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Copper solvent extraction: Status, operating practices, and challenges in the African Copperbelt

2016; Academy of Science of South Africa; Volume: 116; Issue: 6 Linguagem: Inglês

10.17159/2411-9717/2016/v116n6a10

2411-9717

Kathryn C. Sole,

Metal Extraction and Bioleaching

Following the success of the Rancher's Bluebird and Bagdad solvent extraction and electrowinning (SX-EW) operations in Arizona in the late 1960s, the Tailings Leach Plant at Chingola, Zambia, became the first large-scale copper SX plant in the world, commissioned in 1974.Despite the equipment design now being outdated, this plant still continues to operate successfully, indicating the versatility and adaptability of this technology.Today, there are some 75 copper SX operations worldwide with cathode production above 10 kt/a.The top ten producers currently account for about 40% of the global 4.3 Mt/a SX-EW copper production.South America (predominantly Chile and Peru) is the largest copper cathodeproducing region, with annual production of some 2 Mt.The Central African Copperbelt (Zambia and the Democratic Republic of Congo (DRC)) is second, with cathode production of 1.2 Mt/a, and North America (USA and Mexico) third, producing close to 0.8 Mt/a Cu (Solvay Cytec data, 2014).The remaining 0.35 Mt/a comes from all other regions combined (referred to as 'Rest-of-World').Current operations in Zambia and the DRC are summarized in Figure 1.The industry in this region is characterized by a few very large (>200 kt/a) operations, owned by major multinational corporations, and a large number of small (3 to 20 kt/a) plants, mainly Chinese-owned.This paper examines typical SX operating practice in the African Copperbelt, discusses differences compared with other parts of the world, and looks at some of the challenges presented by the conditions, as well as innovations in flow sheets, reagents, and operating conditions that have been introduced in these circuits.Distinct characteristics emerge when one examines copper SX on a regional basis.Table I compares characteristics of the pregnant leach solutions (PLS) in Central Africa with those of North America, South America, and other parts of the world where copper SX is practiced.The nature of the PLS varies considerably (0.23 to 43 g/L Cu), depending largely on the type of process and geographic location (Sole et al., 2013).The versatility of this technology is indicated by its ability to cope with large variations in copper grade as well as selectively recover copper from widely varying PLS compositions.Extreme examples include Mexicana de Cananea (Mexico), which processes a feed containing 2 g/L Cu and 45 g/L Fe, and Cobre Las Cruces (Spain), which recovers >40 g/L Cu from a PLS background of >50 g/L Fe.Copper grades are typically lowest in the southwestern USA, where the industry is mature and many operations have been in production since the mid-1980s.The ores are mainly lower-grade mixed oxide andCopper solvent extraction: status, operating practices, and challenges in the African Copperbelt by K.C.