Venice Mine Complex (VMC) currently has two operations in place. Firstly it is re-processing the six tailings dumps on site, that together hold 2.1m tons of material. Secondly, it is undertaking mining operations in three of the complex’s mines.
Tailings are liquefied using a weak cyanide solution. Drains then collect the tailings fluid, which is run through a trammel screen to remove larger material. The liquid passing through the screen is then transported to the Carbon in Leach (CIL) system through a series of pipes. The tailings retreatment plant can process 40,000 ton/month of tailings.
Carbon in Leach (CIL)
Cyanide is added into the No1CIL tank. Hydrogen peroxide is also added to assist in the leaching process. Slurry overflows from the mechanically agitated leach tank through six mechanically agitated CIL tanks to ensure complete dissolution of gold as a cyanide complex and absorption onto activated carbon. Carbon recovered on the screen is delivered to a bulk bag for re-use. Tailings discharging from the tailings linear gravitate to the waste tailings section.
Elutions extracted from the pregnant carbon are treated through electrowining circuits.
Tailings slurry passing through the CIL tailings screen gravitates via pipes to the waste tailings dam in the immediate vicinity of the plant. Regular sampling of the waste tailings slurry is done to determine the plant gold balance. Water on the tailings dam gravitates via a penstock into a return water pond from which return water is pumped to the plant for re-use.
Mining and Crushing
Mining has started with open pit mining in three mines in the complex. This will progress to underground mining. Mined ore is delivered by tractor and trailer to the main ore bin. Ore is withdrawn from the ore bin at a controlled rate and crushed by a gyro crusher and a series of 3 jaw crushers. After each crusher, material is fed over a vibrating screen; large particles are returned for recrushing, and fine material that passes through the screens progresses towards the next crusher and eventually on to the mill feed bin.
The ball mill has a maximum capacity of 5-6ton/hr. Ore is fed from the crushing line into the mill where it is ground with steel balls. Inlet dilution water is added to the mill feed chute to control mill slurry density. The ball mill discharges the resultant slurry via a trammel screen to the gravity concentrator. Any material not collected in the concentrator is pumped to a cyclone at the head of the CIL plant and treated with cyanide.
Ore particles are subjected to a force of 60 gravities in a fluidization process in a Knelson Concentrator. Water is injected into the rotating concentrating cone, and feed slurry is forced outward and up the cone wall, filling each ring to capacity to create a fluidized concentrating bed. When the concentration cycle is complete, concentrates are flushed from the cone into the concentrate launder through a patented multi-port.
Carbon in Leach (CIL)
The tails empty to a tank and pass through a thickener before passing to the carbon in leach (CIL) tanks. Cyanide and hydrogen peroxide are added into the No1CIL tank. Slurry overflows from the mechanically agitated leach tank through six mechanically agitated CIL tanks to ensure complete dissolution of gold as a cyanide complex and absorption onto activated carbon.
Processing and Refining
Concentrates from the Knelson concentrator and elutions extracted from the pregnant carbon from the CIL tanks are then processed and refined.