This technical report presents the proposed modifications to the existing Santander concentrator to process mineralised material from the Santander Pipe deposit, supported by historical operating data from the Magistral ore processing campaign.
Report context
This NI 43-101 Technical Report and Preliminary Economic Assessment for the Santander Pipe Deposit, Huaral, Lima, Peru, is dated April 2023. The report covers the Santander concentrator, which was acquired from Glencore/Los Quenales’ Rosaura concentrator, relocated, and upgraded with new equipment. The plant began operations in 2013 and has undergone continual optimisation since that time. From 2017 to 2022, the plant processed a total of 4.47 million metric tonnes of mineral. The Santander Pipe mine will share the infrastructure and associated services relating to the fully permitted and producing Magistral mine. CDPR has established a production plan that involves processing material from the Magistral Mine until early 2025, followed by processing mineralised material from the Santander Pipe until 2029.
Processing route
Existing Plant Configuration
The Santander concentrator currently processes Magistral ore and has two separate flotation circuits, one for lead concentration and the other for zinc concentration. The plant operates 24 hours per day, 7 days per week, with a monthly short shutdown for planned maintenance. Production rates increased from 1,250 t/d to 2,000 t/d, with an anticipated maximum capacity up to 2,500 t/d.
Crushing Circuit
Run-of-mine material is delivered to the primary crusher pad where it is stored for blending prior to crushing. A fixed grizzly with 12-inch aperture, located above the coarse ore bin, prevents oversized material from entering the primary crusher. A rock breaker located above the grizzly is used to break oversized rocks. The coarse material bin with 75 t live capacity discharges to two apron feeders of 36-inch and 42-inch width. The discharge from the bin is screened on a 4 ft by 12 ft double deck screen with 8-inch apertures on the top deck and 4-inch apertures on the bottom deck. Screen undersize passes to the collection conveyor while the oversize passes to the 24-inch by 36-inch primary jaw crusher.
Jaw crusher discharge combines with the by-pass fines for conveying to the secondary cone crusher. A 5-ft by 14-ft double deck screen ahead of the 4.25-ft standard Symons cone crusher is fitted with 3-inch aperture upper deck screen panels and 1-inch aperture lower deck panels. Fines less than 1 inch pass to the tertiary crushers while the oversize passes to the secondary cone crusher operating in open circuit. The secondary cone crusher discharge combines with the screen fines greater than 1 inch and is conveyed to the tertiary screens. Tertiary screen oversize passes to two tertiary cone crushers, which are 3-ft short head units operating in open circuit. Fines from each tertiary screen combine with tertiary cone crusher discharge and are fed to the fine ore bin as nominal 1-inch top size material.
Grinding Circuit
The grinding stage consists of two circuits in parallel, each containing a primary rod mill in open circuit followed by a secondary ball mill in closed circuit. The first circuit has a 7 ft by 12 ft rod mill operating with an 8 ft by 12 ft ball mill. The second circuit has a 9.5 ft by 12 ft rod mill operating with a 10.5 ft by 13 ft secondary ball mill. Both circuits are identical in operation. A 1,800-t fine ore bin discharges onto two belt feeders equipped with weight-o-meters for metallurgical accounting purposes, with a third feeder present as a standby unit.
The discharge from both the rod and ball mills are combined and pumped to a skim-air flotation cell for high-grade copper recovery. The SK flotation cell tailing is pumped to a cyclone battery of 15-inch cyclones. Cyclone overflow from the second circuit feeds the flotation circuit at approximately 35% solids w/w and at a P80 of 105 microns.
Proposed Modifications for Santander Pipe Processing
To upgrade the Santander concentrator to enable it to also process Santander Pipe mineralised material and produce copper concentrates, the existing lead flotation circuit will need to be modified. These changes involve the addition of a horizontal regrind ball mill before the cleaner flotation stage for copper, as well as a horizontal vibrating screen prior to the rougher flotation stage.
The flotation circuit will need to be modified slightly for the Santander Pipe material. Two additional equipment items will be added to the lead flotation circuit: a trash screen and regrind mill. As a result, the existing lead circuit will be modified to produce copper concentrate from the Santander Pipe deposit. When processing Magistral material, lead is floated prior to zinc flotation by depressing the zinc sulphides, which are then activated and floated. With material from Santander Pipe, copper minerals are floated prior to separate zinc flotation.
Proposed Flotation and Dewatering Circuit
The feed entering the flotation circuit is screened on a 4 ft by 12 ft horizontal high-frequency vibrating screen for cleaning prior to flotation. The copper rougher-scavenger flotation cells consist of eight OK8 unit cells in a 2-2-4 configuration. The first two cells will be used as conditioning cells followed by two flotation cells to produce a copper rougher concentrate that passes to the copper regrind cluster cyclones. The last four cells produce a copper scavenger concentrate which is pumped back to the head of the copper circuit. Scavenger tailings form the feed to the zinc circuit.
The underflow from the regrind cyclone cluster in the regrind circuit goes to a 4 ft by 8 ft regrind mill operating in closed circuit with the cyclone cluster. Cyclone overflow passes to the primary copper cleaners. The primary cleaner consists of six DR24 cells, with primary cleaner tailings combining with the scavenger concentrate, which are recycled to the head of the copper circuit. Concentrate from the primary cleaner flows by gravity to the secondary copper cleaners, which consists of four DR24 cells. Tailings from the secondary cleaners pass to the feed box of the primary copper cleaner. The concentrate from the secondary cleaners flows by gravity to the two-cell DR24 tertiary copper cleaners. The tailings from the tertiary copper cleaners pass to the secondary copper cleaners, while the tertiary concentrate (final copper concentrate) is sampled by an automatic cutter and pumped to the copper concentrate thickener.
The tailings from the copper circuit are conditioned with reagents in three zinc conditioner tanks in series. The discharge from the third conditioner flows by gravity to the first zinc rougher flotation cells consisting of two OK30 tank cells operating in series. The discharge from the second tank cell gravitates to a bank of eight OK8 cells operating as the second zinc rougher and scavenger bank in a 2-2-4 configuration. Tailings from the zinc scavenger bank (final tailings) flow to the tailings thickener. Concentrate from the two tank cells and the eight rougher-scavenger cells combine and are fed to the zinc regrind cluster cyclones.
Regrind circuit feed is classified using 10-inch cyclones, with the underflow passing to the 5 ft by 10 ft regrind mill operating in closed circuit with the cyclone cluster. Cyclone overflow passes to the primary zinc cleaner that consists of seven OK8 cells. Four cells operate as the first cleaner, with concentrate fed to the secondary zinc cleaner, while the tailings are fed to the zinc cleaner scavenger. Cleaner scavenger concentrate is recycled to the head of the zinc feed while the tailing discharges as final tailings.
The secondary zinc cleaner consists of three OK8 cells. Tailings from the second cleaner are recycled to the first cleaner, while the concentrate from the second zinc cleaner gravitates to the third-stage zinc cleaner. The third zinc cleaner consists of six DR30 cells. Tailings from the third zinc cleaner recycle to the second zinc cleaner, while the concentrate passes to the zinc concentrate thickener for dewatering.
The diameters of the copper concentrate thickener, zinc concentrate thickener, and tailings thickener are 30 ft, 50 ft, and 80 ft, respectively. Water from the concentrate thickeners passes to sedimentation ponds prior to discharging to the process water system where they are recycled back to the plant. Water from the tailing thickener is gravity fed to the tailings pond prior to being recycled back to the process water system. Tailing thickener underflow (nominal 50-60% solids by weight) is pumped to the tailing disposal dam. The concentrate thickener underflow is fed to holding tanks and used as a feed supply to the filter units.
The copper concentrate is filtered by an Andritz plate filter press. Concentrate (nominal moisture content 6-7% by weight) is discharged, by gravity, to the holding shed below for storage prior to being dispatched to Callao. A 29-plate 1.5 m square fully automated unit filters the zinc concentrate. The concentrate (nominal 8% moisture by weight) is discharged to the holding pen below the filter for storage prior to despatch to the port of Callao. A standby 5-disc filter is available with a diameter of 6 ft.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Plant design production rate | 2,000 (max 2,500) | t/d | Design |
| Historical throughput (2017–2022) | 4,470,000 | t | Historical operating data |
| Historical throughput (to Dec 2022) | 7,070,000 | t | Historical operating data |
| Average Zn recovery (2022) | 94.57 | % | Historical operating data |
| Average Pb grade in Pb concentrate (2022) | 50.56 | % | Historical operating data |
| Average Pb recovery (2022) | 67.55 | % | Historical operating data |
| Average Ag grade in Pb concentrate (2022) | 75.89 | oz Ag/t | Historical operating data |
| Proposed Pipe throughput rate | 106 | t/h | Testwork/design |
| Proposed fresh water requirement | 100–200 | m³/h | Testwork/design |
| Grinding circuit P80 | 105 | microns | Design |
| Flotation feed solids | ~35 | % w/w | Design |
| Tailing thickener underflow solids | 50–60 | % w/w | Design |
| Cu concentrate filter cake moisture | 6–7 | % w/w | Design |
| Zn concentrate filter cake moisture | 8 | % w/w | Design |
Project website: https://www.pascoresources.com/news-and-media/cerro-de-pasco-resources-files-preliminary-economic-assessment-for-the-santander-pipe-project
Technical qualifications
The mass and water balances for Santander Pipe material have been calculated at the PEA level based on the flowsheet developed and the selected design criteria. The report notes that additional infrastructure and services connections will need to be designed as part of the next stage of engineering studies in relation to the proposed dewatering and rehabilitation of the La Cuñada shaft. The SRK Consulting feasibility study for the expansion of the TSF is referenced as completed in 2022, with the dam expected to reach the 4,483.0 masl elevation, adding 2.98 Mm³ of additional tailings storage capacity.
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Source: Cerro de Pasco Resources – NI 43-101 Technical Report and Preliminary Economic Assessment for the Santander Pipe Deposit, Huaral, Lima, Peru, April 2023. Sections 1.16, 1.17, 17.1–17.6.
