Exploration on the mechanism of enhancing flotation of long-flame coal by diesel modification via oxidation

Low-rank coal is naturally hydrophilic, and the traditional hydrocarbon collectors often have poor performance in its flotation. In this study, the modification of diesel was conducted using an instantaneous gasification-oxidation-condensation device for the expected improvement of collector’s performance. Experimental analyses and interfacial interaction calculation were performed to explore the mechanism of enhancing flotation of long-flame coal by diesel modification. It indicated that the flotation of coal sample can be greatly enhanced by the modified diesel, and a combustible matter recovery of 90.52 % could be attained only consuming 6 kg/t of modified diesel which was far better than the flotation effect consuming 100 kg/t of common diesel. The improved flotation effect of the coal sample could be attributed to the increased polarity of collector from 0.48 % to 9.76 % resulted from the newly added oxygenated functional groups after the oxidation of diesel, which significantly enhanced the adsorption capacity of the collector on the long-flame coal surface reflected by the FTIR and XPS analyses. Furthermore, the calculated results of interfacial interaction between the coal sample and the common/modified diesel suggested that the efficient adsorption of modified diesel on the coal sample was achieved through the bridging role acted by water molecules. This research may give some insight into enhancing flotation of low-rank coal.