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					                                                   ARIANE
       ____________________________________________________________________________________________




                                 ARIANE

                           USER'S GUIDE




                                                                          STRATEGE Bâtiment A
                                                                          BP 2738
                                                                          F-31312 LABEGE Cedex
                                                                          FRANCE
                                                                          Tel.: + 33 (0)5 62 88 24 30
                                                                          Fax: + 33 (0)5 62 88 24 39
                                                                          E-Mail: info-sup@prosim.net




                                                  Version 5.2
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                                                    ARIANE
       ____________________________________________________________________________________________




                                                 CONTENTS




          CHAPTER 1 : General Information



          CHAPTER 2 : Working with ARIANETM



          CHAPTER 3 : Networks



          CHAPTER 4 : Unit Operations



          CHAPTER 5 : Fitting Methods to set unit operations yield curve



          CHAPTER 6 : Utilities



          CHAPTER 7 : Fuel Networks




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                           CHAPTER 1: GENERAL INFORMATION

                                                                 CONTENTS

     1. Introduction......................................................................................................................................1
     2. Applications .....................................................................................................................................2
         2.1. Studies ......................................................................................................................................2
             2.1.1. Power plants design studies..............................................................................................2
             2.1.2. Existing power plants revamping studies .........................................................................2
         2.2. Operation ..................................................................................................................................2
             2.2.1. " Day to day " exploitation ...............................................................................................2
             2.2.2. " Online " exploitation......................................................................................................3
     3. General characteristics .....................................................................................................................4
         3.1. Standard library of unit operations...........................................................................................4
         3.2. Software monetary unit ............................................................................................................4
         3.3. Power plant production description..........................................................................................4
         3.4. Various calculation modes according to the needs ..................................................................5
     4. Install/Uninstall................................................................................................................................6
         4.1. System requirements ................................................................................................................6
     5. Contact us.........................................................................................................................................7




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     The main chapters of this ARIANE software User's Guide are following:
           First chapter is dedicated to a general presentation of the software and its main
           functionalities;
           Second chapter, called "ARIANE implementation", provides an assistance when
           beginning with the software, for all suggested calculation modes;
           Third chapter presents steam and hot water networks;
           The unit operations library available in ARIANE is detailed in the fourth chapter of this
           guide, whereas the fifth chapter is dedicated to the description of methods which can be
           usefull to fit some unit operations parameters;
           Chapter six details and clarifies utilities handled in the software;
           Lastly, seventh chapter is dedicated to fuel networks description.


     1. Introduction

     ARIANE™ software has initially been conceived by Elf Aquitaine company and for them
     developed by ProSim company for design assistance and optimal exploitation of power plants.

     ARIANE™ makes it possible to optimize and simulate any energy combined production plant
     (steam, hot water, electricity, compressed air, cooling), whatever its size and complexity.

     This software aims to minimize the energy invoice, by searching the optimal production
     configuration, taking into account various demand (in steam or hot water influencing the power
     plant electricity production, within the framework of a cogeneration contract or not) and the main
     production constraints.




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     2. Applications

     ARIANE™ has been conceived to allow multiple applications, as well in engineering studies
     (design, investment or revamping studies) as in operation (online direct use).


        2.1. Studies

     ARIANE™ is used for the complete design of any power plant or for any investment study
     (implementation of a cogeneration system for example) on an existing utility system. Calculations
     integrating maintenance and investment costs authorize accurate and realistic design engineering.


          2.1.1. Power plants design studies

     ARIANE™ is a fast and convivial tool making it possible to conceive and/or create all kinds of
     power plants configurations. The operating constraints being imposed, the various imagined
     configurations are compared economically after a reliable and accurate calculation. Comparison of
     several configurations when facing price changes or unavailability of some equipErreur ! Aucune
     entrée d'index n'a été trouvée.ment is also possible by using the software.


          2.1.2. Existing power plants revamping studies

     Thanks to ARIANE™, an existing power plant can be very quickly modelled and evaluated. Then,
     it is really easy to study an investment impact and to evaluate accurately awaited profits. As an
     example, the implementation of a cogeneration system can be evaluated, as well from a technical
     point of view (electric contract level, produced steam...) as for an economic approach (optimum
     profit research after installation of the best adapted cogeneration system).


        2.2. Operation

     In operation, the problem is different since we have to answer the following question : what is the
     optimal operating configuration to generate the required production, while respecting real time
     production constraints as well as increasing environmental constraints?


          2.2.1. " Day to day " exploitation

     ARIANE™ is the exploitation manager daily tool to obtain the best configuration according to each
     steam network or hot water demand, taking into account units operation availability and raw
     material (fuel especially) price changes. In the daytime, using ARIANE™ software allows to
     quickly react when meeting an installation problem (shutdown of a given unit operation, for
     example) by proposing the most suitable alternative, thus offering simultaneously to the owner a
     saving of time and money.




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          2.2.2. " Online " exploitation

     If the power plant is automated, the coupling of ARIANE™ software with a numerical control
     command system (SNCC) can be done to lead to a power plant real time optimization tool. It only
     requires a few specific developments such as a communication protocol between real time database
     and ARIANE™ software or a specific power plant synoptic. These developments are carried out by
     ProSim, to finally provide an easy to use power plant management tool.




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     3. General characteristics

     From a general point of view, ARIANE™ software main characteristics can be described as
     follows:
         User-friendliness: so that the software is accessible to most people, its use is supposed to be
         instinctive and, a priori, no preliminary training is required. The graphical interface has been
         developed to present clear menus, so that the power plant description is flexible and interactive.
         Flexibility: any power plant can be simulated/optimized, from the simplest to the most
         sophisticated, from a scale point of view (unlimited networks and unit operations number) but
         also from models point of view (solving method adapts to the modeling complexity (see chapter
         2)), while minimizing the computation time. The software allows “coarse but extremely fast”
         calculations (quasi linear calculations), but also much more complex, accurate and realistic
         calculations (nonlinear optimization).
         Robustness and reliability: whatever the calculation mode.


        3.1. Standard library of unit operations

     ARIANE™ presents a standard library of unit operations usually met in power plants: boilers
     (mono-fuel, bi-fuel, electric), turboalternators (backpressure turbines, sidestream turbines,
     condensating turbines), switchable or permutable turbines (in parallel with electric motors), fuel
     turbines and thermal engines (with or without recovery heat exchanger, with or without post-
     combustion boiler), valves (with or without desuperheating), heat exchangers and deaerators.

     All these unit operations can be described easily, from the simplest modeling (minimalist modeling,
     with default values) to the most complex (very fine modeling of the characteristics and technical
     constraints, the complexity of physical models requiring in many cases to use nonlinear models). Of
     course, the lesser or greater complexity of the models, and thus of generated equations, is totally
     transparent for the user.


        3.2. Software monetary unit

     For economic calculations, the default monetary unit handled by the software is the euro (€). Cost
     data are thus provided in euros (utilities price level and unit operations costs). Nevertheless,
     calculations remain valid whatever the selected monetary unit (if costs are defined in dollars ($),
     results are also consistent when expressed in this monetary unit ($)).


        3.3. Power plant production description

     ARIANE™ has been designed with a user-friendliness preoccupation; the power plant definition
     (see chapter 2) is thus carried out easily when following the four steps described hereafter:
            Utilities and units related to the power plant description ;
            Networks description ;
            Unit operations description ;
            Required production and global production constraints definition.

     Once this information completely informed, user can run different types of calculations.
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        3.4. Various calculation modes according to the needs

     To cover all his needs, ARIANE™ proposes two calculation modes to the user, a “simulation”
     mode and an "Optimization" mode ("classical" optimization, optimization with a stopping heuristic
     method, optimization sequencing (wide range calculations)). Optimization algorithm deals with
     realistic models (nonlinear models) with a non linear programming (in continuous variables)
     method (SQP), wich is known as a robust and reliable mathematical tool. Chapter 2 presents in
     details the various calculation modes and used mathematical tool. Main calculations uses are
     synthesized hereafter:
                  Simulation,
                  Simulation with mean costs calculation,
                  Optimization,
                  Optimization with mean costs calculation.

     The criterion (objective function) at least includes the exploitation cost of the plant. It is also
     possible to take into account maintenance and investment costs in this criterion.

     The optimization initialization is a really important procedure to ensure calculations robustness. A
     very strong effort has thus been brought to the variables initialization procedure:
                  Fully automatic initialization,
                  User initialization,
                  Mixing of the two preceding methods,
                  Initialization from results of a previous calculation (simulation or optimization).

     Other possible calculations:
                 Produced utilities marginal costs calculations,
                 Mean costs calculation using an incremental method,
                 Optimization with a stopping heuristic method,
                 Optimization sequencing (wide range calculations).




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     4. Install/Uninstall

     A guide delivered with ARIANE™ CD-Rom contains all the useful information to install and to
     start ARIANE™. This guide also contains the list of minimum required hardware, local station or
     network installation procedures, details about licenses management, help to solve possible problems
     as well as procedure to start and stop the program.


        4.1. System requirements

     ARIANE™ has been designed for 16 and 32 bits systems using Windows 3.x, Windows 95,
     Windows 98, Windows NT 3.51, Windows NT 4 and Windows 2000, XP (or higher).

          Processor Pentium 133 or higher.
          16 Mb of RAM or more (64 Mo or more recommended).
          Operating system Microsoft Windows 3.x, 95, 98, NT3.51, NT 4, NT 2000, XP (or higher).
          10 Mb available disk space (for the complete installation of the software).
          2 Mb of additional open disk space (for installation process temporary files)
          At least 64 Mb available disk space after installation for optimal performances of use.
          A disk drive 3½. and a CD-Rom reader.

     The above description corresponds to a minimum required, a more recent hardware, in particular
     from processor point of view, leads to a better comfort of use and also decreases calculation time.




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     5. Contact us


                        Address:               ProSim S.A.
                                               Stratège Bâtiment A
                                               BP 2738
                                               F-31312 LABEGE Cedex
                                               FRANCE

                        Phone:                 +33 (0)5 62 88 24 30

                        Fax :                  +33 (0)5 62 88 24 39

                        WebSite:               http://www.prosim.net

                        Email :                support@prosim.net




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                               CHAPTER 2: Working with ARIANE™

                                                                 CONTENTS
     1. First steps with ARIANE™ software ..............................................................................................1
         1.1. "File" menu...............................................................................................................................2
         1.2. "Options" menu ........................................................................................................................3
             1.2.1. "Options" menu, "Preferences" submenu .........................................................................3
             1.2.2. "Options" menu, "Labels" submenu .................................................................................5
         1.3. "Help" menu .............................................................................................................................5
         1.4. Particular graphical option .......................................................................................................6
         1.5. Print ..........................................................................................................................................6
         1.6. Excel export..............................................................................................................................6
     2. Building a power plant.....................................................................................................................8
         2.1. Steam or hot water networks building......................................................................................8
         2.2. Fuel networks building.............................................................................................................9
         2.3. Add unit operations ..................................................................................................................9
         2.4. Global constraints visualization .............................................................................................10
     3. Simulation mode calculations ........................................................................................................11
         3.1. Simulation runs ......................................................................................................................12
         3.2. Simulation provided results....................................................................................................13
         3.3. Simulation convergence .........................................................................................................15
     4. Optimization mode calculation ......................................................................................................18
         4.1. Optimization problem definition ............................................................................................18
             4.1.1. Criterion..........................................................................................................................18
             4.1.2. Constraints ......................................................................................................................19
             4.1.3. Action variables ..............................................................................................................20
         4.2. Solving method ......................................................................................................................20
             4.2.1. Numerical problem initialization....................................................................................20
         4.3. Optimization run ....................................................................................................................23
         4.4. Optimization results ...............................................................................................................24
         4.5. From simulation to optimization ............................................................................................25
     5. Mean costs calculation ...................................................................................................................27
         5.1. General presentation...............................................................................................................27
         5.2. Mean cost calculated during main problem solving...............................................................27
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         5.3. Mean costs calculated by an incremental method ..................................................................29
         5.4. Results ....................................................................................................................................29
             5.4.1. Labels..............................................................................................................................29
             5.4.2. Results for each unit operation .......................................................................................30
             5.4.3. General results ................................................................................................................31
     6. Marginal costs calculation .............................................................................................................34
     7. Optimization with stop...................................................................................................................36
         7.1. Generalities.............................................................................................................................36
         7.2. Heuristic description ..............................................................................................................36
         7.3. "Optimization with stop" execution .......................................................................................38
     8. Multi-periods optimization ............................................................................................................41




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        1. First steps with ARIANE™ software

        When opening ARIANE™ the following window appears :




        In this part devoted to the first steps with ARIANE™ software, only first functionalities to
        manage the files, parameterize and personalize the software will be approached. Menus and
        short cuts dedicated to software specific use will be detailed in the following chapters of this
        user's guide. As a consequence, the "Unit operations" bar, the "Network", "Unit
        operations", "Utilities", "Calculations", "Constraints" and "Balances" menus, as well as the
        "Simulate", "Optimize", "Data", "Opt. res." (optimization results), "Sim. res." (simulation
        results) and "List" short cuts will not be described in this chapter.

        A password makes it possible to secure the software use:




        This password can be modified (see paragraph 1.2).

        After the password input, the software configuration is as follows:




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        It should be noted that scroll bars (vertical and horizontal) allows to quickly locate unit
        operations on the defined flowsheet, in the case of large scale power plant.

        Under the "Menu" bar (at the top of the window), a toolbar gives a quick access to some
        functionalities, such as, in the previous picture, the "Unit operations" bar, located vertically
        on the right part of the window.


          1.1. "File" menu

        This menu relates to the files management (ARIANE™ files are finished by a “.war”
        extension). This heading classically aims to create, save, modify or print the files used in the
        software. Toolbars propose short cuts towards some functionalities ("New" to create a new
        file, "Open", "Save" and "Print" to handle existing files).




        Note : an "Other versions of this file" option, available in the "File" menu allows to recall
        former versions of the current file, as presented hereafter.




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           1.2. "Options" menu

        This menu is dedicated to the software personalization, either by the using the "Preferences"
        or "Labels" submenus.


              1.2.1. "Options" menu, "Preferences" submenu




        - the "Files" tab enables:

               • to select the number of last opened files to be kept in the "File" menu (between 1
                 and 10).




               • to change the password (by clicking on the dedicated button):




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        - the "Models" tab is used to save some unit operations default parameters data, which are
        saved in a file “file_name.mod”, under a specific format.




        - The "Flowsheet" tab is used to personalize the software. It makes it possible to choose unit
        operations graphic type, to show or mask a background grid, and also to personalize the
        colors:




           -   The "Toolbar" allows to show or to mask unit operations vertical bar.




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        - Finally, the "International" tab aims to select the software language (French or English) as
        well as the decimal separator (. or ,).




              1.2.2. "Options" menu, "Labels" submenu




                                                            or

        The "Labels" submenu relates to the visible labels around each unit operation on the
        flowsheet drawing. It is thus possible to display more or less information labels around each
        unit operation. The following examples relate to an electric boiler around with different levels
        of information posted directly on the flowsheet:




         No label                          All the labels                  Only one label: the flowrate.



           1.3. "Help" menu

        This menu gives access to ARIANE™ support. In the "About Ariane" tab of this menu, it is
        possible to send an email to the software technical support (if at an electronic mail application
        is available on the current machine). To reach assistance, it is also possible to use the

        following short cut        or F1 key.




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          1.4. Particular graphical option




        Using the above short cut, it is possible to increase (+) or to decrease (-) the flowsheet draw
        width. If the flowsheet width becomes higher than the screen width, a scroll bar appears at the
        bottom, for entire drawing visualization. In the same way, if the specified number of networks
        becomes too large to be displayed on the height of the screen, a vertical scroll bar appears.


          1.5. Print

        The "Print" option, in the "File" menu allows to publish the results in a paper form or in a
        HTML file form.

        Edited headings are:
               Process flowsheet,
               Process data,
               Simulation and/or optimization results (depending on the previous calculation
               mode(s)),
               Financial balance.




          1.6. Excel export

        This function, is an Excel export of all the process variables (supplied parameters and
        calculation results). Variables are then summarized in an MS-Excel form file.

        This option is accessible from the "File" menu, under the "Export for Excel…" heading, as
        shown hereafter:




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        During export run, the following windows appear:




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        2. Building a power plant


        When building a power plant with ARIANE™, some rules have to be respected in order to
        guarantee the data set consistency. It is advised to follow the progression presented hereafter
        to prepare the flowsheet of the plant to be simulated (or optimized).

        Before describing the plant unit operations and networks, all manufacturing units associated
        to the power plant, and then utilities shared on the site should be described.

        Using the "Electric demand" heading of the "Constraints" menu allows to access to the list
        of units (maximum twenty) that can be configured (by possibility naming, starting and
        affecting an electric consumption to them).

        The utilities description includes demineralized water, fuels and network electric call (see
        utilities description in the dedicated chapter).

        Drawing the process
        The drawing aims to be easy and intuitive, in particular thanks to the vertical bar menu, on the
        right part of the screen. This unit operations bar contains networks (steam, hot water and fuel)
        and all the available unit operations. The various elements become active progressively, along
        the power plant building evolution.




                                              " Equipment and Networks " bar


        When opening a new file, only " Networks " shortcut (        and       ) are accessible.

        Apart from this equipment bar, it is possible to add networks (or unit operations) by using the
        "Network" menu (or "Unit operations" menu), and then the "Add…" heading. This method
        is less convivial to add elements but the other heading of this menu ("List…") proves to be
        very useful to modify existing configurations. This heading gives access to a window that
        displays the complete list of networks and unit operations. Then "double clicking" on the
        element of interest enables to access its properties. In the case of large scale power plant,
        including many networks and many unit operations, this method is often easier than to seek
        on the graphical flowsheet the object corresponding to the unit operation to be modified.


          2.1. Steam or hot water networks building

        All networks should be defined (steam and hot water) before starting unit operations
        description. For a detailed description of the networks, refer to chapter number 3.




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        When first network is validated, some unit operations become active in the dedicated bar.
        After the validation of second network, simple valve and most turbines become also
        accessible. It is only after the third network validation that the side stream turbine become
        active. Concerning boilers, de-superheated unit operations and heat exchangers, they become
        accessible when at least one deaerator was defined and validated.


           2.2. Fuel networks building

        Fuel networks are presented in detail in chapter 7. To create such a structure, it is necessary to
        integrate the two strong following constraints:
                Networks are positioned on the drawing according to their order of creation, the first
                created network being at the top, the last one being at the bottom,
                Fuel valve have an imposed direction flow from "Higher" to "Lower" network.


        Networks that are feeding some other networks with their surpluses have to be defined before
        the ones that are receiving these surpluses. This is a limit of the fuel networks concept as this
        structure is not able to manage direction flow changing according to current conditions.

        After fuel networks definition, it is possible to create "fuel feeds" and "fuel valves" (these unit
        operations are defined hereafter).

        At this stage, the fuel structure is an autonomous process, completely independent from the
        rest of the plant (steam and hot water networks, electricity producing…).
        Links between fuel networks and main structure take place when creating and defining unit
        operations that are fed by fuel networks (boilers, fuel turbines, thermal engines…). Fuel
        networks are displayed in the fuel list, in these unit operations "Conception" menus, as
        "classical" fuels (those defined in the utilities framework).


           2.3. Add unit operations

        After definition of all the networks, deaerators have to be defined (for a detailed description
        of this unit operation, please refer to chapter 4). It is then possible to define boilers, and then,
        unit operations that realize steam transfer between networks (turbines and valves). These unit
        operations are also detailed in chapter 4.

        A fuel turbine (and/or a thermal engine) can be defined after the first network validation.
        These unit operations, known as "cogeneration units" (thermal engine, fuel turbine and
        possibly post-combustion boiler) are also detailed in chapter 4. Recovery heat exchangers
        (placed behind the fuel turbine, the thermal engine or the post-combustion boiler) become
        accessible in the unit operations bar, only when the turbine or the engine is completely
        validated in the power plant flowsheet.

        Lastly, exchangers called "simple heat exchangers" (see chapter 4) are preferably the last
        described, as their definition should not generate particular problem.




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          2.4. Global constraints visualization

        At this stage, the power plant is almost completely described. "Constraints" tab, in the
        "General table" heading, allows to visualize all the defined global constraints: fuel,
        demineralized water or electricity supplying constraints (defined in the utilities framework)
        and/or electricity resale constraint (defined, if it exists, when defining the cogeneration
        contract). An additional global constraint can also be defined in this general table, concerning
        the sulfur maximum emission, in kg per hour of power plant exploitation. All the defined
        constraints can be modified directly from this window. Associated to each of these
        constraints, assigned weighting parameters are also visible (reading only; to modify them, go
        back to concerned utility description window).




                                      Summary of all global constraints

        Once the power plant perfectly described, it remains to make sure that each defined
        equipment item operating mode is consistent with the selected calculation mode.




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        3. Simulation mode calculations

        Simulation implies an almost complete determinism at the level of unit operations. For each
        network of the plant, input flowrates must perfectly be determined, and also N - 1 of the N
        network output streams, the Nth being simply deduced by network material balance (this Nth
        stream is called the autonomy degree of each network, in simulation mode).

        This principle imposes that all the boilers operate in "manual" mode (Bi-fuels boilers having
        in addition a fixed fuel ratio). For the same reasons, transfer unit operations (valves, turbines)
        must respect one of the two following configurations:
               All steam transfer unit operations (valves, turbines) connected as an output (network is
                thus their admission network) of a network are in manual mode (fixed output flow rate
                or fixed produced power) if this network has an opened waste stream pipe (in
                automatic mode). The waste stream pipe is then the network autonomy degree;
               Only one of the steam transfer unit operations (valves, turbines) connected as an
                output (network is thus their admission network) of a network is in automatic mode
                (with or without user initialization) if this network has a closed waste stream pipe (in
                stopped mode). This unit operation is thus the network autonomy degree;




                     When "simple" heat exchangers, deaerators and network output valve (de-
                     superheating valves to regulate the network steam output temperature) are in
                     automatic mode, they have to be considered as in "manual" mode, because their
         Caution
                     specific constraints completely determine their operating point (no freedom degree).
                     Side stream turbines must also have a fixed side stream ratio (or flowrate).



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        Cogeneration unit operations necessarily operate according to one of the two schemes
        presented hereafter:
               Fuel turbine (or the thermal engine) is necessarily in manual mode (fuel flowrate or
               produced power are fixed);
                       and
               Post combustion boiler is in manual mode if all following recovery heat exchangers
               are in automatic mode;
                         or
               Post combustion boiler is in automatic mode if one (and only one in simulation mode)
               following recovery heat exchangers is in a manual mode (fixed output flowrate).

        In other words, fuel consumption of cogeneration unit operations is perfectly determined, as
        well as all output flowrates (which are input flowrate for connected networks), at the level of
        each heat exchanger.

        Calculation can only be started if all these conditions are satisfied. Messages that aim to be
        explicit have been set up to help the user to reach a suitable configuration according to the
        calculation mode. A typical example of returned message when user has defined a non
        suitable configuration is presented hereafter.




             Example of error messages displayed when power plant configuration is not suitable


          3.1. Simulation runs


        To execute a simulation run, directly click on the    icon or use the "Calculations" menu,
        "Start" heading, "Simulation" subheading, or use key F9 dedicated short cut.




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          3.2. Simulation provided results

        If convergence has been reached, the provided results are numerous:

               Total operating cost of the power plant is the major result, with a detailed financial
               balance. To access to these results, use the "Balances" menu, "financial" heading. A
               window, as presented hereafter, allows to visualize the power plant various costs, the
               possible profit associated to the cogeneration activity and even the total sulfur
               emission.




                                        Power plant financial balance

        On the preceding figure also appears a financial balance concerning:


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               Maintenance total cost;
               Investment total cost (expressed as a hourly cost).

        Total cost in "criterion" line represents total exploitation cost, plus possibly maintenance cost
        and investment cost. The criterion choice is made in the "Calculations" menu, "Parameters"
        heading, "Costs" subheading.

               the simulation mode also provides an electric power balance, which presents on the
               same draw the network electric power call (sum of units demand and power plant self
               consumption) and also the self-produced electricity (in cogeneration or not). To reach
               this balance, use the "Balances" menu, "Electricity" heading.




                              Electric balance of the power plant after simulation

               each network and each unit operation presents its specific results, either by the mean
               of labels, or by the mean of the "Simulation" tab that can be easily reached by double
               clicking on the desired object (for more details on all unit operations calculation
               results, refer to chapter 4).




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                                 Simulation results visualized using labels

          3.3. Simulation convergence

        The simulation carried out is a sequential modular simulation. Each network, each unit
        operation is then a simulation module and global simulation consists in a sequential
        calculation of these modules. Taking into account the main principles of simulation
        calculation mode, it is advised to specify some elements:

              non convergence of simulation indicates that the considered operating point (for the
              power plant) is technically impossible. Various causes of failure are possible, like an
              insufficient steam production, an impossible mass or energy balance on a given unit
              operation...

          The windows hereafter display the results obtained in the event of simulation non
          convergence.




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          The returned "warnings" and "errors" are helpful to analyze the failure cause. In the
          previous window, for example, the demineralized water temperature is incompatible with
          the required deaerated water temperature.

               Caution : calculations convergence, in simulation mode, does not guarantee the
               feasibility of the power plant operating point. Taking into account the simulation
               principle, some constraints are not taken into account during the calculation (they are
               evaluated but they cannot be integrated into the solved problem). For example, global
               constraints (fuels supply, for example) are not integrated into the problem to be
               solved. It is the same for sulfur emission constraint, with mini/maxi network
               temperature constraints and even for technical constraints of the unit operation that has
               been selected as network autonomy degree.

        Nevertheless, the constraints that have not been integrated into the simulation solved problem
        are evaluated and some warnings appear (after simulation run) if some of them are just
        satisfied (technical bound reached) or even exceeded. As an example, the window below
        presents an example of back calculation warning. Simulation convergence has been reached
        but the following window appears at the end of the simulation run:




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        If the first warning only states that one of the turbines has reached its technical maximum, the
        other indicates that the sulfur emission constraint is not satisfied. Legitimately, it can be
        considered that proposed operating point is "impossible".

                    A simulation is "possible" (i.e. the simulated operating point is technically possible,
                    considering all the defined constraints) if -and only if- calculation convergence has
                    been obtained, and if the "warning-error" final heading does not present information
         Caution
                    relating to non respect of a defined constraint.




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        4. Optimization mode calculation

           4.1. Optimization problem definition

        Optimization consists in looking for the economic optimum of a given plant, with a given
        configuration, with an imposed energy load, while respecting all defined constraints.
        Taking into account the nonlinear character of some used models, optimization naturally leads
        to a non linear programming method, in continuous variables (NLP, see paragraph 3.2 of the
        current chapter).


                4.1.1. Criterion

        The used criterion is at least the power plant operating cost, that SQP method will try to
        minimize. This criterion is composed of multiple elements:

                 Demineralized water (consumed in each deaerator) total cost. This water is consumed
                 to generate the deaerated water, which is the feed of the various boilers but also of the
                 desuperheated unit operations. Minimize demineralized water consumption is one of
                 the optimization problem aspects;
                 Fuels cost (fired in boilers, fuel turbines or thermal engines). Depending on unit
                 operations load, fuels total consumption (and thus fuels cost) fluctuates, and fuels
                 consumption minimization is also an optimization problem aspect;
                 Electric power cost. The final network electric power call is the sum of units electric
                 power consumptions, plus boilers consumptions, less self-produced electricity (by
                 turbine action). Electric power total cost minimization consists in minimizing the
                 boilers consumption while maximizing the self produced electricity. If present, the
                 cogeneration profit has also to be taken into account.
                 Finally maintenance and investment hourly costs can or not (the choice is left to the
                 user), be integrated into the objective function.

        Finally, total cost is expressed as follows : :

                                   Fobj = C ed + C elec + C comb − Gcoge + (C ma int + C inv )
        with:
                Fobj               objective function to be minimized (total cost in euros per hour)
                Ced                demineralized water cost
                Celec              network electric power call cost
                Ccomb              fuels total cost
                Gcoge              profit due to cogeneration contract
                C ma int           maintenance total cost
                C inv              investment hourly total cost

        It should be noted that these six terms are not independent.

        As indicated in the simulation descriptive paragraphs, the criterion is selected by the user,
        among one of the three following possibilities:

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                 Operating cost;
                 Operating plus maintenance cost;
                 Operating plus maintenance plus investment cost.

        It is simple to understand that investment and maintenance costs consideration will only be
        efficient if various contributing costs are described accurately, for each concerned unit
        operation (see "Inv/Maint" heading of unit operations).


                4.1.2. Constraints


                  4.1.2.1. Local constraints

        "Local constraints" are specific to a given object (unit operation or network), i.e. a constraint
        that the module is able to evaluate itself. These constraints can be equality or inequality
        constraints. As an example, a turbine in manual mode, at "user fixed power", generates the
        following local equality constraint:

                                                        Pimp − Pprod = 0
        with:
                Pimp    fixed power (user request);
                Pprod   produced power, function of steam flowrate and turbine technical features.

        In addition, for a valve in automatic mode, two local inequalities constraints are also
        generated:
                                             Qmin − Q < 0

                                                 Q − Qmax < 0
        with:
                Q       valve flowrate
                Qmin    minimum valve flowrate (user definition)
                Qmax    maximum valve flowrate (user definition)


                  4.1.2.2. Global constraints

        Global constraints require a summation in a dedicated module. Some constraints such as fuels
        total consumption or sulfur total emission generate inequality constraints but some equality
        constraints also exists. For example, if a cogeneration contract is defined, the total produced
        power (sum of all concerned unit operations) has to be equal to the contractual power.

        Power plant operating optimization, even for small size plants, generates a great number of
        constraints that have to be managed by the optimization tool.




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                 4.1.2.3. Constraints weighting

        As described in the unit operations chapter, main constraints (local or global) can be
        weighted, using a dedicated parameter. The constraint "consideration" can thus be increased
        or decreased, according to a specific need.

        This possibility is very interesting when a file presents some convergence difficulties, due to a
        specific constraint, which largely exceeds one of its defined bounds (minimum or maximum)
        at a given moment (often at the beginning of the optimization run). Weighting this constraint
        can eliminate the calculation problem, during optimization run.


              4.1.3. Action variables

        First, it should be noted that "actions" are possible only for unit operations in "automatic"
        operating mode (with or without user initialization). In other operating modes, their operating
        point is fixed, i.e. optimizer cannot adjust it. Action variables are divided into three concepts:
                 Fuel flowrates action variables,
                 Any boiler (mono or bi fuel boilers, post-combustion boiler), fuel turbine, or thermal
                 engine, in automatic operating mode, is the optimizer target, through an action on the
                 fuel flowrate,
                 Action variables on the flowrate distribution at the network splitter level; each transfer
                 unit operation in automatic mode is an optimizer target, through an action on the unit
                 operation admission flowrate,
                 Action variables on "free ratios". When the ratio is free (fuels flowrate distribution for
                 bi-fuel boilers or flowrate distribution between side and exhaust for side stream
                 turbine), it is also an action variable of the optimizer.

        All in all, the described problem consists in minimizing the objective function, by respecting
        all defined constraints (equality and inequality, local or global), by adjusting the previous
        defined action variables.


           4.2. Solving method

        The optimizer tool used in ARIANE™ was initially developed at the Carnegie-Mellon
        University of Pittsburgh, in United States (Biegler, Cuthrell, 1984). This tool is based on a
        non linear programming method (NLP), more precisely a successive quadratic programming
        (SQP) routine. This robust and powerful tool underwent some modifications to be perfectly
        integrated in the software and to provide reasonable calculation times (see numerical problem
        initialization and optimizer parameters).


              4.2.1. Numerical problem initialization

        Optimizer efficiency, especially from a computing time point of view, is very sensitive to the
        variables initial values (like any optimization mathematical method). For this reason, a great
        care has been brought to the development of a specific initialization method, dedicated to
        ARIANE™ software.


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                 4.2.1.1. Automatic initialization

        This method is coupled with the optimizer, to provide it with a realistic initial point. It solves
        a general mass balance, taking into account main economic costs (boilers) and profits
        (turbines). It also manages cogeneration units initialization, integrating concepts like partial or
        total cogeneration contract. On the other hand, it has to be noted that some global constraints,
        like supplying constraints, or global sulfur emission, for example, are not taken into account.
        During this phase, the existence of at least one "feasible point", from a mass balance point of
        view, is checked for each defined unit operation, as well as input data consistency (user
        defined technical bounds consistency, for example).


                 4.2.1.2. " User "Initialization

        Automatic mode with "user initialization" option (flowrate or produced power) allows to
        affect initial values to selected unit operations. This possibility is extremely interesting as it
        allows the user to:
                modify the initial point if the automatic initialization procedure fails;
                totally set the initial point, if desired.


                 4.2.1.3. Initialization by the results of a previous calculation

        It is possible to start an optimization run using the results of a preceding run, at convergence
        point ("Calculations", "Start", "Restart optimization"), provided that the problem structure
        remains unchanged. Authorized modifications (that give access to "Restart optimization") are
        the following:
                Global switch of all unit operations in automatic mode via the dedicated "Auto."
                button (when the initial file is a simulation calculation),
                Global constraints modifications,
                Modifications concerning utilities data (electricity, demineralized water, fuels),
                Required production (network steam flowrate…)
                Modifications on fuel networks (network, feeds, fuel valves).

        All these initialization methods finally provide to users an interesting and useful adaptability




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                                       "Calculation parameters" window

        The "traditional" optimization parameters are as follows:
               Optimizer maximum iterations number;
               Gradient order (1 or 2). If the selected order worth 1, the gradient is evaluated with the
               following formulation : g(x) = [f(x+ dx)- f(x)] / dx); otherwise, the following
               formulation is used : g(x) = ([f(x+dx)-f(x-dx)]/(2.dx)) ;
               Optimization classical tolerances are manipulated (Kuhn-Tucker's parameter, to
               characterize the convergence (or not), but also tolerances concerning constraints
               violation, variables evolution or criterion evolution). This tolerances are used
               simultaneously to determine the convergence criterion.

        Tolerances default values are set to 10-6. Nevertheless, they can be modified by user, to obtain
        the best compromise between precision and computational time.

                 4.2.1.4. Initialization of the numerical type of resolution

        For quasi linear problems, significant computing times are often reproached to non linear
        methods (NLP) when compared to simple linear methods (LP). As a response, SQP method of
        ARIANETM offers a specific numerical initialization method for "strongly linear systems",
        which allows a significant calculation time saving (in case of quasi linearity of the solved
        problem).

        This option confers to the optimizer a great adaptability by allowing on the one hand to
        quickly solve quasi linear problems, while remaining able, on the other hand, to solve much
        more complex non linear systems, maintaining all its precision, i.e. without resorting to more
        or less suitable physical models linearizations.




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                 4.2.1.5. Resolution of a restricted problem

        This last option must be considered as a help, when convergence difficulties appear for a
        given system. This option allows to simplify to the maximum the optimization problem to be
        solved, by reducing it almost to a simple mass balance. When this option is selected, the
        optimization problem neglects all the hereafter enumerated constraints:
               Produced power constraints;
               Utilities supplying constraints ;
               Mini/maxi on network temperature;
               Sulfur emission constraints ;
               Waste pipe maximum flowrates;
               Deaerator recycled steam maximum flowrate;
               Various constraints (smokes flowrates, air flowrate...) concerning cogeneration
               equipment item.

        In fact, restricted problem solving consists in minimizing exploitation cost, taking into
        account the technical constraints related to boilers, equality constraints related to unit
        operations in manual mode, flowrate constraints related to unit operations in automatic mode,
        temperature and flowrate constraints related to deaerators, and, of course, required steam or
        hot water flowrates related to networks.

        Main constraints may be weighted by users (technical constraints, utilities global constraints,
        network temperature constraints…); this allows a great flexibility between a "basic"
        optimization run and a totally "restricted" system to be solved.

        Finally, these possibilities, in terms of initialization, numerical problem characterization, or in
        terms of constraints weighting lead to a robust, suitable but also flexible optimization tool,
        able to adapt to any given problem, linear or not, and able to manage any specific cases
        (specific initializations, non typical operating conditions or special constraints).


        Software real power is in fact due to robustness, suitability and flexibility of its optimization
        tool.


           4.3. Optimization run


        To start an optimization run, use the following button          or select the "Calculations"
        menu, "Start" heading, "Optimization" subheading.




        It is also possible to use dedicated Ctrl+F9 short cut.


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           4.4. Optimization results

        Optimization results are displayed in the same way as simulation results (see paragraph 2.2 of
        this chapter). The only difference is that obtaining convergence, in optimization, means that
        the economic minimum has been reached and all constraints have been respected.

        Supplied results relate to the criterion (operating cost), financial balance, electrical balance
        and results specific to each unit operation and each network, through labels or at the level of
        the "optimization" results tab. The diagrams hereafter display the optimization results
        obtained for a simple power plant example.




        Here, iteration count is equal to 3, for a criterion of Kuhn-Tucker of about 10-5. The
        constraints are completely respected. The minimum operating cost is roughly 4710 euros per
        hour (for more precisions and details on the distribution of these costs, consult the "Balances"
        menu, "financial" heading).




                                     Flowsheet diagram after optimization

        Among the results which are likely to be observed at the end of the calculations, the
        "Historic.txt" file is to be noted as it allows to visualize the course of the computing process,
        the modules execution sequence, and the evolution along iterations of influential parameters
        such as the criterion, the parameter of Kuhn-Tucker or the constraints violation parameter.




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        This option is proposed in the "Calculations" menu, "Parameters" heading. The definition
        window then proposes the "Visible history" option, which can be selected as presented
        hereafter.




          4.5. From simulation to optimization

        It is not always easy to switch from simulation to optimization mode, especially when unit
        operations number is significant: operating modes have to be changed unit operation by unit
        operation, and this can lead to a very significant number of handlings. To avoid these boring
        modifications, two possibilities have been implemented:

        Global switch of unit operations : "Auto." button

        All unit operations are switched to automatic mode when acting on the dedicated button,
        available in the menu bar, as presented hereafter:




                                              Switches all the unit operations to automatic mode

        Only the unit operations that were in manual mode are switched to automatic mode, stopped
        or out of order unit operations are not concerned by this option.


        Simplified procedure for modification of unit operations state (switch to automatic mode)


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        This procedure allows to only select the automatic mode for some unit operations. The aim is
        to ease the access to the unit operation state without having to "double-click" on the icon,
        select the "ad-hoc" tab, modify the unit operation state and validate the modification. To use
        this procedure, the unit operations summary table (accessible via the "list" shortcut or via the
        "unit operations" menu, under the "lists" heading) allows to change a unit operation state
        (from manual mode to automatic mode) directly in the summary list. It is possible to switch to
        the automatic mode by double clicking on the current unit operation state.

        Note: if the "Auto." button is used to modify the unit operations state, a simulation file can be
        used as initial point of the new generated optimization file (restart optimization, see paragraph
        4.2.1.3.).




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        5. Mean costs calculation


          5.1. General presentation

        Mean cost calculation of produced utilities consists in distributing the power plant total
        exploitation cost between the various produced utilities (steam, hot water, electricity,
        compressed air, cold) and the losses (not recycled purges, waste pipes...).

        This calculation is really important to carry out an economic balance and evaluate the quality
        of the power plant operation.


          5.2. Mean cost calculated during main problem solving

        Mean costs are automatically calculated during an optimization run (although not always
        shown) but it requires a specific user demand to obtain them in simulation mode. Mean costs
        calculation is specified in the "Calculation" menu, "calculation parameters" heading, "Costs"
        subheading, as shown hereafter.




        A check box allows to select the mean costs calculation during simulation run (by default, the
        box is ticked).

        Then, the user has to select a repartition mode. Let us consider a turbine for example, which
        generates both steam and electricity as outputs, and let us considerer a cost for the input



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        steam; repartition mode allows simply to distribute this input cost between the two generated
        outputs.

        The "Percentage" mode consists in affecting a percentage of the entering cost to electricity
        production, the balance being affected to output steam.

        The " Avoided cost" mode consists in considering that produced electricity represents a cost
        equal to its purchase price (defined in the utilities framework) multiplied by the produced
        quantity (produced by the unit operation). In other words, the turbine avoids a network
        electric call equivalent to the price previously calculated. Thus, from input cost is cut off the
        avoided cost, to deduce the output stream cost. In this case, it is possible to observe negative
        costs for turbine exhaust streams.

        Lastly, the "energy distribution" mode consists in affecting the input price according to
        energetic considerations. As a consequence, in the case of a turbine, exhaust steam potential
        energy is compared to a reference state (steam enthalpy at network lowest pressure, and at
        corresponding saturation temperature). Let He be the input steam energy level, Hs be the
        exhaust steam energy level and Href, be the previously defined reference energy. The ratio R
        is defined as shown hereafter :
        R = [ (He – Hs) / (He – Href) ]
        R represents in fact a "steam energy extraction", i.e. the ratio between "extracted energy" and
        "maximum extractable energy". This method is based on the concept that steam has no more
        value when its entire energy has been extracted. Consequently, the cost affected to electricity
        production is equal to R multiplied by the steam entering cost, the output steam cost being
        simply deduced by subtraction. Three reference energy levels have been defined in the
        software:

        Steam reference energy (lowest energy level; it is implicit that no additional electric power
        production can be obtained from this steam): steam enthalpy of the lowest pressure network.

        Smokes reference energy (smokes energy level; it is considered that no more thermal
        exchange can be carried out with these smokes): a reference level equal to smokes enthalpy,
        at 100°C and under atmospheric pressure is admitted.

        Water reference energy (for condensing unit operations calculation): the reference energy
        level equal to demineralized water enthalpy, at the lowest temperature observed on the entire
        power plant is admitted.

        Methodology

        The implemented methodology is based on a simple concept : produced steam or hot water
        have an initial producing cost (fuel, water..) and this initial cost decreases if they generate
        "profits" (electrical profit in fact) in some unit operations. This method leads to reliable
        calculations of produced utilities mean costs. The basic idea consists in associating a price to
        each process stream, including losses streams.

        As a consequence, if each process stream cost can be calculated, a simple summation allows
        to calculate the "network cost" (mixing of all network input streams). The produced utility


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        cost is simply a fraction of the network cost (previous fraction is simply the ratio between
        produced utility flowrate and network total input flowrate). Each unit operation of the process
        is considered in an autonomous way: it "buys" its entries (vapor, deaerated water, raw
        materials...) and it thus produces a main stream which cost can easily be evaluated. Only few
        particular unit operations are more complex and require a more precise attention (recourse to
        a cost distribution between the several produced utilities). Most unit operations do not cause
        evaluation problem: knowing input cost, it is possible to calculate the produced stream output
        cost.

        Calculation is thus carried out from the highest pressure network towards the lowest. For each
        network, the produced utility is calculated. Co-generated electricity and others special
        produced utilities (compressed air, cold) are also calculated during the main calculation
        progression.


           5.3. Mean costs calculated by an incremental method

        This mean costs calculation method requires:
              A first run to provide a reference,
              A second run to evaluate produced electricity mean cost,
              A third one to calculate others mean costs (steam,…).

        The first calculation is called "reference run". The criterion of interest is the cost "without
        electricity" consideration (i.e. fuels cost plus water cost). This cost is noted: CHE1.
        Produced electricity (P1) is stored.

        A second run is started without electricity producing machines (turbines, fuel turbines…). The
        intrinsic idea consists in appreciating the production cost (without electricity consideration) of
        the required steam production. This second run leads to the second cost, noted CHE2.

        The basic idea of this method consists in affecting the extra cost (CHE2-CHE1) to electricity
        production (P1), thus obtaining an electric production mean cost, as shown hereafter :

        CM élec =
                    ( CHE2 - CHE1 )
                          P1

        The last calculation is a classic run using the "avoided cost" method, simply replacing the
        electric purchase price by the electric mean cost calculated at the end of the second run.


           5.4. Results

              5.4.1. Labels

        Mean costs calculation results can be seen on the flowsheet, in white color labels. These
        labels allow to visualize simultaneously all network mean costs, as shown hereafter:




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             5.4.2. Results for each unit operation

        For each unit operation, calculated mean costs are presented on the results tab ("simulation"
        tab or "optimization" tab). As an example, results for a mono-fuel boiler and for a turbo-
        alternator are presented hereafter:




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             5.4.3. General results

        A total balance of the power plant, in term of mean costs, allows to simultaneously visualize
        the various utilities production costs, but also the losses, as shown hereafter:




        Losses, internal productions and fuel consumptions of the power plant can be observed in
        details, using the dedicated "Losses", "Turbine action", "Auxiliaries" and/or "Fuels" buttons


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        of the results window. The windows hereafter present these detailed results, for the previous
        example.




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        The financial balance results window is proposed hereafter:




        Note : the total exploitation cost of the power plant is equal to the total cost calculated by
        summing all calculated mean costs. In other words, mean costs method allows a complete
        distribution of the total exploitation cost, which is the first objective of a mean production
        cost calculation method.




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        6. Marginal costs calculation

        After convergence of an optimization run, "marginal costs calculation…" option becomes
        accessible, in the "Calculations" menu, "Start" heading, as presented hereafter:




        The window that then appears is presented hereafter:




        All the produced utilities, according to the power plant specified configuration, are listed in
        the window corresponding to marginal costs.

        The table second column is used to specify the utilities for which a marginal production cost
        has to be calculated. For each utility, it is possible to specify a production increment, which
        will be used for the marginal cost calculation.

        In the specific case of permutable turbines, which are only "on" or "off" , the two following
        precisions have to be noted:
                Turbine appears in the table only if it is stopped;
                The supplied increment is used to calculate the marginal cost, the turbine is then set
                "on", without taking into account the user defined value.




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        A check box allows to impose a marginal cost calculation with a "constant SO2 emission". If
        this option is not selected, emission variation due to user defined increment is calculated and
        presented in the table fourth column.

        The "Calculate" button allows to start calculation. The number of necessary runs is equal to
        the number of user defined increments.

        After calculation, marginal costs are displayed on the previously described table, in the third
        column.

        Using this method allows to study all produced utilities at a given time, in term of marginal
        cost. In others words, this calculation method answers a fundamental question, for a power
        plant manager: What is the price of X supplementary hourly tons of such or such utility ?




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        7. Optimization with stop


           7.1. Generalities

        Optimization with stop aims to determine the unit operations that have to be stopped to reduce
        (minimize) total operating cost. These unit operations are then automatically switched to
        "stopped" mode. Concerned unit operations have been set to the minimum operating point
        (technical minimum) by the classical optimization, this technical minimum not being equal to
        the "stopped" mode (see example hereafter).

        Let us take the example of a turbine (turbo alternator) for which steam flowrate constraints
        have been set between 2 and 50 ton/h (user defined constraints). If optimization calculations
        lead to a flowrate equal to 2 ton/h, for this unit operation, one can wonder whether stopping it
        would not be more profitable from an operating cost point of view. In other words,
        optimization with stop deals with unit operations that classical optimization run has set to
        their minimum operating point (indeed, it can be noted that if all unit operations minima are
        zero, classical optimization is sufficient to determine the unit operations which have to be
        stopped: the ones whose flowrates are set to zero).

        The problem becomes complex although it does not constitute a true mixed integer non linear
        problem (MINLP), considering that integer problem is limited to a stopping problem and does
        not consists in an optimal structure research. For this reason, but also to limit computing time,
        a specific heuristic method has been chosen to solve the discrete problem, rather than to use
        heavier MINLP methods (mixed integer non linear programming) or to NLP-stochastic
        algorithm couplings (coupling between NLP and a simulated annealing method or a genetic
        algorithm). In our case, the developed heuristic calls NLP procedure which becomes the
        "slave" procedure of the main problem.


           7.2. Heuristic description

        Optimization with stop run requires several stages:

        First stage
        The first stage is only a "classical" optimization of the problem. This run provides a reference
        criterion CRIT1 and also a list of NEQ unit operations that optimization has set to their
        minimum, non zero operating point. In case of empty list, no unit operation can be stopped,
        the problem is finished and the optimal criterion is CRIT1.

        Second stage
        The unit operations of the previously described list are modified: their minimum operating
        point is set to zero (minimum flowrate, minimum power...) and optimization is re-started,
        providing a second criterion CRIT2.

               If CRIT1 = CRIT2, unit operations stopping method does not allow any profit, the
               problem is finished, the optimal criterion is CRIT1.




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               If CRIT1 > CRIT2 and all the NEQ unit operations of the previous list are in one of
               the two following situations:
                 1 > their final operating point is zero;
                 2 > their final operating point is higher or equal to their real minimum operating
                 point.

        The problem is finished, the unit operations that are in the first situation have to be stopped
        and the optimal criterion is CRIT2.

               If CRIT1 > CRIT2 and 1 of the NEQ unit operations are in the unauthorized situation
               described below:
                 1 > higher than zero;
                 2 > lower than the real minimum operating point.

        The problem is not finished, because the found intermediate solution is unfeasible. Let us
        consider the number NR of unit operations that meet the problem of unauthorized state.

        Third stage
        The third stage is an iterative stage. From the NR unit operations, one is selected, to which are
        re-affected its real minimum operating points. This selected unit operation is declared
        "unstoppable" for the rest of the procedure. The second stage is then reactivated, with NEQ =
        NEQ - 1.

        The iteration continues until convergence is obtained at stage 2 or when the NEQ unit
        operations become "unstoppable" (in this case, optimal criterion is finally CRIT1).

        Advantage of this method is the computing time. Disadvantage, is that optimal solution can
        not be guaranteed, because of the arbitrary choice at stage 3, which suppresses "optimality"
        concept. In fact, the choice of a unit operation (among the NR) must be judicious; it is the
        case in the method developed in ARIANE™ software.

        Moreover, it should be noted that generally, the first two stages are sufficient to obtain
        convergence, and, in this configuration, optimal solution is guaranteed. In the most
        unfavorable cases, NEQ + 2 optimizations have to be carried out.




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          7.3. "Optimization with stop" execution

        Windows hereafter present classical evolution during "optimization with stop" execution:

                                             1 > Basic problem




                                       2> Start   optimization with stop

        To start the execution, choose "Calculations" menu, "Start" heading, "Optimization with
        stop" subheading. It is also possible to use the Maj+F9 dedicated short cut.




                                           3 > First stage results




        • CRIT1 = 1366.24

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                       Warnings present unit operations that can "a priori" be stopped.




                               A message announces end of first stage ending.




                                              4 > Second stage




        • CRIT2 = 1160.03

                                           5 > End of calculation

        Unit operations labels allow a direct visualization of unit operations that have been stopped;
        in the present case, two boilers (electric and mono-fuel), a turbo-alternator and a valve.



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        The previously presented calculation required two successive optimizations. The obtained
        solution is optimal.




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        8. Multi-periods optimization

        The multi-periods optimization enables to calculate successively configurations (which can be
        more or less different) while assigning one specific duration to each period.

        To reach the multi-periods optimization, select the "Calculations" menu, then the "Multi-
        periods optimization" heading.




        The following window appears:




        This window makes it possible to generate (or modify) the list of optimization files that make
        up the required optimization. This list can be saved in a file with extension ".mul" (i.e.:
        filename.mul). The "Opt" column indicates whether the file has already been optimized (O)
        or not (N). The "NC" column indicates whether the file encountered convergence problems
        during its optimization (O) or not (N). Finally the "Duration" column displays the duration
        required for the period corresponding to the file.

        To run a multi-periods execution, use the "Optimize" tab of the window. It should be noted
        that if all the files of the list have already been optimized ("Opt" column filled with "O") no
        optimization is carried out, as the multi-periods optimization only consists in organizing
        (compile) the results according to the respective durations of the ranges.

        The results are displayed in the form of a total balance as presented hereafter:




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                                Multi-periods optimization financial balance

        As an example, the multi-periods optimization can be used to simulate, in a configuration that
        remains unchanged, the tariff modifications of electricity.




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                                        ARIANE                                Networks
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                                                   CHAPTER 3 : Networks

                                                                  CONTENTS

     1. General description ..........................................................................................................................1

         1.1. Steam network..........................................................................................................................1

         1.2. Hot water network ....................................................................................................................1

     2. Network description.........................................................................................................................3

     3. Networks modeling ..........................................................................................................................5

     4. Labels ...............................................................................................................................................6




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     1. General description

     The first objective of a power plant is to satisfy the demand in steam and hot water of associated
     production units. The required quantity of steam is specified, with a given level of pressure, and
     temperature can also be fixed. The hot water flowrate is also a set point for the plant, the
     temperature of provided water either being fixed, or included in a previously defined interval.

     The production units are also likely to send back to the plant a known quantity of residual steam (or
     hot water), at a given pressure and at a temperature also supposed to be perfectly controlled.

     In addition, a waste steam pipe is associated to each network (or a purging for the water networks),
     which makes it possible to evacuate the possible production surpluses.


        1.1. Steam network

     A steam network is characterized by:

        •   a pressure level ;
        •   an acceptable temperature interval. Note that the steam saturation temperature at the
            network pressure is the minimum bound authorized for the network minimal temperature ;
        •   a "factory demand" in steam (in tons / hours), which can be described unit by unit;

     and possibly:

        •   a set point or de-superheating temperature (accurate specification of the outlet temperature).
            In this case, a "network output valve " allows to lower (to de-superheat) the steam to the set
            point temperature.
        •   a steam production of the producing units, at the network pressure, in quantity and at a
            temperature to be specified.
        •   a waste steam pipe.




        1.2. Hot water network

     A hot water network is characterized by:
        • a pressure level ;
        • an acceptable temperature interval. Note that the network maximum temperature is the
            steam saturation temperature at the network pressure
        • a "factory demand" in hot water (in tons / hours) that can be described unit by unit
        • a purging (compulsory for water networks).

     and possibly:

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        •   a set point temperature (accurate specification of the outlet temperature). In this case, an
            exchanger is used to increase the produced hot water temperature.
        •   a hot water production of the producing units, at the network pressure, in quantity and at a
            temperature to be specified.




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     2. Network description

     To describe a network, use the "Network" menu, then the "Add…" heading or directly select a
     network by clicking on the       icon of the unit operations bar.




     The first elements to be supplied relate to the network Identification: name, type (hot water or
     steam), operating pressure and temperature bounds. The saturation temperature is supplied to
     present the lower bound (steam) or higher bound (hot water) which will not be exceeded by the
     input values. The window also presents the name of the input (unit operation which output is
     connected to the network) and output connected unit operations (unit operations fed by the
     network).


     To be able to validate the creation of the network, the "factory demand" should also be defined.
     This window allows to describe the consumption and possibly the production of the units connected
     to the plant (provided that the unit is started). For the production (quantity of steam or hot water
     entering back in the power plant), it is imperative to define a temperature.




                 The simulator only manages one production stream and one consumption stream. The
                 sum of the units’ consumption thus defines the set point flowrate of the production
                 total stream for the network, whereas the sum of the units’ production flowrates
      Caution
                 defines the total stream entering the power plant. For the temperature of the latter, the
                 software carries out a weighted average of the temperatures of the various streams
                 sent back by the units.


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     The steam network options can be defined by "double-clicking" on the waste steam pipe or on the
     network output valve. For the hot water network, only the purging is directly accessible; to specify a
     hot water outlet temperature, it is necessary to define a particular heat exchanger ("Steam / Hot
     water" standard heat exchanger, see Chapter 4).

     Steam network options:

     - Waste steam pipe




     The waste steam pipe is defined by an "Automatic", "Stopped" or "Out of order" state and by a
     maximum authorized bound ("Constraints" tab) for the waste steam pipe flowrate. Caution: only the
     maximum bound on the waste steam pipe flowrate is taken into account in the calculation, not the
     minimal bound. According to the mode of calculation and to the flowsheet, the setting in
     "Automatic" state of the network waste steam pipe can prove to be compulsory or not (see Chapter
     2).


     - Network output valve

     The network output valve is a "pseudo de-heating valve" (see Chapter 4) for which only the
     automatic mode is authorized. Only the set point temperature of the valve output steam has to be
     specified.


     Water network option: purging

     A water network purging is defined in a way similar to the network waste steam pipe. The
     fundamental difference between the two is due to the fact that the purging must always be in
     automatic mode so that the calculation can be run (Chapter 2), whatever the flowsheet and whatever
     the mode of calculation may be.
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     3. Networks modeling

     From a modeling point of view, a network is the succession of two phases, a mixing phase (inlet
     stream mixing), then a division phase (separation) of the streams. Inlet streams are initially mixed
     (sum of the material and enthalpic flowrates), which enables to calculate the temperature of the
     mixture that is the real network temperature. Then, the calculated total stream is divided up among
     the network various outlet streams, among which can be the waste steam pipe stream (or purging)
     or the production stream.

     Two significant points have to be noted:
       • the so calculated temperature is not a linear function of the input flowrates, even if the
            deviation with the linearity can prove to be small when all inlet streams have close
            temperatures.
       • the warming (or cooling) possibly imposed on the production stream is only carried out
            when the mixing temperature is higher than the de-superheating temperature imposed for a
            steam network, or lower than the final set point temperature for a water network.




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     4. Labels

     The labels displayed on an flowsheet make it possible to quickly visualize all the descriptive
     elements of a network:




     Network & Production

            1: Set point production flowrate in tons/hours.
            2: Network relative pressure in bars.
            3: Network temperature in °C (before calculation, this label displays the average temperature
              of the bounds defined by the user; after calculation, this label displays the network real
              temperature).

     In the event of waste steam pipe:

            4: State of the waste steam pipe.
            5: After calculation, waste steam pipe stream flowrate (tons/hour).

     In the event of de-superheating on the production stream:

            6: State of the network output valve.
            7: After calculation, flowrate in the heat valve (tons/hour).
            8: De-superheating temperature imposed in °C or real temperature if the de-superheating is
               not carried out (°C).

     In the event of steam return coming from the manufacturing units:

             9: Input flowrate on the network, provided by the producing units (tons/hour).
            10: Temperature of this stream (°C).




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                                        Ariane                          Unit Operations
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                                     CHAPTER 4: UNIT OPERATIONS

                                                                  CONTENTS
     1. General presentation – Common tabs ……………………………………… ……………………1
        1.1. Design.......................................................................................................................................1
        1.2. Constraints................................................................................................................................1
        1.3. Operation ..................................................................................................................................2
        1.4. Investment – Maintenance .......................................................................................................2
        1.5. Results: "Simulation" or "Optimization" tabs ..........................................................................2
        1.6. Comparative tab .......................................................................................................................2
     2. Boilers ..............................................................................................................................................4
        2.1. Electric boiler ...........................................................................................................................5
           2.1.1. Design and Operation ......................................................................................................5
           2.1.2. Constraints ........................................................................................................................7
           2.1.3. Investment and maintenance ............................................................................................7
           2.1.4. Controls on data input.......................................................................................................8
           2.1.5. Standby mode ...................................................................................................................8
           2.1.6. Electric boiler options.......................................................................................................9
           2.1.7. Results ............................................................................................................................10
           2.1.8. Electric boiler model ......................................................................................................11
        2.2. Mono-fuel boiler ....................................................................................................................12
           2.2.1. Design.............................................................................................................................12
           2.2.2. Constraints ......................................................................................................................13
           2.2.3. Operation tab ..................................................................................................................14
           2.2.4. Auxiliaries ......................................................................................................................14
           2.2.5. Pre-treatments .................................................................................................................15
           2.2.6. Other descriptive elements of a mono-fuel boiler ..........................................................16
           2.2.7. Calculation results ..........................................................................................................16
           2.2.8. Mono-fuel boiler model..................................................................................................17
        2.3. Bi-fuel boiler ..........................................................................................................................19
           2.3.1. Design.............................................................................................................................19
           2.3.2. Constraints ......................................................................................................................20
           2.3.3. Operation ........................................................................................................................21
           2.3.4. Other descriptive elements .............................................................................................21
           2.3.5. Results ............................................................................................................................22
           2.3.6. Bi-fuel boiler model........................................................................................................22
        2.4. Imported utilities (steam or hot water) ...................................................................................23
     3. Transfer unit operations (valves and turbines)...............................................................................24
        3.1. De-superheating concept ........................................................................................................24
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           3.1.1. Calculation principle.......................................................................................................24
           3.1.2. De-superheating specifications.......................................................................................25
        3.2. ExpansionValves ....................................................................................................................25
           3.2.1. De-superheated valve - network output valve ................................................................26
           3.2.2. Expansion valve model...................................................................................................26
        3.3. Turbines..................................................................................................................................26
           3.3.1. Turbine model.................................................................................................................27
           3.3.2. Turbine constraints .........................................................................................................28
           3.3.3. Turbo-alternator – Simple switchable turbine ................................................................29
           3.3.4. Sidestream turbine - Sidestream condensing turbine .....................................................30
           3.3.5. Condensing turbine.........................................................................................................31
           3.3.6. Turbo generator of special utilities (cold, compressed air) ............................................32
           3.3.7. Permutable turbine..........................................................................................................36
           3.3.8. Switchable turbines.........................................................................................................39
     4. Other unit operations......................................................................................................................42
        4.1. Deaerator ................................................................................................................................42
        4.2. Deaerator modeling ................................................................................................................42
        4.3. Demineralized water pre-heating ...........................................................................................45
        4.4. Deaerator and preheater auxiliaries........................................................................................46
        4.5. "Simple" heat exchanger ........................................................................................................47
           4.5.1. Heat exchanger modeling ...............................................................................................48
           4.5.2. Controls on data input.....................................................................................................48
           4.5.3. Exchange on water network ...........................................................................................49
           4.5.4. Exchange on deaerated water .........................................................................................51
           4.5.5. Exchange on a boiler input fluid.....................................................................................53
           4.5.6. Graphical objects ............................................................................................................54
        4.6. Steam pricking........................................................................................................................55
     5. Cogeneration unit operations .........................................................................................................57
        5.1. General presentation...............................................................................................................57
           5.1.1. Cogeneration...................................................................................................................57
           5.1.2. Constraints ......................................................................................................................57
           5.1.3. Unit operations sequence and operating modes .............................................................57
           5.1.4. Investment / Maintenance...............................................................................................60
        5.2. Fuel turbine ............................................................................................................................61
           5.2.1. General presentation .......................................................................................................61
           5.2.2. Design - Constraints - Operation ....................................................................................61
           5.2.3. Modeling.........................................................................................................................63
           5.2.4. Fuel turbine calculation results.......................................................................................65
        5.3. The thermal engine.................................................................................................................66
           5.3.1. General standard .............................................................................................................66

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           5.3.2. Design - Constraints - Operation ....................................................................................66
           5.3.3. Calculations ....................................................................................................................68
        5.4. The post-combustion boiler....................................................................................................68
           5.4.1. Design - Constraints - Operation ....................................................................................68
           5.4.2. Modeling of the post-combustion boiler ........................................................................69
        5.5. Recovery exchangers cascade ................................................................................................70
           5.5.1. Design - Constraints - Operation. ...................................................................................71
           5.5.2. Recovery heat exchanger modeling................................................................................72




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     1. General presentation – Common tabs

     ARIANE contains a standard library of unit operations usually used in power plants. These unit
     operations, detailed hereafter, can be classified in five categories:




                Boilers (steam or hot water);
                Unit operations of steam transfer between networks (valves and turbines);
                Cogeneration unit operations;
                Other unit operations (deaerator, heat exchanger and steam pricking);
                Fuel networks (see Chapter 7).

     To guarantee the software homogeneity and coherence, each graphical object is composed of
     several tabs for the unit operation definition and the calculation results display. All unit operations
     common tabs are presented hereafter.


        1.1. Design

     This tab allows to define each unit operation design data. Necessary information is described below:
            Name (for all unit operations);
            Connection networks (for boilers, transfer unit operations, deaerator, heat exchangers…);
            Fuels used (for boilers, fuel turbine, thermal engine, post combustion boiler);
            Deaerator (for boilers, fuel turbine, thermal engine and de-superheating unit operations);
            Yield curve (for boilers, fuel turbine, thermal engine and turbines);
            Additional specific data.


        1.2. Constraints

     The "Constraints" tab is used to define the unit operations technical limits. Operating bounds of
     each unit operation are thus defined. As an example, a turbine could be bounded in flowrate and
     power, as presented hereafter:

     Let us consider Q, the input flowrate of a given turbine, and P the corresponding produced power;
     constraints are used to limit the turbine operating field by the two following inequalities:

                                   Q min < Q < Q max and     Pmin < P < Pmax


     with, Q min Pmin minimum and Q max Pmax maximum user defined bounds. In terms of equations,
     defining bounds on two operating parameters is equivalent to generate four inequalities constraints.
     These inequalities constraints are known as "local" because the unit operation is able to calculate
     its own constraints. Technical limits of a given unit operation are thus defined, in the "constraints"
     tab. Usually, constraints relate to temperature, flowrate (steam or fuel), or power. More specific

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     constraints, like smokes or air flowrate in a fuel turbine, for example, will be described according to
     each case.

     The defined constraints can be weighted (constraint weight can be modified) by using the dedicated
     weighting coefficients. 4 values are possible:

        0       : no weighting;
        -1      : constraint weight reinforcement for a better consideration;
        1       : constraint weight weakening;
        2       : constraint consideration important weakening;
        3       : constraint elimination;



        1.3. Operation

     The "Operation" tab finalizes the unit operation definition. This tab allows to define some
     additional information and finally the selected operating mode (unit operation "State").


        1.4. Investment – Maintenance

     This tab is an option that allows to integrate hourly costs, in term of investment but also in term of
     maintenance. Each unit operation, according to user defined data (technology, correlation
     selected...), calculates its own investment and maintenance cost, which can eventually be integrated
     into the power plant estimated total cost.


        1.5. Results: "Simulation" or "Optimization" tabs

     According to the selected unit operation and selected calculation mode, results are displayed in one
     or the other results window, where specific results of each unit operation are detailed. They are
     organized in order to dispose of a global view of both data and results. In the following paragraphs,
     carried out calculations and available results will be detailed for each unit operation, starting from
     the used models description.




        1.6. Comparative tab

     This tab presents the results obtained in Simulation and/or Optimization as shown hereafter, for a
     mono-fuel boiler.




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     This tab presents the exhaustive list of model variables, i.e. it contains some results that are not
     shown in the "Results" tab (for clearness reasons). As an example, the results relating to input and
     output streams energy, usable to make a energy balance, are not displayed in the "Results" tab but
     they are available in the "Comparative" tab. Excel export and HTML file generation concern all
     the variables of the "comparative" tab.

     In addition, when calculations have been carried out in simulation before optimization, this tab
     contains both results and allows an easy comparison between the two calculation modes.




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     2. Boilers

     To add this type of unit operation, select "Unit operations" menu, "add…" heading




     or use the dedicated short cut buttons of the vertical bar, located on the right part of the screen:




          Electric boiler                    Mono-fuel boiler                        Bi-fuel boiler

     To modify a unit operation, select the "Unit operations" menu, "Lists" heading and "left double
     click" on the interesting unit operation, in the presented tab, which contains all unit operations (and
     also all networks).




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     It is also possible to select the desired unit operation by "a left double-click" directly on the
     graphical object representation (on the flowsheet).

     In addition, for a simplified access to a given unit operation (for modification, as presented above),
     the software allows several sorting methods (to sort unit operations but also networks). Unit
     operations can thus be sorted by name, by type, by state (operating mode) or finally according to an
     additional attribute (geographical attribute for example) that can be defined for each unit operation.
     Networks are sorted either by name, type or pressure level (for steam networks).

     For power plants with many parallel unit operations, the entire flowsheet draw visualization
     becomes sometimes difficult. The software then allows to superimpose all parallel unit operations
     and to access them as follows:
        - To obtain the foreground visualization of a desired unit operation (among all the
             superimposed ones), exert a simple clicking on the desired unit operation, in the sorted list.
             On flowsheet draw, the selected unit operation will be presented in the foreground with its
             corresponding labels.
        - To access a desired unit operation, double clicking, as presented before, is sufficient.


        2.1. Electric boiler

           2.1.1. Design and Operation

     To "Design" an electric boiler, the following elements have to be defined:
           Unit operation user name;
           Connected network (the output network (steam or hot water network) is used to determine
           whether the defined boiler is a steam boiler or a hot water heater);
           Deaerator (feed water provider);
           Boiler yield (in %).




                It is advised to define the deaerators (water provider) before defining the boilers

      Advice




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                                        Electric boiler "Design" tab

     The        button calls a fitting routine, which provides a helpful method to determine boiler yield
     from user defined experimental data (see Chapter 5 "Fitting methods") .

     For Operation, necessary specifications are as follows:
           Operating mode (stopped, automatic (with or without user initialization), manual or
           "standby" mode);
           Output temperature (steam or hot water);
           Output flowrate (if unit operation is in a manual mode);
           Initial flowrate (if unit operation is in an automatic mode).




                                       Electric boiler "Operation" tab


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          2.1.2. Constraints

     Three kinds of technical constraints have to be specified: generated flowrate (steam or hot water),
     output temperature and electric consumption. Minimum and maximum bounds have to be set for
     these three physical limits. The window hereafter presents the electric boiler "Constraints" tab:




                                      Electric boiler "Constraints" tab


          2.1.3. Investment and maintenance

     For all boilers, maintenance and investment costs formulation are presented as follows, in the
     electric boiler case:




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     With regard to investment, the cost can either be directly supplied by the user or calculated by one
     of the two available correlations, both depending on the boiler maximum power. An over cost (in
     %) can be applied depending on the boiler technology, in the case of a superheater item, for
     example.

     The investment is expressed as an hourly cost, taking into account the annual operating time and
     depreciation time (expressed in years). The investment can then be weighted by using a
     depreciation coefficient ([ 0,1 ]).

     Regarding maintenance, the method is quite similar. Maintenance cost can be expressed as a direct
     cost, as a percentage of investment cost or as a function of operating power (depending then of
     current operating point).



          2.1.4. Controls on data input

     To avoid problems when running a calculation, a rigorous control is carried out on data input, in
     order to ensure the consistency of all the input parameters. As an example, the controls carried out
     on a boiler input data are presented hereafter:

            Control on the temperature bounds
            Connected network being defined, the boiler defined temperature interval has to be included
            in the network previously defined temperature interval.


            Consistency control between specified value and defined constraints
            The defined outlet temperature must be included in the defined temperature interval and if
            the operating mode is manual, it must be the same for the fixed flowrate.


     Controls of this type have been set up for all the unit operations. If inconsistencies are detected,
     some input fields become "red" and validation button is deactivated.


          2.1.5. Standby mode

     The standby mode characterizes a boiler with an output flowrate equal to zero but which is
     maintained in temperature to allow a quick restart. As presented hereafter, standby mode is
     accessible in the boiler "Operation" tab:


     In term of modeling, the standby mode is defined by one of the three following options:




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            Constant electrical consumption, defined by the user;
            Consumption as a percentage of the electrical consumption when boiler reaches its
            maximum load;
            Consumption as a percentage of maximum electric power consumption defined by the user.

     The "Standby" mode window is presented hereafter:




           2.1.6. Electric boiler options

     Two options are proposed for the electric boiler, as presented hereafter:




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                                          Electric boiler "Options" tab

     The first option consists in defining losses for the boiler. The losses, which are expressed as a linear
     function of the admission flowrate, are considered at boiler output pressure and at a temperature
     equal to:
             Saturation temperature for steam boilers,
             Defined output temperature for hot water heater.

     The second option allows to define a flash on the boiler purge (others process streams may also be
     recycled on this flash), at a user-defined pressure. The flash output steam can be recycled on a
     chosen process steam network. The flash liquid output is usually a process output.


           2.1.7. Results

     Displayed results depend on the calculation mode. In simulation, only electric power consumption
     that is consumed is calculated (the boiler specific electric consumption is sent towards a dedicated
     "adding module", in charge of evaluating all global constraints and of calculating the total operating
     cost). In optimization, the flowrate adjusted by the optimizer is presented as a result. These results
     are displayed on the flowsheet. Maintenance and investment costs, expressed in euros/h, are
     presented in the unit operation "Inv/Maint" tab.




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                                   Optimization results example, for an electric boiler



             2.1.8. Electric boiler model


               2.1.8.1. Electric cost calculation

     An electric boiler is modeled by a yield, expressed in percentage. The input fluid energy as well as
     the output fluid energy (user defined data) being perfectly known, the electric consumption P is
     calculated according to following equation:

                                  Q s .( H s (Ts , Ps ) - H e ( Te , Pe   )) + Q p ( H p ( Tp , Ps   ) - H e (Te , Pe ))
                             P=
                                                                          Rdt
                                                                          100

                                                               Qe = Qs + Q p

     with:
                      P:                   electric power consumption
                      Qe                   admission flowrate
                      Qs                   output flowrate
                      Qp                   "losses" flowrate
                      Rdt:                 boiler yield (in %)
                      Hs                   output stream enthalpy (steam or hot water)
                      Hp                   purge stream enthalpy
                      He                   feed water enthalpy

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     The electric power consumption depends in fact, on a linear way, on the output generated flowrate
     (as a consequence, the electric boiler cost is also a linear function of the boiler load, when electric
     purchase price remains constant).


              2.1.8.2. Production cost calculation

     The production cost of the main output stream (steam or hot water) both integrates the electric cost
     and the water feed cost (calculated on deaerator, which is the boiler supplier). Losses cost is cut off
     this total cost.

     If a flash is defined, the flash output steam cost (steam can be recycled on a steam network) is
     calculated starting from the various input costs, by using a repartition mode (see mean costs
     calculation).


        2.2. Mono-fuel boiler

     The mono-fuel boiler consumes a fuel chosen in the utilities framework or defined on a fuel
     network.


           2.2.1. Design

     The "Design" tab of a mono-fuel boiler is present hereafter:




                                      "Design" tab of a mono-fuel boiler
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     In addition to the "user" name given to the boiler, this tab allows to specify:
             Connected network,
             Deaerator providing feed water,
             Yield curve (as a function of the boiler load) and reference conditions (air temperature and
             excess) for defined yield curve,
             Used fuel.

     Used fuel can be:
            One of the fuels described in the utilities framework (see Chapter 6),
            Fuel network (see Chapter 7).

          2.2.2. Constraints

     The "Constraints" tab of the mono-fuel boiler is presented below:




                                    "Constraints" tab of a mono-fuel boiler

     Three kinds of bounds allow to limit the mono-fuel boiler operating point :
            Output temperature,
            Output flowrate (steam or hot water),
            Consumed fuel flowrate.




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          2.2.3. Operation tab

     The "Operation" tab of the mono-fuel boiler is presented hereafter:




                                      Mono-fuel boiler "Operation" tab

     The mono-fuel boiler operating modes are numerous:
           Standby (like electric boiler, see 2.1.5),
           Automatic (in optimization calculation mode only),
           Automatic with user flowrate initialization (in optimization calculation mode only),
           Manual mode at fixed output flowrate,
           Manual mode at fixed fuel flowrate.

     The boiler model allows to define the problem via a fixed output (the fuel consumption is then
     calculated) or, on the contrary, by imposing a fuel, the model then determines the generated output
     stream.

     The steam (or hot water) output temperature has to be defined. The model also offers two
     possibilities :
             Taking into account an energy brought to the boiler by external sources (heat from some
             smokes furnaces, for example), called "external heat supply", expressed in kW,
             Correcting yield when operating conditions (air temperature and excess) differ from
             reference conditions.

          2.2.4. Auxiliaries

     The boiler operating point may have an influence on other power plant unit operations, such as
     permutable or switchable turbines, for example. In fact, the electricity consumed by the various
     pumps (feed water or fuels pumps) or the boiler air compressor can be supplied either by a network

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     electric call and/or or produced by a turbine. A link between the boiler and possible associated
     turbine is presented hereafter:




                                     Mono fuel boiler "Auxiliaries" tab

     Note: The permutable and switchable turbines are presented in great detail in the followings
           paragraphs of present chapter.


          2.2.5. Pre-treatments

     As presented below, some pre-treatments can be defined for a mono-fuel boiler.




                                  Mono-fuel boiler "Pre-treatments" tab
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     The pre-treatments can be defined only if the corresponding "prickings" or "exchangers" that are
     necessary to their realization have been created before and if the link with the boiler has been
     specified.

     The first possible treatment consists in preheating the air from ambient temperature (user defined
     value) to effective temperature, defined in the boiler "Operation" tab.

     Second treatment is a fuel pre-heating until reaching the user defined temperature.

     Note: These two treatments are carried out using heat exchangers, i.e. unit operations that consume
     steam (on a specified network) and generate condensates (that can be recycled).

     The last pre-treatment, in case of very viscous fuels, allows to atomize it before its injection. To
     perform atomization, steam is directly injected into the fuel stream, in a proportion defined by the
     user (as a fuel flowrate percentage). This treatment is carried out by the "Pricking" unit operation,
     presented in detail in the followings paragraphs of present chapter.

           2.2.6. Other descriptive elements of a mono-fuel boiler

     As presented for the electric boiler, the mono-fuel boiler proposes the following possibilities:
            A standby mode,
            Losses definition ("Options" tab),
            Flash creation on the purge stream ("Options" tab).


           2.2.7. Calculation results

     The window hereafter presents some results, for a mono-fuel boiler.




                                        Mono-fuel boiler "Simulation" tab

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     Results are numerous:
            Output flowrate or fuel flowrate depending on the calculation mode,
            Losses flowrate,
            Pre-treatment auxiliaries steam flowrate ,
            Mean cost of the produced utility (steam or hot water).

     Mean cost of the produced utility (steam or hot water) takes into account:
           Fuel cost,
           Feed water cost,
           Pre-treatments cost (fuel, air or water pre heating, fuel atomization).

     Losses cost is not considered in the mean cost of the produced utility.


           2.2.8. Mono-fuel boiler model

     To characterize a mono-fuel boiler, it is necessary to define the fuel used (one of the fuels defined
     in the utilities list or on a fuel network), the reference air (temperature and excess (in %) of
     reference air) that is used in the model and the real air (air temperature and excess (in %)) used for
     combustion. The "Design" and "Operation" tabs are presented hereafter for a mono-fuel boiler:




                                        Mono-fuel boiler "Design" tab




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                                      Mono-fuel boiler "Operation" tab

     The Yield is expressed as a quadratic function of the boiler "enthalpic load" (energy variation
     between input and output streams):

                                              η    °
                                                       = a.Q 2 + b.Q + c

     with:
             η°           yield of reference;
             Q            boiler load (energy variation);
             A, B, C      yield curve parameters (user defined parameters).

     Then, air excess and air temperature are taken into account in calculations according to the
     formulations presented below:

                                                                1 − Exc 
                                          η = 1 − (1 − η 0 ).             
                                                                1 − Exc 0 

                                              Cp                                        
                               η1 = η. 1 −        . (1 + k ). (1 + Exc). ( T air − T0 ) 
                                             ∆ HC                                       

                M CO2  ∆ H1 − ∆ H C  M H2 O  ∆ H C − ∆ H 2         PO2 . M O2    
     with: k =        .             +       .               / 
                                                                     P .M + P .M      
                M C  ∆ H1 − ∆ H 2  2. M H  ∆ H1 − ∆ H 2    O2       O2     N2 N2 



    and:
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             ∆ HC             enthalpy of fuel combustion (= HCP = 1,1.PCI);
             ∆ H1             enthalpy of carbon combustion;
             ∆ H2             enthalpy of hydrogen combustion;
             PO 2             molar percentage of oxygen in the air;
             PN2              molar percentage of nitrogen in the air;
             M*               molar weights of the various compounds.

     Finally, fuel consumption is obtained by the relation below:

                                                                 Q
                                                   Qcomb =
                                                             η1 .LHV
     with:

               Qcomb          consumed fuel flowrate;
               Q              boiler load;
              η1              boiler yield;
               LHV            fuel low heating value (= HHV / 1.1).

                                Q = Qs . ( H s - H e ) + Q p . ( H p - H e ) − APP − EXT
     with:
               Qs             generated steam flowrate;
               Qp             losses flowrate;
               APP − EXT      external heat supply;
               Hs             output stream enthalpy;
               He             feed water enthalpy;
               Hp             losses enthalpy.


        2.3. Bi-fuel boiler


             2.3.1. Design

     The bi-fuel boiler is quite similar to the mono-fuel boiler previously described, this is the reason
     why it will be proceeded to many carry over paragraph 2.2.




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                                           Bi-fuel boiler "Design" tab

     This tab is very similar to the mono-fuel boiler one (see § 2.2.1.), with the difference that two fuels
     have to be defined.

           2.3.2. Constraints

     The window hereafter presents the bi-fuel boiler "Constraints" tab:




                                        Bi-fuel boiler "Constraints" tab


    On this tab, it appears the same constraints as for the mono-fuel boiler, i.e.:
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            Output temperature bounds,
            Output stream flowrate bounds,
            Fuels flowrate bounds.


           2.3.3. Operation

     The Bi-fuel boiler "Operation" tab is proposed hereafter:




                                         Bi-fuel boiler "Operation" tab

     In addition to the description already done for mono-fuel boiler (see § 2.2.3.), the concept of Fuel
     Ratio appears (energy provided by first fuel / total energy of both fuels).

     This ratio can be free or fixed (free only in Optimization mode).

     In case of "fixed flowrate" calculation mode, it is possible to define the output flowrate and the first
     fuel flowrate, rather than the fuel ratio.


           2.3.4. Other descriptive elements

     As for mono-fuel boiler, various options and pre-treatments can be specified:
            Losses, in the "Options" tab,
            Flash, in the "Options" tab,
            Links between boiler auxiliaries and turbines (permutable or switchable), in the
            "Auxiliaries" tab,
            Air, feed water or fuel(s) pre-heating, in "pre-treatments" tab,
            Fuel(s) atomization, in "pre-treatments" tab.

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             2.3.5. Results

     The bi-fuel boiler simulation results are presented hereafter:




                                           Bi-fuel boiler "Simulation" tab

     The results displayed concern calculated flowrates (output flowrate or fuel(s) flowrate) but also air
     flowrate or losses flowrate.

     Production cost integrates all costs associated to the boiler (fuels, feed water, pre-treatment) and
     also takes into account the losses cost.


             2.3.6. Bi-fuel boiler model

     The yield evaluation is carried out like for the mono-fuel boiler. The difference is that combustion
     equation integrates fuel ratio, as presented hereafter:

                                                      1,1.LHV1 .LHV2
                                      ∆H C =
                                               ratio.LHV2 + (1 − ratio ).LHV1

     with:

              ∆ HC            enthalpy of combustion;
              ratio           fuel ratio;
               LHV1           first fuel low heating value;
               LHV2           second fuel low heating value.


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     Finally, the consumption of both fuels is obtained as follows:
                                                           Q
                                            Qcomb1 =
                                                     η1 .LHV1 .ratio

                                                              Q
                                          Qcomb 2 =
                                                      η1 .LHV2 .(1 − ratio )

     with:

             Qcomb1         first fuel flowrate;
             Qcomb2         second fuel flowrate;
             Q              boiler load;
             ratio          fuel ratio;
             η1             boiler yield;
             LHV1           first fuel low heating value;
             LHV2           second fuel low heating value.



        2.4. Imported utilities (steam or hot water)
     The "imported utilities"        module is an external source (steam or hot water supply) and for this
     reason, it has to be classified with the boilers, as a "feed" for the networks.

     From a design point of view, only the connected network and user name have to be defined. The
     "Constraints" tab allows to define two different input flowrate intervals, each with its own purchase
     price (intervals have to be contiguous). Finally the "Operation" tab allows to specify:
             Input temperature of imported utility;
             Inevitable flowrate (case of manual mode).

     The window hereafter shows the "Operation" tab of the "Imported utilities", in a manual mode.




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     3. Transfer unit operations (valves and turbines)

     Transfer unit operations are generally used to expand steam from a network of higher level towards
     a network of lower pressure level. Two kinds of transfer unit operations will be distinguished :
     valves unit operations and items able to provide a "turbine action" (turbines), which allow electric
     power production. All transfer unit operations available in ARIANETM software are detailed in this
     part.


        3.1. De-superheating concept

     Output stream, from valves or from turbines can be "de-superheated" (output steam is mixed with
     deaerated water to decrease steam output temperature to a user defined level). From a graphical
     point of view, a small arrow entering the unit operation, as a symbolic representation of the de-
     superheating operation, announces de-superheating.




             3.1.1. Calculation principle

     De-superheating operation principle is presented hereafter:

     Let us consider:
             Ps              pressure of output connected network;
             Ts              steam output temperature, before de-superheating;
             Td              user defined de-superheating temperature;
             Tdeg            deaerated water temperature (water used for de-superheating);
              Pdeg           deaerated water pressure (water used for de-superheating);

     Equations system of the de-superheating operation is expressed as follows:

                           Q deg .H deg (Tdeg , Pdeg ) + Q e.H(Ts , Ps ) = Q s. H s (Td , Ps )

                                                  Q deg + Q e = Q s

     with:
              Q deg          deaerated water flowrate;
              Qe             steam flowrate before de-superheating operation;
              Qs             output flowrate of de-superheated steam;
              H deg          deaerated water enthalpy;
              H              steam output enthalpy, before de-superheating;
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            Hs             real output enthalpy of the de-superheated steam.
     Of course, de-superheating has a sense only if the Td user defined temperature is lower than the Ts
     temperature. If such is not the case, no de-superheating operation is carried out. In addition, de-
     superheating temperature must be higher than steam saturation temperature at Ps output pressure.

     If the unit operation is in an automatic mode, the Qe input flowrate is likely to evolve and the
     resolution consists, according to Qe, to calculate the output flowrate (and thus the required water
     flowrate). On the other hand, if the unit operation is in manual mode, the Qs output flowrate is
     specified, in addition to the de-superheating temperature, and it is then necessary to adjust both Qe
     and Qdeg flowrates just to respect constraints on flowrate and on temperature.


          3.1.2. De-superheating specifications

     To specify a de-superheating operation, the user has to select a deaerator (water provider) on the
     "Design" tab, and to specify the de-superheating temperature on the "operation" tab. Window
     below presents the "Operation" tab of a turbine that can manage a de-superheating operation:




        3.2. ExpansionValves

     The expansion valve is a quite simple unit operation, which is defined by a user name and the two
     connected networks. From a technical constraints point of view, only the flowrate is limited. Lastly,
     the operation (apart from the "stopped" or "out of order" modes) is either the "automatic" mode (the
     flowrate is then an action variable in Optimization or the network freedom degree in simulation), or
     the "manual" mode (flowrate is thus constant).

     The window below presents an expansion valve "Operation" tab:
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             3.2.1. De-superheated valve - network output valve

     The de-superheated valve is more complex because the output temperature can be specified.
     The network output valve (on a steam network, see chapter 3) is in fact a de-superheating valve for
     which the output flow rate is specified (specified flow rate is then the network required production).


             3.2.2. Expansion valve model

     The expansion valve modeling rests on the concept of isenthalpic conservation:

                                            H e (Te , Pe ) = H s (Ts , Ps )

     with:

              He , Hs       input and output steam enthalpy (assumed equal);
              Pe , Ps       connected network pressure;
              Te            steam input temperature;
              Ts            calculated value : steam output temperature.


        3.3. Turbines

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     In ARIANE™, a complete set of turbines can be defined: turbo-alternator (with de-superheating or
     not), switchable turbine (with de-superheating or not), permutable turbine, side stream turbine, side
     stream turbine with exhaust condensation, various types of condensing turbines... All these unit
     operations rest on the same principle: a "treatment" by "turbine action" generates both an output
     stream at a lower pressure and electricity that allows to reduce network electric call.


             3.3.1. Turbine model

     The basic turbine model rests on an isentropic concept, as presented hereafter

     Equation of entropy conservation

                                                                 (
                                              S e (Te , Pe ) = Ss Ts* , Ps   )

     Maximum work calculation (under isentropic assumption)

                                                                       (
                                         Wmax = H e (Te , Pe ) − H s Ts* , Ps    )
     with:

                 S e , Ss            entropies of input and output steam;
                 He , Hs             enthalpies of input and output steam;
                 Wmax                maximum work produced by the turbine;
                 Te                  input temperature;
                 Pe                  input pressure;
                 Ps                 output pressure;
                  *
                 Ts                 output temperature under isentropic assumption.


     Isentropic yield

                                            Wréel  H (T , P ) − H s (Ts , Ps )
                                       η=         = e e e
                                                                             (
                                            Wmax H e (Te , Pe ) − H s Ts* , Ps       )
     with:

                 η                          turbine isentropic yield;
                 Wréel                      turbine provided power.


     Yield expressed in a quadratic form



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                                                    2
                                          η = a * Wréel + b * Wréel + c


     where A, B, C are user defined coefficients to characterize the turbine yield. These coefficients
     implicitly integrate both mechanical and energy yield.
     From there, solving gives access to the turbine provided power. (It should be noted that work is
     expressed in kW in the preceding yield expression).


             3.3.2. Turbine constraints

     A turbine is constrained on its flowrate but also on the produced power. The consistency of the
     user-defined constraints is not checked in simulation mode because an inconsistency does not
     involve a simulation failure (warnings are displayed after the simulation run). For an optimization
     calculation, preliminary tests are carried out to check the user defined constraints consistence: let us
     consider Q min , Q max , Pmin , and Pmax being the user defined technical bounds and the function
     P=f(Q), which allows, according to the admission flowrate, to calculate the produced power. If the
     intervals [f( Q min , f( Q max ] and [ Pmin Pmax ] are disjoined, ARIANE detects an inconsistency and
     prohibits calculation starting.

     The defined constraints can be weighted (constraint weight can be modified) by using the dedicated
     weighting coefficients. 5 values are possible:

        -1        :   no weighting;
         0        :   constraint weight reinforcement for a better consideration;
         1        :   decreasing of the constraint weight;
         2        :   important reduction of constraint consideration;
         3        :   constraint elimination.


     This weighting possibility may be very useful when an optimization run presents some convergence
     difficulties.

     As an example, a turbo-alternator "Constraints" tab is presented hereafter :




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     Turbine Investment and maintenance

     Maintenance and investment costs of turbines are quite similar to those described previously for the
     boilers.

     Investment cost is a direct cost or can be obtained by a produced power depending equation. This
     cost is thus brought back to an hourly cost by using depreciation coefficient, annual working time,
     and depreciation time.

     For maintenance cost , it is possible to specify:
           a direct cost;
           an operating point depending cost;
           a cost defined as a percentage of a previously defined investment cost.


          3.3.3. Turbo-alternator – Simple switchable turbine

                 turbo-alternator                  simple switchable turbine

     These two turbines presents only one turbine action stage. In design, the user name, the connected
     networks and the yield curve must be defined. Constraints relate to steam admission flowrate and to
     power, only for the turbo-alternator (a simple switchable turbine does not present produced power
     bounds).

     In operation, the possible operating modes are presented hereafter:

         Stopped
         Manual at fixed flowrate (produced power is then calculated);
         Manual at fixed power (admission flowrate has to be calculated);
         Automatic (power is automatically evaluated in regard to admission flowrate);
         Automatic with user flowrate initialization
         Automatic with user power initialization.
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           3.3.4. Sidestream turbine - Sidestream condensing turbine



                                               Sidestream turbine

     The sidestream turbine consists of two turbines. Admission flowrate enters the first turbine and only
     a fraction of the first stage exhaust enters in the second (exhaust stream), the other part constituting
     the side stream. Side stream ratio is of course an interesting operating parameter, which can be set
     as follows:
             constant side stream flowrate;
             ratio (side/admission) constant or free (free, in optimization mode only).

     Several possibilities of connecting exhaust stream are available:
            connection to a steam network ("classical" side stream turbine requiring 3 steam networks);
            connection to a hot water network;
            direct connection to a deaerator;
            connection to a deaerator with preliminary exhaust sub-cooling (to reach liquid saturation
            temperature).

     Two yield curves have to be defined, as presented hereafter :




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     About constraints, the total produced power is bounded, (the total power is the sum of each turbine
     production), as well as admission flowrate, side stream flowrate and also exhaust flowrate.

     In operation, the operating mode can be set to "manual" (constant required power or constant
     admission flowrate) or to "automatic" (with or without user initialization). Finally if the ratio is used
     (free or specified), it must be indicated at the level of the "Operation" tab. If it is specified, the
     supplied value will be recalled, if the ratio is free, the provided value will be used as initial value.
     For side stream turbine, calculations consist in evaluating produced power and/or admission
     flowrate, but also its specific constraints values.


           3.3.5. Condensing turbine

                                              Condensing turbine

    A condensing turbine is a set of N parallel and identical turbines, a single yield curve is thus
    sufficient to characterize this operation unit. An equal-distribution is operated between the N
    turbines, whose output pressures follow a geometric progression, as presented hereafter.
    Let N being the number of turbines (4 is the default value), the user has to define the last stage
    output pressure and from there, other turbines output pressure are obtained by the following
    relation:
                                          Ps i = Ps i −1 * (Pmin /Pe) (1/N)
    with:
            Ps i           output pressure of stage I (of the ith turbine);
            Ps i −1        output pressure of stage I -1;
            Pmin           user defined pressure for last stage output pressure;
            Pe             input pressure;
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            N               stage number (number of parallel turbines).

     Turbine outputs are supposed to be mixed and the exhaust liquid stream that is formed can be
     specified as follows:
             direct process output;
             connected to a "special heat exchanger" (see details in § 4.1.2) on demineralized water or
             deaerated water of a deaerator (just energy recovery) to be defined. In both cases,
             temperature has to be defined after heat exchange (for turbine condensates);
             direct connection to a deaerator;
             connection to a deaerator, after a condensates sub cooling;
             connected to a hot water network.

     In the window hereafter is presented the condensing turbine "Design" tab:




     The "Constraints" tabs (concerning power and admission flowrate) and "Operation" tab (operating
     mode description) are completely similar to those already described for other turbines.


           3.3.6. Turbo generator of special utilities (cold, compressed air)



                                          Turbo-generator of utilities

     Under the term "Utilities turbo-generator", the software integrates two different unit operations:
            Air turbo compressor;
            Cold turbo generator.

     From the turbine point of view, this equipment item is really "classical ", with a produced power
     depending on admission flowrate, with a user defined yield curve.

     This turbine specificity is its association with two others items to represent the total concept:
     electric motor and auxiliary.



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     The auxiliary consumes electricity to generate compressed air or cold, with a constant defined
     production, i.e. a constant electrical need.

     The "Turbine + Motor" couple has to generate exactly the auxiliary electric power consumption.

     In the case of compressed air, required production is expressed in Nm3/h and the auxiliary
     consumption (required total production for "Turbine + Motor" couple) is obtained as follows :

                                                  PCons = α.Cons

                    Cons : Compressed air required production (in Nm 3/h)
                    α     : Specific consumption coefficient in (kWh/Nm3)
                    PCons : Consumed power (in kW)

     In the case of a cold turbo generator, the required production is presented hereafter:

                                                    PCons = α Pf

                    PF       : Cold power to produce (in cold kW (kWc))
                    α        : Performance coefficient
                     PCons   : Required power (in kW)

     The turbine and motor both contribute to the respect of the assigned electric production, according
     to:
                                                 PCons = PT + PMot

                       with:                 PT = f ( QSteam   )
                                            P
                                    PMot   = network
                                             yield

         PCons      : Required power (to feed auxiliary) (in kW)
         PT         : Turbine produced power (in kW)
         PMot       : Motor electric balance (in kW)
         Pnetwork   : Network electric call (to feed motor) (in kW)
         yield      : Motor yield (auxiliary restored power (by motor) on network electric call
                      called on the network)

     The "Utilities turbo generator" "Design" and "Operation" tab are presented hereafter.




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     The operating mode obeys to a quite simple logic:

            If the auxiliary is stopped, the unit operation is not taken into account during calculation;
            If the auxiliary is "on", the required electric production has to be satisfied:
                 o By motor only, turbine then being stopped
                 o By turbine only (Motor "off ", turbine being then in an implicit "fixed power"
                     operating mode)
                 o By "Turbine + motor" couple, both items then acting simultaneously to satisfy the
                     production constraint



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           3.3.7. Permutable turbine



                                               Permutable turbine

     The permutable turbine is a couple of parallel operting unit operations:
             Steam turbine,
             Electric motor.
     This couple, as previously described for the turbo-generator of utilities, has to supply electricity to a
     third entity: the auxiliary.

     The major operating constraint is an "On/Off" rule. If the motor is "On", the turbine is necessarily
     "Off". If the turbine is "On" (motor is "off "), it has to produce exactly the auxiliary consumed
     power.

     The auxiliary consumed power may be constant or not (linear function of a given flowrate). In the
     case of consumed power variability, an associated equipment item (deaerator or boiler) determines
     the flowrate to be considered in the consumed power linear function (this flowrate can be a pump
     flowrate, or air flowrate if auxiliary is a ventilator).


              3.3.7.1. "Design" tab

     The window hereafter presents the "Design" tab of a permutable turbine:




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              Permutable turbine "Design" tab according to electrical production configuration

     In addition to connected networks and turbine yield curve, the following additional definitions
     should be noted:
            Losses: a losses flowrate (a flowrate which is lost before turbine action) can be defined, as a
            linear function of admission flowrate. These losses are "process outputs" streams,
            Required power: auxiliary electric power consumption, which can be constant or not,
            Motor yield, if turbine is "off".

     If the required power is not constant, a link between the permutable turbine and the associated
     equipment item (boiler or deaerator) is not defined in the permutable turbine that is considered as
     the "slave" item ("master" item is a boiler or a deaerator, and the link is defined in their own
     description tabs).




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             3.3.7.2. "Operation" tab

     The window hereafter presents the permutable turbine "Operation" tab:




                                     Permutable turbine "Operation" tab

     The "estimated" power must be indicated by the user to carry out the turbine initialization for
     optimization. The operating modes of this unit operation governed by a rule "all or nothing" are a
     little different from the other turbines:
              Out of order: steam turbine cannot operate,
              Stopped: steam turbine is stopped but may be by started during calculation run,
              Forced: steam turbine is on and produces exactly the required electricity amount,
              Automatic: turbine operating mode will be adjusted during optimization run.

             3.3.7.3. "Optimization" tab

     The "Optimization" tab shows all available results provided by the calculation run.




                                 "Optimization" tab of a permutable turbine
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     The results displayed are as follows:
            Admission flowrate,
            Produced power, by turbine action PT,
                                                         PT = PR
            Required power PR,
                                                         Or Pr = Pcall.Rdt
            Network electric call Pcall,
            Losses flowrate,
            Mean production cost of both generated utilities (steam and electricity).


          3.3.8. Switchable turbines



                                              Switchable turbine

     The switchable turbine is also a "turbine+motor" association, to supply an auxiliary electric power
     demand. Nevertheless, fundamental differences with the permutable turbine are presented hereafter:
           The previously defined "Turbine + Motor" couple produces at least the required power.
           This means that surplus can be produced, which is valorized on site (no resell),
           Turbine and motor are set on the same axis; this means that motor can be, depending on
           operating conditions, either a producer (turbine mechanical energy surplus allows a rotating
           action of the motor, which becomes an electric producer) or an electricity consumer (to help
           turbine to provide auxiliary power consumption).

     Modeling

     Let us consider PR, auxiliary consumed power and PT, the turbine production (turbine action
     provides a power PT).

        → if PT ≥ PR, energy surplus is used to drive the motor and on site generated electric
          production is expressed as follows : Pprod =
                                                        (PT − PR ) with Yield _ prod , the yield of the
                                                       Yield _ prod
          motor, when generating.

        → if PT < PR, on the contrary, the motor provides the complement to guarantee the necessary
          power (to feed the auxiliary) and the motor consumed power is expressed as follows:
           Pcons =
                    (PR − PT ) with Yield _ cons the yield of the motor when consuming.
                   Yield _ cons

     The window hereafter presents a switchable turbine "Design" tab.




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                                        Switchable turbine "Design" tab

     The only difference with a permutable turbine "Design" tab concerns the specification of two yields
     for the electric motor, the first one to characterize it when generating electricity, the second one to
     characterize it when consuming.

     The produced power and admission flowrate are here necessarily bounded, on the contrary of the
     permutable turbine, because the steam turbine may follow an "autonomous" operating mode, which
     must thus be restricted by technical limits.

     The "Operation" tab of the switchable turbine presents "classical" operating modes, as shown
     hereafter:




                                    Switchable turbine "Operation" tab
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     The estimated power is used for steam turbine initialization when calculation mode is
     "Optimization" and when turbine operating mode is "Automatic".

     Lastly, the "Optimization" tab, presented hereafter, proposes the obtained results, almost similar to
     those described for the permutable turbine:




                                    Switchable turbine "Optimization" tab

     A switchable turbine electric balance is presented, which can, according to operating conditions,
     represent an export or an import of electricity.




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     4. Other unit operations

        4.1. Deaerator

     A deaerator is the water feed of boilers, heat exchangers and also of all de-superheating unit
     operations. In the simplest case, a deaerator mixes demineralized water with a specified recycled
     steam, to form the deaerated water, in constrained quantity (by all the connected unit operations
     demand) and at a user specified temperature.


        4.2. Deaerator modeling

     To provide the specified deaerated water (flowrate and temperature), the deaerator mixes:
            Perfectly defined external condensates (specified in temperature and flowrate),
            Process internal condensates (from condensing turbines, heat exchangers…),
            Demineralized water (or pre-heated, see § 4.3.), for which temperature is user defined and
            flowrate has to be calculated.
            Fixed vapor (stream with fixed flowrate),
            Recycled steam stream which flowrate has to be determined.

     A material and energy balance allows to determine the necessary recycled steam flowrate and
     demineralized flowrate.

     The deaerator "Design" tab, presented hereafter, allows to define a user name, to choose the
     network that provides recycled steam, and possibly to access to the demineralized water definition
     (using dedicated button, which opens this utility description window, in the utilities framework).

     The "Pre-heating" button can be used to define a demineralized water pre-heater, a detailed option
     in the paragraph 4.3.




                                        "Design" tab of a deaerator


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     The "Constraints" tab details the deaerator technical bounds (mainly recycled steam flowrate bound,
     demineralized (or preheated) water flowrate bounds).

     The deaerator "Operation" tab is presented hereafter:




                                          Deaerator "Operation" tab

     This tab allows to define:
             Deaerated water required temperature (or deaerator pressure), these two values being linked
             by water saturation curve,
             External condensates (temperature and flowrate),
             Demineralized (or pre-heated) water temperature.

     The two followings remarks should be noted:
           Fixed vapor, when existing, is not defined in the deaerator but directly in the "Pricking"
           (unit operation that generates fixed vapor),
           Pre-heating button, on the "Operation" tab, is usable for a pre-heater definition (see
           paragraph 4.3).

     Lastly, the "Operation" tab allows to observe:
             The list of unit operations consuming the generated deaerated water,
             The list of unit operations providing internal condensates.
     Both following symbols (     ) represent in fact some energetic feeds on demineralized water or on
     deaerated water, by the way of thermal exchanges with condensing turbine output streams. These
     exchanges are described on the paragraph dedicated to the condensing turbine.

     Results tab ("Simulation" or "Optimization") is presented hereafter:



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                                           Deaerator "Results" tab

     This tab presents the main following results:
            Recycled steam flowrate,
            Demineralized water flowrate,
            Deaerated water mean production cost,
            Deaerated water flowrate (required by consumers),
            Fixed flowrate and external condensates, (possibly),
            Internal condensates (temperature, flowrate).

     A simple click on the dedicated button allows to visualize heat exchange on demineralized or
     deaerated water, as shown hereafter :




                                          Heat exchange between
                                  a condensing turbine and deaerated water

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        4.3. Demineralized water pre-heating

     Water entering a deaerator may be pre-heated, in a dedicated tank vessel called "pre-heater", which
     is nothing else than another deaerator, which provides pre-heated water for the main deaerator (pre-
     heated water then replaces demineralized water in the main deaerator).

     A pre-heater has a demineralized water input, a recycled steam input, and possibly, a fixed vapor
     and condensates (internal and/or external).

     The pre-heater required temperature is set by the user and pre-heated water flowrate is a calculation
     result of the main deaerator.

     To declare a pre-heater , click on the "Pre-heating" button, on the main deaerator "Design" tab. The
     hereafter presented window appears, which allows to define totally the pre-heater tank vessel:




                                               Pre-heater design

     In the deaerator, the "Pre-heating" button of the "Operation" tab allows to specify the pre-heating
     operation as follows:
             Demineralized water temperature,
             Pre-heated water required temperature,
             External and internal condensates.

     By default, internal condensates are affected to the main deaerator; the "+" button has to be used to
     re-affect them to the pre-heater. The "-" button allows to come back to the previous situation.




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                                         Pre-heater specifications tab

     The results shown for the pre-heater are very close to those already presented for the "main"
     deaerator, as shown in the window hereafter:




                                         Pre-heater displayed results


        4.4. Deaerator and preheater auxiliaries

     Like for boilers feed water, various pumps, around the deaerator (or pre-heater) can be linked to
     Permutable or switchable turbines (the power called on these turbine will then depend on the
     deaerator operating mode, more precisely the considered pump flowrate).

     Five pumps can be linked to a turbine for the deaerator, and only one pump, for the pre-heater, as
     shown in the window hereafter:


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                                  "Auxiliaries" tab of the deaerator-preheater

     For the deaerator, a turbine can be connected to a:
             Deaerated water pump,
             External condensates pump,
             Demineralized water pump.

     Two turbines can work in parallel to produce the required electric power to feed deaerated water
     pump.

     For the pre-heater, only the demineralized water pump can be linked with a turbine.


        4.5. "Simple" heat exchanger

     The heat exchanger considered in ARIANE™ allows to prick steam on a network to carry out a
     thermal exchange with:
            hot water of a specified network to obtain a required output temperature;
            deaerated water;
            a boiler input stream.

     The "steam/deaerated water" heat exchangers must not be considered like "pseudo-exchangers"
     defined for condensing turbine exhaust characterization. Both concepts may co-exist in a same
     deaerator.




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          4.5.1. Heat exchanger modeling

     The heat exchanger calculation is based on the knowledge of input and output streams. For the
     heated stream, temperatures before and after exchange as well as flowrate are known. Required heat
     is then calculated as follows:
                                                  E = Q f .[H f (Tfs ) − H f (Tfe )]
     with:

                   E               energy provided to heated fluid;
                   Qf              cold fluid flowrate;
                   Hf              cold fluid enthalpy;
                   Tfs             cold fluid user-defined temperature (after exchange);
                   Tfe             cold fluid stream input temperature (before exchange).

     For hot stream (steam pricking), the temperature before exchange is known (it is the network
     temperature), and the temperature after exchange is specified by the user. Consequently, steam
     flowrate is obtained by:
                                                          E
                                         Qc =
                                               H c (Tce ) − H c (Tcs )
     with:

                    E              exchanged energy;
                    Qc             steam flowrate (to be pricked on the network);
                    Hc             hot fluid enthalpy;
                    Tcs            user defined temperature (after exchange);
                    Tce            network temperature (steam temperature before exchange).

     Enthalpic calculations take into account the steam condensation. A thermal exchange yield "EFF"
     has been established to characterize the thermal losses during the exchange. The steam flowrate
     "pricked" on the network is then:
                                 Q
                          Q c = c with EFF [ 0,1 ], user defined exchanger yield.
                                Eff


          4.5.2. Controls on data input

     Data consistency controls concerning the heat exchanger are done to ensure the exchange
     feasibility, i.e. the entered data respect the following basic concepts: the cold fluid is heated, the
     heat cools, the hot fluid is indeed hotter than the cold fluid, and both fluids temperatures do not
     cross.
                              Tce > Tfs
                           Tcs > Tfe
                           Tcs ≤ Tce
                           Tfe ≤ Tfs

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          4.5.3. Exchange on water network

     Network pricked steam is used to bring up the production of a hot water network to a required
     temperature.

     The "Design" tab of a heat exchanger on "steam/hot water network" is proposed on the window
     below:




                            "Design" tab of a heat exchanger on hot water network
     Are defined at this level:
            User specified name,
            Hot water network,
            Steam provider (network),
            Condensates definition (process output or recycling towards a flash or a deaerator).

     The "Operation" tab presented hereafter allows to define:
           Fluids temperature after exchange,
           Heat exchange yield,
           Exchanger state (On/Off).




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                          "Operation" tab of a heat exchanger on hot water network


     After calculation, a heat exchanger provides the results presented on the window hereafter:




                       Results provided by the heat exchanger on a hot water network

     The two main results are the steam flowrate and exchanged power. In addition, the mean cost of the
     two generated fluids (heated fluid and condensates (or losses)) are displayed.



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     The exchange cost is affected to the hot water production cost. There is no graphical visualization
     of the thermal exchange on the hot water network. Results are presented in the heat exchanger,
     which appears on the flowsheet, as presented hereafter.




                                  Heat exchanger graphical representation


          4.5.4. Exchange on deaerated water

     The deaerated water temperature is specified by the user. The flowrate of this stream depends on
     global operating conditions. It is possible to heat this deaerated water by using a heat exchanger,
     which "Design" tab is presented hereafter:




                           "Design" tab of the heat exchanger on deaerated water

     On this tab are specified : deaerator identification, heat exchanger connected network and
     condensates destination.

     The "Operation" tab presented hereafter allows to specify the heat exchanger state, temperatures
     that have to be defined and heat exchanger yield:




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                          "Operation" tab of the heat exchanger on deaerated water


     The obtained results are presented in the "Simulation" or "Optimization" tab as shown hereafter:




                          "Simulation" tab of the heat exchanger on deaerated water

     The calculated steam flowrate, total exchanged power, and also mean cost of the generated fluids
     (condensates or losses and heated deaerated water) are displayed. The exchange cost is affected to
     deaerated water production cost.


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          4.5.5. Exchange on a boiler input fluid

     Three types of fluids can be considered:
            Feed water,
            Air,
            Fuel.

     The problem is almost the same as for both previous heat exchanger types.

     The "Design" tab of a heat exchange on boiler feed water is presented hereafter.




                            "Design" tab of a heat exchanger on boiler feed water

     The "Operation" tab presented hereafter does not present any particular feature, compared to those
     previously shown:




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                       "Operation" tab of a heat exchanger on the feed water of a boiler

     The "Simulation" or "Optimization" tab allows to show all results already mentioned, like steam
     flowrate or total exchanged power, mainly.

     This heat exchanger is accessible from the boiler whose feed water is preheated, via a dedicated
     short cut button.

     Moreover, in the case of a heat exchanger to pre-heat air or fuel, cold fluid description is done in the
     boiler tab, which is accessible from the heat exchanger, as shown in the window hereafter:




                                    Cold fluid specification: boiler access
                                from the "Operation" tab of the heat exchanger


     For air and fuel, specifications are defined on the boiler "Pretreatments" tab.


           4.5.6. Graphical objects

     Heat exchanger charts are different, depending on cold stream: deaerated water, boiler feed or water
     network:



            Steam / Deaerated water heat exchanger



                Steam/ Water network heat exchanger




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             Steam / Boiler input fluid (water, air, fuel) heat exchanger


        4.6. Steam pricking

     This unit operation is a representation of steam pricking that is carried out on the power plant
     networks, to carry out some special operations.

     The "Design" tab of this unit operation is shown below:




                                             Pricking "Design" tab

     Four different definitions are possible:
            Particular process output: a fixed flowrate of steam is taken on network. This option is
            equivalent to a specified production,
            Fixed steam towards a deaerator,
            Pricking for fuel atomization : this pricking allows to define the link with the boiler which
            fuel has to be atomized (very viscous fuel may need this treatment). Atomization steam
            flowrate is defined, on the boiler tab, as a percentage of the fuel flowrate,
            Steam injection (on a fuel turbine) : this option is nearly the same as the previously defined,
            steam being sent to combustion chamber of a fuel turbine, for various reasons. The link with
            the fuel turbine is defined in the pricking, but injected steam flowrate is defined as a
            percentage of the input fuel flowrate, on the fuel turbine tab.

     The "Operation" tab of a pricking is presented hereafter :

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                                          Pricking "Operation" tab

     The pricking can be "On" or "Off". The flowrate is a user-defined data in the case of a process
     output or a fixed vapor flowrate towards the deaerator. In others cases, it is calculated during the
     run, depending on the boiler or fuel turbine operating mode.




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     5. Cogeneration unit operations

        5.1. General presentation

     Four types of unit operations are part of the classification known as "cogeneration" unit operations:
            fuel turbine (also called gas turbine);
            thermal engine;
            post-combustion boiler;
            recovery exchanger.

     The post-combustion boiler is not defined as a real unit operation (there is no graphical
     representation available in the unit operations bar of the software). Indeed, this unit operation is
     defined as an "extension" of a fuel turbine or thermal engine, as it only exists with these two unit
     operations.

     The specificity of this set of unit operations is that it can be integrated in a cogeneration contract,
     which enables the plant to resell whole or part of the produced electric power.


           5.1.1. Cogeneration

     The term "cogeneration" designates a contract that bounds the thermal plant to produce a fixed
     quantity of electricity, for a sale price clearly specified. The cogeneration contract can be partial or
     total. If it is total, all the electricity produced by this set of unit operations is provided to the
     electricity purchaser. In a partial contract, only the contractual power is provided, the possible
     surplus can be used for in-house needs, as with traditional rotating unit operations. Cogeneration is
     thus defined by three specific attributes of the contract:

         • Contractual power (generated power is at least equal to this power);
         • Resale price;
         • Standard (total or partial).


           5.1.2. Constraints

     There are additional constraints associated with a cogeneration contract, which impose for example
     a minimum ratio between the energy generated in the form of steam or of hot water and generated
     electric energy. These constraints are not taken into account in the current version of the software,
     which leaves a great flexibility in the use of unit operations.


           5.1.3. Unit operations sequence and operating modes

     The fuel turbine (FT) and thermal engine (TE) are two equivalent unit operations: they generate
     electricity and smokes. The post-combustion boiler (PCB) can give back additional energy to the
     turbine or engine output smokes. Finally the recovery exchangers (EXCH) are cascade exchangers
     that make it possible to generate steam or hot water, by using the smokes energy. The operating
     modes of these unit operations are not independent, only the sequences presented below are
     authorized:
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     In simulation




                                    PCB                EXCH            EXCH            EXCH
                                  Stopped                           Automatic
        FT
        or                          PCB                EXCH            EXCH            EXCH
        TE
                                   Manual                           Automatic
      Manual
                                    PCB                EXCH            EXCH            EXCH
                                Automatic              Manual                 Automatic


     The turbine or the thermal engine is in manual mode (specified fuel flowrate or fixed power):
            If the post-combustion boiler is stopped, the exchangers are necessarily in automatic mode;
            If the post-combustion boiler is in manual mode (specified fuel flowrate), the exchangers are
            necessarily in automatic mode;
            If the post-combustion boiler is in automatic mode, one of the exchangers is necessarily in
            fixed flowrate manual mode, the others are in automatic mode. The post-combustion boiler
            fuel flowrate is controlled in order to respect the flowrate fixed for the exchanger in manual
            mode.

     The operating post-combustion boiler (manual or automatic) implies the presence of at least a
     recovery exchanger, as it is not very probable that a plant overheats smokes without taking profit
     from them. In addition, the use of a fuel turbine or a thermal engine as a single unit operation
     remains possible in the software, although it is improbable in the reality, taking into account the
     additional constraints associated to a cogeneration contract (see § 5.1.2).




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     In Optimization


                                        PCB                EXCH          EXCH           EXCH
                                     Stopped
                                                                       Automatic
          FT
          or                            PCB                EXCH          EXCH           EXCH
          TE
                                      Manual
       Manual or                                                       Automatic
       Automatic
                                        PCB                EXCH          EXCH           EXCH
                                    Automatic             Manual                Automatic

                                        PCB                EXCH          EXCH           EXCH
                                     Automatic
                                                                       Automatic

     In "Optimization" mode, flexibility is much more significant since multiple sequences of
     calculation are possible, like presented on the above diagram. The less "constraint" sequence (which
     offers the better flexibility in optimization) is the sequence in which all the unit operations are in
     "automatic" mode.

     When there is possibility to add or not a cogeneration contract, there is great combinative
     possibilities of using cogeneration unit operations.

     Rigorous controls are carried out to check the defined operating modes consistency for the set of
     cogeneration unit operations. As an example, the window presented hereafter appears in simulation
     when no heat exchanger is in manual mode whereas the boiler post-combustion is in automatic
     mode.




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     From a general sizing point of view, note that ARIANE has the following limitations: It authorizes
     only two "groups" of cogeneration for the same plant (2 fuel turbines, 2 thermal engine or 1 engine
     and 1 turbine). In addition, only one cogeneration contract can be defined by plant, which means
     that if several unit operations of cogeneration are defined, they work within the same contract. This
     means that any modification of the contract definition at the level of one unit operation induces the
     same modification for the other implied unit operation.


          5.1.4. Investment / Maintenance

     The notions of investment and maintenance for the cogeneration unit operations are completely
     similar to those presented for boilers and turbines. The window hereafter presents the fuel turbine
     "Inv/Maint" tab.




                                      The fuel turbine "Inv/Maint" tab.




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        5.2. Fuel turbine


           5.2.1. General presentation

     The fuel turbine is a unit operation that, using a specified fuel burning, allows to generate both
     electricity (within the framework of a cogeneration contract or not) and smokes, whose energy can
     be used to generate steam and/or hot water, by using dedicated unit operations, called recovery heat
     exchangers.

     From a technical point of view, the operation is carried out in three phases, inside the fuel turbine:
           Compression phase;
           Combustion;
           Turbine action.

     The electricity is produced during the third phase, when expanding smokes produced during the
     second phase, by a turbine action completely similar to those described for turbine (see § 3).


           5.2.2. Design - Constraints - Operation

     The definition data of a fuel turbine are numerous, as well in Design as in Operation. Unit
     operations technical bounds concern the input and output flowrates and the total produced power.

     Design

     In Design, in addition to the user defined name, the fuel used and the yield curve coefficients have
     to be defined: compressor yield, turbine yield and temperature curve that allows to calculate the real
     temperature of the burning chamber, called fuel turbine high temperature.

     A possible option is to introduce deaerated water (in addition to fuel), in the combustion chamber. If
     this option is selected (check box), the deaerator must be chosen and the mass ratio (as a percentage
     of the fuel flowrate) must be indicated.

     Another possible option consists in injecting steam pricked on a steam network. If this option is
     selected, the steam mass ratio (as a percentage of the fuel flowrate) must be indicated.

     Steam pricking must be placed on the flowsheet and suitably defined before the "Steam injection"
     becomes visible on the fuel turbine "Design" tab.

     Lastly, "Design" data define the turbine action parameters, by describing the combustion chamber
     pressure and the smokes exhaust pressures.




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     The window hereafter presents the fuel turbine "Design" tab.




     Operation

     The operation must define the turbine operating mode, characterize the combustion and define, if
     necessary, the cogeneration contract.

     For the operating mode, the operating turbine can be in mode:
            • automatic (with or without user initialization);
            • manual at fixed fuel flowrate (flowrate to be specified);
            • manual at fixed power (power to be specified).

     To characterize the combustion, the user can define the input air (temperature, excess) or specify
     the high temperature.

     Lastly, the "Cogeneration" tab makes it possible to define the electricity type, power and resale
     price.

     The window hereafter presents a fuel turbine "Operation" tab.




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     Constraints

     The technical constraints of a fuel turbine relate to the following flowrates:
            • input fuel flowrate;
            • input air flowrate;
            • generated smokes flowrate.

     In addition, a minimal value (not necessarily equal to zero) and an acceptable maximum value also
     bound the electric power generated by the turbine.

     These constraints can be weighted to increase or decrease their influence during optimization
     process.


           5.2.3. Modeling

              5.2.3.1. Air compression calculation

     The input/output pressures being known, the input temperature being specified by the user, the
     theoretical work of the air compression is obtained by using the isentropic process concept:

                                              S e (Te, Pe ) = Ss (Ts* , Ps )

                                         Wmin = H e (Te , Pe ) − H s (Ts* , Ps )


     The real output is calculated starting from the minimum work provided by using the efficiency
     curve defined by the user (here, the curve is defined in relation to the minimum work concept):
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                                                    2
                                         Yield = a.Wmin + b.Wmin + c

     And finally, real work corresponding to compression is expresses as follows:

                                                        Wmin
                                                  W=
                                                        Rdt

     with:

             Se            input air entropy;
             Ss            output air entropy;
             Te            input air temperature;
             Pe            input air pressure;
             Ts*           compression adiabatic temperature;
             Ps            compression pressure;
             He            input enthalpy;
             Hs            enthalpy after compression;
             Wmin          minimum work provided;
             W             real work obtained;
             Yield         compression output;
             a, b, c       parameters indicated by the user.


              5.2.3.2. Combustion calculation

     The combustion equation, combined with the calculation of the exact quantity of oxygen necessary
     to combustion, makes it possible to accurately define the generated smokes composition and partial
     flowrates.

     The air flowrate and the air enthalpy being known (after compression), the fuel flowrate being fixed
     (its GCV being specified), and possibly the additional deaerated water flowrate and enthalpy being
     evaluated, the smokes adiabatic enthalpy is obtained, which gives access to the combustion
     adiabatic temperature.

     The high temperature (real temperature after combustion) is obtained by using the temperature
     curve defined by the user, quadratic function of the adiabatic temperature:


                                                      2
                                          Thigh = a.Tadia + b.Tadia + c



     with:

             Thigh       high temperature;
          Tadia          adiabatic temperature;
          a, b, c        used defined parameters.
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             5.2.3.3. Turbine calculation

     The high conditions being perfectly defined (temperature, pressure, and composition), the outlet
     pressure being specified, the turbine calculation is completely the same as for rotating unit
     operations (see Paragraph 3). The isentropic process and isentropic efficiency concept enables to
     calculate on the one hand the real output temperature, and thus the smokes energy level, and on the
     other hand, by using the turbine efficiency curve, the produced electric power.


          5.2.4. Fuel turbine calculation results

     Calculation results provide the following information:
            water, fuel and air flowrates;
            "high" temperature and output smokes temperature;
            smokes flowrate and composition;
            provided power.

     The window hereafter presents an example of results provided for a fuel turbine.




     In addition to the previously evoked results, three additional results characterize the turbine
     operating mode:
            global yield;
            heat/power ratio;
            electric equivalent yield.

     These results are expressed hereafter. Let us consider Pf, characterizing smokes potential energy,
     Pe, total electric produced power and Pc, the fuel power (LHV*fuel flowrate); the "global yield" is
     expressed as follows :
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                                           Yield _ G = ( Pf + Pe ) / Pc

     The "heat/power ratio" is expressed as follows:

                                             Yield _ Q / W = Pf / Pe

     Lastly, the "equivalent electric yield" is expressed by the relation:

                                         Yield _ E eq = Pe / ( Pc - Pf/0.9 )



        5.3. The thermal engine

           5.3.1. General standard

     The thermal engine generates energy by combustion of a utility (fuel to be defined). This energy is
     separated in three parts (in % of the total energy produced by combustion):
            • energy yielded to cool the engine;
            • electric energy produced;
            • energy contained in the produced smokes.

     The energetic "conversion matrix" (distribution in % of the total energy produced by combustion) is
     specified by the user (by default, 15% for cooling, 40% for the electricity, 45% for the smokes).
     The energy produced in the form of electricity intervenes or not in a cogeneration contract. Energy
     associated with cooling is lost if the cooling water is external water (river water for example), on
     the other hand, it can be used if the cooling water is demineralized or deaerated. The energy
     transferred to the smokes is exploitable to generate hot water or steam thanks to the use of recovery
     exchangers, downstream from the engine (with possible preliminary passage of the smokes in a
     post-combustion boiler).


           5.3.2. Design - Constraints - Operation

     In design, the user must define the name of the unit operation, the fuel used, the cooling type of the
     engine and the smokes temperature curve.

     If the selected cooling type is "external water", the user must specify this water input and output
     temperature. The software then calculates the necessary external water flowrate.

     If the cooling type is "demineralized water", it is necessary to specify the concerned deaerator. The
     demineralized water flowrate entering the deaerator will be preheated by the energy released by
     cooling the engine and the value calculated by the software is then the demineralized water
     temperature after exchange.

     Lastly, in the case of cooling with deaerated water, the specified deaerator provides a quantity of
     water (to calculate), which is sent back to a hot water network. The user must specify the deaerated
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     water temperature after cooling the engine and identify the water network supplied with this
     deaerated water.

     At the level of the operation (see window hereafter), the data to be supplied are the following:
          • operating mode (manual at fixed fuel flowrate, manual at fixed, automatic or stopped
             power). In manual, it is necessary to specify the set point value, the power, or the fuel
             flowrate, according to the selected mode;
          • the energetic conversion matrix;
          • specifications on the air (temperature, excess);
          • the engine operating pressure;
          • the cogeneration. A checkbox is used to define or not a cogeneration contract. If this option
             is selected, the "Cogeneration contract" window makes it possible to specify the type (total
             or partial), the power and the resale price.




     The technical constraints of thermal engine are the same as for the fuel turbine, i.e. bounds on
     flowrates (fuel input, air inlet, output smokes flowrate) and on generated power. In addition, bounds
     on cooling water flowrate must be defined for the thermal engine, as presented in the thermal
     engine "Constraints" window.

     Weighting coefficients allow to more or less take into account the defined constraints during the
     optimization process. 5 values may be entered:

            0      : no weighting;
            -1     : constraint weight reinforcement for a better consideration;
            1      : decreasing of the constraint weight;
            2      : important reduction of constraint consideration;
            3      : constraint is nearly eliminated.




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          5.3.3. Calculations

     The principles of the thermal engine calculation are based on the concept of division of power
     generated by combustion between the three elements previously defined. Apart from this
     characteristic, combustion is calculated in the same way as for the fuel turbine, which makes it
     possible to entirely characterize the generated smokes.



        5.4. The post-combustion boiler

          5.4.1. Design - Constraints - Operation

     This unit operation can only be accessed from a window of the fuel turbine or thermal engine. The
     "Post Combustion" link gives access to the boiler definition. The window below presents the link to
     reach the boiler from the fuel turbine "Operation" tab.




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     In design, the name given to the unit operation and the fuel used must be defined. The single
     constraint on this unit operation relates to the fuel flowrate. Lastly, at the level of the "Opertation"
     window, the air used (temperature, excess) and the operating mode (manual, at fixed or automatic
     fuel flowrate) are indicated by the user. The window hereafter presents the post-combustion boiler
     "Operation" tab:




           5.4.2. Modeling of the post-combustion boiler

     The post-combustion boiler is a simplified boiler where combustion is supposed to be adiabatic. In
     other words, the smokes outlet temperature of a post-combustion boiler is a calculated theoretical
     temperature, which is not corrected by a curve to be specified by the user.

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        5.5. Recovery exchangers cascade




     A recovery exchanger generates steam or hot water on one of the specified networks of the plant, by
     exchanging heat with the smokes leaving the post-combustion boiler (failing this, directly the fuel
     turbine or thermal engine). These exchangers are supposed of UA type, i.e. the heat exchange area
     and the heat exchange total coefficient are supposed perfectly known (see § 5.5.2).




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           5.5.1. Design - Constraints - Operation.

     For the description of an exchanger, the "Design" tab allows to define its name, the source of the
     smokes, the deaerator that provides the cold stream at the exchanger input and the network on
     which the steam is produced (or hot water, according to the selected network). U and A coefficients
     (see § 5.5.2) must also be indicated at this level.




     In operation, if the exchanger is operating, it is necessary to specify a produced steam or hot water
     outlet temperature. If the selected operating mode is "manual at fixed flow rate", it is also necessary
     to impose the flowrate.




     The constraints associated to the exchanger relate to the cold stream flowrate and outlet
     temperature. The bounds to be defined by the user are free with regard to the flowrate variable, but
     the specified temperature technical interval must be included in the temperature interval defined for
     the network on which the steam (or hot water) is produced.
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           5.5.2. Recovery heat exchanger modeling

     The recovery heat exchanger is modeled by a UA heat exchanger; it means that the exchange area
     and the heat exchange coefficient are supposed to be known and constant. For the cold stream,
     deaerated water temperature and pressure are known. For the hot stream, composition, input
     temperature and smokes flowrate are perfectly controlled.

     The system of major equations to solve is presented hereafter (in the most complex case):

     Section Water of the heat exchanger ( A1 )

                     Q1 = mf Cp f1 ∆Tf = mf Cpf (Tf e − Tf 1 )
                     Q1 = UA1 ∆Tml1
                     Q1 = meau Cp eau ∆Teau = meau Cp eau (TSAT − Teeau )

     In A1 area of the heat exchanger, water reaches its saturation level, smoke are cooled until Tf 1 and
     exchanged power is equal to Q1 .

     Variables are : Q1, A 1 , Tf 1 and the water flowrate meau


     Section phase change A2

                     Q2 = mf Cp f 2 ∆Tf 2 = mf Cpf 2 (Tf 1 − Tf 2 )
                     Q2 = UA2 ∆Tml 2
                     Q2 = meau ∆H VAP

     On A2 section of the heat exchanger, water is vaporized. Variables are then: Q2 , A 2 , Tf 2


     Section steam superheating A3

                     Q3 = mf Cp f 3 ∆Tf 3 = mf Cpf 3 (Tf 2 − Tf s )
                     Q3 = UA3 ∆Tml 3
                     Q2 = meau CpVAP ∆H VAP + meau CpVAP (Ts eau − TSAT )

     Variables are Q3 , A 3 , Tf s in A3 section, which corresponds to the superheating of the generated
     flowrate.


     Link equations are as follows :

                     Q1 + Q2 + Q3 = Qech = Exchanged _ power

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                       A1 + A2 + A3 = A. = Defined _ exchange _ area
     All in all, the resolution of this system allows to obtain as main results:
             The input water flowrate: meau
             Exchanged power: Qech
             Smokes output temperature : Tf s

     The global heat exchanger is thus considered in three sections, the first being used to heat water
     until its saturation temperature, the second characterizing the vaporization phase and the third
     section being used for steam superheating.

     Note: the same heat exchange coefficient U is considered in the three sections of the heat
     exchanger. Theses three sections are present only if the generated fluid is superheated steam. For
     saturated steam, two sections are sufficient and only one section (the first) is necessary if heat
     exchanger produces hot water.




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                                         Ariane                          Fitting methods
      _______________________________________________________________________________




                CHAPTER 5: FITTING METHODS TO SET UNIT
                      OPERATIONS YIELD CURVE

                                                              CONTENTS

     1. Boilers fitting methods.....................................................................................................................2
         1.1. Electric Boiler fitting method...................................................................................................2
         1.2. Mono-fuel boiler fitting method...............................................................................................3
         1.3. Bi-fuel boiler fitting method ....................................................................................................4
     2. Turbines yield curve fitting methods ...............................................................................................6
         2.1. Turbo-alternator fitting method................................................................................................6
         2.2. Sidestream turbine fitting method ............................................................................................7
         2.3. Condensing turbine fitting method...........................................................................................8
     3. Cogeneration unit operations fitting methods..................................................................................9
         3.1. Fuel turbine fitting method.......................................................................................................9
         3.2. Thermal engine fitting method ...............................................................................................11




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     1. Presentation

     Many unit operations use yield curves or simply correlations to characterize some variable
     evolution in the model. In practice, it proves sometimes to be difficult to obtain the exact value of
     the various coefficients used in ARIANETM software from manufacturers or from power plant
     operating staff.

     For this reason, each unit operation requiring the definition of a yield curve has been equipped with

     a specific yield curve fitting method, accessible from the     button in the "Design" unit operation
     tab. This method makes it possible to determine yield curve coefficients value starting from
     experimental data. Obviously, experimental data relevance is a necessary success condition.

     This chapter is dedicated to the description of the various yield curve fitting methods available.


     1. Boilers fitting methods

     In the electric boiler simplest case, the selected model makes the assumption of a constant yield. On
     the other hand, for the "fuel(s) boilers", the boiler yield depends, with a quadratic function
     characterization, on the boiler "energy load" (enthalpy).


        1.1. Electric Boiler fitting method

     The yield curve fitting method aims to provide an average value of experimental yields, observed
     for a set of experimental points. In addition to the average yield (which will be taken into account in
     the model after validation by the user), the method also provides minimum and maximum values
     that have been observed during experimental data treatment. The user can thus appreciate yield
     dispersion according to the defined experimental data.

     As shown in the window hereafter, the electric boiler yield curve fitting method requires, for each
     experimental point, the following data:
            Input water pressure and temperature;
            Output stream pressure and temperature (steam or hot water, depending on the type of
            boiler);
            Boiler output flowrate (no waste flowrate consideration in the fitting method);
            Electric power consumption.




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     For each provided experimental point, the method evaluates an experimental yield and then
     calculates the yield average, and also the minimum and maximum values.

     A file management system, under the "Data set" heading, allows to save experimental data for a
     later use. Lastly, an "Edition" menu allows to access some management facilities (for experimental
     data modifications).


        1.2. Mono-fuel boiler fitting method

     In the case of the mono-fuel boiler, the quadratic model retained to express the yield is shown
     hereafter:
                                          Rdt = A. W² + B.w + C

     With:          Rdt            : Boiler yield;
                    W              : Boiler load (kW); it represents energy quantity to turn the input
                                     water into output stream (hot water or steam);
                    A, B, C        : Yield curve coefficients.

     The yield curve is also depending on temperature and air excess, and for this reason, it is defined for
     a given reference point (input air temperature and air excess) which has to be set by the user. The
     window hereafter presents the window of the mono-fuel boiler yield curve fitting method. The
     following experimental data have to be defined:
            Type and flowrate of fuel (a button gives a direct access to the fuels defined in the list of
            utilities, to load automatically the corresponding properties);
            Operating conditions (in terms of input air temperature and air excess);
            Input water temperature and pressure;
            Output stream (steam or hot water) temperature and pressure;
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            Boiler load (mass output flowrate);
            Fuel consumption.

     Mono-fuel fitting method window is shown hereafter:




     The method calculates the boiler effective yield (for each experimental point) and then, using a
     minimization routine, allows to identify A, B and C coefficients which enable to describe the yield
     curve, according to the boiler energetic load (expressed in kW).

     Average, minimum and maximum yields make it possible to appreciate yield sensitivity, giving a
     good idea of the relevance (or not) of using a quadratic modeling function.



        1.3. Bi-fuel boiler fitting method

     The principle is very similar to the one presented for mono-fuel boiler, the main difference is that
     two fuels are simultaneously consumed, two fuel flowrates thus have to be defined.

     The window of a bi-fuel boiler yield curve fitting method is presented hereafter.




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     2. Turbines yield curve fitting methods

     These unit operations produce electricity by turbine action. Yield curve fitting methods have been
     developed to be able to take into account desuperheating or condensation inside the turbine.

     Yield modeling formulation of a turbine is presented hereafter:

     Rdt = A.P² + B.P + C

     With          Rdt            : Yield of the turbine;
                   P              : Power produced by turbine action in kW;
                   A, B, C        : Coefficients of the yield curve.

     Two possibilities are offered to reach turbine yield:
           Focusing on input conditions, output pressure and produced power;
           Focusing on input and output steam characteristics.


        2.1. Turbo-alternator fitting method

     The window of the turbo-alternator (or any unit operation with only one turbine) yield curve fitting
     method is presented hereafter.




     It is possible to take into account de-superheating effects when the yield curve fitting method
     focuses on the turbine input/output steam conditions, using experimental conditions of the de-
     superheating (de-superheating water temperature and flowrate).
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     As presented previously, the method includes a file management system for experimental data
     saving and an editing system to ease data acquisition.

     In terms of results, the minimization method provides the A, B and C coefficients and also average,
     minimum and maximum observed values.


        2.2. Sidestream turbine fitting method

     The problem is almost the same for a sidestream turbine, differences are as follows:
            Two successive turbines must be characterized;
            A sidestream ratio has to be defined;
            The total provided power (for both turbines) must be defined.

     For the first turbine (sidestream turbine), the user has to define the input/output steam conditions
     (pressure, temperature, flowrate). For the second one, it is possible to choose between the two
     previously defined methods (input/output steam conditions or produced power).

     The window hereafter presents the graphical interface of a sidestream turbine yield curve fitting
     method.




     Note: the method remains valid in case of exhaust stream condensation.




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        2.3. Condensing turbine fitting method

     For a condensing turbine, a single yield curve is supposed to represent all parallel turbines, whose
     output pressures are supposed to follow a geometrical deflation (see unit operation characterization
     at Chapter 4).

     The turbine maximum power is obtained, on the basis of an isentropic principle, as the sum of each
     turbine produced power, taking into account their respective real conditions of use (output pressure
     especially). The condensing turbine total produced power divided by the theoretical power provides,
     for each given operating point, an experimental yield. A minimization method, considering turbine
     yield as a quadratic function of produced power, allows to obtain the required A, B and C
     coefficients.

     The window hereafter presents the graphical interface of a condensing turbine yield curve fitting
     method.




     Average, minimum and maximum values are also proposed to check the relevance of a quadratic
     modeling formulation to characterize the turbine yield as a function of the global produced power.




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     3. Cogeneration unit operations fitting methods

     Two unit operations are concerned by a modeling curve:
           Fuel turbine (also called gas turbine);
           Thermal engine.

     For the fuel turbine, the modeling is quite complex as it covers simultaneously compressor yield,
     thermal losses and turbine electric yield (smokes expansion).

     For the thermal engine, only thermal losses have to be characterized.


        3.1. Fuel turbine fitting method

     Three yield curves have to be simultaneously defined. This is the reason why this unit operation is
     known as the most difficult to fit.

     The three yield curves are described hereafter. The first one concerns air compressor: minimum
     power Wmin is the electrical power that would be consumed during a real isentropic process. The
     ratio between this minimum power and real electrical power that is needed characterizes
     compressor isentropic yield. This yield is then modeled as a quadratic function of Wmin:

                                       Rdt _ c = a1.W min ² + b1.W min + c1

     The second curve is dedicated to the modeling of a combustion chamber thermal losses. Tadia
     represents the adiabatic temperature and we assume that Thigh (highest temperature) depends on a
     quadratic way on the adiabatic temperature as shown in the following formulation :

                                       Thaute = a 2.Tadia ² + b 2.Tadia + c 2

     Temperatures are considered in Kelvin. It should be noted that if only one experimental point is
     provided, b2 parameter will be set, instead of c2. It avoids to consider a constant high temperature
     in the combustion chamber whatever admission conditions (air, fuel).


     Finally, the third yield curve is identical to those observed for turbines:

                                       Rdt _ t = a 3.Wreel² + b3.Wreel + c3

     Calculation method

     Burning conditions being supposed to be known (high temperature, combustion chamber pressure,
     smokes flowrate) as well as fuel turbine output smokes temperature and pressure, it is possible to
     calculate the turbine yield curve parameters and, for each experimental point, to determine the
     produced electric power.



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            Data needed for turbine coefficients calculation:

                           Smokes high temperature;
                           Combustion chamber pressure;
                           Smokes flowrate;
                           Fuel turbine exhaust pressure;
                           Post turbine action smokes temperature.

     With turbine action produced power, knowing also the fuel turbine electrical balance, it is possible
     to calculate air compressor electric consumption and thus, to deduce its yield curve coefficients,
     from air excess, air input temperature and compressor exhaust pressure (combustion chamber
     pressure).

            Data to evaluate air compressor yield curve coefficients:
                          Fuel turbine electrical balance;
                          Fuel flowrate;
                          Air excess;
                          Air temperature.

     Finally, taking into account a possible water injection in the combustion chamber, adiabatic
     temperature can be calculated and then, the parameters to characterize smokes high temperature.

            Needed data for high temperature curve fitting:
                          Complete fuel description (LHV, C/H ratio, sulfur content..., plus molar
                          weight if flowrate is expressed in Nm3/h);
                          Deaerated water injection ratio, in combustion chamber (in % of fuel
                          flowrate);
                          Deaerated water temperature if previous ratio is not equal to zero.

     The window hereafter presents the graphical interface of a fuel turbine yield curve fitting method is
     presented hereafter.




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        3.2. Thermal engine fitting method

     Thermal engine characterization only concerns the high temperature concept. Required data to fit
     this unit operation are then the following:
             Input air temperature;
             Air excess;
             Combustion pressure;
             Smokes temperature ( High temperature);
             Fuel complete description (LHV, sulfur content, …plus molar weight possibly).

     As we only focus on high temperature (to be compared to adiabatic temperature), the fuel flowrate
     and produced power are not necessary to fit the thermal engine curve coefficients.

     The window hereafter presents the graphical interface of a thermal engine yield curve fitting
     method.




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                                        Ariane                                 Utilities
      _______________________________________________________________________________




                                                 CHAPTER 6: UTILITIES

                                                                  CONTENTS

     1. Demineralized water ........................................................................................................................1
     2. Electricity .........................................................................................................................................2
     3. Fuels .................................................................................................................................................4




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     1. General description

     In ARIANE™ software, utilities framework allows description of resources shared by all power
     plant unit operations. A given utility is defined by a purchase price, possibly by specific
     characteristics of use (fuels calorific value for example) and/or supplying constraints. These
     resources break up into three distinct concepts:
                 Demineralized water;
                 Electricity (called on electric network);
                 Fuels.

     To describe a given utility, use the "Utilities" menu:




     1. Demineralized water

     Demineralized water is the power plant water source. This utility is only consumed by one unit
     operation: the de-aerator .
     This utility minimum description is the purchase price (in euros/ton unit). In an optional way, it is
     possible (using the dedicated check box) to also specify supplying constraints (in ton/hour unit).

                 Only one source of demineralized water is considered in the software (only one price
                 and the associated supplying constraints). Nevertheless, for a greater flexibility, input
                 water temperature can be defined for each de-aerator.
      Caution




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     2. Electricity

     Electricity described at the utilities level is the electricity consumed by some power plant unit
     operations (electric boilers, electric pumps, auxiliaries). This utility is at least defined by a price
     purchase (in $/kWh).

     ARIANE™ makes it possible to calculate the network electric call which will have to be done. This
     call is the difference between electric consumption and electric internal production.

     A possible cogeneration contract can also be described but it is not taken into account in the
     network electric call calculation, resold electricity being the subject of a specific contract (see fuel
     turbine description).

     Electrical network need is thus defined by:

            Units consumption + Electric boilers consumption – Internal production.


     Electricity constraints description
     In an optional way, it is possible to define supplying constraints (mini/maxi) on electric network
     call, as exposed in the figure hereafter:




     These constraints will only be evaluated in simulation and necessarily respected in optimization
     mode (constraints are taken into account in optimization calculation mode).




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     Financial penalties
     If no more specification is defined, electricity purchase price is supposed to be constant throughout
     calculation (simulation or optimization). A specific "allows constraints violation" check box makes
     it possible not to respect electricity supplying constraints, with financial penalties to be described as
     follows:




     In the previous example,
              Pmin is the minimum power call, fixed at 200 kW;
              Pmax is the maximum power call, fixed at 500 kW;
              Pm arg is the electricity marginal purchase price, defined at 0.1 €/kWh.

     Supplying constraints violation is allowed with the following consequences:
            PENB , penalty coefficient when minimum power constraint is not respected, is fixed at 0.02
                   €/kWh;
             PENH , penalty coefficient when maximum power constraint is not respected, is fixed at
                   0.03 €/kWh.


     Electric cost is then calculated as follows:

             * If electric call ∈ [Pmin Pmax ]
                             Electric cost = P . Pm arg

             * If electric call > Pmax
                              Cost electric = P . Pm arg + PENH . [P − Pmax ]

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             * If electric call < Pmin
                              Electric cost = P . Pm arg + PENB . [Pmin − P ]
     Electric consumption
             power plant electrical need is calculated as the sum of each unit call. To define electrical
             consumption of the various started units, use the "Constraints" menu, then the "Electric
             demand" heading.




            The following table appears, which allows to define electric consumption of each started
            unit, the total (calculated at the bottom of the window) is the power plant electrical
            minimum consumption.




            power plant specific needs, calculated according to the electric boilers or pumps
            consumption.

     Electric production
     This is the electricity produced by all the power plant turbines.
     3. Fuels

     ARIANE™ can simulate a plant using simultaneously up to nine fuels (fuel oil, fuel-gas, hydrogen,
     coal, natural gas, four "user" fuels to represent specific fuels such as wood, flora wastes or any other
     fuel).


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     The reference unit of a fuel may be the mass (fuel oil, fuel gas, coal), the normal volume (natural
     gas, hydrogen) or can be chosen (user fuel) by the user. If the reference unit is the mass, the fuel is
     described by a current purchase price (in Euros per ton) and a lower calorific value (in thermie per
     ton). On the other hand, if the reference unit is the normal volume, the purchase price is expressed
     in Euros/Nm3 (or in Euros/kWh in case of natural gas) and the calorific value is defined in kWh per
     Nm3.

     Fuels are described as presented hereafter:
            The name and the units system are specified, except for user fuel,
            The current price is simply fuel purchase price,
            Supplying constraints may be defined,
            In case of fuel in “gas state”, gas composition allows to define the CO2, H2O and inert gas
            percentage.

     For each fuel, input characteristic data are the following :
            Lower calorific value,
            Sulphur content (weight percentage),
            Molar weight,
            Carbon / Hydrogen ratio (except for Hydrogen)
            Storage temperature and pressure,
            Fuel purity,
            Specific heat.

     Input data are checked, to ensure a global coherence : the sum of fuel purity, sulphur contents and
     possibly H2O, CO2 and inert contents must not exceed 100 %.




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                                        Ariane                            Fuel Networks
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                                     CHAPTER 7: FUEL NETWORKS

                                                               CONTENTS




     1. Fuel networks...................................................................................................................................1
     2. Fuel feeds concept............................................................................................................................3
     3. Fuel valves concept ..........................................................................................................................5




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     Fuels described in the previous chapter are directly usable in any unit operation which consume
     them. Nevertheless, some real aspects of power plant onsite fuel management cannot be taken into
     account by this representation. As an example, the previous formalism cannot represent the constant
     production of a given fuel (back from units) that has to be consumed in priority, or fuel mixtures
     before entering boilers.

     The fuels management modeling requires the description of real fuel networks. They have been
     implemented in the software, as presented hereafter:
           Fuel networks,
           Fuel feeds concept,
           Fuel valves concept.


     1. Fuel networks


     These networks are overall presented as steam or hot water networks, as shown in the figure
     hereafter.

     A general table allows to define a name for the created fuel network, presents all fuels feeding the
     network (fuel feeds, see next point), and details all connected unit operations (boilers, fuel turbines,
     thermal engines…).




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     The "Operation" tab allows to define a total consumption (total units consumption of this fuel, in
     furnaces for example ). This value is the fuel network required production.




     A torch can be defined on each fuel network. The torch has to be set "On" if no "Fuel valve" is
     defined. It can be set "Off" as the fuel valve offers a degree of freedom.

     In Simulation mode, the fuel network degree of freedom is ensured by the torch or one and only one
     fuel valve. There is thus one and only one possible degree of freedom in this calculation mode.

     In Optimisation mode, there must be at least one degree of freedom.

     Fuel networks mixing rules

     The mixing of different fuels on a given network leads to a "fuel mixture", with its own
     characteristics (low heat value, price, molar weight...).

     To evaluate these properties, simples rules are used: each property is thus evaluated by the rule
     presented hereafter:
                                                          N

                                                          ∑
                                                          j=1
                                                                     Pj .Q j
                                             Property =       N

                                                           ∑  j =1
                                                                      Qj

     with:              J          : Fuel feed number J
                        Pj         : Property value for fuel J
                        Qj         : Flowrate of fuel J
                        Property   : Property value assigned to the resulting mixture.




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     2. Fuel feeds concept




     Each fuel defined in the utilities list can be defined as a "fuel feed". It then feeds a fuel network.

     The "Design" tab allows to select a fuel in the utilities list, to rename it within the defined fuel feed
     and finally to connect it to a chosen fuel network.




     The "Constraints" tab allows to set admission bounds on this fuel (which can be different from
     those eventually defined in the utilities framework).




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     Finally, the "Operation" tab allows to define the fuel feed operating mode among the three
     following ones:
             Stopped: the feed is ignored during calculation,
             Inevitable flowrate : the defined flowrate will remain constant during calculation,
             Automatic with flowrate initialisation: the optimisation run will adjust the fuel feed required
             flowrate but initialisation is given by user.




     Fuel feeds (and therefore fuel networks and fuel valves) are defined in mass unit. Fuel networks do
     not yet support volumic data.




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     3. Fuel valves concept


     This unit operation allows to represent excesses discharge from a network towards another one.
     Integration of this concept in the software allows to simulate inter-connected fuel networks, with a
     model rather similar to the steam network.

     The fuel valve is described by the three tabs presented hereafter:

            The "Design" tab allows to name the unit operation and, above all, to define the input/output
            connected fuel networks.




            The "Constraints" tab allows to define flowrate constraints




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            Finally, the "Operation" tab makes it possible to impose the operating mode (stopped,
            manual with fixed flowrate, automatic)




     Note: like for fuel feed, the automatic mode implies a flowrate initialisation by the user.




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