Study On The Interaction Characteristics Of Fiber Composition In The Process Of Biomass Pyrolysis

Biomass energy,as a substitute for fossil energy,is playing an increasingly important role in the world’s energy system,and biomass pyrolysis is an important way for its high-value utilization.The pyrolysis process of the three major components(cellulose,hemicellulose and lignin)has been widely studied.However,biomass pyrolysis cannot be regarded as the summation of individual pyrolysis behaviors,and the cross-coupling of components will affect the pyrolysis process and product distribution.Based on this,with fast pyrolysis online analysis,secondary reaction of volatile matter,bio-char structure analysis as the starting point,and the interactions of cellulose-hemicellulose and cellulose-lignin as the research object,the main work is as follows:Firstly,the influence mechanism of the interaction between the components on the thermal weight loss characteristics,gas product precipitation and the evolution characteristics of functional groups was studied by thermogravimetric-Fourier infrared transform spectroscopy.The experimental results of thermal weight loss show that the thermal weight loss range of cellulose is the most concentrated,the decomposition is thorough,and the solid carbon yield is the lowest;hemicellulose is the most unstable and the depolymerization temperature is low;and the lignin has a complex structure and the most stable solid carbon yield.Highest;mixed pyrolysis of cellulose and hemicellulose with equal mass ratio is beneficial to volatilization analysis and the solid phase yield is lower,while cellulose and lignin are the opposite,and the pyrolysis kinetics experiment results show that the activation energy of mixed pyrolysis is higher low.Infrared studies have found that the interaction between hemicellulose and cellulose promotes the secondary cleavage of anhydrosugars and the production of small aldehydes and ketones;the interaction between cellulose and lignin is shown in the fact that lignin promotes the secondary pyrolysis reaction of cellulose.Cellulose promotes the pyrolysis of lignin to release aromatic compounds,and the interaction between cellulose and lignin has a promoting effect,which shows that the characteristic products of each pyrolysis are enhanced.Then,an online analysis of the pyrolysis process between the fiber composition was performed by a photoionization-time-of-flight mass spectrometer.At 400-500°C,the peak area of anhydrosugar corresponding to cellulose and hemicellulose mixed pyrolysis decreases,while the low-molecular-weight region(42-96)corresponds to an increase in the peak area of small molecules.However,600-700°C fiber The reforming of the molecular fragments of cellulose and hemicellulose increases the precipitation peak area of benzene.Cellulose can promote the production of ligninphenolic substances.On the one hand,cellulose molecular fragments can act as H donors to promote the removal of lignin active substances,which is manifested by the increase in eugenol and 4-vinylphenol content.On the other hand,Benzene comes from the reaction between cellulose and lignin molecular fragments,which increases benzene.The lignin will promote the secondary reaction of cellulose,so that the content of dehydrated sugars is reduced,while the content of small molecular hydrocarbons increases.Next,A closed micro pyrolysis reactor was used to study the influence of the secondary reaction of the volatiles between the fiber component molds on the interaction.Studies have found that glucose reduces the activity of the guaiacol methoxy group,the branched structure of eugenol is well preserved,and the types of phenolic products in the pyrolysis product are significantly reduced,and the degree of enrichment increases,and the synergy promotes The conversion of dianhydrosugars to linear compounds;however,co-pyrolysis promotes the pyrolytic conversion of 2,6-dimethoxyphenol,and phenolic substances represented by 2,6-dimethylphenol increase;while phenol And2,6-dimethoxyphenol increase the furan products.The experimental results show that glucose has obvious selectivity for the pyrolysis of phenols.Levo-glucan has a certain promoting effect on the methoxy reforming reaction of guaiacol and 2,6-methoxyphenol,but it has an inhibitory effect on the pyrolysis of eugenol,while phenol has an effect on LG ring-opening cracking.Has a promoting effect.Furfural is stable at 600°C and is not easy to decompose;the results of co-pyrolysis experiments show that furfural intensifies the methoxy recombination reaction,which increases the content of 2-methylphenol and catechol in the guaiacol pyrolysis product and The variety of 2,6-dimethoxyphenol pyrolysis products increased and the content of low-carbon olefins increased;furfural reduced the activity of the eugenol branching reaction but intensified the benzene ring condensation reaction.Finally,Two-dimensional infrared spectroscopy was used to study the effect of component interaction on the chemical structure of biochar.The study found that the cellulose-hemicellulose interaction at 300°C showed an increase in the solid yield and a decrease in the gas-liquid yield.With the increase of hemicellulose,the change trend of C-O-C and C=O bond in the corresponding char structure is the same,indicating that the cellulose ring opening and the removal of hemicellulose glucuronic acid side chain occur simultaneously.The change of the C-H bond of the aliphatic chain is later than that of the xylosyl C-O bond.The intermediate product of hemicellulose promotes the ring-opening reaction of cellulose,and the dehydrated sugar in the liquid oil gradually decreases compared with the predicted value.The formation of conjugated carbonyl C=O bond in cellulose-hemicellulose char at 500°C is synchronized with the formation of C-O bond and C-H bond bending vibration,and the change of aryl group C-C bond.The interaction makes the cellulose and hemicellulose to polyphenyl ring char evolution.The interaction between cellulose and lignin at 400°C shows that cellulose promotes the removal of lignin branches and aromatization processes,and lignin promotes the dehydration and further decomposition and transformation of cellulose.However,at 650°C,the strength of the functional group becomes smaller and the abundance becomes lower,and a large number of small molecular fused rings begin to form inside the char,and the peak positions of the asynchronous spectrum are intricate.