The 2014 technical report on Tenke Fungurume in Katanga describes a 14,000 t/d plant expanded in 2013, with SAG milling, acid leaching with sulphur dioxide, CCD washing, SX-EW and a cobalt purification train.
The Tenke Fungurume copper-cobalt mine lies about 175 km northwest of Lubumbashi in Katanga Province, Democratic Republic of Congo, on concessions covering 1,437 km2. Tenke Fungurume Mining S.A.R.L. (TFM) holds the deposits. At the time of the report, Freeport-McMoRan indirectly owned 56% and operated the mine, Lundin Mining held 24% and the state company Gécamines held a 20% carried interest. The technical report, dated July 21, 2014, updates resources and reserves at December 2013 for Lundin. Commercial production began in 2009 at a capital cost of about US$1.8 billion. A Phase 2 expansion, substantially completed in 2013, raised nameplate capacity to 14,000 t/d of ore and 195,000 t/a of copper cathode. In 2013 the plant averaged about 14,900 t/d and produced about 210,000 t of cathode.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Commercial production | 2009 | Not applicable | First cathode March 2009 |
| Nameplate throughput | 14,000 | dry t/d | After Phase 2 |
| 2013 throughput | About 14,900 | t/d | Above nameplate |
| Nameplate cathode output | 195,000 | t/a | Plant |
| 2013 cathode production | About 210,000 | t | LME Grade A |
| Tankhouse nameplate | 270,000 | t/a | After 100% extension |
| Added EW cells | 280 | Not applicable | Phase 2 tankhouse extension |
| Leach tanks | 5 | Not applicable | SO2, acid and raffinate |
| CCD stages | 5 | Not applicable | Washing of leached solids |
| SX stages | 6 extraction / 4 stripping | Not applicable | Four HG, two LG |
| Mineral reserve | 113.4 | Mt | 3.34% Cu, 0.36% Co |
| Low grade stockpiles | 30.7 | Mt | 1.25% Cu, 0.33% Co |
| Capital cost | About 1.8 | US$ billion | Initial project |
Overview
The Tenke Fungurume plant is built for oxide copper-cobalt ore. The ore is ground in a single-stage SAG mill and leached with sulphuric acid, sulphur dioxide and recycled raffinate. Copper and cobalt both dissolve. Thickening and counter-current decantation (CCD) separate the solution from the solids and produce high-grade and low-grade pregnant leach solution (PLS). Solvent extraction and electrowinning (SX-EW) recover the copper as cathode. The low-grade raffinate then passes through iron, aluminium and manganese removal, copper precipitation and two-stage cobalt precipitation to produce cobalt hydroxide. Washed solids and residues are neutralized with lime and pumped to a lined tailings facility.
Phelps Dodge approved construction before the end of 2006, and Freeport-McMoRan acquired Phelps Dodge in March 2007. The first cathode was stripped in March 2009 and the first cobalt hydroxide was produced in May.
Key Process Stages
Grinding
Haul trucks deliver ore to the ROM pad, and front-end loaders feed a blend to a mobile crusher. The crusher feeds a ROM bin, and a conveyor carries the ore to the single-stage SAG mill, which runs in closed circuit with hydrocyclones. Phase 2 added the mobile crusher ahead of the SAG feeder, faster and stronger braking on the SAG feed conveyor, and a pebble crusher to reach the target grind. A ball mill was planned for 2017 to handle harder ore at depth.
Leaching and CCD
The ground slurry is thickened and pumped to the first of five leach tanks, where it is mixed with sulphur dioxide, sulphuric acid and raffinate. After leaching, the slurry is thickened. The overflow is clarified, cooled and clarified again to remove colloidal silica and solids, and it becomes high-grade PLS. The thickener underflow passes five CCD stages to wash out the dissolved metals. Overflow from CCD 1 is clarified to give low-grade PLS. Phase 2 added desanding pumps, upgrades to the leach feed and discharge thickeners and CCD underflow pumps, and new raked clarifiers on both PLS streams.
Solvent extraction and electrowinning
One SX circuit has six extraction stages, four for high-grade and two for low-grade PLS, and a shared four-stage strip. An organic extractant loads the copper, and stripping produces strong electrolyte, which is filtered to remove entrained organic before electrowinning. Phase 2 added four mixer-settlers, three tricanters, a clay filter and a crud filter. It also doubled the tankhouse with 280 more cells, two rectiformers, two high-speed stripping machines, four electrolyte filters, a cooling tower and three cranes. Cathodes are stripped from stainless steel blanks by semi-automatic and fully automatic machines. High-grade raffinate and electrolyte bleed return to the leach to cut fresh acid use.
Iron, aluminium and manganese removal
Low-grade raffinate is neutralized with limestone while sulphur dioxide and air are sparged into agitated tanks. Under these oxidizing conditions, iron, aluminium and manganese precipitate. The slurry is thickened and filtered to recover the cobalt-bearing solution. The filter cake, mainly gypsum and iron and aluminium hydroxides, is repulped and sent to neutralization.
Copper and cobalt precipitation
Milk of lime precipitates the remaining copper, with sulphur dioxide and air sparged to remove remaining manganese. The copper solids return to the leach. Milk of magnesia then precipitates cobalt hydroxide in a first stage, and lime finishes the job in a second stage, which improves purity and cuts magnesia use. First stage cobalt hydroxide is filtered and bagged wet, or flash dried and bagged, for export. Second stage solids return to the iron removal circuit, and the cobalt-free solution serves as CCD wash.
Neutralization
CCD 5 underflow, excess wash solution and iron residue are neutralized with slaked lime, which also precipitates magnesium and trace heavy metals. The neutralized slurry goes to the lined tailings storage facility. Phase 2 added a third neutralization tailings pump.
Additional Interesting Data and Summary
The deposits include oxide, mixed oxide-sulphide and sulphide zones. Beyond the reserve, low grade work-in-progress stockpiles held 30.7 Mt at 1.25% copper and 0.33% cobalt. The report says higher output would depend on ore grades, debottlenecking the front end, and possible heap leaching of low grade ores, and that optimisation studies were continuing.
Because of Gécamines' carried interest, Freeport-McMoRan and Lundin funded capital in a 70 to 30 ratio. The initial capital cost was described as the largest foreign direct investment in the DRC at the time.
Key Processes
- Mobile crushing and single-stage SAG milling with pebble crushing
- Acid leaching with sulphur dioxide and recycled raffinate
- Thickening, clarification and five-stage counter-current decantation
- Solvent extraction with high-grade and low-grade circuits
- Copper electrowinning to LME Grade A cathode
- Iron, aluminium and manganese removal with limestone, SO2 and air
- Copper precipitation with lime and two-stage cobalt hydroxide precipitation
- Lime neutralization and lined tailings storage
Source: Technical Report – Resource and Reserve Update for the Tenke Fungurume Mine, Katanga Province, Democratic Republic of Congo, July 21, 2014.
Project website: Tenke Fungurume Mine
