The invention project belongs to the field of advanced energy technology and is a new technology for efficient and clean coal burning. Aiming at the control of NOx emissions from power station boilers, a method of ultra-low NOx emissions has been invented and developed with horizontal lean and lean separation of primary air, reverse blowing of strong primary air, and setting of reducing air as the core, while taking into account the prevention of slagging in the main combustion zone and ensuring high combustion efficiency. The high-efficiency air staged combustion technology with characteristics such as concentrated reverse blowing multiple staged NOx combustion technology and process has been developed. The invention is based on the principle of air staged combustion technology, innovatively changes its principle and technical implementation, and belongs to the category of method and technical process invention.
The key invention point is that for tangentially fired coal-fired boilers, the burners arranged on the corner or wall of the furnace are divided into two groups, upper and lower, along the height direction of the furnace, and an appropriate distance is maintained between the two groups of burners. The lower group of burners is the main (fuel) burner, the primary air is divided into thick and thin phases, and the dense phase uses a large back-blown pulverized coal nozzle; the upper group is an over-fire burner, and reducing air is set in the reduction area in the furnace. This technology effectively achieves multiple staged combustion of pulverized coal in the furnace and achieves ultra-low NOx emissions. Compared with traditional low NOx combustion technology, its unique technical characteristics are as follows: 1. Multiple air classification conditions are formed in the furnace from local outlet of the burner to the entire furnace, and the formation of NOx in the entire process of pulverized coal combustion can be effectively controlled; 2. Dense phase large-reverse flow combustion technology ensures the initial enhanced combustion of pulverized coal, facilitates the initial formation and control of NOx, and guides most pulverized coal, especially the larger the particle size, to be burned in the center of the furnace far away from the water wall, ensuring that there is still a high oxygen concentration atmosphere near the water wall under the deep air classification of the main combustion zone where the primary air is located to avoid wall slagging and high-temperature corrosion problems that are prone to hypoxia in the main combustion zone; 3. For the first time, this technical invention proposes to set reducing air in the NO reduction zone, so that oxygen in the reduction zone can participate in the reduction, strengthen the reduction effect of the coal char on NO, so that the reduction of NO by the coal char and its own burnout can be carried out simultaneously, which is conducive to the later burnout of the coal char. It belongs to a new technology with independent intellectual property rights with efficient ultra-low NOx emission four-corner tangential boiler that adapts to domestic bituminous coal. It is not only suitable for the application requirements of large-capacity supercritical boilers, but also suitable for the application conditions of subcritical boilers with smaller capacity (completely solves problems such as burnout and slagging that may be caused by air classification).
The results of the invention are applied to boilers with a capacity of 300MW and above. The coal is bituminous coal with a received base ash of no more than 10%, and a combustible base volatile content of no less than 30%. Under the conditions of deep air classification, the boiler efficiency can be ensured. A NOx emission control level of 200mg/Nm3 (when the flue gas oxygen concentration is 6%) can be achieved.
It has obtained three national invention patents,"Concentration-Reverse Blow Multiple Staged NOx Combustion Method"(ZL200710042886.6),"Direct Flow Burner Nozzle Structure of Power Station Coal-fired Boiler"(ZL200910312362.3), and "Bottom Air Nozzle Group of Four-corner Tangential Coal-fired Boiler"(ZL200910309786.4); Published 13 papers, including 8 in SCI and 10 in EI. He cited SCI papers 64 times in international journals. So far, this technology has been applied to 2 newly built 300MW boilers and the renovation of low-nitrogen burners of 14 300MW coal-fired boilers. On the newly built boiler, it shows good comprehensive performance under the condition of burning inferior bituminous coal with high ash content. NOx can be greatly reduced, combustion is stable, there is no slagging in the boiler, boiler efficiency reaches the guaranteed value, and superheater output reaches the standard. Good comprehensive performance was also shown in the assessment test of the completed project. These engineering application results show that the technology of the present invention can greatly reduce NOx emissions from coal-fired boilers, and at the same time improve the reliability and safety of boiler operation, as well as the burnout rate of pulverized coal and the stability of combustion; Compared with the tail denitrification technology, the initial investment and operating costs of this technology are significantly reduced, so the 'dense phase large-blow multi-stage high-efficiency low-NOx combustion technology' will gain broad market space in China. With the popularization and application of the technology of the invention in coal-fired power plant boilers, it will make greater contributions to coal-fired NOx emission control, and will inevitably obtain good social benefits.