关闭煤矿水—岩—气反应模拟研究

发布时间：2018-03-20 02:03

本文选题：关闭煤矿　切入点：水-岩-气相互作用　出处：《中国矿业大学》2017年硕士论文　论文类型：学位论文

【摘要】：含瓦斯煤矿关闭后矿井内仍残余CH_4、CO_2、N_2等气体,上述气体在矿井水-煤岩作用下有可能带来瓦斯突出与地下水污染问题。本文通过室内实验和数值模拟重点针对CO_2、N_2气体开展了关闭煤矿水-岩(煤)-气反应模拟研究,揭示了闭坑条件下水-岩-气三相反应过程中矿井水质演化与煤岩矿物相变化机理,主要成果如下:(1)我国关闭高瓦斯煤矿主要分布在黑龙江、山西、湖南、江西及四川、云贵、重庆等地;高瓦斯矿井水化学特征以酸性矿井水居多,矿化度及硫酸盐含量相对较高,水化学类型有HCO_3·SO~(4-)Na型水、HCO_3~-Na型水、SO_4~-Ca·Mg型水、Cl·SO_4~-Na型水、Cl·HCO_3~-Na型水、Cl·HCO_3·SO~(4-)Na型水及SO_4~-Ca·Mg型水,其中SO_4~-Ca·Mg型水分布较多。(2)关闭煤矿水-岩(煤)-气反应室内实验结果表明:随着反应时间的增加,以CO_2/N_2为气相的水-岩反应中,溶液的pH值逐渐升高,Eh与pH呈负相关逐渐降低,溶液中HCO_3~-、SO_4~(2-)、Ca~(2+)、Mg~(2+)、可溶性SiO_2的含量均呈现不同程度的增加,溶液中Fe的浓度逐渐下降,溶液的矿化度逐渐增加;在以CO_2为气相的水-煤反应中,溶液中Cr、As、Cd、Al、Fe、Pb等微量元素与TOC的含量逐渐增加,重金属与有机污染风险加剧;利用SEM、XRD、XRF等手段研究了三相反应过程中煤岩层主要矿物的溶解沉淀情况,高岭石、石英主要发生溶解反应,方解石在溶解的同时伴随着碳酸盐矿物的再生成,黄铁矿表面生成赤铁矿、菱铁矿、绿泥石等新矿物。(3)采用PHREEQC软件模拟了不同温度、压力、水化学条件对关闭煤矿水-岩-气三相反应平衡的影响,结果表明,随着温度的升高,溶液的pH值略有降低,CO_2的溶解度、HCO_3~-、Ca~(2+)的浓度逐渐降低,方解石的溶解效应最明显;随着CO_2分压增大,溶液的pH值逐渐降低,CO_2的溶解度、HCO_3~-、Ca~(2+)的浓度逐渐增大,方解石的溶解效应最明显,不同CH_4分压下溶液的水化学成分和地层矿物的溶解沉淀量基本没有变化;随着体系pH值的增大,CO_2的溶解度先上升后迅速下降,HCO_3~-的浓度逐渐升高,Ca~(2+)的浓度逐渐降低,方解石、高岭石的溶解量逐渐降低,石英的沉淀量逐渐减少并发生微量溶解;随着Fe~(3+)浓度的升高,溶液的pH值迅速降低,HCO_3~-的浓度逐渐降低,Ca~(2+)、Fe~(2+)、SO_4~(2-)的浓度逐渐升高,高岭石、方解石、黄铁矿的溶解量不断增大,石英的沉淀量逐渐增多;硫酸盐的加入提高了地层矿物的溶解量,其中方解石的溶解效应最明显。
[Abstract]:After the gas mine was closed, there was still a remnant of gas Ch _ 4 / CO _ 2C _ 2T _ 2 in the mine. The above mentioned gas may bring about gas outburst and groundwater pollution under the action of mine water and coal rock. This paper, through laboratory experiments and numerical simulation, has carried out a simulation study on the water-rock (coal gas) reaction of coal mine closing by focusing on CO _ 2H _ N _ 2 gas. The mechanism of mine water quality evolution and coal rock mineral facies change in the process of water-rock-gas three-phase reaction under closed pit condition is revealed. The main results are as follows: 1) the closed high gas coal mines in China are mainly distributed in Heilongjiang, Shanxi, Hunan, Jiangxi and Sichuan, Yungui. In Chongqing and other places, the chemical characteristics of high gas mine water are mainly acid mine water, the salinity and sulfate content are relatively high. The hydrochemical types include HCO_3 路SO~(4-)Na type water, HCO3, -Na type water, so 4- Ca-mg type water, Cl 路SO_4~-Na type water, Cl 路HCO_3 路SO~(4-)Na type water and SO_4~-Ca 路mg type water, The results of laboratory experiments on the water-rock reaction of coal mine with SO_4~-Ca 路mg type water distribution are more and more. The results show that with the increase of reaction time, the pH value of solution increases gradually and decreases negatively with pH in the water-rock reaction with CO_2/N_2 as gas phase. In the solution, the content of soluble SiO_2 increased in varying degrees, the concentration of Fe in the solution gradually decreased, and the salinity of the solution gradually increased. In the water-coal reaction with CO_2 as the gas phase, The contents of trace elements and TOC in the solution increased gradually, and the risk of heavy metal and organic pollution increased. The dissolution and precipitation of main minerals in coal strata during three-phase reaction were studied by means of SEMXRDX XRF, kaolinite, kaolinite, etc. Quartz mainly dissolves, calcite dissolves at the same time accompanied by carbonate mineral formation, pyrite surface forms hematite, siderite, chlorite and other new minerals. It uses PHREEQC software to simulate different temperatures and pressures. The effect of hydrochemical conditions on the three-phase equilibrium of water-rock-gas reaction in coal mine closure is studied. The results show that the pH value of solution decreases slightly with the increase of temperature, and the concentration of HCO _ 3H _ 2O _ (3) -cai _ (2) decreases gradually, and the dissolution effect of calcite is the most obvious. With the increase of the partial pressure of CO_2, the pH value of the solution decreases gradually the solubility of HCO _ 2 and the concentration of HCO _ 3H _ 2O _ (2) increases gradually. The dissolution effect of calcite is the most obvious. The hydrochemical composition of the solution and the amount of dissolved and precipitated minerals in the formation are basically unchanged under different partial pressures of CH_4. With the increase of pH value of the system, the solubility of COS-2 rises first, then decreases rapidly. The concentration of HCO3- increases gradually, the dissolution of calcite and kaolinite decreases gradually, the precipitation amount of quartz decreases and the micro-dissolution occurs. With the increase of Fe~(3) concentration, the pH value of the solution decreases rapidly and the concentration of HCO3- decreases gradually. The concentration of kaolinite, calcite and pyrite increases gradually, and the precipitation amount of quartz increases gradually, and the concentration of kaolinite, calcite and pyrite increases gradually. The addition of sulphate increased the dissolution of the formation minerals, and the dissolution effect of calcite was the most obvious.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD71

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