Pyrolysis/gasification Of Biomass For Hydrogen-rich Gas In Free-fall Bed Reactor

Pyrolysis, gasification and catalytic gasification of some kinds of biomass (including Legume Straw, Pine Sawdust, Rice husk, Apricot Stone, TobaccoStalkand Walnut Shell) in free-fall bed reactor were studied, which was applied to determine optimum operation conditions that could enhance hydrogen-rich yield. In addition, simple analysis of bio-oil and char from pyrolysis and gasification were performenced, and it was discussed to effects on composition of bio-oil and char with different technologies.During fast pyrolysis of biomass in free-fall bed, aseries of experiments have performed to investigate the effects of pyrolysis temperature, particle size and fuel type on product distribution and gas composition. High temperatures contributed to produce more gas and increase concentration of H₂ and CO. Particle size also had influence on product gas. Smaller particle size favored gas yield, which exhibited negative effect on liquid and solid yield. High heating rate caused by small particle size may be one possible explanation for this. As its rapid heating rate favoring high gaseous product and H₂ concentration. Fuel type is also one factor on product gas. Biomasses with high cellulose and hemicellulose content produce higher gas yield and relative high concentration of hydrogen than other biomasses, which have low cellulose and hemicellulose content. Products distribution and gas composition from fast pyrolysis are relevant to chemical composition of biomass. Among thermal conversion of biomass to hydrogen-rich gas, biomass which has high cellulose and hemicellulose content is preferred.Non-catalytic and catalytic Gasification of the legume straw and sawdust were studied in a free-fall bed reactor filled with nitrogen. The effects of the gasification temperature, the S/B value and the catalyst on the distribution of gasification products were investigated for the optimization of the process to achieve maximized yield of hydrogen-rich gases. Higher temperatures favored gaseous products and inhibited the formation of liquid or solid products. A high temperature in combination with a high S/B value was found to promote the formation of H₂ and CO₂ and hampered the formation of CO and CH₄. Catalysts promote cracking of bio-oil and quality of gas obtained from gasification, and calcined dolomite was found the best in favoring the gaseous products including H₂.Analysis of bio-oil show that oil from fast pyrolysis, gasification and catalytic gasification of Pine Sawdust has high organic acid content; Infra-red spectrometry of asphalt fraction of bio-oil suggest that small molecule fractions break away from raw materials with participate of steam and catalysts.Analysis of char of Pine Sawdust, which has different origin, show that gasification performance better in absolute cracking of organic matters in biomass, and catalysts propel its development; gasification and catalytic gasification favor reactivity of char; surface area of Pine Sawdust is small, which is not appropriate for preparation of porous materials.