煤中微细粒矿物的赋存与演化特征

During coal beneficiation, as an important inorganic component of coal, fine-grained mineral is difficult to describe and separate, due to its small particle size and complicate interaction with coal matrix. Moreover, fine-grained mineral makes great contributions to fine particulate matter during coal combustion. The work aims to accommodate the significant demand for the prevention and control of atmospheric pollution in China. The mode of occurrence of fine-grained mineral in coal and its evolution during coal utilization will be studied by several analysis methods such as XPS, FE-SEM, CT, FIB-SEM, etc., combining with combustion experiments and manual coalification experiments, which includes: (1) geological genesis and occurrence of fine-grained mineral in coal including its constitution, crystal structure, degree of development, disseminated mode, etc.; (2) the physical and chemical properties of fine-grained mineral and its structural relationship with coal organic matrix; (3) the microscale effect of fine-grained mineral and its response during coal beneficiation; (4) the ash formation mechanism of fine-grained mineral and its relationship with the atmospheric fine particulate matter during coal combustion. The research results will provide the scientific basis on the high-efficiency and clean utilization of coal resources, coal-related atmospheric pollution reduction and atmospheric quality improvement.

煤中微细粒矿物是煤重要的无机组分，由于其颗粒尺度小并与煤有机本体形成复杂的结构关系，不仅难以表征，选煤过程中难以脱除，也对燃煤细颗粒物的生成贡献巨大。本项目面向我国大气环境污染防治的重大需求，拟运用XPS、FE-SEM、CT、FIB-SEM等多种分析方法以及人工煤化实验、燃烧实验等手段，研究微细粒矿物在煤中的赋存以及在煤利用过程中演化特征：（1）煤中微细粒矿物的组成、晶面结构、发育程度、嵌布方式等赋存特征以及地质成因；（2）煤中微细粒矿物的物理化学特性及其与煤有机本体的结构关系；（3）煤中微细粒矿物的微尺度效应及其在选煤过程中的响应规律；（4）煤中微细粒矿物的成灰机理及其与燃煤大气细颗粒物的成因联系。研究成果试图为煤炭资源的高效洁净利用、燃煤大气细颗粒的减排与空气质量改善提供科学依据。

项目基于贵州、山西、云南、内蒙古不同煤级煤的洗选、低温灰化、热解等实验，并使用XPS、FE-SEM、CT、FIB-SEM等多种分析方法，研究了微细粒矿物在煤中的赋存以及在煤利用过程中演化特征，发表论文8篇，其中SCI收录6篇，达到了预期成果:（1）揭示煤中微细粒矿物的赋存特征与地质成因。发现粒度<50μm的微细矿物占矿物总体的体积一般小于10%，在煤中分布比较均匀，且煤中普遍存在微球粒矿物（＜5μm），多为胶体成因，主要是作为高岭石前驱物的水铝石英，其脱水后最终会形成难选的浸染黏土矿物；（2）明确微细粒矿物的物理化学特性及其与煤有机本体的结构关系。发现的煤（特别是低煤级煤）中有机矿物的存在（草酸钙、腐殖酸钠等）是矿物与有机质间存在物理化学作用的直接证据，随着煤化作用增强，煤中有机矿物显著减少；煤源高岭石中有机质的含量高于非煤源的矿系高岭石，而且有机质含量越高高岭石的结晶度越好，故煤源高岭石的结晶度高于矿系高岭石；煤中微细粒黄铁矿表面含有更多的有机官能团，在一定的条件下黄铁矿硫与有机硫可以相互转化；（3）揭示了微细粒矿物在煤炭分选过程中的分配规律。发现煤中难选矿物主要为浸染状黏土矿物（主要是高岭石）与微细粒矿物（主要是黄铁矿），38μm为浮选尺度效应临界点，小于此粒度黏土矿物受泥化作用影响较大，精煤灰分增加；（4）揭示煤中微细粒矿物的成灰机理及其与燃煤细颗粒的成因联系。发现燃煤产生的粉煤灰富铝贫硅且有较高的K2O含量，其颗粒分布在0.5-300μm之间，平均粒径在20μm左右，不同粒度级的粉煤灰有着相似的物相组成；除了煤中成灰矿物外，参与煤中有机质结构的无机组分以及嵌布于煤基质中的内在矿物（多是亚微米、纳米硅铝酸盐矿物）同样能在煤燃烧过程中产生约4%的灰分。研究成果为燃煤大气细颗粒的减排与空气质量改善提供科学依据，对发展煤炭资源的高效洁净利用的新工艺提供新的启示。