The structure and distribution of organic sulfur in coals of different rank and different sulfur content were studied by combining mild organic solvent extraction with XPS technology. The XPS results have shown that the distribution of organic sulfur in coal is related to the degree of metamorphism of coal. Namely, thiophenic sulfur content is reduced with decreasing metamorphic degree; sulfonic acid content rises with decreasing metamorphic degree; the contents of sulfate sulfur, sulfoxide and sulfone are rarely related with metamorphic degree. The solvent extraction and GC/MS test results have also shown that the composition and structure of free and soluble organic sulfur small molecules in coal is closely related to the metamorphic degree of coal. The free organic sulfur small molecules in coal of low metamorphic degree are mainly composed of aliphatic sulfides, while those in coal of medium and high metamorphic degree are mainly composed of thiophenes. Besides, the degree of aromatization of organic sulfur small molecules rises with increasing degree of coalification.

Coal seam water injection is widely used to prevent rockbursts in coal mines, and the duration of water injection is an important parameter related to the effectiveness of rockburst prevention, making it of practical importance to optimize the effective water injection duration. This paper presents the test results of the mechanical properties and pore structure of samples with different soaking time, obtained from a working face where rockburst occurred. Soaking time changes the mechanical properties of samples, and this time effect differs with the coal size (from centimeter to nanometer size). Results of numerical simulation and on-site tests in the Changgouyu coal mine demonstrated that water injection can effectively soften coal bodies and release or transfer stresses, and the time effect of water injection on rock prevention and control is apparent.

Coal spontaneous combustion (the term is hereafter abbreviated as CSC) is an important problem facing by China to achieve carbon peak and carbon neutrality. CSC affects the mining process of mining for a long time, not only causing a large amount of waste of coal resources, but also severely destroying the ecological environment. At present, filling & plugging materials (the term is hereafter abbreviated as F&P materials) is widely welcomed and developed rapidly because of its advantages of wide application, obvious performance and low price. Based on the research of the prevention and control of CSC and the materials applying for it, this paper creatively puts forward an application system of materials used for the prevention and control of CSC. The types of F&P materials are systematically summarized. According to the form of materials, the F&P materials are divided into slurry, colloid and foam. The performance and effect of three kinds of F&P materials are analyzed in detail. On this basis, the cost and environmental protection characteristics of F&P materials in China were compared and evaluated. Finally, this paper predicts the development of F&P materials. This paper provides an effective reference for Chinese coal mining enterprises to select suitable F&P materials, which is of great significance for the prevention and control of CSC and environmental protection.