JOHANNESBURG (miningweekly.com) – Three major projects completed by surface gold mining company DRDGold are expected to boost the fortunes of the company’s Ergo plant on the East Rand.

The three projects made up the bulk of the company’s capital spend of R125.9-million in the 12 months to June 30.

Providing greater plant stability and efficiency and helping to lower costs is the 4L50 slimes dam reclamation project, which is ramping up to 450 000 t a month.

This four-year-life project provides access to 20.5-million tonnes of material with a grade of 0.256 g/t.

The second project is the conversion to a zinc precipitation process at Ergo, which replaces the far slower and more expensive electrowinning process.

Zinc precipitation does in three hours what electrowinning does in 18 hours, providing a R2-million to R2.5-million cost saving through greater speed and less use of caustic soda and cyanide.

The third project is the installation of two 60 000 t/m ball mills from the company’s reclaimed Crown operation, which have been refurbished at a cost of R41-million.

These enable the company to process higher-grade sands that provide higher margins.

“We’re really looking forward to those three projects making Ergo more stable and, ultimately, keeping the cost line below the revenue line,” DRDGold CFO Riaan Davel commented to Mining Weekly Online.

The change is providing a vast improvement on where the company was 18 months ago.

“It’s really all about making sure that we consistently deliver the right material at the right density, the right rate, the right composition and at the right time into the plant and this is certainly making a contribution towards that,” DRDGold CEO Niél Pretorius told investors, analysts and media at the company’s presentation of latest results.

The zinc precipitation plant brings with it greater optionality and volume throughput headroom. “I personally like the fact that you can batch treat every consignment and it also has the advantage of cost saving, so we’re hoping to see the upside of that also coming through. The initial indications on the zinc precip are very much in line with our expectations and targets,” Pretorius said.

The two ball mills that became available following the closure of the Crown plant, where clean-up work is described as being nothing short of spectacular, allow the company to take in high-grade sand material scattered across the East Rand, and free up the City Deep circuit to process the remaining sand material in and around the central Johannesburg area.

“It’s surprising to see how a little bit of high grade material can improve the average grade of the entire throughput," said Pretorius.

This dovetails nicely with the Knights plant reaching the final stages of its life in the next few years and positions Ergo very favourably to insource external sand materials scattered around the East Rand that landowners want to get rid of to avoid environmental risk.

Targeted will be 12-million to 15-million tonnes in that area to improve margins.