(General Information Release December 2004)
The Barbrook Mine is a recent revival of a greenstone mine extracting gold from carbonaceous sulphide veins running through the rugged mountainsides near the Swaziland borders of Mpumalanga, South Africa. Canadian listed Caledonia Mining Corporation has made the most of new technology in turning around the challenging mining venture. The reconfigured plant is operating at a capacity of 6,000 tonnes per month with head grades averaging 8g/t gold. They have recently installed proprietary technology supplied by Maelgwyn Mineral Services thought its South African subsidiary, Greenhills Mining & Industrial Services (Pty) Ltd
The equipment includes a 2-stage Imhoflot G-Cell cleaner flotation plant to upgrade rougher flotation concentrates, which in turn drives improved recoveries and efficiencies of the oxidation and leach processes. The Imhoflot G-Cell is an enhanced pneumatic flotation device utilising intensive pre-aeration and a centrifugal froth separator. With all aeration and process energy derived from the slurry pump delivery the benefits of the system include an extremely short residence time and absence of moving parts and instrumentation. The stainless steel G12 has a 1.2m diameter and a single pass capacity of up to 30m3/h. Simplicity of operation and low maintenance costs are added bonuses, considering the flotation plant has quadrupled concentrate grades and simultaneously improved recoveries.
In addition Barbrook Mine has installed two MMS Aachen Aerator leach reactors to drive the sulphide oxidation and cyanide leaching process at the plant. These proprietary in-line ceramic aerators operate at elevated pressure and incorporate microporous diffusers and intensive after-mixing technology. This gives dramatic increases in reaction kinetics using liquid oxygen. The first Aachen REA 300 has been installed as a pre-aeration device for sulphide oxidation. It has resulted in a 25% increase in gold recovery on the plant. The second Aachen REA 150 is operating in the subsequent cyanidation leach process. The result being that gold leaching is completed in the REA 150 circuit, allowing the Resin-in-Pulp circuit to be optimised for gold adsorption. The improved chemistry of the Aachen Aerators is attributed to the massive interfacial area produced by the formation of extremely fine and dispersed bubbles.