Gold Cyanide Leaching Process

Metso offers complete cyanide leaching plants irrespective of the material quality. Free-milling gold materials are cyanide leachable and so are the refractory gold materials after suitable pre-treatment. Possible pre-treatment methods such as pressure oxidation, bio-oxidation, roasting, and ultra-fine grinding are also included in our offering.

Metso's cyanide leaching plants are available as gold adsorption directly from the process slurry in carbon-in-leach (CIL) and carbon-in-pulp (CIP) processes. In addition, dissolved gold can be recovered from the solution after solid-liquid separation by Merrill-Crowe and carbon-in-column operations. The most suitable technology is determined on a case-by-case basis, based on the experimental data of the actual raw material. Using in-house expertise and specialized partners, our services cover everything required for successful project development from test work to delivery of an optimized plant with process guarantees.

Metso takes agitator and reactor solutions to a new level by using pre-designed leaching plant modules that improve the efficiency and quality of project implementation. Highly efficient Metso OKTOP® reactors focus on minimizing carbon attrition and maximizing gold recovery in the CIL and CIP processes. All aspects from manufacturing and installation to operation, safety, and maintenance are taken into consideration in the productization phase to help minimize time and costs during execution.

Cyanide forms environmentally hazardous components if proper protocol is not followed. Local environmental regulations and conditions define the requirements for cyanide detoxification. This makes cyanide detoxification a critical part of each cyanide leaching plant operation. Metso offers several process options for cyanide detoxification in addition to natural degradation or solution dilution. Cyanide detoxification by the SO₂ /air process is commonly used, but the most efficient detoxification method is selected based on individual process requirements.

The detoxification capacity requirements can be decreased by recycling the cyanide-containing solution. Detoxified cyanide solutions can also be used in other process areas. Metso's dewatering technologies provide the answer for these and other process steps that require solid-liquid separation.

Proven agitation technology with the Metso OKTOP 3200 agitator provides the ideal balance between conflicting requirements for optimal process performance:

• Provides solids suspension to distribute concentrate and carbon equally around the tank
• Ensures an acceptable efficiency rate for gas utilization through gas dispersion
• Minimizes carbon attrition to prevent unnecessary costs, attrition of activated carbon causes gold, and carbon losses in CIP and CIL processes

The Metso OKTOP launder system provides easy functionality to the cyanide leaching operation. Individual reactor by-pass is safe and easy through knife gate valves.