The Red Dog processing plant uses three stages of grinding and froth flotation to recover sphalerite and galena as separate zinc and lead concentrates, with a capital project under review to address declining feed grades and harder ore.
Report context
This technical report, dated 2014, describes the Red Dog Mine as a currently producing operation with all milling equipment in place. The report details the existing process plant configuration and presents a proposed capital project, referred to as the VIP2 project, which is under review to maintain concentrate production levels.
Processing route
Crushing and grinding
Primary crushing is performed by an Allis-Chalmers 42-inch by 65-inch gyratory crusher (400 HP) with a Fuller-Taylor 42-inch by 60-inch jaw crusher (200 HP) as backup. Primary grinding uses three Fuller SAG mills, each 22 feet in diameter by 8.5 feet long. SAG Mill 1 and SAG Mill 2 are each powered by 2,000 HP motors, while SAG Mill 3 is powered by a 2,650 HP motor. Secondary grinding uses a Fuller ball mill (16 feet diameter, 18 feet long, 3,000 HP). Tertiary grinding comprises three Marcy ball mills: two at 12 feet diameter by 12 feet long (1,250 HP each) and one at 10 feet 8 inches diameter by 15 feet long (1,000 HP).
Pre-flotation
Following crushing and grinding, slurry reports to a pre-flotation circuit to remove elemental sulphur and naturally occurring organic material. The pre-flotation section consists of a rougher stage using six Outokumpu OK-50 mechanical cells (950 HP total) and a cleaner stage using a Glencore Technology B5400/18 Jameson cell (5.4 metres diameter, 18 down-comers). The Jameson cell is used to minimize the loss via entrainment of both fine lead and zinc particles to the pre-flotation concentrate using dilution.
Lead flotation
The lead flotation circuit consists of a rougher circuit in closed circuit with cleaner columns. The lead rougher uses ten Outokumpu OK-50 cells (100 HP each). The cleaner circuit comprises one lead primary column (13.5 feet diameter, 42 feet tall, 130 HP) with cav-tubes and two lead secondary columns (4.9 feet diameter, 38 feet tall, 275 HP total) with two cav-tubes and two CPT air sparged columns. Xanthate is used as sulphide collector and cyanide is used as the main pyrite depressant. Three MPSI tower mills (1,515 HP total) are used for regrind in closed circuit, with normally two operating and one on stand-by. The final lead concentrate is thickened in an Eimco 60-foot diameter thickener and filtered by one Ingersoll-Rand pressure filter (142 HP). Typical lead recovery to the lead concentrate varies between 55-65% depending on ore type.
Zinc flotation
Lead flotation tailings reports to the zinc circuit. The zinc rougher uses twelve Outokumpu OK-50 cells (1,550 HP total), with the rougher bank split for first and second roughing. Copper sulfate is used to activate sphalerite while xanthate is used as the sulphide collector. The zinc rougher concentrate is reground by one M5000 IsaMill (2,012 HP) from Glencore Technology for additional liberation. The zinc cleaning circuit consists of first cleaners (four OK-50 and five OK-38 cells, 1,075 HP total), second cleaners (six OK-50 and two OK-38 cells, 800 HP total), and six CPT cleaner columns (12 feet diameter, 52 feet tall, 700 HP total) with cav-tubes. The tailings from the zinc cleaner circuit is further reground in another M5000 IsaMill (2,012 HP) before feeding a three-stage zinc retreat circuit. The retreat circuit comprises first retreat (three OK-50, four OK-38, two MX-14 cells, 950 HP total), second retreat (six OK-38 cells, 500 HP total), and two CPT retreat columns (12 feet diameter, 52 feet tall, 300 HP total) with cav-tubes. The zinc retreat final concentrate is combined with the zinc cleaner concentrate to make up the final zinc concentrate. The zinc concentrate is then thickened in an Eimco 140-foot diameter thickener and filtered by four Ingersoll-Rand pressure filters (433 HP total).
Tailings and water management
Tailings slurry from both the zinc rougher and the zinc retreat circuits are combined with the pre-flotation concentrate to form the final tailings. The final tailings are pumped to the tailings impoundment area where water is decanted and re-used in the milling circuit. During the summer months, excess water in the tailings impoundment area is treated prior to discharge via Outfall 001 to Red Dog Creek. Process water is sourced from tailings water reclamation; consumption averages 6,000 gallons per minute (1.4 ML/hr). Precipitation is in excess of that required to replenish water lost in concentrate shipped off site, and is of sufficient quantity to require annual discharge of treated water from the tailing pond.
Concentrate handling
Concentrate is stored on site then hauled by truck to the port site facility on the Chukchi Sea. The concentrates are stored at the port and then shipped to the contracted smelting facilities during the shipping season between early July and early October.
Proposed VIP2 project modifications
In order to maintain concentrate production close to current levels with the declining feed grades, and handle the expected harder ore, a capital project referred to as the VIP2 project is currently under review. The VIP2 project envisages that the main modifications to the grinding circuit will be to allow the SAG1 and SAG2 mills to draw the same amount of power as the SAG3 mill (2,650 HP each), and the addition of one M15000 IsaMill (3,000 HP) from Glencore Technology as a quaternary mill. The flotation circuit will be augmented with six OK-16 lead scavenger cells and one Jameson cell as a zinc first rougher concentrate cleaner. A power study has shown that the VIP2 project will not require additional power generation equipment.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Lead recovery to lead concentrate | 55-65 | % | Typical operating range depending on ore type |
| Average daily power draw | 23.1 | MW | Actual operating data |
| Peak power draw | 27.0 | MW | Actual operating data |
| Mill power consumption | ~92 | % of power generated | Actual operating data |
| Process water consumption | 6,000 (1.4) | gpm (ML/hr) | Average operating data |
| SAG Mill 1 power (existing) | 2,000 | HP | Design specification |
| SAG Mill 1 power (VIP2 proposed) | 2,650 | HP | Proposed design |
| SAG Mill 2 power (existing) | 2,000 | HP | Design specification |
| SAG Mill 2 power (VIP2 proposed) | 2,650 | HP | Proposed design |
| SAG Mill 3 power | 2,650 | HP | Design specification |
| M15000 IsaMill (VIP2 proposed) | 3,000 | HP | Proposed design |
Project website: https://www.teck.com/operations/united-states/operations/red-dog/
Technical qualifications
The flowsheet descriptions, equipment specifications, and performance data presented in this report are drawn from a NI 43-101 Technical Report dated 2014 for the Red Dog Mine. The VIP2 project modifications are identified as under review and are clearly distinguished as proposed design changes. Equipment details marked with strikethrough in the original equipment table indicate existing equipment, while italicized entries indicate VIP2 proposed additions. Figures referenced in the report (Figure 17-1, 17-2, and 17-3) are not reproduced in this article. The report notes that figures were prepared for Teck in 2001 and 2014.
Source: NI 43-101 Technical Report, Red Dog Mine, 2014, Section 17 Recovery Methods.
