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Effect of pulp rheology on flotation : the nickel sulfide ore with asbestos gangue system Kilickaplan, Isil

Abstract

Pulp rheology is a sensitive indicator of the state of aggregation/dispersion of mineral particles. In this study, possible correlation between the rheological properties of flotation pulp and the flotation response was investigated through a series of rheological and batch flotation tests. The nickel-sulfide ore from the Mt. Keith plant (Western Australia) was used for the tests. It is a low-grade nickel sulfide ore which is characterized by complex mineralogical composition with a large content of serpentine minerals. The experimental program included agglomerate flotation tests and rheological tests with the use of a slurry produced by grinding the nickel-sulfide ore. In order to see the effect of solids content on flotation, a series of tests were performed at various pulp densities in the absence and presence of oil in both conditioning and flotation stages. The agglomerate flotation and rheological tests were repeated with dispersants in order to investigate the correlation between degree of agglomeration/dispersion and flotation response. The agglomerate flotation tests conducted at various solids content in the flotation stage revealed that the fastest flotation rate was observed at the lowest solids content. The entrainment was found to increase with increasing solids content due to elevated pulp viscosity. The “boiling” was observed in the flotation cell in the tests at a high pulp density, the effect likely associated with a high pulp viscosity. High pulp viscosity is clearly increasing the size of bubbles in the flotation system. In line with this the high recoveries by entrainment are observed in the tests at high pulp density. Under such conditions the concentrate grade was low since a large proportion of the nickel recovery resulted from entrainment. In distilled water the use of a dispersant improved considerably flotation performance. The presence of chrysotile in the system strongly affects the pulp viscosity. In the tests with pure chrysotile the pulp with a solids content of around 0.8% by volume is close to the critical packing fraction. However, in the tests with the nickel ore containing more than 80% of chrysotile the viscosity is still far from the critical packing even at 7.6 % solids content by volume. This shows a very beneficial dilution effect; the presence of other non fibrous minerals dramatically decreases the viscosity of the chrysotile suspensions. Without such minerals processing of this ore would have been entirely impossible.

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