Abstract: With the rapid development of China's economy,as an important basic material,the demand for cement products is huge and tends to be stable. The NO_x emission from cement production process and coal-fired power plants and automobile exhaust has become the main source of air pollution,and decomposition furnace is an effective equipment to reduce NO_x emission in cement production process.The air-staging combustion experiments were carried out in a simulated precalciner with high-temperature flue gas,and the effects of air distribution position,air distribution ratio and limestone/coal ratio on combustion and NO_xemission characteristics in cement precalciner were investigated. During the stable test,the coal feeding and air distribution of the high-temperature flue gas generator remain unchanged.At this time,the time-average temperature of the high-temperature flue gas generator is 911 ℃,and the temperature of the high-temperature flue gas produced is stable at approximately 750 ℃ . The NO_x in the high-temperature flue gas mainly exists in the form of NO and N_2O,and the concentration is 261.49×10~(-6) and 12.96×10~(-6),respectively. The high-temperature flue gas will simulate the actual flue gas from the rotary kiln into the decomposition furnace. The temperature in the upper part of the calciner( 0-2 000 mm from the top) is from800 to 1 000 ℃,which is consistent with the actual operation temperature of the calciner. NO_xin the exhaust gas mainly exists in the form of NO and N_2O. As the position of the middle air distribution moves down,the exothermic region of pulverized coal combustion moves down,while the heat absorbed by limestone in the top region changes a little,so the original heat balance is broken and the original heat absorbed is higher than the exothermic quantity,causing the combustion temperature in the top zone to drop. At this time,the reaction time of coal combustion and limestone decomposition becomes longer in reducing atmosphere,which leads to more sufficient reduction of NO_x.However,calcium oxide( Ca O) produced by limestone decomposition,as an intermediate product,can promote the formation of NO,and its reaction time also promotes the formation of NO. On the other hand,limestone is used as a catalyst in the reduction of NO by char and volatiles,the reduction of NO is weakened due to the decrease in temperature in the top zone of the decomposition furnace. To sum up,the final emission concentration of NO is the combined result of the above reactions. As the position of air distribution moves down,the effect of those changes on NO production becomes more obvious,so the concentration of NO emission increases gradually. When the ratio of the first air flow rate to the second air flow rate is reduced,the coal combustion rate and limestone decomposition rate in the upper part of the calciner decrease,and the proportion of pulverized coal combustion and the proportion of undecomposed limestone in the lower part of the calciner increases,but the heat absorption increase of limestone is higher than the heat release of combustion increase,so the whole temperature of calciner decreases. The concentration of NO in the calciner is determined by the oxidation and reduction processes catalyzed by limestone. The concentration of CO in the tail increases and the concentration of NO in the flue gas decreases with the decrease of the first stage air flow rate. When the ratio of limestone to coal increases,the temperature in the calciner decreases gradually. With the increase of the amount of limestone powder,the CaO concentration produced by thermal decomposition of limestone in the calciner increases,and the NO reduction reaction is more intense,and the NO concentration decreases gradually. The increase of limestone powder and the decrease of calciner temperature lead to the increase of CO concentration in the tail.