Improvement of Extraction Efficiency at Kamoto Copper Company's High Grade Train 1 KCC SA

This study seeks to resolve a practical problem encountered in solvent extraction. This problem relates to the copper extraction yield in the high-grade circuit. Between July and September 2024, constraints related to increased production and increased demand for HG raffinate led to an increase in feed flow, which increased transfer but resulted in a decrease in copper extraction yield to average values of 80%. Low extraction yield would mean potentially lower copper recovery at the stripping stage, raffinate richer in residual copper and, in addition, low overall plant productivity. The main objective of this research was therefore to improve copper extraction efficiency, taking into account the increase in feed flow rate, in order to ensure an optimal amount of copper transfer, which would enable the plant to meet its annual production targets. To do this, a sample of the discharged organic phase and another of the solution from the PLS leaching process were taken at the plant and then characterised for use in laboratory extraction tests. Thirty extraction tests were carried out, varying four parameters in turn to the following values: pH (1.2; 1.4; 1.6; 1.8; 2; 2.2 and 2.4), the O/A ratio (1/3, 1/2, 1, 2/1, 3/1, 4/1, 5/1), the residence time (1; 2; 3; 4 and 5 min) and agitation speed (400; 600; 800; 1000; 1200; 1500 and 1700 rpm). The optimum values for these parameters will be used to establish simulation isotherms in order to adapt the flow rate to the flowsheet. At the end of this study, the results obtained when applied to a simulation with ISOCALC showed that an efficiency of 84.76% could be achieved by feeding 900m3/h into a series-parallel circuit with a flow rate of 500m3/h on the series stages and 400m3/h on the parallel stage, with a parallel O/A ratio of 2.8, a pH of 1.28, a residence time of 3 minutes and an agitation speed of 100 rpm.3/h on the parallel stage at an O/A ratio of 2.8; a pH of 1.28; a residence time of 3 minutes with an agitation speed of 800 rpm for an organic extractant of 23.12%. These conditions would also minimise the co-extraction of iron to 31.32%. An extractant was added up to 28% under the same conditions and we obtained an extraction yield of 92.32% and a transfer of 277.15 tonnes/day.