EK Dewatering at DeBeers Diamond Mines

DeBeers Diamond Mines in Kimberley, South Africa are using Electrokinetic to optimise their belt press dewatering.

The Results:

• Input 50% dry solids slimes
• Output 75% dry solids cake
• 49% (by volume) water recovery
• Stackable cake
• Transportable by conveyor
• 40-60% reduction in power consumption
• Significant reduction in carbon footprint

In the mining industry, the recovery of metals and minerals from rock often requires that the ore or host rock be crushed and ground down to a very fine texture in order to release the minerals being sought. The industry therefore produces huge quantities of fine grained mineral sludges or tailings.

EKG may be used to effect electroosmosis or electrophoresis on sludges and tailings depending on their consistency. Electrophoresis works in liquid suspensions, such that solid particles move under the action of a DC voltage, aggregate and settle out from suspension. In some instances, there is a transition from electrophoresis to electroosmosis during treatment as the solids content rises and the material becomes less like a suspension and more like a soil.

EKG has been used to accelerate the settlement of solids from liquid suspensions and to increase the rate of consolidation of thickened tailings pastes. The liquid suspensions were generated from diamond mining operations in South Africa. The mineralogy of the waste tested was a mixture of clays including montmorillonite and very finely divided quartz. The problem with these wastes is that the materials are so fine that there is effectively zero settlement of suspended particles even after several months. Diamond mine tailings can be very fine grained with >80% of the material being finer than 1 mm. The initial solids content of the slurries was approximately 1.3%. The use of EKG resulted in a very rapid settlement of the materials. The photograph below shows a field trial underway to dewater thickened tailings pastes using electroosmosis.

Large scale laboratory data illustrate the ability of EKG to induce settlement by a mixture of electrophoretic movement and pH related adjustment of colloid structure. In essence, anodes became coated in solids due to electrophoretic migration and when the pH reached a certain level the remaining suspension cleared rapidly.

Field trial using electrokinetic prefabricated vertical drains to further dewater thickened mine tailings. The cathode is situated in the centre, surrounded by anodes.

 

applications > dewatering > mine tailings