Combustion and NOx Emission Characteristics of Coal Slime Solid Waste at Different Feeding Positions

The NOx emission of coal slime burned in circulating fluidized bed (CFB) boilers could hardly meet the increasingly strict standards in China. Feeding coal slime from the top of furnace led to uneven combustion in furnace and cyclones, short residence time and overheated tail heating surface. The effects of feeding positions on the combustion uniformity and pollutant emission characteristics of coal slime were studied. The experimental results showed that the coal slime combustion was more uniform when feeding from the front wall and longer residence time was conducive to the control of NOx emission. When the boiler temperature and excess air ratio were almost identical, the initial NOx emissions were 45.0 mg·m−3 and 70.7 mg·m−3 when feeding from the front wall and the top of furnace, respectively; the NOx emission was cut down 36.35% when feeding from the front wall, successfully meeting the ultra-low NOx emission standard of China. The adoption of feeding from the front wall greatly reduced the original emission of NOx; the operation costs in the practical applications were saved to a large extent.