Five hundred megawatts of electrical power (500 MWe) 3 is to be generated in the

Question

Five hundred megawatts of electrical power (500 MWe)3 is to be generated in the present facility. Coal with properties given in Table CS 9.1 is fed at 25°C to a furnace where it is burned with 15% excess air. During combustion of the coal, sulfur reacts to form SO2 and a negligible amount of sulfur trioxide (SO3), while carbon and hydrogen are oxidized completely to CO2 and H2O. Essentially all of the nitrogen in the coal leaves the furnace as N2.4The ash in the coal leaves the furnace in two streams: 80% leaves as fly ash in the furnace flue gas, and the remainder leaves the furnace as bottom ash at 900°C.

Moisture: 4.80 kg/100 kg dry coal

HHV: 30,780 kJ/kg dry coal (see Section 9.6a)

Dry coal: Cp 1.046 kJ/kg C

Ash: Cp 0.921 kJ/kg C

At what rate is heat removed from the furnace? Assuming that all of the heat removed from the furnace is used to generate steam (i.e., none is lost to the surroundings), estimate the rate of steam generation in the power cycle.

Explanation / Answer

= Total Electricity produced = 500 MW

Coal HHV = 30780 KJ/Kg dry coal

Therefore.Coal used to produce Electricity = 500*10^6/(30780*10^3) =16.24 Kg/s

Total Heat produced per second = 16.24*30780 =499867 KJ/s

Latent heat of steam = 2268 KJ/kg

Therefore, Total steam produced = Total Heat generated/Latent heat of steam = 499867/2268 =220 Kg/s

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