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Boiler Low Nitrogen Combustion Renovation Plan
In recent years, many large thermal power plants have been built in China. The boiler fuel systems of these power plants usually use some advanced nitrogen combustion technologies to reduce nitrogen oxide emissions. However, these technologies are generally accompanied by the procurement of the main equipment of the boiler, and some equipment also draws on mature foreign technologies.
The technologies developed by these domestic research institutes and power production enterprises have generally achieved very good results in low nitrogen combustion technology, and many domestic boiler production equipment manufacturers are gradually developing towards independent and independent research and development in the field of low nitrogen combustion system design. Currently, in the field of low nitrogen combustion, the main problem in China is the lack of related products in independent intellectual property rights. Therefore, how to improve relevant technologies, form mature technologies, and apply this technology in actual production is a problem that needs to be solved in the future.
The technical principle of staged combustion
The measures that can be taken to suppress the generation of NOx based on the principle of staged combustion 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. decrease excess air coefficient) and block some secondary air ducts.
3. To ensure the output of the boiler, some coal powder and air can be injected 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 to reduce NO to N2 using the hydrocarbon CHi generated during combustion in the main combustion zone and incomplete combustion products such as CO, H2, C, and CnHm.
80% to 85% of the fuel is sent to the main combustion zone, where it burns to generate NOx. 15% to 20% of the fuel is sent to the reburning zone, where the excess air coefficient 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 reignition zone are completely burned. 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, outlet of reburning zone α= 0.8-0.9, outlet of burnout zone α= 1.167.
It has the following characteristics:
1. The low nitrogen burner of the hot air stove is a high-power burner (W=2500KW), using a pilot two-stage ignition method. Full and intense combustion: the flame width can reach 3 meters and the length is 5 meters.
2. The low nitrogen burner of the hot air stove realizes the automatic adjustment function of air distribution: the air volume is fully mixed with the gas, so the combustion is less affected by pressure.
3. The igniter of the low nitrogen burner in the hot air stove adopts an embedded design to ensure the safety and durability of the igniter, effectively extending the service life of the entire system.
4. Strong functionality: integrating ignition, combustion, and furnace temperature detection.