Experimental Study And Numerical Simulation Of Oil Production By Microwave-heated Catalytic Pyrolysis Of Biomass

Biomass energy as the only renewable carbon source has been widely concerned,Oil production from biomass pyrolysis is a research hotspot in the field of biomass utilization.However,the non-catalytic pyrolysis of biomass to produce bio-oil generally has high oxygen content,strong corrosion and poor stability,which limits the application of bio-oil.In this paper,a series of basic research work was carried out from the aspects of catalyst and pyrolysis reactor.With bamboo sawdust as raw material,the catalytic pyrolysis characteristics of metal simple substance and low-valence metal oxide were investigated on Py-GC/MS,and the high efficient chemical chain deoxidation catalyst system was explored,composite Metal catalysts were prepared by means of modification.In addition,in order to obtain high quality bio-oil,a series of pyrolysis experiments were carried out on a fixed bed heated by microwave and a fluidized bed heated by microwave,it provides theoretical guidance for the optimization design of microwave pyrolysis process and test-bed.In terms of Py-GC/MS experiment,the optimum reaction temperature was 600 °C,and an efficient chemical chain deoxygenation catalyst system was explored.The experimental results show that the use of metal catalysts in single-stage catalytic mode is beneficial to reduce the oxygen content of bio-oil.In the two-stage catalytic mode,the introduction of HM further reduced the unfavorable components such as acids,aldehydes and macromolecular compounds,and significantly improved the hydrocarbon yield and the selectivity of monocyclic aromatic hydrocarbons.Among them,Zn/HM has the most significant effect,with a hydrocarbon yield of 79.14%,and Fe/HM has the highest monocyclic aromatic hydrocarbon selectivity,reaching 73.31%.In addition,the influence of Fe/Ce composite catalyst on the catalytic pyrolysis performance of biomass was explored.The best catalytic performance was obtained when the molar ratio of fe/Ce was 8:2 with a maximum hydrocarbon content of 33.46% and a single ring of 52% Aromatic selectivity.The scale-up experiment was carried out on a fixed bed heated by microwave.Firstly,the effects of metal catalysts and composite molecular sieves on the deoxidation and upgrading of bio-oil were investigated under different catalytic modes.Secondly,the experiments of catalyst regeneration were carried out,and the weight-loss characteristics of catalysts obtained in different catalytic modes were analyzed.The results showed that the use of metal catalysts reduced the yield of bio-oil,and the highest hydrocarbon yield,6.23%,was obtained by Ni addition.The introduction of HM greatly simplifies the distribution of pyrolysis products.The combination of FE,Ni,Zn and HM was beneficial to the increase of hydrocarbon yield.The highest hydrocarbon yield was obtained under Zn/HM condition,reaching 31.10%,and the highest phenol yield was obtained under Fe/Hm catalysis mode,63.05%.In addition,the introduction of Fe improved the carbon deposition of HM by only 1.96%.The catalyst regeneration test showed that the maximum yield of hydrocarbon was 32.96% after two regenerations,and the yield of hydrocarbon and the activity of catalyst decreased obviously after more than three regenerations.The catalyst with carbon deposition has two typical weight loss stages,which correspond to the weight loss of water and carbon deposition respectively.High temperature roasting can effectively remove carbon deposition on the catalyst surface,at the same time,it proves that the two-stage catalytic mode is more conducive to improving the carbon deposition of HM.A series of experimental studies were carried out on a self-designed and built fluidized bed tandem reforming furnace test bench.The results show that in the HM single-stage catalytic mode,28.56% hydrocarbon yield and 40.28% relative content of phenolic products were obtained from pyrolysis of bamboo sawdust.The distribution of pyrolytic products was changed with the introduction of metal catalysts,in which the highest hydrocarbon yield was obtained in Zn/HM condition,reached 38.16%,and the highest phenol yield was obtained in Fe condition(48.49%).In addition,the addition of metal catalysts promoted the conversion of heavy phenols and improved the hydrocarbon components.The performance of Fe /HM was the most prominent.The Ni/HM combination achieved the highest selectivity of monocyclic aromatic hydrocarbons(44.68%).Based on experimental research,the two-euler fluid model and multi-component,multi-step reaction model were used to simulate the biomass pyrolysis process in a fluidized bed reactor,The results show that the temperature field in the bed is stable when the simulation time is longer than 12 s,and the concentration field fluctuates steadily when the simulation time is longer than 60 s,and the deviation is less than 5%.Among the reaction temperature,carrier gas flow rate and initial bed height,the temperature has the most obvious influence.The pyrolysis oil yield increases first and then decreases with the increase of temperature,and reaches the maximum value at 550℃.The deviation between simulation and experiment is within a reasonable range,and the law of variation is basically consistent.