Which statement best describes the function of an economizer in a boiler system?

• A. It filters impurities from feedwater.
• B. It reduces emissions by cleaning exhaust.
• C. It reduces heat loss by condensing exhaust.
• D. It preheats feedwater using residual heat from flue gases, improving efficiency.

Answer: (D)

An economizer’s job is to recover heat from the hot exhaust gases and use it to preheat the incoming feedwater. By transferring residual heat to the water before it enters the boiler, the water requires less energy to reach steam, so less fuel is burned overall. This improves boiler efficiency and can lower fuel use and emissions.

The other ideas aren’t describing this device’s main function: filtering feedwater impurities is the role of water treatment equipment; cleaning exhaust refers to emissions control devices; and condensing exhaust to reduce heat loss is a different approach not typically what an economizer does.