Determination of oxidation properties and flotation parameters of low-rank coal slimes

Abstract

The oxidation properties and flotation parameters of low-rank coal slimes from Shuilian mine were researched in this paper. Because coal slimes remain piled up for long periods outdoors, they are highly susceptible to oxidation, which makes it difficult for them to undergo flotation. Based on elemental analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), different characteristics of fresh and oxidized coal slimes were compared. The results showed that coal slimes collected from Shuilian mine were characterized by high ash content, fine mud texture, low calorific value, and susceptibility to serious sliming. After oxidization, the O element content increased, whereas that of C and H elements decreased. Therefore, many oxygen-containing functional groups formed on coal slimes surface, such as C–O–C, C=O, and O=C–O, which imparted strong hydrophilicity, thereby reducing the flotation effects. Thus, with the aim to improve the flotation effects, we investigated the influence of flotation conditions, such as impeller speed, pulp concentration and air flow rate, on flotation effects. Based on our experiments, optimal flotation conditions were determined as follows: impeller speed, 1800 r/min; pulp concentration, 60 g/L; and air flow rate, 0.25 m3/(m2·min).