Experimental Study On The Pyrolysis Of Three Main Components In Biomass

Biomass as a renewable energy source has significant potential to transform into biochar, bio-oil and gas by the pyrolysis process, its pyrolysis behavior can be presented by three main components in biomass(lignin, cellulose, hemicellulose), therefore, the study on pyrolysis characteristics of three main components in biomass can provide theoretical basis for improving the quality of pyrolysis products in terms of mechanism. This study presented the pyrolysis characterization of three main components in biomass to provide comprehensive information for distributions and properties of pyrolysis products(char, bio-oil and gas) gained at different pyrolysis temperatures by a lab-scale tube furnace pyrolysis reactor. The detailed work was so follows:Three main components in biomass samples were investigated on basal analysis, the pyrolysis tests on three main components were conducted at different pyrolysis temperatures.The influence of pyrolysis temperature on yields and properties of char producted from three main components in biomass was investigated, the results were as follows: as the pyrolysis temperature increased, the yields of char producted from lignin, cellulose and hemicellulose continued to decrease from 72.94%, 69.09% and 58.26% to 39.79%, 12.27% and 21.34%, respectively; volatile content of the char rapidly decreased, fixed carbon content to increase, combustion reactivity of char samples obtained at 500 ℃ was the best; the char obtained from lignin pyrolysis at 600 ℃ had the most developed pore structures, and the specific surface area and iodine adsorption value of which reached the largest value, while the char obtained from cellulose or hemicellulose pyrolysis at 500 ℃ had the most developed pore structures, and the specific surface area and iodine adsorption value of which reached the maximum value.The influence of pyrolysis temperature on yields and compositions of bio-oil producted from three main components in biomass was investigated, the results were as follows: as the pyrolysis temperature increased, the yields of bio-oil producted from lignin, cellulose, hemicellulose pyrolysis at 600 ℃, 500 ℃ and 450 ℃ increased to the largest value, respectively; the main ingredients in bio-oil got from lignin were phenols, relative content of which increased with an increase of pyrolysis temperature, and the highest bio-oil yield obtained the most types of phenols; the main ingredients in bio-oil got from cellulose were saccharides, furans, ketones, with pyrolysis temperature increasing, relative content of saccharides reduced continuously, relative content of ketones rose significantly, while relative content of furans showed unobvious change; the main ingredients in bio-oil got from hemicellulose were acids and ketones, with pyrolysis temperature increasing, relative content of acids first decreased, then remained stable state, relative content of ketones increased significantly.The influence of pyrolysis temperature on yields and compositions of pyrolytic gas producted from three main components in biomass was investigated, the results were as follows: the yields of pyrolytic gas producted from lignin, cellulose and hemicellulose continued to increase from 8.93%, 5.37% and 13.12% to 28.09%, 39.96% and 46.04%; the main composition of non-condensable gas obtained from lignin was CO2, CO and CH4, as the pyrolysis temperature increased, the volume content of CO2 in gas products rapidly decreased, the volume content of CO first decreased, then gradually increased, while the volume content of CH4 showed a noticeable increasing trend, resulting in being the dominant composition in gas products above 450 ℃; the main composition of non-condensable gas obtained from cellulose was CO2 and CO, as the pyrolysis temperature increased, the volume content of CO2 in gas products rapidly decreased, volume content of CO first increased, then decreased, resulting in the dominant position of CO in gas products above 450 ℃; the main composition of non-condensable gas obtained from hemicellulose was CO2 and CO, as the pyrolysis temperature increased, the volume content of CO2 in gas products rapidly decreased, the volume content of CO increased followed by a decrease.The comparative analysis on yields and properties of three main components in biomass was conducted, the results were as follows: lignin was the main responsible of biomass char yield, cellulose was the main responsible of biomass bio-oil yield, hemicellulose was the main responsible of biomass pyrolytic gas yield; the char received from lignin was suitable as low ash carbon fuel, the char received from cellulose was suitable as ignition carbon fuel, and cellulose was the main responsible of biomass char adsorption; hemicellulose was the main responsible of CO2 yield, lignin was the main responsible of CH4 yield, while minor responsible of CO yield.