Study On Pyrolysis Characteristics And Kinetics Of Three Components Of Biomass

Biomass pyrolysis is the key technology to convert the biomass energyinto high grade energy and chemical products. Because of the obviouscomponent and structural differences, the heat pyrolysis of three maincomponents of biomass, cellulose, hemicellulose and lignin is a quite complexphysicochemical process. The pyrolysis characteristics and kinetics of threebiomasses were investigated in this paper. Then, the pyrolysis characteristicsand interactions for three main components of biomass were studied.Firstly, the pyrolysis characteristics of three biomasses (methyl cellulose,bagasse and peanut shell) were studied by means of thermogravimetricanalysis method. The results indicate that the pyrolysis of peanut shell coversthe widest pyrolysis temperature range from 230℃to 580℃. The pyrolysis ofmethyl cellulose and bagasse are mainly in the range of 300℃and 400℃.Thepyrolysis kinetic models of theirs were developed with Coats-Redfern integralmethod. The results show that the pyrolysis reaction of theirs can be describedwith the first-order kinetics in their main reaction temperatures. Active energyof methyl cellulose among three biomasses is highest.The research on the pyrolysis characteristics and kinetics of three maincomponents of biomass, cellulose, xylan (which is the modeling material of hemicellulose) and lignin show that differences among the pyrolysises of thethree components depend upon differences of their molecular structures. Themass lose of the cellulose, xylan and ligin are about 86%, 69% and 51%respectively in the experimental temperature range. The reaction depth of thethree components of biomass reduces from cellulose, xylan to lignin orderly.The pyrolysis reaction of lignin as well as xylan can be described with twosecond-order kinetics in its two different temperature regions. However, afirst-order reaction in the low temperature region and a second-order reactionin the high temperature region are best suitable to describe the pyrolysis ofcellulose.There is a unilateral effect between pyrolysis of xylan and that ofcellulose. The cellulose has little contribution to the pyrolysis of xylan, butxylan produces significant inhibiting effect to pyrolysis of cellulose. There is asimilar conclusion between pyrolysis of lignin and that of cellulose: celluloseproduces have unilateral inhibiting effect to pyrolysis of lignin.The pyrolysis and catalytic pyrolysis of cellulose and lignin were carriedout in a fixed bed reactor. The results indicate that the calcined dolomiteshows the favorable catalytic performance to the pyrolysis reaction ofcellulose, but it does not show remarkable effect on the pyrolysis reaction oflignin in comparison with that of cellulose.