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基于ReaxFF的不黏煤燃烧过程中自由基及主要燃烧产物生成规律研究

Study on the formation law of free radicals and main combustion products in non-caking coal combustion process based on ReaxFF

  • 摘要: 为了探究不黏煤燃烧过程中自由基及主要燃烧产物生成规律,采用X射线光电子能谱(XPS) 和核磁共振谱(13C NMR)实验方法,对不黏煤进行表征分析,构建了分子式为C208H199O23N3S的不黏煤分子模型。在不同O2分子数与温度条件下,应用反应分子动力学(ReaxFF MD)方法进行不黏煤的燃烧分子动力学模拟,探究其燃烧过程中自由基与主要产物的生成与消耗规律。研究结果表明:消耗OH自由基主要反应的总次数为1 906次,消耗H自由基与O自由基的总次数分别为3 733、2 033次,提高温度和O2分子数使得相对稳定的OH自由基产量峰值增幅更大,H自由基与O自由基的产量峰值增幅相对较小;消耗CO2主要反应的总次数为1 781次,低于消耗CO与H2O主要反应总次数,提高温度和O2分子数使得相对稳定的CO2产量峰值增幅更大。提高O2分子数对H2O的产量峰值影响呈现先促进再抑制的趋势;H自由基、O自由基及OH自由基主要由小分子化合物或其他自由基发生分解反应生成。自由基聚合或小分子化合物分解反应是CO、CO2及H2O生成的主要路径。

     

    Abstract: To explore the formation mechanisms of free radicals and major combustion products during the combustion of non-caking coal, this study conducts a comprehensive characterization analysis of non-caking coal using X-ray photoelectron spectroscopy (XPS) and 13C NMR nuclear magnetic resonance spectroscopy. A molecular model of non-caking coal (C208H199O23N3S) is developed. Utilizing the reaction molecular dynamics (ReaxFF MD) method, molecular dynamics simulations of coal combustion are performed under varying O2 molecule numbers and temperatures to explore the generation and consumption patterns of free radicals and main products. The results indicate that the OH free radical was consumed 1 906 times in total, while the H and O free radicals were consumed 3 733 times and 2 033 times respectively. Increasing temperature and the number of O2 molecules resulted in a more significant increase in the peak yield of relatively stable OH free radicals, with smaller increases in the peak yields of H and O free radicals. The total number of primary reactions consuming CO2 was 1 781, which was lower than the total number of primary reactions consuming CO and H2O. Increasing temperature and the number of O2 molecules caused a greater increase in the peak yield of relatively stable CO2. The peak yield of H2O initially increased and then decreased with the increase in the number of O2 molecules. H, O, and OH free radicals were primarily generated through the decomposition of small molecule compounds or other radicals. The main pathways for the formation of CO, CO2, and H2O were the polymerization of free radicals or the decomposition of small molecule compounds.

     

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