What component of a boiler is usually the last stage for heat recovery?

The air heater is designed to recover heat from the flue gases and utilize it to preheat the combustion air entering the boiler. This component is typically positioned after other heat recovery systems, such as economizers and superheaters, which serve different functions within the heat recovery hierarchy.

The economizer captures residual heat from the flue gases to preheat the feedwater going into the boiler, improving efficiency. Superheaters are employed to increase the temperature of steam before it enters the turbine, enhancing the performance of steam systems. Reheaters, often found in regenerative cycles, reheat steam after it has done work in the turbine to maximize energy output.

In contrast, air heaters are strategically placed as the final step in the heat recovery process within the boiler system. By generating warmer combustion air, they improve overall boiler efficiency and reduce fuel consumption, making them a critical component in optimizing energy use. Therefore, selecting air heaters as the final heat recovery stage reflects their critical role in enhancing the overall thermal efficiency of the boiler system.