After the concentrate has been appropriately ground in an IsaMill (i.e. P80 of <12 micron), the slurry is then leached in agitated tanks, or Albion Leach Reactors.
These reactors are connected in series, with a launder system that allows gravity flow of the slurry through the continuous leach train. All Albion Leach Reactors are fitted with bypass launders to allow any reactor to be isolated from service for periodic maintenance.
Oxygen gas is injected into the base of the Albion Leach Reactor using supersonic velocity injection lances. Coupled with a high power reactor mixer, this maximises oxygen gas dissolution (oxygen mass transfer rate), plus reactant distribution.
The Albion Leach Reactor is designed to operate at close to the boiling point of the slurry. The temperature of the leach slurry is set by the inherent heat released by the exothermic (heat-generating) chemical reactions. No external heat source is necessary.
Further, no cooling is required. Excess heat generated from the oxidation process is removed by the humidification of the vessel off gases (latent heat losses). The maximum leach temperature is typically 94°C. The design oxygen capture efficiency is 85%.
The Albion Process oxidative leach has three primary control parameters:
Albion Leach pH: Leach pH is continuously regulated using an alkali slurry to neutralise the leach acid products.
Albion Leach Density: Slurry density is controlled through the addition of process water.
Albion Leach Oxygen Gas Addition: Oxygen addition is regulated according to each Reactor’s oxygen consumption (rate of reaction – oxygen demand).