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Continuous Leach Reactor
Continuous InLine Leach Reactor Operation
The continuous ILR is designed to accept dilute, high-grade gold concentrates in order to recover the solid gold into solution. The gold is recovered from the solution by means of electrowinning technology. The feed slurry reports to the feed cone where it is de-watered. The cone holds the solids and the water overflows to the ILR tails sump. The feed cone is controlled using a load cell and pinch valve combined in a PID timer loop. The load cell measures the mass in the cone. The solids are allowed to build-up in the cone to form a bed until the bed reaches a predetermined mass when the controller allows the timer circuit to open and shut the feed valve.
The thickened feed reports to the reactor drum feed. Fresh reagents and return barren solution from the electrowinning circuit are added at the feed. The drum rotates around a horizontal axis. The drum is rotated only fast enough to ensure fresh solution is mixed through the solid. The drum inlet and outlet are set to create a low angle of repose across the drum. The solids are agitated only enough to keep the mass moving from feed to outlet. A set of internal baffles allow movement of solids through the drum but inhibit short circuiting and help to hold very coarse gold particles back. The mass of the solids retained in the drum dictate the residence time. Solution passes through at a controlled rate. The solution and solids pass through at rates independent to each other. This enables the equivalent of a low leach density to be achieved. The low-density leach allows high levels of fresh reagent to be passed through the solids.
Solid and solution pass out of the reactor drum and into the pregnant solution sump. This sump is divided into three interconnected sections. The first section allows the solids and solution from the reactor tail to report to the solids recirculation pump. This pump transfers all solids to the tails settling cone. The solids settle to the base of the cone and are thickened. This solid reports to the inclined dewatering screen. The solids are dewatered to > 83% w/w and are dropped from the end of the screen into the tailings discharge sump. Any underflow solids from the dewatering screen are returned to the first two sections of the pregnant solution sump.
The overflow from the tailings settling cone reports to the second section of the pregnant solution sump. The third section of the pregnant solution sump incorporates a set of lamella plates, which completes the clarification of the liquor. The overflow from the lamella plates reports to the pregnant solution pump, which pump solution to the solids settling vessel. The solids settling vessel is a safety trap to ensure minimal solids reach the electrowinning cell. Flocculent is used to improve clarification performance if required.
The overflow from the solids settling vessel reports to the electrowinning cell. The barren solution overflows from the tail of the electrowinning cell and is returned back to the feed of the reactor drum. The system makes excess solution, which is released as overflow from a small tank located at the reactor feed.
If electrowinning is not metallurgically feasible, other options include Activated Carbon, Aurix resin and Merrill
Crowe interfaces.
Specific Advantages Of The Continuous InLine Leach Reactor
- Demonstrated ability to treat high volume sulphide streams as well as free gold
- Significant achievements on complex ores as well as oxide ores
- Extra chemicals added only as required, reducing reagent use and cost
- Continuous flow allows for instant and straightforward gold accounting
- Variety of solution recovery options including electrowinning, carbon columns, zinc precipitation and resin absorption
