榆木木屑慢速热裂解过程中气体的逸出规律

Evolution profiles of gases evolved during slow pyrolysis of elm sawdust

为掌握榆木木屑的热裂解特性,该文利用热分析/质谱联用技术研究了榆木木屑在20℃/min升温速率下的慢速热裂解过程。主要探讨了水蒸汽、甲烷、氢气、一氧化碳、二氧化碳等7种小分子气体在慢速热裂解过程中的逸出规律。气体逸出和失重主要发生在升温阶段,恒温温度越高,气体越容易逸出。在榆木木屑加热至380℃和480℃并恒温1.5h的过程中,所有逸出气体峰值对应的温度约为350℃。通过计算质谱图中逸出气体的峰面积,比较了7种逸出气体的相对体积含量,结果表明,水蒸汽、一氧化碳和二氧化碳的含量较高,水蒸汽相对含量超过50%,而氢气、甲烷、乙烷和丙烯在逸出气体中含量较低。

In order to grasp elm sawdust pyrolysis behavior,slow pyrolysis of elm sawdust at the heating rate 20℃/min was studied in this paper by utilizing thermal analysis coupled with mass spectrometry technique.The evolution profiles of seven kinds of small-molecule gases including water vapor,methane,hydrogen,carbon monoxide,carbon dioxide etc.were discussed.Gases emission and mass loss occurred at the heating stage.Gases emission tended to take place under higher isothermal temperature.Results also showed that the emission peak of these gases was located at about 350℃when the elm sawdust was heated to 380℃and 480℃and then was kept isothermal state 1.5 hours. Relative volume percentage of the gases was compared by calculating their peak area of mass spectrum.It was found that water vapor,carbon monoxide and carbon dioxide had a much higher amount of relative volume percentage.The water content was more than 50%.The relative volume percentage of hydrogen,methane,ethane and propene were rather small.