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Harmony to install world-first railveyor system at new mine
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9th June 2006
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South African gold miner Harmony Gold says that its Phakisa and Sub-66 decline projects, at Tshepong mine, are well on track.

The goal of the Phakisa project is to hoist 90 000 t a month at a recovered grade of 7,29 g/t, producing 648 kg of gold at a cost of R425/t by May 2010. At present, the project, which was restarted by Harmony in July 2003, is 52% complete, against a plan of 53%, and the capital cost to date is 54% of the total, compared with the 62% planned, indicating that the earned value of the project is well in line.

Immediately adjacent to Phakisa, the Sub-66 project comprises a twin decline system from 65 level to 72 level which will allow mining on 69 and 71 levels, below the current mine. The declines are 1 164 m in length and consist of a material decline equipped with a belt con-veyor and a monorail system, as well as a chair-lift decline for the transportation of personnel.

The project was started in April 2003 and is 59% complete, against a plan of 64%. The capital cost to date is 61% against the 65% planned. The total capital cost of the project is R280-million, with R174-million spent to date, leaving a balance of R107-million. Adverse ground conditions experienced in the upper portion of the declines were the main reason for the delay in the schedule.

However, these conditions have now improved and are not expected to affect the overall sche-dule of the project.

Tshepong project GM Tom Smith says that, with the Sub-66 project, the mine is doing every-thing from designing to construction and installation itself. The project goal is to produce 48 600 t of ore per month at a grade of 7,21 g/t, yielding 350 kg of gold. First gold production is scheduled for August this year and full production by July 2008. Harmony will use state-of-the-art techno-logy and best practices in bringing these projects into production.

An example of this is the world-first railveyor system that is being installed at Phakisa to transport the rock mined to the adjacent Nyala shaft, where it will be hoisted to surface. It comprises a system of trains running on a track with external electricity primary drive units. The trains consist of small hoppers connected to each other with flexible joints to form a trough. A track with over- and underchange loops at each end enables the trains to run continuously, like a conveyor belt on wheels. Project mananger Marius de Leeuw states that the system combines the best features of conveyor and rail systems; for instance, it conveys material as a conveyor with high flexibility and increased capacity, but can negotiate curves as in a rail system. A further advantage of the railveyor system is that it is fully automated and very safe, as there is a low fire and accident risk associated with it. The system is designed for a capacity of 115 000 t a month and will cost R21-million to install, compared to R31-million for a conventional rail system and R30-million for a conveyor-belt system. The operating cost, at R2,51/t for the 5-km distance, compares with R3,58/t for a conveyor and R5,68/t for a rail system.

Other technologies that are under investigation include electric rock drills, which De Leeuw says are already being used by other mining majors, such as AngloGold Ashanti, and new cordless light-emitting diode cap lamps which are reported to be lighter and easier to wear. The lamps are made in China and have been approved by the Department of Minerals and Energy. “This means that miners will no longer have to carry those heavy batteries on them,” says De Leeuw.

He adds that the cost of the lamps is about double the price of an ordinary lamp, but that the maintenance cost is low.

“They can last up to three years without maintenance,” he says.

“The electric drill systems are less noisy and more efficient energy users than conventional systems, which means that there will be reduced cases of employees losing their hearing because of the noise created by conventional systems, and it will have a positive effect on the bottom line,” he says.

New technology included in the design will reduce the use of compressed air throughout the mine, increase the positional efficiency of fridge plants and also improve productivity by redu-cing reject temperature.

Phakisa project manager Anton van Wyk reports that the project is expected to be on budget and on time. “We are currently installing shaft pipes and we expect the project to be completed soon,” says Van Wyk.

Electrical installation is scheduled for Decem-ber 8 and, by November, it is expected that refri-geration installation, as well as surface work and the service centre, will have been completed. First gold at Phakisa is anticipated by May 2008. The project is considered low-risk because the company already knows the area it operates in. Work at Phakisa is carried out on a 24/7 basis. “We have also started to recruit labour that would go into training on July 1; we have a call-back list from previously-retrenched employees and we will be recruiting those people first,” says van Wyk.

He explains further that the mine project will be completed by February 2009. At full complement, the project will employ 2 500 people. Mining at Phakisa will be carried out mainly on the basal reef horizon. The basal reef zone consists of a siliceous quartzite with a thin basal conglo-merate. This zone is overlain by khaki shale.

The A, B and leader reef horizons are also present in the Phakisa lease area, but are not economically viable, based on existing information. Exploration of these horizons is planned to determine possible payable reserves. The area is divided into the black chert and steyn basal reef facies and subdivided into three and five geozones respectively.

Operations director Bob Atkinson says that, as the projects come into production, they will be combined with the existing Tshepong mine to form a single mine that will rank among the larger gold mines in the world. The mine will have a resource of 166,5-million tons at 9,11 g/t and reserves of 43,2-million t at 7,2g/t. Atkinson says that the combined production will be 245 000 t a month and that the new entity will produce some 700 000 oz of gold a year. The life-of-mine will be in excess of 20 years. A further opportunity exists of including the Nyala shaft, which has a large but lower-grade orebody and is currently under care and maintenance. The viability of this will be dependent on the sustainability of the current gold price. The benefits of merging the two operations include all the normal scale of operations advantages, such as shared infrastructure. The mines are adjacent and mine the same basal reef orebody.

Harmony is interrogating ways to bring higher-grade blocks of reserves into production sooner than initially planned. Van Wyk says Phakisa was acquired in 2002 for a book value of R1 as part of the Freegold acquisition.
Edited by: Ollie Madlala

 

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