P. Lotz, J. van der Merwe, S. Mogashoa, S. Flatman, and R. Imhof


Gold ore processing relies, among other criteria, on the efficient oxidation of not only the target metal, but also components inhibiting this crucial step, such as iron- and sulphurbased compounds. The associated oxygen mass requirements can be substantial and form a considerable part of the operational cost where this is the case.

The Aachen High Shear ReactorTM, originally designed to enable efficient high-level oxygen mass transfer from gas to liquid phase in the treatment of refractory gold ores, has by now found many applications where substantial process optimization targets have to be met.

With many of the easy-to-process reserves depleted, the remaining gold ores often have associated problems of cyanidable gold losses, slow leach kinetics, and high reagent consumptions. The endless pursuit of higher throughput to compensate for declining gold prices in recent times has only served to exacerbate these issues.

The Maelgwyn Aachen technology has been developed and deployed successfully in a range of gold mining applications to address these problems and has now, in addition to its original application to refractory flotation concentrate, found significant industry uptake into normal oxide cyanidation circuits.

This paper describes the journey from laboratory test work to full commercialization of Aachen reactors. Examples of work conducted to identify the envisaged level of shear, mass of oxygen, and general process conditions to maximize the potentials for a range of different ores and applications are provided. Early-stage economic evaluations include the identified benefits, which are then offset against the inputs of power, oxygen, and rental cost. A favourable balance typically leads to a trial phase on-site with a given scope of technology deployment. Data collection to support or validate the conclusions based on laboratory work forms part of final acceptance, and examples are provided. Finally, data from selected operational sites across Africa is presented demonstrating the ability of the Aachen reactor to assist with realizing hidden potentials in reagent savings, gold recovery, or throughput increases.

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