How to reduce oxides in the gas burner

After the fuel and air mixture enters the furnace, the temperature of the mixed airflow rises quickly due to convection and radiation heating of the surrounding high-temperature flue gas. When the ignition temperature is reached, the fuel begins to burn, and the temperature rises sharply to a level close to the adiabatic temperature. At the same time, due to 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. The nitrogen content in the gas burner is low, so fuel-type NOx is not its main control type. Thermal NOx refers to the oxidation of N2 in the combustion air at high temperature to generate NOx. The formation mechanism of thermal NOx generally adopts the Teredovich mechanism: when the temperature is below 1500℃, the amount of thermal NOx generated is very small; when it is above 1500℃, the reaction rate 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 some high-temperature areas, more NOx will be generated in these areas, which may play a key role in the NOx generation in the entire combustion chamber. Rapid NOx When hydrocarbon fuels are burned and the fuel is rich, the reaction zone will quickly generate NOx. In the actual combustion process, various factors change independently, and many parameters are constantly changing. Even the combustion of simple gas fuels must go through the mixing of fuel and air, combustion to generate flue gas, until it 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. It can be seen that the flame temperature distribution in the furnace is actually uneven.

Usually, the temperature at a certain distance from the burner outlet is very high, and the temperature before and after it is low, that is, there is a partial high-temperature area. Because the temperature of this area is much higher than the average temperature level in the furnace, it has a great influence on the NOx generation: the higher the temperature, the more NOx is generated. Therefore, in the furnace, in order to suppress the generation of NOx, in addition to lowering the average temperature in the furnace, it is also necessary to try to make the temperature in the furnace evenly distributed to avoid local high temperatures.