Recovery of copper from dump slag by a segregation process

Abstract

The need to treat copper ores and wastes and the diminishing size of the ore deposits has become an impetus for the development of many non-traditional processes aimed at complete extraction of valuable components. Recently, the attention of research scientists has again been focused on chlorination. One of the methods that still holds some potential is segregation roasting. The segregation process was discovered accidentally in 1923, when an oxide copper ore containing chloride was reduced with coal [1]. In basic terms, segregation roasting consists of heating copper ore to 600–800°C with 1–6% of a chlorinating agent and 2–4% carbonaceous reducing agent. The metals are converted to volatile chlorides, which are subsequently reduced to metallic particles 10–50 μm in size. The metals can finally be recovered by froth flotation or magnetic separation. The segregation process appears to have several advantages over other methods of treating oxide ores. The amount of reagent required for the treatment is reduced by 10 to 20 times and the overall recovery of the metal is very high. The flotation concentrate is normally sent to a smelter or can be treated by hydrometallurgical techniques. The feed to the segregation process can be ore of different mineralogical composition, containing high amounts of iron, silicon and magnesium oxides. Since the process is kept below 1000°C, compared with over 1600°Cfor the smelting alternative, a total of 25–30% energy saving is anticipated for a full-scale plant [2] for treatment of nickel oxide ores. Previous investigators studied the application of segregation roasting of copper sulphide ores [3], refractory oxide ores [4], roasted copper concentrates [5,6], and converter slag [7] as a means of recovering metallic copper. In the present investigation an attempt was made to extract copper from dump slag by segregation roasting.