协同时间效应的煤低温氧化表观动力学模型研究

Low temperature coal oxidation is the most critical stage within the process from self-heating to self-ignition of coal. Low temperature coal oxidation kinetics is an important theoretical basis and technical method to investigate the complex thermal process which contains various chemical reaction sequence and multiple physical fields. Previous studies mainly employed Arrhenius kinetic model to study the correlation between oxidation rate and reaction temperature. However, a growing number of studies have shown that the simple Arrhenius kinetic model was unable to rigorously describe the complex dynamic process and to scientifically explain the reason for the differences between coal low temperature oxidation experimental results. Based on the status quo, the project follows such a research path as theory promotion, experimental justification and applicability extension. The purpose of the project is to establish a revised apparent kinetic model of low temperature coal oxidation considering time effect intrigued by the oxygen adsorption sequence and to validate the model by the combination of experiment and numerical simulation; to grasp the differences and causes of low temperature oxidation apparent kinetic models under different governing regimes by properly adjusting the testing conditions; to expand the applicability of the new model and to reveal the crossing application scope of the new and old kinetic models by proposing the concept and calculation method of the effectiveness factor between different governing regimes. It is expected that the research results can reveal deeper characteristics of low temperature oxidation of coal and have certain practical significance to the development of coal spontaneous combustion theory.

煤低温氧化阶段是煤自热发展到自燃的一个最重要的阶段，低温氧化动力学是研究这个兼具多类型化学反应序列过程的一个重要理论基础。以往的研究主要利用Arrhenius动力学模型来表征煤氧反应速率与反应温度的关系，而越来越多的研究表明采用单一的Arrhenius动力学模型无法严谨地描述这个复杂的动力过程，也无法科学解释煤低温氧化实验结果差异性的原因。本项目立足于这个现状，通过理论延伸、实验及数值模拟验证和适用性选配的总体研究技术路线，揭示煤氧低温反应吸附序列所激发的的时间效应的显现规律；建立协同时间效应的煤低温氧化表观动力学模型并采用实验和数值模拟有机结合的研究思路完成模型验证；掌握煤低温氧化动力主控模式的切换规律；提出不同主控动力模式间效果因子的数学概念和计算方法，甄别新旧动力学模型间的交叉适用范围。预计研究成果对煤自燃动力学理论的发展有一定的现实意义。

项目完成了绝热氧化实验平台的设计和搭建，开展了不同变质程度不同粒径的绝热氧化实验，回归分析了不同变质程度和不同粒径煤的表观动力学参数，并得出以下主要结论：随着变质程度的增加，升温速率降低，煤的指前因子和活化能均随着煤化程度的增加而增大；粒径的降低会加快煤的氧化速率，煤的表观活化能随着粒径的减小而减小，褐煤和不粘煤的指前因子也随着粒径的减小而减小，将煤颗粒简化为无内孔球形颗粒后由理论分析和实验研究证明煤粒径的倒数与其表观活化能呈线性关系；在煤绝热氧化的初始阶段（＜70℃）和高温阶段（＞150℃）出现了非Arrhenius现象，通过分析得出煤与氧的物理脱附吸附是初始阶段前半段（＜50℃）的非Arrhenius现象的主要原因，化学吸附则主要影响初始阶段的后半段（50~70℃）；在高温阶段氧化产物的增多对氧气扩散的限制则是该阶段产生非Arrhenius现象的主要原因；得出褐煤、不粘煤和无烟煤不同粒径的临界温度点，并且低变质程度褐煤的临界温度对粒径的变化较为敏感，其次是不粘煤，这两种煤的临界温度随粒径的变小而降低，高变质程度无烟煤的临界温度也出现了降低但是并不明显。项目揭示了煤氧低温反应的时间效应作用机制和显现规律；建立了协同吸附序列所激发的时间效应的煤低温氧化表观动力模型；掌握了不同主控动力模式的切换规律以及表观动力模型的差异性现象及成因；提出不同主控动力模式间效果因子的概念和计算方法。研究成果对煤自燃动力学理论的发展有一定的现实意义和应用前景。