How does excess air affect boiler efficiency?

Excess air in a boiler system refers to the additional air supplied for combustion beyond what is theoretically necessary for complete fuel combustion. This situation impacts boiler efficiency primarily because it leads to increased fuel consumption. When more air than needed enters the combustion process, it results in colder combustion gases. This causes the heat generated by the fuel to be absorbed by the excess air rather than being effectively used to produce steam or heat.

As a result, the overall energy efficiency of the boiler decreases because more fuel must be burned to achieve the same output of steam or thermal energy. The excess air not only dilutes the combustion process, making it less efficient, but also carries away more heat energy in the flue gases. Consequently, this combination leads to increased fuel costs, diminishing the operational efficiency of the boiler system.

In contrast, optimizing combustion with the right amount of air is crucial for achieving maximum efficiency and minimizing fuel use, which is why the alternatives provided do not hold as the correct response in this context.