What is air over the stoichiometric amount of air called?

When the amount of air supplied for combustion exceeds the stoichiometric requirement, it is termed "excess air." The stoichiometric amount of air is the exact amount needed to burn a given amount of fuel completely without leaving any unburned fuel or excess oxygen. When more air than this optimal quantity is provided, it serves several purposes, such as ensuring complete combustion and improving the efficiency of the combustion process by diluting the exhaust gases.

Using excess air helps to reduce the formation of pollutants, such as carbon monoxide and unburned hydrocarbons, because the increased oxygen availability allows for a more thorough reaction with the fuel. However, too much excess air can lead to reduced efficiency, as it may cool down the combustion process and lower the flame temperature, causing more energy to be wasted.

In the context of combustion and energy systems, understanding the concept of excess air is crucial for optimizing the performance and emission characteristics of combustion systems, making it an essential detail in plant operations.