Two-staged Pyrolysis Law Of Biomass And Analysis Of Bio-oil Characteristic Components

Biomass energy is the only renewable carbon source,biomass pyrolysis is a very important form of biomass energy utilization,and can be considered as a comprehensive performance of the pyrolysis behaviors of the three major components——cellulose,hemicellulose and lignin.The products from the direct pyrolysis of biomass are complex and difficult to separate.Therefore,the pyrolysis products of biomass can be separated preliminarily and the quality of bio-oil can be optimized by two-staged pyrolysis of biomass.Because pyrolysis temperature and biomass species are important factors of biomass pyrolysis,rice straw,cedar wood and dalbergia wood were selected as the representative biomass materials and two-staged pyrolysis at different first-stage temperature were studied.The pyrolysis and product release characteristics of three representative biomasses and their major components were studied by using Thermogravimetric-Fourier Transform Infrared（TG-FTIR）analysis based on the compositional analysis of them.The results show that the weight loss characteristics of biomass were closely related to its component distribution and the temperature at the weight loss peak depends on the lignin content of the biomass.In addition,the pyrolysis kinetics analysis was performed on biomass and its constituents,as a result of which,the value of E/lnA is opposite to the weight loss rate.Combined with the infrared spectra of the three components,the spectra of the three biomasses at the maximum weight loss rate were compared and analyzed.It was found that some of the cellulose pyrolysis products in the biomass were inhibited,and the peaks of CO₂ and H₂O during pyrolysis of cedar wood and dalbergia wood were slightly lower than others;the former may be induced by the interactions of cellulose and lignin,and the latter is due to the inhibitory effect of lignin on most of the dehydration products.Two-staged pyrolysis and direct pyrolysis experiments were carried out in a small fixed bed at 320℃.Tar yield of different samples ranged from large to small（coke yield from large to small）arranged as:cedar wood,dalbergia,rice straw.The content of liquid phase product in two-staged pyrolysis was less than its content in direct pyrolysis.However,the partial loss of bio-oil is acceptable compared with the advantage of two-staged pyrolysis to product subsection enrichment.Compared with the results of Py-GC/MS,the proportion of some products in the first stage is relatively increased,which may be because the pyrolysis time of the samples in the fixed-bed experiment is longer than that in the pyrolysis apparatus.The products of two-staged pyrolysis is more abundant;The phenols which appear in the low temperature stage of two-staged pyrolysis belong to guaiacols;The levoglucose and most of the phenols are enriched in the middle temperature range.In a word,the effect of two-staged pyrolysis on reducing the complexity of pyrolysis products is significant.