准东煤田大井矿区B_(1)煤中水溶态离子分布及赋存特征

Distribution and occurrence characteristics of water-soluble ions in B_(1) coal in Dajing mining area of Eastern Junggar coalfield

目前,对煤中碱/碱土金属的研究主要以单个元素的赋存状态和迁移行为为主,煤中多种水溶态离子组合模式、可能来源及其对煤利用的影响缺乏系统的研究。为此,采用溶滤实验的方法,系统测定大井矿区煤中水溶态离子的含量及其沿煤层埋深方向的变化,分析大井矿区煤中水溶态离子的分布及其在煤中的组合形式。采集准东煤田大井矿区煤层钻孔样品、顶板样品及地表土壤样品,以样品中水溶态离子为主要研究对象,通过煤质特征分析和溶滤实验,综合运用离子含量比值分析、Piper三线图等方法,研究了煤中水溶态离子的分布及赋存特征。结果表明:大井矿区煤中水溶态离子含量总体相对较高;水溶态Na^(+),Ca^(2+),Mg^(2+),SO^(2-)_(4)等离子在煤层顶部含量较高,随着煤层埋深的增加含量呈明显降低趋势,到一定层位后,其含量基本趋于稳定;煤中水溶态Cl-纵向分布比较均匀,在下部煤层中含量略低;HCO^(-)_(3)随煤层埋深增加在中下部煤层中含量略有升高,但不显著。上部煤层中水溶态离子组合以SO_(4)-Na·Ca型和SO_(4)·HCO_(3)-Na型为主,下部煤层中水溶态离子组合以HCO_(3)·SO_(4)-Na型为主,整个煤层呈现出随埋深增加煤中水溶态离子组合由SO_(4)-Na·Ca型转化为HCO_(3)·SO_(4)-Na型的特点。煤中水溶态离子可能来源于地表盐碱土,地表土在地表水淋滤及地下水作用下对煤中水溶态离子进行补给,补给过程中煤中水溶态离子含量受到吸附、离子交换、分解氧化等物理化学作用的影响,使得煤中水溶态离子在不同层位分布和赋存特征上具有较显著的差异。研究准东煤田大井矿区煤中水溶态离子进入煤中的地下水动力学模式,硫酸盐和碳酸盐等矿物形成的次序及其地球化学机理,以期科学全面认识高碱煤中水溶态离子的成因,进而促进高碱煤的清洁高效利用,是下一步的工作重点。

At present,most studies on alkali/alkaline-earth metals in coals focus on the occurrence and migration of individual elements.There is a lack of systematic research on the combination patterns of various water-soluble ions in coal,their possible sources,and their effects on coal utilization.Therefore,using the dissolution and filtration method,the content of water-soluble ions in coal from the Dajing mining area and their changes in the direction of coal seam burial depth were systematically measured and the distribution of water-soluble ions in coal from the Dajing mining area and their combination forms in coal were analyzed.The coal seam drilling samples,roof samples,and surface soil samples from the Dajing mining area in the East Junggar coalfield were also collected.Taking the water-soluble ions in the samples as the main research object,the distribution and occurrence characteristics of water-soluble ions in coal were studied through the coal quality analysis,the experiments of dissolution and filtration,ions ratio analysis and Piper trilinear diagram,etc.The results show that the content of water-soluble Na^(+),Ca^(2+),Mg^(2+),and SO^(2-)_(4) in coal from the Dajing mining area is generally relatively high.Moreover,the content of water-soluble ions,such as Na^(+),Ca^(2+),Mg^(2+),and SO^(2-)_(4) in coal is higher at the top of the coal seam and shows a significant decreasing trend with the increase of coal seam depth.After a certain depth,their content tends to stabilize.The vertical distribution of water-soluble Cl-is relatively uniform,with a slightly lower content in the lower coal seam.HCO^(-)_(3) slightly increases in the middle and lower coal seams with the increase of coal seam depth,but the increase is not significant.The combination of water-soluble ions in the upper coal seam are mainly SO_(4)-Na·Ca type and SO_(4)·HCO_(3)-Na type,while it is mainly the HCO_(3)·SO_(4)-Na type in the lower coal seam.At the same time,the entire coal seam shows the characteristics that the combination of water-soluble ions in coal changes from SO_(4)-Na·Ca type to HCO_(3)·SO_(4)-Na type with the increase of burial depth.The water-soluble ions in coal may come from the surface of saline-alkali soil.The surface soil replenishes the water-soluble ions in coal under the action of surface water leaching and groundwater.During the replenishment process,the content of water-soluble ions in coal is affected by physical and chemical actions such as adsorption,ion exchange,decomposition,and oxidation,making the distribution and occurrence characteristics of water-soluble ions in coal significantly different in different layers.The next step is to focus on the groundwater dynamics model of water-soluble ions entering the coal in the Dajing mining area of the East Junggar coalfield,the sequence of the formation of minerals such as sulfates and carbonates,and their geochemical mechanisms.This is in order to scientifically and comprehensively understand the genesis of water-soluble ions in high-alkali coal and to promote the clean and efficient utilization of high-alkali coal.