Two-stage fast flotation of coal tailings using reflux flotation

Abstract

Low pulp density and low grade slurries in the coal and minerals industries are discharged as waste to tailings dams, incurring significant losses of valuable particles. This paper investigates the rapid processing and cleaning of hydrocyclone overflow coal slurry using two laboratory scale Reflux Flotation Cells in series as a means to economically beneficiate low quality tailings streams. The Reflux Flotation Cell incorporates a novel arrangement of inclined channels to enhance bubble-liquid segregation, enabling extremely high gas rates and liquid rates per unit of vessel area. Hence, in the first stage, fast flotation is employed to rapidly recover fine coal particles using a feed flux of 11.4±0.5cm/s, up to an order of magnitude increase in the throughput rate over conventional flotation systems. First stage product was then sent to a second stage for counter-current washing using fluidisation wash water to produce a fully deslimed product, having ash percent in agreement with the minimum ash attainable using flotation as determined through tree flotation analysis. The results demonstrate the potential for two-stage Reflux Flotation to deliver high throughput at a high separation efficiency from low quality slurry, with a fivefold reduction in the required vessel footprint, thus overcoming the principal economic deterrent of having to install banks of large-scale flotation cells.