Milling Concept Video
The state of the art Milling Process proposed to be used is “Continuous Vat Leaching” (CVL Process) and was developed by Innovat Minerals Process Solutions Ltd (Canada).
A video of this process can be seen here >>
Continuous Vat Leaching Operation
Korean Metals Exploration is evaluating both conventional sequential flotation processing as well as a novel and innovative vat leaching process which could potentially be used on its projects in South Korea.
Innovat Mineral Process Solutions Limited is the owner of the Continuous Vat Leaching (CVL) process. The Innovat CVL is essentially a “Turn Key” plant that consists of ROM feed hoppers and belt conveyors, two large rectangular tank/vats, freshwater tank, reagent tank, head tank, bucket wheel excavator, discharge hopper, a series of wash-filter screens, and a discharge conveyor, as depicted in the oblique schematic diagrams below.
Ore crushed to -6mm (1/4”) is continuously fed to the large rectangular vatsat one end of the Vat. Lixiviant is stored in tanks that discharge under gravity periodically through pipes in the bottom of the vat. The fluidization process results in intense leaching and liquifaction and these high intensity events accelerate dissolution of the gold and copper due to the dynamic contact between the leach solution and solid ore particles. The Head Tank is set at a height approximately double the depth of the ore bed. This hydrostatic pressure is used to inject solution into the ore bed.
At the end of the Vat opposite the feed is a slowly revolving Bucket Wheel Excavator, which continuously removes leached material from the vat. The void in the ore bed creates a level surface which gradually moves the vat material towards the discharge wheel. Slow rotation of the Bucket Wheel Excavator allows lixiviant to drain back into the vat during removal of leached material. The solids are discharged onto a belt conveyor and move through a series of wash and detoxification filter screen sections to systematically and selectively remove toxic materials and decant and recover lixiviant by solid-liquid seperation.
After metals recovery, process water is removed, reclaimed and recycled for re-use by Innovats novel Paste Thickener, eliminating the need for a tailings dam. The detoxified paste is environmentally safe and can be mixed with cement and placed as paste backfill into underground workings.
The advantages of the Innovat CVL plant include:
- Commercially viable treatment of low-grade Cu-Au ores.
- Leach tanks can be lagged for heating, permitting elevated temperatures to enhance leaching.
- Easy to operate. Monitoring of a CVL plant is estimated at 4 workers, with minimal training required.
- Low capital and operating costs. Plant simplicity with low-cost materials for construction.
- Recovery of metals speed is rapid, about 24 hours.
- Fully detoxified, neutralized dry tailings are available for immediate disposal as backfill.
- Tailings dams are not required.
- Leach solutions are contained. Minimal environmental risk of leakage or accidental discharge.
- Recovery and recycling of glycine lixiviant (estimated at <5% losses).
- Recovery and recycling of process water (85-90% recovery of water).
- Can be used in dry, wet, cold or environmentally sensitive locations.
- Low environmental footprint of the CVL plant.
Glycine (NH2CH2COOH) is a low-cost, non-toxic, stable, environmentally benign amino acid/reagent that can be recovered and re-used. It is commonly used as an animal food and as a food additive, it is biodegradeable and non-toxic to most living organisms. Mining & Process Solutions Pty Ltd (“MPS”) holds the global licence to the GlyLeach™, a glycine leaching process developed by Curtin University’s Western Australian School of Mines. GlyLeach™ is an environmentally benign hydrometallurgical process that is capable of leaching base and precious metal oxide, mixed oxide and sulphide ores under alkaline conditions of pH 9-12. Leaching can be enhanced using mildly-elevated temperature (50-60oC). Glycine remains in the aqueous solution after metals recovery and is easily recycled for re-use with minimal losses.
Gold and silver can be recovered directly from the Pregnant Leach Solution (“PLS”) by adsorption onto activated carbon. Copper can be recovered by adding sulphur dioxide, sodium hydrosulphide (NaSH) to produce a pure, coarse-grained covellite copper concentrate, or through conventional SX-EW. Lead and zinc can also be recovered.
Oblique front and rear views of the schematic layout of a Continuous Vat Leach “Turn-Key Plant” (innovat Ltd.)