Improving the dewatering performance of red sludge with alternative methods in Eti Aluminum Plant in Seydisehir, Konya province, Turkey

Recently, alumina demand has increased significantly due to the increment of usage area of aluminum in the world. One ton of red sludge on dry bases has come out as a bauxite residue in the course of 1 ton of alumina and 0.5 tons of aluminum production respectively. Especially the high liquid ratio significantly reduces the life of the red sludge dam used as a disposal area. In this study, alternative techniques have been investigated to improve the dewatering performance of red sludge in ETI Aluminum Inc. For this purpose, the vacuum rotary drum filter, decanter centrifuge, and filter press methods have been searched, and the effects on ETI red sludge dewatering properties have been obtained. The dewatering studies have been performed not only at the laboratory scale but also at the pilot scale to determine the optimum technique and to achieve the most efficient performance. As a result of dewatering the 30% solids red sludge with vacuum rotary drum filter, decanter centrifuge, and press filter methods, solids ratios of 48%, 65%, and 70% were obtained, respectively. While the amount of caustic in the red sludge produced by the present method was between 1.5 and 3%, the amount of caustic remaining in the cake was reduced to 0.22%, 0.15%, and 0.95%, respectively, by vacuum filtration, decanter centrifuge, and press filter methods. Thus, reducing the amount of caustic in the red sludge has reduced its negative impact on the environment, and a significant amount of caustic has been recovered.