The Corani plant is designed as a 27,000 t/d two-stage sequential flotation concentrator producing separate lead (with silver) and zinc concentrates.
Report context
The Corani Project 2019 Technical Report, dated 17 December 2019, presents the processing design for the Corani orebody at a nominal rate of 27,000 t/d. This chapter (Recovery Methods) describes the process flowsheet, design criteria, and supporting testwork used to define the proposed plant. The design emphasizes a compact footprint suited to steep, high-altitude terrain with limited flat space.
Processing route
Site layout considerations
The project site is located on steep sloping, high-altitude terrain with limited flat space. The process plant layout was developed to reduce footprint and capital cost, working within topographical constraints: mine to the north, a steep mountain range to the west, and a swamp to the east. The plant is laid out as a narrow facility, with the primary crusher product conveyor using the existing hill to feed the stockpile with a shallow incline.
Crushing and stockpile
Run-of-mine ore with a F100 of 1000 mm will be delivered by 135-140 t trucks (CAT 785) into a single dump hopper with 240 t live capacity. Ore will be crushed by a 50’ x 65’ gyratory crusher with a closed side setting of 120 mm, then discharged via a belt feeder onto a sacrificial conveyor (38 m) and transferred to an overland conveyor (650 m). The sacrificial conveyor is equipped with a metal detector; the conveyor stops if tramp metal is detected and an operator removes it using an overhead hoist. A weightometer on the overland conveyor monitors crusher production and stockpile feed rates.
The overland conveyor feeds a single conical coarse ore stockpile with total storage of approximately 49,000 t. Live capacity was estimated at 7% of total capacity, with the remainder recoverable using earthmoving equipment. Jenike and Johanson flow property tests on crushed ore (May 2019) indicated a strong tendency to form stable ratholes, which will reduce likely live capacity; this will be managed by using a dozer or excavator when ore is not being crushed to the stockpile.
Reclaim uses two variable-speed apron feeders, each capable of providing 100% of full base case tonnage to the SAG mill, though normally operating at 50% capacity for even drawdown. The SAG mill feed conveyor is fitted with a weightometer before the pebble recycle discharge point to measure new feed rate for process control and metallurgical accounting.
Grinding and classification
The grinding circuit was designed from ore characterization testwork including Bond crushing, rod and ball mill work indices of 9.0, 11.8, and 14.7 kWh/t respectively, and a JK SMC (Axb) value of 80. The circuit consists of a semi-autogenous (SAG) mill and ball mill in closed circuit with a cyclone cluster (SAB configuration). Cyclone overflow is designed at a nominal density of 32% w/w solids. The product P80 will vary with ore hardness, from 70 µm to 120 µm based on life-of-mine ore hardness data.
Flotation and regrind
Flotation is a two-stage sequential circuit. Primary cyclone overflow feeds lead rougher flotation. Lead rougher concentrate reports to a lead regrind circuit, followed by a cleaner scalper (Jameson cell) and three stages of cleaning, including two column flotation stages, to produce the final lead concentrate. Lead rougher tailings and lead cleaner scavenger tails feed zinc rougher cells. Zinc rougher concentrate feeds a zinc regrind circuit, then a cleaner scalper (Jameson cell) and three stages of cleaning (including two column flotation stages) for the final zinc concentrate. Zinc rougher tails and zinc cleaner scavenger tails are combined as final tailings.
Design recovery is 75% for lead in the lead flotation circuit, followed by 69% for zinc in the zinc flotation circuit.
Concentrate and tailings handling
Lead and zinc concentrates are thickened in high-rate thickeners, filtered in conventional pressure filters, and transported to port.
To reduce water consumption, flotation tailings are thickened in high-compression thickeners and filtered in conventional pressure filters. Filtered tailings are transferred by conveyor to a tailings stacker, stockpiled, then transported to DDMR for co-disposal with mined waste to form a stable waste deposit.
Availability basis
The design basis is 70% availability for the crushing circuit, 92% for grinding and flotation, and 82.8% for concentrate and tailings filtration, based on 365 operating days per year.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Treatment rate | 27,000 t/d | Design |
| Crushing circuit availability | 70% | Design |
| Grinding/flotation availability | 92% | Design |
| Filtration availability | 82.8% | Design |
| Lead recovery | 75% | Design |
| Zinc recovery | 69% | Design |
| Primary crusher | 50' x 65' gyratory, CSS 120 mm | Design |
| ROM feed F100 | 1000 mm | Design |
| Coarse ore stockpile total capacity | ~49,000 t | Design |
| Stockpile live capacity | ~7% of total | Estimate |
| Cyclone overflow density | 32% w/w solids | Design |
| Cyclone overflow P80 range | 70–120 µm | Based on LOM hardness data |
| Bond crushing work index | 9.0 kWh/t | Testwork |
| Bond rod mill work index | 11.8 kWh/t | Testwork |
| Bond ball mill work index | 14.7 kWh/t | Testwork |
| JK SMC (Axb) | 80 | Testwork |
| Tailings thickening | High-compression thickeners | Design |
| Tailings filtration | Conventional pressure filters | Design |
| Concentrate filtration | Conventional pressure filters | Design |
| Regrind | Lead and zinc regrind circuits | Design |
| Cleaning stages | Scalper (Jameson) + 3 stages (2 column) | Design |
Technical qualifications
Specific limitations and testwork notes from the report include the following. The coarse ore stockpile live capacity was estimated at only 7% of total, with a strong tendency to form stable ratholes identified in flow property testing; management will require dozer or excavator assistance. The grinding circuit cyclone overflow P80 is stated as variable between 70 µm and 120 µm depending on ore hardness. Design availabilities differ by circuit area, and filtration availability is notably lower than grinding. All recoveries and throughputs are design figures, not operating data. The report does not present historical operating data.
Source: Corani Project 2019 Technical Report, Chapter 17 (Recovery Methods), dated 17 December 2019, report reference 102760-05–RPT–01, Rev 1.
