Question

Why pre-heater air and the tempered air are introduced in the pulverizer of ball mill?

(a) To carry the ash out

(b) To increase the combustion rate

(c) To carry pulverized coal

(d) To dry the coal by removing the moisture

I got this question by my college director while I was bunking the class.

My question is from Pulverised Mills topic in chapter Steam Power Plant of Energy Engineering

Answer 1

Correct choice is (c) To carry pulverized coal

The best explanation: A mixture of tempering air and hot air from pre-heater is introduced in the pulverizer. These streams of air carry the pulverized coal and pass through the classifier. The over-sized particles are thrown out of the air stream in the classifier and fine material is passed to the burner through exhaust fan.