A steam generator comprises a boiler drum, a super heater, an economizer and an air preheater. The feedwater enters the economizer at 140oC and leaves as saturated liquid. Air is preheated from a temperature of 25oC to 250oC. Steam leaves the boiler drum (evaporator) at 60 bar, 0.98 dry and leaves the super heater at 450oC. When using coal with a calorific value of 25.2 MJ/kg, the rate of evaporation is 8.5 kg steam per kg coal and the air fuel ratio is 15:1 by mass. Neglecting heat losses and pressure drops, estimate the heat transfer per kg fuel in each component and the efficiency of the steam generator.
What are the percentages of the total heat absorption taking place in the economizer, boiler drum and the superheater, respectively? Assume cp of air and water as 1.005 kJ/kg K and 4.2 kJ/kg K, respectively