Challenges of Engineering Education by HC120519182322

VIEWS: 12 PAGES: 43

									   OPTIMIZATION OF
CONVENTIONAL THERMAL
 & IGCC POWER PLANT
FOR GREEN MEGA POWER
Dr. V K Sethi               &           J K Chandrashekar
Director                                 Adviser
            University Institute of Technology
                      RGTU Bhopal
WORLD SUMMIT ON SUSTAINABLE DEVELOPMENT

       AGENDA FOR THE ENERGY GENERATION SECTOR:
      Increased use of Advanced Fossil Fuel Technology.

      Promote CCT in countries where coal is main stay
       fuel for Power Generation.

      Reduce Atmospheric Pollution from Energy
       Generating Systems.

      Enhance productivity through Advanced Fossil Fuel
       Technology.
      Adoption of Renewable Energy Technologies in
       Rural Sector
     INDIAN POWER SECTOR JOINS TERA CLUB
                   BY 2010

   POWER GENERATION BY UTILITIES TODAY
     1,47,965 MW …600 Billion kWh per annum
   TARGETTED CAPACITY ADDITION BY XI PLAN END
        Central                 46,500 MW
        State & IPP             41,800 MW
        NCES                    10,700 MW
        Nuclear                 6,400 MW
         Total                         105,400 MW

   BY 2012 WE NEED TO GENERATE ANNULLY
                       …Over 1000 Billion kWh
   THUS WE WILL BE A TRILLION or TERA kWh (Unit)
    GENERATING POWER SECTOR BY 2012
Tera-watt Challenge for synergy in Energy
& Environment
    A terawatt Challenge of 2012 for India
     To give over one billion people in India the minimum Electrical Energy
     they need by 2012, we need to generate over 0.2 terra watt (oil
     equivalent to over 3 million barrels of oil per day) and 1 TW by
     2040,primarily through Advanced fossil fuel technologies like CCTs for
     limiting GHG emission levels
    By 2020 our mix of generation would have the Peak
     in Thermal, certainly   it would be the Green
     Thermal Power:
             Thermal                     326,000MW
             Renewable & Hydro           104,000 MW
             Nuclear                      20,000 MW
             Total                       450,000 MW
               POWER SCENARIO IN INDIA

    Installed capacity in Utilities as on April 07
                                              …1, 47, 965
    MW
   Thermal Installed Capacity…93,726 MW
    (Coal 77,648 MW, Gas 14,876 MW, Diesel 1202 MW + Others- cogen etc.)

   Hydro Power …36,877 MW
   Nuclear Power … 4120 MW
   Renewable Energy Sources …13,242 MW
   Electric Demand…..7-8% growth
   Peak & Energy Shortage…..16.7% & 12.1%
   Capacity Addition in 11th Plan……80,020 MW
     INDIAN POWER SECTOR - TOWARDS
     SUSTAINABLE POWER DEVELOPMENT
   Total Installed Capacity … 1,47,965 MW
   Thermal Generation      … over 66 %
   Although no GHG reduction targets for India
    but taken steps through adoption of
    Renewable Energy Technologies,Combined
    cycles, Co-generation, Coal beneficiation,Plant
    Performance optimization
   Under Kyoto Protocol; Clean Development
    Mechanism (CDM) conceived to reduce cost of
    GHG mitigation, while promoting sustainable
    development as per Framework Convention on
    Climate change (FCCC)
Prime Clean Coal Technology Options

    Supercritical Power Plants
    Integrated Gasification Combined
     Cycle (IGCC) Power Plants
   Circulating Fluidized Bed
    Combustion (CFBC) Power Plants
     FRONTALS IN ENERGY & ENVIRONMENT

   GREEN ENERGY TECHNOLOGIES – PRIMARILY THE
    CLEAN COAL TECHNOLOGIES

   ZERO EMISSION TECHNOLOGIES FOR TRANSPORT,
    POWER PLANTS & INDUSTRIAL SECTOR

   AFFORDABLE RENEWABLE ENERGY TECHNOLOGIES

   ENERGY EFFICIENCY

   CDM OPPORTUNITIES IN ENERGY SECTOR
 OPTIMISATION
       OF
A CONVENTIONAL
THERMAL POWER
     PLANT
  ENERGY CONSERVATION
  IN THERMAL POWER STATION
          Efficiency Improvement Opportunities
Average 1.5% increase in effeciency of Thermal Power Plants in
India could result in:
 CO2 reduction: 4.5% per annum (over 10 Millon Ton/ annum)
 Coal savings: 9 Million tons per annum
 Coal savings worth Rs. 630 Crore
 Higher productivity from same resources; equvalent to
  capacity addition.
 Lower generation cost per KWh.

                                                            1
 ENERGY CONSERVATION
 IN THERMAL POWER STATION
ENERGY BALANCE OF 500 MW PLANT UNIT
                                     %   MW
Heat input to boiler                100  1428
Boiler losses                       9.5  137
Steam & feed range radiation losses 0.5   7
Condenser loss                      52.5 750
TG set Elec. & Mech. Losses         1.5   20
Works Auxiliaries                    1    14
Generator output                     35  500
                                            2
ENERGY CONSERVATION
IN THERMAL POWER STATION

 EFFICIENCY OF VARIOUS IDEAL CYCLES

Basic Rankine Cycle                    41.40%
Cycle with superheat                   45.80%
Cycle with reheat                      47.50%
Cycle with superheat and feedheating   52.00%
Cycle with reheating and feedbeating   53.20%
Carnot Cycle                           52.10%

                                                3
ENERGY CONSERVATION
IN THERMAL POWER STATION

      ENERGY EFFICIENT MEASURES
          DURING OPERATION
Factors during operation - Turbo-Generator:
(1)   Controlling the throttle losses.
(2)   Optimising condenser performance.
(3)   Optimising feed heaters performance.
(4)   Optimising auxiliaries consumption.
(5)   Reduction in make-up water consumption.
                                                11
      Optimization of Prime Performance
    Functions- Heat Rate & Boiler Efficiency
    Heat Rate – The Heat supplied to Steam in Boiler for producing
     one kWh
    MATHEMATICAL MODELING
     The mathematical models for the plant performance can be divided
     into two main categories
1. Basic Models: These consist of
     (a)   Steam table model.
     (b)   Combustion model –total approach to combustion of PF.
     (c)   Wet steam expansion model.
     (d)   Boiler heat transfer model for radiation and other unaccountable losses
2. Specific models
    Boiler accountable losses based on fuel characteristics.
    Mill operation window.
    Unburnt Carbon
    Turbine heat rate.
    Cylinder efficiency.
    Condenser performance.
    Feed heaters.
    Overall unit heat rate model.
TURBINE HEAT RATE MODEL
     The system chosen for the purpose of modeling and subsequent optimization is a
     210 MW unit with cycle diagram given in figure 1. This is an information flow
     diagram showing temperatures, pressures and flows at critical locations and a
     control volume to determine the net energy exchange between the boiler and the
     turbine.
     Turbine heat rate objective function with reference to above figure is,
                M ms (hms  h fw )  M hr (hhr  hcr )  M gs (hhs  h fw )
     THR 
                                      KW  KWA
     Where mass flows are simulated as functions of pressures and temperatures as
     given below
Main, reheat and extraction flows: As functions of Operating paprameters
                                      0.5
                    P 1   P 
      M ms    13250 ms
                           cr 
                    Vms1  Vcr 


                                                 
       M hr  M ms  ( M ex7  M ex6 )   M gl1 
                                         1       



                                  P 7
      M ex7  19410                ex

                              t ex7  273



                                P 6
       M ex6  36205             ex

                             t ex6  273
Leak offs from HP turbine in reference to figure 2 are:

                                Pcr2  Pgli 2
         M  K
         1
             gli
                      1
                          gli
                                  PgliVgli


Where              Kgli = 8.8766, 75.137, 106, 776 77.6, 4235.0 for i=1, 2, 3, 4 & 5
respectively.
        Pcr = Cold reheat line pressures and Curtis wheel pressure at each
             value of i for leak offs from both sides of turbine.
Gland steam flow
                    Pgs1               Pgs2                 Pgs3               Pgs4
    M gs  58019              1839              111034              6896
                 t gs1  273        t gs2  273          t gs3  273        t gs4  273

     Turbine heat rate objective function is given on right side of the scheme ‘NPHR’,
     given at Figure 3. It gives objective function for turbine heat rate NTHR considering
     effect of various operating parameters as well as the associated condenser vacuum
     system. Steam properties are drawn from various subroutines and the two-phase
     enthalpy through subroutine EXHAL.
     An increase in boiler excess air increases steam outlet temperature, as most of the
     super heaters are convective type and requires larger spray input for temperature
     control, ultimately affecting the turbine heat rate. This is known as two ways
     coupling as shown in figure -3. The results of two-way coupling are given at fig. 4 in
     which Plant Heat Rate is plotted against boiler excess air and particle size of
     pulverized fuel.
OPTIMIZING BOILER EFFICIENCY:
     A heat balance diagram of 210 MW, boiler shown in Fig.5 is used to estimate the
     various boiler losses. While other boiler losses could be determined using standard
     ASME PTC- 4.1 Formulations, the combustion losses and the un-burnt carbon loss
     could be modeled using probabilistic approach. The probability that a particle would
     remain un-burnt depends on the difference between combustion and particle
     residence time. This probabilistic approach yields following empirical relation for a
     PC boiler for Un-burnt carbon loss
                                                     ( D) 2    A
     Un-burnt carbon loss per kg of coal= 0.3008 10   8
                                                                  CVc
                                                       E      100
     Or,
     Un-burnt carbon loss per kg of coal= U c  CVc

     Where:
              D: particles diameter in meters
              E: Excess air percentage
              A: Ash percentage
              CVc: Calorific value of Carbon.
                                           CO
        Incomplete combustion loss= (             )CVc (C  U c )
                                         CO2  CO

Using above models and ASME test code formulations for other losses the boiler efficiency
is determined for different values of excess air and particle diameter.
The boiler efficiency variation with excess air for particle sizes ranging from 80 to 200µ is
plotted in figures 6. It is seen that the excess air considerably affects the boiler efficiency.
The excess air needed to attain maximum boiler efficiency increases with increase in
particle size of the pulverized fuel, with peak at 20 percent excess air for particles of 80µ
size and 50 percent for particles of 200µ size. Fig. 7 for Combustion loss shows that the
unburnt carbon loss drastically increases at low excess air values below 20 percent. The
optimum excess air at a particle diameter is given by:

                 Eopt  6.43  34 .72 D  2.29 D 2
          This formulation has a useful practical value in operation of modern pulverized
        fuel fired boilers as depicted at Fig. 8 drawn for particle size variation from 80 to 200
        microns and gas outlet temperature variation from 140 to 155 degree Celsius.
INTEGRATED OPTIMIZATION
       A computer programme was run for the 210 MW unit as shown schematically in
Figure 9 using specifically designed software ‘ULTMAT’. In this program both Turbine and
Boiler are independently optimized and then through an overriding program for two way
coupling a correction is provided. Some of the results of the program are summarized in
the following Table:


Average Particle   Excess air for      Excess Air for minimum Plant Heat Rate (PHR) at
Size in Microns    Optimum Boiler      various back pressures in milli bar (mb) of the
(u)                Efficiency          Condenser
                                           94.3 mb             130 mb       150 mb

      200 u             51.0 %              24.8 %             23.97 %      23.18 %
      150 u             24.0 %              21.0 %             20.12 %      19.85 %
      80 u              20.2 %              15.0 %             14.77 %      14.35 %


       It is seen that the coupling between boiler and turbine becomes more complex with
firing of large size PF particles and at deteriorated backpressures.
The scheme is considered useful in online and on-time performance Monitoring and
Analysis of a Thermal Unit.
REFERENCES
    1.   Sharma, P.B., Sethi, V.K. "A Technique for computerized Thermal Power
         Plant Performance Monitoring", Jr. Irrigation and Power, Min. of Energy,
         India, pp. 417-428, July 1984.

    2.   Sethi, V.K. Sharma, P.B. and Gupta, SK " A mathematical Model of turbine
         heat rate for a Thermal power Plant ", Jr. IEEE, pp. 1257-61, Dec. 1983.


    3.   Sethi, V.K., Sharma, P.B. and Gupta, SK "Effects of Condenser Performance
         on Turbine Heat Rate of a Thermal Power Plant", Jr. of Thermal Engg. Vol. 4,
         No.2, pp. 46, 1985.

    4.   Sethi V.K. and Sharma, P.B. "A Model for combustion Losses in a
         pulverized fuel fired power plant boiler"; Proc. I. Mech.E. (London), Vol. 202,
         No. A4.


    5.   Sethi V.K. and Sharma, P.B. "Computer Aided Optimization of Turbine Heat
         Rate of a Thermal Power Plant", Trans. ASME. "Jr. of Energy Resources",
         1984.

    6.   Sethi V. K. “Performance Monitoring and Testing - Some Newer Techniques”,
         Jl. CEA, December 1997.
IGCC (Integrated Gasification Combined
                Cycle)
    The IGCC process is a two-stage combustion
    with cleanup between the stages.
   The first stage employs the gasifier where
    partial oxidation of the solid/liquid fuel occurs by
    limiting the oxidant supply.
   The second stage utilizes the gas turbine
    combustor to complete the combustion thus
    optimizing the gas turbine/combined cycle
    (GT/CC) technology with various gasification
    systems.
IGCC (Integrated Gasification Combined
                Cycle)
   The Syn-Gas produced by the Gasifiers however,
    needs to be cleaned to remove the particulate, as
    well as wash away sulphur compounds and NOx
    compounds before it is used in the Gas Turbine.
   It is the Integration of the entire system
    components, which is extremely important in an
    IGCC Plant.
   Various sub-systems of an IGCC Plant thus are:
       i) Gasification Plant
       ii) Power Block
       iii) Gas Clean-up System
                       IGCC
                         Gas
                       Clean Up
                                         Fuel
COAL
           Raw Gas
                       Steam      Combustion
            Cooler
                                   Chamber

                        Air
Gasifier
             Booster                                    Alternator

                        Comp.                   Turb.



  Ash                   Air

             Steam                                      Alternator

                                                 ST




                 Exhaust
                  Gases

                                            Condenser
                                   WHB
    Coal Gasification

   Combustion Process: Excess Air
   Gasification Process: Partial Combustion of
    coal with the controlled oxygen supply
    (generally 20 to 70% of the amount of O2
    theoretically   required     for  complete
    combustion)
       C + 1/2 O2 gasification CO
       C + H2O gasification CO + H2
EXPECTED IMPROVEMENTS OF IGCC
    POWER PLANT EFFICIENCY
 Flexibility to accept a wide range of fuels
 IGCC technology has been proven for a variety of
  fuels, particularly heavy oils, heavy oil residues, pet-
  cokes, and bituminous coals in different parts of the
  globe. In fact the same gasifiers can handle
  different types of fuels.
 Environment Friendly Technology
 IGCC is an environmentally benign technology. The
  emission levels in terms of NOx, SOx and
  particulate from an IGCC plant have been
  demonstrated to be much lower when compared to
  the emission levels from a conventional PC fired
  steam plant. In fact, no additional equipment is
  required to meet the environment standards.
 Lower Heat Rates & Increased Output
 The heat rate of plants based on IGCC
  technology are projected to be around 2100
  kcal/kWh compared to 2500 kcal/kWh for the
  conventional PC fired plants
                  Gas Clean-up System

  The typical steps for Gas Clean-up System aim at
  particulate removal, sulfur removal and NOx removal.
  This is achieved as follows:

• Particulate Removal: Combination of Cyclone Filters &
  Ceramic candle Filters
• SOx & NOx removal: Combination of steam/water washing
  and removing the sulfur compounds for recovery of sulfur as
  a salable product. Hot Gas Clean-Up technology is currently
  under demonstration phase. Wet scrubbing technology,
  though with a lower efficiency, still remains the preferred
  option for gas clean-up systems in IGCC.
                  Sulfur Removal
• Sulfur from the hot fuel gas is captured by reducing it
  to H2S, COS, CS2 etc. The current sulfur removal
  systems employ zinc based regenerative sorbents
  (zinc ferrite, zinc titanate etc.) Such zinc based
  sorbents have been demonstrated at temperatures
  up to 650 0C.
• Sulfur is also removed by addition of limestone in the
  gasifier. This is commonly adopted in air-blown
  fluidized bed gasifiers.
• In fact, in the case of Air Blown Gasifiers, sulfur
  is captured in the gasifier bed itself (above 90%)
  because of addition of limestone. The sulfur
  captured in the bed is removed with ash.
          RGTU INITIATIVES
    Green Energy Technology Center has been set up
    to focus on following areas:
      - Clean Coal Technology & CDM
      - Bio-fuels and bio-diesel
      - Renewable Energy devices (hybrid) targeted to
        produce 1 MW Power for the campus
      - Energy Conservation & Management
      - CO2 Sequestration & CO2 capture technologies
.
                    Summary
 Coal is going to remain our main stay in Power Scenario.
 A synergy between Energy & Environment is need of the
  day as over 56% GHG Emission is from Energy
  Generating Systems, for which:
    Accelerated growth of Power generation should be
     coupled with        Environmental concern through
     adoption of Clean Coal        Technologies
    Renewable Energy Technologies need a fillip
     particularly for Rural Sector
    Heat Rate Optimization & Energy Conservation
     measures will go a long way in reducing Demand :
     Supply Gap
 IGCC is going to remain the prime CCT of the third
  Millennium for Indian Power Sector
THANK YOU

								
To top