2. Get Idea about
Different Temperature
and Pressure Ratings
and their effects on
Power Plants
Economics
Calculation of Fuel
Cost per Unit of
Electricity Produced
3. BOILER CLASSIFICATIONS
Mentioning Two circulating Fluidized Bed Boilers of
same capacity having different temperatures and
Pressures ratings
Boiler-1: High Temperature and Pressure CFBC
Steam Generating Capacity : 130 Tons/ Hour
Rated Evaporation Pressure : 8.43 Mpa (84.3
Bar)
Rated Evaporation Temperature : 515 C
4. Boiler-2: Medium Temperature and Pressure
CFBC
Steam Generating Capacity: 2 x 65 Tons / Hour
Rated Evaporation Pressure: 3.82 Mpa ( 38.4
Bar)
Rated Evaporation Temperature: 450 C
5. At what temperature and Pressure limits boilers are
classified whether they are
i. Low temperature and Low Pressure
ii. Medium temperature and Medium Pressure
iii. High temperature and High Pressure
Advantages and Disadvantage associated with both
sort of configuration for a 25 MW Power Plant
6. CLASSIFICATION ON THE BASIS OF PRESSURE
As per ASME code, Boilers are classified into two basic
classes
Low Pressure Boiler: Pressure is below 15 Psi
High Pressure Boiler: Pressure is above 15 Psi.
High Pressure Boilers are further classified in to Sub
Critical, Supercritical and Ultra Super Critical
Sub-Critical (Operated around 19 Mpa):
Example: 170 bar, 540 C, Efficiency: 38 %
Super-Critical (Operated above 22.1 Mpa):
Example: 250 bar, 600/615 C, Efficiency: 42 %
Ultra Super-Critical:
Example: 300 bar, 615/630 C, Efficiency: 44 %
7. POWER PLANT USING BOTH CONFIGURATIONS
25 MW Power Plants Using Boiler - 1
Steam in Kg / kWh around 3.9 to 4.0 at 6000 kcal / kg of
Coal with 1 % Sulphur
Net Thermal Efficiency of around 24 %
Have high Cost of Boiler and Turbine due to high pressure
Have long pay back opportunities
25 MW Power Plants Using Boiler – 2
Steam in Kg / kWh around 4.5 to 5.0 at 6000 kcal / kg of
Coal with 1 % Sulphur
Net Thermal Efficiency around 22.5 to 22.8 %
Have low Cost of Boiler and Turbine due to low pressure
Better control over low electrical load equipments
Low initial Cost
8. COST / kWh ?
Plant Capacity : 25 MW
Auxiliary Consumption: 9 % of the rated
Efficiency:
Boiler : 88 %
Turbine : 35 %
Other : 78.5 %
i. GCV of Coal : 6500 kcal / kg (Foreign Coal)
ii. GCV of Coal : 4600 kcal / kg (Local Coal)
9. FOR FOREIGN COAL
Calorific Value of Coal:
3600 kJ = 1 kWh = 856 kcal
6500 kcal / kg = 27336 kJ / kg
Net Thermal Efficiency:
Efficiency = 0.88 x 0.35 x 0.78
= 24 %
Heat Rate:
Heat Rate = 3600 / Efficiency
Heat Rate = 3600/ 0.24 = 15000 kJ/ kWh
14. Cost/ kWh: (For Local Coal)
1.0 Ton = Rs 10,000. 00
19.4 Tons = Rs 194, 000.00
Energy Produced = 25, 000 kWh
Auxiliary Power = 9 % of 25, 000 kWh
Net Available Power = 22,750.00 kWh
Cost / kWh = Net Units available / Cost of
Coal
= 22, 750.00/ 194, 000.00
Cost / kWh = Rs 8.53
15. LOCAL Vs FOREIGN COAL
Cost / kWh for Foreign Coal: Rs 10.244
Cost / kWh for Local Coal: Rs 8.53
Difference = 10 . 244 – 8.53
= Rs 2.714 / kWh
If Local Coal is used then money saved in
Hour = 2.714 x 22750 = Rs 61,743.50
Day = 61,743.50 x 24
= 1.481844 million Rupees
Year = 270 x 1.481844 = 400.1 million Rupees