A power plant producing 120 MW of electricity has steam condition at boiler outlet as 100 bar, 500 C and the condenser pressure is 0.1 bar. The boiler efficiency is 90%. The boiler consumes coal of calorific value 25.7 MI/kg. The feedwater temperature at boiler inlet is 160 C. The steam generator has risers in the furnace wall 40 m high and unheated downcomers. The quality at the top of the riser is 8% and a minimum exit velocity of mixture leaving the riser and entering the drum is required to be 2 m/s. The risers have 60 mm o.d. and 3 mm wall thickness. Neglecting any pressure drop and heat loss, as well as the pump work, estimate 3.1 the steam generation rate, 3.2 the fuel burning rate, 3.3 the evaporation factor, 3.4 the pressure head available for natural circulation, the circulation ratio. 3.5 [m. = 93.385 kg/s; mr = 10.898 kg/s; EE-8.57; Ap=0.6433 bar; CR = 12.5] A boiler produces 6 tonnes/hour of steam at a pressure of 1.8 MPa and a temperature of 250C. Feedwater enters at a temperature of 39C. At exit from the economizer part of the boiler the temperature is 72C. 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 430C. 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. 4.2 [70.5 %] 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%)