Abstract: The boiler burning with Zhundong coal is prone to deposition and slagging problems on heat-exchanger surfaces,which severely restricts the wide utilization of coal resources in the Zhundong area of Xinjiang province.In this paper,the ash deposition characteristics of Wucaiwan coal were studied on the one-dimensional settling furnace combustion and ash accumulation test system,and the effects of dilution gas type and oxygen concentration of O_2/CO_2 combustion on fly ash deposition were analyzed.The results show that at the concentration of 21% oxygen,compared with N_2,when the diluent gas is CO_2,the adhesion phenomenon of the ash deposition is not obvious,and the tendency of ash accumulation is weak.Under combustion condition of O_2/CO_2,with the rise of oxygen concentration,the ash deposition of Wucaiwan coal tends to increase and the fine ash particles gradually decrease,the proportion of spherical ash particles gradually increases,and the adhesion phenomenon of ash particles gradually increases.The results of SEM-EDS analysis illustrate that with the increase of oxygen concentration in O_2/CO_2 combustion,the surface shrinkage and pits of the ash particles in the deposited ash gradually increase,the white fine floc ash adheres to the surface of the ash particles,and the enrichment of Na and Cl is gradually aggravated,which is an important reason for the intensification of ash deposition on the heating surface in the combustion with high oxygen concentration.In the influence research of dilution gas species on the ash deposition tendency of Wucaiwan coal,the element contents of Na and Cl are obviously higher when the diluent gas is N_2( air combustion) than when the diluent gas is CO_2( O_2/CO_2 combustion).In addition,the enrichment of Ca and S elements also occurs in the deposited ash when the combustion diluent gas is N_2.At high temperature condition,Ca O reacts with the aluminosilicate to form low-temperature eutectics,which is also an important reason why the ash deposition in air combustion is more serious than that in O_2/CO_2 combustion.The results of XRD analysis confirm the conclusion of EDS to some extent.The enrichment of low-melting substances such as CaSO_4 and NaCl in ash leads to the intensification of ash deposition in air combustion conditions and high oxygen concentration O_2/CO_2 combustion conditions.The difference in particle temperature of combustion is the main reason for the difference of ash deposition characteristics between O_2/CO_2 combustion and air combustion,and also is the main reason for the difference of ash deposition characteristics in O_2/CO_2 combustion under different oxygen concentrations.When the combustion temperature of coal particles is higher,the pulverized coal ignition and combustion performance are improved.The higher particle temperature causes more molten ash particles to appear in the flue gas,and the molten phase on the surface of ash particles will increase the viscidity of ash surface and aggravate the phenomenon of ash accumulation.