This document discusses heat rate audits in thermal power plants. It aims to identify causes of efficiency losses that increase heat rate. Some key points: - Heat rate is the amount of heat input (fuel) required per unit of power generated and impacts generation costs. Lower heat rates reduce costs. - Losses occur in the boiler, turbine, condenser/feedwater systems, circulating water system, and from electrical/steam auxiliaries. - Common causes of higher heat rates include incomplete combustion, turbine erosion, condenser tube fouling, and electrical auxiliary inefficiencies. - Tracking plant parameters and conducting monthly performance tests can identify losses and guide improvement efforts to lower heat rates.

1. HEAT RATE AUDIT IN
THERMAL POWER PLANT
SHIVAJI CHOUDHURY

2. 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.

3. 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.

4. 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.

5. 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 %

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

7. 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

8. 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

9. 1.1.Moisture losses
 High moisture in air
 Tube leaks
 Coal quality

10. 1.2.Dry losses
 Boiler casing air leakage
 Air pre heater leakage
 Incorrect fuel air ratio
 Fouled heat transfer surfaces

11. 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

12. 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

14. 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

15. 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.

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

17. 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

18. 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

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

20. 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

21. 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

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

23. 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.

24. 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.

25. 11.Impact of parameter deviation on HEAT
RATE (210 MW ,KWU Turbine )-operator
controllable parameters.
SN PARTICULAR UNIT DESIGN
PARAMETERS
INCREASE in HEAT
RATE DUE TO
DEVIATION from
design parameters
(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.

26. .500 MW TURBINE CONTROLLABLE
LOSSES
11.1

27. 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

28. 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

29. Heat Rate Monitoring
 Daily Heat Rate Calculation by deviation
method & Identification Of Heat Rate Losses
 Monthly Performance Test (as per ASME
PTC/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

30. 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

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

32. 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

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

34. Section wise losses in a particular
thermal power plant

35. 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

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

37. 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.

38. THANKING YOU
Heating
By LP heaters
Heating
By HP heaters
LP
Expansion