What is the primary function of an air preheater in a steam generation system?

The primary function of an air preheater in a steam generation system is to heat the combustion air entering the boiler, thereby increasing efficiency. When the combustion air is preheated, it allows the fuel to burn more efficiently, which enhances the overall thermal efficiency of the steam generation process. This preheating reduces the amount of fuel needed to achieve the desired energy output, leading to economical operation and reduced emissions.

Heating the combustion air before it enters the boiler not only improves combustion efficiency but also helps to maintain a more stable and optimal temperature within the combustion chamber. This contributes to better heat transfer within the system and supports the overall performance of the boiler by maximizing output while reducing fuel consumption.

In contrast, other functions suggested in the options do not align with the primary role of an air preheater. For example, cooling the combustion air or eliminating excess steam are not typical functions associated with air preheating. Similarly, measuring temperature is a separate function that involves sensors and instrumentation rather than the main purpose of enhancing combustion efficiency.