A boiler produces 6 tonnes/hour of steam at a pressure of 1.8 MPa and a temperature of 250ºC. Feedwater enters at a temperature of 39ºC. At exit from the economizer part of the boiler the temperature is 72ºC. At exit from the evaporator part of the boiler the steam is 90 % dry. Energy is supplied by 650 kg of coal per hour, which has a calorific value of 36 MJ/kg. The A/F ratio is 25 : 1. The temperature of the flue gas at entry to the economizer part of the boiler is 430ºC. The average specific heat at constant pressure of the flue gas in the economizer is 1045 J/kg.K. 4.1 Calculate the efficiency of the boiler. [70.5 %] this one is the answer 4.2 Draw up an energy balance, on a kJ/kg coal basis, with percentages of the total energy supplied. [economizer 3.6 %, evaporator 59 %, superheater 8 %, other 29.4 %]
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questionn 4
4. A boiler produces 6 tonnes/hour of steam at a pressure of 1.8 MPa and a temperature of 250ºC.
Feedwater enters at a temperature of 39ºC. At exit from the economizer part of the boiler the
temperature is 72ºC. At exit from the evaporator part of the boiler the steam is 90 % dry.
Energy is supplied by 650 kg of coal per hour, which has a calorific value of
36 MJ/kg. The A/F ratio is 25 : 1. The temperature of the flue gas at entry to the economizer
part of the boiler is 430ºC. The average specific heat at constant pressure of the flue gas in
the economizer is 1045 J/kg.K.
4.1 Calculate the efficiency of the boiler. [70.5 %] this one is the answer
4.2 Draw up an energy balance, on a kJ/kg coal basis, with percentages of the total energy
supplied. [economizer 3.6 %, evaporator 59 %, superheater 8 %,
other 29.4 %]
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