Question

What is done when there is requirement for more coal in the ball and race mill?

(a) The primary air flow is increased

(b) The combustion intensity is reduced

(c) The secondary air flow sucks out the light coal particles

(d) The hopper is fully opened

I have been asked this question in a job interview.

My question is taken from Pulverised Mills in section Steam Power Plant of Energy Engineering

Answer 1

Right choice is (a) The primary air flow is increased

Easiest explanation: When there is requirement for more coal, the primary air flow is increased automatically and its higher velocity in the mill carries additional coal in the furnace. This action reduces the amount of coal in the pulverizer and decreases the pressure drop, causing the feeder controller to supply more coal.