SISHEN IRON ORE MINE

ISCOR's Sishen Mine was established in 1953 and is situated in the Northern Cape approximately 280km north-west of Kimberley. It is one of the seven largest open cast mines in the world with an open pit of approximately 11km long, 1.5km wide and almost 400m deep.

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Mining is undertaken by almost 4 000 employees in three 8-hour shifts, six days per week. The crushing and sorting plant is capable of processing in excess of 30 million tons of raw ore per annum which in turn yields 25 million tons of high grade hematite iron ore (1997). Approximately 6.8 million tons of the processed ore is used locally by ISCOR, while the remainder is exported to various parts of the world via Saldanha Bay on the west coast near Cape Town. China is currently the largest market for the South African ore, although British Steel is the largest single customer.

The ore is carried from the pit to the crushing plant using up to 70 of the largest trucks in the world, with capacities of between 150 tons and 170 tons each. (see photo). The trucks are diesel powered for normal use but also have pantographs which allow them to make use of electrical power to travel uphill fully laden using electrical motors. The ability to switch from diesel power to electrical power greatly reduces the fuel consumption and also increases their top speed from 10km/hr to 18km/hr on the steep uphill sections of the pit.

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The haematite ore at Sishen occurs in beds of varying thickness. Interbedded impurities, such as shales occur as bands in laminated ores, with iron enrichment at the contact zones. Since blast furnace operation is drastically influenced by fluctuations in the iron and potassium contents of the ore, it is necessary to either select only the high grade ore or the ore has to be upgraded to produce a final product with an iron content of approximately 65%. By using heavy-medium separation, ore reserves may be increased considerably through better utilisation of the medium and low-grade ores. A mixture of high and low-grade ores is therefore fed to the process plant, where waste material is effectively separated from ore. Without proper blending of the high and low grade ores, fluctuations in the iron content would be difficult to control and much of the lower grade ore would otherwise have to be discarded.

Although the Sishen Mine can utilise Vaal River water via the 700mm diameter Vaal-Gamakara pipeline, it currently makes use of groundwater abstracted directly from the mining area. Approximately 1.5 million m3 of water is abstracted monthly from the mine of which approximately 0.9 million m3 is used for the mining operations or the towns housing the mine employees and their families (Dingleton, Kathu and Sesheng). The remainder is distributed to other mines in the area including Hotazel and Olifantshoek via the Vaal-Gamagara pipeline. It is anticipated that the groundwater will gradually become depleted to such an extent that the Sishen Mine will eventually have to import water through the pipeline and will no longer be in position to export water.

Approximately 11 000 people stay in the towns (i.e 4 000 employees and their families) which are full self sufficient with schools, hospitals, shopping centres and sports facilities etc.

Several world records have been set at the Sishen mine including the largest single blasting operation where 7.2 million tons of rock were broken during a single blast in April 1981. The ore is usually transported to Saldanha by trains 2.3 km long comprising 210 wagons each carrying 85 tonnes of ore, ie a total of 17 850 tonnes per train. A train with 660 wagons recently set a new world record for the longest train and heaviest load from Sishen to Saldanha with a total load of 68 640 tonnes of ore and a length of over 7.5 km.

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