Document Sample

                                           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

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.

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                                             Maximizing Economic and Environmental
                                             Performance of Existing Coal-Fired Assets

  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

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                                                 Maximizing Economic and Environmental
                                                 Performance of Existing Coal-Fired Assets

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 Boiler
     geometry and
                                                 criteria &                                             efficiency of the section in order to
                                                                        Turbine specs :
      equipment             turbine heat
                                                 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

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.
                                                  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

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

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

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

   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
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
                                                  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

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

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

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

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

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
Reheater outlet
                                                  540°C 1000°F                      539°C (1002°F)                  540°C (1004°F)
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
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

 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
                                                            (0.7 lb/MBtu)            (0.6 lb/MBtu)             (0.115lb/MBtu)
                                                              2.6 kg/kJ                2.06 kg/kJ                 0.22 kg/kJ
                                                             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

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,
e1559df2-44a4-44f2-b948-1432dac871fa.doc                                                                            
                                           Maximizing Economic and Environmental
                                           Performance of Existing Coal-Fired Assets

        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.

e1559df2-44a4-44f2-b948-1432dac871fa.doc                                                                  

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