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Heat rate audit in thermal power plant
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Heat rate audit in thermal power plant

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Heat rate audit in thermal power plant Heat rate audit in thermal power plant Presentation Transcript

  • HEAT RATE AUDIT INTHERMAL POWER PLANTSHIVAJI CHOUDHURY
  • The New ScenarioIn the new competitive scenario, powerstations must face: • To Reduce the generating costs. • To Maintain high availability, efficiencyand operational flexibility. • To Meet strict environmentalconditions. • To Manage and extend the equipmentlife, including systems modernization.
  • The Generation Cost The variable overall cost =(The PlantAvailability Factor ,Station Heat Rate ,Specific Fuel Oil Consumption , AuxiliaryEnergy Consumption ). The Variable Cost, decides thecompetitiveness of the electric units in agenerating pool.
  • The Generation Cost Reduction The kWh fuel cost = 70 % approxthe variable overall cost . The Fuel cost components: Thestation Heat Rate (kcal/kWh). To reduce the variable cost throughthe heat rate improvement.
  • Heat rate Heat rate is the heat input (fuel)required per unit of power generated(kcal/kWh), for specific fuel beingfired and specific site conditions. Station heat rate =Turbine cycle heat rate=-------------------------- x100Boiler efficiency %
  • Objective• To point out the causesand location of efficiency losses.• Improve stationheat rate.
  • LOSSES IN THERMAL POWER PLANT 1.Boiler losses 2.Turbine losses 3.Condensate/feed water system losses. 4.Circulating water system losses. 5.Steam conditions 6.Electrical auxiliary losses 7.Steam auxiliary losses 8.Fuel handing 9.Heat losses 10.Cycle isolation 11. Impact of parameter deviation on HEAT RATE 12.D M water Makeup
  • 1.Boiler losses Symptoms Boiler efficiency Exit gas temp high Excess air Causes 1.1.Moisture losses 1.2.Dry gas losses 1.3.Incompletecombustion 1.4.Radiation losses
  • 1.1.Moisture losses High moisture in air Tube leaks Coal quality
  • 1.2.Dry losses Boiler casing air leakage Air pre heater leakage Incorrect fuel air ratio Fouled heat transfer surfaces
  • 1.3.Incomplete Combustion Coal quality Increased in ash contain Increased in carbon contain Decreased Coal mill fineness Classifier vanes improperly adjusted Ring/roller wear Classifier vane wear Burner tips plugged/eroded Burner damper settings Incorrect fuel air ratio. Hi oxygen at boiler out
  • 2.Turbine losses Symptoms HP/IP/LP section efficiency Causes 2.1.Mechanical damage Metallurgical defects Maintenance practices 2.2.Flow area decrease Mechanical blockage Blade deposits 2.3.Flow area bypass 2.4.Flow area increase
  • 2.3. Flow area bypass H P Turbine inlet bushing leakage Main steam valve leakage H P gland seal leakage IP steam /intercept valve leakage I P Turbine inlet bushing leakage
  • 2.4. Flow area increase Spill strip or packing leakage. Rubbing Thermal stress Erosion of turbine stages. Solid particle erosion of nozzle block. Condenser leaks Poor water chemistry Blade mechanism damage.
  • Leaking steam notcontribution to powergeneration (in RED)2.5.Cross section of turbine –showingefficiency loss due to leakage
  • 3.Condensate / F W systemlosses Symptoms Low feed water temp Causes HP/LP heaters out of service CEP/BFP efficiency Shaft rub Impeller wear Flow resistance path increase LP/HP heaters (high TTD/DCA) Excessive tube plugged FW heater out/bypass FW heater level low/high
  • 4.Circulating water losses Symptoms High back pressure Causes Number of CW pump in operation Air binding of condenser tubes Excessive air in leakage Inadequate air removal capacity Fouled condenser tubes Microfouling Plugged condenser tubes Air binding water box Low circulating water flow Increased CW system resistance Decreased CW pump performance Excessive condenser tube plugged
  • 5.Steam condition Firing conditions High super heater spray flow High re heater spray flow Inadequate heat transfer surface
  • 6.Electrical auxiliary losses Symptoms Station load Causes Precipitator (ESP) performance Ash deposit Excessive rapping High ash in coal Fan (ID,FD,PA ) Change in fan efficiency AHP chocking Pump (BFP,CEP,CW ) Change in pump efficiency LP/HP Feedwater heater tube plugged Coal Mill performance Classifier setting incorrect Coal quality
  • 7.Seam Auxiliary Losses Excessive soot blowing Decreased in BFP Turbine efficiency Low inlet steam temperature Excessive steam flow through vacuumpump/ejector Steam trap/vent leaking Excessive usage of steam coil
  • 8.Fuel Handling Spillage from the belt/transport Measurement inaccuracies Coal pile erosion Wind erosion Water erosion Coal pile fire
  • 9. Heat Losses Insulation on duct, pipe , turbine etc . No insulation Insulation damages Poor insulation Cladding missing /loose Steam leakage. Leakage to blow down tank. Leakage through vents, drains.
  • 10.Cycle isolation Leakage from recirculation valves of BFP/CEP. Leakage through bypass valves. Leakage to condenser through high energydrains. Leakage to condenser through emergencycontrol valves of feed water heaters. Check high energy drains after every startup.Provide Thermocouple in High energy Drains,To detect passing of drain valve.
  • 11.Impact of parameter deviation on HEATRATE (210 MW ,KWU Turbine )-operatorcontrollable parameters.SN PARTICULAR UNIT DESIGNPARAMETERSINCREASE in HEATRATE DUE TODEVIATION fromdesign parameters(IN KCAL/KWH)MULTIPLICATIONFACTOR1 PARTIAL LOADING MW 210 24.7 PER 20 MW 1.2352 MS PRESS KG/CM2 150 25.5 PER 20KG/CM21.2753 MS TEMP AT HPT INLET DEG C 535 7.5 PER 10 DEG C 0.754 HRH TEMP AT IPT INLET DEG 535 6.6 PER PER 10DEG C0.665 CONDENSER VACUUM mmHg 660 23.4 PER 10 mmHg2.346 FEED WATER TEMP DEG C 241 16 PER 20 DEG C 0.87 RH ATTEMP FLOW T/HR 0 6.4 PER 10 T/HR 0.648 OXYGEN % IN FLUE GASES % 3 8 PER 1% 8•�From above it is clear that, to achieve minimum heat rate,keep the operating parameters as close to the design parameters.
  • .500 MW TURBINE CONTROLLABLELOSSES11.1
  • 12.DM Water makeup Boiler tube leaks Excess deaerator venting to atmosphere Excess continuous blowdown Excess steam lost through condenserventing Valve packing leaks Pump seal leaks Steam leaks to atmosphere
  • Normative station heat rate • Existing Coal based Stations – 210 MW – 2500 Cal/kWh – 500 MW – 2425 Cal/kWh – In respect of 500 MW and above units where the boilerfeed pumps are electrically operated, the station heatrate shall be 40 Cal/kWh lower than the station heat rateindicated above. • New Coal based Stations – 1.065 x Design heat rate. – Prescribed maximum permissible design heat rate todiscourage procurement of inefficient machines
  • Heat Rate Monitoring Daily Heat Rate Calculation by deviationmethod & Identification Of Heat Rate Losses Monthly Performance Test (as per ASMEPTC/BS/DIN PG test Method ) Boiler Efficiency Air -Preheater performance Economizer Performance Turbine Heat Rate HP-LP-IP Cylinder Efficiency Heaters & condenser Turbine cycle rate rate
  • HEAT RATE OF TURBINE CYCLEUNIT-Kcal/KWH 210 MW TURBINE(LMZ)- 2063 210 MW TURBINE (KWU)- 210 MW- 1952 168 MW - 2001 500 MW TURBINE (KWU)- 500 MW - 1945 400 MW- 1988 300 MW- 2063.2 250 MW - 2134.3
  • Maximum Turbine Cycle Heat RateNote – Prescribed maximum permissible heatrate to discourage procurement of inefficient machines
  • Example of 210 MW Operating efficiency of unit is 37.5 %. Unit heat rate is 2305 Kcal/kwhr To produce 860 Kcal ( heat equivalent toone kwhr) ,2305 kcal heat has to suppliedto boiler. Losses in the boiler- 266 kcal Losses in turbine generator- 1179 kcal Total losses-(266 +1179)= 1445 kcal Total heat input to boiler= (1445 + 860)kcalLOSSESProducesOne kwhr
  • Power plant efficiency Sub critical - 34% Super critical- 37% Ultra super critical 41%
  • Section wise losses in a particularthermal power plant
  • Major Reasons for Higher GrossHeat Rate in India 1. Low combustion efficiency lead to high carbon loss. 2. High force outages due to failure of boiler tubes. 3. Poor performance of milling system. 4. Lack of Maintenance planning and spare planning 5. Low turbine cylinder efficiency 6. High dry gas losses due to high unwanted excess air 7. Poor sealing and heat transfer in air pre-heaters 8. Low condenser vacuum. 9. High air ingress in the boiler and high heat loss due to poorinsulation 10. Poor Performance of ESP lead to failure of ID fan and lowavailability. 11. High cooling water inlet temperature due to poorperformance of Cooling Tower. 12. Non availability of quantity and quality coal. 13. High auxiliary power consumption . 14. Obsolete C&I system . 15. Poor quality critical valves lead to passing and poor control
  • Conclusion Only Improvements in the stationHeat Rate, Specific Fuel OilConsumption and Auxiliary EnergyConsumption can makegenerating units competitive.
  • Less Emissions As the heat rate decreases (heat rateimproves), the amount of fuel for thesame generation also goes down. Ofcourse with less fuel burned, emissions(green house gases) are lowered.
  • THANKING YOUHeatingBy LP heatersHeatingBy HP heatersLPExpansion