Abstract: With the vigorous development of the energy power industry,the situation of air pollution becomes increasingly severe,and the relevant environmental protection standards for NO_x emission control become increasingly strict. Selective non-catalytic reduction technology( SNCR) can effectively reduce NO_x emission,but the production of NO_x needs to be reduced from the source in order to further reduce NO_x emission in circulating fluidized bed.Therefore,the influence law of bed material and fuel particle size on denitration reaction has great research value.The effects of reaction temperature,molar ratio of ammonia to NO_x ,particle size ratio of bed material and average particle size of pulverized coal on NO_x emission were investigated by using the circulating fluidized bed thermal experiment system.The results show that the temperature range of NO_x reduction with ammonia reducing agent is 860-950 ℃ .The denitration efficiency of ammonia increases first and then decreases with the increase of NSR at different reaction temperatures. Increasing the proportion of fine particle bed material can effectively reduce the production of NO_x ,improve the denitration efficiency,and reduce the SNCR active reaction temperature.Among them,the denitrification efficiency of the bed material with the largest proportion of fine particles increases with the increase of NSR.When NSR = 2.0,the denitrification efficiency reaches the highest 42%,and the NO_x emission decreases to 215 mg/m~3.By appropriately reducing the average particle size of pulverized coal,the production of NO_x can be reduced and the SNCR reaction can be carried out at a lower temperature.At each temperature,the NO_x generated by pulverized coal with an average particle size of 330 μm decreases by 10-30 mg/m~3 compared with that of pulverized coal with an average particle size of 425 μm.At high temperature,the denitration efficiency of ammonia reducing agent increases obviously with the increase of fuel particle size.At lower temperature,the denitration efficiency of ammonia may decrease with the increase of fuel particle size.At 910 ℃,the denitration efficiency of pulverized coal with an average particle size of 600 μm is significantly 20%-30% higher than that of pulverized coal with an average particle size of 425 μm under different NSR.At860 ℃,the denitration efficiency of pulverized coal with an average particle size of 425 μm is significantly lower than that of pulverized coal with an average particle size of 330 μm.The main reason for this phenomenon is that the reduction reaction of ammonia is related to the initial concentration of NO_x and the reaction temperature.Ammonia has different reaction selectivity at different initial concentration and temperature.After determining the fuel particle size,the appropriate process operating parameters should be matched to meet the NO_x emission requirements.