Modern Mining November 2017

PRODUCT News

Tharisa Minerals’ platinum mining opera- tion on the south-western limb of South Africa’s Bushveld igneous complex has boosted its mill circuit production perfor- mance by 36 % by replacing its original cyclones with Cavex® hydrocyclones from Weir Minerals Africa. Changing to the Cavex® hydrocyclones has allowed the mine to recover an addi- tional 98 ounces of platinum group metals Cavex® hydrocyclones boost recoveries at Tharisa (PGMs) each month, giving an additional annual revenue of some US$800 000 – almost R11 million. With this improved performance, Tharisa’s payback period for the cluster of new units was just 29 days. The Tharisa mine, in production since 2009, produces metallurgical grade PGM concentrate and chemical grade chrome concentrate from a shallow open-pit operation. It had been using conventional 510 mm flat-bottom cyclones fitted onto their secondary mill circuit cluster. However, according to the mine, these cyclones were cutting too coarse, were inefficient and were experiencing a low mass split to underflow.

Using the data supplied by the cus- tomer, Weir Minerals generated a mass balance simulation, highlighting the per- formance capability of its Cavex® 500CVX hydrocyclones. These units have a 360 deg laminar spiral inlet that reduces turbulence within the hydrocyclone. In an initial trial, Tharisa mine installed a single Cavex® 500CVX hydrocyclone on site, retrofitting the unit onto the existing competitor cyclone cluster. It then con- ducted a sample analysis, comparing the performance of the Cavex® hydrocyclone to that of the competitor cyclone. The data from this trial confirmed that the Cavex® unit outperformed the incumbent com- petitor’s cyclone. Once the results of the first trial were made available, the competitor was offered another trial opportunity to make adjustments that would improve its equip- ment’s performance. To do this, it modified one of its on-site cyclones by installing an angled conventional cone section onto the flat-bottom cyclone, intending to sharpen the cut point and improve efficiency. In a second sampling campaign under- taken by the mine, the performance of the Cavex® 500CVX hydrocyclone was com- pared with both the competitor’s original cyclones and its newly modified cyclones. The Cavex® unit again outperformed both competitor cyclone models, showing a significantly reduced level of +75 micron material reporting to the overflow. As a result of the tests, Tharisa decided to remove the competitor cyclones on its secondary mill 13-way cluster and replace these with Cavex® hydrocyclones. Rajen Govender, Weir Minerals Africa, tel (+27 11) 929-2701

The mine’s objective was to allow the secondary mill circuit to improve mass pull to the underflow and produce a much finer cyclone overflow material reporting to downstream flotation and a spiral cir- cuit. By providing a finer feed material to flotation and the spiral circuits, PGM and chrome recovery increases significantly. 900 t/h over 4,9 km, with an overall vertical climb of 35,0 m. This system is due to be in operation from 2019. As part of an additional expansion pro- gramme, Booysendal, in October 2017, further contracted Doppelmayr to design and construct a second RopeCon® to tie in with the first system, allowing transport of ore frommining modules in the north of the property. This RopeCon® system will convey 400 t/h over 2,8 km, with a vertical drop of

Cavex ® hydrocyclones retrofitted onto the exist- ing cluster on site. Second RopeCon® system for Booysendal

Booysendal Platinum, a subsidiary of Northam Platinum, is currently expanding mining capacity at its Booysendal mine. Key to the success of this expansion is the cost effective, reliable, safe and environ- mentally low impact transport of ore over topographically challenging terrain, from mining modules in the south of the licence area to the concentrator plant. To this end, Doppelmayr Transport Technology GmbH (Doppelmayr), headquar- tered in Austria, is currently constructing a RopeCon® system which will transport up to

160 m, and will operate from 2020. Doppelmayr, website: www.doppelmayr-mts.com

52  MODERN MINING  November 2017