Picture: REUTERS
Picture: REUTERS

Northam Platinum will process 10-million tonnes of tailings that came with the purchase of the Aquarius Platinum Everest mine and concentrator plant, using the residue for not only financial benefits, but to prime the concentrator and to test a longer-term strategy at its Booysendal mining complex.

The tailings, with a content of about 18% chrome and 0.8g-0.65g of platinum group metals (PGMs) a tonne, give Northam the chance to restart the long-mothballed concentrator and to iron out ramp-up niggles, leaving it ready to process more than 150,000 tonnes a month of freshly mined Merensky Reef ore at an 86% recovery rate in 2019.

Analysts forecast the low-cost, energy-efficient tailings project could be a significant earner for Northam over a two-year period

The Booysendal mining complex is the jewel in the Northam asset portfolio, with its suite of shallow, highly mechanised mines, a brand-new concentrator to treat UG2 Reef, as well as the Everest mines and concentrator, which Northam plans to make a Merensky-only processing plant as it considers the potential to make the complex the source of 500,000oz of PGMs a year.

The R100m project to process the tailings dump in the renamed Booysendal South portion of the complex will occur in two stages, with chrome extracted first and tailings returned to the storage facility before being processed for a second time to extract PGMs. Booysendal’s chrome concentrate output will more than double from the current 300,000 tonnes a year.

It is too early to say what the additional PGMs would amount to, says Damian Smith, manager of mineral resources and projects at Northam. Whatever the PGM production is, it is not included in the forecast of more than 200,000oz of PGMs in 2018.

Analysts forecast the low-cost, energy-efficient tailings project could be a significant earner for Northam over a two-year period. Northam will treat the tailings while it builds a R500m, 4.76km rope conveyor that utilises a system that has trays running on wheels, with minimal maintenance requirements. The conveyor will bring Merensky from the central part of the property to feed the southern plant from February 2019.

The maintenance and operating cost of the rope conveyor worked out to 80c a tonne compared with more than R1.80 a tonne for a conventional conveyor belt and R14 a tonne for trucks.

The complex is divided into three areas, with the northern portion hosting a UG2 mine and a new Merensky mine, which all feed a concentrator in the central portion.

In time, Northam could add a R300m-R400m rope conveyor to link the northern Merensky mine to the rope conveyor feeding the concentrator in the south.

But the mineral revenue benefits aside, arguably more important benefits flow from the tailings retreatment project, Smith says, pointing out Northam is in the unique position of being able to treat a large tailings deposition before processing mined material to dial in the concentrator.

Northam intends treating up to 8-million tonnes of the 10-million tonnes, of which 3-million tonnes will be pumped into the old Everest mine as backfill, largely to reduce its environmental liability and create extra tailings capacity in an area where flat ground is scarce, but also to prove a concept.

The thinking is that by pumping the tailings underground, it will firm the pillars supporting the excavations, making the mine more rigid and allowing greater ore extraction in the future by possibly reducing the size of pillars, which lock up metal.

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