Abstract
The presence of fine and ultra-fine gangue minerals in flotation plants can contribute to sub-optimal valuable ore recovery and incomplete water recycling from thickeners, with the performance of the latter equipment relying on adequate flocculation. In order to study the dependence of the flocculation process on the suspension-flocculant mixing conditions, a series of experiments—chosen using chemometric analysis—were carried out by varying mixing conditions, solid concentration, water salinity and flocculant dosage. To this purpose, two different tailings (both featuring coarse and fine content) were considered and a response surface methodology based on a Doehlert experimental design was used. The results suggest that the operational conditions to optimise the flocculated tailings settling rate and the suspended solids that report to a thickener overflow are not necessarily the same. This is a reasonable outcome, given that the settling rate depends on the coarse aggregates generated in the slurry, while the overflow solids content is governed both by either fine particle content (and its characteristics) or small aggregates. It is inferred that to maximise dewatering performance two stages should be involved—a separate treatment of the thickener overflow to remove fine content and thickening at optimal flocculant dosage to enhance this process.
Highlights
Water is a scarce commodity for many mining companies, in particular in countries such asChile, Australia and South Africa, where it is essential to minimise water consumption for massive large-scale operations placed in arid regions [1,2,3]
The thickening performance depends on three factors: (i) particle surface chemistry, especially of the fine particle contents, including the most common clays kaolinite and smectite, (ii) water chemistry, including dissolved salts along with both high and low molecular weight additives and (iii) hydrodynamic conditions to promote effective mixing
The intent of the present paper is to use the technique described above to analyse the impact of solid content, flocculant dosage, mixing rate and kaolinite content, both on settling rate and the resulting turbidity of the overflow after flocculation
Summary
Water is a scarce commodity for many mining companies, in particular in countries such as. The challenge of testing a representative number of concentrations of a single type of clay (n1 ), salt types (n2 ), salt concentrations (n3 ), mixing rates (n4 ) and flocculant dosage (n5 ) would require, following a full factorial design, n1 × n2 × n3 × n4 × n5 experiments to reproduce all possible combinations To avoid this potentially prohibitive amount of experimental measurements (especially for prospective testing purposes in metallurgical laboratories at mineral processing plants), the present paper proposes the use of chemometric analysis, defined as “the chemical discipline that uses mathematical, statistical and other methods employing formal logic (a) to design or select optimal measurement procedures and experiments and (b) to provide maximum relevant chemical information by analysing chemical data” [18] to optimise both the distribution and number of tests. The intent of the present paper is to use the technique described above to analyse the impact of solid content, flocculant dosage, mixing rate and kaolinite content, both on settling rate and the resulting turbidity of the overflow after flocculation
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