Study On The Effect Of Torrefaction On Physicochemical Properties And Gasification Characteristics Of Corn Straw

There are nearly 100 million tons of agricultural straw waste in China every year,most of which are simply burned leading to serious environmental pollution problems.Biomass gasification technology is a clean utilization method,in which biomass can react with gasification agents at a certain temperature to produce production gas containing CO,H₂,CH₄,C_mH_n alkane hydrocarbons.However,in view of the low grade of biomass,as well as the defects of excessive moisture,high oxygen content,low energy density,and difficulty in transport and storage in biomass feedstock,it leads to the high cost of its use as a renewable energy source,thus limiting the in-depth development of biomass gasification process.As an efficient pretreatment method,torrefaction can improve the biomass properties and has an important impact on the subsequent gasification.Based on this,this paper analyzes the effect of torrefaction on the physicochemical properties of corn straw,investigates the changes of gas phase products during torrefaction,analyzes the effect of torrefaction pretreatment on the reactivity and gas production characteristics of corn straw pyrolysis char gasification,and calculates the kinetic parameters.The torrefaction pretreatment experiments on corn straw using a horizontal fixed-bed reactor experimental system showed that the torrefaction pretreatment could change the elemental composition of corn straw,resulting in lower O content,lower volatile content and higher calorific value in corn straw.During the torrefaction process,the main gases released from corn straw were CO₂ and CO,and the release of each gas tended to increase with the increase of torrefaction temperature,with the most obvious change in CO₂.This paper also found that some toxic gases containing N will be produced during the torrefaction process,and the gas emission problem should be considered in the actual production process.In this project,CO₂ and steam gasification experiments of corn straw char and roasted corn straw char were carried out separately using a micro fluidized bed reactor experimental system,and the kinetic parameters of raw corn straw char and roasted corn straw char were calculated using the iso-conversion method.The torrefied pretreated corn straw char showed better gasification reactivity than the raw corn straw char for both CO₂ gasification and steam gasification.In the steamization process,the gas production rate of each gas component of the torrefied pretreated corn straw char was generally larger than that of the raw char.The total yield of H₂ increased by about 94%for torrefied straw char compared to raw char.the total yield of CO decreased slightly,and the total yield of CO₂ and CH₄decreased,although the gas production rates of CO₂ and CH₄ increased.The volumetric concentration of H₂ produced by the gasification of torrefied corn straw char increased by about 16%compared to corn straw char,and the value of H₂/CO increased from 1.15 to 1.73.The experimental data indicated that the torrefaction pretreatment increased the yield of steam gasification syngas from corn straw char,especially the yield of hydrogen,which in turn improved the quality of corn straw char gasification syngas.