A R27-million order for a turnkey crushing and screening plant for a new mine in KwaZulu-Natal reflects equipment manufacturer Osborn’s ability to deliver customised solutions that match customers’ requirements.
According to product sales manager Shane Beattie, the new plant features a unique process designed by Osborn to minimise fines generation in the production of calcite and lime. It has been supplied by Osborn to Umzimkhulu Industrial Holdings’ Rossmin open cast limestone mining operation at Port Shepstone, on the KwaZulu-Natal South Coast in South Africa.
“The plant was designed and installed to only produce two sized products: 80 mm +30 mm and -30 mm +10 mm. The -10mm is a by-product,” says Beattie. He reveals that the process is revolutionary in that a conventional crushing plant would be a jaw and cone configuration to crush down to a -80 mm product from a run of mine (ROM) of 600 mm.
“We supplied an Osborn modular 3042 jaw plant feeding into an Osborn modular 2340 jaw plant, then over an Osborn modular 6 x 20 triple deck screen, splitting the product into -80 mm+30 mm, -30 mm+10 mm and a -10 mm +0 mm. The primary reason for the two-stage jaw crushing process is to minimise the generation of fines (-10mm),” says Beattie, adding that this material cannot be used in the next stage and is a waste product.
Beattie says that Osborn’s pioneering process is more effective than the conventional separation process at other plants, where all the ROM material is crushed to -1mm and smaller, then flotation is used to remove the impurities. “This process requires lots of water and waste that is more difficult to manage,” he argues.
Umzimkulu and Rossmin will only process the high grade material, up to 99% calcite, Beattie states. “By only feeding the high grade -80+30 mm to the tertiary/quaternary plant and, the next stage being dry, will produce a higher yield per ton crushed,” he notes. “Since this stage is the most expensive part of the process, by only crushing the desired calcite, the operation will be able to dramatically reduce its cost per ton, and the capacity in this stage is utilised to its fullest potential,” adds Beattie.
Osborn also supplied the mine’s next stage with its imported high frequency screens, to cut at -2+1,2 mm, -1,2+0,8 mm, -0,8+0,4 mm and -0,4+0,075 mm.
“This is an extremely innovative process that enables us to screen out the -1,2 mm fraction. This is then sent to an air classifier, which removes the -0,075 mm from the -1,2 mm. The -1,2+0,075 mm fraction is then sent to the second 2624VM high frequency screen, a double deck 6’ x 24’ screen, to separate the -1,2+0,8 mm, -0,8+0,4 mm and -0,4 mm +0,075 mm fractions.”
