Panorama pins hopes on tailings recovery

An eerie silence prevails over the mills and monstrous open pits at the Kambove and Kakanda mining areas — an indication that Zaire, once a powerful player in the copper market and the world’s leading producer of cobalt, has fallen on hard times.

Situated 130 km northwest of Lubumbashi in the country’s once-prolific copper belt, the mine sites have been eclipsed by the cobalt mines of Kolwezi, 125 km to the west, where most of the country’s base metal producers are clustered.

However, the void at Kambove and Kakanda could soon be filled, at least in part, by a tailings recovery project undertaken by International Panorama Resource (ILP-V), as a joint venture with the Zairian state mining company, Generale des Carrieres et des Mines (Gecamines).

Panorama gained a 51% stake in the project in August 1996, when it took over a private company, PTM Minerals, for an immediate cash payment of US$250,000 and a series of share issues amounting to a total of 11.5 million shares.

PTM’s agreement with Gecamines provided that Panorama could complete a feasibility study and then opt to take a 51% interest in the project. If the project went into production, 85% of revenue would be diverted to pay back Panorama’s capital expenditures and startup costs, and the remaining 15% would be split pro rata, allowing Gecamines some immediate cash flow from the project. After the payback period, Gecamines would retain a 49% interest in profits plus a 1.5% net smelter return royalty.

The tailings resource at Kambove consists of a body of sulphide and dolomitic oxide tailings with 27.5 million tonnes grading 0.64% copper and 0.15% cobalt, and a body of clay and dolomitic oxide tailings with 9 million tonnes grading 1.63% copper and 0.33% cobalt. At Kakanda, the company has three zones, including an oxide-silicate structure with 17.1 million tonnes of 1.15% copper and 0.18% cobalt. Also present are two oxide-dolomite zones — one with 6.3 million tonnes of 0.93% copper and 0.16% cobalt; the other with 1.2 million tonnes of 1.67% copper and 0.33% cobalt.

What is all that metal doing in the tailings? Put it down to the copper belt’s metallurgical history. Blessed with grades of 3-7% copper, the operations in Shaba did not need sophisticated metallurgy to hit the economic sweet spot.

The mines at Kakanda and Kambove went into production in the 1940s, when Union Miniere’s annual copper production was around 150,000 tonnes. Sulphide ores were concentrated in circuits that were tuned for high-grade chalcocite ores; oxide and carbonate mineralization, if it made the grade, was smelted directly. The result was that plenty of metal was not recovered.

Drastic change

The Kambove-Kakanda project is an example of how the use of solvent extraction-electrowinning (SX-EW) to recover copper (and cobalt) has brought about a drastic change in the economics of metal production. Much of the metal in the “oxide” mineralization — actually a catchall term for the mixture of oxides, carbonates and silicates that occurs above the permanent water table — is easily leached with dilute sulphuric acid. Then metal in the leachate can be back-extracted into an organic solution, and subsequently stripped with concentrated sulphuric acid for electrocemical recovery.

Panorama’s current plan is to start with a combined leach and electrowinning plant to treat the higher-grade clay and dolomitic oxide tailings at Kambove.

Once the project has some cash flow, a second leach plant could be built at Kakanda, with the leachate pumped to Kambove for the SX-EW stages.

Getting the tailings to the leach pad presents little or no problem.

Hydraulic monitor mining, at a cost of less than US$1 per tonne, will allow the silty sand tailings to be pumped in a slurry to a dewatering circuit at the plant. The dewatered tailings can then be leached.

Feasibility studies, now under way, will determine whether SX-EW or a cobalt-carbonate process will be more economic. Estimates of the capital costs to get the operation up and running range from US$103 million for a single cobalt-carbonate plant to US$118 million for one SX-EW plant (and US$190 million for two).

Panorama is not expecting cobalt to stay at US$20 per lb., and prefeasibility studies assumed a price of US97c per lb. for copper and US$9-12 per lb. for cobalt. Low operating costs, estimated at US55c per lb. copper, give the project plenty of breathing room if metal markets get tight. As Panorama director Terry O’Kane says, “The copper pays for the operation, and the cobalt is the gravy.”