Gold recovery has been boosted and reagent consumption reduced through optimisation efforts by South African mineral processing and metallurgical testwork company Maelgwyn Mineral Services Africa (MMSA) using its Aachen High Shear Reactor technology.

The technology facilitates mass transfer by increasing gas dispersion in a process fluid or slurry, resulting in improved gas use and efficiencies, explains Aachen technology process manager Wiehan Botes.

He explains that typical applications are the leaching of gold ores with cyanide and chemicals, and wastewater treatment processes where substantial amounts of gases are required to be dissolved in fluids.

In comparison, the Aachen High Shear Reactor is efficient for high-rate oxidation of sulphides as the slurry (fluid stream) is accelerated at the gas addition point, increasing shear rates in the subsequent mixing zones.

The effectiveness of Aachen technology has been validated through rigorous testwork, demonstrating a potential to significantly enhance gold recovery while reducing reagent consumption.

Recent pre-oxidation tests on samples from a Ghana-based site, where two Aachen units are set to be deployed later this year, yielded “impressive results”, says Botes.

The ten-pass Aachen pre-oxidation test achieved an overall gold recovery of 89% after the carbon adsorption stage, marking an improvement of about 4% over the base case tests, which had an average recovery of 85.3%.

The same test also resulted in a significant reduction in cyanide consumption, with sodium cyanide use decreasing by 37%, from 1.62 kg/t in the base case, to 1.02 kg/t.

These enhancements boost economic returns for mining operators and contribute to more sustainable mining practices by reducing the environmental impact associated with excessive reagent usage, according to MMSA.

Overall, MMSA has been steadily expanding its Aachen installation base across West Africa, with 30 units already deployed in the region, some of which have been running for more than 15 years.

The company has recently added to this footprint with a new installation in Ghana in 2024, and another two units are slated for deployment at a Ghanaian gold mining site later this year.