Study On The Gasification Of Coal Char With H₂O/CO₂ Catalyzed By Binary Composite Metal Salts

In this paper,the typical alkali metal,alkaline earth metal and transition metal salt(K,Fe,Ca)are taken as the research object to investigate the influence of composite catalyst on the gasification of coal char with H2O and CO2.The main contents of this paper are:the reaction characteristics of coal char with typical single or binary composite metal compound catalyst in the process of H2O/CO2 gasification,the change process of catalyst and the catalytic mechanism.The effect of single catalyst on the product selectivity and gasification activity of ash free Shenfu bituminous coal char was investigated in a fixed bed reactor.It was found that Fe2(SO4)3 is more favorable to the formation of H2 and CO than K2SO4,but the coal char containing K2SO4 has a higher carbon conversion rate in the gasification reaction.Under the experimental conditions,the best addition amount of Fe2(SO4)3 and K2SO4 are 5wt%and 10wt%,respectively.In the process of gasification,Fe2(SO4)3 forms redox cycle,while K2SO4 has a low melting point and maintains a good flow state at a lower gasification reaction temperature.In the process of gasification,CaSO4 forms a relatively stable CaO,reducing the gasification reaction activity.Fe2(SO4)3,K2SO4,CaSO4 were compounded in two ways.The experiment of H2O gasification was carried out on the fixed bed reactor of vertical tube furnace,which was convenient for the analysis of its products.The experiment found that the K had better catalytic effect,in which the K-Ca composite catalyst was more favorable for the formation of CO,and the Fe-K composite catalyst for H2,CO,CH4 and CO2 It can promote the formation.Only Fe2(SO4)3-K2SO4 composite catalyst can improve the carbon conversion rate(synergistic effect),the presence of K salt in the gasification process reduces the melting point of Fe salt,and produces a-Fe in the gasification stage,so the catalytic activity is enhanced.By means of thermogravimetry,the CO2 gasification of coal char with different kinds of coal ash removal catalysts containing different anionic and cationic binary composite metal compounds was investigated.It was found that K-Fe and K-Ca have synergistic effect.When the ratio of catalyst is K:CaO4:1 and K:Fe=4:1,it has the best catalytic effect.The higher the coal rank,the better the catalytic effect.Potassium catalyst can reduce the melting point of calcium catalyst and iron catalyst,and ?-Fe and other amorphous forms of Fe-K composite appear in the heating stage,which can promote the gasification of CO2.