Pyrolysis Characteristics And Kinetics Of Agricultural And Forestry Wastes

At present,all countries in the world are facing the pressure of energy shortage and environmental pollution.During the combustion of fossil fuels,pollutants such as SO2,CO2 and nitrogen oxides will be produced,which seriously affects the atmospheric environment.The total amount of agricultural and forestry waste in China is rich.If it can be used efficiently,it can not only alleviate the current energy crisis,but also avoid polluting the environment and occupying land.Biomass pyrolysis technology can directly convert agricultural and forestry wastes and other biomass resources into pyrolytic gas,pyrolysis tar and biochar,which can achieve energy recovery and avoid environmental impact.In this paper,typical agricultural waste corn stalk and typical forestry waste peach wood were selected as the research objects,and three states of gas,liquid and solid were collected through tubular furnace pyrolysis experiment.The final pyrolysis temperature(350℃,400℃,450℃,500℃,600℃,700℃),the heating rate(5℃/min,10℃/min,20℃/min,30℃/min)and the carbonization time(10min,15 min,20min,30 min,60min)on the properties of pyrolysis products.The results show that temperature,heating rate and residence time have great influence on the distribution of biomass pyrolysis products.(1)With the rise of temperature,the yield of carbon and tar decreased,the yield of gas increased,the content of ash and fixed carbon of biochar increased,the volatiles showed a decreasing trend,and the H/C ratio and O/C ratio of the prepared carbon gradually decreased,indicating that the degree of carbonization of biochar increased and the aromaticity increased.(2)With the increase of heating rate,the yields of tar and pyrolysis gas increased significantly,while the yields of biochar decreased,and the ash and volatile contents of the prepared biochar increased.(3)With the extension of biomass residence time,the yield of pyrolytic carbon and tar decreased,while the gas yield increased.The ash content of the prepared biochar increased,while the volatiles showed a downward trend.The pyrolysis process of biomass feedstock was studied by thermogravimetric analyzer.The optimal kinetic model suitable for the pyrolysis of agricultural and forestry wastes was found,so as to further understand the pyrolysis characteristics of biomass.The results show that with the increase of heating rate,the temperature corresponding to the maximum pyrolysis rate increases,and there is an obvious thermal hysteresis effect.Pyrolysis kinetics analysis showed that the peach branch’s pyrolysis process was in line with the first-order pyrolysis reaction kinetics model,and the activation energy of dried peach branch was low,indicating that peach branch was easy to undergo pyrolysis reaction.