单一应力下义马原煤热解产物演变规律及动力学模拟

Evolution and kinetic simulation of pyrolysis products from Yima coal under single stress

以义马原煤为研究对象,构造晶胞,在ReaxFF力场中施加5×10^(9)s^(-1)的应变率,模拟1000K,1500K,2000K,2500K,3000K终温下义马原煤热解演化过程,分析单一应力对褐煤热解的作用效果。结果表明:不同模拟终温下,不同方向上的应力是上下波动的,在允许一定误差下,应力范围保持在±70GPa之间,即此应力对褐煤热解的作用受温度的影响较弱。模拟过程中,在26ps~33ps之间分子数出现极小值点而种类数出现极大值点,义马原煤热解模拟起始温度点不变,但缩聚反应的温度区间前移,表明反应前期单一应力作用效果优于温度作用效果,应力促进了整体的反应进程。受缩聚反应的影响,CO,CH_(4),H_(2)O和NH_(3)含量先升后降,符合热解一般规律,说明应力没有改变反应的最终趋势。H_(2)和·H的数量随反应进行持续上升,说明缩聚反应过程中,此应力作用促进焦油裂解生成的·H的数量大于缩聚反应消耗的·H的数量;同时,·H和H_(2)含量升高,促进·SH与·H结合,提高了H_(2)S的产率。

Taking Yima coal as the research object,the crystalline cell was constructed.In the ReaxFF force field,the 5×10^(9) s^(-1) strain rate was applied to simulate the pyrolysis product evolution of Yima coal at the final temperatures of 1000 K,1500 K,2000 K,2500 K,3000 K and to analyze the effect of single stress on lignite pyrolysis.The results show that the stress in different directions fluctuates up and down at different simulated final temperatures.The stress range remains between ±70 GPa with an allowable uncertainty,indicating that the effect of this stress on the pyrolysis of lignite is weakly affected by temperature.In the simulation process,there is a minimum point in the number of molecules and a maximum point in the number of species between 26 ps-33 ps.The simulated starting temperature point of Yima coal pyrolysis remains unchanged,but the temperature range of the polycondensation reaction moves forward.It indicates that the effect of single stress is better than that of temperature in the early stage of the reaction process,and stress promotes the overall reaction process.The contents of CO,CH_(4),H_(2)O and NH_(3) first increase and then decrease due to the effect of polycondensation,which conforms to the general pyrolysis law,indicating that the stress does not change the ultimate trend of the reaction.The quantities of H_(2) and·H continue to rise,which explains that the cracking quantities of·H in the tar by this stress is higher than that of·H consumed by the polycondensation reaction.At the same time,the elevated contents of·H and H_(2) promote the combination of·SH with·H,thereby increasing the yield of H_(2)S.