Flowsheet development for and commissioning of the Kamoa-Kakula project

Abstract

The Kamoa-Kakula copper resource, located west of Kolwezi in the Democratic Republic of the Congo, was discovered and explored by Ivanhoe from 2008/9 on. As a greenfield project with prospects of high grade ore and a long life-of-mine, the need for best practice flowsheet development was recognised, so as to ensure sustainability of metallurgical performance at the at the maximum economic level from the orebody during metallurgical operations. Process Mineralogy, a hybrid discipline, has been developed in the mining industry over the last forty years, and its proper use has seen very successful outcomes in flowsheet development (Bradshaw, 2014; Lotter, 2011; Lotter et al., 2003; McKay et al., 2007; Pease et al., 2005). Drill core was sampled at site across six phases of flowsheet development that worked with the developing mine plan. The two main geomet units were hypogene and supergene, with the hypogene being unusually rich in bornite. The main variability is between supergene and hypogene, and between Kamoa and Kakula, but with less spatial variability within them. The first viable flowsheet was developed and demonstrated in nine months of test work, followed by various revisions and iterations as required by the discovery of variable mineralogy. The first flowsheet, called “Milestone”, was then challenged with an opportunity for a simpler but better-performing flowsheet, which became known as IFS4A. The simultaneous discovery of the Kakula resource refocussed the project due to its shallower depth and higher grade. Laboratory scale flotation testing using IFS4A in Phase 6 of Kamoa and two drill-holes of Kakula quickly confirmed that the Kakula ore outperformed the Kamoa supergene ore using this flowsheet. A mini-pilot plant campaign was run in 2019 with this flowsheet plus modifications, using 985 kg of metallurgical drill cores material to demonstrate the full flowsheet mass and value balance on a continuous operating campaign. This mass and value balance produced an estimated 85.6 % Cu recovery with a saleable concentrate grading 57.3 % Cu. Whereas this paper concentrates on the mineralogy and its contribution to process implications such as grinding requirements and flotation strategy, it is recognized that first-class design, engineering and construction contributed in no small measure to the successful start-up. This mass and value balance was used in the design of the grinding and flotation circuits, and contributed to the successful commissioning of the new concentrator in 2021, which averaged a recovery of 84.7 % at a grade of 50.5 % Cu, in good agreement with the testwork. A McNulty model for the commissioning data shows a better than Type 1A start-up. The flowsheet development part of the project is discussed in this paper as a case study.