Abstract: Coal gasification technology is one of the main ways of coal cascade utilization,which develops rapidly and is widely used recently. However,the coal gasification process is not able to convert all the carbon in the coal,and some combustibles remain in the gasification fly ash after coal gasification. The gasification fly ash produced by circulating fluidized bed (CFB) coal gasification usually has high carbon content,and its low calorific value can reach 12-25 MJ/kg. The high-efficient combustion of gasification fly ash powders can improve the coal utilization rate. However,gasification fly ash powder can be hardly burned by the conventional combustion technologies due to its low volatile content. In order to realize efficient combustion of gasification fly ash and control NO_x emission,the technical route of combustion with fuel preheating was put forward and developed. The gasification fly ash powders are first preheated to 850-950 ℃ in a CFB,and then the resulting fuel gas and char particles are burned out in the furnace. In addition,the reaction conditions of high temperature and anoxia are conducive to the removal of fuel nitrogen in the preheated burner,so that the NO_x emission can also be realized with staged air distribution in the furnace. In this study,several commissioning and engineering tests were carried out for a boiler with preheating combustion technology of gasification fly ash. The preheating characteristics of gasification fly ash,combustion characteristics and NO_x emission characteristics of high temperature gas-solid mixture fuel were studied by investigating the temperature distribution and variation in preheating burner and furnace,combustion efficiency and original NO_x emission of gasification fly ash. The results show the gasification fly ash with volatile below 3% could be preheated and burnt out stably. The combustion efficiency can reach 98% and the original NO_x emission can achieve the lowest concentration of 261.94 mg/m~3,and the ultra-low emission can be achieved after denitration treatment.The high efficiency and low nitrogen combustion of gasification fly ash is realized by preheating and burning boiler,and the feasibility and advantage of preheating combustion technology in ultra-low volatile fuel treatment are proved.