The position of the burner is very important in the equipment of low nitrogen gas steam boiler. The burner determines whether the fuel combustion process can achieve complete combustion, so the performance of the burner must be considered to reduce the amount of NOx generated. Based on the degree of control of the amount of NOx produced by the burner, we divide the low nitrogen burner into the following 6 types:
1. Stage burner
The stage burner designed according to the principle of staged combustion enables the fuel and air to be combusted in stages. Since the combustion deviates from the theoretical equivalent ratio, the generation of NOx can be reduced.
2. Self-recycling burner
One is to use the pressure head of the combustion air to suck back part of the combustion flue gas, enter the burner, and mix with the air for combustion. Due to the recirculation of the flue gas, the heat capacity of the combustion flue gas is large, the combustion temperature is reduced, and NOx is reduced.
Another type of self-recycling burner is to directly recirculate part of the flue gas in the burner and add it to the combustion process. This burner has the dual effects of inhibiting nitrogen oxides and saving energy.
3． Light and light burner
The principle is that part of the fuel is burned too richly, and the other part of the fuel is burned too lightly, but the air volume remains the same. Because both parts burn at a deviation from the stoichiometric ratio, the NOx is very low. This kind of combustion is also called off-combustion or non-stoichiometric combustion.
4． Split flame burner
The principle is to divide a flame into several small flames. Due to the large heat dissipation area of the small flame and the lower flame temperature, the "thermal reaction NO" decreases. In addition, the small flame shortens the residence time of gases such as oxygen and nitrogen in the flame, and has a significant inhibitory effect on "thermal reaction NO" and "fuel NO".
5. Mixing promotion burner
The residence time of the flue gas in the high temperature region 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. Under the condition of constant combustion load, the flue gas is at high temperature on the flame surface The residence time in the zone is shortened, which reduces the amount of NOx produced. Mixing promotion burners are designed according to this principle.
6. Low NOx pre-combustion chamber burner
The pre-combustion chamber is a high-efficiency, low-NOx staged combustion technology developed and researched in China in the past 10 years. The pre-combustion chamber is generally composed of primary air (or secondary air) and fuel injection systems. Fuel and primary air are rapidly mixed. The primary combustion zone in the pre-combustion chamber forms a fuel-rich mixture. Due to lack of oxygen, only part of the fuel is burned. The fuel precipitates volatiles in the primary flame zone where the oxygen is depleted and the flame temperature is low, thereby reducing the generation of NOx.
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