This section describes the recovery methods for the Ming Copper-Gold Mine project, which will use the existing Nugget Pond concentrator as-is without modifications, and details the process design criteria, reagent systems, and plant availability assessment.
The recovery of a copper-gold concentrate from the Ming Mine is based on using the existing copper concentrator located at Nugget Pond. The existing grinding and flotation circuits, and concentrate dewatering equipment will be used as-is without any modifications. Run-of-mine (ROM) mill feed from the Ming Mine is stored on an outdoor pad at the Nugget Pond site. It is fed through a two-stage crushing plant by front-end loader and the crushed material is conveyed into the crushed ore silo. From there, the ore is processed through the grinding and flotation circuits to produce a copper-gold concentrate, which is then dewatered and transported by truck to the Goodyear's Cove Port Site for shipment.
The process design criteria and operating parameters for the concentrator are based on historical operating data from the Nugget Pond operations during 2016 and 2017, as well as bench test results. The concentrator design capacity is 1,250 tonnes per day of ROM mill feed when running continuously 24 hours per day. The annual availability at design capacity is 95%, based on average Nugget Pond operations from January 2016 to November 2017, where the availability factor is calculated as the total number of hours the mill was reported to be operating in a given month divided by the total number of hours in the month. Days when the mill was shut down due to a lack of ore from the mine were not counted against plant availability, as this was an issue of lack of feed rather than the availability of the mill.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Concentrator design capacity ROM mill feed throughput | 1,250 | tonne/d (dry) | When running continuously 24 hours per day |
| Concentrator annual availability at design capacity | 95 | % | Total availability over 365 days for design purposes. Based on average Nugget Pond operations from January 2016 to November 2017 |
| Crushed ore top size | 12.7 | mm | Feed to SAG mill |
| Ground ore 80% passing particle size | 120 | micron | Grind size achieved based on plant data for operation at 1,250 tpd |
| Average overall copper recovery to concentrate | 96.0 | wt% | Based on average Nugget Pond mill data 2016 and 2017 |
| Copper concentrate grade dry basis | 27.7 avg., 25.0 min., 30.0 max. | wt% Cu | Based on average Nugget Pond mill data 2016 and 2017 and typical range from Nugget Pond operations and bench test results |
Overview
The Ming Copper-Gold Mine project will utilize the existing copper concentrator located at Nugget Pond for the recovery of a copper-gold concentrate. The existing grinding and flotation circuits, and concentrate dewatering equipment will be used as-is without any modifications. The concentrator has a design capacity of 1,250 tonnes per day of ROM mill feed and operates with an annual availability of 95% at design capacity, based on historical operating data from 2016 and 2017. The process design criteria are summarized in Table 17.1 of the technical report and include a crushed ore top size of 12.7 mm, a ground ore 80% passing particle size of 120 microns, an average overall copper recovery to concentrate of 96.0 wt%, and a copper concentrate grade ranging from 25.0 wt% Cu minimum to 30.0 wt% Cu maximum, with an average of 27.7 wt% Cu.
The concentrator uses a programmable logic controller (PLC) based process control system for the existing grinding circuit and the flotation plant. The control of the new process water reclaim pumps at Camp Pond and The Steady will be integrated into the PLC control system in the grinding area. The future operation will use a new process water reclaim pump house located at Camp Pond, which will eventually be relocated to The Steady later in the operation. Process water reclaim from the tailings impoundment areas will provide all of the process water required for the concentrator.
Key Process Stages
The process flow for the Ming Copper-Gold Mine recovery operations consists of several key stages: crushing, grinding, flotation, concentrate dewatering, and concentrate transport. Run-of-mine mill feed is stored on an outdoor pad and fed through a two-stage crushing plant by front-end loader, with the crushed material conveyed into a crushed ore silo. The material is then fed to a semi-autogenous grinding (SAG) mill, with a minimal amount of oversize material from the SAG mill trommel screen collected in a bin and periodically dumped back on the mill feed stockpile. The ground material from the grinding circuit is received in a flotation feed holding tank, which provides surge capacity and allows downstream processes to continue operating during short-term interruptions of the grinding circuit.
The flotation circuit consists of rougher, rougher-scavenger, cleaner, cleaner-scavenger, secondary cleaner, and tertiary cleaner stages. Flotation collector (Aerophine 3418A) and additional lime are added to the flotation feed holding tank to adjust the pH to the optimum range for copper-gold recovery and pyrite rejection. The ground material is pumped from the flotation feed holding tank to the rougher conditioning tank, where more conditioning time is provided and MIBC frother is added. Under certain conditions, the rougher concentrate grade from the first cells in the bank may be suitable as final concentrate, and the operator may direct this stream via the outside launder to the concentrate handling system. Additional 3418A collector and MIBC frother are added to the rougher-scavenger feed box, as these cells are designed to maximize recovery of copper and gold from the rougher tailings.
The concentrate from the primary cleaner stage is routed to the secondary cleaner stage, and the secondary cleaner concentrate is routed to the tertiary cleaner stage, from where the final concentrate product is directed to the concentrate dewatering system. Cleaner-scavenger concentrate is recycled to the cleaner conditioning tank, and tailings are routed to the rougher-scavenger flotation cell feed to scavenge additional copper and gold. The rest of the feed to the cleaner conditioning tank consists of rougher concentrate, cleaner-scavenger concentrate, and secondary cleaner tails, all of which are conditioned once again with lime and 3418A collector prior to being fed to the cleaner circuit. Hydrated lime slurry is added to the cleaner-scavenger, secondary cleaner, and tertiary cleaner feed boxes to maintain the optimum pH for copper-gold upgrading throughout the cleaner circuit, and additional 3418A collector and MIBC frother are added to the cleaner-scavenger feed.
Concentrate dewatering involves thickening and filtration. The concentrate is processed through a thickener, with the supernatant directed to the process water tank, and a filter press to achieve the required moisture content. The dewatered copper concentrate is then loaded into trucks and transported 142 km from the Nugget Pond site to the Goodyear's Cove Port site, where a truck dump station, concentrate storage building, and boat loading equipment are used to load ocean-going bulk carriers for final shipment.
Additional Interesting Data and Summary
The operating history of the Nugget Pond concentrator for the last two years was reviewed to evaluate the average processing plant availability. The availability factor is calculated as the total number of hours the mill was reported to be operating in a given month divided by the total number of hours in the month. In a few of the months, the mill had to be shut down temporarily as there was no ore available from the mine to process. These days were not counted against the plant availability since it was an issue of lack of feed rather than the availability of the mill. The typical plant availability factor was determined to be 95% based on the average over the operating period. One shutdown was required to install new equipment related to operating the plant at the increased 1,250 tpd capacity.
The reagent systems for the concentrator include Aerophine 3418A collector, MIBC frother, hydrated lime, zinc sulphate, and AERO MX983. Aerophine 3418A collector is a copper-gold collector reagent supplied in liquid form by Cytec Solvay and is purchased in 1000-litre tote tanks. MIBC frother is purchased in 200-litre steel drums and is not miscible with water, so it is best fed to the flotation process neat. Dry powdered hydrated lime (calcium hydroxide) is supplied in 1-tonne bulk bags and is mixed in batches to the required 5 to 10 wt% concentration for distribution to the process. A hydrated lime slurry makeup and distribution system is used to supply lime to various unit operations within the copper concentrator building, and a separate similar system is used within the grinding area. Zinc sulphate solution is metered into the flotation feed holding tank when needed. The scavenger flotation collector AERO MX983 is received in liquid form in drums and is delivered to the process via a diaphragm metering pump pumping directly from the drum.
Tailings will be disposed of by pumping in slurry form to existing and new tailings impoundment areas to be developed adjacent to the Nugget Pond mill site. New tailings slurry distribution piping will be installed to suit the tailings disposal plan. The site location and infrastructure associated with process water reclaim is described in Section 18 of the technical report.
Key Processes
- Two-stage crushing plant fed by front-end loader, with crushed material conveyed to a crushed ore silo
- Semi-autogenous grinding (SAG) mill and ball mill circuit with trommel screen oversize recycle
- Flotation feed holding tank providing surge capacity and pH adjustment with Aerophine 3418A collector and lime
- Rougher and rougher-scavenger flotation cells designed to maximize copper and gold recovery
- Cleaner, cleaner-scavenger, secondary cleaner, and tertiary cleaner flotation stages for concentrate upgrading
- Concentrate dewatering using a thickener and filter press
- Truck transport of concentrate 142 km from Nugget Pond to Goodyear's Cove Port Site for boat loading
- PLC-based process control system for grinding circuit, flotation plant, and new process water reclaim pumps
- Process water reclaim from tailings impoundment areas providing all process water requirements
- Tailings disposal by slurry pumping to existing and new tailings impoundment areas
Source: Ming Copper-Gold Mine , 2018 Technical Report, 2018. Project website: Rambler Metals & Mining Canada Limited (https://www.gov.nl.ca/eccc/projects/project-1487/)
Project website: Ming Copper-Gold Mine, 2018 Technical Report
