Direct measurement of entrainment in large flotation cells

A key response variable to describe the metallurgical performance in a flotation cell is the concentrate grade. The mineral feed characteristics and conditioning determine the grade of the particles attached directly to the surfaces of the bubbles by true notation, while the operating conditions, such as gas rate, bubble size, froth depth and others, determine the amount of gangue recovered by entrainment. which finally decreases the concentrate grade. In this paper, the recovery of liquid and solids by entrainment was evaluated by direct measurement of the fraction of liquid and solids reported to the concentrate in a 130 m(3) mechanical flotation cell. The liquid and solids entrainment, per size classes (+150; -150+45; -45 mu m). was measured by the radioactive tracer technique. The procedure consisted of introducing a tracer impulse at the cell feed entrance. The tracer time response was monitored on-line at the concentrate overflow and at the tailings discharge. Also, in order to obtain the quantitative distribution of the feed, samples were taken periodically from the concentrate and tailings streams. for a period of 4 residence times, during the tracer tests. This allowed the quantification of the mass of tracer reporting to both streams. Experimental results confirmed that solids entrainment with the froth was strongly dependent on particle size, and that the entrainment factor (EF=solid/water recovery ratio) was similar to that reported for smaller size Cells under similar operations conditions. (C) 2008 Elsevier B.V. All rights reserved.