A novel method for the desulfurization of medium–high sulfur coking coal

The presence of sulfur affects the clean utilization of coking coal. Inorganic sulfur in coal, which exists mainly in the form of pyrite, inherently pollutes clean coal during flotation, while organic sulfur, on the other hand, can only be effectively removed by chemical means. Here, the combined methods of flotation and oxidation were adopted for desulfurization, and the desulfurization mechanisms were analyzed via XPS (X-ray photoelectron spectrometer), SEM (Scanning electron microscopy), MD (Molecular Dynamics), etc. Results showed that the removal of inorganic sulfur was preferred compared to the removal of organic sulfur. The sulfur and ash contents in coal were reduced from 2.55% and 46.16% to 1.33% and 13.41%, respectively, via flotation-oxidation (FO) method. During the oxidation-flotation (OF) method, however, Fe2O3 was observed to form on the surface of pyrite, while the content of oxygen-containing functional groups, adsorption capacity of water molecules and hydrophilicity were observed to increase. MD simulation was in agreement with experimental results, in which the diffusion coefficient of water molecules on the surface of oxidized coal was found to be lower than that of raw coal. As such, the oxidation process reduced the hydrophobicity of coal, resulting in a lower recovery of the products obtained via OF as compared to FO method.