Study on the separation of lithotypes and their properties: A case study in the Permian period coal of the Dahebian coal mine, Liupanshui coalfield, China

The basic research on the separation method and characteristic properties of different coal lithotypes is of great significance for coal precision utilization. Based on the separation process of coal lithotypes and the characterization of the physical and chemical properties of the separation products, this paper aims to explore the relationship between the selection of lithotypes differential separation methods and their own physical and chemical properties. Firstly, a combined process of manual picking, density liquid centrifugation and shaking table separation was used to separate and purify fusain, vitrain and durain. Then, the properties of high purity single lithotype (fusain: 88.95%, vitrain: 91.74%, and durain: 85.33%) are analyzed to micromorphology analysis, surface properties, thermal stability analysis, elemental composition and functional group analysis. The product characterization results showed that the difference some physical and chemical properties, thermogravimetric parameters, surface finish and flatness, surface wettability, elemental content (C, O, S), degree of aromatization, and oxygen-containing functional, are obviously different and have certain internal correlation for different coal lithotypes. Comprehensive comparative analysis demonstrated that several parameters (the degree of surface finish and aromatization, as well as the content of oxygen-containing functional groups) have significant positive effects on wettability of coal lithotypes. These properties determine that the separation methods of different lithotypes should be different. Besides, we also verify the above conclusion through the combined separation process experiment of centrifugation, flotation and shaking table.