2nd Class Power Engineering (2B2) Practice Exam

Economizers enhance boiler efficiency primarily by recovering waste heat from the flue gases before they are expelled into the atmosphere. In a typical boiler system, flue gases carry away significant amounts of heat as they exit the combustion chamber. An economizer captures this waste heat and uses it to preheat the feedwater entering the boiler.

By increasing the temperature of the feedwater, the economizer reduces the amount of heat energy that the boiler must generate from combustion to reach the desired steam temperature or pressure. This leads to lower fuel consumption, as less fuel is needed to heat the water to the necessary temperatures. Consequently, this not only improves the overall thermal efficiency of the boiler but also reduces operational costs and greenhouse gas emissions.

In contrast, other methods, such as adjusting air supply or increasing water pressure, do not directly contribute to the recovery of waste heat. These mechanisms may optimize combustion or system performance but do not capitalize on the energy available from flue gases as effectively as an economizer does.