Abstract

LIDDELL, K.S.; ADAMS, M.D.; SMITH, L.A.  and  MULLER, B.. Kell hydrometallurgical extraction of precious and base metals from flotation concentrates - Piloting, engineering, and implementation advances. J. S. Afr. Inst. Min. Metall. [online]. 2019, vol.119, n.6, pp.585-594. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/602/2019.

Kell is a hydrometallurgical treatment option for the recovery of platinum group metals (PGMs), gold, silver, and base metals from flotation concentrates to refined products on site. The process is cyanide-free, while eliminating emissions of sulphur dioxide, arsenic trioxide, and other toxic species often emitted by smelters and roasters. Kell has been tested on a range of concentrates, including PGMs (UG2, Merensky, Platreef, Great Dyke, Great Lakes, Lake Superior and others), refractory gold-silver, copper-gold, and polymetallic concentrates. High extraction efficiencies (>95%) are achieved for value metals (Pt, Pd, Rh, Au, Ag, Ni, Cu, Co) and secondary metals (Sb, Zn, Pb, and others). Studies comparing Kell with smelter-refining show economic benefits: capex 18-33% of smelting; opex 51-66%; electricity consumption 13-46%; and environmental benefits: greenhouse gas emissions 57-61% of smelting, acidification 5-27%, human toxicity 37-62%, and freshwater ecotoxicity 43-55% of smelting. Synergies for Kell plants alongside smelter-refineries include utilization of recovered acid from sulphur abatement systems and excess capacity in precious metal refineries. Kell is unconstrained by concentrate grade and impurities, allowing the co-location of Kell plants for treatment of non-smeltable concentrates alongside existing smelters. Kell has been demonstrated in a nine-week integrated pilot campaign at 1:1000 scale, supporting a bankable feasibility study for a 110 000 t/a plant treating a UG2-Merensky concentrate at Pilanesberg Platinum Mine (PPM), owned by Sedibelo Platinum Ltd, which has along with South African Industrial Development Corporation (IDC), invested in Kell. Zimbabwean Mining Development Corporation (ZMDC) has signed a Memorandum of Agreement (MOA) with KellTech for a centralized PGM concentrate processing plant.

Keywords : Kell; platinum group metals; base metals; hydrometallurgy; recovery; refining; environment.

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