Effective Beneficiation of a Fine Coking Coal Using a Novel Flotation Scheme

Effective flotation of fine coal remains challenging due to flotation inefficiency, of coarse, intergrowth particles, and contamination due to fine particles. In this article, a novel flotation scheme, named split-conditioning and bulk-flotation (SCBF), has been proposed to improve flotation efficiency of coarse and fine particles. The conditioning time and impellor speed of the flotation machine for coarse and fine particles were optimized using the nine well-planned orthogonal experiments. The results demonstrated that, by using the SCBF approach, an increase of 12.43% recovery for +0.074 mm particles and a decrease of 2.42% ash content in the -0.074 mm fractions were obtained compared to the conventional flotation. Based on the orthogonal experiments analysis, the optimal mixing conditions for +0.074 mm particles were an impellor speed of 2100 rpm and a conditioning time of 240 s, whereas, for the -0.074 mm size particles, an impellor speed of 2100 rpm and a conditioning time of 60 s were found to be the most important factors in SCBF. It was found that, for +0.074 mm particles, a higher impellor speed and a longer conditioning time improved the recovery of coarse particles, and a shorter conditioning time for the -0.074 mm particles reduced the contamination in clean coal.