This report details the proposed refurbishment and operation of the Kombat processing plant to treat open pit run-of-mine material at a capacity of 30,000 tonnes per month.
Report context
The Kombat plant, which has a capacity of 30,000 tonnes per month (30 ktpm), will be refurbished to treat open pit run-of-mine (RoM) material. The plant consists of three-stage crushing and screening, rod and ball milling, flotation, concentrate thickening and filtering circuits. Historically, the plant was capable of producing separate copper and lead concentrates; however, only the copper concentrate section will be refurbished and no lead concentrate will be produced. The plant will produce a copper concentrate of 22% Cu, which will be trucked and exported via the port of Walvis Bay. Flotation tailings will be deposited on a newly constructed tailings storage facility (TSF) adjacent to the processing plant.
Processing route
Primary Crushing
RoM material will be delivered over a static grizzly screen by tipper trucks. RoM material will also be stockpiled and fed into the plant by front end loaders as required. The static screen underflow will discharge into a bin and then onto a vibrating grizzly screen. The vibrating grizzly screen undersize (-100 mm material) will gravitate onto a conveyor, while the oversize (+100 mm material) will discharge into the primary jaw crusher. The jaw crusher product will combine with the grizzly underflow and then be conveyed into a 100-tonne silo.
Secondary Crushing
The silo will ensure a consistent feed to the downstream screening and secondary crushing circuit. The silo product will be delivered onto a vibrating grizzly screen. The grizzly undersize (-50 mm) will discharge onto the wet double deck screen. The grizzly oversize material (+50 mm) will discharge onto conveyors before the dry double deck screen.
The wet screen oversize (+15-50 mm) will be conveyed and combine with the grizzly oversize. The wet screen middlings (+2-15 mm) will be conveyed to the mill silos. The wet screen underflow (-2 mm) will be pumped to the fines thickener.
The dry double deck screen oversize (+35 mm) will be crushed in a cone crusher with its product conveyed back to the dry screen. The dry deck middlings (+15-35 mm) will be conveyed into the short head cone crusher. The short head cone crusher product will combine with the dry deck underflow (-15 mm) and the wet screen middlings (+2-15 mm) onto the mill silos together with wet screen middlings.
Milling and Classification
The three mill feed silos feed three rod mills. The silos will ensure that the total rod mill circuit operates at approximately 48 tonnes per hour (16 to 17 tph per rod mill) to achieve a throughput of 1,071 tonnes per day.
Silos 1 and 2 will discharge onto a conveyor and split between rod mill 2 and 3. Silo 3 will discharge onto a conveyor and feed into rod mill 1. The rod mills will discharge into a common sump with the sump contents pumped to one of the two primary cyclones.
The wet screen underflow (from the secondary crushing circuit) will be pumped into the 30-foot fines thickener. The thickener underflow will be pumped into the rod mill discharge sump.
The primary cyclone overflow will gravitate into the regrind mill sump, while the underflow will gravitate and split into the two ball mills. The ball mill discharge will be fluidised with water and gravitate into the rod mill discharge sump.
The regrind mill sump contents will be pumped into one of two secondary cyclones. The secondary cyclone underflow will gravitate into the regrind mill feed tank and then be pumped into the regrind mill. The regrind mill product will be fluidised and gravitate into the regrind mill sump. The secondary cyclone overflow will gravitate to the float circuit feed conditioning tank.
Cyclone classification will be controlled by adjusting the cyclone feed flow rate with the discharge sump pump variable speed drive (VSD), while the feed density will be controlled by manipulating the sump dilution water. The milling circuit will be controlled to ensure a final grind of 80% passing 90 µm and a final cyclone overflow with at least 30% solids. The final slurry density will be adjusted in the float feed conditioning tank.
Flotation
The flotation circuit will receive new cells as part of the refurbishment project. The historic flotation process flow will be modified and will consist of roughers, scavengers, cleaners and recleaner circuits. The float circuit will produce a single copper concentrate at a target grade of 22% Cu.
Mill circuit product will gravitate into the conditioning tank where the pH will be modified to 10 and flotation reagents will also be added. The conditioning tank will serve as a buffer prior to the rougher float circuit. The conditioning tank contents will be pumped into the primary rougher at a consistent flow rate to ensure stable float conditions.
The primary rougher concentrate will gravitate into a concentrate box then be pumped to the cleaning circuit feed tank. The rougher tail will discharge into the rougher tails box and then be pumped to the scavenger circuit. The scavenger concentrate will gravitate into concentrate and then be pumped to the cleaning circuit feed tank where it will combine with the rougher concentrate.
The cleaning circuit concentrate will gravitate into a concentrate box and then be pumped to the recleaning circuit feed box. The recleaner concentrate will gravitate into a concentrate box and then be pumped to the concentrate thickener circuit prior to filtration.
Cleaner circuit tails will be recycled back into the rougher circuit. The recleaner tails will be pumped into the cleaner feed box. The scavenger tails will be pumped to the tails thickener.
Thickening and Filtration
Flotation tails will be pumped into the 70-foot tails thickener. The underflow will be pumped into the final tails pump box and then to the TSF.
Flotation final concentrate will be pumped into one of the two 40-foot concentrate thickeners. The underflow will be pumped into a concentrate holding tank. The thickener and the holding tank will serve as buffer capacity prior to the filter press.
The overflow water from the thickeners will gravitate into the first process water tank.
The concentrate holding tank contents will be pumped into the filter press. The filter press will be installed in the filter house. The filter cake will discharge directly into trucks below the filter house.
The filtrate will gravitate into a filtrate tank and then be pumped into the process water tank.
Tailings Storage Facility
The tailings storage facility was designed to accommodate tonnes for the total life of mine. The TSF construction was split into two phases to phase the expansion of the tailings dam over the early life of mine. The phases will be built in succeeding years, with Phase 1 to be completed prior to start of production. Phase 2 will be built in the next year to accommodate further deposition.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant capacity | 30 ktpm | Proposed design |
| Throughput target | 1,071 tpd | Proposed design |
| Rod mill circuit feed rate | ~48 tph (16-17 tph per mill) | Proposed design |
| Final grind target | 80% passing 90 µm | Proposed design |
| Cyclone overflow solids target | At least 30% solids | Proposed design |
| Copper concentrate grade target | 22% Cu | Proposed design |
| Total installed power | 2,500 kW | Proposed design basis |
| Total power consumption | 1,309,000 kWh/month | Proposed at 30 ktpm processing |
| Power unit cost | 1.67 NAD/kWh | Estimated |
| Monthly power cost | 2,186,030 NAD/month | Calculated |
| Specific power cost | 72.9 NAD/t | Calculated |
| Peak water requirement (dry season) | 30 m³ per hour | Estimated at 30 ktpm throughput |
| Sodium Carbonate consumption | 1.022 kg/t RoM | Reported reagent consumption |
| Sodium Sulphide consumption | 1.111 kg/t RoM | Reported reagent consumption |
| Amyl X consumption | 0.142 kg/t RoM | Reported reagent consumption |
| Butyl N consumption | 0.060 kg/t RoM | Reported reagent consumption |
| Frother consumption | 0.057 kg/t RoM | Reported reagent consumption |
| Total reagent cost | 37.2 NAD/t RoM | Calculated from reported unit costs |
Project website: https://www.businesswire.com/news/home/20251223050934/en/Trigon-Metals-Announces-Closing-of-Sale-of-Kombat-Mine-Interest-to-Horizon-Corporation-Limited
Project website: https://ca.finance.yahoo.com/quote/TM.V/
Technical qualifications
The report states that the plant consists of industry standard processing equipment and well-understood processing recovery methods and is deemed to be appropriate to treat the targeted open pit material. The proposed processing route is based on the refurbishment of the existing Kombat plant and modification of the historic flotation process flow. The report notes that an onsite laboratory will be equipped and operated by a contractor to process both plant and mining samples. Water for make-up will be sourced from underground dewatering activities.
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Source: Trigon Metals Inc. NI 43-101 Technical Report on the Kombat Project, Namibia, Item 17 – Recovery Methods.
