Micromechanism of coal dust wettability and its effect on the selection and development of dust suppressants

Abstract This article investigated quantitative data of carbon- and oxygen-containing groups of lignites, gas coals and anthracites through nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) experiments. In this study, these three different coal samples were denoted as HM, QM and WY, respectively. For HM, the aromatic structures are scarce and simple, the side chains are abundant and long, and many hydrophilic oxygen-containing functional groups are present on the surface. Thus, HM has strong hydrophilicity. For QM, the aromatic rings have compact structure, but the content of oxygen-containing functional groups approximates 50%, which means that QM can be easily wetted. For WY, the polycyclic aromatic structures are compact and the oxygen-containing functional groups on the surface are nearly detached. Therefore, WY is characterized by poor wettability. Then, two commonly-used suppressants (AEO-9 and rapid penetrant T) were used and coal dust wettability was measured. However, these two suppressants, especially the rapid penetrant T, show poor wetting performance on WY but work well with HM and QM. From the perspective of structure, the hydrophobic groups in AEO-9 are similar to carbon structures in WY, and thus AEO-9 is superior to rapid penetrant in the wetting performance of WY, according to the principle of like dissolves like. In other words, for the coal dusts with good wettability, the application of appropriate dust suppressants guarantees satisfactory dust removal performance. However, for the dusts with poor wettability, macromolecular surfactant with similar structures should be developed in order to achieve better dust removal performance.