(January 2014)

Maelgwyn Mineral Services (MMS) is pleased to announce its largest ever sale of Aachen Reactors to date. The order for eighteen REA 450 reactors for a new gold mine in the Democratic Republic of the Congo now brings the total number of reactors supplied by MMS to over 100. The reactors are to be used for Aachen assisted leaching (AAL) and also for cyanide destruction using the MMS CN-D process.

The Aachen reactor is basically a highly efficient mass transfer device developed out of the experience with Maelgwyn’s Imhoflot flotation technology. The unit can be used for any application where it is required to intimately mix a gas with a liquid but has been found to be particularly suitable for gold leaching applications where it is required to boost the dissolved oxygen levels of slurry either prior to, or during the leach reaction. Historically in many operations this has been done by various types of lance arrangements and their derivatives. However lances by their very nature tend to be very inefficient resulting in large oxygen bubbles and high oxygen consumptions. A second drawback of lance based systems is that they fail to address the problem of surface passivation from oxidised species which can retard the leach dissolution process .The Aachen reactor in contrast is able to produce significantly higher dissolved oxygen levels whilst also introducing an element of shear to clean up mineral surfaces. The net benefits of this include:

  • Accelerated leach kinetics
  • Reduced cyanide consumption
  • Lower residue grades
  • Improved oxygen utilisation

The same reactors are also used in a more aggressive role where partial sulphide oxidation is required for refractory flotation concentrates. This role is normally as part of the Leachox process and when combined with ultra-fine grinding can significantly increase gold recovery for these refractory flotation concentrates through partial oxidation of the sulphide matrix.

Many gold mining operations begin to experience problems with declining recoveries as their mining plan progresses from “free milling” oxide ore to more refractory sulphide minerals. The phased implementation of Aachen Reactors can help to successfully manage this transition and mitigate declines in recovery.


Aachen reactors at top of a gold leach tank