Importance of Synthetic Flocculants in Alumina Industry

Abstract

In the Bayer's process of alumina production, separation of mud residue front the liquor plays on important role. Throughout Alumina production process additives are used at one stage or the other, flocculant being one of the additives. Till 70's natural flocculants were used in the operations. Starch, guar gum, wheat bran etc. were used for the purpose of settling of red mud and to attain increased solidl/liquid separation rates. Slowly transformation has taken place from natural flocculants to synthetic flocculattts for a variety of advantages such as improved settling rates, improved liquor throughput, high underflow consistency,improved liquor filterability, reduced organic load etc. They also control the physical and chemical properties of the Bayer process streams during the operation- Synthetic flocculattts are polymers of acrylamide & polvac rylate etc. the molecular structure of which is an important factor to obtain the desired flocculation effect in the process liquors. Depending on the Bauxite quality and the process technology adopted the selection of flocculant varies from plant to plant. This paper deals with different types of synthetic flocculants available, their usage in Alumina industry.