Which component preheats combustion air for burners using hot flue gases?

The component that preheats combustion air for burners using hot flue gases is the air heater. This device utilizes the waste heat from the flue gases exiting the boiler to warm up the incoming combustion air. By preheating the air, the air heater increases the efficiency of the combustion process, allowing for better fuel utilization and reducing the overall energy needed for combustion. This results in improved boiler performance and lower emissions.

In contrast, an economizer is designed to recover heat from the flue gases to preheat the feedwater before it enters the boiler, while a superheater raises the temperature of steam beyond its saturation point. The windbox is a component that distributes the air to the burners but does not involve preheating. The air heater plays a crucial role in optimizing energy use within the combustion system, contributing significantly to the overall thermal efficiency of the boiler system.