微波辐射对煤体瓦斯解吸渗流特性影响及作用机理

The impact of exerted physical fields such as electric field, electromagnetic field and sound field on coal and gas system is widely concerned in gas disaster prediction and prevention in recent years. As a high-frequency electromagnetic wave, microwave can generate thermal effect and electromagnetic effect in coal body. Based on the impact of temperature and electromagnetic field on coal and gas system, microwave irradiation could accelerate desorption of gas and enhance penetrability of coal. In order to study the effects of microwave irradiation on coal and gas system and explore a new method on gas derivation under physical field, a physical experiment is designed in this study. A triaxial desorption and seepage equipment and a microwave generation system will be reassembled. Diffusion characters of microwave in the standard coal specimen will be analyzed. Desorption and seepage tests will be performed under three different conditions, which are conventional condition (without microwave irradiation), online microwave irradiation and modified microwave irradiation. Desorption flux, desorption rate, seepage flux and permeability rate obtained under the three different conditions will be compared and analyzed. Effects and mechanisms of microwave irradiation on coal gas desorption and seepage characters are expected to be clarified. The results have important theoretic and practical significance for microwave application in gas treatment, gas derivation from low permeability coal seam, gas disaster prevention and coal mine safety production.

电、磁、声等外加物理场对煤与瓦斯系统的影响是近年来瓦斯灾害预测与防治领域研究的热点。微波作为一种高频电磁波，作用于煤体能够产生热效应及电磁场效应，根据温度及电磁场对煤与瓦斯系统的影响特征，微波辐射极有可能促进瓦斯解吸、增大煤体渗透性。为深入探讨微波辐射对煤与瓦斯系统的影响，同时也为探索一种新的物理场激励瓦斯的方法，本项目采用室内物理实验方法，设计、改装微波辐射作用下三轴解吸渗流实验平台，研究微波在成型煤样中的传播特征，开展常规（无微波辐射）、微波在线辐射及微波电磁改性后三种条件下煤样瓦斯解吸及渗流实验，对比分析三种条件下煤样瓦斯解吸量、解吸速度以及渗流量、渗透率，揭示微波辐射对煤样瓦斯解吸及渗流特征的影响规律及作用机理。研究成果对于促进微波技术在瓦斯治理方面的应用、提高低透气性煤层瓦斯抽放效率、防治瓦斯灾害、确保矿井安全生产具有重要的理论与现实意义。

渗透率低、解吸速度慢是目前制约我国瓦斯抽采的主要因素。为提高瓦斯抽采效率，近年来，国内外学者开始关注电、磁、声等外加物理场对煤与瓦斯系统的影响以期找到用于瓦斯灾害防治的新方法。微波作为一种高频电磁波，作用于煤体能够产生热效应及电磁场效应，根据温度及电磁场对煤与瓦斯系统的影响特征，微波辐射极有可能促进瓦斯解吸、增大煤体渗透性。为深入探讨微波辐射对煤与瓦斯系统的影响，同时也为探索一种新的物理场激励瓦斯的方法，本文对微波作用下煤中瓦斯解吸响应特征及机理进行了研究。设计改装了微波辐射作用下煤中瓦斯解吸实验装置，根据微波功率的不同，实验方案采用微波间断加载和微波连续加载两种方式。开展了微波间断加载作用下煤中瓦斯解吸实验，结果表明，微波间断加载作用下瓦斯累积解吸量比无微波作用条件下瓦斯累积解吸量增加了0.9～2.9倍，表明微波间断加载作用对煤中瓦斯解吸具有明显的促进作用。微波辐射对煤中瓦斯解吸的瞬间提速作用效果十分显著，800W功率微波加载40s能将解吸速度提升至加载前的11.2倍。分别开展了微波间断加载与等效升温条件下煤中瓦斯解吸对比实验及微波连续加载与最高温度条件下煤中瓦斯解吸对比实验，结果表明微波作用和纯升温作用均能增大瓦斯解吸量，促进瓦斯解吸，且微波辐射对煤中瓦斯解吸的促进作用要优于纯温度作用。应用经典扩散模型与动扩散系数模型分别对微波间断加载作用与连续加载作用下煤中甲烷解吸动力学规律进行了分析，表明微波作用能够显著提高甲烷扩散系数，微波作用能量越大，扩散能力增加越多。微波作用对煤中瓦斯解吸特性影响及其作用机理表现为微波热效应、煤的损伤效应及微波作用对煤的孔隙结构影响的综合作用。研究成果可为微波辐射法的工艺设备研发及强化瓦斯抽采方案的设计提供理论依据，对于低渗煤层强化瓦斯抽采、瓦斯灾害防治具有重要的理论与现实意义。