Highly Promising Preliminary Testwork For Improving Copper Recoveries At Kamoa-Kakula

DEMOCRATIC REPUBLIC CONGO - Ivanhoe Mines reported on the on preliminary test work conducted to improve copper recovery at the Kamoa-Kakula Copper Complex. Kamoa-Kakula mine improvement in recoveries can result in significantly increased copper production. In 2022, Kamoa Copper's process engineering team, together with a number of internationally recognized external metallurgy specialists, initiated work to investigate ways to economically recover additional copper units from the tailings stream of the Phase 1 and 2 concentrators.

During 2022, the Kamoa-Kakula Copper Complex milled approximately 7.1 million tonnes of ore at an average feed grade of 5.5% copper, producing 333,497 tonnes of copper in concentrate. Based on the metallurgical recovery of 86% copper, which was in line with design parameters, in excess of 50,000 tonnes of copper was not recovered into concentrate and diverted to the tailings storage facility, or used underground as backfill. The grade of Kamoa-Kakula's tailings in 2022 averaged approximately 0.8% copper.

Kamoa-Kakula's ore contains fine-grained copper sulphides (chalcocite), which to fully liberate from the host rock requires grinding of the ore to fine particle size. Grinding rock to an ever-finer particle size is exponentially energy intensive. During the original flowsheet development, a trade-off was struck between recovery and energy intensity. The Phase 1 and 2 concentrator design has primary grinding to 80% passing less than 53 microns (-53 µm). This grind size is already significantly finer than most copper concentrators globally.

Copper recoveries from the Phase 1 and 2 concentrators have improved year-to-date, averaging 87.1% during H1 2023, and periodically achieving as high as 90%. However, any further sustained improvement in copper recoveries presents a significant opportunity to generate additional revenue at Kamoa-Kakula.

To date, 13 workstreams with separate entities have been initiated leveraging various technologies to improve copper recoveries. This includes the recently announced collaboration with I-Pulse Inc., as announced on June 15, 2023.

More recently, promising preliminary results were received from work conducted by Expert Process Solutions (XPS) of Falconbridge, Canada. XPS has worked with Kamoa-Kakula since project inception, conducting metallurgical testwork during the study phases before construction. Therefore, XPS has a high degree of experience working with both the Kamoa and Kakula deposits. Preliminary test results indicate a significant improvement in total copper recoveries can be achieved.

XPS was reappointed for a dedicated scope of work focused on grinding and reprocessing the tailings stream from the Phase 1 and 2 concentrators. Initial preliminary results indicate that with a feed grade of less than 1% copper, approximately 65% of the contained copper can be recovered from the tailings stream. The results generated a saleable concentrate with a grade of approximately 40% copper that could be processed on-site at the 500,000 tonnes-per-annum direct-to-blister flash copper smelter that is currently under construction. For comparison, the copper concentrate grade from the Phase 1 and 2 concentrators is currently approximately 50%. The test program consisted of fine-grinding the tailings stream to a particle size of 80% -12 µm, before conventional flotation, thickening and filtration.