New Vaal Colliery, South Africa

17th March 2000 By: System Author

New Vaal Colliery Free State Name: New Vaal Colliery. Location: The colliery is situated immediately south of Vereeniging on the Free State bank of the Vaal river about 70 km south of Johannesburg.

Brief description: The colliery is an Anglo Coal mine, a division of Anglo Operations, and was established to supply coal to Eskom’s 3 600 MW Lethabo power station. It is an opencast strip mine producing 15-million sales t/y from three coal seams which have been previously mined by underground bord-and-pillar methods.

Brief history: New Vaal Colliery was established in 1983, with the first saleable coal produced in December 1985. The mine is currently mining the remaining coal in the Maccauvlei east area of Cornelia Colliery, which mined the area using bord-and-pillar methods from 1931 to 1969. Some 93% of the original reserve was left underground.

Products: The colliery produces the lowest-quality steamcoal currently burnt by Eskom. All coal is sent to Lethabo power station, where it is burnt in specially-designed boilers capable of handling this low-calorific-value (CV) high-ash coal.

Geology: The coalfield is known as the Vereeniging-Sasolburg coalfield. Coal occurs in the Karoo sandstones, siltstones and shales and was formed some 230-million years ago. The Karoo sediments overlie a thin sequence of Dwyka fillites, which rest unconformably on the Transvaal dolomites. The entire mining area is overlain by an average of 16 m of river sand deposited by the Vaal river as it migrated to the north. Three coal seams, the top, middle and bottom, are present. All three seams are mined simultaneously to provide an average quality blended CV of about 16 MJ/kg and 37,5% ash content. The area is extremely faulted and has numerous sinkholes, making mining floor conditions poor.

Reserves: Reserves originally totalled 750-million tons, but underground mining extracted some 55-million tons, leaving the balance to be mined by modern opencast methods.

Mining method: The colliery is an opencast strip mine using three draglines as the prime earthmoving equipment. The coal is loaded and transported to the plant using a fleet of electric shovels and 170 t rear dump trucks. The mine was the first in Anglo Coal to use Truck Dispatch, a computerised system which uses the co-ordinates from satellite triangulation to control the allocation of trucks, using the most economical travelling distances and minimising queuing time, producing coal at the correct quality blend from the three mining seams from as many as seven shovels.

Major infrastructure and equipment: The mine operates three 1 570W Bucyrus draglines, six P&H 2300 electric face shovels, three Demag H285 hydraulic shovels, one CAT 994 FEL, one Komatsu PC1000 and a fleet of 20 Euclid R170 rear dump trucks as the primary earthmoving fleet. An O&K S800 bucket wheel excavator is deployed as a prestrip sand operation. The ancillary fleet consists of 11 Komatsu D375 track dozers, three Komatsu WD 600 wheel dozers, three GD 70 electric overburden drills, three D25K Drilltech coal drills and numerous smaller earthmoving machines. New Vaal also operates a washing plant, where the coal is crushed, screened and, if required, sent to the dense medium separation plant, which consists of two large Drewboy washing vessels, 7 m in diameter, containing a mixture of magnetite and water. The heavier stone sinks and is removed back to the mine, while the coal is skimmed off the surface by the rotating paddle wheel and joins the crushed coal as it is transported to the stockyard by a system of conveyor belts.

Future prospects: The mine is currently at full production as per contract. The improvements made by the Lethabo power station in achieving availabilities of above 90% could enable the station to burn more than 16,7-million t/y, which would require higher production output from the mine.

Controlling company: New Vaal Colliery is an Anglo Coal mine, a division of Anglo Operations, a member of Anglo American.

Unique features: The mine is unique in many ways and is situated in close proximity to major conurbations. Subsequently great detail is paid to rehabilitation and environmental control.