What are the three combustion methods of gas-fired boilers?

The fuel of a gas-fired boiler is gas such as natural gas, city gas, biogas and liquefied gas, etc. What kind of fuel the boiler burns is decided by an equipment called a burner. The boiler equipped with a gas-fired burner is called a gas-fired boiler. There are three methods of gas-fired boiler combustion as per technical characteristics of how the gas and air mix.

1. Diffusion combustion:

Gas and air mutually diffuse at the gas nozzle and are burning. The advantages are burning stably and with simple burner structure. However, the heated area is easy to be carbonized due to long flame, which is easy to produce incomplete combustion.

2. Premixed combustion:

A part of air and gas are premixed before combustion (coefficient of primary air surplus is between 0.2-0.8), and then being burned. The advantages are clear combustion flame, enhanced combustion, and high thermal efficiency. However, the combustion is unstable, and the control of the primary air and the composition of the combustion are relatively high. Gas-fired burners generally use this type of combustion.

3. Flameless burning:

The air required for fuel gas is evenly mixed with the fuel gas before burning. The primary air surplus coefficient is equal to the air surplus coefficient when the fuel is completely burned. There is no need to obtain oxygen from the surrounding air during the combustion process. When the mixture of fuel gas and air reaches the combustion zone, it can be burned instantly.