In which component is combustion air for burners preheated by hot flue gases?

The correct answer is that combustion air for burners is preheated by hot flue gases in the air heater. An air heater is designed specifically to elevate the temperature of the air entering the combustion system. By doing this, the efficiency of combustion is enhanced as preheated air can facilitate more complete combustion, resulting in better energy performance and reduced fuel consumption.

In the context of combustion systems, instructors often cover how preheating the combustion air leads to improved operational efficiencies and helps in maintaining the desired temperature profiles within burners, ultimately supporting more effective combustion processes.

The windbox, while related to air distribution for the burners, does not serve to preheat the incoming air with flue gases; instead, it directs air into the combustion system. The superheater, on the other hand, is involved in raising the temperature of steam, which is not directly related to the combustion air. Lastly, the economizer recovers heat from flue gases to preheat water or feedwater rather than air. This differentiation is essential to understanding the roles of each component in a combustion system.