Abstract
In mineral processing, the common requirement for progressively finer milling due to the decreasing of ore grades implies the need for more challenging water recovery conditions in thickeners. Several mining operations exist in arid areas, where water recovery becomes critical. The present paper explores the process of particle separation in batch inclined settlers where the downward facing wall is subject to heating. To this purpose, two-dimensional numerical simulations using a mixture model have been run for a number of combinations of temperature jumps at the downward facing fall, particle diameters, and concentrations. Results show that, for particle sizes on the order of 10 µm, heating has a significant effect on the particle settling velocity at the bottom, but it also promotes particle resuspension, affecting the particle concentration at the supernatant layer. The initial concentration also affects settling: for the concentration range tested (8%–15% by volume), when re-normalized by the average concentration, particle accumulation rates at the bottom were found to be lower for higher average concentrations, thus suggesting that the separation process is more efficient at lower concentrations.
Highlights
Solid-liquid separation in mining operations is a critical unit operation occurring in commonly adverse conditions such as water scarcity, energy cost [1,2,3], or a naturally fine particle size range [4,5,6]
The Boycott effect induces particle accumulation at the upward facing wall, which transport them towards the bottom
This single result represents no proof of a trend due to the limitations of the numerical scheme used for computations—a mixture model, where close interaction between particles has only been regarded via a concentration-dependent viscosity and a solid phase pressure term—it is suggested that the effect of particle size on the separation efficiency should be analyzed in light of a time scale based both on the settling velocity and the convective process
Summary
Solid-liquid separation in mining operations is a critical unit operation occurring in commonly adverse conditions such as water scarcity, energy cost [1,2,3], or a naturally fine particle size range [4,5,6]. While there are several means to recycle water, including centrifugal separation and filtration [7], due to its considerably low cost per recovered m3 water, gravity settling [8] is still the most commonly-used technique in the sector Among this type of technology are lamellar settlers, which are a type of process equipment consisting of a vessel fitted with a set of parallel inclined plates immersed in a slurry vessel. This working principle is explored, for the first time, in combination with the use of heat, considerably abundant from natural sources in arid areas, to further enhance the particle settling process To this purpose, a set of two-dimensional numerical simulations for the case of batch settling within a single convection cell consisting of two parallel inclined plates is presented and analyzed.
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