However, the nitrogen content in the gas is low, therefore, the fuel type NOx is not the main control type.

Thermal NOx means that N2 in the combustion air is oxidized at high temperature to produce NOx. About the thermal NOx generation mechanism generally adopts the mechanism of Gedredovic: when the temperature is lower than 1500 ℃, the amount of thermal NOx generation is very small; When the temperature is higher than 1500 ℃, the reaction speed will increase by 6~7 times for every 100 ℃ increase in temperature. In the actual combustion process, because the temperature distribution in the combustion chamber is uneven, if there are local high-temperature regions, more NOx will be generated in these regions, which may play a key role in the formation of NOx in the entire combustion chamber.

Rapid NOx In the case of hydrocarbon fuel combustion and rich fuel, the reaction zone will quickly produce NOx. In the actual combustion process, various factors are changed separately, and many parameters are in constant change. Even the most simple combustion of gas fuel will undergo the mixing of fuel and air to produce flue gas until it finally leaves the furnace. The temperature of the furnace, the degree of mixing of fuel and air, the residence time of flue gas in the furnace, and other parameters that have a greater impact on NOx emissions are constantly changing.

After the mixture of fuel and air enters the furnace, the temperature of the mixture flow rises rapidly due to the convection and radiation heating of the surrounding high-temperature flue gas. When the ignition temperature is reached, the fuel starts to burn, and the temperature rises sharply to near the adiabatic temperature level. At the same time, due to the convection and radiation heat exchange between the flue gas and the surrounding medium, the temperature gradually decreases until it is the same as the temperature of the surrounding medium, that is, the flue gas flows through the entire furnace while cooling. It can be seen that the flame temperature distribution in the furnace is actually non-uniform. Generally, the temperature at a certain distance from the burner outlet is the highest, and the temperature before and after it is lower, that is, there is a local high temperature zone. Since the temperature in this zone is much higher than the average temperature level in the furnace, it has a great influence on the amount of NOx generated: the higher the temperature, the more NOx is generated. Therefore, in order to suppress the generation of NOx in the furnace, in addition to lowering the average temperature in the furnace, it is necessary to make the temperature distribution in the furnace uniform and avoid local high temperature.