Dynamic Characteristics for Evolution Process of Semi-closed Coal Fire
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摘要:
为研究松散煤体自然发火过程中氧气及温度阶段性的演化规律，搭建了半封闭煤火演化实验系统，探究煤体从常温到燃点过程中氧气浓度及温度变化情况，建立松散煤体自燃蔓延过程自然吸氧强度模型，分析自燃过程中氧气分布特征和温度场水平与纵向阶段性移动特征. 结果表明：半封闭煤火演化实验系统能够较好地再现煤自燃“自然吸氧”过程，验证了自然吸氧效应为煤体自燃蔓延提供动力；煤体自然发火过程中，温度变化时间滞后于氧气浓度变化时间，其滞后时间差随煤层纵深变化的增加而增加；在水平方向上高温区域迁移趋势主要受煤体内部裂隙与孔隙分布的影响；自然吸氧强度与测点峰值温度随煤体纵深增加而降低，未发生自燃区域的下方氧气浓度大于其上层氧气浓度. 研究成果对开采、运输、储存状态下的松散煤体自然发火的防治提供理论基础.
Abstract:In order to study the evolution law of oxygen and temperature in the process of spontaneous combustion of loose coal, an experimental system for semi-closed coal fire evolution was built to explore the changes of oxygen concentration and temperature in the process of coal from normal temperature to ignition point, and to establish the natural oxygen absorption intensity model for the spontaneous combustion process of loose coal. The model analyzes the characteristics of oxygen distribution and the horizontal and longitudinal phase movement characteristics of the temperature field during the spontaneous combustion. The results show that the semi-closed coal fire evolution experimental system can better reproduce the natural oxygen absorption process in coal spontaneous combustion, which proves that the natural oxygen absorption effect contributes to the spontaneous combustion of coal mass. During the spontaneous combustion of coal mass, the temperature change time lags behind oxygen concentration change time, and the lag time difference increases with the coal seam depth. The migration trend in the high-temperature area in the horizontal direction is mainly affected by the distribution of cracks and pores at coal body. The natural oxygen absorption intensity and the peak temperature at measuring points decrease with the coal body depth growing, and the oxygen concentration in the lower area without spontaneous combustion is greater than that in the upper layer. The research results provide a theoretical basis for the prevention and control of spontaneous combustion of loose coal under mining, transportation and storage conditions.
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图 4 自然吸氧强度变化与时间关系曲线
Figure 4. Curves of natural absorption oxygen intensity versus time
图 6 纵向温度变化与时间关系
Figure 6. Relationship between longitudinal temperature change and time
表 2 煤质分析
Table 2. Coal quality analysis
% 工业分析 元素成分分析 Mad Aad Vad FCad C H O N S 4.4 14.0 33.5 48.0 78.8 4.7 14.2 1.3 0.8 
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表 3 不同氧化自燃阶段温度划分
Table 3. Temperature levels in oxidized spontaneous combustion
阶段 氧化自燃阶段 平均温度范围/℃ 第一阶段 缓慢氧化阶段 0～111.0 第二阶段 快速升温阶段 112.0～303.0 第三阶段 高温自燃阶段 304.0～604.0
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表 4 纵向测点到达各阶段的时间与温度
Table 4. Time and temperature of longitudinal measuring points at each phase
阶段 PTC1 PTC2 PTC3 PTC4 PTC5 时段/h 温度/℃ 时段/h 温度/℃ 时段/h 温度/℃ 时段/h 温度/℃ 时段/h 温度/℃ 第一阶段 0～4.5 121.0 0～12.0 132.0 0～14.0 120.0 0～19.5 115.0 0～32.5 121.0 第二阶段 4.5～6.5 316.0 12.0～13.5 314.0 14.0～16.0 308.0 19.5～21.0 301.0 23.5～48.0 302.0 第三阶段 6.5～23.0 602.0 13.5～24.0 598.0 16.0～48.0 577.0 21.0～43.0 492.0 48.0～73.0 476.0
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