The February 2024 feasibility study describes a 17,600 tpd copper-gold-silver flotation concentrator and a separate 2,400 tpd gravity wash plant for saprolite ore and historical tailings, with metallurgical design based on testwork performed during the PFS and FS phases.
Report context
The process design for the feasibility study (FS) was developed from metallurgical testwork performed during the pre-feasibility study (PFS) and FS phases. Testwork was conducted by Blue Coast Research between the PFS and FS study phases and in parallel with the FS in 2023. Historical PFS testwork included mineralogical work conducted by Actlabs, SGS Canada, and SGS Lakefield, while grindability work was performed by Blue Coast Research and flotation testwork was completed at SGS Canada.
The metallurgical testwork program used 81 discrete geometallurgical variability samples selected from the 2022/2023 drilling program to represent the spatial distribution, grade, and rock type of the deposit. Samples underwent head analysis, mineralogical characterization by QEMSCAN, and rougher flotation kinetic testing. Composites were formed into three master composites, five comminution composites, six metallurgical composites, and one bulk composite.
Processing route
Fresh and transition ore processing
The concentrator is designed for a throughput of 17,600 tpd (6.4 Mtpa) with 92% plant utilization. ROM ore is crushed in a single jaw crusher. The grinding circuit uses a SAG mill in open circuit with a pebble crusher arrangement and a ball mill in closed circuit with hydrocyclones. Hydrocyclone overflow at a target grind size P₈₀ of 150 µm reports to the rougher flotation circuit.
Primary crushing reduces ore from an F₈₀ of 300 mm to a P₈₀ of 150 mm. The jaw crusher has dimensions of 1200 mm x 1600 mm, is installed with 250 kW, and crushes ore from a top size of 600 mm down to a P₈₀ of 150 mm. A scalping screen with a grizzly handles feed, with oversize reporting to the jaw crusher. A remote-operated rock breaker is installed at the jaw crusher feed point. The coarse ore stockpile provides 12 hours of live buffer storage (8,000 t). Three apron feeders, with two operating and one standby, control feed to the SAG mill conveyor.
The SAG mill has dimensions of 9.15 m diameter by 5.5 m EGL, with 8.5 MW installed power through a single pinion drive and VFD arrangement. The pebble crusher is a conventional cone crusher with a closed side setting of 16 mm, reducing SAG mill discharge pebbles to a P₈₀ of 14 mm, rated at 320 dry t/h. The ball mill measures 6.55 m diameter by 10.37 m EGL with 8.5 MW installed power. A trunnion magnet separates ball scats and slivers from ball mill discharge.
Flotation circuit
Feed reports to rougher flotation at a grind P₈₀ of 150 µm and pH of 10.5. The rougher circuit consists of six 200 m³ mechanical tank cells in series with 187 kW agitators, providing 30 minutes total residence time. Reagents include sodium hexametaphosphate (Calgon), MIBC, and potassium amyl xanthate (PAX), added to the rougher feed box and rougher cell number 4.
Rougher concentrate reports to a regrind stage closed with hydrocyclones. A 1,500 kW vertical mill (CSM 1500) grinds to a P₈₀ of 30 µm prior to first cleaning. The cleaner scalper is a single Jameson Cell model B4500/12, with Calgon, PAX, and MIBC added. Concentrate from the cleaner scalper reports to the final concentrate thickener, while tailings are partially recycled to maintain constant feed, with the remaining tailings overflowing to the cleaner scavenger stage.
The cleaner scavenger is also a single Jameson Cell model B4500/12, fed by cleaner scalper tailings, recleaner tailings, and its own recirculation. Cleaner scavenger concentrate reports to the recleaner stage. The recleaner is a single Jameson Cell model E1732/4, producing final concentrate that reports to the concentrate thickener. Recleaner tailings are recycled to the cleaner scavenger.
A gravity concentrator treats cleaner scavenger tailings to remove remaining gold and silver before final tailings thickening. The dedicated Au-Ag concentrate is combined with the first stage gravity concentrate and bagged separately for sale apart from the copper concentrate.
Concentrate and tailings handling
Final concentrate from the cleaner scavenger and recleaner feeds a 10 m diameter high-rate concentrate thickener at 25% solids w/w, thickened to 60% solids w/w underflow using anionic flocculant. Thickened concentrate is pumped to a concentrate pressure filter, increasing solids content to a target of 92% w/w. Filter discharge is conveyed to an enclosed stockpile for storage before truck transport to a port facility and ocean vessels. Thickener overflow and filter filtrate are recycled to the process.
Rougher flotation tails and gravity concentrator number 2 tails are pumped to a high-rate tailings thickener targeting 55% w/w underflow solids density with flocculant addition. Thickener overflow combines with concentrate thickener overflow and reports to the process water storage tank.
Gravity wash plant
The stand-alone gravity wash plant processes saprolite ore at 2,400 tpd and historical tailings at 1,200 tpd, recovering a high-grade gold-silver concentrate bagged on site. Saprolite feed is reclaimed by front-end loader into a feed hopper through a static grizzly, then washed in a rotary scrubber with water jets. Oversize material above 10 mm is conveyed to a stockpile. Material between 3 mm and 10 mm reports to a coarse gravity module with a sluice and jig cleaner, producing bagged concentrate. Material below 3 mm is pumped to a batch centrifugal gravity concentrator producing high-grade Au-Ag concentrate bagged in large filter bags.
The gravity wash plant includes a regrind mill and classification step. Regrind mill feed includes sluice, jig, and gravity concentrator tailings. Hydrocyclone overflow reports to the main tailings management facility, while underflow is recycled to the gravity concentrator for further recovery.
Process water
Process water is stored in a 1,400 m³ tank. Primary supply comes from concentrate and tailings thickener overflows at 1,202 m³/h. A secondary source is the water management pond collecting water from the waste management facility. Water is delivered by pumps mounted on a reclaim barge, with excess water discharged to the San Pedro River based on water simulation results. Process water is used for grinding, regrinding, gravity concentration, flotation launders, fire water, and concentrate filter wash water. Fresh water is supplied by a 2,700 m³ fresh and fire water head tank receiving runoff from Collection Pond 4, with a standpipe maintaining at least 90 minutes of fire water supply. Potable and sewage treatment plants are included.
Key reported parameters
| Parameter | Unit | Value |
|---|---|---|
| Plant design capacity (fresh/transition) | tpd | 17,600 |
| Throughput | Mtpa | 6.4 |
| Plant utilization | % | 92.0 |
| ROM feed F₈₀ | mm | 300 |
| Primary crusher type | Jaw, 1200 mm x 1600 mm | |
| Primary crusher installed power | kW | 250 |
| Crushing work index | kWh/t | 13.6 |
| Abrasion index | g | 0.066 |
| SAG mill dimensions | m | 9.15 dia. x 5.5 EGL |
| SAG mill installed power | MW | 8.5 |
| Pebble crusher type | Cone | |
| Pebble crusher installed power | kW | 375 |
| Pebble crusher product P₈₀ | mm | 14 |
| Ball mill dimensions | m | 6.55 dia. x 10.37 EGL |
| Ball mill installed power | MW | 8.5 |
| Ball mill work index (85th percentile) | kWh/t | 20.4 |
| Regrind mill type | Vertical mill | |
| Regrind mill installed power | kW | 1,500 |
| Primary grind size P₈₀ | µm | 150 |
| Regrind grind size P₈₀ | µm | 30 |
| Rougher flotation residence time | min | 30 |
| Rougher cells | 6 x 200 m³ mechanical tank | |
| Cleaner scalper | Jameson Cell B4500/12 | |
| Cleaner scavenger | Jameson Cell B4500/12 | |
| Recleaner | Jameson Cell E1732/4 | |
| Concentrate thickener | High rate, 10 m diameter | |
| Concentrate filter | Vertical multi-plate pressure | |
| Final concentrate moisture | % | 8 |
| Tailings thickener | High rate, 45 m diameter | |
| Tailings thickener underflow density | % w/w | 55 |
| Concentrate mass pull | % of feed | 2.0 |
| Final flotation concentrate mass pull | % | 2.0 |
| Combined gravity mass pull | % nominal feed | 0.03 |
| Gravity concentrator 1 nominal / design | t/h | 614 / 675 |
| Gravity concentrator 2 nominal / design | t/h | 59 / 68 |
| Gravity wash plant capacity, saprolite | tpd | 2,400 |
| Gravity wash plant capacity, historical tails | tpd | 1,200 |
| Saprolite specific gravity | t/m³ | 2.78 |
| Historical tails specific gravity | t/m³ | 2.84 |
| Saprolite feed granulometry F₈₀ | µm | 160 |
| Historical tails feed granulometry F₈₀ | µm | 233 |
| Saprolite ball mill work index | kWh/t | 3.05 |
| Historical tails ball mill work index | kWh/t | 6 |
| Saprolite regrind mill grind size P₈₀ | µm | 45 |
| Historical tails regrind mill grind size P₈₀ | µm | 90 |
| Gravity wash plant mass pull | % of feed | 0.08 (0.05 to 0.1) |
| Gold recovery, saprolite | % | 36 |
| Silver recovery, saprolite | % | 3 |
| Gold recovery, historical tails | % | 37 |
| Silver recovery, historical tails | % | 3.5 |
Project website: https://ivanhoeelectric.com/news/ivanhoe-electric-to-receive-58pt4-million-cash-distribution-from-cordoba-minerals-corp/
Reagent consumption
| Reagent | Consumption per tonne of ore (g/t) | Annual consumption (tpa) |
|---|---|---|
| Lime | 1,400 | 8,994 |
| Calgon | 15 | 96.4 |
| PAX | 13 | 83.5 |
| MIBC | 26 | 167 |
| Flocculant for concentrate thickener | 20 | 2.7 |
| Flocculant for tailings thickener | 50 | 321.2 |
Technical qualifications
The study notes that final optimization of the gravity wash plant flowsheet will be performed during detailed engineering. Testwork was conducted on composite samples representing the deposit distribution. The process design was based on metallurgical testwork performed during the PFS and FS phases, with variability samples selected to represent spatial distribution, grade, and rock type. The report states that water simulation results showed safe discharge to the environment with constituent concentrations well below regulations.
Source: NI 43-101 Technical Report Feasibility Study, Alacran Project, February 2024, DRA Ref.: J6769-0000-STU-REP-0001-Final, Sections 17.1, 17.2, 17.2.9.2, 17.3, and 17.4.
