This report describes the processing facilities at the Caylloma mine, which uses differential flotation to produce lead–silver and zinc concentrates.
Report context
This technical report is dated December 31, 2023, and covers the Caylloma Mine operations in the Caylloma District, Peru. The Bateas processing plant resumed operations in October 2006 treating 600 tpd of polymetallic mineral. Capacity increased progressively, reaching 1,300 tpd with installation of a 1.8 m by 2.4 m ball mill in 2009, and 1,500 tpd at the end of March 2016 with installation of two Derrick Stack Sizer vibrating wet screens.
Processing route
Crushing and milling circuits
The crushing circuit is fed from a 10,000 t capacity stockpile used for ore storage and blending. Feed enters a coarse hopper with 450 t active capacity and 30 cm separation grates. Material passes through an apron feeder to a vibrating grizzly, then to a Kurimoto jaw crusher producing a product size between 76 mm and 90 mm. Material is transported to a two-deck vibrating 6 by 14-foot (1.82 x 4.27 m) screen. Undersize (100% passing ¾ inch) goes to the stockpile; oversize feeds a Sandvik CH-420 secondary crusher. Secondary crusher product goes to a two-deck vibrating 5 by 14 foot (1.52 x 4.27 m) screen, with undersize feeding the stockpile and oversize feeding a Sandvik CH-430 tertiary crusher whose discharge returns to the initial conveyor belt to close the circuit. The actual capacity of this circuit is 1,800 tpd.
A standby primary crushing circuit exists, starting at a 100 t capacity coarse hopper feeding a Kueken 24 by 36-inch (0.6 x 0.9 m) jaw crusher via a Ross chain feeder. Three permanent magnets and one electromagnet on the conveyors prevent entry of tramp iron.
The grinding circuit has two stages. The primary stage operates in open circuit with two ball mills (Comesa 2.4 m by 3.0 m and a Denver 2.1 m by 2.1 m). The secondary stage operates in closed circuit with three ball mills: a Magensa 1.8 m by 1.8 m, a Hardinge 2.4 m by 0.9 m, and a Liberty 1.8 m by 2.4 m.
The Comesa and Denver primary mills discharge to a flash cell (SK 240). Flash cell concentrate goes to the lead thickener; tailings feed a 6 by 6-inch (15 x 15 cm) horizontal pump feeding the Derrick Stack Sizer. Undersize goes to flotation; oversize feeds the three secondary ball mills. Discharge from the Hardinge and Magensa mills feeds a 6 by 4 inch (15 x 10 cm) horizontal pump feeding the D-15 cyclone. Fine product from the cyclone goes to flotation; coarse product returns to the secondary ball mills. Discharge from the Liberty mill also feeds the flash cell (SK240). The final product of the grinding circuit is 55% passing 130 µm.
Metallurgical treatment
Treatment is via differential flotation, first floating lead–silver followed by zinc.
Lead–silver flotation circuit: D-15 cyclone overflow and Derrick Stack Sizer undersize feed a 10 m³ conditioner before entering a TC-20 unit cell of 20 m³ capacity. Unit cell tailings feed three TC-20 rougher cells. Unit cell and rougher concentrates feed primary cleaner cells (four 3 m³ OK-3 cells). Primary cleaner concentrate feeds secondary cleaner cells (three 3 m³ OK-3 cells). Secondary cleaner concentrate feeds tertiary cleaner cells (two 3 m³ OK-3 cells). Tertiary cleaner concentrate forms the final lead–silver concentrate. Rougher tailings feed scavenger flotation (two TC-20 cells). Scavenger concentrate and primary cleaner tailings return to the Derrick Stack Sizers. Scavenger tailings feed the zinc flotation circuit.
Zinc flotation circuit: Lead–silver flotation tailings go to three conditioners (two 10 m³ and one 22 m³). Conditioned pulp feeds zinc rougher flotation (two RCS 20 cells of 20 m³ and six 8 m³ OK8U cells in series). Rougher concentrate feeds a four-stage cleaner circuit: one RCS 10 cell of 10 m³, then five, three, and two 2.8 m³ Sub-A30 cells for primary, secondary, and tertiary cleaners respectively, with a fourth cleaning stage. Rougher tailings feed scavenger flotation (two 8 m³ OK8U cells). Scavenger tailings are the final tailings of the whole process.
Concentrates thickening and filtration
Lead–silver concentrate is thickened in an Outotec 9.0 m diameter thickener; underflow pumps to a 1.8 m diameter disc filter (six discs). Filtered lead concentrate contains on average 7.5% moisture. Zinc concentrate is thickened in an Outotec 12.0 m diameter thickener; underflow pumps to a 1.8 m diameter disc filter (eight discs). Filtered zinc concentrate contains on average 9.0% moisture. Each filtered concentrate is discharged into covered temporary storage for truck transport.
Tailings disposal
Tailings are classified through cyclones. Underflow (approximately 40% of tailings) is used as hydraulic backfill in the mine. Overflow is pumped to the tailings storage facility. Water from the tailings impoundment is pumped back to the plant for reuse. Usage of tailings storage facility N°3 commenced in January 2013; capacity was increased to 921,000 m³ in January 2022, sufficient for four years at current production levels, with further expansion planned in 2025.
Requirements for energy, water, and process materials
Electric power is supplied through the Callalli substation from the national grid. The whole operation requires 7.8 MW including 3.2 MW for the processing plant. Two diesel generators provide backup power. Processing plant water consumption is 2.45 m³/t, with approximately 74% (1.82 m³/t) recovered from the tailings facility and 26% (0.63 m³/t) fresh water. Reagents and consumables include sodium cyanide (10 g/t), copper sulphate (239 g/t), zinc sulfate (954 g/t), xantato Z-11 (6 g/t), xantato Z-6 (16 g/t), calcium oxide (483 g/t), foaming agent MC 5 (94 g/t), and steel balls (720 g/t).
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Crushing circuit actual capacity | 1,800 tpd | Operating data |
| Grinding circuit final product fineness | 55% passing 130 µm | Design specification |
| Silver recovery (2022) | 81.34% | Historical operating data |
| Gold recovery (2022) | 31.78% | Historical operating data |
| Lead recovery (2022) | 87.83% | Historical operating data |
| Zinc recovery (2022) | 88.75% | Historical operating data |
| Historical achievable lead recovery | 90% | Historical operating data |
| Historical achievable silver recovery (in lead concentrate) | 81% | Historical operating data |
| Historical achievable zinc recovery | 88% | Historical operating data |
| Lead concentrate moisture | 7.5% average | Operating data |
| Zinc concentrate moisture | 9.0% average | Operating data |
| Tailings used as backfill | Approximately 40% | Operating data |
| Total power requirement | 7.8 MW | Design/operating |
| Processing plant power requirement | 3.2 MW | Design/operating |
| Plant water consumption | 2.45 m³/t | Operating data |
| Water recovered from tailings facility | 1.82 m³/t (74%) | Operating data |
| Fresh water consumption | 0.63 m³/t (26%) | Operating data |
| Tailings facility N°3 capacity (January 2022) | 921,000 m³ | Design/operating |
| Tailings facility N°3 life | 4 years at current production | Design estimate |
Project website: https://fortunamining.com/
Technical qualifications
The report notes that the qualified person considers process requirements to be well understood and consistent based on actual observed conditions in the operating plant. There is no indication that the characteristics of the material being mined will change, with the expectation of the high zinc oxide material that has been accounted for, and therefore the recovery assumptions applied for future mining are considered reasonable for the life of mine. The plant is of conventional design and uses conventional consumables. The report notes that metallurgical recoveries of lead and zinc are affected due to the increase in treatment of oxidized ore to 11% due to its higher gold head grade. From late 2009 to January 2011, a copper–silver concentrate was produced, but due to unfavorable commercial terms the production of copper concentrate was suspended and the copper circuit put on standby.
