At present, low nitrogen burners can be roughly divided into the following categories according to the principle:
1. Stage burner -------The stage burner designed according to the staged combustion principle makes the fuel and air mixed and burned in stages. Since the combustion deviates from the theoretical equivalent ratio, it can reduce the generation of nitrogen.
2. Self-recirculation burner-------One is to use the pressure head of combustion air to suck back part of the combustion smoke, enter the burner, and mix it with air for combustion. Due to the flue gas recirculation, the heat capacity of the combustion flue gas is large, the combustion temperature is reduced, and the NOx is reduced. Another self-recirculating burner is to directly recirculate part of the flue gas in the burner and add it to the combustion process. This kind of burner has dual effects of suppressing nitrogen oxides and saving energy.
3. Rich-lean burner-------The principle is to make part of the fuel burn too richly, and the other part burn too lightly, but the overall air volume remains unchanged. Since the two parts are burned at a deviation from the stoichiometric ratio, the NOx is very low. This kind of combustion is also called deviation from combustion or non-stoichiometric combustion.
4. Split flame type burner-------The principle is to divide a flame into several small flames. Due to the large heat dissipation area of the small flames and the low flame temperature, the "thermal reaction NO" is reduced. In addition, the small flame shortens the residence time of oxygen, nitrogen and other gases in the flame, and has a significant inhibitory effect on "thermal reaction NO" and "fuel NO".
5. Mixing-promoting burner -------- The residence time of flue gas in the high temperature area is one of the main factors affecting the amount of NOx generated. Improving the mixing of combustion and air can reduce the thickness of the flame surface. When the combustion load remains unchanged, the residence time of flue gas in the flame surface, that is, the high temperature area, is shortened, thereby reducing the amount of NOx produced. The mixing-promoting burner is designed according to this principle.
6. Low-nitrogen pre-chamber burner --------- The pre-chamber is a high-efficiency, low-nitrogen staged combustion technology developed and researched in my country in the past 10 years. The pre-chamber is generally composed of primary air (or secondary secondary air) and fuel injection system, the fuel and the primary air are quickly mixed, and a fuel-rich mixture is formed in the primary combustion zone of the pre-combustion chamber. Due to the lack of oxygen, only part of the fuel is burned. Volatile matter is precipitated in the flame zone, thereby reducing the formation of NOx.