Double Catalytic Effects Of Inorganics On Char-H₂O Gasification Reaction

Minerals are important inorganic components of the coals,which have a significant impact on the char steam gasification process.At present,the study of minerals in char steam gasification focused mainly on gasification reactivity.A few studies focused on the effects of minerals on the generations of main components containing in synthesis gas and their adjusting and modifying actions,and the experimental objects in these researches mainly were bituminous coal Therefore,it has a very important significance in the synthesis utilization of coal gases as feedstocks to study the effects of minerals on char steam gasification reactivity and further conversion in this processIn this study,Ximeng lignite and the demineralized Ximeng lignite were chosen as the experimental objects.The samples were prepared by temperature programmed method with the final pyrolysis temperature of 1000?.The characteristics of the steam gasification of the produced chars are performed by a fixed bed reactor-online gas analyzer.It is found that the minerals in char accelerated the gasification reaction rate,but also converted more CO into CO2,and generated a large amount of H2 during the char-H2O gasification.In order to identify the types of minerals in coal,the inherent minerals in the raw coal were firstly identified by low temperature ashing and XRD.The minerals catalysis can be verified and analyzed with different heat treatment process of coal ash and pure substances in situ action.The mechanism of minerals in situ catalytic gasification reaction was proposed.In addition,to investigate the effect of various biomass ashes on the steam gasification of char,providing a certain basic exploration for char catalytic gasification experiment.The main conclusions are as following(1)The low temperature ash(LTA)sample made by low temperature ashing method,which didn't change the states of inorganic matters,was analyzed by XRD.The result shows that the inherent minerals are composed mainly of quartz,kaolinite,sanidine,calcite,and pyrite(2)Minerals not only have a good catalytic effect on char gasification reaction,especially at a lower temperature of 850-900?,but also promoted the water gas shift reaction,which can prompt more CO to convert into CO2 and generate a large amount of H2.This demonstrates the double catalytic effects of minerals on char-H2O gasification reaction(3)The catalytic role of inherent minerals in char on the water gas shift reaction during char gasification was mainly shown through the great improvement of the quotient of the water gas shift reaction(WGSR),and promotion of its reaction towards chemical equilibrium positive direction.The Ca and Fe-containing compounds in the char can effectively catalyze char steam gasification reaction,which is mainly achieved by WGSR in catalytic gasification process.(4)Using different heat treatment process of coal ash in situ action,it is found that three kinds of ash have a basically consistent catalytic effect on the water gas shift reaction,in which the catalytic effect is closely related to the ash composition By in situ,the anhydrite diffraction peaks of high temperature ash(HTA)sample disappeared,and its catalysis was remarkable and stability as well;the diffraction peaks of calcite,pyrite and hematite in LTA also disappeared,and has the best catalytic effect at 850? during gasification;the gasification ash(GA)sample showed a good thermal stability,and has the best catalytic effect at 1000? during gasification.(5)There is a certain saturation of the char loading catalysis for sawdust ash(SA).When SA content is more than 7%,the gasification reaction was inhibited.The content of potassium and sodium in corncob ash(CCA)is higher,and it shows a good catalytic effect.