煤中微细粒黄铁矿的赋存化学与物理

Fine pyrite is the main carrier of not only sulfur, but also many hazardous elements, such as Hg, Pb, As and so on. Due to its micro particles and complicate relationship with coal matrix, it is difficult to describe its characteristics in coal and remove it during coal preparation. Besides, fine pyrite plays a leading role in the spontaneous combustion of coal and coal gangue as well as the acidification of mine drainage. This will bring about many environmental problems during the coal processing and utilization. Fine pyrite in coal will be studied by several means such as XPS, TEM, NMR, etc., combining with experimental means of extraction separation, which includes: (1) occurrence of the fine pyrite in coal including its crystal structure, the level of crystal growth, embedded mode and the relationship with the structure of organic macromolecular, etc., (2) physical characteristics of the fine pyrite such as its scale effect, density and surface properties, etc., (3) geochemical characteristics of oxidbillity and solubility of fine pyrite with organic matter and spontaneous combustion mechanism of coal gangue in the atmosphere, (4) physicochemical reaction between fine pyrite and organic matter. The results aim at providing the scientific basis on deeply de-ashing and desulfur of coal, and controlling the spontaneous combustion of coal gangue and pollution from coal.

煤中微细粒黄铁矿不仅是硫的主要载体，也是Hg、Pb、As等有害元素的寄主矿物，由于其颗粒尺度小并与煤本体形成复杂的结构关系，不仅难以表征研究，选煤过程中难以脱除，也对煤与煤矸石的自燃、矿井水的酸化起主导作用，因而在煤的加工利用过程造成极大的环境影响。本项目运用XPS、TEM、NMR等多种分析方法以及萃取分离等实验手段，以煤中微细粒黄铁矿为研究对象，研究：（1）煤中微细粒黄铁矿的晶面结构、发育程度、嵌布方式及其与有机大分子的结构关系等赋存特征；（2）微细粒黄铁矿的尺度效应、密度与表面性质等物理特征；（3）大气环境中有机质参与微细粒黄铁矿氧化溶解的地球化学特性以及煤矸石自燃的机理；（4）微细粒黄铁矿与煤有机质的物理化学作用。研究成果试图为抑制矸石山的自燃、煤炭的深度脱灰降硫以及煤源污染控制提供基础理论与科学依据。

项目基于贵州、云南、内蒙古高硫煤样的洗选、氧化、溶解等实验，以及XRD、TEM、SEM等分析技术，研究了煤中微细粒黄铁矿的物理赋存与化学作用。发表论文10篇，其中SCI 收录7篇，达到了预期的成果。（1）揭示了煤中微细粒黄铁矿的分布赋存特征。发现煤中微细粒黄铁矿赋存方式多样，这主要与成煤环境与成因有关，但一般情况下，很难见在煤中到发育良好晶体形貌的微细粒黄铁矿，这主要与煤有机质参与矿物的形成有关；（2）明确了微细粒黄铁矿的尺度效应。发现煤颗粒粒度400目（37µm）为浮选尺度效应临界点，小于此粒度浮选效果不理想；发现煤中5µm粒度以下的黄铁矿颗粒有较强的地球化学特性，煤中微细粒黄铁矿密度为3.35-3.89g/cm3；（3）揭示了煤中微细粒黄铁矿氧化溶解的地球化学特性以及煤矸石自燃的机理。发现同等条件下，煤系黄铁矿的氧化速率大于矿物黄铁矿，而且接菌（氧化亚铁硫杆菌）处理的煤中黄铁矿氧化速率远大于矿物黄铁矿。煤矸石中的煤有机质和黄铁矿有缓慢的氧化反应，并伴生相互催化作用，从而降低了煤的着火点，促进了氧化进程，引起煤的自燃。（4）探索了微细粒黄铁矿与煤有机质的物理化学作用。发现煤中黄铁矿硫与有机硫在合适的条件下可以相互转化，煤中黄铁矿颗粒越细小其地球化学活动性越强，小到一定程度（亚微米尺度以下）黄铁矿颗粒与煤有机本体间可能不是物理嵌入而是化学键合。研究成果为抑制矸石山的自燃以及控制煤源污染提供基础理论与科学依据，对发展深度脱灰降硫的煤炭洁净新工艺提供新的启示。