HEAT RATE AUDIT IN THERMAL POWER PLANT

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Presentation Transcript

HEAT RATE AUDIT IN THERMAL POWER PLANT: 

HEAT RATE AUDIT IN THERMAL POWER PLANT SHIVAJI CHOUDHURY

The New Scenario: 

The New Scenario In the new competitive scenario, power stations must face: • To Reduce the generating costs. • To Maintain high availability, efficiency and operational flexibility. • To Meet strict environmental conditions. • To Manage and extend the equipment life, including systems modernization.

The Generation Cost: 

The Generation Cost The variable overall cost =(The Plant Availability Factor ,Station Heat Rate , Specific Fuel Oil Consumption , Auxiliary Energy Consumption ). The Variable Cost, decides the competitiveness of the electric units in a generating pool.

The Generation Cost Reduction: 

The Generation Cost Reduction The kWh fuel cost = 70 % approx the variable overall cost . The Fuel cost components: The station Heat Rate (kcal/kWh). To reduce the variable cost through the heat rate improvement.

Heat rate: 

Heat rate Heat rate is the heat input (fuel) required per unit of power generated (kcal/kWh), for specific fuel being fired and specific site conditions. Station heat rate = Turbine cycle heat rate =-------------------------- x100 Boiler efficiency %

Objective: 

Objective To point out the causes and location of efficiency losses. Improve station heat rate.

LOSSES IN THERMAL POWER PLANT: 

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: 

1.Boiler losses Symptoms Boiler efficiency Exit gas temp high Excess air Causes 1.1.Moisture losses 1.2.Dry gas losses 1.3.Incomplete combustion 1.4.Radiation losses

1.1.Moisture losses: 

1.1.Moisture losses High moisture in air Tube leaks Coal quality

1.2.Dry losses: 

1.2.Dry losses Boiler casing air leakage Air pre heater leakage Incorrect fuel air ratio Fouled heat transfer surfaces

1.3.Incomplete Combustion: 

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: 

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: 

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: 

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.

PowerPoint Presentation: 

Leaking steam not contribution to power generation (in RED) 2.5.Cross section of turbine –showing efficiency loss due to leakage

3.Condensate / F W system losses: 

3.Condensate / F W system losses 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: 

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: 

5.Steam condition Firing conditions High super heater spray flow High re heater spray flow Inadequate heat transfer surface

6.Electrical auxiliary losses: 

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: 

7.Seam Auxiliary Losses Excessive soot blowing Decreased in BFP Turbine efficiency Low inlet steam temperature Excessive steam flow through vacuum pump/ejector Steam trap/vent leaking Excessive usage of steam coil

8.Fuel Handling: 

8.Fuel Handling Spillage from the belt/transport Measurement inaccuracies Coal pile erosion Wind erosion Water erosion Coal pile fire

9. Heat Losses: 

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: 

10.Cycle isolation Leakage from recirculation valves of BFP/CEP. Leakage through bypass valves. Leakage to condenser through high energy drains. Leakage to condenser through emergency control 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 HEAT RATE (210 MW ,KWU Turbine )-operator controllable parameters.: 

11.Impact of parameter deviation on HEAT RATE (210 MW ,KWU Turbine )-operator controllable parameters. SN PARTICULAR UNIT DESIGN PARAMETERS INCREASE OF HEAT RATE DUE TO DEVIATION IN KCAL/KWH MULTIPLICATION FACTOR 1 PARTIAL LOADING MW 210 24.7 PER 20 MW 1.235 2 MS PRESS KG/CM2 150 25.5 PER 20 KG/CM2 1.275 3 MS TEMP AT HPT INLET DEG C 535 7.5 PER 10 DEG C 0.75 4 HRH TEMP AT IPT INLET DEG 535 6.6 PER PER 10 DEG C 0.66 5 CONDENSER VACUUM mmHg 660 23.4 PER 10 mm Hg 2.34 6 FEED WATER TEMP DEG C 241 16 PER 20 DEG C 0.8 7 RH ATTEMP FLOW T/HR 0 6.4 PER 10 T/HR 0.64 8 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.

PowerPoint Presentation: 

.500 MW TURBINE CONTROLLABLE LOSSES 11.1

12.DM Water makeup: 

12.DM Water makeup Boiler tube leaks Excess deaerator venting to atmosphere Excess continuous blowdown Excess steam lost through condenser venting Valve packing leaks Pump seal leaks Steam leaks to atmosphere

Normative station heat rate: 

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 boiler feed pumps are electrically operated, the station heat rate shall be 40 Cal/kWh lower than the station heat rate indicated above. • New Coal based Stations – 1.065 x Design heat rate. – Prescribed maximum permissible design heat rate to discourage procurement of inefficient machines

Power plant efficiency: 

Power plant efficiency Sub critical - 34% Super critical- 37% Ultra super critical 41%

HEAT RATE OF TURBINE CYCLE UNIT-Kcal/KWH: 

HEAT RATE OF TURBINE CYCLE UNIT-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 Rate: 

Maximum Turbine Cycle Heat Rate Note – Prescribed maximum permissible heat rate to discourage procurement of inefficient machines

Example of 210 MW: 

Example of 210 MW Operating efficiency of unit is 37.5 %. Unit heat rate is 2305 Kcal/kwhr To produce 860 Kcal ( heat equivalent to one kwhr) ,2305 kcal heat has to supplied to 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)kcal LOSSES Produces One kwhr

Power plant efficiency: 

Power plant efficiency Sub critical - 34% Super critical- 37% Ultra super critical 41%

Section wise losses in a particular thermal power plant: 

Section wise losses in a particular thermal power plant

Major Reasons for Higher Gross Heat Rate in India: 

Major Reasons for Higher Gross Heat 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 poor insulation 10. Poor Performance of ESP lead to failure of ID fan and low availability. 11. High cooling water inlet temperature due to poor performance 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: 

Conclusion Only Improvements in the station Heat Rate, Specific Fuel Oil Consumption and Auxiliary Energy Consumption can make generating units competitive.

Less Emissions: 

Less Emissions As the heat rate decreases (heat rate improves), the amount of fuel for the same generation also goes down. Of course with less fuel burned, emissions (green house gases) are lowered.

THANKING YOU: 

THANKING YOU