What is the function of an economizer in a boiler system?

• A. To store condensate.
• B. To generate electricity directly.
• C. To recover heat from flue gases to preheat feedwater, improving overall boiler efficiency.
• D. To remove particulates from flue gas.

Answer: (C)

An economizer is a heat-recovery device in a boiler system that uses the heat in the flue gases to preheat the incoming feedwater. By transferring heat from the hot exhaust to the cooler water returning from the condensate system, it raises the feedwater temperature before it enters the boiler. This means less fuel is needed to bring the water up to steam, which lowers stack losses and improves overall boiler efficiency. In other words, it makes use of energy that would otherwise go up the chimney.

The other options don’t fit this role: storing condensate is handled by the condensate return system, not the economizer; generating electricity directly is not what the economizer does (it doesn’t power a turbine); and removing particulates from flue gas is done by pollution-control devices like scrubbers or filters, not an economizer.