Abstract: In the process of coal gasification,a large amount of fine gasification slag( HC-ash) with high carbon content is produced.The ash-waste landfilling occupies a lot of land,causes the pollution of soil and water,and also wastes the energy.How to utilize the coal-gasification ash( HC-ash) is attracting more and more attentions recently.Based on the proximate and ultimate analysis,particle size distribution,ash compositions,and micro-morphologies of HC-ash,the characteristics of HC-ash combustion alone and combustion with raw coal were studied by thermos gravimetric analysis( TGA).The difference of combustion characteristics between HC-ash and typical coal was compared.The influence of mixing ratio on mixture combustion was also considered.The results show that the moisture of HC-ash( as received basis) reaches 69.7%,the ash of dried HC-ash is 54.5%,the carbon content in dried HC-ash is 43.4% with a heating value of 16.14 MJ/kg.The carbon content and calorific value of dried HC-ash are equivalent to that of inferior bituminous coal.The particle size of dried HC-ash is generally smaller than 200 μm,but with a very developed porous structure.The results of SEM show that the microstructure of HC-ash is composed of sphere and porous irregular shapes.HC-ash compared with other types of combustion characteristics show that the ignition temperature and burnout temperature of HC-ash is 601.6 ℃ and 680.8 ℃,respectively,which are slightly worse than those of contrastive coal samples.The TGA results with different mixing ratio of HC-ash and raw coal show that a significant synergistic effect is observed during the co-combustion of HC-ash and raw coal,which can significantly improve the combustion property of HC-ash.When mixing ratio is 25%,the combustion property of HC-ash is significantly improved and the combustion characteristics of mixed coal with HC-ash decreases slightly compared with pure raw coal.This study indicates that the dried HC-ash is of great application value,its co-firing with raw coal has little influence on the combustion characteristics of mixed coal and is able to improve the overall combustion properties.The overall results suggest that combustion of dried HC-ash with raw coal is a feasible technical scheme to utilize the calorific value of HC-ash.