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A typical coal-fired power plant burns 350 metric tons of coal every hour to gen

ID: 1419431 • Letter: A

Question

A typical coal-fired power plant burns 350 metric tons of coal every hour to generate 730 MW of electricity. 1 metric ton= 1000 kg. The density of coal is 1500 kg/m3 and its heat of combustion is 28 MJ/kg. Assume that all heat is transferred from the fuel to the boiler and that all the work done in spinning the turbine is transformed into electrical energy.

Part A

Suppose the coal is piled up in a 15 m × 15 m room. How tall must the pile be to operate the plant for one day?

Part B

What is the power plant's thermal efficiency?

Explanation / Answer

A)

mass required per hour = 350 mt

mass for 24 hours = 350*24 = 8400000 kg

density of coal = 1500 kg/m3

=> vol of coal = 8400000/1500 = 5600 m3

height of coal stack = 5600 / (15*15) = 24.89m

B)

B. 1 kg coal produces = 28MJ / kg

total energy supplied by coal in 1 hour = 28 * 350 * 1000 Mj

= 9800000 MJ/hour

energy produced by plant = 730 * 60 * 60 MJ/hour

= 2628000 MJ/hour

efficiency = (output/input) x 100

=(2628000 / 9800000) x 100

= 26.81%

power plant's thermal efficiency =26.81%

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