![]() The cobalt was recovered from a raffinate bleed stream by iron and copper precipitation processes, followed by precipitation of a basic cobalt hydroxide sulphate by-product utilizing soda ash as a precipitant. The pregnant leach solution (PLS) recovered from the heaps was clarified and then processed through SX and EW circuits to produce the copper cathode product. The selected irrigation rate took advantage of the rapid leaching kinetics of malachite. The undersized ore (-625 um 'fines') was removed from the feed in order to allow for a maximum heap irrigation rate of 90 L/m2/h. ROM ore was processed through two crushing and washing plants to produce a sized ore (-50 mm +625 um) for the heap leach operation. The Luita plant block flow diagram as it was in 2015 is illustrated in Figure 1. This process design challenges the boundaries of conventional thinking in the areas of leaching, solid/liquid separation, solution management, impurity management, and metal recovery, and is the subject of this paper. The revised Luita circuit reached design capacity in November 2017 and has proven to be well suited to processing of the oxide ore feed. Central to this was the installation of a tank leach circuit to process the discarded fines and a modified SX circuit to manage colloidal silica. This set in motion a range of improvement initiatives for the Luita operation. The London Metal Exchange (LME) copper price dropped below US$2.00 per pound, with cobalt dropping below US$10.00 per pound in Q1 2016. The initial Luita operation was established in 2010 at a time when metal prices were above long-term averages (copper above US$3.00 per pound cobalt above US$20.00 per pound), and the drop in prices in 2015/2016 presented a major challenge. The operating cost for the process as then installed placed this facility well in the fourth quartile of the industry cost curve. In a subsequent development, the cobalt SX section was converted to a copper SX facility, the leached cobalt being recovered from a bleed stream from the copper heap leach circuit. This fraction carried with it approximately 30% of the copper contained in the run-of-mine (ROM) ore feed, and an equivalent proportion of cobalt. In preparing the sized ore for the heap leach operations, the undersized ore fraction at a P 80 of 625 um was discharged to a fines storage facility for later processing. The process was originally conceived as a heap leach operation followed by direct electrowinning of copper, with solvent extraction (SX) and electrowinning (EW) of cobalt. Keywords: copper, cobalt, process design, oxide ores, solvent extraction, colloidal silica management.ĮRG Africa operates the Luita hydrometallurgical facility located at Kakanda in the Democratic Republic of Congo (DRC), treating malachite and heterogenite minerals to recover copper as electrowon cathode and cobalt as a hydroxide precipitate. Of these changes, the most novel presented an alternative approach to mitigate the impact of colloidal silica on the operation of the solvent extraction plant. A number of innovative changes to the conventional process design were included in the modified flow sheet, which were validated when the project reached design throughput in November 2017. ![]() In 2015, ERG Africa began a project to expand the leaching capacity of the Luita hydrometallurgical facility. The physical characteristics of the oxide ores, however, provide the process design engineer with an opportunity to examine critically the principles on which equipment selection is based and to design processes better suited to these ores. The design of metallurgical processes for these oxide ores is based on the conventional equipment and layout for processing of sulphide ores, and comprises milling followed by leaching, solvent extraction, and electrowinning. The greater proportion of this expansion has arisen through processing of oxide ores. The mining industry in the Democratic Republic of Congo has seen a significant expansion in copper and cobalt production in recent years. IIBoss Mining, Democratic Republic of Congo ![]() Innovative process design for copper-cobalt oxide ores in the Democratic Republic of Congoĭ.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |