The proposed processing plant is designed for a capacity of 136,000 t/d, employing HPGR crushing, ball milling, bulk and selective flotation, and dry stacked filtered tailings.
Report context
This technical report, dated 2022, details the recovery methods for the Vizcachitas Project. The concentrator is designed for a capacity of 136,000 t/d and is located in two areas within the Rocín River valley: the crushing and grinding circuits on a platform of compacted waste rock, and the wet area down the valley on a natural plateau next to the access road on the east side of the valley.
Processing route
Crushing and grinding
The run of mine material is fed to a primary crusher (MK60-110E) where it is reduced to 7 inches, and then to three secondary cone crushers (2,500 HP) in open circuit. The crushed product of 2 inches is stored in a surge bin that feeds the tertiary crushing circuit that includes two HRC3000 high pressure grinding roll (HPGR) crushers arranged in a closed circuit with banana screens.
The undersize from the crushing plant (P80 < 3.5 mm) is fed to two 23 MW ball mills arranged in a reverse closed circuit with hydrocyclones to achieve a P80 of 240 μm. The overflow from the hydrocyclones is thickened to 50% solids %wt and then transported via a concrete launder to the flotation area.
Flotation
The flotation circuit has two stages: a Cu-Mo bulk flotation and a Cu-Mo selective flotation. Both circuits use mechanically agitated tanks and column cells to produce concentrates. The bulk flotation includes a rougher flotation stage of 24 TankCell e500 cells arranged in two parallel lines operating at a pH near 7. The rougher concentrate is reduced to P80 = 25 μm in three HIG mills (HIG 5000) and then fed to three 5 m diameter x 13 m cleaner columns operating at a pH of 12. The selective Cu-Mo flotation stage includes rougher flotation and several cleaner stages in counter-current arrangement, with sulphuric acid and sodium hydrosulphide added to maintain the pH around 9 and the pulp potential near -450 mV.
Concentrate handling
The copper concentrate is filtered and then loaded and stored in Rotainers to be hauled by trucks to the port of Ventanas. The molybdenum concentrate is filtered and stored in bags to be hauled by truck to the port of Ventanas or to alternative destinations agreed with buyers. The concentrator produces clean concentrates of approximately 24% Cu.
Tailings dewatering and disposal
The tailings from flotation are classified using hydrocyclones. The coarse fraction is fed to belt filters and the fine fraction is thickened and then filtered in pressure filters. The filtered cake contains an average moisture of 15% and is disposed of in 2 m layers co-mingled with mine waste rock, in the bottom and across the valley to shape the dry stacked filtered tailings deposit.
Water supply and management
The concentrator water supply will be supplied by a third party (Desala Petorca SpA) from a desalination plant located in Papudo to a pump station located near Cabildo. The water is pumped to Vizcachitas in a 26 inch diameter, 90.6 km long pipeline. Three 49,000 m³ water storage ponds are included: fresh water storage pond #1, process water storage pond #2, and recovered water storage pond #3.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Concentrator capacity | 136,000 | t/d | Design |
| Primary crusher product size | P80 7 in | inches | Design |
| Secondary crusher product size | 100% -2 in | inches | Design |
| HPGR product size | P80 < 3.5 mm | mm | Design |
| Ball mill product size | P80 240 μm | μm | Design |
| Ball mill power (each) | 23 | MW | Design |
| Flotation feed density | 50 | % solids | Design |
| Rougher concentrate regrind size | P80 25 μm | μm | Design |
| Filtered tailings moisture | 15 | % | Design |
| Copper concentrate grade | ~24 | % Cu | Design |
| Make-up water consumption | 271 (max 300) | L/s | Design |
| Power consumption | 16.6 | kWh/t | Design |
| Total installed power | 139 | MW | Design |
| Testwork source (main) | SGS, 2021 | , | Testwork |
| Crushing and grinding equipment selection | Metso:Outotec | , | Based on testwork and simulations |
| Tailings filtration sizing | Takraf | , | Based on laboratory and pilot testwork |
| Ball mill sizing methodology | Bond methodology with phantom cyclone adjustment | , | Calculations by Metso:Outotec |
| Mass balance simulation | JKSimMet 6.3 | , | Nominal design values |
Project website: https://losandescopper.com/projects/overview/
Project website: https://losandescopper.com/projects/history/
Technical qualifications
The plant design and the equipment selection are backed up by bench-scale testwork and some pilot plant testwork carried out using representative composites of the first years of operation. The main design criteria are based on results obtained from the PFS testwork carried out on representative samples (SGS, 2021). Mass balances and simulations were calculated in JKSimMet 6.3 using nominal design values. Crushing and grinding equipment were selected and sized by Metso:Outotec based on PFS testwork (Drop Weight Test, Bond Abrasion Index and Bond Work Index), PBT tests performed in York, PA and subsequent simulations using Metso's proprietary BRUNO simulation software (Metso, 2020; Metso:Outotec 2022). The tailings water recovery equipment requirements were calculated by Takraf based on laboratory and pilot filtration testwork (Takraf, 2021). Characteristics for sizing the concentrate thickeners and filters were based on vendor databases using similar feeds. The overall power consumption includes a 10% allowance on the flotation and water recovery stages.
Source: Vizcachitas Project , 2022 Technical Report, Sections 1.17 and 17 (Recovery Methods), pages 17, 270–286.
