Investigation and improvement of the kinetic mechanism for methanol pyrolysis
Investigation and improvement of the kinetic mechanism for methanol pyrolysis
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DOI：
10.1016/j.ijhydene.2017.05.042
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发表时间：
2017-06
影响因子：
7.2
通讯作者：
Mingchu Ran;Jun Shi;Juntian Niu;Changlei Qin;J. Ran
中科院分区：
文献类型：
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作者：
Mingchu Ran;Jun Shi;Juntian Niu;Changlei Qin;J. Ran
由于化石能源的短缺及其污染物的排放，醇类燃料的热裂解和燃烧利用越来越受到人们的关注。然而，目前还缺乏对其燃烧和热解过程准确预测的动力学机理的深入了解。为了进一步完善甲醇热解燃烧的动力学机理，采用带在线气体检测系统的活塞流反应器（温度873-1273 K，体积流量4.4- 34.2ml/s）进行了甲醇热解实验研究，分析了甲醇热解的反应路径，并利用CHEMKIN软件计算了甲醇热解的本征反应动力学。在此基础上，对甲醇热解过程进行了优化，并在实验结果的基础上，通过修正甲醇分解反应、甲醇和甲醛夺氢反应的速率常数，提出了改进的动力学机理，并结合计算数据和实验数据进行了验证。结果表明，甲醇在910 K开始分解，在1150 K完全转化，主要产物为氢气、甲烷和一氧化碳。甲醛是甲醇分解的重要中间产物，甲醇分解的两条主要路径为：CH 3OH → CH 2 O→ CO和CH 3OH → CH 3→ CH 4，这与前人的研究结果一致.甲醇分解的速率常数k可表示为k= 8.323× 103（s-1）exp [-64.05（J mol-1）/RT]。此外，机理验证表明，改进机理的计算结果与激波管实验结果吻合较好，尤其是对甲醇消耗量和CO含量的预测。
Due to the shortage of fossil energy and its pollutants emission, the utilization of alcohol fuel by pyrolysis and combustion has attracted increasing attention. However, there is still a lack of good understanding of the kinetic mechanism for accurate prediction of its combustion and pyrolysis process. In the paper, to improve the kinetic mechanism of methanol pyrolysis and combustion, an experiment was conducted to investigate methanol decomposition using a plug flow reactor (with temperature of 873–1273 K and volume flow rate of 4.4–34.2 ml/s) with on-line gas detection system, the reaction paths were analyzed and the intrinsic reaction kinetics of methanol decomposition was calculated with CHEMKIN. Then, the process of methanol pyrolysis was optimized, and an improved kinetic mechanism was proposed by modified the rate constant of methanol decomposition reaction, hydrogen abstraction reaction of methanol and formaldehyde based on the experimental results, and verified by the combination of calculated and experimental data. The results show that methanol starts decomposing at 910 K and reaches complete conversion at 1150 K, with major products of hydrogen, methane and carbon monoxide. Also, formaldehyde is an important intermediate species, and two dominant paths for methanol decomposition have been proposed: CH 3 OH→ CH 2 O→ CO and CH 3 OH→ CH 3→ CH 4, which are in good agreement with that proposed by previous studies. Meanwhile, the much accurate rate constant k of methanol decomposition can be expressed as k= 8.323× 10 3 (s− 1) exp [− 64.05 (J mol− 1)/RT]. Moreover, mechanism verification indicated that the calculated result with improved mechanism is highly consistent with that of experiment detected in shock tube, especially for predicting methanol consumption and carbon monoxide fraction.