应用分布活化能模型分析伊敏褐煤丝炭腐植酸热解及氢气生成动力学

Kinetic Analysis of a Pyrolysis Process and Hydrogen Generation of Humic Acids of Yimin Lignite Fusain Using the Distributed Activation Energy Model

应用开放体系的热重-质谱(TG-MS)联用技术在5、20和50℃·min-1三个升温速率下对伊敏褐煤丝炭腐植酸(F-HA)和脱灰丝炭腐植酸(DF-HA)的热解行为进行了分析,并利用分布活化能模型(DAEM)分别对其热解和氢气生成动力学进行分析,获得了热解过程和氢气生成的活化能分布函数.结果表明:(1)F-HA热解活化能分布函数呈类Gaussian分布,且具有一定的对称性,主峰位与标准Gaussian分布相一致;DF-HA热解活化能分布函数也呈类Gaussian分布形式,主峰位与Gaussian分布相比,偏向低活化能值.根据转化率与温度、活化能的关系,结合腐植酸的热失重特征,将F-HA热解过程划分为四个阶段,DF-HA热解过程划分为五个阶段,并对腐植酸热解过程中各阶段的化学反应进行了详细讨论.(2)F-HA和DF-HA热解氢气生成活化能分布函数均呈类Gaussian分布,热解氢气生成活化能的整体趋势为随着转化率的升高而增加,但也表现出一定的阶段集中分布特征.根据热解氢气生成的动力学特征,将其生成过程划分为五个阶段,反映了其生成的不同化学反应机制.(3)酸洗脱灰对伊敏丝炭提取出的HA的热解行为、热解过程及热解氢气生成动力学产生了影响.

The thermal behavior of humic acids of fusain （F-HA） and humic acids of demineralized fusain （DF-HA） were investigated at heating rates of 5,20,and 50℃·min-1 using an open system thermogravimetric analyzer coupled to a quadrupole thermogravimetry mass spectrometer （TG-MS）.The pyrolytic and hydrogen generation kinetics were analyzed using the distributed activation energy model （DAEM） and the distribution functions of the activation energy were obtained.The results indicated：（1） the distribution function of the activation energy for F-HA has an asymptotic approximation to a Gaussian distribution during pyrolysis.Moreover,it has some symmetry properties and the same peak value as a standard Gaussian distribution.The distribution function of the activation energy for DF-HA has an asymptotic approximation to a Gaussian distribution during pyrolysis and its peak value is less than that of a standard Gaussian distribution.According to the conversion ratio vs temperature,activation energy relationships and the thermal mass loss features of humic acids,four and five stages of a general pyrolytic process were found for F-HA and DF-HA,respectively.The chemical reactions for each stage of the pyrolytic process are discussed in detail.（2） The distribution functions of the activation energy of hydrogen generation for F-HA and DF-HA have an asymptotic approximation to a Gaussian distribution during pyrolysis.The activation energy of hydrogen generation increased with an increase in the conversion yields but it also showed staged features.Based on the kinetic characteristics of their generation during pyrolysis their hydrogen generation processes can be divided into five stages,which reflect the different chemical reaction mechanisms.（3） The demineralization of Yimin fusain influences the thermal behavior,kinetics of the pyrolytic processes and the hydrogen generation of humic acid.