This report details the processing facilities and planned upgrades for open pit and future underground block cave ore at the Red Chris Operations in British Columbia.
Report context
This technical report for Red Chris Operations, located in British Columbia, Canada, is dated 2021 and constitutes a 43-101 Technical Report. It describes the processing methods and planned modifications for treating open pit ores and evaluates process plant upgrades required for a future underground block cave operation based on a 2021 Prefeasibility Study (PFS) metallurgical testwork program.
Processing route
Current Plant Design Basis
The plant design for open pit ores was based on metallurgical testwork assuming open pit mining methods and employed a standard porphyry copper flowsheet using SAG and ball milling, flotation, regrinding, thickening and filtering to produce a gold-bearing copper concentrate at a moisture content of 8% for export.
Comminution Circuit
The plant consisted of a SAG mill–ball mill–pebble crushing (SABC) comminution circuit housed in a single process building. The target grind size was a P80 of 150 µm, with throughput taking precedence over grind size, resulting in typical grind sizes closer to 170–180 µm.
Flotation Circuit (as of May 2021)
The flotation circuit consisted of:
- Copper rougher: five Outotec TC-200 cells
- Mixed duty (copper rougher/sulphide rougher): one TC-200 cell and one TC-160 cell
- Regrind: primary ball mill in series with a secondary Vertimill targeting a regrind size P80 of 30 µm
- Cleaner circuit: two cleaner columns and a bank of five Outotec TC-50 cleaner scavengers
- Concentrate storage tank, thickener, and pressure filter
The flotation circuit was configured to produce a copper concentrate with a grade of 23–24% Cu. Originally configured as a two-stage cleaning circuit, the plant was often operated with only a single stage of cleaning due to insufficient capacity in the cleaner columns. In June 2021, a third flotation column was commissioned, and this single-stage issue no longer occurs.
Post-Construction Modifications
Subsequent to the initial construction, the plant underwent the following changes: installation of a pebble bypass system on the SAG mill, installation of an additional rougher flotation cell to increase rougher flotation residence time, and installation of a third flotation column to increase capacity of the cleaner circuit.
Process Improvements Underway
Process improvements underway as of the report included:
- Installation of a third Eriez Cavitation Tube Column in the cleaners, which started commissioning in June 2021
- Installation of two pre-rougher duty Eriez StackCells, due to be completed by Q1 2022
Newcrest was investigating the installation of a tailings thickener for NAG cyclone overflow. A new tailings cyclone cluster was planned to be installed adjacent the tailings thickener, should this project proceed.
Proposed Plant Requirements for Block Cave Underground
The 2021 PFS evaluated process plant upgrades required to meet the different ore characteristics of underground ores compared with open pit ores, specifically increased hardness and higher copper head grades. The 2021 PFS metallurgical testwork program confirmed that a flowsheet incorporating crushing, grinding, flotation, and concentrate dewatering was suitable for the planned underground block cave material. Two process options were evaluated:
- A Central Case (forming the base case) that would treat 13.6 Mt/a of underground ore through the existing SABC circuit plus a new single-stage SAG circuit; this concept was within the current maximum permitted throughput of 38,000 t/d average, 13.87 Mt/a
- An Upside Case (forming an alternatives case) that would treat 15 Mt/a of underground ore through the existing SABC circuit plus a new single-stage SAG circuit
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Target grind size (P80) | 150 µm | Design target |
| Typical operating grind size (P80) | 170–180 µm | Actual operating data |
| Regrind target size (P80) | 30 µm | Design target |
| Concentrate moisture content | 8% | Design target |
| Copper concentrate grade | 23–24% Cu | Design configuration |
| Maximum permitted throughput | 38,000 t/d average, 13.87 Mt/a | Permitted limit |
| Central Case underground throughput | 13.6 Mt/a | Proposed design (2021 PFS) |
| Upside Case underground throughput | 15 Mt/a | Proposed design (2021 PFS) |
Project website: https://operations.newmont.com/canada/red-chris-canada
Technical qualifications
This report describes historical operating data as of May 2021 and does not include performance results from process improvements commissioned after that date. The proposed block cave processing options are based on the 2021 PFS metallurgical testwork program and do not represent current operating conditions. All reported parameters are from the original design basis, actual plant operation, or 2021 PFS testwork as indicated in the table basis column.
Source: Red Chris Operations, British Columbia, Canada, 43-101 Technical Report, 2021, Section 1.15 Recovery Methods.
