Avgold Target Gold Mine Processing Plant

Client: Avgold Limited

Location: Free State, South Africa

Map showing the location of Avgold Target Gold Mine Processing Plant

Executive Summary

Avgold's $25-million metallurgical process plant processes 1.25 million tonnes of gold-bearing ore per annum. It employs innovative concepts coupled with proven design technology. Fluor performed detailed design of the processes, structures and mechanical and electrical works, as well as construction.

Client's Challenge

The facility, completed in 2002, was the first large grassroots gold mine built in South Africa in 20 years. Avgold wanted the newest technology applied to the plant design, including the broadest possible application of computerized automation. The gold recovery plant thus incorporated state-of-the-art technology, with a degree of automation that helped to minimize manpower and to reduce operating costs.

The gold is milled in a two-stage process, first through a grind mill followed by a ball mill in closed circuit with a cyclone cluster. The overflow from the cyclone is thickened and pumped to the leach circuit, where the gold is dissolved using cyanide. From the leach circuit, the slime gravitates to the carbon absorption section where the dissolved gold is absorbed onto the carbon. The slime residue from the absorption section can be pumped either to the tailings dam or the backfill plant.

Finally, the gold bearing carbon is removed from the absorption section and pumped to the elution circuit to remove the gold from the carbon. The gold in solution is plated out in the electrowinning circuit, where it is smelted.

Fluor's Solution

Fluor was awarded the design, construction and commissioning contract for the Target Gold Project. Detailed design was carried out at our office in Perth, Australia, and responsibility for construction was transferred to our site office at Free State, South Africa.

During construction, site employment peaked at more than 500 people, totaling 60,000 workhours during the construction phase. The construction portion of the project, completed within 12 months, expended more than 800,000 workhours without a single lost-time accident.

The majority of the materials and equipment were sourced from suppliers within South Africa.

The design of the plant included complete process, structural, mechanical and electrical design of its components: an ore storage silo with a 20-hour capacity and a stockpiles reclamation facility that bypasses the silo. Key facilities in the plant were ore storage and handling, milling and classification, pre-leach thickening, leaching, adsorption, residue disposal, gravity concentration, electrowinning and smelting and reagents storage and handling.

Conclusion

The president of Fluor's Mining & Metals organization remarked that the project “constitutes a landmark in terms of innovative Australian concepts coupled with proven South African design technology.”

We delivered a design that complied with the client's resolve to have the most up-to-date process plant possible. A majority of the materials and equipment was sourced from South Africa.