Syngas Production From Pyrolysis/Gasification Of Biomass Within Carbonate Salts

Both biomass pyrolysis and gasification can achieve energy efficient conversion,which are beneficial to the development and utilization of biomass energy.Among the productions,the syngas composed of H₂ and CO is an important chemical raw material.While carbonates can be used as heat carriers and catalysts,so it is a reasonable way for using biomass energy to produce syngas from pyrolysis or gasification of biomass under the role of carbonates.The production of hydrogen-rich syngas from pyrolysis process of fir sawdust by adopting molten Li₂CO₃-Na₂CO₃-K₂CO₃?LNK?salts as heat medium and catalyst was investigated firstly.The influences of pyrolysis temperature,feeding time,carrier gas flow and metallic oxides added into carbonate salts on the yields and distributions of gas composition were investigated.The results illustrated that the yield of hydrogen showed an increasing tendency first and then declining tendency with rising temperature,the maximum reached 7.55mol/kg biomass at 750?.High temperature was favor of the production of syngas,its yield and content attained the highest values at 800?which were up to 14.40mol/kg biomass and 68.03%respectively.As feeding time extended,the yield of hydrogen,the yield and content of syngas increased firstly and decreased subsequently,their maximum values were up to 7.55mol/kg biomass,12.88mol/kg biomass and 64.49%when the feeding time maintained at 60min.The syngas possessed a highest yield with raising carrier gas flow,which could come up to15.30mol/kg biomass at 60.7L/h.Metallic oxides added into the salts could promote pyrolysis of fir sawdust and formation of syngas,and the improving effects of Cr₂O₃was the most remarkable on syngas yield and content,which were 15.31mol/kg biomass and 62.47%respectively.Li₂CO₃-Na₂CO₃-K₂CO₃ was selected as the basic molten salt in a lab-scale gasification plant,CO₂ gasification was conducted on the experimental study of fir sawdust.The influences of gasification agent CO₂ flow with sweeping and bubbling methods,respectively,metallic oxides added into carbonate salts and Cr₂O₃ content on the distributions of gas composition and yields were investigated.The experimental results showed that the maximum syngas content of 59.99%obtained through sweeping method,and that of 61.37%obtained through bubbling method.Compared with them,the bubbling method demonstrated excellent results than sweeping method for its agitation,the maximum syngas content and yield were up to61.37%and 14.48mol/kg biomass when the CO₂ gas flow maintained at 99.8 L/h,respectively.Among four metal oxides such as Fe₂O₃,MgO,Cr₂O₃ and Al₂O₃,Cr₂O₃was more efficient to the gasification experiment,and the synthesis gas content is67.91%.With the increase of Cr₂O₃ content,the content of syngas increased firstly and decreased subsequently.At the weight ratio of 11.1%,the syngas content and yield were the highest,which were 67.91%and 12.55 mol/kg biomass,respectively.This study provided an useful reference for the energy utilization of agricultural forestry waste and hydrogen-rich syngas production.