Effect of impeller rotational speed on the size dependent flotation rate of galena in full scale plant cells
ABSTRACT The first three rougher cells in the lead circuit of the Elura concentrator (formerly Pasminco Australia Limited) were selected as the plant cells for investigation. Metallurgical surveys were performed and various hydrodynamic measurements taken, allowing the galena flotation rate constant and the bubble surface area flux (Sb) in these cells to be calculated over a wide range of gas flow rates, and at two impeller rotational speeds. It was determined that altering the impeller rotational speed did not significantly change the rate constant dependency on Sb when flotation was considered on an unsized basis.The analysis was further extended to examine the same cells parameters on a size-by-size basis. The results obtained have been used to identify differences in the flotation behaviour of the various particle size fractions, independently of surface hydrophobicity. It is shown that the physical conditions for effective flotation of fine (<9 μm) and coarse (>53 μm) particle size fractions differ substantially, suggesting that a specific hydrodynamic environment will favour a high flotation rate for fine galena, which may be detrimental to the recovery of coarse galena, and vice versa. These observations are in accord with metallurgical practice that suggest that it is difficult to improve fine particle flotation without also compromising coarse particle stability efficiency simply by modifying the cell hydrodynamics alone. A fundamental flotation model was applied to quantify differences in the flotation rate of the various particle size fractions with impeller rotational speed.
Conference Paper: Optimization of a Novel Split Current Hall Device by Numeric Modeling[Show abstract] [Hide abstract]
ABSTRACT: We report the modeling and optimization of a novel split current Hall device. A unique advantage of the device is the reduction of the common mode sensor signal while the absolute sensitivity is kept. This is achieved by an additional current terminal. Numeric modeling with our finite element package SOLIDIS allows to separate the influence of the geometry and that of material properties on the sensitivity. We achieved an accuracy better than 5% with respect to the measurement data. Based on these results we optimized the device for maximum sensitivity and investigated the influence of several geometric parameters.Solid State Device Research Conference, 1995. ESSDERC '95. Proceedings of the 25th European; 10/1995
- Journal- South African Institute of Mining and Metallurgy 03/2013; 113(3). · 0.18 Impact Factor
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ABSTRACT: There is absolutely no question that a key role for an effective fine particle flotation plays the achievement of sufficiently high flotation velocities by means of large collision rates between the value mineral particles and bubbles in the strongly turbulent rotor (impeller) stream of the flotation machines. Therefore, a large ratio has to be aimed at (εR is the local energy dissipation rate in the impeller stream; νF is the kinematic viscosity of the fluid phase), i.e. εR should be as large and νF as small as possible. On the one hand, for that it is important to use an impeller–stator system having a large power number and an intensive internal slurry recirculation. On the other hand, a satisfactory dispersion state and thus advantageous rheological properties (low apparent viscosity) of the slurry must be aimed at. The latter effects a substantial reduction of the turbulence damping and with that not only an increase of εR in the impeller stream but also a decrease of its volume contraction. Furthermore, an adequate control of the entrainment into the froth lamellae plays a role in optimization.Minerals Engineering 01/2008; 21:930-936. · 1.21 Impact Factor