玉米秸秆沼渣热裂解及热动力学研究

采用热重法(TG)-微分热重法(DTG)-差热分析法(DTA)研究玉米秸秆沼渣热解过程及热裂解反应动力学特征和机理。研究结果表明玉米秸秆沼渣的失重过程分为吸附水蒸发阶段和秸秆裂解、挥发性物质蒸发阶段。热解过程中,加热速率对玉米秸秆沼渣热解有显著作用。使用FWO、KAS和Popescu方法计算出其热解活化能分别为233、359、358 kJ/mol。对41种常用热裂解动力学机理函数分析确定其热裂解动力学机理为三级方程g(α)=(1-α)-2。扫描时电子显微镜(SEM)分析表明,热裂解可破坏玉米秸秆沼渣的木质纤维束状结构,降低木质纤维中的木质素和半纤维素的质量分数,但效果随升温速度的增大而变差。

PYROLYSIS AND KINETICS OF CORN STOVE BIGOGAS RESIDUES

Thermal decomposition and kinetics of corn stove biogas residues were studied by TG-DTG/DTA. The TG-DTG curve showed the process of mass loss of the substance proceeded in two steps. The first stage could be attributed to the expulsion of water of crystallization. The second stage was corresponding to the devolatilization and decomposition of the molecular structure. Heating rate had a significant effect on the pyrolysis of the corn stove biogas residues. The activation energy E of the second stage of degradation process obtained by FWO,KAS and Popescu method were 233,359 and 358 kJ/mol respectively. According to Popescu mechanism functions,the possible kinetic model was estimated to be formula three g(α)=(1-α)-2. SEM showed that pyrolysis damaged the wood fiber beam structure of corn stove biogas residue,reduced the mass fraction of hemicellulose and lignin of wood fiber,but the effect got worse with the increase of heating rate.