The Effect Of Natural Ore Catalyst On Biomass Pyrolysis

Under the double pressure of energy and environment,the development and utilization of biomass energy is paid more and more attention,and biomass pyrolysis gasification technology is the key technology of biomass energy conversion.This article is to suppress the tar,to obtain high-quality flammable gas as the ultimate goal,olivine and iron ore base catalyst was prepared,the effect of experimental condition and catalyst on pyrolysis process of cotton has also investigated,meanwhile,the pyrolysis process was analyzed by kinetic analysis,reveals the reaction rule of biomass pyrolysis process,puts forward the mineral base load nickel catalyst influence mechanism of biomass pyrolysis.The results are as follows:The thermal weight loss?TG-DTG?curves were obtained,the pyrolysis of cotton stalk and walnut shell can be divided into four stages:water loss,transition,main pyrolysis and carbonization.,the greater the heating rate,the greater the weight loss rate and the weight loss rate.The weight loss rate,weight loss rate,hemicellulose and volatile content of walnut shell were higher than that of cotton stalk,and the activation energy was lower than the cotton stalk,indicating that the walnut shell was more prone to pyrolysis reaction.Using the method of the Coats-Redfern,the pyrolysis parameters obtained in the reaction series n=1 had the best correlation,indicating that the first-order model could well describe the pyrolysis process of cotton straw and walnut shell.The results of Doyle's and Ozawa's methods were basically the same,and the activation energy obtained by Ozawa method was higher than that of Doyle and Coats-Redfern.The pyrolysis experiment of a fixed bed reactor was carried out,With the increase of pyrolysis temperature,the content of semi-coke,tar and CO₂ decreased,and content of the total gas,H₂ and CO were increased.When the pyrolysis temperature is 650?,the content of tar and CO₂ is the smallest,and the total gas,H₂and CO are the most.Nickel catalyst promoted the tar cracking,water-gas transformation and the reforming reaction of methane,cotton,walnut shell,the content of total and H₂ gas increased to 50%and 30%,the tar were reduced to 10%.With the increase of NiO amount,production rate of tar and carbocoal gradually reduced,the syngas content increased gradually,when nickel loads 7%,the content of tar,CO₂ and CH₄ were lowest,the content of total gas,H₂ and CO were highest.However,NiO self-reduction consumes a certain amount of pyrolysis gas,and the excessive NiO load leads to the decrease the content of H₂ and CO in the gas production,and the increase of CO₂ content.Therefore,NiO content should not be too high.The pyrolysis of the tar in four kinds of catalysts is:NiO-olivine>NiO-iron ore>Calcined olivine>Calcined iron ore.According to the influence of the nickel catalyst on the pyrolysis process of biomass and the analysis of XRD,TPR and SEM of catalysts before and after the experiment,the influence mechanism of the nickel catalyst on the pyrolysis of biomass was proposed:During the process of pyrolysis,NiO olivine,NiO catalyst iron ore on the surface of the part NiO is a reducing gas in the pyrolysis gas reduction into elemental Ni,at the same time,Olivine,iron ore surface part of Fe₂O₃ is reduced to Fe₃O₄.In this process,catalyst on biomass pyrolysis has a dual role:on the one hand,the catalyst has a catalytic effect of biomass pyrolysis tar cracking,promoting steam reforming reaction produced by pyrolysis tar and improve syngas content in gas,and inhibit the pyrolysis process of secondary polymerization between free radicals.On the other hand,the presence of catalyst to further promote the pyrolysis reaction rate of raw materials,to promote the further pyrolysis carbocoal,raised in the process of biomass pyrolytic carbon conversion rate and utilization rate of raw materials.