煤升温氧化动力学阶段性规律

1.西安科技大学 安全科学与工程学院,陕西 西安 710054; 2.教育部 西部矿井开采及灾害防治重点实验室,陕西 西安 710054

煤自燃; 热分析实验; 分段性; 活化能; 补偿效应

Kinetics and segmentation law of coal oxidation at elevated temperature
ZHANG Xin-hai1,2,BAI Ya-e1,2,LI Ya-qing1,2,MA Teng1,2

(1.College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China; 2.Key Laboratory of Western Mine Exploration and Hazard Prevention,Ministry of Education,Xi'an 710054,China)

coal spontaneous combustion; thermogravimetric analysis experiments; divided segments; activation energy; kinetic compensation effect

DOI: 10.13800/j.cnki.xakjdxxb.2017.0404

备注

为了研究煤的自燃特性,选取石圪台煤矿22203采煤工作面煤样为研究对象,采用热分析技术,对煤氧化升温过程中质量及动力学参数变化规律进行了探讨。结果 表明:煤的失重呈阶段性变化规律,可分为低温失重、吸氧增重、缓慢化学反应和燃烧阶段; 通过采用改进的KAS法计算煤升温氧化动力学参数,可知在温度达到燃点前,随着温度升高反应活化能增加,说明不断有难燃结构参与到反应。超过燃点温度,在燃烧阶段初期,活化能基本保持不变,而指前因子出现峰值,表明有大量活性结构被激活,准备参与到燃烧反应中。在燃烧阶段中后期,活化能随温度的增加逐步减小,表明该阶段有芳香环的破坏形成更易于反应的活性结构; 动力学参数的补偿效应存在显著分段性,说明在煤氧反应过程中前后反应不同,其整体反应存在不止一个反应机理。研究结果对防治煤自燃提供理论依据。

In order to research on spontaneous combustion of coal,thermogravimetric analysis is employed to study laws of mass loss of coal sample from Shigetai coal mine 22203 working face.During oxidation at elevated temperature,kinetics of the process is studied.The results showed that lows of sample mass loss and kinetics remarkably among different temperature segments.Accordingly,the reaction process of coal in air at elevated temperature is divided into 4 segments:low temperature heat loss,oxygen adsorption weight gaining,low rate chemical reaction and combustion.The modified KAS method is employed to calculate activation energy of coal.It can been known from the results that the activation energy increases as temperature rises to combustion point,indicate that more and more less reactive structures of coal involves in the reaction.When temperature crosses the combustion point,at the beginning of combustion the activation energy keeps almost constant while the pre-exponential factor have a peak.It indicate that more and more reactive structures were appeared to prepare for the combusion reaction.As temperature continues to rise,the activation energy decreases slowly.The main reason is that the aromatic core of the coal may break down to produce large amount of reactive structures.The kinetic compensation effect has a significant segments,indicating that the Shigetai coal's combustion mechanisms are different in the ealy stage and in the later stage during its burning,and there are more than one mechanism through the whole reaction.The results provide a theoretical basis for the prevention and control of coal spontaneous combustion.