基于不同三组分模型解析生物质热解过程

Kinetic study of biomass pyrolysis based on different three-pseudocomponent models

三组分模型(three-pseudocomponent model)通常被用来表征生物质热解过程。传统三组分模型中单个模型的反应级数被限定为1或3。在本研究过程中,利用非线性最小二乘法,在不限定反应级数的前提下回归三组分模型动力学参数(活化能、指前因子、反应级数)。通过研究发现,纤维素(cellulose)分解反应级数接近1,与前人结果相一致。木质素(lignin)分解级数与生物质种类有关,接近于1或3。半纤维素(hemicellulose)的分解过程最复杂,其反应级数在1.5～4之间变化。以Ozawa方法计算得到的活化能作为相对标准,对3种三组分模型进行比较,发现反应级数未确定时的模型比其他两种模型更精确地表征生物质热解过程。

The biomass pyrolysis process usually could be expressed by a three-pseudocomponent model. The value of reaction order in the traditional three-pseudocomponent model is set as 1 or 3. In this study, the kinetic parameters of three pseudocomponents （activation energy, pre factor and reaction order） were calculated from the three-pseudocomponent model with undefined reaction order by the non-linear least square fitting method. The analysis result showed that the reaction order of cellulose decomposition was close to one, which agreed with the conclusions of other researchers. The reaction order of lignin decomposition was related to the type of biomass sample, and was close to one or three. The most complex process was hemicellulose decomposition. The reaction order of hemicellulose decomposition changed in the range of 1.5 to 4. Several three-peseudocomponent models based on the weight average activation energy calculated by the Ozawa method were compared. The three pseudocomponent model with undefined reaction order was more accurate than the other two models to describe the biomass pyrolysis process.