Abstract This paper presents pyrolysis simulations of a multi-component structure model of Fugu sub-bituminous coal containing 23,898 atoms with ReaxFF MD. The slow heat-up and long-time isothermal simulations were performed using the GPU-enabled ReaxFF MD code of GMD-Reax and reaction analysis code of VARxMD. The simulated pyrolyzate evolution trends and pyrolysis stages proposed based on lumped pyrolyzates agree fairly with literature. Major reaction pathways for early generation of CO2, H2O, CH4 and H2 in the activation and primary pyrolysis stages are found closely associated with carboxyl and methoxyl groups, indicating the significant role of oxygen-containing groups in the initialization of Fugu coal pyrolysis. Compared with reported experiments, the coal tar yield is over-predicted, while the gas yield is slightly under-estimated. To shorten the simulation time from 2 ns to 250 ps, an increase of 400 K in average on the basis of temperature range of 1200–2200 K is needed that will result in the over-prediction for the yields of gas and tar, as well as under-prediction for the non-volatile yield. This work suggests that ReaxFF MD simulation is useful for revealing the overall scenario and detailed reactions in coal pyrolysis but cautions should be taken for proper elevated temperatures.

中文翻译：

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府谷煤的大规模 ReaxFF 分子动力学热解模拟

摘要 本文采用 ReaxFF MD 对含 23,898 个原子的府谷次烟煤多组分结构模型进行了热解模拟。使用 GMD-Reax 的支持 GPU 的 ReaxFF MD 代码和 VARxMD 的反应分析代码执行缓慢加热和长时间等温模拟。基于集总热解物提出的模拟热解物演化趋势和热解阶段与文献相当吻合。发现在活化和初级热解阶段早期生成 CO2、H2O、CH4 和 H2 的主要反应途径与羧基和甲氧基密切相关，表明含氧基团在府谷煤热解的初始化中起重要作用。与报道的实验相比，煤焦油产量被高估，而天然气产量略有低估。为了将模拟时间从 2 ns 缩短到 250 ps，需要在 1200-2200 K 的温度范围的基础上平均增加 400 K，这将导致对气体和焦油产率的高估，以及作为对非挥发性收益率的低估。这项工作表明，ReaxFF MD 模拟可用于揭示煤热解的整体情况和详细反应，但应注意适当升高温度。