Effects Of Homologous And Non-homologous Charcoal On Pyrolysis Of Corn Stalk

With the increasing exhaustion of fossil resources and the intensification of environmental pollution problems,renewable energy sources such as straw has received great attention.Pyrolysis technology can convert biomass into products such as biogas,bio-oil,and bio-char.It is one of the main technologies for high-value utilization of biomass.Co-pyrolysis of biomass and other substances can change its pyrolysis behavior,improve the selectivity of pyrolysis,and promote the production of target products.Studies have shown that co-pyrolysis of biochar or coal and biomass can change its pyrolysis characteristics.The composition,physical and chemical properties of biochar and coal are similar,with high C content,rich pore structure,better thermal stability and adsorption;both are carbonaceous solid fuels with highly complex chemical structures,with similar fuel ratios.However,(1)H/C,O/C,volatiles,and calorific values of biochar and coal are different,which may affect the generation of oxygenates and small molecule volatiles in the products of co-pyrolysis;(2)The specific surface area of biochar is larger than coal,which may be more conducive to contact between char and biomass,and promote co-pyrolysis reaction;(3)Biochar has a stable aliphatic chain structure and highly aromatic structure.The co-pyrolysis reaction will promote more functional group changes and generate more potential chemical reactions.In order to compare the effects of homologous charcoal and non-homogeneous charcoal on biomass pyrolysis characteristics,this paper used corn stalk to co-pyrolyze with straw carbon or anthracite,respectively,analyzed its pyrolysis characteristics and product distribution,and proved the influence of straw charcoal and anthracite on the pyrolysis of corn stalks,provided data support for biomass co-pyrolysis and a theoretical basis for promoting the high-value utilization of biomass.Firstly,Through TG-FTIR and fixed bed pyrolysis experiments,to study the effect of straw charcoal on the pyrolysis characteristics of corn stalk.The effects of blending ratio and pyrolysis temperature on the distribution of co-pyrolysis products and pyrolysis kinetic parameters were investigated.The results showed that the addition of straw charcoal significantly affected the pyrolysis characteristics and product distribution.(1)With the blending ratio of straw charcoal increased,the residue rate at 900℃ gradually increased.The co-pyrolysis reaction shifted to the high temperature,corn stover and straw charcoal had obvious synergy in the co-pyrolysis process.With increasing of straw carbon blending ratio,the activation energy of the reaction increased from 84.75 kJ/mol to 96.28 kJ/mol,and then gradually decreased to 65.92 kJ/mol.(2)The blending ratio and temperature were important for co-pyrolysis characteristics of corn stalk and straw charcoal.With the straw charcoal blending ratio increased from 0 to 100%,the volume fractions of H2 and CO increased from 2.89%and 9.03%to 6.23%and 10.78%,respectively,and the gas production increased from 0.19L/g to 0.51L/g.The aerothermal value increased from 2.79%to 3.09%,the volume fraction of CO2 gradually decreased,and CH4 increased first and then decreased.With the increasing of pyrolysis temperature,the volume fractions of H2 and CO increased from 4.28%and 7.8%to 6.23%and 10.78%,respectively,and the gas production increased from 0.25 L/g to 0.51 L/g,calorific value increased from 2.88%to 3.09%.The volume fraction of CO2 firstly increased and then decreased,and CH4 gradually decreased.Through TG-FTIR and fixed-bed pyrolysis experiments,the effect of anthracite on the pyrolysis characteristics of corn stalks was studied.The results showed:(1)As the blending ratio of anthracite increased,The co-pyrolysis reaction was shifted to the high temperature side,but the gas products precipitated were different from the added straw carbon.Corn stalk and anthracite had a significant synergistic effect during co-pyrolysis,but were lower than those of corn stalk and stalk charcoal.With the increasing blending ratio of anthracite,the activation energy of the reaction decreased from 84.75 kJ/mol to 47.71 kJ/mol.(2)The product distribution of pyrolysis by corn stalk and anthracite was significantly different from that of stalk charbon.With the blending ratio of anthracite increased from 0 to 100%,the volume fractions of H2 and CO increased from 3.14%and 9.03%to 5.75%and 10.11%,respectively,and the gas production increased from 0.23L/g to 0.47L/g.The calorific value of gas increased from 2.79%to 3.07%,and then decreased to 1.36%,the volume fraction of CO2 gradually decreased,and CH4 firstly increased and then decreased.(3)The difference between straw charcoal and anthracite on the pyrolysis behavior of corn stover may be due to the volatile content of straw char,O/C was higher than anthracite,H/C was less than anthracite,and the hydrogen-rich small molecules produced by pyrolysis of corn stover easy to combine with straw charcoal.Therefore,the co-pyrolysis of biomass and carbon should choose carbon with higher volatile content,higher O/C and lower H/C,which was more conducive to the interaction between the samples.