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不同类型接触变质煤大分子结构差异性研究

Study on macromolecular structure of different types of contact metamorphic coals

  • 摘要: 岩浆侵入煤层时发生接触变质作用,导致煤的显微组分、煤级、化学成分、物理化学结构、工艺性质发生改变。不同的构造−热条件下形成不同类型的接触变质产物。为从大分子结构尺度揭示不同类型接触变质煤的差异性及其控制因素,采用工业分析、元素分析、反射率测定、X射线衍射(XRD)和拉曼光谱(Raman)等测试方法,并结合地质背景分析,开展山西大同塔山矿区天然焦系列样品和湖南鲁塘矿区煤系石墨系列样品的对比研究。结果表明:小型浅成岩体沿断裂侵入煤层后,热作用时间短,热封闭性差,属于高温低压条件,接触变质带窄,发育天然焦−热变煤序列;该系列处于碳化作用阶段,煤大分子结构以化学变化为主,芳构化作用和环聚合作用占主导地位,表现为富碳、去氢、脱氧。侧链和官能团等活性部位缺陷减少,芳香结构单元增长并导致芳层面内缺陷增加,芳香层片并未有序排列。区域性挤压构造背景下侵入的岩株、岩基等酸性、中酸性深成岩体,热量充足,热封闭性好,为高温高压条件,接触变质带宽度可超过1 km,发育石墨−半石墨−无烟煤变质序列;煤系石墨系列的化学成分成熟度高且变化小,大分子结构以物理变化为主,主要发生拼叠作用和秩理化作用。非定向的芳香层片在力的作用下拼接叠合、旋转定向,缺陷不断减少,向三维有序的晶体结构转变。

     

    Abstract: Contact metamorphism occurs when magma intrudes into the coal seam, resulting in changes to the microfraction, grade, chemical composition, physico-chemical structure and process properties of the coal. Different types of contact metamorphic products are formed under different tectonic-thermal conditions. In order to reveal the variability of different types of contact metamorphic coals and their controlling factors from the macromolecular structure scale, a comparative study of natural coke series samples from the Tashan mine in Datong, Shanxi Province and coal-based graphite series samples from the Lutang mine in Hunan Province was carried out using industrial analysis, elemental analysis, reflectance determination, X-ray diffraction (XRD) and Raman spectroscopy (Raman) test methods, and combined with geological background analysis. The results show that the small shallow-formed rocks have a short thermal action time, poor thermal confinement conditions, belong to high temperature and low pressure condition, narrow contact metamorphic zone, and develop natural coke - thermal transformation coal sequence; the series is in the carbonation stage, and the coal macromolecular structure is dominated by chemical changes, with aromatization and ring condensation dominating. It shows carbon enrichment, dehydrogenation, deoxygenation, reduction of defects in the active sites such as side chains and functional groups, growth of aromatic structural units leading to an increase in defects within the aromatic level, and the aromatic lamellae are not ordered. The acidic and moderately acidic deep-formed rock bodies such as strains and bases intruded in a regional extrusive tectonic setting are well heated, thermally confined and under high temperature and pressure conditions, and the contact metamorphic width can exceed 1km, developing graphite-semi-graphite-anthracite metamorphic sequences; the chemical composition of the coal-based graphite series is highly mature and less variable, and the macromolecular structure is dominated by physical changes, mainly occurring as collagenesis and rank physicochemical interactions. The non-oriented aromatic lamellae are spliced and stacked and rotated and oriented by forces, with a continuous reduction of defects and a transition to a three-dimensional ordered crystal structure.

     

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