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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C 208H 199O 23N 3S的不黏煤分子模型。在不同O 2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O 2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CO 2主要反应的总次数为1 781次,低于消耗CO与H 2O主要反应总次数,提高温度和O 2分子数使得相对稳定的CO 2产量峰值增幅更大。提高O 2分子数对H 2O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、CO 2及H 2O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 (C 208H 199O 23N 3S) is developed. Utilizing the reaction molecular dynamics (ReaxFF MD) method, molecular dynamics simulations of coal combustion are performed under varying O 2 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 O 2 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 CO 2 was 1 781, which was lower than the total number of primary reactions consuming CO and H 2O. Increasing temperature and the number of O 2 molecules caused a greater increase in the peak yield of relatively stable CO 2. The peak yield of H 2O initially increased and then decreased with the increase in the number of O 2 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, CO 2, and H 2O were the polymerization of free radicals or the decomposition of small molecule compounds.

     

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