煤样浸水过程中水化学效应研究

Hydrochemistry of Coal Samples in Water Immersion Process

为研究地下煤层开采中,水化学作用对预留安全煤柱的化学影响,对取自大柳塔5-2煤样进行完全静态浸泡试验,浸泡时长以溶液pH波动变化幅度而定,通过对浸泡煤样溶液的pH及氧化还原电位值动态变化监测,分析盐水溶液pH及氧化还原电位与煤样水化学过程的对应关系,并结合非平衡态热力学理论判定,解释煤样水化学作用的根本原因;结果表明:煤样浸水初期溶液pH(0~4 h)降低,煤岩矿物及有机碳氧化反应产生大量酸性水,随浸泡时间的增加,煤岩长石类矿物及方解石、白云石等消耗大量的H+,生成稳定的黏土矿物,同时长石类矿物溶解的阳离子与黏土矿物裸露表面产生离子反应,引起pH总体上升;结合非平衡态热力学理论,浸水煤样与外部环境的存在温差、水岩之间相互作用及渗流力的产生等,加快熵产生率,因此煤样浸水水化学效应所导致溶液pH及氧化还原电位值变化均属于煤样化学风化自发体系。

In order to study the chemical weathering process of the reserved safe coal column in underground coal seam mining,a complete static immersion experiment was carried out on coal samples taken from Daliu Tower 5-2,and the duration of immersion was determined by the fluctuation of the pH value of the solution.The non-equilibrium state thermodynamic theory was used to explain the root cause of chemical weathering of coal samples.The results show that the solution pH(0~4 h)at the initial stage of coal sample immersion decreases,which is due to the oxidation reaction of coal rock minerals and organic carbon to produce a large amount of acidic water.With the increase of immersion time coal rock feldspar minerals,calcite,dolomite.consume a large amount of H+,generate stable clay minerals.At the same time,feldspar minerals dissolved cations and clay.Combined with the non-equilibrium thermodynamic theory,the existence of temperature difference between the weathered rocks and external environment,the interaction between water rocks and the generation of percolation force accelerate the entropy generation rate,therefore,the changes in solution pH and redox potential caused by the weathering of coal samples in water belong to the spontaneous system of coal sample weathering.