Research on the Enhancement of the Flotation of Low-Rank Coal Slime by Compound Collectors

High-efficiency flotation of low-rank coal slime is an urgent problem to be solved in the comprehensive recycling and utilization of coal resources. The flotation results presented that the flotation effect of a single collector on low-rank coal slime was poor, which made it difficult to improve its flotation index. When dodecamine was added alone, the yield and ash of cleaned coal were higher at 79.15 and 18.74%, respectively. With dodecane added alone, the yield and ash were only 30.57% and 12.85%, respectively. When diesel oil was added alone, the yield and ash content were 47.25 and 14.68%, respectively. The compound collector can significantly improve the flotation effect of coal slime. The compound collector of diesel oil and dodecane can obtain a flotation index of 66.32% yield and 11.53% ash, and the compound collector of dodecane and dodecane can obtain a flotation index of 74.01% yield and 13.27% ash. The surface potential test revealed that the positive shift with the compound collector of dodecane-dodecamine and diesel-dodecane was greater than that with the compound collector of diesel-dodecamine, resulting in a better flotation effect. Meanwhile, the contact angle test found that the contact angle of coal slime with diesel-dodecane and dodecane-dodecamine was increased from 45.46 to 68.52 and 63.95°, respectively, which greatly increased the surface hydrophobicity and floatability of coal slime. Thus, an efficient flotation method of low-grade slime with a compound collector as the core is provided.