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.
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ABSTRACT: In the current work, we investigated a methodology to assess the potential energy savings when a fluidised-bed separator (i.e., the HydroFloat) is incorporated into a conventional flotation flowsheet for flotation of coarse sulphide minerals (chalcopyrite). Overall metallurgical performance of the new flotation set-up is compared to a single stage conventional flotation flowsheet. In the modified flowsheet, coarser particle sizes (+ 150 μm) from a coarse grind (d80 = 500 μm) were floated in the fluidised-bed separator whereas the finer particles (− 150 μm) were channelled to a conventional, agitated flotation cell. The coarser and high grade concentrate from the fluidised-bed separator was then reground and floated again using a mechanically agitated flotation cell. The energy used in grinding and regrinding was calculated using the bond work index formula and compared with the energy consumed when the total mass of sample was ground fine (d80 = 150 μm) and floated in the mechanically agitated flotation cell only. Observations made from the results indicate that the floatability of the coarse chalcopyrite particles in the fluidised-bed separator depended mostly on their liberation classes. The remaining unrecovered copper was either completely or mostly encapsulated by gangue minerals. Though the metallurgical performance of the conventional flowsheet was superior in terms of copper recovery, the modified flowsheet showed promise in terms of energy efficiency. The methodology developed herein may be used for assessing coarse flotation strategies as a function of ore mineralogy type.Powder Technology 05/2015; 275. DOI:10.1016/j.powtec.2015.01.065 · 2.27 Impact Factor
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ABSTRACT: The separation efficiency of the flotation process depends not only on differences in the physico-chemical surface properties of various minerals within an ore but also on the hydrodynamics of flotation. The aim of this article was to study the effects some fundamental hydrodynamic variables such as impeller speed on coarse particles flotation using a combination of factorial and one factor at a time experimental methods. As a function of impeller speed, the most important variable according to the factorial experiments, coarse-particle recovery increased with a Reynolds number around 119600, a Froude number of 1.53, and an air capacity number of 0.00346 and then decreased significantly due to the domination of the detachment mechanism in the process. Impeller clearance off-bottom was the second most important parameter and it was found that increasing impeller clearance off-bottom declined recovery as a result of decreasing the intensity of particle suspension. Frother concentration was the third most important parameter and the recovery increased by raising frother concentration up to 170 ppm, stayed steady between 170 to 200 ppm and then dropped. Also investigating the effects of solids showed that coarse coal recovery increases gradually by increasing solids concentration.International Journal of Coal Preparation and Utilization 05/2014; 34(5). DOI:10.1080/19392699.2013.879293 · 0.73 Impact Factor
Powder Technology 11/2014; 267:61–67. DOI:10.1016/j.powtec.2014.06.026 · 2.27 Impact Factor