Why are economizers used on boilers?

Economizers are utilized on boilers primarily to enhance energy efficiency by heating the feedwater. By capturing waste heat from the flue gas that would otherwise be expelled into the atmosphere, economizers preheat the water before it enters the boiler. This process reduces the amount of fuel required to raise the temperature of the feedwater to the needed boiler operating conditions, which can lead to lower fuel consumption and operating costs while increasing overall thermal efficiency. Additionally, preheating the feedwater can help reduce thermal shock to the boiler, extending its lifespan and improving reliability.

While reducing emissions can be a secondary benefit of improved efficiency, the primary function of an economizer is to heat feedwater effectively before it is used in the steam generation process. Increasing pressure does not directly involve economizers, as they focus on temperature and energy recovery rather than pressure management. Cooling exhaust gases is typically not a function of an economizer, as that would not contribute to the efficiency of the boiler system but rather might indicate a need for a different type of heat exchange system.