What is the purpose of the economizer on a boiler?

The economizer on a boiler serves the primary purpose of adding heat to the feed water before it enters the boiler. By transferring heat from the flue gases that exit the boiler to the incoming feed water, the economizer effectively raises the temperature of the feed water. This process improves the overall thermal efficiency of the boiler.

When the feed water is preheated, less energy is required from the boiler to reach the desired steam temperature, leading to reduced fuel consumption—though this is a result of its operation rather than the primary function of heat addition. Additionally, preheating the feed water helps in reducing thermal shock and enhances the lifespan of the boiler components. The economizer does not directly increase steam pressure or regulate exhaust gases, as those functions are handled by other components in the boiler system.