Characteristics And Kinetics Of Tar Catalytic Reforming By Char In Micro Reactor

Gasification is regarded as a promising method for the conversion of coal and carbonaceous materials into syngas and fuel gas.However,despite the production of useful products,some undesirable contaminants such as tar,are inevitably produced as by-products which brings problems to the whole gasification process such as blocking and corroding of pipes and equipment,poisoning of catalyst,and the production of phenolic wastewater and irritating gases that contributes to severe environmental problems.In recent years,tar removal by char catalytic reforming has been widely considered as a feasible catalyst with a good technical and economical property.Being an intermediate product in the gasifier,char owns obvious advantages,such as cheapness,abundance,good reactivity,strong resistance in sulfur and chlorine to avoid poisoning,and no consideration of catalyst regeneration after deactivation.All of these characteristics make char a good catalyst for tar removal in a commercial gasifier.However,the existing reports mainly focus on the feasibility research on tar removal by char and the improvement of tar removal efficiency.Researches about the mechanism of tar catalytic removal and the reaction kinetics are very few,strongly inhibiting the rapid development of this novel tar removal technology.To reveal the reaction characteristics of tar catalytic reforming by char,a TGA and newly developed micro fluidized bed reaction analyzer(MFBRA)were adopted in this study.The non-isothermal and isothermal reaction behavior were analyzed and compared.Moreover,to verify the advantages of char catalytic reforming by char,the thermal cracking of tar was also examined.This thesis primarily investigates the characteristics,role of metal oxides and kinetics of tar catalytic reforming by char in a newly developed micro fluidized reaction analyzer(MFRBA)with the aim to expand the understanding of tar catalytic reforming and to propose kinetic models for fuel gas production.The non-isothermal cracking behavior of tar by char was firstly investigated and compared with results realized by non-isothermal cracking behavior in TGA.Under the experimental conditions,the temperature and char property were considered the key factors that efficiently promote the tar cracking reaction.While,the activation energies for thermal cracking and catalytic reforming by char were 27.38 and 18.47 kJ/mol respectively.The isothermal reforming behavior of tar by char was examined in a micro fluidized bed reaction analyzer.To investigate the effect of metal oxide in char on tar catalytic reforming,the char-supported metal oxide catalyst has been prepared by the impregnation method.The catalytic activity followed the order of CaO-char>K2O-char>Fe2O3-char>Na2O-char>MgO-char.Hence,this study will deepen the understanding of tar catalytic reforming by char,and also promote the development of gasification process for the production of coal-basis industrial fuel gas.