The effect of air distribution on the characteristics of waste combustion and NO generation in a grate incinerator

The combustion process optimization and nitrogen oxide emissions reduction of waste incineration power generation is a key challenge. In order to reveal the influence of air distribution on the combustion process and NO emission in a grate-type waste incinerator, the combustion process and NOx generation in a waste incinerator were studied, and the influence of different ratios of primary air in the grate chamber, different ratios of primary air and secondary air, and different speeds and angles of secondary air on the combustion and NOx emission characteristics were explored. The results show that the moisture evaporation and mass loss rates of combusted MSW (municipal solid waste) increase accordingly as the air ratios of the primary air in the zone1 increases. As the ratio of air flow in the combustion section (zone 2) in the grate chamber increases, the high temperature area and oxygen concentration above the grate will increase, and the NO formation will be promoted accordingly. The NO concentration at the furnace outlet is reduced from 259.34 mg/Nm³ to 201.34 mg/Nm³, as the air flow ratio of the grate chamber in the combustion section (zone 2) is reduced from 0.50 to 0.34. With the increase of secondary airflow ratio, the high temperature zone in the furnace increases, and more NO is generated above the grate, however, the NO concentration at the furnace outlet decreased, the probable reason is the combined result of temperature and turbulent kinetic energy. The secondary air speed has a great influence on NO generation. With the increase of secondary air speed of SA3 and SA4, the concentration of NO at the furnace outlet decreases. The secondary air angle has little effect on NO generation, but has great effect on temperature distribution uniformity.