热解压力对生物质焦结构及气化反应性能的影响

利用加压固定床反应器、吸附仪、X射线衍射仪、元素分析仪、电感耦合等离子原子发射光谱仪等考察了热解压力对生物质半焦(以下简称半焦)产率、物化结构、元素组成的影响规律。同时,利用热天平对不同热解压力下所制半焦的气化行为进行了考察。结果表明,随热解压力升高,半焦产率增大,当压力升至1.0 MPa后,半焦产率基本不变;半焦中C元素含量随热解压力的升高而增加,而H元素含量和BET比表面积则减小;此外,随热解压力升高,玉米秸秆焦和锯末焦的石墨化程度增强,而稻壳焦的石墨化程度则基本不受热解压力影响。气化反应的研究表明,玉米秸秆焦及锯末焦的平均气化反应速率随热解压力的提高而减小,而稻壳焦的平均气化反应速率基本不受热解压力的影响。热解压力对半焦BET比表面积及碳微晶结构的影响规律与气化反应速率变化规律的对比研究表明,热解压力引起半焦微晶结构的变化是造成热解压力对半焦气化反应速率影响的主要原因。

Effects of pyrolysis pressure on the properties and gasification reactivities of biomass chars

Biomass chars were prepared under different pyrolysis pressures in a pressurized fixed bed reactor. The evolution of chemical composition and physical structure of the biomass chars with the change of pyrolysis pressure were observed by BET, XRD, CHNS elemental analyzer and ICP-AES. The reactivities of biomass chars were evaluated by a thermogravimetric analyzer. The results show that the yields of biomass chars increase with increasing pyrolysis pressure, but reach a plateau above 1.0 MPa. With increasing pyrolysis pressure C content in biomass chars increases, while H content and BET surface area decrease. The degree of graphitization of corn stalk char and sawdust char increases with increasing pyrolysis pressure, while that of rice husk char shows almost no dependence on pyrolysis pressure. The average gasification rates of corn stalk char and sawdust char all decrease with increasing pyrolysis pressure, while pyrolysis pressure has little influence on the gasification rate of rice husk char. Compared the evolution of BET surface area and carbon crystallite structure of biomass chars with biomass char gasification rate, it shows that the difference of carbon crystallite structure of biomass chars, which was brought out by the change of pyrolysis pressure, mainly contributes to the difference of gasification rate of biomass chars prepared under different pyrolysis pressures.