Enrichment Characteristics of Macerals during Triboelectrostatic Separation in the View of Surface Microstructure, Pore distribution, and Typical Electrical Parameters

[Image: see text] Vitrinite and inertinite, respectively, are the reactive and inert macerals for coal liquefaction, which could be effectively enriched in triboelectrostatic separation specialized in particle processing. Inertinite has a higher specific surface area and more pores than vitrinite and a more balanced mesopores distribution, while the mesopores in vitrinite are mainly focused in the 4 nm × 7 nm range. As for electrical properties, inertinite has a higher relative dielectric constant than vitrinite in all granularities, while its resistivity is only higher than vitrinite in the <74 μm fraction, which means inertinite and vitrinite tend to have negative and positive charges, respectively, in their mutual friction, but inertinite (<74 μm) has a stronger ability to maintain surface charge. During triboelectrostatic separation, the 105 μm × 150 μm fraction of clean coal has the highest vitrinite content, whereas inertinite tends to concentrate at tailings <74 μm under the co-effect of separation granularity limit and electrical characteristics of macerals; this conclusion has a certain guiding significance to maceral separation.