Question

Why does burnt gases with content of N2, CO2, H2, O2 and H2O re-enter the boiler in overfeed system?

(a) To dismiss the ash content in the gases formed

(b) Due to incomplete burning

(c) For complete removal of moisture

(d) To complete the burn the coal

The question was asked in final exam.

Query is from Principle of Stoker topic in chapter Steam Power Plant of Energy Engineering

Answer 1

Right answer is (b) Due to incomplete burning

The explanation is: The burnt gases re-enter the boiler containing N2, CO2, O2, H2O and CO if the burning is incomplete. During incandescence, the fuel is continuously loses its carbon by oxidation until only the ash remains.