Influence factors of coal surface wettability

In order to study the influence mechanism of coal surface wettability, 16 kinds of coals with different metamorphic degrees were characterized by the measurement of contact angle.Metamorphic of coal (rank), chemical composition, oxygen containing functional groups, the fractal dimension of coal, and the specific surface area were studied by means of virtrinite reflectance determination, industry analysis, elemental analysis, infrared spectrum experiment, and the determination of laser granulometer.The least square method and the contact angle were used to establish the linear fitting.The results verify that coal surface wettability mainly depends on oxygen content, moisture, ash and the content of functional groups.The hydrophilic functional groups mainly include the 910-940 cm^-1 hydroxyl deformation and the 3 400-3 450 cm^-1 aromatic hydroxyl extension, carbonyl and carboxyl groups were not obvious in the samples.At the same time, along with the increase of coal rank, carbon content and fixed carbon, the contact angle increase and the wetting property becomes worse.Fractal dimension is used to characterize particle size distribution, with the coal particle size D₁₀, D₅₀, and D₉₀ becoming smaller, the fractal dimension increases, the contact angle becomes larger, and the wetting property becomes worse.