Optimization of Reagents Distribution Down a Coal Flotation Bank to Improve the Recovery of Coarser Particles

Fine coal (− 0.5 mm) is treated in a flotation circuit at Bhelatand washery of Tata Steel. The average ash content of the flotation feed, the fine clean coal, and the tailings of the flotation circuit are 18.5%, 12.5%, and 36%, respectively. The yield of clean coal from the flotation circuit is about 72%. However, the performance of the circuit in terms of clean coal yield is not satisfactory. The feed to the flotation contains 15–20% of oversize (+ 0.5 mm) fraction because of the inefficiency of the desliming screens. These oversize materials, which are of high carbonaceous value, are not efficiently recovered through the flotation process. Hence, the major challenge is to improve the flotation kinetics of the coal fines, especially the oversize particles. The way flotation reagents are distributed down a flotation bank can positively influence the flotation response of oversize particles. Hence, two-stage reagent distribution, with extra amount of reagent in the second stage, was studied in the laboratory. Results of laboratory-scale studies showed an improvement in yield of clean coal of 10–12% with a marginal increase of clean coal ash content. Based on encouraging laboratory findings, the idea was implemented in the plant, which showed a substantial improvement in the yield of clean coal from 74% to 84% with marginal increase in clean coal ash content.