Question

What is done in the primary stage of the grinding in impact mill?

(a) Coal is reduced to fine granular state

(b) Coal is broken down in medium pieces

(c) Coal is dried up to remove the moisture content

(d) Coal is mixed up with the other state of fuel to improve the combustion efficiency

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

Asked question is from Pulverised Mills topic in portion Steam Power Plant of Energy Engineering

Answer 1

The correct answer is (a) Coal is reduced to fine granular state

To elaborate: The primary air fan induces flow of air through the pulverizer carrying the coal to the primary stage of grinding. In the primary stage of grinding, the coal is reduced to fine granular state by impact with a series of hammers and then into the final stage where pulverization is completed by attrition.