What type of air is used to regulate the efficiency of combustion?

Secondary air is used primarily for the combustion process in a boiler system to enhance the efficiency of combustion. Its primary function is to support the burning of fuel by providing additional oxygen necessary for complete combustion. When the fuel-air mixture is not enough to reach optimal combustion temperatures or to consume all the fuel effectively, secondary air is introduced to facilitate this.

By ensuring that a sufficient amount of secondary air is available, the combustion process becomes more efficient, leading to lower emissions of unburnt fuel and improved thermal efficiency. This type of air is critical for achieving complete combustion, minimizing pollutants and maximizing the energy output from the fuel being used.

While primary air is the initial amount of air mixed with the fuel, and tertiary air can be used in more advanced combustion setups for further enhancement, secondary air specifically addresses the necessity of enhancing combustion after the initial phase. Thus, its role is vital in maintaining an optimal efficiency level in the combustion process.