Abstract
The problem of low-rank coal flotation continues to be a challenge due to the poor hydrophobicity and abundant oxygenated functional groups on particle surfaces. In this study, carrier flotation was used to improve the flotation performance of low-rank coal with polystyrene as a carrier material. Kerosene was used as a collector and played a role in the adhesion of fine low-rank coal to polystyrene due to its hydrophobic properties. The carrier feature of polystyrene was demonstrated by Turbiscan Lab Expert stability analysis and scanning electron microscopy analysis. The flotation experiments revealed that the optimum conditions were: collector dosage 5000 g/t, pulp concentration 40 g/L, and the ratio of low-rank coal to polystyrene 100:10. Under these conditions, the combustible recovery by carrier flotation was obtained as 70.59% when the ash content was 12.32%, which increased by 25.68 points compared with the combustible recovery of conventional flotation under almost the same ash content. The fine coal particles coated the coarse polystyrene particles through hydrophobic interactions between the polystyrene and hydrocarbon chains of the kerosene adsorbed on coal particles. The results suggested that the flotation performance of low-rank coal was significantly improved by carrier flotation with polystyrene, especially for fine particles.
Highlights
Froth flotation is an efficient method for the upgrading of fine coals of less than 0.5 mm [1,2,3].low-rank coals are very difficult to float with ordinary collectorsdue to abundant oxygenated functional groups on their surfaces, such as hydroxyl and carboxyl groups, which hinder the adsorption between low-rank coal particles and collectors [4,5]
The results suggested that the flotation performance of low-rank coal was significantly improved by carrier flotation with polystyrene, especially for fine particles
The polystyrene particles in float and sink products were separated from coal particles by 0.25 mm sieving, and the combustible recovery and ash content were calculated after removing polystyrene particles
Summary
Froth flotation is an efficient method for the upgrading of fine coals of less than 0.5 mm [1,2,3]. Numerous researchers have contributed to exploit new collectors [6,7,8,9,10] and particle surface treatments (ultrasonic, grinding, heat treatment and microwave, etc.) [11,12,13,14] for improving the flotation performance of low-rank coals. Carrier flotation has been tested in a variety of ores, and proven to be beneficial for improving flotation performances [15,16,17,18] In this technique, the particles which will be floated coat the carrier materials, and all of them are floated together [19]. The carrier flotation was used to improve flotation performance of low-rank coal with polystyrene as the carrier material. Experimental scanning electron microscopy (SEM) analyses were applied to analyze particle aggregation
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