Experimental Research On Biomass Three Components Pyrolysis And Formation Of Soot

Biomass high temperature pyrolysis can make secondary cracking of tar molecule and increase the conversion rate to pyrolysis gas.However,tar will undergo recombination and polycondensation to form soot under high temperature and anoxic environment,reducing carbon conversion rate and purity of gas.Studying the thermochemical characteristics and soot formation during pyrolysis of three components of biomass can explain the high temperature thermal cracking differences of different types of biomass from the perspective of initial composition of raw materials.In addition,unlike pyrolysis in pure inert atmosphere,adding CO₂ in pure inert atmosphere can increase the conversion rate,and can also recycle CO₂ to reduce greenhouse gas emissions in actual engineering applications.Therefore,the paper compared the pyrolysis of cellulose,xylan and lignin under N₂ and mixed atmosphere?80%N₂/20%CO₂?and used Coats-Redfern method to obtain kinetic parameters firstly,and found the addition of 20%CO₂ catalyzed the pyrolysis of cellulose and xylan,reduced the activation energy of the first weightlessness stage,caused the weightlessness to occur in advance,and reduced some of the pyrolytic carbon in the high temperature region to reduce the solid residue.However,the effect of CO₂ addition on weight loss of lignin was not obvious.The comprehensive evaluation of the order of chemical energy during the pyrolysis of the three components was:cellulose>xylan>lignin.Secondly,the three components were pyrolyzed in mixed atmosphere on fixed-bed,and the soot were collected by filtration,found that the soot yield rose first and then fell with temperature increasing,and lignin pyrolysis would generate more soot because of riching in aromatic rings;The higher the pyrolysis temperature,the smaller,more uniform and more mature the soot;The average particle size of xylan soot was the largest,and the degree of graphitization of lignin and cellulose soot were higher.Increasing the pyrolysis temperature would reduce oxidation activity of soot,The E and A of three components soot were ranked as follows:cellulose>lignin>xylan.Finally,the ultrasonic extraction method was used to obtain the PAHs concentrated solution on the soot,and the qualitative and quantitative analysis of the 16 PAHs preferentially detected by EPA was conducted.The total content decreased,but the average number of rings increased,and the high temperature promoted the growth of PAHs;the content of PAHs on lignin soot was the lowest,but the average number of rings was the highest,and the content of PAHs on xylan soot was the highest,which was also to a certain extent.As a result,its thermal stability was relatively worse.