Product Distribution And Experimental Study Of Lignocellulosic Biomass Directional Pyrolysis

Lignocellulosic biomass is an ideal raw material for pyrolysis process,how to effectively increase the yield of target products and inhibit the formation of non-target products in the process of pyrolysis is the focus of current study.In this paper,the basic parameters of pyrolysis process and catalytic pyrolysis of biomass and its components were firstly studied.Then,the effects of cross coupling pyrolysis of biomass components and catalytic co-pyrolysis of hydrogen rich materials and oxygen rich biomass on the distribution of liquid products were combined to systematically study the product distribution of biomass directional pyrolysis.Finally,based on the characteristics of pyrolysis products and energy yield,the pyrolysis of biomass in a rotating bed was studied.(1)The differences in the composition and structure of cellulose,hemicellulose,and lignin make the three components show different product formation characteristics in the pyrolysis process.Pyrolysis temperature and time can significantly affect the types and yields of compounds in pyrolytic bio-oil of the three components,and reaction time has less effect on the product distribution than temperature.Different doses of K2SO4,ZnCl2,HZSM-5,MCM-41,and ZrO2 can obviously change the distribution of pyrolysis products of the three components,which mainly manifested as that a single component with different kinds of catalysts and a single catalyst with different components all show different characteristics of pyrolysis products.Moreover.cellulose,hemicellulose,and lignin interact with each other in the experiment of cross ratio of components.The product distributions of mixed components can not be replaced by the simple superposition of pyrolysis product distribution of each component.(2)Due to the difference of lignocellulosic biomass composition and structure,the distributions of pyrolysis products of different biomass materials are vary greatly.Pyrolysis temperature and time can obviously affect the types and yields of compounds in pyrolytic bio-oil of aspen wood,rice husk,and corn stalk,and reaction time has less effect on the product distribution than temperature.Different doses of K2SO4,ZnCl2,HZSM-5,MCM-41,and ZrO2 can obviously affect the distribution of pyrolysis products of the three biomass.Moreover,from the component coupling pyrolysis experiments of cellulose,hemicellulose,and lignin,it is concluded that the three components interact during pyrolysis and the interaction of pyrolysis of mixed components is less than that of biomass components.(3)The co-pyrolysis of corn stalk(CS)and polypropylene(PP)can obviously change the distribution of compounds in bio-oil,and the metal loading and loading ratio of molecular sieve catalyst have a significant effect on the formation characteristics of pyrolysis products.Zn and Al showed a certain synergistic effect,under catalysis with 1 wt%Zn-3 wt%Al/MCM-41,and the maximum proportions of aromatics(24.31%)and the minimum production of oxygenated compounds(12.37%)were obtained.With Zn-Al co-modified MCM-41,the highest contents of benzene,toluene,xylene,trimethylbenzene,naphthalene,and indene were 1.33,1.84,2.31,1.15,1.20,and 1.08 times the output of MCM-41,respectively.The catalytic co-pyrolysis of CS and PP also showed a synergistic effect on the production of aromatic hydrocarbons compared with their individual catalytic pyrolysis and the chemical mechanism of that synergy was revealed according to the acidic center of zeolite,hydrocarbon pool mechanism,and Diels-Alder reaction.Additionally,this synergy ability was further confirmed by thermogravimetric(TG)analysis and pyrolysis kinetic analysis.(4)In the experiment of catalytic co-pyrolysis of corn stalk(CS)and polypropylene(PP)in rotating bed,with the increase of pyrolysis temperature(500?800?),the yield of bio-oil decreased gradually.The decrease of olefin and oxygenate content in bio-oil makes aromatic hydrocarbon content increase significantly.With the increase of catalyst dose(1:0?1:10),the yield of bio-oil reduced gradually.The contents of aromatic hydrocarbons in bio-oil increased obviously,while the contents of olefins and oxygenates decreased.With the increase of rotating speed(0?20r/min),the yield of bio-oil first decreased and then increased.The highest contents of aromatics,olefins,and oxygenates in bio-oil were all obtained at 15r/min.The sensitivity of different parts(cob,leaf,stem,and root)of CS to pyrolysis temperature is different,based on Plackett-Burman(PB)experimental design and response surface Central Composite Design(CCD)model,the optimal pyrolysis and carbonization conditions are as follows:a heating rate of 5.96?/min,holding time of 1.54 h,pyrolysis temperature of 424.87?,and rotation speed of 11.05 r/min.The predicted maximum energy yield was 76.66%.During the operation of biomass rotary pyrolysis pilot plant,the change trend of biochar yield and calorific value is noticeably negatively correlated.With the increase of temperature,the yield of biochar decreased significantly while the calorific value increased remarkably,and the energy yield decreased gradually.With the increase of rotating speed,the yield of biochar increased while the calorific value decreased,and the energy yield increased.