Modern Mining July 2018

IRON ORE

south, with an average width of 2,5 km and a maximum width of 5 km. The current depth is 275 m but it will go down to 400 m by the end of the mine’s life. So vast, in fact, is the pit that it has been divided into two separate opera- tions, the North and South mines, each with its own manager. The single biggest activity at Sishen – which, in 2017, produced 31 Mt of iron ore for export through Saldanha Bay – is the loading and hauling of the waste and ore. Briefing the media party visiting the mine on the scale of this oper- ation, Sishen’s GM, Mapikwa Mobwano, said it accounted for around 65%of costs and required a huge mining fleet. This consists of 13 primary shovels, the biggest being three 109‑tonne P&H 4100 XPCs (each capable of picking up 109 tonnes in a single scoop), and 98 trucks, 36 of them 327-tonne capacity Komatsu 960Es and the balance Komatsu 860Es, each with a payload of 254 tonnes. The trucking fleet is smaller than it was at the end of 2015, when it numbered 136 units. As Mobwano explained, a programme of load and haul efficiency improvements – involv- ing, among other things, a redesign of the pit, a revamped shift system and improved blasting – has seen a 62 % improvement in productiv- ity, allowing the smaller number of machines on site to handle more material. Detailing the gains, he said the P&H 4100 shovels were han- dling twice as much material per day per shovel while the Komatsu 960Es were transporting 1,6 times as much material per day per truck. Shift change duration had been reduced by 88 % while the DOH (Direct Operating Hours) of the trucks had increased by five hours per day. Reviewing the processing operation, Mobwano said Sishen operated three plants:

a capex of R360 million is currently under construction and will be commissioned in the fourth quarter of this year. The modular plants are based on Ultra High Density Media Separation (UHDMS) technol- ogy, which Kumba and Exxaro (one of Kumba’s shareholders) have played an important role in pioneering. Kumba believes that full imple- mentation of UHDMS – which allows low grade material to be economically benefici- ated – has the potential to increase Sishen’s

Sishen is one of the largest open-pit operations in the world, moving well over 200 Mt of material a year. Launching a drone. Routine tasks which were traditionally carried out by surveyors – for example, measuring the volume of waste dumps and stockpiles – are now being undertaken using drones.

the DMS plant, commissioned in 1975, which treats the mine’s high Fe content ore; the jig plant, which came on line in 2007 and is designed to process lower grade reserves; and the modular plant, con- structed in 2014, which processes the jig discard. Typically, the DMS plant, which has a yield of between 78 and 86 %, accounts for 18 to 18,5 Mt/a of Sishen’s final product while the jig and modular plants – deliver- ing yields of between 55 and 65 % – are responsible for a further 11 to 11,5 Mt/a. A sec- ond modular plant involving

July 2018  MODERN MINING  31