Many slurry mixing tanks used industrially utilise baffles in order to generate the desired flow pattern for good mixing and particle suspension. These tanks have the disadvantage of dead zones which are prone to scaling. Conventional mixing tanks also require that impellers be placed closer to the tank bottom which can lead to burying of impellers in settled solids in the case of unscheduled power outages. CSIRO has developed an alternate approach (Swirl Flow Technology, SF) to tank design which dispenses with the baffles or any other internal structure such as draft tubes. The SF installations consist of a single impeller near the top of the tank at a suitable depth to eliminate splashing. This provides improved particle suspension and increases the flow velocity near the tank walls, leading to reduced scaling. Another benefit is that the impeller is not buried in the case of power outage, thus tanks are easily restarted and accessed from top, eg for repair and cleaning. A SF installation was developed for a neutralisation tank at the Fosterville Gold Mine which had scaling issues. Pilot-scale laboratory test work followed by a six month the site installation demonstrated: improved particle suspension compared with the conventional baffled tank as shown by less sanding; and a significantly lower scale growth rate, approximately 70% less than the conventional baffled tank after six months.
CITATION:Nguyen, B, Mills, S, Nash, A, Davoody, M, Harris, D, Mohanarangam, K, Bruckard, W, Graham, L and Wu, J, 2019. Swirl flow agitation for a BIOX neutralization process, in Proceedings World Gold 2019, pp 577583 (The Australasian Institute of Mining and Metallurgy: Melbourne).