Improved viscous slurry agitation for minerals processing

• We summarised improved agitation technology developed by CSIRO.
• Showed methods to improve mixing, solids suspension and reduced scaling for viscous slurries.
• Found swirl flow found effective for Re > 500 even for viscous non-Newtonian slurries.
• We implemented many agitation improvements in the minerals industry.

A review is presented here outlining design improvements for agitated tanks as developed in CSIRO’s laboratories, which have solved practical problems in minerals processing operations involving viscous slurries. Depending on Reynolds number, there are a range of design options which can be employed to improve the mixing technology in general. These include optimizing impeller spacing and pitch angle. Swirl flow via removal of baffles can be employed for Re > 500, even for viscous non-Newtonian slurries with a yield stress. These agitator design improvements could be used to reduce stagnant zones, increase wall velocity and reduce sedimentation depth, with the same power input as original designs. Significant industrial benefits include reduced growth of scale, reduced agitator sedimentation bogging risk and improved reagent mixing. These improvements have been demonstrated by many full-scale implementations in large minerals processing tanks over the last 20 years. Radical design concepts including shafts installed at an angle or offset have also been suggested for mixing high viscosity fluids more efficiently.