Document Type : Original Research Paper
Authors
1 Mining Engineering Department, Tarbiat Modares University.
2 Department of mining engineering, Arak university of technology, Arak, Iran.
Abstract
The main characteristic of mechanical flotation cells is to have an impeller, which is responsible for creating particle suspension, gas dispersion, and producing turbulence necessary to create effective bubble-particle interactions. For this purpose, in this paper, the conditions for complete gas dispersion in a Denver laboratory flotation cell have been investigated. Then, the critical impeller speed has been investigated for quartz particles with different size fractions. The effect of complete dispersion of introduced gas and critical impeller speed on the flotation rate constant (k) of particles was investigated. The results showed that k was the minimum value at an impeller speed of 700 rpm in the superficial gas velocity of 0.041- 0.125 cm/s for all size fractions. The impeller speed of 700 rpm was sufficient to keep -106µm quartz particles suspended, but at all superficial gas velocities, the minimum impeller speed required for complete gas dispersion was 850 rpm. Therefore, it can be stated that the reason for the low k value at a stirring speed of 700 rpm is the incomplete distribution of bubbles and particles (+106µm), resulting in a reduced probability of air bubbles colliding with solid particles. By increasing the impeller speed to values greater than 700 rpm, the k value increased, which is due to the complete distribution of particles and air bubbles in the flotation cell (increased probability of bubble-particle collision). Therefore, it is necessary to provide suitable operating conditions for the complete dispersion of air bubbles and also to keep solid particles suspended.
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