ISBN 978-3-8439-0279-3

978-3-8439-0279-3, Reihe Ingenieurwissenschaften

Ishaq Ahmad
Beneficiation of Bauxite by Washing Processes

131 Seiten, Dissertation Technische Universität Hamburg-Harburg (2011), Softcover, A5

Zusammenfassung / Abstract

Bauxite is the major source for alumina production in the Bayer process. Silica in the form of clay associated with the bauxite has a number of negative impacts in the Bayer process. Therefore, the bauxite beneficiation was carried out with the aim to increase alumina grade and reduce the silica grade of bauxite. On the basis of experimental investigation, proper cut size can be selected in order to set up a trade off between grade and recovery of alumina and silica. A low alumina to silica ratio clayey gibbsitic bauxite was processed. Washing was selected as the beneficiation technique for removal of clay from bauxite surface. Ultrasonic washing technique was developed for determining the potential of an industrial washing process and to observe the effect of washing of various size fractions individually. The results of the ultrasonic washing were used for the development of a washing matrix to model the washing process. Bauxite washing at industrial scale is usually carried out in a series of steps and the exact mechanisms of the washing process are not well understood. Therefore, the washing process was split in the laboratory such that the effects of the different washing mechanisms could be studied separately. It is concluded on the basis of experimental results that the retention time of bauxite inside the water is the dominating parameter for clay removal from the bauxite surface. Only moderate movement of the pulp is necessary to detach the fines from the particle surface. Additional energy input showed nearly no effect on the washing efficiency. No models are available in the literature for bauxite washing process; therefore, models were developed on the basis of the laboratory experimental data with the aim of determination of particle size distribution and the composition distribution, which are useful for the estimation of the grade and recovery of the alumina and silica at the required cut size. The models developed were validated for various cases of a bauxite washing plant and can be used for flowsheet simulation of industrial washing processes.