Characterization of red mud aggregate populations generated under shear conditions

CIM Bulletin, Vol. 95, No. 1062, 2002

M.J. Gagnon, G. Simard, A. Charette, G. Péloquin

In the Bayer process, flocculants are introduced in the feed well to enhance the aggregation of red mud particles. To gain a better understanding of the flocculation process taking place in the feed well, shear-induced flocculation was achieved using concentric rotating cylinders (Couette system). Our previous work has shown the effect of the shear rate on the aggregate’s settling rate and on residual turbidity of the Bayer liquor. In this study, the data demonstrated that the aggregates at selected shear levels appear as a population with a widespread size distribution. By using an imagery apparatus, it was possible to measure the size, the shape, and the sedimentation velocity of the larger red mud aggregates. Marked differences were noticed in the characteristics of the aggregate populations obtained under various shear conditions.

Keywords: Flocculants, Aggregates, Shear conditions, Red mud particles