The Manono Lithium Tailings Project is designed to process material from the K, G, and I tailings dumps using a combination of dense media separation and flotation to produce a lithium spodumene concentrate.
Report context
This technical report summarizes the preliminary economic assessment (PEA) for the Manono Lithium Tailings Project, located in Manono, Democratic Republic of Congo, with an effective report date of 19 October 2023. The processing plant is designed to treat tailings recovered from the K, G, and I tailings dumps to produce a lithium oxide (Li₂O) concentrate. The process flowsheet and preliminary mass balance are based on metallurgical testwork conducted during the study, as described in Chapter 13 of the report.
Processing route
Process design criteria
The Processing Plant is designed to process tailings recovered from the K, G, and I tailings dumps to produce Li₂O concentrate. The process flowsheet and preliminary mass balance are based on metallurgical testwork conducted during the study.
Key process design criteria include a run-of-mine (ROM) feed to the process plant of 216 dry tonnes per hour, comprising 134.2 t/h from the K-dump, 61.0 t/h from the G-dump, and 20.8 t/h from the I-dump. The crusher feed is rated at 14.6 t/h, the DMS plant feed at 135.9 t/h, and the flotation plant feed at 97.9 t/h.
Crushing and screening
The 15,000-tonne process plant stockpile is reclaimed by a front-end loader and fed onto a belt conveyor that transports the material onto a vibrating crusher sizing screen. A 5 mm screen deck diverts oversized material into a double roll crusher, which returns the material onto the crusher feed conveyor. Spray water is used on this screen deck to push finer material to the undersize. Screen undersize flows onto a vibrating wet sizing screen with a 500 µm deck. The wet sizing screen diverts oversize material into the DMS plant feed tank, while undersize is directed into the wet grinding plant feed pump box.
Dense media separation plant
The wet screen oversize material is combined with ferrosilicon (FeSi) media to increase the specific gravity of the slurry to 2.65 t/m³ before entering the primary DMS cyclones. Primary DMS cyclone overflow (floats) is dewatered through a screen to 15% moisture and transported by a series of grasshopper conveyors to the Tailings Storage Facility (TSF). Primary cyclone underflow (sinks) is combined with additional FeSi to increase the specific gravity to 2.85 t/m³ before entering the secondary DMS cyclones. Overflow from the secondary cyclone (middlings) is pumped to the wet grinding plant. Secondary cyclone underflow is transferred to a dewatering centrifuge. FeSi media is recovered from primary and secondary DMS cyclones through drain and rinse screens and magnetic separators.
Wet grinding
Wet screen undersize and DMS middlings are pumped to a ball mill for wet grinding. The product slurry is pumped to a hydrocyclone with a cut point of 300 µm. Cyclone overflow (−300 µm) is fed to the flotation plant, and the underflow (+300 µm) is recycled back to the ball mill.
Flotation plant
Ball mill cyclone overflow is pumped to a high-intensity scrubber followed by a desliming cyclone and a magnetic separator. The iron-deficient slurry is then pumped into two stages of mica reverse flotation cells. The floated mica is pumped to the tailings thickener, with the remaining slurry pumped into a dewatering cyclone.
The mica-deficient, dewatered slurry passes through a high-density scrubber and a desliming cyclone before being pumped into four stages of lithium spodumene flotation cells. Tailings from the rougher and scavenger cells are pumped to the tailings thickener, while concentrate is pumped to the cleaner cells. Concentrate from the first cleaner stage is pumped into the second-stage cleaner to produce a final product concentrate that is pumped to the dewatering centrifuge. Tailings from the cleaner cells are pumped to the tailings thickener.
Product dewatering and bagging
Spodumene concentrate from the DMS and flotation plants is pumped into dedicated screen bowl centrifuges for final dewatering, targeting 5% moisture. The dewatered concentrate is transferred into dedicated storage bins to feed the product bagging plants. Each concentrate type has a dedicated bagging plant that includes automatically filling 1-tonne bulk bags, bag labeling, and transporting the filled bags on an accumulating conveyor for forklift handling. The 1-tonne bulk bags are removed from the accumulating conveyors by forklifts for storage on wooden pallets in a covered area at the process plant. Forklifts maneuver the palletized bags onto transport trucks that deliver the bags to a warehouse location in Lubumbashi. From Lubumbashi, the palletized bags are loaded onto 26-tonne capacity trucks for transport to the port of Dar es Salaam, Tanzania.
Tailings dewatering
A single high-rate thickener collects various tailings streams generated throughout the process plant. These streams consist of effluent from the DMS plant, fines in the desliming cyclone overflow, overflow from the dewatering cyclones, magnetic separation tailings, mica reverse flotation concentrate, and spodumene flotation tailings. The solids present in the feed streams settle to the bottom of the thickener, and water is recovered through the overflow weir. The recovered water is pumped to the process water pond. The underflow slurry is pumped to the TSF at 55% moisture.
Reagents
The DMS Plant uses ferrosilicon (FeSi) as the densifying agent. The FeSi is stored in waterproof steel drums under a roof at the process plant. The flotation plant requires several reagent types, including frothers, amine collectors, and sodium-based compounds as regulators, stored in plastic totes under a roof at the process plant. A flocculant is added to the tailings thickener to assist in solids settling and is stored in plastic totes under a roof at the process plant, near the thickener.
Key reported parameters
| Parameter | Unit | Value | Basis |
|---|---|---|---|
| ROM Feed to Process Plant | t/h | 216 | Design |
| K-dump feed | t/h | 134.2 | Design |
| G-dump feed | t/h | 61.0 | Design |
| I-dump feed | t/h | 20.8 | Design |
| Crusher feed | t/h | 14.6 | Design |
| DMS Plant feed | t/h | 135.9 | Design |
| Flotation Plant feed | t/h | 97.9 | Design |
| DMS concentrate Li₂O grade , laboratory | wt% | 6.0 | Testwork |
| DMS concentrate Li₂O grade , commercial | wt% | 5.5 | Commercial design |
| DMS lithium recovery , laboratory | % | 51.5 | Testwork |
| DMS lithium recovery , commercial | % | 45 | Commercial design |
| DMS tailings Li₂O grade , laboratory | wt% | 0.37 | Testwork |
| DMS tailings Li₂O grade , commercial | wt% | 0.42 | Commercial design |
| Flotation concentrate Li₂O grade , laboratory | wt% | 6.0 | Testwork |
| Flotation concentrate Li₂O grade , commercial | wt% | 5.5 | Commercial design |
| Flotation lithium recovery , laboratory | % | 67.1 | Testwork |
| Flotation lithium recovery , commercial | % | 55.0 | Commercial design |
| Flotation tailings Li₂O grade , laboratory | wt% | 0.25 | Testwork |
| Flotation tailings Li₂O grade , commercial | wt% | 0.34 | Commercial design |
| Annual DMS and flotation production | tonnes/year | 112,167 | Mass balance |
| Total production over six years | tonnes | 673,003 | Mass balance |
| Annual plant feed , K dump | tonnes/year | 1,016,667 | Mass balance |
| Annual plant feed , Gc dump | tonnes/year | 133,833 | Mass balance |
| Annual plant feed , I dump | tonnes/year | 111,667 | Mass balance |
| Annual plant feed , Gf dump | tonnes/year | 0 | Excluded |
| DMS plant feed (coarse +0.5 mm) | tonnes/year | 793,724 | Mass balance |
| Flotation plant feed (fines −0.5 mm) | tonnes/year | 468,443 | Mass balance |
| DMS middlings to flotation | tonnes/year | 93,515 | Mass balance |
| Concentrate moisture target | % | 5 | Design |
| DMS media specific gravity , primary | t/m³ | 2.65 | Design |
| DMS media specific gravity , secondary | t/m³ | 2.85 | Design |
| Hydrocyclone cut point | µm | 300 | Design |
| Tailings underflow moisture | % | 55 | Design |
| Bag capacity | tonne | 1 | Design |
| Transport truck capacity | tonnes | 26 | Design |
Project website: https://tantalexlithium.com/manono-tailings/
Technical qualifications
The feed grade used as input into the mass balance was based on the mineral resource estimate with an effective date of 23 August 2023. Testwork results for K-dump and Gc-dump were applied to I-dump, as I-dump has similar granulometry. Material from the Indicated Gfs-dump was excluded from feed due to its very low head grade. Testwork results were downgraded to account for process inefficiencies anticipated to occur in a commercial plant, with these corrections summarized in Table 17-2 of the report and included in the mass balance.
Source: NI 43-101 Technical Report Summarizing the PEA for the Manono Lithium Tailings Project, Manono, Democratic Republic of Congo, prepared for Tantalex Lithium Resources, 19 October 2023, Chapter 17, Recovery Methods.
