A steam power station uses 2 kg of coal per kWh of electrical energy generated. What is the calorific value of coal if the overall efficiency of the plant is 20%?

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MPPGCL JE Electrical 28 April 2023 Shift 3 Official Paper
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  1. 4300 kcal/kg
  2. 8600 kcal/kg
  3. 2150 kcal/kg
  4. 1075 kcal/kg

Answer (Detailed Solution Below)

Option 3 : 2150 kcal/kg
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Detailed Solution

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Concept

The efficiency of a coal is given by:

Let CV be the calorific value of coal in kcal/kg. The total energy input from n kg of coal:

Total Input Energy = n × CV

Calculation

Given, η = 20% = 0.2

Coal consumption = 2 kg per kWh

Output energy = 1 kWh = 860 kcal (since 1 kWh = 860 kcal of useful energy)

CV = 2150 kcal/kg

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