Abstract: Coal gas produced from coal gasification,is frequently used as a fuel in the aluminium hydroxide calcination process.Normally,coal gas generally contains a certain amount of ammonia,resulting in a high amount of nitrogen oxides in the roasting process.In this paper,the low-nitrogen combustion process of gas was studied by air classification method in a gas-fired aluminum hydroxide suspended calciner,and the influence of air classification technology on the formation of nitrogen oxides in gas combustion in the calciner was investigated,so as to guide the actual combustion structure design and optimization in the calciner.Barracuda~(TM)software was utilized to simulate the gas-solid two-phase flow and the combustion process in a 3 000 t/h Al_2O_3calciner.The results show that there is an obvious high temperature zone at the bottom of the suspension calciner.The local high temperature load point is concentrated,and the maximum temperature is up to1 700 K.With the increase of furnace height,the mean temperature decreases gradually.Additionally,due to the effect of airflow reflux,there is a high concentration area of particles in the bottom of the furnace and the upper airflow diversion.Based on the temperature field in the furnace calculated by gas-solid flow,and the detail chemical reaction process was considered by coupling the detailed chemical reaction mechanism.The reactor network was established by using Chemkin Pro software,and the influence of air classification technology on the formation of NO_xin the combustion process of ammonia-containing gas in the calciner was investigated by numerical calculation.The results show that the main nitrogen oxides produced in the calciner burning gas are fuel nitrogen oxides.In addition,the inhibition effect of air classification on the formation of NO_xin gas combustion is limited when the staged-air ratio is 20%.However,the NO_xemission generated by gas combustion in calciner reduced up to 70.3%when the staged-air ratio is 40%,and the reducing atmosphere appears in the main combustion area.