According to the principle of reducing nitrogen, there are currently four types of low-nitrogen burners: stage-combustion low-nitrogen burners, dense-lean low-nitrogen burners, self-recirculating low-nitrogen burners, and split flame-type low-nitrogen burners.
The first is the stage combustion type low-nitrogen burner, this kind of burner mainly uses the over-rich combustion method to reduce the combustion temperature and oxygen concentration to achieve the purpose of suppressing NOx. The fuel phase combustion type low NOx burner can reduce the amount of NOx produced, mainly because it organizes the aerodynamic working conditions and the mixing of fuel and air. Swirl blades are installed at the exit of the combustor to achieve a certain swirling intensity. The fuel is sprayed to the inner surface of the swirling layer to make the fuel, primary air and part of the secondary air evenly mixed to form a fuel-rich combustion zone; The unburned combustibles in the rich zone are then mixed with the high-speed outer airflow to form a fuel-light combustion zone, and finally the combustion process is completed. This combustion method is different from the two-stage combustion mentioned above. In the fuel-rich zone, due to the high-temperature flue gas recirculation, the flame temperature is lower and the air is insufficient, so it can not only suppress the temperature-type NOx, but also reduce the fuel-type The amount of NOx generated, because the entire flame is surrounded by the outer swirling airflow, the smoke and NO generated in the fuel-rich zone will continue to burn out when passing through the fuel-light zone. This kind of burner can reduce the NOx concentration by about 50%.
Then there is the rich-lean type low-nitrogen burner. The principle of the rich-lean type low-nitrogen burner is to make part of the fuel overburn and the other part of the fuel burns too lightly. Due to the large amount of air, the combustion temperature will inevitably decrease, thereby reducing the temperature-type NOx. This kind of combustion will "deviate from combustion" or "non-chemically equivalent combustion." The upper part of the thick and thin burner is the over-dilute burner, and the lower part is the over-rich burner. The air used by the two burners is divided equally, and the fuel is distributed according to the upper 22%-40% and the lower 78%-60%. If the deviation ratio is too large, soot and NO will increase. Deviation-combustion Y-type fuel injectors that achieve dense and light combustion on a nozzle are called self-deviation-combustion fuel nozzles. This kind of fuel nozzle can be arranged in two ways, namely, the large and small nozzles are arranged for communication and the upper part is a small nozzle, and the lower part is a large nozzle. The large nozzle achieves over-rich combustion and the small nozzle is too light. Compared with general nozzles, NOx production can be reduced by 20% to 40%.
