生物质气化燃气中固体颗粒物的恒温临氧热解机理研究

在固定床反应器中考察了不同气氛下PBG恒温热解特性的差异,结合XPS与~(13)C NM R等技术手段分析了400℃恒温热解条件下PBG固相产物的化学结构变化。结果表明,PBG在400℃恒温热解时,生物质气化燃气(BAG)与N_2气氛下更易生成焦油,其析出量分别为50.71与37.45 mg/g,而临氧燃气气氛(BAG+2%O_2)下焦油析出量仅为11.96 mg/g,说明适量O_2的存在可有效抑制焦油的生成。进一步进行化学结构分析表明,在燃气(BAG)恒温热解条件下,PBG主要发生以脱氢脱氧为主的芳香化缩聚反应,易形成焦油类的大分子多环芳烃;而在临氧燃气(BAG+2%O_2)恒温热解条件下,PBG表面的有机基团易与O_2发生表面氧化反应,生成表面含氧官能团,在一定程度上抑制了芳香环缩聚反应,进而有利于降低焦油类物质的产率。因此,在生物质气化燃气实际高温过滤过程中适当添加氧(如:2%O_2),可有效降低PBG焦油收率,且不会形成大分子多环芳烃,有助于解决粗燃气过滤的过滤介质堵塞问题。

Isothermal partial oxidative pyrolysis mechanisms of solid particles from biomass gasification

Isothermal pyrolytic characteristics of PBG at 400℃ under different reaction atmospheres in a horizontal tubular quartz reactor were investigated and compared. Meanwhile, chemical structures of PBG and its pyrolysis solid products were also analyzed with the help of XPS and ¹³C NMR methods. The results indicate that tar yields derived from PBG pyrolysis are 50.71 and 37.45 mg/g under biomass air gasification (BAG) and N₂ atmospheres, respectively, while 11.96 mg/g under BAG+2%O₂ atmosphere, which indicates that the presence of oxygen can inhibit the production of tar. Furthermore, the dominant reaction is characterized as the polycondensed aromatization involving dehydrogenation and deoxygenation in PBG under BAG atmosphere, tending to the formation of heavy organic compounds such as tar. While, surface oxygen-containing organic functional groups can be generated via the oxidation reaction between some surface functional groups of PBG and O₂ in PBG under BAG+2%O₂ atmosphere, inhibiting the aromatization of aromatic clusters and the formation of heavy organic compounds such as tar to some extent. Thus, the introduction of a limited amount of oxygen may be helpful for solving the pipe blockage during hot gas filtration of the raw BAG gas.