Study On The Adsorption Capacity And Structural Revolution Of Torrefied Cornstalk By Oxidative Torrefaction

Torrefaction is a thermochemical pretreatment method with tremendous application potential,which is used to improve the combustion characteristics of biomass.This article mainly discusses the impacts of torrefaction temperature,torrefacton atmosphere and the moisture content of raw cornstalk on combustion characteristics and microstructure evolution of solid products,and their performance of adsorption of methylene blue together with adsorption kinetic through proximate analysis,elemental analysis,nitrogen adsorption and desorption experiments,scanning electron microscopy?SEM?,Fourier infrared spectroscopy?FTIR?and methylene blue adsorption experiments.Initially,the effects of different operating conditions?temperature,atmosphere and sample moisture content?on the composition,mass yield,energy yield and calorific value of baked solids were analyzed.The results showed that in nitrogen torrefaction,the ratio of H/C and O/C decreased with the increase of temperature,and the calorific value increased to 23.67 MJ/kg^-1;Air atmosphere can promote the devolatilization in the baking process,which will adversely affect the solid yield,energy yield and calorific value.Secondly,the effects of temperature,atmosphere and moisture content on the specific surface area,pore volume,pore diameter distribution and fractal dimension of solid products were investigated.It was found that the surface area and pore volume of the roasting products were much lower under nitrogen.The pore structure of production from air torrefaction was significantly different from that under nitrogen atmosphere.The specific surface area and pore volume of products increased,while the average pore size will decrease.A high moisture content in raw corn straw improved the development of pores with an increase of specific surface area and small pore diameter pores.In addition,the spectrum shows that the products from air torrefaction were rich in oxygen-containing functional groups,such as carboxyl,hydroxyl and lactone.Finally,the adsorption experiments indicates that kinetics of methylene blue adsorption process conformed to the secondary dynmics equation,and activation energy of adsorption processes were 7.65,18.21 and 7.21 KJ/mol,respectively,suggesting in the process existing physical adsorption and chemical adsorption and dominating by physical adsorption.Besides,the gibbs free energy of adsorption progress implied that the adsorption process of live adsorption process occurred spontaneously.