Effect of oxygen and particle size on the oxidation-pyrolysis competition during coal char reburning: A thermogravimetric kinetic study

IF 5.1 3区工程技术 Q2 ENERGY & FUELS

Thermal Science and Engineering Progress Pub Date : 2025-06-12 DOI:10.1016/j.tsep.2025.103747

Liyang Ma , Fei Wang , Lan Zhang , Haihui Xin , Deming Wang , Qiulin Ma

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引用次数: 0

Abstract

The parallel competitive mechanism involving oxidation-pyrolysis kinetics dominates in governing the combustion dynamics and propagation of coalfield fires through fluctuating oxygen concentration. This study proposed a four-lump reaction kinetic model for oxygen-lean coal char combustion involving 17 parameters to be optimized. The contributions of each sub-reaction to the kinetic rates and mass evolution during coal char oxygen-lean combustion was delineated and quantified based on resolving the thermogravimetric data. The influence of oxygen concentration and particle size on the kinetic reactivity within the oxidation-pyrolysis competitive mechanism was elucidated. The results indicated that the immediate oxidation of initial coal char active structure (R_β) consistently predominated across the entire oxygen-lean gradient, successively followed by coke oxidation (R_o), incompletely pyrolysis of initial coal char active structure (R_α) and condensation gasification reaction of semi-coke (R_p). As the oxygen concentration increased from 1 % to 13 %, the competitive coefficient χ decreased from 0.608 to 0.077, and the proportion of mass loss contributed by sub-reaction R_β rose from 42.32 % to 93.37 %. The ignition mechanism shifted from heterogeneous ignition to homogeneous ignition at a transitional oxygen concentration of 9 % oxygen, while the critical value for coal char to transition from slow smoldering to rapid combustion was determined as 3 %. The particle size gradient influenced the combustion reactivity of coal char with 306 μm serving as a critical threshold. This study offers critical insights into the kinetic mechanisms and advanced monitoring strategies essential for mitigating coalfield fire hazards, contributing to the development of more effective control and prevention methodologies.

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氧和粒度对煤焦再燃过程中氧化热解竞争的影响：热重动力学研究

含氧化热解动力学的平行竞争机制在控制煤田燃烧动力学和通过波动氧浓度传播的过程中起主导作用。本研究提出了含氧贫煤焦燃烧的四团反应动力学模型，涉及17个参数进行优化。在分析热重数据的基础上，对煤贫氧燃烧过程中各子反应对动力学速率和质量演化的贡献进行了描述和量化。在氧化热解竞争机制中，阐明了氧浓度和粒径对反应动力学的影响。结果表明：在整个贫氧梯度上，初始煤焦活性结构（Rβ）的直接氧化反应始终占主导地位，其次是焦炭氧化反应（Ro）、初始煤焦活性结构（Rα）的不完全热解反应和半焦的缩合气化反应（Rp）。当氧浓度从1%增加到13%时，竞争系数χ从0.608下降到0.077，亚反应Rβ贡献的质量损失比例从42.32%上升到93.37%。在氧气浓度为9%的过渡条件下，煤焦的燃烧机理由非均匀燃烧向均匀燃烧转变，由缓慢阴燃向快速燃烧过渡的临界值为3%。粒径梯度对煤焦燃烧反应性的影响以306 μm为临界值。这项研究为减少煤田火灾危险的动力学机制和先进的监测策略提供了重要的见解，有助于开发更有效的控制和预防方法。

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来源期刊

Thermal Science and Engineering Progress Chemical Engineering-Fluid Flow and Transfer Processes

CiteScore

7.20

自引率

10.40%

发文量

327

审稿时长

41 days

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