Study On The Key Apparatus Development And Characterizations Of Mobile Combined Heat Transfer Fluidized Bed For Biomass Fast Pyrolysis

Mobile fast pyrolysis equipment can be easily transported to forest farms,farms,villages and other areas with rich biomass resources.On the spot,the biomass with low energy density can be converted into high-quality pyrolysis products,which can effectively solve the problem of biomass raw material collection,storage and transportation.However,there are few researches on the mobile pyrolysis equipment at home and abroad,which is still in the initial stage of development.There are many problems that need to be studied deeply and systematically.In this paper,the optimal design and experimental research on the key apparatus such as feeder,reactor and condenser of the mobile biomass rapid pyrolysis equipment are carried out,and the mathematical model of feeding rate and the heat transfer model of the combined heat transfer fluidized bed reactor are established,a set of mobile combined heat transfer fluidized bed for biomass fast pyrolysis with a capacity of 35?50 kg/h is developed,and the fast pyrolysis experiment of larch sawdust is carried out,the characteristics of the equipment and the physicochemical properties of pyrolysis products are analyzed.The main conclusions of this paper are as follows:(1)The study on the characteristics of biomass fast pyrolysis double bin pneumatic conveying feeder is carried out.The results show that the feeding rate is mainly affected by spouting gas velocity,fluidizing gas velocity,inner diameter of conveying pipe,effective spraying distance and biomass particle size.A multiple linear regression model between the feeding rate and each factor is established,the error is within ± 10.2%,which can be used to predict the feeding rate of double bins pneumatic conveying.(2)The experimental study and numerical simulation of heat transfer are carried out in reaction zone and annular zone of combined heat transfer fluidized bed reactor.The results show that the comprehensive heat transfer coefficient is affected by the inlet gas velocity of high temperature flue gas,the type and height of packing.The comprehensive heat transfer coefficient is directly proportional to the inlet gas velocity of high temperature flue gas and packing height.(3)At room and high temperature,the experimental study on the change of critical bed porosity and critical fluidization velocity with temperature is carried out with quartz sand and dolomite used as bed materials in reaction zone of combined heat transfer fluidized bed reactor.The results show that the critical bed porosity increases linearly with the increasing of temperature,increases with the increasing of bed particle size,and the critical fluidization velocity decreases with the increasing of temperature,and increases with the increasing of bed particle size.The method of calculating critical fluidization velocity at high temperature is put forward by integrating the factors of critical bed porosity,simulated non condensable gas density and viscosity changing with temperature into the classical Ergun equation.(4)The design of the combined heat transfer fluidized bed reactor with the inner tube as the fluidized bed reactor and the annular area between the inner tube and the outer tube as the heating area is optimized.The design of the double bins pneumatic conveying feeder including the feed bin and the transition bin is completed.The combined condenser with the multi-functions of spray and jet condensation and heat exchange is optimized.The design of other parts are also completed.A mobile biomass combined heat transfer fluidized bed equipment with a capacity of 35 ? 50 kg/h has been completed.(5)The operation characteristics of the mobile combined heat transfer fluidized bed for biomass fast pyrolysis are carried out.The effects of reaction temperature on the yield,components,physical and chemical properties of pyrolysis products are studied with larch sawdust as raw material.The condenser performance,LPG substitution rate,the fluidization carrier gas consumption and energy balance analysis are carried out.The results show that the highest yield of bio-oil is 68.62 wt% at 500 ?,and the yields of pyrolysis carbon and non condensable gas are 12.13 wt% and 19.25%,respectively.The replacement rate of LPG is 76.42%,the energy efficiency of bio-oil is 66.96%,and the total energy efficiency(bio-oil,pyrolysis carbon)is 82.19%.