| Froth flotation is a separation process, which utilizes the difference in surface properties (such as surface hydrophobicity) of mineral particles to be separated. The separation is effected by a selective adhesion of air-bubbles to hydrophobic solid surface. In conventional flotation cells, in addition to selective hydrophobic attachment, hydraulic entrainment mechanism also plays a significant role in the recovery of ultrafine particles thus affecting the quality (grade) of flotation concentrate. Many advanced flotation systems, having sophisticated bubble generators and froth washing features, have been developed and commercialized over the years to eliminate some of the deficiencies of the conventional flotation cells. G-Cell (where G stands for gyratory) is one such advanced flotation system, which is a relatively new design modification of the Imhoflot pneumatic flotation technology that utilizes a self-inducing aerator inside a downcomer.;The present study aimed at investigating the suitability of the G-Cell technology for cleaning fine coal, for the first time in the U.S., using a 0.8 meter diameter prototype unit at a coal preparation plant operating in the Midwestern United States. A slip-stream was obtained from the overflow of raw coal cyclones operating in the plant, containing nominally minus 150 micron size particles and having ash content in the range of 40% to 50% and sulfur content in the range of 1.30% to 1.50%, was used as the feed for the G-Cell. A statistically designed experimental program has been conducted to investigate the parametric effects on various key process responses, such as combustible recovery, product ash and sulfur rejection. The empirical models developed in this study have been utilized to identify a suitable experimental region for achieving a desired combination of response targets. Single stage G-Cell test, even with high recirculation of tailings, failed to provide high combustible recovery values. Two-stage (rougher-scavenger) tests had to be conducted to allow the G-Cell combustible recovery value approach the maximum predicted by the release analysis. |
