生物质热裂解反应器对镍/木炭催化剂重复使用过程中积炭的影响研究

摘要

In order to investigate the effect of the type of reactor on carbon deposition and service life of Ni based catalysts in the process of biomass pyrolysis, a Ni/char catalyst was reused in a two-stage reactor and a three-stage reactor. The effects of pyrolytic volatiles from fir wood sawdust on the weight of catalyst were also studied. The results showed that the changes in the Ni/char weight depended on the two pathways, i. e. , the carbon deposition on the catalyst by the thermal cracking, and carbon losing by oxidation in the cracking process of fir wood sawdust. It was found that the carbon deposited on the Ni/char catalyst was more difficult to be oxidized than the char used as the carrier. The deposited carbon was presented in a form of carbon nanofibers. The Ni/char catalyst has longer cycle life in the three-stage reactor than that in the two-stage one. As a result, the three-stage reactor was recommended in the process of biomass gasification due to remarkable reduction of the cost in biomass gasification.%为了研究生物质热解气化过程中,反应器类型对镍基催化剂的积炭和使用寿命的影响,以杉木屑为原料,研究了Ni/木炭催化剂分别在二段式和三段式热裂解反应器内重复使用次数对杉木屑热裂解产物及其催化剂质量的影响规律。结果表明：在杉木屑热裂解过程中,Ni/木炭催化剂上会同时发生炭的沉积和炭的氧化消耗2个过程,其质量的变化受这2个过程共同的影响,且镍基活性中心上的积炭比载体木炭更难以被氧化消耗。沉积在Ni/木炭催化剂上的炭主要是以纳米碳纤维的形式存在,且纳米碳纤维覆盖在金属镍上。在二段式反应器中,催化剂的质量是先减少,然后增加,再减少；而在三段式中,则是不断减少。采用三段式生物质热裂解反应器不仅可以显著延长Ni/木炭催化剂的使用寿命,而且可以充分利用热解气化过程所产生的副产物固体炭,从而降低生物质热解气化的催化剂使用成本。