Abstract

MEGAW, D.; MOOLMAN, J.; MUZADI, P.  and  MARCUS, T.. Copper sulphate crystallization plants at remote locations. J. S. Afr. Inst. Min. Metall. [online]. 2017, vol.117, n.8, pp.779-784. ISSN 2411-9717.  https://doi.org/10.17159/2411-9717/2017/v117n8a8.

The Central African Copperbelt is well known for its high-grade copper-cobalt deposits. Many hydrometallurgical copper refineries have been established in northern Zambia and in the Haut-Katanga and Lualaba provinces in the Democratic Republic of Congo to treat such orebodies. As the high-grade deposits at primary refinery sites become depleted, new ore deposits are exploited. These new deposits are often situated some distance from the refineries, thus necessitating upstream mineral processing in order to produce a concentrate that is then transported to the refinery, usually by road. In this paper a processing route that produces a copper sulphate product at the remote ore location is presented as a possible alternative to the production of a concentrate by dense media separation (DMS). The alternative process comprises crushing and screening of the ore, heap leaching, solvent extraction, and copper sulphate crystallization. Similar technology has been successfully implemented in South America; however, these plants have targeted copper sulphate as a final product, primarily for the animal feed additive market. Although the production of feed-grade copper sulphate offers producers a premium on the final product, the market demand is limited. The demand for LME-grade copper metal is orders of magnitude higher than that for feed-grade copper sulphate. An advantage of satellite copper sulphate production is that copper units supplied to the refinery for cathode production require less secondary processing than a DMS concentrate. The end product is attractive for copper cathode producers that have un-utilized solvent extraction (SX) and electrowinning (EW) capacity. When added to SX, the sulphate associated with the copper sulphate is recovered as sulphuric acid in the raffinate, supplementing the fresh acid requirements for leaching. The copper sulphate purity is such that it can also be added intermittently to the EW strong/advance electrolyte circuit, although care must be taken to maintain the sulphate balance in the EW circuit. The advantages and disadvantages of the two processing routes are compared.

Keywords : copper; copperbelt; solvent extraction; mineral processing; crystallization.

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