Question

What happens when too much excess air is supplied to the furnace in the process of combustion of coal?

(a) There is a gain in heat in the furnace

(b) No change occurs in the furnace

(c) There is loss in heat in the furnace

(d) The excess air escapes out

I have been asked this question by my school principal while I was bunking the class.

My doubt is from Efficiency of Combustion in chapter Fuels and Combustion of Engineering Chemistry II

Answer 1

Right answer is (c) There is loss in heat in the furnace

The explanation is: In ordinary furnaces, 50 to 100 % excess air is generally supplied. If the excess air is supplied above this amount, there is a loss of heat in the furnace. In such cases, the supply of air to the hearth is cut short or the rate of fuel supply is increased.