Question

What is the function Air heater in the boiler?

(a) Preheat the air before entering the boiler

(b) Recover the heat from flue gas

(c) Heating of economizer tubes

(d) Reheat the gas coming out of economizer

The question was posed to me by my school principal while I was bunking the class.

My question is taken from Boiler Mounting Accessories topic in division Steam Generators & Accessories of Energy Engineering

Answer 1

Correct answer is (b) Recover the heat from flue gas

To explain: Function of air preheater is to recover the heat of a portion of exhaust flue gases before the flue gases enter the chimney. It is places along the passage of the exhaust flue gases in between the economizer and the chimney.