Final planning for new coal-mine

24th May 2002 By: Marius Roodt

Final planning is under way for the development of a R400-million extension to the south of the 25-year-old Bosjesspruit colliery in Secunda, Mpumalanga, for what will be a brownfields operation.

Bosjesspruit is an underground mine which forms part of energy group Sasol's Secunda mining complex, and exploits the No 4 lower coal seam 170 m to 180 m below surface.

It is anticipated that the new extension, at present known as the Irenedale Extension Project, will begin in four years and that the mine will reach its full rate of production of seven million tons a year by 2008.

Two ventilation shafts have already been sunk into the Irenedale area to a depth of 170 m, mining contractor Rucbor breaking a world raiseboring record for both depth and width, with a shaft diameter of 7,1 m.

The project, should it proceed, will extend the life of Bosjesspruit by 20 years, which is a significant enhancement on the existing life-of-mine plan. Indeed, at current mining rates of 7,4-million tons a year, the operation has little more than seven years life left after extracting a total of 144-million tons since 1977.

Mine manager Nico van Eck tells Mining Weekly in an exclusive interview that work is being done on the final implementation model, and that current planning envisages a seven-section operation producing a million tons a year each.

He says a study is also under way to assess the viability of producing solely for export, but that it is possible that the mine could be a 'double-stream' mine, producing for both export and for Sasol's Synfuels factory in Secunda.

The new extension is likely to draw on Bosjesspruit's extensive narrow-seam bord-and-pillar and total extraction mining experience, and many of the mine's 1 216 employees will find employment at the new development.

Indeed, Bosjesspruit has, over the last few years, worked intensely on optimising its mining methods to suit its massive 26 492 ha mining area.

Preparation is also under way for the closure of the existing mine and for relocation to the new operation.

Van Eck says that resources are being set aside for this.

In the meantime, priority attention is continuing to be given to strengthening the mine's overall performance, which has shown a marked turnaround over the past few years.

In the 1997–98 financial year, the mine operated at a R31-million-a-year loss, but currently, following considerable management intervention, the loss has been converted into a R102-million profit for 2001–2.

Van Eck explains that the turnaround has been achieved as a result of the renewal process.

Time management, standardising continuous mining equipment, better logistical systems, improved communication and mining optimisation studies had underpinned the improvements.

"Our largest improvement has come from as simple a thing as starting shifts on time and improving changeovers." The delay between the mine's two shifts, for instance, has been cut from 120 minutes to around about 10 minutes, achieved following a three-month consultation process with labour unions. Another factor has been the upgrading and revamping of the underground transport system. Roadways are kept clear of water and non-flameproof bakkies have been deployed to speed up transport to the working areas. Given that the furthest working area is some 17 km from the shaft entrance, these better travelling speeds have made a significant impact.

It is now possible to travel at speeds of up to 40 km/h, well up on the 15 km/h possible when the mine was using the old flameproof buses. This has also enabled the workforce to improve throughput with the ton-per-employee rate expected to rise to 5 800 during the course of the year. Productivity has been further enhanced by a programme to use the shift between the two production shifts to do maintenance, lay cables and to carry out belt and pipe extensions.

Van Eck believes productivity will continue to rise in the years ahead due to the fact that mining is taking place at the outskirts of the property and a process of reversing the pillar extraction is beginning.

"The configuration makes us a high-cost mine," he explains, admitting that the operation is currently the third highest-cost producer in the six-operation Sasol Mining group.

"But we are beginning to become competitive, and with the reverse-pillar mining, we think that within two years we will be on a par with Sasol Mining's best performers." The introduction of a standardisation programme for the mine's heavier equipment, particularly its continuous mining systems, is also paying off. The ton-a-minute production rate has risen from seven to 11,5. Bosjesspruit has reduced the number of machines it uses, while continuing to produce at the same levels of output – three years ago it had 16 – two of which were longwall units – and today it has only ten continuous miners in operation. This rationalisation exercise has helped to reduce costs substantially, as a third of the operation's costs related to its heavy equipment, with the balance shared in equal parts by labour and consumables.

In addition, Bosjesspruit has, together with the CSIR, worked on what it believes to be an optimal pillar design. It now mines its pillars to 28 m by 28 m centres at a height of 2,8 m, whereas previously, it was 30 m by 30 m centres. This has been particularly important given that Bosjesspruit has the narrowest seam, at 2,8 m, of all the group's mines, which average 3,4 m.

The mine also plans to introduce battery haulers and double-boom roof bolters in the not too distant future.

Bosjesspruit plans to implement all these improvements while maintaining its solid safety and environmental performance.

The mine was the first in the Sasol group to achieve a year entirely free of lost-time injuries and it became the first underground coal-mine in South Africa to obtain an ISO 14001 environmental management rating in May 2000.