Study On Co-pyrolysis Tar Upgrading Of Coal And Waste Catalyst Residue Containing Wax From F-T Synthesis And Its Char Gasification Reaction Characteristics

China's energy structure is dominated by coal,of which low-rank coal accounts for more than half of the proven reserves,but the current utilization method is inefficient.Therefore,a clean and efficient cascade utilization of low-rank coal is proposed.The coal is first pyrolyzed to recover part of the tar and gas,and the semi-char is used for power generation by combustion or converted into syngas by gasification for the preparation of liquid fuels and chemicals.The waxy residue is a waste produced by the indirect coal liquefaction process,which itself contains more wax oil components.Co-pyrolysis of low-rank coal and waxy residue and gasification of co-pyrolysis char can not only improve the yield and quality of tar,but also realize the efficient utilization of waxy residue.In this work,the pyrolysis characteristics of Hailaer coal and Filter residue containing wax from F-T synthesis under different pyrolysis temperatures and different ratios were investigated on-line by using a rapid pyrolysis apparatus,and the yield and distribution of volatile products were analyzed.Then,the effects of ZSM-5 zeolite on the yield and distribution of light aromatics in volatiles of Hailaer coal and waxy filter residue were investigated,and the mechanism of ZSM-5 zeolite catalytic copyrolysis of volatiles was explored under the optimal conditions.The pyrolysis gas and pyrolysis char were produced by using the drop bed reactor,and the yield and composition of the pyrolysis gas were analyzed.The yield of pyrolytic char was calculated,the structure and gasification reaction characteristics of pyrolytic char were characterized and analyzed,and the influence of wax containing filter residue addition on pyrolytic char and its gasification reaction characteristics was explored.The main contents and conclusions are as follows:(1)Hailaer coal and waxy filter residue were fast pyrolysis at 500-800?.Hailar coal produces the most amount light aromatic at 700?,which is because in the early stage of pyrolysis,coal pyrolysis mainly produces a lot of light aromatics,while in the late stage of pyrolysis,condensation reaction begins to take place,and the amount of light aromatics increases slowly.Then,the influence of the addition of waxy residue on co-pyrolysis was investigated.Compared with the experimental and calculated values,it was found that the addition of different proportion of waxy filter residue was beneficial to the formation of light aromatics in the co pyrolysis volatile,indicating that the waxy filter residue played a role of hydrogen supply in the co pyrolysis process.(2)ZSM-5 zeolite(SiO2/Al2O3=40)was used to catalyze the volatiles from the coal and wax containing filter residue pyrolysis,respectively.The addition of ZSM-5 zeolite can greatly improve the yield of light aromatics in the volatile matter of Hailar coal and wax containing filter residue,which is 7.1 times and 26.7 times of that without catalyst,which is because ZSM-5 has catalytic cracking and aromatization.The optimal pyrolysis conditions were as follows:The final pyrolysis temperature is 700?,and the addition amount of ZSM-5 is 0.6 mg.Catalytic conversion of volatiles from co-pyrolysis of Hailaer coal and waxy filter residue showed that the experimental value of light aromatics was higher than the theoretical value,which indicated that ZSM-5 zeolite can decompose the long chain aliphatic hydrocarbons in the wax containing filter residue into small molecule hydrogen rich free radicals,stabilize the aromatic free radicals produced by coal pyrolysis,and promote the formation of light aromatics.(3)Pyrolysis gas and co-pyrolysis char was prepared in a drop bed reactor.Firstly,the yield and composition of pyrolysis gas are analyzed.Compared with raw coal,the gas yield of co-pyrolysis is higher and more hydrogen rich gas is produced.Then,the effect of the addition of waxy filter residue on the gasification reactivity of pyrolytic coke in CO2 atmosphere was investigated by thermogravimetric analyzer at 900?.It was found that the addition of different proportion of waxy filter residue could improve the gasification reactivity of pyrolytic coke,indicating that there was a synergistic effect between the two.When the filler ratio is 3:1,the gasification reactivity of pyrolytic coke is the best,and the K value reaches 0.192.