Abstract: As a kind of high alkali metal coal with broad prospect of exploitation and utilization,Zhundong coal in Xinjiang is easy for slagging,which greatly limits its efficient utilization. Much research work has been done on its conventional combustion,but the research on combustion and heat transfer characteristics in O_2/CO_2 atmosphere is still insufficient.In order to study the effect of burning Zhundong coal in O_2/CO_2 atmosphere on alkali metal release and heat transfer performance of heat exchanger,the chemical process analysis software Aspen Plus was used to establish the combustion process flow model of Zhundong coal under the atmosphere of air and O_2/CO_2 for reaction simulation.By controlling the constant O_2/fuel ratio and adjusting the ratio of O_2/CO_2,the adiabatic flame temperature of burning Zhundong coal in O_2/CO_2 is close to that in the air atmosphere.There is a similar temperature distribution in the boiler under these two working conditions.By Gibbs reactor,the product components and state parameters were obtained under the conditions of phase equilibrium and chemical equilibrium,and the occurrence and transformation of Na elements were obtained,which provided a reference for predicting the release form of Na.Due to the high concentration of CO_2 and water vapor content in the oxy-coal combustion flue gas,the heat transfer characteristics of the coal-fired flue gas under the oxy-coal combustion mode will be significantly different.The PR-BM physical property method was used to estimate the physical properties of the flue gas produced by burning Zhundong coal in air and O_2/CO_2 atmosphere,and the density and specific heat capacity of flue gas in different atmosphere were compared and analyzed.The variation of thermal conductivity and viscosity with temperature provides more accurate parameters for analyzing the difference of heat convection characteristics of coal combustion flue gas in air and O_2/CO_2 atmosphere.The heat transfer performance of boiler convection heating surface was analyzed by combining heat transfer theory calculation with CFD analysis.With the decrease of smoke temperature,the existing form of Na gradually changed from Na Cl and Na OH to Na2 SO_4.Oxygen-enriched/flue gas recirculation combustion increases the fouling and slagging of high alkali coal ash.Due to the increase of CO_2 and H_2 O concentration in oxy-coal combustion flue gas,the convection heat transfer performance is enhanced,and the heat transfer coefficients of each convective heating surface increases respectively.The heat transfer coefficient of each convection heating surface is about 1.24-1.27 times of that of conventional working conditions.The convective heat transfer coefficient of the high temperature reheater increases by 24.8 W/( m~2·K) and the steam temperature at the outlet of each pipe nearly increases by 11.32 K under the condition of oxy-coal combustion.