The measures that can be taken to suppress the generation of NOx include:
1. Reduce the peak temperature of the boiler and reduce the amount of coal powder in the combustion zone.
2. Reduce oxygen concentration (i.e. reduce excess air coefficient) and block some secondary air ducts.
3. To ensure the output of the boiler, some coal powder and air can be input from the upper part of the boiler, which controls the amount of combustion air in the central area of the combustion flame, shortens the residence time of combustion products in the high-temperature flame area, and avoids the coexistence of high temperature and high oxygen concentration.
4. Establish a reburning zone in the furnace, utilizing the hydrocarbon CHi generated during combustion in the main combustion zone and the incomplete combustion products CO, H2, C, and CnHm to reduce NO to N2.
80% to 85% of the fuel is fed into the main combustion zone, where it burns to generate NOx. 15% to 20% of the fuel is fed into the reburning zone, and the excess air coefficient in the reburning zone is less than 1.0（ α< 1.0), with a strong reducing atmosphere, the NOx generated in the main combustion zone is reduced; The reburning zone not only reduces the already generated NOx, but also suppresses the generation of new NOx; Supply a certain amount of air (called burnout air) in the burnout zone to ensure that the incomplete combustion products coming out of the reburning zone are burned out. Based on the principle of ultra-fine coal powder reburning low NOx combustion technology and previous research results, the entire furnace combustion zone is divided into the main combustion zone, reburning zone, and burnout zone. The target value of excess air coefficient at the outlet of each region is: the outlet of the main combustion zone α= 0.9-1.0, reburning zone outlet α= 0.8~0.9, outlet of burnout zone α= 1.167。 Both the main and reburning zones of the boiler use actual coal as fuel. The main combustion zone burns 80% to 90% concentrated coal powder, and the reburning zone injects 10% to 20% ultra-fine coal powder as reburning fuel. Denmark DANFOSS oil pump
