The Experimental Study On The Characteristics Of Gas And Tar Evolution During Pyrolysis And Gasification Of Typical Biomass

Nowadays, two major challenges loom large in the environmental pollution andshortage of energy. The resource utilization of biomass energy, which is abundant,“carbondioxide neutral” and renewable, has attracted increasing worldwide interest. Biomassgasification is one of the efficient approaches and the target product of this technology isgas. The end-use of the product gas is wide, for example, it is the raw material forFischer-Tropsch or fuel cells. Rice husk is one of the agricultural residues available inChina, the experimental study on the pyrolysis and gasification of this typical biomass wasperformed, and both the gas and tar evolution patterns were studied in details during theprocesses.Firstly, the pyrolysis and steam gasification of rice husk were studied using alaboratory fixed bed with a Gasboard-3100gas analyzer in different temperatures. Nomatter there was water vapor or not, the volatile of rice husk released rapidly when thebiomass was in reaction zone. Especially, the water gas reaction could produce moregaseous products when water added. The yield of gas was increasing with temperature.Secondly, the influence factors of steam gasification were studied, such as particle size,residence time and biomass kind. The yield of product gas increased with smaller particlesize or longer residence time, but the gas composition was effected rarely. The yield of gas,especially hydrogen, of steam gasification was much more than the yield of pyrolysis. Inaddition, the reaction activities of three kinds of biomass were different, and the sawdust’swas the highest. The gasification rate enhanced when CaO, MgO or Fe₂O₃was added ascatalyst. The maximum of gas yield was attained when using CaO, and Fe₂O₃couldcatalyze CH₄reforming.Lastly, the main components and yields of tar, which was collected by cold trap, wereanalyzed by GC/MS and gravimetric method respectively. Both elevated temperature andthe addition of water vapor could promote the tar cracking, while the content of aromatichydrocarbons was increased; CaO, MgO or Fe₂O₃could also promote tar cracking, theability in turn was Fe₂O₃>CaO> MgO, what’s more, the complexity of tar was decreasedusing Fe₂O₃.