【作者】 杨宏民；

【导师】 张铁岗；

【作者基本信息】 河南理工大学 ， 安全技术及工程， 2010， 博士

【摘要】 受煤层注气提高煤层气产出率(ECBM)试验成功的启发,首次成功地将煤层注气驱替技术用于煤矿井下注气促排促抽煤层瓦斯的工程技术领域。论文围绕煤对N2、CO2、CH4以及他们的混合气体吸附-解吸规律、气体之间的竞争吸附和置换吸附规律展开实验室研究。基于达西(Darcy)渗流理论、菲克(Fick)扩散理论、扩展Langmuir吸附理论以及气体状态方程,建立了多物理场耦合条件下的气体流动和置换解吸模型,利用Comsol Multiphysics有限元数值模拟软件进行了煤层注气数值模拟。在此基础之上,在煤矿井下开展了注气置换解吸煤层甲烷的工艺技术研究,考察了掘进面迎头边注边排和边注边抽、巷帮耳状钻场边注边抽、巷帮顺层孔边注边排和边注边抽等多种井下工艺的注气置换效果,提出了注气驱替/置换煤层甲烷的气体置换、气流“携载”、气流稀释扩散和气流膨胀增透的作用机理。首先研制了专用的大煤样量多元气体吸附装置,采用气样储罐隔离采样法解决了采样过程中气相组分不断变化的难题。建立了煤对混合气体的竞争吸附和置换吸附实验方法。试验结果表明,煤对CO2、CH4和N2吸附常数a值分别为63.6943 m3/t、41.1523 m3/t和16.5837 m3/t,说明煤对这三种气体吸附能力由大到小的顺序为CO2、CH4、N2;竞争吸附和置换吸附显示出相同的吸附规律,表明煤对气体的吸附与各种气体吸附的先后顺序无关,仅与吸附始末状态及浓度比例有关。煤层注气驱替/置换过程是一个渗流、扩散、置换吸附-解吸多场耦合条件下的含有质量交换的运动过程。基于达西定律、菲克定律和Langmuir多元气体吸附方程,建立了多物理场耦合数学模型,进行了煤层注气数值模拟。结果表明,在自然排放条件下,注气能使钻孔纯甲烷流量大幅度增加,其中注N2增加幅度为29.5倍,注CO2的增加幅度为37.54倍。配合抽放措施后,注N2增加幅度在排放+注气的基础之上又提高了8.34倍,注CO2提高了10.10倍。在煤矿井下分别对掘进工作面迎头、巷帮钻场和巷帮煤壁进行了注气促排和注气促抽现场试验。试验结果表明,试验煤层注气有效半径为1.2m-2.0m,且受注气压力和注气流量的影响较大。现场实测掘进面迎头注气+排放条件下,注气后的钻孔纯甲烷流量较注气前增加了31.56~140.93倍。抽放+注气条件下,纯甲烷抽放流量比单抽措施的抽放流量增加了1.63~2.06倍。经现场考察,在抽放量相同时,单抽措施需要抽放19天,配以注气措施后仅需9.2~11.6天。巷帮顺层钻孔高压注气的纯瓦斯流量增加了4.54~24.57倍。利用钢瓶向煤层注入纯N2或纯CO2时,从煤层瓦斯含量的变化和煤层气成分的变化上来看,比注空气的效果好。但是从煤层宏观上看,由于其注气量和注气时间有限,整体置换效果不如空气。井下注气驱替/置换煤层甲烷的机理主要有:注入气体的置换吸附-解吸作用、注气气流的载携作用、注气气流的稀释扩散作用和注气气流的膨胀增透作用。其中注入气体对甲烷的“携载”、“驱赶”作用占主导地位,而气体之间的“竞争吸附”和“置换吸附”起次要的作用。更多还原

【Abstract】 Inspired by the successful test of Enhanced Coal Bed Methane (ECBM) by means of gas injection, the gas injection technology was firstly applied to accelerate coal seam methane emission and drainage in underground coal mine. The adsorption– desorption laws of N2, CO2, CH4 and their mixture on coal have been researched; and a series of lab experiment of displacement adsorption and competition adsorption have be made. Before underground testing, based on Darcy’s law, Fick’s law and Langmuir’s law, a set of numerical models were established under multi-physics field coupling conditions, and coal seam gas injection was simulated make use of The Comsol Multiphysics software. On this basis, a set of technical study about injection gas in coal seam to displace coal methane underground has been made, and the displacement effect of“gas-injection as methane releasing”and“gas-injection as drainage”in roadway head, road wall drill shack and roadside hole alone coal seam has been researched. Finally, the mechanism of displace methane by gas injection has been proposed.A special experimental equipment for big quantity coal saples adsorption and desorption to multicomponent gas has been developed, and the problem, which the gas phase component change continually in the sampling process has been solved by separate sampling method used a gas sample storage vessel. Based on the equipment, two experimental methods of competition adsorption on multicomponent gas mixture and displacement adsorption for gases displacing methane in coal has been established. The results show that the adsorption constant a values of coal sample to CO2, CH4 and N2 weae 63.6943 m3/t, 41.1523 m3/t and 16.5837 m3/t, the absorbability descending sequence of the three gas is CO2, CH4 and N2. Two experiments showed the seam laws between displacement adsorption and competition adsorption. It indicated that the gases adsorption has nothing to do with the order of adsorption of every component, it only relates to start and end condition of adsorption and component of mixture.Displacement and replacement of coal seam gas incection is a complex movement with mass exchange under the multi-physics field coupling conditions of permeation, diffusion, and displacement adsorptiom-desorptiom. Based on Darcy’s law, Fick’s law and multicomponent gas Langmuir’s law, a series of multi-physics field coupling mathematical model has been established, the gas injection numerical simulation has been made. The results were indicated that methane flow quality in bore hole made a significant increase after gas injection, which the increase multiple of N2 injection is 29.5 times, and that of CO2 injection is 37.54 times. With the gas drainage, the increase multiple of N2 injection is 8.34 times, and that of CO2 injection is 10.10 times.The two testing of gas injection-nature emission and gas injection-drainage has been made in head-on of coal drift face, coal roadside wall and drill shack. The site test result indicated that the effective influence radius of gas injection is 1.2m to 2.0m for the testing coal seam, and the radius was influenced greatly by pressure and flow of gas injection. With compared to nature methane emission, the pure methane flow quality of bore hole is increase to 31.56~140.93 times under air injection and nature emission in tunneling face head-on. Correspondingly, the methane flow quality is increase to 1.63~2.06 times under air injection and drainage. With the same drainage methane quality,the drainage time of drainage only is 19 days, that of air injection and drainage only need 9.2~11.6 days. The pure methane flow quality is increase 4.54~24.57 times on the condition of air injection and drainage in roadside hole alone coal seam. When injected pure N2 and CO2 into coalbed use high-pressure cylinders, the methane emission effect of pure gas injection is better than that of air injection as viewed from methane quality of coal sample. But from the macro point of view, pure gas injection effect is no better than that of air injection because of the limit of quality and period of injection.The mechanism of gas injection to accelerating methane emission and drainage are the action of displacement adsorption of injection gas, the action of carrying of injection gas to coal seam methane, the action of dilution and diffuse, and the action of expansion and increased permeability. The action of carry and drive of injection gas is main role, and the action of competition and replacement adsorption is played secondary role.更多还原