Which boiler component is used to recover heat from flue gases?

• A. Economizer
• B. Boiler drum
• C. Superheater
• D. Feedwater heater

Answer: (A)

Recovering heat from flue gases to preheat incoming feedwater is the key idea. An economizer sits in the path of the flue gases and acts as a heat exchanger that transfers heat from the hot exhaust to the feedwater before it enters the boiler. By raising the feedwater temperature, the boiler needs less fuel to reach the desired steam conditions, boosting overall efficiency and reducing fuel consumption and emissions.

The boiler drum is the vessel that separates steam from water; it doesn’t function as a heat-recovery exchanger from the flue gas. The superheater uses remaining heat to raise the temperature of already formed steam, which is about increasing steam quality rather than preheating feedwater. The feedwater heater preheats feedwater, but it typically uses steam or another heat source rather than directly using flue gas in the boiler’s exhaust path.