Merensky and UG2 concentrator plants
Crushing/screening circuit: In the crushing/screening circuit the ore is crushed to reduce its size before it reports into the mill.
Milling: Merensky ore feeds into a fully autogenous mill (FAG mill). In the UG2 plant the crusher product feeds into a high pressure grinding roll crusher (HPGR) and this then goes into a primary ball mill.
Flotation: The circuit includes rougher cells, scavenger cells and cleaner columns. In the UG2 plant the secondary roughers consist of a bank of tank cells.
In the UG2 circuit, sparger columns act as a cleaner and help to produce a final UG2 concentrate at half the original chrome content while maintaining PGM recoveries.
Smelter and furnace operations
Commissioned in 1993, the smelter has a 15MW capacity. Key processes are drying, smelting and converting the concentrate. Concentrates brought in are blended in by a conveyor. Dried concentrate is pulverised and then stored in silos. The off-gases are cleaned in an electrostatic precipitator, where fine concentrates are recovered too.
The concentrate and flue dust are mixed with lime and then feed through to the day bin and into the furnace.
Inside the furnace electrodes provide heat. The lighter oxides float to the top as slag, and the more dense sulphides, which contain the PGMs, sink to the hearth as furnace matte.
The smelter at Zondereinde has for years treated Zondereinde's output and spare capacity has been filled with toll-treated third party concentrate. In line with the company’s expansion and Booysendal operations coming on stream, the smelter is being expanded, and a new furnace is being built to make provision for the higher volumes. Innovative design parameters allow the facility to operate as a pure UG2 furnace, apart from being a conventional smelter also for a combination of Merensky and UG2 concentrate. This new design comfortably accommodates the growth in UG2 mining.