When an air heater is used in a boiler, what is its primary function?

The primary function of an air heater in a boiler system is to increase the efficiency of the boiler. Air heaters accomplish this by preheating the incoming combustion air using the exhaust gases that leave the boiler. By warming the air before it enters the combustion chamber, the air heater allows for more efficient combustion of the fuel.

When combustion air is preheated, it requires less fuel to achieve the same temperature and pressure within the boiler. This leads to a reduction in fuel consumption and, consequently, a decrease in overall operating costs. Furthermore, as the boiler operates more efficiently, it can produce more steam or hot water for the same amount of fuel, resulting in improved system performance.

Although other options might be relevant in broader contexts, they do not directly reflect the primary role of an air heater. For instance, reducing emissions is a beneficial outcome of improved efficiency, as more complete combustion typically results in lower emissions, but it is not the air heater's direct function. Similarly, filtering impurities pertains more to the handling of combustion products rather than the heater’s operational purpose, and lowering steam temperature is not consistent with the intended function of an air heater. The key takeaway is that the air heater is fundamentally integrated into systems to enhance boiler efficiency through the effective use of