Calculate the overall efficiency, the heat rate [MW], and the total fuel rate [k

Question

Calculate the overall efficiency, the heat rate [MW], and the total fuel rate [kg/s] of a combined-cycle power plant (1) if no supplemental firing is used and (2) if 30% of the gas turbine fuel demand is additionally burned in the supplementary firing of the HRSG. The gas turbine plant and steam turbine plant thermal efficiencies are 37.5% and 26% [both based on lower heating value (LHV)], respectively. Assume that the combined-cycle power plant has an electrical power output of 380 MW and that the fuel HFO No.2 has the lower heating value of 43 MJ/kg.

Explanation / Answer

Efficiency = (860.4*100)/(Heat rate in kCal/kWh)
or
Efficiency = (860.4*4.18*100)/(Heat rate in kJ/kWh)

Ex 1: if heat rate is 2500 kCal/kWh, then efficiency is 34.416%

Ex 2: if heat rate is 9000 kJ/kWh, then efficiency is 39.96%

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