This report describes a proposed expansion of the Copper Mountain mill to 65 kt/d through installation of a high-pressure grinding roll and fourth ball mill, with a corresponding life-of-mine plan.
Report context
The technical report, effective September 1, 2020, was prepared for Copper Mountain Mining Corporation to document the 65 kt/d expansion study and life-of-mine plan for the Copper Mountain Mine. The study assumes that the Ball Mill #3 expansion, an ongoing project that will add a third ball mill in parallel with the two existing mills and reduce grind size to 150 µm, is complete. The expansion examined in this report involves installation of an HPGR and a fourth ball mill to enable 65 kt/d throughput at a target grind size P80 of 165 µm. The current mill capacity is 40 kt/d. The report presents design inputs, comminution circuit configuration, and flotation circuit design for the proposed expansion.
Processing route
Current flowsheet basis
The existing Copper Mountain mill flowsheet is described as a relatively simple two-stage crushing, SAG, pebble crusher, ball milling, and sulphide flotation circuit design, currently supporting 40 kt/d of ore processing. The Ball Mill #3 expansion underway will add a third ball mill in parallel with the two existing ball mills. Table 1-7 in the report provides 65 kt/d plant design inputs on the basis that the Ball Mill #3 expansion is complete.
Proposed 65 kt/d comminution circuit design
A 60–89 primary crusher receives run-of-mine ore and reduces material to less than 143 mm. Product is sent to a 14 ft by 24 ft double-deck screen, with oversize material feeding an XL2000 cone crusher operating in open circuit. Because of the maximum top size allowed at the new downstream HPGR, the open screening format will be closed with a security screen that scalps material greater than 90 mm. This oversized material is returned to the secondary crusher feed stockpile. A final crusher product with P80 of 38 mm is then sent to a 164 kt capacity ore stockpile.
The fine ore stockpile will use existing apron feeders to transfer to a modified SAG feed conveyor, serving as the transition point to the new HPGR circuit. A chute will allow material to be sent directly to the HPGR or to the existing SAG, which will remain on standby. The HPGR, installed in a new building serviced by a 160-t crane, will operate in a closed loop with a screening plant. Three parallel 14 ft by 24 ft double-deck screens will wet screen the HPGR product to a 4 mm P80 product size. Fine ore bins above the screens will allow for 30 minutes of operating time if the HPGR is down for inspections or maintenance. Screen undersize material will be pumped to each of the two lines of ball mills.
Ball Mill #4, a 22 ft by 38 ft mill with 12.6 MW of installed power, will be installed adjacent to Ball Mill #3 within the existing building, in the location where the existing regrind mill is currently positioned. The regrind mill will be demolished in this plan. With the addition of Ball Mill #4, the ball milling line will comprise four mills operating in parallel: two identical 24 ft by 30 ft mills and two identical 22 ft by 38 ft mills, designated Lines 1 and 2, respectively. Each line of mills will supply flow to independent rougher flotation lines. The total installed power will allow for an average target grind size of 165 µm.
Proposed flotation circuit design
The existing rougher flotation circuit, with two banks of five 160 m³ tank cells, will receive flow from ball mill Line 2. A new building erected at the northeast corner of the existing concentrator will house additional flotation equipment for the expansion, as specified in the report's flowsheet design.
Key reported parameters
| Parameter | Unit | Value |
|---|---|---|
| Daily throughput (design) | kt/d | 65 |
| Crushing plant operating time (design) | % | 80 |
| HPGR, milling and flotation availability (design) | % | 93 |
| Crushing plant nominal throughput (design) | t/oph | 3,385 |
| HPGR, milling and flotation nominal throughput (design) | t/oph | 2,912 |
| Head grade (design) | % Cu | 0.30 |
| Rougher recovery (design) | % Cu | 87.2 |
| Cleaner recovery (design) | % Cu | 98 |
| Overall recovery (design) | % Cu | 85.5 |
| Concentrate grade (design) | % Cu | 28 |
| Concentrate production (design) | t/oph | 26.7 |
| Concentrate moisture (design) | % w/w | 8.5 |
| Current mill capacity (actual) | kt/d | 40 |
| Target grind size after Ball Mill #3 expansion (planned) | µm | 150 |
| Target grind size after 65 kt/d expansion (proposed design) | µm P80 | 165 |
| Final crusher product size (proposed design) | mm P80 | 38 |
| HPGR product size (proposed design) | mm P80 | 4 |
| Ball Mill #4 installed power (proposed design) | MW | 12.6 |
Project website: https://hudbaycoppermountain.com/
Technical qualifications
The report does not include specific details on metallurgical testwork, pilot plant results, or ore characterization studies underpinning the recovery and grind size assumptions. The 65 kt/d design inputs in Table 1-7 are presented on the basis that the Ball Mill #3 expansion is complete, and the report notes the regrind mill will be demolished as part of the proposed plan. No information is provided on capital or operating cost estimates, economic analysis, environmental permitting, or project execution schedule. The report does not present historical operating data comparisons or testwork results beyond the general description of the existing flowsheet. Performance projections for the HPGR circuit and fourth ball mill are design basis values only and have not been confirmed by operating experience at this configuration.
Source: Copper Mountain Mine 65 kt/d Expansion Study and Life-of-Mine Plan, NI 43-101 Technical Report, effective date September 1, 2020, Section 1.17 Recovery Methods.
