Modulation Of Composition Of Syngas By Material In Biomass/Coal Co-gasification Process

Co-gasification of biomass and coal is one of the effective methods to solve the fossil energy crisis and the pollutant emission problem in fossil energy utilization.It is of great significance to resolve the contradiction between the increase in energy consumption and the reduction of emissions of gaseous pollutants.Biomass energy is clean,renewable energy and emits nearly zero CO₂during the whole life cycle.However,due to high biomass volatilization and low ignition point,it is easier to react with oxygen to form CO₂ and H₂O than coal,which not only reduces the elemental utilization of C,H,and O in biomass,but also decreases reactor temperature to affect the gas composition due to the lower calorific value of biomass during co-gasification of biomass and coal.How to avoid the shortage of low energy density of biomass in the co-gasification process of biomass and coal and make full use of the high gasification reactivity of biomass char and the catalytic effect of alkali metals rich in biomass on coal gasification.This is very important for the development and application of adsorption and release behavior technology for biomass/coal co-gasification.The two-stage fluidized bed reactor built in this paper is used.The effect of biomass addition in the combustion zone and its addition to the reducing zone on the composition of co-gasification gas production is investigated,and the variation law of gas production composition caused by factors such as biomass addition ratio,water/carbon ratio and temperature in the reduction zone is also explored.The above experiment can obtain the law of the chemical environment change of reactor caused by different feed positions and the corresponding influence on the C/H ratio of product,so that it can satisfy the proportion of elements required for synthesis to the greatest extent.Through the addition of biomass and coal in different positions in the reactor,the law of chemical environment change of the reactor caused by different feed positions and the corresponding influence on the C/H ratio of the product are obtained,so that the proportion of elements required for synthesis can be maximized.in order to further clarify the heat transfer process of the two materials,the co-gasification process is decoupled into two processes of co-pyrolysis coke and coke gasification,and determination and analysis of heat transfer in coal/biomass co-pyrolysis process is analyzed by synchronous thermal analyzer.Main conclusions are as follows:1.In coal/biomass co-gasification process,the addition of biomass and coal in different reaction zones directly causes changes in the chemical environment of reactor,which can affect the composition and gasification efficiency of co-gasification gas.?1?When the added biomass and coal are not mixed together into the reactor,the biomass is in a strong oxidizing environment,and the H₂ and CO content of coal gasification products biomass combustion products can be reduced from 40.41%and 36.39%to 34.94%and 30.05%,respectively,due to biomass burning.If the added biomass is in a reducing environment,the H₂ and CO content in coal gasification product can be increased from 40.41%and 36.39%to 45.35%and 38.83%,respectively,because of the presence of biomass gasification product.?2?When added biomass and coal are mixed into the reactor,but the biomass is in a vigorous reduction zone,the H₂ and CO content in mixture gasification gas increases,and CO₂ content decreases with the increase of biomass added ratio.At the same time,the utilization ratio of C,H and O in the raw materials is obviously improved.In addition,with the increase of H₂O/C ratio in the reduction zone,the content of H₂ in gas production increases,and the content of CO and CO₂ decreases,which is contributed to improving the utilization of C and H and harmful to the utilization of O element in raw materials.As increases the reduction zone temperature,the content of CO and H₂ can be increased and the CO₂ content in the gas production can be reduced,and the element utilization of C,H and O in the raw material can be increased.?3?When biomass is mixed with coal and added to reactor,and biomass and coal materials are in the mild reduction zone,the H₂ and CO content in the mixture gasification gas increases as the biomass addition ratio increases.As the biomass ratio changed from 0 to20%,the H₂ and CO contents increased from 41.2%and 30.8%to 47.6%and36%,respectively,and the CO₂ content decreased from 27.3%to 15.5%.Meantime,when the biomass blending ratio in weak reduction zone is 20%,the utilization ratios of C,H and O in raw materials are increased by 13%,13%and11%respectively.In addition,with the increase of H₂O/C ratio in weak reduction zone,the content of H₂ in gas production increases,and the content of CO and CO₂ decreases,which is beneficial to improve the utilization of C and H elements and not conducive to the utilization of O element in raw materials.Increasing the reduction zone temperature can increase the content of CO and H₂ in gas production,reduce the content of CO₂,and increase the utilization ratio of C,H and O in the raw material.2.The DSC curve obtained by the simultaneous thermal analysis experiment is processed and integrated to obtain the heat absorption of the raw material when the pyrolysis process reaches the final pyrolysis temperature.The amount of heat absorbed by the co-pyrolysis process decrease as the proportion of biomass added increases.When the biomass addition ratio is 20%,the heat required for pyrolysis is 1176.3 J/g and is lower than the 1333.8 J/g required for pyrolysis of individual coal.