Comparison of mechanical and column flotation performances on recovery of phosphate slimes in presence of nano-microbubbles

Abstract

Fine particle flotation has been one of the main problems in many mineral processing plants. The bubble-particle collision rate is very low for fine particles, which reduces flotation efficiency. Also, the existence of slimes is, generally, detrimental to the flotation process, affecting the selectivity and the quality of the concentrates. Besides, it causes an increase in reagents consumption. Hence, in most of processing plants, some of these particles are transmitted to the tailing ponds to reduce the effects of these problems and increase the selectivity of the process. Esfordi phosphate plant in Iran loses more than 30% of its capacity as particles with d₈₀ finer than 30 µm. These fine particles with 15.9% P₂O₅ content are transferred to tailing dam. Processing of fine particles is very important for phosphate industry from economic and environmental aspects. This study addressed the processing of fine tailings (slimes) from a phosphate ore concentrator via flotation, despite the traditional view that ultrafine particles do not float. Phosphate flotation performances in the presence and absence of nanobubbles (NBs) in both mechanical and column cells were compared according to the metallurgical results of the process. NBs (generated by hydrodynamic cavitation) have interesting and exclusive properties such as high stability, durability and high surface area per volume, leading to increase of their utilization in mining-metallurgy and environmental areas. The results of this study revealed that, in the absence of NBs, a concentrate containing 26.9% P₂O₅ with a recovery of 29.13% was obtained using mechanical cells in comparison to 31.6% P₂O₅ with a recovery of 32.74% obtained using column flotation. In the presence of NBs, the recoveries of the concentrate of the mechanical and column flotation increased to 40.49% and 41.26% with 28.47% and 30.43% P₂O₅ contents, respectively. Comparative study showed that the column flotation was almost more efficient for processing the phosphate ore in the presence of the NBs, and had thicker froth layer compared to the mechanical flotation.

Keywords

column flotation / mechanical cell / phosphate / tailings / slime / nanobubble / Venturi tube / hydrodynamic cavitation

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