Exploratory Research On Deashing And Comprehensive Utilization Of Low Quality Bituminous Coal (Coal Gangue)

Low quality coal is mainly burned directly as a kind of fuel for generating electricity, which produce low economic added value, and will pollutes the environment. Coal gangue is a kind of solid waste produced in the process of coal mining, the accumulation quantities is increasing, which is used ineffective, and is also threating the ecological environment and health of people surrounding the mining area constantly. The paper startes with exploratory research on de-ashing and comprehensive utilization of low quality bituminous coal (coal gangue),based on have a thorough understanding on characteristics of the raw material, and conducts a systematic study on de-ashing of bituminous and the separation of metal impurity and silicon of coal gangue, and then explores the feasibility of the synthesis of silicon carbide with low ash coal and low metal content coal gangue. The mainly conclusions obtained are as follow:(1) Deepth de-ashing technology on bituminous coal was studied by acid-base combined method at low temperature. The results show that, under the condition that the alkali-coal ratio is0.35:1, the alkali leaching temperature is180℃,the alkali leaching time is8h,the bituminous coal granularity is-200mesh, as well as acid-coal ratio is1:1,the pickling temperature is55℃,the acid dipping time is lh,the liquid-solid ratio is12:1, ash content of bituminous coal can be reduced from28.37%to0.17%.(2) Synthetic process of SiC powder by carbothermic reduction method with silica sand and bituminous coal after de-ashing was studied. The results show that, under the condition of ball milling time is2h, calcination temperature is1550℃, holding time is4h, which can synthesis ultrafine SiC powder with the purity of89.41%, particle size distributing in5-20microns(average particle size is about9.70microns), average specific surface area is about2969g/cm2,the first synthetic production rate can reach more than90%.(3) Separation technology of Si and impurity metal by the method of acid leaching at low temperature was studied. The results show that, by using ultrafine ball mill coal powder as raw material, under the condition of acid-coal ratio is3:1, acid leaching temperature and time is180℃and4h respectively, metal impurities in coal gangue can be reduced from47.48%to less than0.6%.(4) By using coal gangue which have been removed metal impurities as a silicon source to synthesis SiC powder were studied. The results show that, under the condition of C excessive coefficient of10%, ball milling time is2h, synthetic temperature and holding time is1550℃and4h respectively, the synthesis yield of SiC is78.27%, synthetic purity is77.54%,particle size distribution is between1-15microns, specific surface area is6750g/cm2.