SELECTION AND OPTIMIZATION OF SYNTHETIC FLOCCULANT FOR HIGH RATE DECANTERS (DEEP CONE THICKENERS)

Raghavan, P.K.N., Bamrah, H., Kshatriya, N.K. and Dasgupta, S.

Synthetic flocculants have come to play a prominent role in improving the operation of various systems in Alumina Refinery. They are used for improving settling and filtration characteristics of mud in settlers, washers and thickeners prior to disposal, and also to improve overflow liquor clarity and mud compaction. This paper describes the results of the Laboratory scale trials of various synthetic flocculants and establishes the best Flocculant for the Deep Cone Thickener (DCT). Preliminary screening tests were conducted for selection of the flocculants that gave best results with respect to good quality flocs, rapid settling rates (in the range of 10-15m/h) and better mud compaction. The screened flocculants from reputable suppliers were then assessed for suitability under plant conditions. The flocculant trails have shown that the flocculants play a crucial role in the mud dewatering. Flocculated red mud was observed to have better filterability, lower cake moistures and lower solid losses in filtrate with appreciable reduction in soda loss through the mud. A comparison of the experiments for a similar trial done for a conventional settler is also given.