Plant Performance Calculation by hbi59934

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									

                                               MAXIMIZING ECONOMIC AND ENVIRONMENTAL
                                               PERFORMANCE OF EXISTING COAL-FIRED ASSETS

                                                        Authors: Pat BARTLEY, Alstom
                                                       Jean-Claude FOUCHER, Alstom
                                                         Rolf HESTERMANN, Alstom
                                                            Bob HILTON, Alstom
                                                            Bill KEEGAN, Alstom
                                                           Don STEPHEN, Alstom



Abstract
In a time where the margin between available electrical supply versus demand is shrinking,
many utilities are faced with the difficult task of how best to address this problem. One option
is to take the greenfield approach by installing new generating capacity that takes
advantage of the latest advances in high efficiency, environmentally friendly coal firing
technologies. This, however, can be a costly process that can take several years before the
plant is in operation.

In recent years, Alstom has come to realize that existing coal-fired assets have in many cases
hidden capacity. This largely results from the conservative nature of their design, but also from
advances in technology. By taking advantage of these hidden reserves, a unit can often
obtain a notable increase in output. In cases where new air pollution control equipment is
being installed, parasitic power losses can be offset so that the impact on net generating
output is minimized.

Alstom’s Optimized Plant Retrofit (OPR) process is a proven method to enhance unit output
that has been successfully implemented in the marketplace. OPRs are supported by Alstom’s
comprehensive portfolio of available technologies and a proven capability to integrate
retrofit opportunities that encompass innovative solutions for a variety of plant components
such as coal mills, boiler, air pollution control equipment, turbogenerator, etc.

To exploit the full potential of existing equipment, it is not adequate to optimize components
on an individual basis. Rather, it is necessary to take a systemic and holistic approach and
look at the complex interaction between key components and assess how best to integrate
the disparate potentials into a coherent synergistic and integrated solution. This is of specific
importance with regard to CO2 emissions where total plant performance is the determining
factor. By teaming with utility representatives, Alstom’s technical experts can collectively
identify one or more solutions for enhancing net output, with a return on investment that is
significantly better than greenfield construction.

This paper introduces the OPR concept in detail on all potential aspects: boiler,
turbogenerator, emission control equipment, site construction, etc. Case studies are

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presented and future perspectives offered, in particular in view of retrofitting existing assets
towards a CO2-ready status.




4579d369-0416-482b-b04b-808d96836441.doc                                               
                                                 Maximizing Economic and Environmental
                                                 Performance of Existing Coal-Fired Assets
                                                                            3




  1 - Introduction
  Various drivers are now pushing the                   identification and matching of the     used for trading within the frame of
  power generation industry to                          maximum capability of the boiler       emission trading schemes such as.
  improve performance of the coal-                      and turbogenerator combined            in Europe. This is only the beginning
  fired power generation assets.                        with ensuring that the balance of      of a major shift in power
                                                        plant systems and equipment have       generation. For example, for a 400
  The primary driver in today’s market                  sufficient capability to support the   MWe coal fired power station, a 3%
  place results from the increasingly                   boiler – turbine island output         efficiency improvement avoids
  competitive power generation                          capability.                            approximately 250 000 tonnes of
  market : maximize revenues while                                                             CO2 emission per year.
  minimizing costs: this leads to                       The third driver is related to
  improvement of heat                                   emissions. For example, the            The authors' company having
  rate/efficiency/output.                               addition of back-end flue gas          boiler, turbine, pollution control
                                                        treatment systems will increase the    equipment and balance of plant
  Another route to maximize                             parasitic power losses in the plant.   expertise, have actively developed
  revenues is to adapt base load-                       It may be possible to offset these     such integrated optimization
  designed power station to load                        parasitic power losses through         processes over the past years.
  follow, thus taking advantage of                      identification and optimization of
  "golden hours" operation, without                     the boiler – turbogenerator island.    This paper comprehensively details
  suffering the cost of operating the                                                          the process followed in developing
  installation at partial loads for                     Another emission-related driver is     integrated projects starting with the
  which they were not initially                         the emergence of the CO2-              thermal optimization.
  optimized.                                            constrained economy, where
  The second driver is maximizing the                   avoided CO2 emissions can be
  potential of existing assets through



  2 - Thermal Optimization Process

                                                        equipment from the fuel system to      of Optimized Plant Retrofit (OPR)
  General                                               the generator, Alstom has              aims at maximizing the
  Methodology                                           developed tools for the                performance of existing plants,
                                                        development of such activities         either in terms of power output or
                                                        aiming at optimizing the plant:        heat rate.
  There are various approaches to                       Alstom’s ECORAM tool (ECOnomic
  assess an existing power station,                     Reliability, Availability and
  and identify ways of improvement.                                                            An ECORAM analysis, jointly
                                                        Maintainability) focuses on RAM
  Thanks to its capabilities covering                                                          performed with the Customer,
                                                        aspects to maximize overall plant
  the full range of power station                                                              identifies potential improvement for
                                                        economics, while Alstom’s concept
                                                                                               operation and maintenance of the
                                      The ECORAM concept                                       power station. It is a total plant
                                                                                               evaluation package combining
                                                                                               technical and economical
   Balance of plant                              • Power input increase
                                                                                               evaluation of operational and
Turbine / generator                Design        • More flexible operation                     maintenance costs and evaluation
                  Boiler          Operation Goal • Increase of availability                    of potential reductions.
              Electrical         Maintenance     • Reduction of maintenance cost
      Environmental                              • Less emissions                              This is done by analyzing the whole
                                                                                               power plant by design, operation
                      - systematic investigation of the plant -                                and maintenance. The results can

  4579d369-0416-482b-b04b-808d96836441.doc                                                                               
                                                    Maximizing Economic and Environmental
                                                    Performance of Existing Coal-Fired Assets
                                                                                            4


be new investment plans and/or                                                                             to accurately reflect either the
retrofit programs for the plant. For
                                                                   General                                 original design performance of an
example, an ECORAM investigation                                   Considerations                          existing cycle or, more usefully, the
complemented the Optimized                                                                                 performance of an existing cycle
Plant Retrofit optimization work at                                                                        as determined from recent test
ARNOT Power Station in the                                         The Alstom proprietary Turbine          data.
Republic of South Africa.                                          Cycle Program (ALPRO) enables
                                                                   thermodynamic performance               Such a model can then be run in
                                                                   prediction and analysis of any          ―off design mode‖ to predict how
Thermal Optimization                                               steam turbine cycle. The core of        the cycle will perform under
Process                                                            the system is a robust simultaneous     different operating conditions
                                                                   solver for non-linear equations that,   and/or with some components
                                                                   in combination with generic             (e.g. steam turbines) replaced by
The Thermal Optimization Process                                   interfaces for data exchange,
— illustrated below — is a key                                                                             modern retrofitted components.
                                                                   provides an open tool meeting           Using the ALPRO system in this
element of any effort aiming at                                    current and future needs.
maximizing performance and can                                                                             manner permits rapid optimization
be implemented without a full                                                                              of an overall cycle retrofit proposal.
                                                                   The ALPRO program includes
ECORAM Evaluation if some of the                                   calculation elements for steam
key drivers for thermal optimization
of the power plant are already
                                                                   turbines, condensers, feed-heaters,     Turbine retrofit
                                                                   motors, pumps, generators and
identified.                                                        other cycle components. Using a
                                                                   graphical user interface the various    High Pressure Turbine

                                                                                                           The main driver for retrofitting the
                                                                                                           HP turbine is to increase the
                              Design
     Design Boiler
     geometry and
                             original
                                                  Optimization
                                                    criteria &                                             efficiency of the section in order to
                                                                           Turbine specs :
      equipment            turbine heat
                             balance
                                                    constraints:           • inlet flow, temp, press       increase overall power output. This
                                                  • steam flow
                                                  • Q fired
                                                                           • Ffwt                          improvement may also be
                                                                           • Reheat P
                                                  • Emissions              Boiler specs :                  combined with an increase in main
       Test Data as per turbine and               • Others…                • SH/ RH surfaces
            boiler requirements
                                                                           • Design tilts                  steam flow to achieve a more
                                                                           • SH/ RH sprays                 significant increase in overall power
                                                                           • RH press. drop
                      Proposed turbine design                                                              output. Other aspects of retrofitting
                                                                             Turbine & boiler              HP turbine cylinders might be to
        Proposed boiler perf.                                                 geometry fixed
           Modifications.              Customer input                                                      eliminate the risk of Solid Particle
            Generator &                                                                                    Erosion by applying state-of-the-art
                                               Balance of plant
            transformer                          information                                               blading technology or to change
            information                                                    Off-design operation :
                                                                           • Mill configuration            the mode of operation by going
               Preliminary Assessment Followed by
                       Joint project review
                                                                           • Heaters out of service        from partial arc to full arc.
                                                                           • Boiler fouling
          Turbine elastic (variable swallowing capacity)                   • Condenser pressure
                    boiler surfaces not fixed                                changes
                                                                           • Part load operation
                                                                                                           The latter is especially of interest for
                                                                                                           plants that are base loaded. By
                                                                                                           changing from partial to full arc an
                        The Iterative Thermal Optimizing Process                                           additional benefit in heat rate on
                                                                                                           the order of 0.1 to 0.2% can be
                                                                                                           achieved. For most of the suitable
This optimization process is a                                     calculation elements can be             units, this conversion can be done
cooperative and jointly performed                                  connected in any required               without any costly investments if
effort with the Customer. The                                      configuration and customized to         done at the time of the retrofit.
thermal optimization process                                       allow accurate modeling of any          Conversion to full arc operation
covers the turbine, the boiler and                                 steam turbine cycle.                    might also be of interest for cycling
the balance of plant, each of                                                                              units if the unit can be operated in
those being addressed hereafter in                                 A special strength of the ALPRO         a sliding pressure mode and the
detail.                                                            system lies in its design and off-      load range is above approximately
                                                                   design management capabilities.         85% of Maximum Continuous Rating
                                                                   An ALPRO model can be created           (MCR).
                                                                   in ―design mode‖ and calibrated

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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                            5


When increasing steam flow the re-                    into the reheater. It is this additional   sprays, it is not unusual for the spray
design of the flow-passing capacity                   heat added (in the region of 3-4%          quantity to be reduced in order to
of the HP turbine in conjunction                      over the existing reheater duty)           maintain hot reheat temperature
with a careful boiler analysis can                    that contributes to the power              after retrofitting the HP turbine.
also be used to minimize carry-over                   advantage given by HP retrofitting.
and thus improve the performance                      The overall turbine heat rate is also      The effect on the turbine cycle of
and reliability of the plant. The                     improved due to the higher HP              reheater sprays taken from the
matching of turbine throttle                          section efficiency but the heat rate       boiler feed pump discharge is to
pressure and boiler superheater                       improvement is usually limited to          increase the flow through the IP
output pressure with the new steam                    about 60% of power increase.               and LP turbines with the main
flow conditions may also result in                                                               steam flow remaining unaffected.
benefits such as avoiding safety                      The reduction of internal turbine          The increase in power is achieved
valve problems and system                             leakages, particularly in the case of      at a worse heat rate and boiler
pressure drop issues.                                 combined HP-IP turbines                    firing is increased when compared
                                                      contributes significantly to the           to a plant designed for zero spray.
Also, whether the pressure is still                   overall benefit of retrofitting. The       Nevertheless plant owners often
within acceptable limits at the                       reduction of leakages is possible by       are worried about reducing the
crossover from the Intermediate                       improving and simplifying both the         spray quantity due to the
Pressure (IP) to Low Pressure (LP)                    steam path and inlet                       associated reduction in power.
turbine or at the extraction pipes                    arrangements. This generally leads
and the feedwater heaters needs                       to an increase in reheater flow thus
to be evaluated.                                      increasing the extra reheater
                                                                                                 Intermediate Pressure
                                                      thermal duty still further. In some        Turbine
The impacts of increased steam                        cases the reheater flow has been
flow and/or changes in main                           increased by 2%.                           When compared against the
steam, cold reheat or hot reheat                                                                 economics of modifying the HP
steam pressures on the high energy                    If reheater spray water is currently       turbine, an IP turbine retrofit is
piping systems also need to be                        being used then the amount of              usually not as attractive with
considered to ensure that critical                    spray required, assuming no other          respect to the ratio of investment
design temperatures or pressures                      operational or plant changes, will         versus power gain. However,
are not exceeded.                                     reduce. The reduction in reheat            recent activity indicates that
                                                      spray water will reduce power but          modification of the IP turbine is
Consequence on boiler reheater                        does improve the heat rate.                being considered more often.
operation.
                                                      The reduced cold reheat                    An important option when
Reheat temperature is a very                          temperature has a small second             modifying the IP is the flow passing
important condition both from a                       order effect on the quantity of            capacity. An increase in the flow
heat rate and power                                   extraction steam taken for                 passing capacity will for example,
consideration. It is worth                            feedwater heating from this point.         reduce the IP inlet pressure and
mentioning that a reduction in hot                    Due to the reduction in                    therefore the HP exhaust pressure.
reheat temperature affects power                      temperature, the extraction steam
considerably more than the same                       quantity increases slightly which          In the case where the final
reduction in main steam                               leads to a slight corresponding            feedwater heating is being tapped
temperature.                                          reduction in cold reheat pressure          from cold reheat, the final
                                                      and final feedwater temperature (if        feedwater temperature can be
Increasing the HP cylinder                            the highest pressure heater is fed         adjusted. Changes in the final
efficiency result in a decrease of                    from cold reheat).                         feedwater temperature affect the
the exhaust temperature (cold                                                                    heat input to the boiler and
reheat). The reduction is obviously                   In any case, a comprehensive               significantly affect the power and
dependant on the efficiency levels                    boiler analysis is required in order to    heat rate gain of the turbine cycle.
both before and after the retrofit                    quantify the extent of necessary           The design of the IP turbine can
but is generally in the region 8°C to                 changes. In many situations, the           therefore be used to optimize the
11°C (15° to 20° F). It is assumed                    analysis highlights other areas of         cycle for either power or for heat
that in most retrofit applications the                deficiency or shows modifications          rate.
hot reheat temperature will be                        to other areas that may help
maintained at design levels, which                    reheater performance. In the case
requires extra heat to be added                       of a plant operating with reheat
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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                           6


Low Pressure Turbine                                  size of the valves will have to be        CR value should be maintained in
                                                      altered.                                  order for a waterwall circuit to
                                                                                                operate in a safe zone for a given
Modern LP turbine retrofit designs                    Similar comments apply to safety          drum pressure and circuit fluid mass
offer significant efficiency                          valves located on the waterwall           velocity (flow rate per unit area). Of
improvements versus existing                          outlet boiler throttle links and          course, this condition is very boiler
designs due to the application of                     superheater outlet headers or links       specific and is not always a main
state-of-the-art Computational                        on supercritical pressure combined        concern.
Fluid Dynamics (CFD) modeling in                      circulation boilers. Note that if the
blade design. These models take                       new operating pressure of any             Water purity: The water purity and
into account the complex, three-                      safety valve is within 3% of the          carry over is an important
dimensional behavior of the steam                     closure pressure of that valve, then      consideration from both a boiler
flow. Longer blades (up to 114 mm                     excessive valve leakage and               and turbine viewpoint. If the drum
(45 inches) in 60 Hz, corresponding                   maintenance can occur. To                 pressure is lowered, the carry over is
to 137 mm (54 inches) in 50 Hz                        eliminate this condition, the boiler      generally reduced. In rare cases
designs reduce leaving losses,                        superheater or reheater sections, or      modifications to drum internals may
further improving efficiency. LP                      the steam leads can be                    be required.
turbines provide a significant                        redesigned to reduce steam side
portion of the overall power                          pressure drop. The best solution          Increased firing: The issues
generated — typically about 45%                       however, is to design the HP turbine      associated with increased firing
for a 500 MWe unit in U.S.A.                          for a lower throttle pressure.            cover boiler furnace, pressure parts,
installations. Therefore, small                                                                 burners, pulverizers, air supply,
efficiency increases give significant                 The system pressure of the boiler         emissions, etc. Evaluating the firing
overall improvements.                                 turbine complex needs to be               increases in incremental amounts
                                                      checked if steam flow exceeds             and reviewing the margins in each
Boiler retrofit                                       original boiler MCR. This check is
                                                      necessary to verify that the
                                                                                                of the associated equipment will
                                                                                                allow an assessment to be made of
                                                      increased steam flow and resultant        the extent and cost of
Alstom has extensive experience in                    increase in system pressure drop          modifications necessary to reach a
retrofitting/upgrading boilers of any                 does not result in the drum               particular flow. An important
technology, whether or not                            operating pressure approaching            performance goal for the boiler is
supplied by said company. Such                        the lift pressure of the low set drum     the maintaining of main steam and
retrofits cover output improvement,                   safety valve prior to the lift pressure   reheat steam temperatures after
fuel flexibility, capacity to load                    of the low set Superheater Heat           the retrofit.
swings, environmental compliance,                     exchanger (SH) safety valve. The
etc.                                                  SH safety valves should always be         In certain boiler specific cases, the
                                                      set to lift prior to the drum safety      issues of boiler efficiency, flue gas
General Considerations                                valves lifting and close after the        temperature control and firing rate
                                                      drum safety valves close to prevent       issues may collectively point out a
                                                      potential SH tube overheating due         need for review of the thermal
The following is a list of                            to lack of cooling flow. The same         performance of the economizer. In
considerations needing attention                      check is needed on the Reheater           several cases it has been found
for increasing boiler capacity:                       Heat Exchanger (RH) steam system          that upgrading the economizer is a
                                                      safety valves.                            viable solution for (i) maintaining
The steam drum safety valves on a                                                               exit flue gas conditions for flue gas
natural or controlled circulation                     Water circulation: An assessment is       cleaning equipment, (ii) lowering
boiler, the superheater outlet                        needed of the ability of drum type        boiler heat input (Qfired) rates to
header or links, and the reheater                     boilers to operate with adequate          acceptable levels, or (iii) increasing
inlet and outlet links must all be                    safety margin at the increased            project justification via
checked for relieving capacity and                    flow. The Circulation Ratio (CR),         improvements in boiler efficiency.
operating pressure based on                           defined as the mass flow ratio of         Economizer upgrades have also
design code. If the relieving                         the circulation fluid to steam            been found to lower system flue
capacity is exceeded, larger size                     leaving the circuit, and the              gas pressure drop and thus result in
valve internals may be required. If                   circulation mass flow rate are the        plant power savings adding to the
larger valve internals cannot be                      two important parameters used to          project justification.
installed, then the number or the                     measure the waterwall circulation
                                                      safety margin. A certain minimum
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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                          7


Advanced Boiler                                       superheater and reheater steam         module consist of furnace
                                                      flows, superheater and reheater        geometry and dimensions, number
Simulation Software                                   outlet steam temperature and           and location of burners in service,
                                                      pressures, economizer inlet water      burner tilt angle, and the required
One of the key tools used in boiler                   temperature and pressure,              information from previous modules.
retrofit activities is a dedicated                    reheater inlet steam temperature
advanced simulation software                          and pressure, and the required         The Upper Furnace Module is used
known as the Reheat Boiler                            information from the previous          only for conventional panel and
Performance Program (RHBP).                           modules.                               pendant type units. This module
                                                                                             calculates a heat balance in the
This Alstom proprietary tool predicts                 The Pulverizer Performance Module      upper furnace portion of the boiler,
overall boiler performance, as well                   calculates the thermal                 from the horizontal outlet located
as the performance of selected                        performance and grinding               at the arch, to the vertical outlet
boiler components. Heat balances                      capacity of the mills. Input values    plane prior to the first vertical
are performed around the boiler                       for this module are the number,        convective section. This module
envelope and individual                               size, and type of mills in service.    also calculates the direct radiation
components, in order to generate                      Additional data includes the           distribution to the vertical output
the information that is required for                  available hot air temperature, mill    plane, sidewalls, and waterwalls.
detailed component evaluation.                        outlet temperature, coal               Input values for this module consist
The computer program is structured                    grindability, and coal particle        of upper furnace geometry and
in a modular fashion and performs                     fineness, and additional               dimensions, and required
these calculations in a                               information from previous modules.     information from previous modules.
predetermined sequence.
                                                      The Net Heat Input Module              The Direct Radiation Distribution
The calculations begin with boiler                    calculates the total amount of         Module uses the direct radiation
efficiency, general data, and net                     energy present in the furnace from     calculated at the furnace
heat input modules, which are                         fuel, heated secondary air, and        horizontal outlet plane (at the
dependent on the fuel analysis,                       heated primary air (if used). In       elevation of the bottom of the
design or field test data, and the                    addition, this module accounts for     platen superheater) to calculate
turbine heat balance information.                     energy losses due to carbon,           the amount of radiation that is
The calculations then continue in                     radiation from the boiler casing       absorbed by subsequent
the same sequence as the flue gas                     and furnace bottom, and the            convective sections. Input values
through the boiler. Furnace                           latent heat of vaporization of         for this module are the tube and
performance is calculated first, and                  moisture from the fuel and from the    assembly geometry (tube spacing
is then followed by an analysis of                    moisture that is formed by the         and number of tubes across each
the convection pass components.                       combustion of hydrogen in the fuel.    assembly), for each section that
The final module is the air preheater                 The main input values are the          can absorb direct radiation.
module. The program is divided                        secondary airflow and                  Required information from previous
into nine modules that are                            temperature, primary airflow and       modules is also included in this
computed in the following                             temperature, and required              module.
sequence:                                             information from previous modules.
                                                                                             The Steam Generator Module is the
The Efficiency Module calculates                      The Furnace Outlet Temperature         largest and most complex module
the boiler losses and efficiency at a                 Module calculates the furnace          in the Reheat Boiler program. This
given operating condition. The                        outlet gas temperature and the         module calculates the heat
main input values are fuel analysis,                  furnace outlet direct radiation, at    balances for all of the convective
air preheater exit gas temperature,                   the horizontal plane located at the    sections in the boiler, beginning at
air and fuel temperatures, and                        elevation of the bottom of the         the final superheater gas inlet, and
excess air levels.                                    platen superheater. This calculation   ending at the economizer gas
                                                      is based upon Alstom boiler design     outlet. The convective sections of
The General Data Module                               standards, developed empirically       the boiler are arranged according
calculates the total heat absorbed                    from test data. When unit specific     to the way the gas flows through
by the steam, the total fuel fired by                 test data is being analyzed, this      the boiler. Boiler banks, and split (or
the boiler, and establishes the air                   module is used primarily for           dual) backpass arrangements can
and gas flow requirements for a                       comparison of actual furnace           also be solved. All boiler heat
given operating condition. The                        performance with design furnace        absorbing sections are also linked
main input values are the                             performance. Input values for this     together in the computer program,
4579d369-0416-482b-b04b-808d96836441.doc                                                                                 
                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                            8


in order that the fluid flow                          water temperatures are an                 Electrostatic Precipitator (ESP) or
sequence correctly accounts for all                   essential part of this calibration        bag house where the flue gas
of the superheater, reheater and                      process.                                  inlet conditions need to be
economizer sections.                                                                            modified to ensure compliance
                                                      Once the RHBP is calibrated, the          with emissions requirements.
This Steam Generator Module                           new steam turbine conditions can
                                                                                               Fuel firing rate – directly affects
determines the heat transfer                          be input and the redesign process
                                                                                                the size of all equipment through
characteristics for each convective                   of the boiler can begin. Of course,
                                                                                                its impact on total gas volume
section. This includes the adjusted                   this is an iterative process with the
                                                                                                and pollutant concentration.
heat transfer rates, intermediate                     steam turbine designer. Together
gas and fluid temperatures, and                       with the customer’s objectives, the      Coal sulfur content – directly
either the furnace outlet gas                         plant performance can be                  affects the sizing of the reagent
temperature at the horizontal                         optimized. In the balance of this         addition system, whether a lime
furnace outlet plane (if analyzing                    paper, when boiler resurfacing or         injection system found
test data), or the economizer outlet                  performance predictions are               predominantly in dry scrubbing,
gas temperature (if design data is                    mentioned, the Reheat Boiler              or a limestone preparation
used). Input values include tube                      Program is the main tool used to          system utilized in wet scrubbing
outside diameters, tube and                           develop the proper solution to the        systems.
assembly spacing, free gas area,                      boiler island.
known or desired fluid                                                                         Coal heating value – has some
temperatures, inlet and outlet fluid                                                            impact on equipment size.
pressures, gas touched surface gas
                                                      Emissions Control Systems
                                                                                               SO2 removal efficiency - affects
and fluid flows, and required                         Considerations                            lime or limestone preparation
information from previous modules.                                                              system size in a similar way as
                                                      Several major inputs are critical to      coal sulfur content.
The Air Preheater Module is used to                   the modeling and design of air
analyze the performance of                            pollution control systems. For           Gas flow rate – a major factor in
rotating Ljungstrom® regenerative                     scrubber projects, which are the          determining absorber sizing, as
type air preheaters, and can also                     environmental retrofits typically         this equipment is designed based
analyze tubular type air preheaters.                  having the largest plant impact,          upon volumetric considerations.
Input values include air preheater                    these factors are described below:        This impact includes sizing of
component dimensions, material                                                                  collection devices (ESPs or fabric
specifications, and required                                                                    filters). It has a lesser impact on
information from previous modules.                     Integrating the boiler-turbine          reagent preparation systems and
                                                        retrofit with possible post             for dry scrubbers, atomizer size.
                                                        combustion environmental
Test Data Used with the                                 control projects may also              Gas temperature – impacts
                                                                                                atomizer size for dry scrubber.
Reheat Boiler                                           necessitate further in-depth
                                                                                                Increases water use for wet
                                                        assessment of boiler
Performance program                                     performance with an objective           scrubber.
(RHBP)                                                  of modifying the flue gas              Excess air or air heater leakage –
                                                        boundary conditions exiting the         increases gas flow rate with
The RHBP is an important tool used                      boiler to optimize the                  impact described above.
to evaluate the present and future                      performance of the flue gas
operating conditions of the boiler. It                  emissions control systems.             Similarly, SCR systems are also
can be used to model both Alstom                                                                impacted by changes in flue gas
and non-Alstom boilers as well.                         In many cases it has been found         boundary condition changes at
When steam turbine modifications                        that boiler modifications are           the economizer flue gas outlet.
are being considered, the effects                       needed to provide the flue gas         SCR systems also have strict flue
on the boiler operation must be                         temperature required by a               gas temperature ranges in which
accurately modeled so that the full                     Selective Catalytic [NOx]               they operate that must be
benefit of the steam turbine                            Reduction system (SCR) to               considered whenever boiler
changes can be realized. To                             properly operate and achieve            changes are made.
accomplish this, current plant and                      required NOx emissions
boiler operating data is needed to                      performance. A similar situation       Optimization of the boiler –
properly calibrate the RHBP. Note                       could occur with a Flue Gas             turbine performance with the flue
that all intermediate steam and                         Desulphurization system (FGD),          gas emissions control system

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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                           9


   requirements and performance is                    A HP turbine retrofit project is often    pressure and temperatures. Cost
   a key consideration that Alstom’s                  viewed as attractive for power            benefit must be carefully weighed
   Thermal Evaluation Process                         increases of about 2% - 3% that are       as the impact downstream the
   addresses.                                         a result of efficiency gains.             boiler affects the main piping from
                                                      However, it is often possible to gain     the boiler to the HP turbine, and
                                                      a few extra percent flow without          the HP turbine itself, at least.
Boiler-Turbine                                        incurring any significant additional
Interfaces                                            cost, which can greatly boost the
                                                      return on investment.                     Generator and
The boiler-turbine interfaces of                      With respect to pressure, there are
                                                                                                Balance of Plant
specific concern are main steam                       many cases where units are unable
pressure, temperature and flow,                       to operate at the MCR boiler flow,        The following is a short list of the
cold reheat temperature and                           which usually corresponds to a 5%         more important Balance of Plant
pressure, and final feedwater                         over pressure condition. Limitations      items that may need consideration.
temperature.                                          may be related to safety valve
                                                      operation, concerns over steam            Generator : In analyzing the effect
                                                      purity or a conservative operating        of increased steam flow on the
Selection of Turbine Inlet                                                                      generator, initial considerations
                                                      procedure.
Conditions                                                                                      should be for operation at an
                                                      Increasing the main steam flow to         increased power factor or
Generally speaking, most                              the original boiler design MCR and        increased hydrogen pressure. As
optimization efforts try to maintain                  beyond needs to be considered             the power further increases,
the original design steam                             carefully and the potential impacts       cooling modifications may need to
temperature due to the high cost                      to the boiler, turbine, generator         be considered and in some
associated with either its increase                   and balance of plant evaluated. A         circumstances the generator may
or decrease. For the most part, the                   logical starting point is to review the   need to be rewound.
majority of turbine retrofits are                     current operating flow and if below
designed for the original design                      design, investigate ways to restore       The boiler feed pump turbine,
temperature.                                          it. In some cases fuel changes to         particularly if supplied with
                                                      lower rank fuels, have reduced the        extraction steam and exhausting to
At a constant flow at MCR,                            output to below original design.          the feedwater heaters (rather than
reducing the pressure causes a loss                                                             to the condenser) will need to be
of cycle efficiency and power. In                     If the main steam flow is to be           analyzed for operation at higher
the case of a 600 MWe unit,                           increased beyond the original             main steam flows. In addition to the
designing for a pressure of 165.5                     rating, the approach should focus         extra feedwater flow, the pressure
Mpa g (2400 psig) versus a pressure                   on incremental increases and at           drops in the feedwater heating
of 173.7 Mpa g (2520 psig) will result                which point a particular item of          system, the boiler and from boiler to
in a reduction of about 3 MWe                         plant will become the limiting            turbine may all increase. Very
while maintaining a constant final                    factor. It therefore involves the         often, the output of the boiler feed
feedwater temperature.                                identification of major components        pump turbine can be increased by
                                                      and balance of plant items, the           resizing of the inlet nozzles.
                                                      relationship between maximum
Considerations for                                    component output and the main             The pressure increases in non-
Increasing Main Steam                                 steam flow (which can be                  retrofit turbine cylinders and
                                                      accepted with current equipment),         corresponding increases in the
Flow
                                                      and finally the modifications             extraction pressure will increase the
                                                      needed to increase the duty.              feedwater heater shell pressure. It
A major consideration at the time                                                               may be necessary to modify the
of retrofitting is whether or not to                                                            turbine stages to reduce the
increase the main steam flow for                      Improvement of steam                      extraction pressures if the rated
the unit. Where environmental                         cycle efficiency                          levels are exceeded.
issues can be addressed, plant
owners will usually attempt to                                                                  The following table shows the
increase the main steam flow as                       This is another route to investigate
                                                      as far as the turbine is tolerant to      effects of other options that can be
much as possible.                                                                               followed. The main steam flow and
                                                      significant increases in live steam

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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                            10


inlet conditions are kept constant                    for all options.



                                                                 Current                Option A                       Option B
Cold reheat temperature                                       302°C (575°F)          294°C (562°F)                  294°C (561°F)
Hot reheat temperature                                       540°C (1004°F)          540°C (1004°F)                 540°C (1004°F)

                                                                45.6 t/hr                  45.6 t/hr                  25.6 t/hr
Reheater Spray mass flow
                                                             (100,000 lb/hr)         (100,000 lb/hr)                (56,350 lb/hr)

Boiler Total Heat input (Q fired) MWth                             1889                     1903                         1891
Power Output MWe                                                   806                       821                          817
                                                              8440 kJ/kWh             8345 kJ/kWh                    8333 kJ/kWh
Turbine Heat Rate
                                                            (7,999 Btu/kWh)         (7,910 Btu/kWh)                (7,898 Btu/kWh)

CO2 avoided (evaluation, baseline 806                           Base line              69 000 t/yr                    78 000 t/yr
MWe output, assuming 100% availability)

   Table 1: Impact of modifications of reheater surface and reheater spray flows on power output and heat rate.


For Option A, reheater surface has                    increased to that in Option A (by            stages up or down the expansion.
been increased to                                     increasing the main steam flow)              In general, the extraction pipe
accommodate the extra duty on                         the power would increase to                  work and heater shell limits
the reheater such that the hot                        about 822 MWe.                               increases in extraction pressure. In
reheat temperature is maintained                      In general it is thus better to              the case of the top heater being
without reducing the level of                         modify the boiler or operation of            fed from the cold reheat,
spray water. The increase in                          the boiler in order to maintain the          changes can only be made if the
power to 821 MWe (+1.86%) and                         reheat temperature and minimize              IP flow passing capacity is altered.
the reduction in heat rate (-1.11%)                   the heat rate, and then increase
is a result of increasing the                         the main steam flow to regain the            If the main steam flow is fixed, the
efficiency of the HP turbine. Note                    power.                                       potential of reducing the final
that the Boiler Total boiler heat                                                                  feedwater temperature and
input (Qfired) has increased to                                                                    increasing the power is often very
1903 MWth (+0.75%) and thus                           Final Feedwater Temperature                  attractive. A reduction of about
emissions will change accordingly.                                                                 5°F (approx. 3 °C) will yield about
                                                      The final feedwater temperature              5 MWe on a 600 MWe unit. There
With Option B, the hot reheat                         (or economizer inlet temperature)            will be a corresponding decrease
temperature is maintained by                          is a function of the performance             in heat rate of about 0.1%.
reducing the reheater sprays (i.e.,                   of the highest pressure (top)
no reheater surface modifications                     feedwater heater and its                     If the boiler heat input Qfired is to
are made). The power output of                        operating pressure. The ability to           be kept constant, another
817 MWe, achieved with the                            adjust the final feedwater                   alternative is to increase the final
lower RH spray flow, is below that                    temperature is important as it               feedwater temperature to
of Case A, but still is significantly                 allows the turbine cycle to be               improve cycle heat rate and then
higher than existing. Since the                       optimized still further for either           to recover the power by
heat input is essentially the same                    heat rate or power.                          increasing the main steam flow.
as existing, the heat rate                                                                         Boiler efficiency is mainly
decreased to 8333 kJ/kWh (7,898                       When the top feedwater heater is             dependent on the gas outlet
Btu/kWh) (-1.26%).                                    being fed via extraction from the            temperature. Some gains can be
                                                      HP turbine (Heating Above                    made on boiler efficiency by a
Option B thus gives the choice of
                                                      Reheat Point), the design of the             combination of adjustment of the
improving heat rate as a result of
                                                      retrofit HP turbine can                      economizer inlet temperature and
both improved turbine efficiency
                                                      accommodate an extraction                    economizer surface. These gains
and the cycle gain in reducing
                                                      point that can be moved a few                can be used either to reduce fuel
the spray flow. If the Qfired was

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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                         11


costs or generate more power by                       current boiler-turbine thermal          Changes in turbine cold reheat
increasing the main steam flow at                     performance. Once the                    steam pressure, temperature
the same constant fuel input.                         calibrated models are finalized,         and flow to the boiler
                                                      an initial set of changes will be
                                                                                              Evaluate changes in boiler
                                                      input based upon the expected
Joint Project Design                                  HP turbine or HP/IP turbine section
                                                                                               steam extractions, blowdown,
                                                                                               sootblowing steam, SH & RH
Team Reviews                                          redesign and improved
                                                      performance. This will establish
                                                                                               desuperheating flows, etc.
                                                      the baseline performance                Investigate impacts of sliding
Alstom has in-house expertise to                      upgrade that would be expected           pressure operation
optimize the performance of                           from the boiler- turbine complex
boiler and turbines. This applies to                  after retrofit.                         Investigate feedwater heaters
its own fleet as well as third party                                                           out of service
equipment. Alstom has                                 After establishing the expected         Investigate differences in winter
successfully demonstrated its                         baseline conditions, the customer        & summer operation
capability over the course of                         will be invited to visit Alstom
many projects executed to date.                       offices to participate in a Joint       Investigate impacts associated
The intent is to provide our                          Project Design Team Review. The          with emissions control
customers with the greatest return                    Joint Project Design Team Review         modifications
on investment by looking at the                       is a key feature of the process that    Consider the effects of
turbine-boiler complex as a                           Alstom is offering. It is also a         changing coal quality
whole, taking carefully into                          ―value added‖ benefit that we
account the interaction between                       believe no other OEM can                Consider operational changes
both.                                                 currently offer.                         to key parameters such as
                                                                                               excess air & tilt position, etc.
As part of the OPR approach, the                      The intent of this meeting is to        Consider impacts of potential
Customer is invited to participate                    gather the key boiler, turbine and       equipment modifications
in a Joint Project Design Team                        customer project design
Review Meeting. During an OPR                         personnel in one location to            The Joint Project Design Team
phase of a project, Alstom’s                          discuss and evaluate the                 Review effort can also be
steam turbine retrofit group works                    numerous potential future                tailored to investigate specific
together with the boiler retrofit                     operating conditions for the             problems or topics of interest
engineering personnel to establish                    boiler-steam turbine complex. This       that customers may have. It
the new thermal specification for                     evaluation process will provide          can be employed to obtain an
the boiler-turbine complex.                           near real time predicted                 understanding of how these
                                                      performance results for the              problems may impact the
This effort will be accomplished by                   suggested conditions that are            steam turbine HP or HP/IP retrofit
constructing mathematical                             analyzed. Examples of the types          project and/or how they an be
models of the boiler and turbine                      of operating conditions that can         addressed in concert with the
using Alstom’s proprietary                            be expected to be evaluated              turbine modification.
computer programs for turbine                         are:
                                                                                              Once all team members have
and boiler design.
                                                                                               agreed on which scenarios to
                                                       Changes to feedwater flow,
                                                                                               focus upon as a result of a Joint
Once the turbine and boiler                             temperature and pressure to
                                                                                               Project Design Team Review
models are constructed, current                         the boiler
                                                                                               meeting, Alstom can then
and complete unit data that is
                                                       Throttle steam temperature,            execute a more detailed
submitted by the Customer will be
                                                        flow and pressure changes              engineering evaluation in order
reviewed for accuracy. Once the
                                                                                               to develop associated
data is determined to be                               Steam purity to the turbine            modification requirements and
acceptable, it will be input into                       (discuss copper transport and          detailed cost estimates.
the computer models to establish                        deposition issues)
a calibrated representation of the



3 - Integrated Project Execution
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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                          12


OPR projects are inherently                           about specific details that             least expensive type of major
complex and consequently may                          contradict each other, scope            project. This approach can
require significant coordination                      omission or even duplication can        eliminate the need and/or reduce
between the Customer, the                             occur. A turnkey bid specifications     the time required for third party bid
equipment supplier, and the                           promote suppliers to arrive at the      specification preparation, bid
installation contractor. Significant                  lowest combined price. Scope            issuance, proposal development,
advantages can be realized when                       omission/duplication no longer is a     bid evaluation and contract
wrapping the total project scope                      risk for the Customer since it          negotiation. Competitively bid
responsibility around a highly                        becomes the single supplier’s           turnkey projects are the next
competent single supplier such as                     responsibility.                         quickest type of major project.
Alstom, in a full and comprehensive
turnkey scheme.                                                                               The reason is that the material
                                                      Design Opportunities for                design/supply and construction
Consolidating defined project                         Lowest Evaluated Cost                   design teams work together from
scope responsibility around a single                                                          the very beginning. Conversely,
supplier avoids the burden of                         Many times, unique material design      projects requiring separate material
developing two (or more) separate                     and supply configurations can be        and labor bids typically require
bid specification documents. It                       identified that can reduce              more time because the
eliminates the risk that scope                        installation duration. Opportunities    construction bids aren’t usually
boundaries between separate                           for reducing overall project risks      possible before the material
material and labor contractors                        with an incremental addition or         supplier provides the initial design
don’t match. Depending upon the                       variation to the material design or     information, sometimes well into the
level of complexity, it may reduce                    manufacturing process are missed        material contract phase. Turnkey
or even eliminate the need for                        when material suppliers compete         project format is the preferred
outsourced engineering services                       on a lowest delivered material          method for ―fast track‖ projects
while minimizing the risks associated                 price basis.                            where the minimum project
with complex projects.                                                                        lifecycle from technical concept
                                                      Similarly, opportunities for the        through installation and final
Additionally, a turnkey approach                      introduction of labor saving design     customer acceptance is a key
will also reduce the need for                         changes based on input from the         driver or requirement.
potential limited power company                       installation contractor are missed
resources.                                            when the installation bid               Negotiated turnkey projects also
                                                      preparation doesn’t occur until         open the door to the use of some
                                                      after the material design is fixed.     advanced technologies to identify
Single Accountable                                                                            opportunities for reducing outage
Supplier                                              Also, working with a single material    duration during the project
                                                      and installation supplier may           planning stage that simply aren’t
Any and all issues between                            provide an opportunity to consider      practical for inclusion in proposal
material supplier and installation                    sensible decisions early in a project   development activities for
contractor become invisible to the                    about the integrated material &         competitively bid projects.
Customer with turnkey projects.                       installation design where
                                                      incremental and opposing cost           For example, Alstom uses when
                                                      changes from material to                applicable, computer animation
Reduced Risk of Scope                                 installation and vice versa can         starting with scale CAD drawings to
Omission                                              result in outage duration changes       help optimize construction
                                                      where the value of plant revenue        sequencing, determine and prove
                                                      comes into play, enabling arrival at    optimum component or module
Individual competitors carefully
                                                      the truly lowest overall evaluated      sizes, and even help train craft
analyze separate bid specifications
                                                      cost.                                   personnel to better understand the
for material and installation in order
                                                                                              construction plan. This is
to develop the most competitive
price. Unless the specifications are                                                          particularly useful in evaluating
extremely comprehensive, some                                                                 construction rigging needs, as well
scope detail assumptions typically                    Reduced Project Lifecycle               as planning when multiple labor
have to be made. If the selected                                                              teams need to coordinate
material and installation                             A negotiated turnkey project is the     separate construction activities in
contractors make assumptions                          quickest to execute and potentially     close proximity to one another.


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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                         13




4 - Case Studies
                                                      in early January, 2004. The overall
Newton, U.S.A.                                        objective of the OPR effort was to     A range of boiler modification
                                                      evaluate the Newton No. 1              options were evaluated during the
In November, 2002 AMEREN Corp.                        performance with a high efficiency     review process and AMEREN, with
commissioned Alstom to implement                      Alstom HP/IP turbine retrofit and a    input from all Joint Project Design
a Boiler Engineering Study intended                   new economizer section of the          Review Team members, eventually
to assess available actions that                      boiler. The impacts of boiler and      selected modifications to the Low
could be implemented on Newton                        turbine boundary condition             Temperature Superheater, Front
No. 1 boiler to effect thermal                        changes as a result of these           and Rear Reheater pendants and
performance improvements while                        modifications were assessed to         the replacement of the
firing 100 % USA Powder River Basin                   determine if heat rate and total       economizer to an in line spiral
(PRB) coal (one of world largest                      output megawatts could be              finned design.
coal deposit, named after the                         improved without exceeding
crossing through Powder River).                       current plant emissions restrictions   Installation of the new turbine
Alstom conducted this study in                        or other limitations.                  cylinders, coupled with the boiler
Spring, 2003 and identified several                                                          modifications, was predicted to
actions that the Customer should                      The results to date of the OPR         result in an increased generation of
consider. These actions included                      process indicate that the              approximately 40 MWe over base
certain pressure part upgrades and                    November, 2003 operating data          line data conditions. This increase is
modifications to the existing                         characterized boiler and turbine       the result of revised steam flow to
sootblowing system.                                   operating conditions and is of         the turbine, heat rate
                                                      sufficient accuracy to represent       improvements associated with the
Subsequent to the execution of this                   typical unit operation. The current    new cylinders and revised
initial boiler study, the Customer                    operating data indicated that the      feedwater boundary conditions.
identified that upgrade of the HP/IP                  turbine was maintaining close to       Table 2 below provides a summary
turbine cylinders to current day                      original gross megawatt generation     of performance changes
technology would result in a                          but performance had deteriorated.
significant economic payback and                                                             Alstom’s steam turbine retrofit
benefit. Following discussions                        This was evidenced by increased        group was responsible for the new
between various Alstom and                            steam flow and lower feedwater         turbine HP and IP cylinders.
AMEREN personnel it was quickly                       inlet temperature. The Joint Project   Alstom’s boiler retrofits group was
realized that execution of a                          Design Team Review modeling            responsible for the supply of a new
combined boiler and turbine                           session showed that additional         spiral finned, in line arrangement
evaluation to optimize overall plant                  Superheater and Reheater surface       economizer, as well as
performance should reap                               would be required to achieve and       modifications to the low
improved benefits that could not                      maintain original boiler design        temperature superheat section
be achieved independently.                            outlet steam temperatures of           and modifications to the front &
                                                      540°C/540°C (1004°F/1004°F) under      rear pendant reheat sections of the
The plant obtained current unit                       a range of operating conditions        boiler. These modifications were
operating data in November, 2003                      with the new turbine cylinders and     implemented in 2006.
and submitted this data to ALSTOM                     economizer installed.




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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                                14




Newton #1 record                                    Initial Conditions               2003 Operating Data         Predicted future operation

                                                        1787 t/hr                         1832 t/hr                        1905 t/hr
Main steam flow
                                                    (3,938,761 lb / hr)               (4,038,529 lb/ hr)               (4,200,000 lb/hr)
Superheater outlet
                                                     540°C (1004°F)                    535.6 °C (996°F)                 540°C (1004°F
temperat.
Reheater outlet
                                                      540°C 1000°F                      539°C (1002°F)                  540°C (1004°F)
temperature
Throttle pressure                               16.65 Mpa a (2415 psia)          16.65 Mpa a (2415 psia)          16.65 Mpa a (2415 psia)
Feedwater temperature                                254°C (489.0°F)                 247°C (476.6°F)                  252°C (484.0°F)
Gross generation MWe                                      590                             595                               637
Boiler efficiency %                                      88,47*                         85.46 **                          86.24**
                                                      8049 kJ/kWhr                                                     8234 kJ/kWhr
Turbine Heat rate                                                                            NA
                                                    (7629 Btu/kW-hr)                                                 (7804 Btu /kW-hr)
All data values taken at
                                               * reflects boiler efficiency
turbine or FW heater outlet                                                                    ** firing Powder River Basin coal
                                               firing Midwest bituminous coal
except boiler efficiency.

                      Table 2 – Comparison of Original Predicted Performance with Current Operating Results
                            and Future Predicted Performance with Upgrades & Modifications in place.


                                                          plant had to be considered. Major                outage, economizer and air
Labadie, U.S.A.                                           retrofits were initiated on all four             preheater
                                                          units beginning in 1988 and
At AMEREN UE’s Labadie Plant,                                                                          2003; Unit 3 outage, economizer,
                                                          continuing over the course of the
located just outside St. Louis,                                                                         air preheater, HP/IP and LP
                                                          next 15 years. The year and scope
Missouri, in the U.S.A., all four                                                                       turbine retrofit; Unit 4 : HP/IP and
                                                          of each outage is detailed as
tangentially fired units were                                                                           LP turbine retrofits
                                                          follows:
included in a long-term
commitment to upgrade the plant.                           1988 – Pulverizer vane wheel
                                                                                                      The results from the extended effort
The units were originally placed in                         replacement
                                                                                                      were impressive. The modifications
commercial operation from 1971 to                          1992 – Low NOx firing system              improved overall plant
1974. Each was designed to                                  installation                              maintenance and reliability,
produce 600 MWe firing a high-                                                                        significantly decreased emissions
energetic Midwest bituminous coal.                         1993 – Test-fire Powder River Basin
                                                                                                      and provided and overall increase
Steam output from each unit was                             coal
                                                                                                      in net output per unit of 40 to 45
supplied to a tandem compound                              1994 – Install (a) high efficiency        MWe with essentially the same heat
turbine with two double-flow LP’s.                          pulverizer exhausters and (b) new         input. Some details on the overall
                                                            steam inerting system                     improvements provided by the
Starting in the mid 1980’s AMEREN                                                                     modifications are as follows:
UE Labadie Plant and Alstom                                1995 – Fire 100 percent PRB coal
began a large-scale retrofit                               1996 – Install additional
program focused on improving the                                                                       20% increase in pulverizer
                                                            sootblowers                                 capacity eliminated fuel input as
plant’s operation. AMEREN UE and
Alstom worked together using a                             1997 – Modify plant controls                a unit load limitation
systemic approach to identify key                                                                      Steam inerting system improved
                                                           1998 – Aggressive NOx tuning
component improvements.                                                                                 pulverizer safety with PRB coal
Modifications ultimately included                          2001 – Unit 2 outage,
overhauling coal mills, firing                              economizer, air preheater, HP/IP           Firing system modifications
systems, assorted pressure parts, air                       turbine replacement                         resulted in significant NOx
heaters and steam turbines.                                                                             reduction. When combined with
                                                           2002 – Unit 1 outage,                       operational tuning, the Labadie
Alstom’s ability to analyze the
                                                            economizer, air preheater, HP/IP            units became the lowest non-SCR
entire plant was critical since the
                                                            turbine replacement; Unit 4                 NOx emitters in the United States
effect of each change on the total
                                                                                                        for three years in a row.

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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                            15


 Superheater division panel                              capacity and availability factors         Lower auxiliary service power
  modifications eliminated gas flow                       on all four units.                        resulted in a 3 to 6 MWe net
  restrictions resulting in a 12 MWe                                                                capacity increase.
                                                         New economizer and air heater
  capacity increase. This action
                                                          lowered gas temperature thus           New HP/IP turbine retrofit
  also addressed the primary
                                                          improving ESP efficiency and            improved machine efficiency
  source of boiler tube leaks and
                                                          reducing opacity. Also reduced          resulting in 25 to 27 MWe increase
  thus significantly improved the
                                                          gas path delta-P thus reducing          in capacity.
                                                          the fan horsepower requirement.


Labadie record                                                      1977                      1985                      2001
                                                                                                                    20,000 kJ/kg
Coal heating value                                                   25,586 kJ/kg (11,000 Btu/lb)
                                                                                                                    (8600 Btu/lb)
Generation (MWhrs)                                               12,200,000               13,100,000                 16,700,000
Coal Burned (tons)                                                5,250,000                5,000,000                  9,500,000
Max. Unit Capacity (MWe)                                              580                      580                       630
                                                                  0.3 kg/kJ                0.26 kg/kJ                 0.05 kg/kJ
NOx
                                                                (0.7 lb/MBtu)            (0.6 lb/MBtu)             (0.115lb/MBtu)
                                                                  2.6 kg/kJ                2.06 kg/kJ                 0.22 kg/kJ
SOx
                                                                 6.0 lb/MBtu              4.8 lb/MBtu              (0.52 lb/MBtu)
Operating Availability                                                75%                      77%                       90%
Pulverizer Capacity t                                               90,000                   90,000                    120,000
Outage Interval, months                                                12                       18                        36
                                               Table 3: Labadie record : summary of unit performance.


Arnot, Republic of South Africa
RSA's booming economy and the                           ESKOM, embarked upon a massive          The key success factors were the
electrification of the townships                        program to expand its capacity.         ability to offer a credible optimized
have meant that peak electrical                         ARNOT is a 6 x 350 MWe coal fired       integrated approach, to manage
demand has been increasing at 3-5                       power station that will be part of      interfaces efficiently and ―off-line‖
per cent every year since 1999. It is                   this program                            with the customer resulting in a
expected that the need for energy                                                               single contract administration. The
will continue to grow at the same                       A key driver for the ARNOT OPR          OPR project covers the boiler, the
pace and that South Africa may                          project was the capacity increase       HP, IP and LP turbines, the
run out of peak capacity next year                      through a quick and competitive         condenser and other BOP
and base load capacity by 2010.                         method of upgrading the output to       components.
                                                        400 MWe (per unit), combined with
That is why the South African                           an extension of plant life for          ARNOT was awarded in 2006, and
electricity supply company,                             another 20 years.                       completion of first unit is due
                                                                                                December, 2007.




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                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                         16




5 - Conclusion
In recent years many utilities have                   potential impacts of such a           upon calibrated calculation
been struggling with the issue of                     change are fully understood and       models, during one common
needing to increase generation                        addressed.                            working session where all the
capacity while at the same                                                                  specialists from various disciplines
operating within more and more                        The assessment of changes that        provide their input.
stringent environmental permits.                      impact the flue gas boundary
Adding new generating units may                       conditions leaving the boiler has     This procedure has proven to result
not be feasible due to real estate                    become increasingly important as      in retrofit solutions that give the
availability, environmental issues,                   utilities continue to be faced with   optimum return on investment to
lengthy permit procedures, political                  the requirements to meet ever         our customers.
issues and/or other issues.                           more stringent environmental
                                                      regulations regarding the emissions   In addition, a CO2-constraint
In these cases retrofitting of power                  of flue gas particulates, NOx, SOx    economy is now emerging. CO2
stations offers a very attractive and                 and other pollutants.                 capture technologies are currently
cost-effective method of increasing                                                         developed by Alstom and other
plant output and reducing heat                        Alstom’s experience indicates that    vendors and bring, to various
rate. The fact that the installation                  this can best be accomplished by      degrees, some penalty on the
of a retrofit can often be done                       bringing together all the key         overall system efficiency.
within a normal outage is of                          contributors involved in a retrofit   Therefore, it makes sense to bring
additional benefit. The full                          project. As part of its OPR           the underlying cycle to the best
utilization of the existing latent                    (Optimized Plant Retrofit)            performance. Optimized Plant
capability of installed equipment                     approach, Alstom offers to its        Retrofits are well adapted to this.
necessitates a system evaluation                      customers the unique opportunity
approach to ensure all of the                         to look at various scenarios, based



6 - References
[1] Condition Assessment and                               Europe Exhibition, June 2002,         Newton Steam Power Plant –
    Modernization of Large Utility                         Milan, Italy                          Unit #1, Turbine and Boiler
    Boilers, A. Crosson, JC                                                                      retrofit; P. Bartley, (ALSTOM);
                                                      [4] Establishing Optimal Thermal
    Foucher, G. Camody, P.                                                                       D. Boll, J. Marshall and P.
                                                          Conditions for Steam Power
    Wooley, ALSTOM, CEPSI 2000                                                                   Morrell (AMEREN), Electric
                                                          Plant Retrofits, R. Hestermann,
    Conference, Manila, The                                                                      Power 2005 Conference,
                                                          D. Stephen, and P. Bartley, t
    Philippines, October 2000                                                                    March, 4, 2005
                                                          ALSTOM, Steam Turbine
[2] Optimized Plant Retrofits, Don                        Retrofit Conference, San          [7] ALSTOM's Integrated Retrofit
    Stephen BSc, in Proceedings                           Francisco, U.S.A., 16-17th            Projects Concept, a solution
    of IJPCC '01, 2001                                    September 2003                        approach to renovation and
    International Joint Power                                                                   modernization, ALSTOM,
                                                      [5] Make Your Boilers
    Generation Conference, June                                                                 International conference &
                                                          Environmental Friendly : A
    4-7, 2001, New Orleans,                                                                     Exposition on "Indian Power
                                                          Portfolio of Advanced
    Louisiana, USA                                                                              Stations, Managing the Game
                                                          Technologies, Jean-Claude
                                                                                                Changers", Delhi, India, 13-15
[3] Rehabilitation of Old Power                           Foucher, Alain Bill, ALSTOM,
                                                                                                October 2005
    Plants for Improved                                   19th Power System
    Environmental Performance,                            Conference, Teheran, Iran,        [8] A Review of the State-of-the-
    Reliability, Efficiency and Fuel                      Nov. 2004.                            art and a View of the Future
    Flexibility, JC Foucher, J. Barth,                                                          for Combustion-Based Coal
                                                      [6] Establishing Optimal Thermal
    E. Pianini, ALSTOM, PowerGen                                                                Power Generation, S. Black, A.
                                                          Conditions for AMEREN
                                                                                                Bill, J.L. Marion, G. Liljedahl,
4579d369-0416-482b-b04b-808d96836441.doc                                                                               
                                               Maximizing Economic and Environmental
                                               Performance of Existing Coal-Fired Assets
                                                                         17


        ALSTOM, Institute of Clean Air                    Power Plants Retrofits, P.     Bartley, M. Salerno, ALSTOM,
        Companies Forum March 8-                          Bartley, R. Hestermann, D.     Steam Turbine Retrofit
        10, 2005, Baltimore, MD, USA                      Stephen, ALSTOM, May 2006      Conference, May 2006,
                                                                                         Chicago, U.S.A.
[9] Update on ALSTOM's Process                        [10] Integrated Environmental,
    for Establishing Optimal                               Boiler and Turbine Retrofit
    Thermal Conditions for Steam                           Solutions, D. Stephen, P.




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