What is the effect of excess air in combustion?

What is the effect of excess air in combustion?

Too much excess air leads to lower flame temperature. That means less heat gets into the system. Also, excess air must heat up to flue gas temperature, which consumes extra energy.

What affects combustion efficiency?

Combustion efficiency is affected by fuel type, bed temperature, gas velocity, and excess air levels. Combustion efficiency increases with fuel volatile matter content and bed temperature. This is believed to be due to an increase in CO and hydrocarbon emissions as the excess air level increases to higher levels [23].

How can combustion efficiency be improved?

An often stated rule of thumb is that boiler efficiency can be increased by 1% for each 15% reduction in excess air or 40°F reduction in stack gas temperature. Operating your boiler with an optimum amount of excess air will minimize heat loss up the stack and improve combustion efficiency.

What is meant by excess air what is the significance of excess air?

Excess air ensures that there is enough air for complete combustion. Excess air is expressed as a percentage of theoretical air required. Thus, 10% excess air indicates that 110% total air is being supplied. In boiler operation, excess air represents a heat loss.

Why do we use excess air?

Excess air increase the amount of oxygen to the combustion and the combustion of fuel. The combustion efficiency increases with increased excess air – until the heat loss in the excess air is larger than the heat provided by more efficient combustion.

What is meant by combustion efficiency?

Combustion efficiency is a measure of how effectively the heat content of a fuel is transferred into usable heat. The stack temperature and flue gas oxygen (or carbon dioxide) concentrations are primary indicators of combustion efficiency.

What is combustion efficiency?

How do you measure combustion efficiency?

The ultimate thermal efficiency of the appliance is determined by dividing the heat output rate of the appliance by the rate of fuel input. During the combustion process, all furnaces that operate with the same combustion efficiency will produce the same amount of heat with the same fuel input.

What is definition of excess air?

Excess air means that amount of air supplied in addition to the theoretical quantity necessary for complete combustion of all fuel or combustible waste material present.

How do you reduce excess air?

The simplest method to reduce excess air of an atmospheric burner is to damper (reduce) the combustion air flow rate to the point that CO emissions are near the upper limit acceptable for flue gas emissions. This measure is suitable only if the burner operates at almost constant heat output.

How does excess air affect the combustion of fuel?

Excess air increase the amount of oxygen to the combustion and the combustion of fuel. The combustion efficiency increases with increased excess air – until the heat loss in the excess air is larger than the heat provided by more efficient combustion.

Why is combustion efficiency important to the environment?

Optimizing boilers efficiency is important to minimize fuel consumption and unwanted excess to the environment. Sponsored Links. To ensure complete combustion of the fuel used combustion chambers are supplied with excess air. Excess air increase the amount of oxygen to the combustion and the combustion of fuel.

Why is the efficiency of a boiler important?

Optimizing boilers efficiency is important to minimize fuel consumption and unwanted excess to the environment. To ensure complete combustion of the fuel used combustion chambers are supplied with excess air. Excess air increase the amount of oxygen to the combustion and the combustion of fuel.

Which is excess air achieves the highest possible efficiency?

Typical excess air to achieve the highest possible efficiency for some common fuels: Carbon dioxide – CO2 – is a combustion product and the content of CO2 in a flue gas is an important indication of the combustion efficiency.