South African firm, Dowding, Reynard & Associates (DRA), has secured a contract for the upgrade of the backfill plant at the No 1 Gold Plant of the Driefontein Gold Mine, and will be responsible for the project’s engineering, procurement and management. The project, valued at around R22 million, is expected to last 25 weeks and will be commissioned in February 2006.

Says Bruce Ebell of DRA, "The current backfill plant is unable to keep up with the mine’s demand for consistent quantity or quality of backfill. In addition, the current design of the plant, which consists of a primary and secondary cyclone to produce backfill and store it in two transfer tanks, lacks flexibility and does not optimise its energy usage. The new plant will utilise the existing tankage and will be built into the plant’s existing structure. DRA Electrical will install the instrumentation and control system which will be linked to the mine’s existing control room."

The system will be converted to a cluster design of cyclones to remove fine material from the slurry in a 2-stage process. This could be upgraded to a 3-stage process in the future should the mine require higher quality backfill. Large volumes of water are used in the process and two redundant tanks have been retrofitted to serve as a high rate thickener and process water tank to recycle water. The thickened tailings produced will be pumped together with normal plant tailings to the slimes dam.

Says Ebell "One of the main requirements placed on DRA for this project is that the old system remain in operation while the new one is built without affecting current production. Once the new plant is on-line, the old one will be de-commissioned. The difficulty in this would be during changeover and therefore considerable planning has taken place to ensure that the system is able to go live without interruption."

Adds Ebell, "The new backfill plant is expected to increase backfill production to 140 tonnes per hour from the current 50 tonnes per hour and this will be pumped in batches to the shaft. As much of the existing plant is still functional, the upgrade project is more economical than a complete replacement and the mine will be able to increase production or backfill quality as it requires in the future."

For further information contact:
Bruce Ebell
Dowding, Reynard and Associates
Tel: + 27 11 202- 8600
Fax: + 27 11 202- 8807
E-mail: brucee@drasa.co.za