Abstract
Abstract The agitation intensity has a directly influence on flotation performance, lifting the particles and promoting the contact of bubbles and particles. In this paper, the energy input by the agitation on apatite flotation was investigated. The influence of pulp agitation in the flotation rate of particles with different sizes and two dosage levels was evaluated by batch testing. The flotation tests were conducted in an oscillating grid flotation cell (OGC), developed to promote a near isotropic turbulence environment. The cell is able to control the intensity of agitation and measure the energy transferred to the pulp phase. A sample of pure apatite was crushed (P80=310µm), characterized and floated with sodium oleate as collector. Four levels of energy dissipation, from 0.1 to 2 kWm-3, and two levels of collector dosage are used during the tests. The flotation kinetics by particle size were determined in function of the energy transferred. The results show a strong influence of the agitation intensity on the apatite flotation rate with both low and high dosage. For fine particles, when increasing the energy input, the flotation rate increase too, and this fact can be attributed to elevation of bubble-particle collisions. The kinetic result for the coarse particles demonstrated a reduction of the flotation rate whenever the energy input for this particle size was increased, whereby the turbulence caused by the agitation promotes the detachment of bubble-particle.
Highlights
The agitation in a conventional flotation machine is promoted by the rotor-stator system with the turbulence suspending the particles and drawing the pulp through the stator to disperse the bubbles, promoting the contact of bubbles and particles (Schubert, 1999)
This study investigated the effect of energy/agitation input on the flotation of apatite in an oscillating grid flotation cell (OGC)
One may conclude that the effect of energy/power input on the flotation rate is strongly dependent on the particle size and collector dosage
Summary
The agitation in a conventional flotation machine is promoted by the rotor-stator system with the turbulence suspending the particles and drawing the pulp through the stator to disperse the bubbles, promoting the contact of bubbles and particles (Schubert, 1999). To avoid the effect of anisotropy caused by impeller in mechanical cells and investigate the effect of energy, Changunda et al (2008) developed a flotation cell with oscillating grid. In this cell, the agitation is promoted by the oscillatory motion of parallel grids positioned inside the machine. The results of Massey (2011) using Oscillating Grid Cell (OGC) show concordance with the literature of stirred flotation cells using low energy input. The results show that for fine particles, the increased energy stepped up the flotation rate, while for coarse particles, the effect of the inserted energy in flotation is the opposite, reducing the rate of flotation
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