The stacker conveyor leading out of the crushing plant.

An overview of the process plant at Gunpowder Copper, with the oxygen generation plant in the left foreground, the reagent plant in the centre foreground in front of the leach circuit and the Delkor filter in the centre background. The electrowinningand solvent extraction circuits are in the background on the right of the picture.

The grinding and thickening circuits in the centre of the picture, with the crushing plant in the background on the left.

The leach plant with the autoclave on the left and the leach tanks on the right of the picture.

The leach liquor is filtered on this Delkor horizontal belt filter. It has an area of 158 m 2 with a counter-current wash configuration and is the largest of its type in the world.

The autoclave equipped with five agitators in which the ore is subjected to a low temperature pressure leach. This is the first time this process has been applied to a copper ore.

The interior of the electrowinning tank house in which high gradeLondon Metal Exchange copper is produced.

Gunpowder Copper project successfully completed

Bateman Kinhill is in the final stages of the project to expand the existing copper cathode production capacity at the Gunpowder copper mine recently acquired by Western Metals Limited.

The expanded plant

The expanded plant will process 750 000 t/yr of chalcocite ore from an opencast operation mining the Esperanza ore body, typically containing 7,5 % copper, to produce 50 000 t/yr of high grade LME (London Metal Exchange) copper.

The ore is crushed in a jaw crusher and ground in a semi-autogenous (SAG) mill and then subjected to an acidic ferric sulphate leach in combination with an autoclave operating at low temperature and pressure. This is the first time this process has been applied to copper. The leach residue is thickened and filtered for disposal. The leach liquor is clarified, filtered and passed to the solvent extraction and electrowinning (SX - EW) circuit. The acidic rafinate from the SX - EW circuit is recycled to the leaching circuit.

To extract the copper in the leach liquor, BATEMAN reverse-flow enhanced coalescence mixer settlers were installed in the solvent extraction section. Similar units are operating successfully at La Caridad, Nacozari, Mexico; Sanyati Copper, Zimbabwe and at the El Arco pilot plant, Baja California, Mexico and have also been incorporated into the Bulong Nickel project. This type of mixer settler offers a higher process efficiency, reduced loss of organic solvent, lower capital cost, shorter construction time, a more compact layout and easier operation than conventional equipment.

The old plant

The old plant, which processed Mammoth ore containing about 4 % copper obtained from an underground mining operation, had a production design capacity of 13 000 t/yr and has been incorporated into the new plant.

Project details

The design of the expanded plant was completed by a team of 65 people in 7 months. The basic engineering package comprised a process flowsheet which was developed jointly with Aberfoyle. Other process routes were eliminated and all materials of construction were critically evaluated and selected. Critical areas to permit a fast track project were identified and long lead items specified and ordered.

Bateman Kinhill personnel assisted in the pilot plant operation during which a close working relationship was established with Aberfoyle personnel. Significantly, the team which was assembled for the project was based on the study team.

The fast-track project commenced in July 1997 with a site management team of 10 supervising 340 contractors and personnel. Construction was essentially completed within an 11 month schedule at a capital budget of Aus$92M. Dry commissioning started during June 1998 with electrowinning commencing in August. The project team executed 110 construction and procurement packages, poured 8 600 m 3 of concrete and installed 1 200 tonne of structural steel, 70 km of electrical cable and 32 km of piping.

Project cost

The total cost of the project was Aus$125M and it included the mine development, power supply and infrastructure.

More information on the project may be obtained from Tony Cau, General Manager, Base Metals, on +61-7-3320-3333 or email basemetals@batemanengineering.com.

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