A typical coal food power plant burns 270 metric tons of coal every hour to gene

Question

A typical coal food power plant burns 270 metric tons of coal every hour to generate 2 7 times 10^6 MJ of electricity 1 metric ton = 1000 kg? 1 metric ton of coal has a volume of 1.5 m^3 The heat of combustion is 28 MJ/kg Assume that all heat is transferred from the fuel to the boiler and that at the work done in spinning the turbine is transformed Into electrical energy Suppose the coal is piled up in a 9 0 m times 14 m room How tal must the pile be to operate the plant for one day? Express your answer using two significant figures What is the power plant's thermal efficiency?

Explanation / Answer

a) Mass of coal needed for one day = 270 x 1000 x 24 = 6480000 kg

Volume of coal = mass/density = 6480000/1500 = 4320m3

Volume of coal = length x width x height = 9 x 14 x height = 4320

Height of pile = 4320/126 = 34.28 m

(b) Thermal energy released by combustion of coal per hour = mass x heat of combustion

= 270 x 1000 x 28 = 7560000 J

Thermal power released by combustion of coal = energy/time

= 7560000/3600 = 2100 MW

Thermal efficiency = electrical power/thermal power x 100

= 36.6 %

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