Abstract

By thermogravimetry (TG) experiments, evolution behaviors and properties of thermal oxidation processes at low temperature (< 230.0 °C) of a bituminous coal with five moisture contents were investigated. A novel Acceleration Temperature Point Method (ATPM), defined as the transition point from low-temperature oxidation to rapid self-sustained heating-up period, was proposed to determine the role of moisture content in accelerating such process. Results show that segments of water evaporation and gas desorption dominate in stage 1 (65.0–150.0 °C), while segments of generation of coal-oxygen complex and structure oxidation dominate in stage 2 (150.0–275.0 °C). In the moisture range of 9.16–12.06%, the promoted effect of physical desorption capacity becomes weak with increasing moisture content. This is owing to five aspects: the equilibrium of vapor pressure and wetting capability of physically bound water, the change of mass and heat transfer between gas phase (water vapor)-condensed phase (bulk coal particle), the diffusing effect of gaseous water, the heat from dissolving and swelling of gaseous water into bulk coal pores, and the heat of pyrolysis derived from coal particles. Taking Acceleration Temperature Point (ATP) as a barometer to evaluate the spontaneous combustion susceptibility, the critical moisture content of Gengcun bituminous coal is 9.16%.

摘要

通过热重（TG）实验，研究了五种含水率烟煤低温（< 230.0 ℃）热氧化过程的演化行为和性质。提出了一种新的加速温度点法 (ATPM)，定义为从低温氧化到快速自持升温期的过渡点，以确定水分含量在加速这一过程中的作用。结果表明，第一阶段（65.0-150.0℃）以水蒸发和气体解吸为主，而第二阶段（150.0-275.0℃）以煤氧复合物生成和结构氧化为主。在9.16-12.06%的水分范围内，随着水分含量的增加，物理解吸能力的促进作用变弱。这得益于五个方面：物理结合水的蒸气压和润湿能力的平衡，气相（水蒸气）-凝相（散装煤颗粒）之间的传质和传热变化，气态水的扩散作用，溶解和膨胀产生的热量气态水进入散装煤孔隙，煤颗粒产生的热解热。以加速温度点(ATP)为晴雨表评价自燃敏感性，更村烟煤的临界含水率为9.16%。以及来自煤颗粒的热解热。以加速温度点(ATP)为晴雨表评价自燃敏感性，更村烟煤的临界含水率为9.16%。以及来自煤颗粒的热解热。以加速温度点(ATP)为晴雨表评价自燃敏感性，更村烟煤的临界含水率为9.16%。