The effect of pH on the local and average filtration properties of a bauxite residue slurry

T. Kinnarinen*, A. Häkkinen, Lappeenranta University of Technology, Finland; H. Theliander, T. Mattsson, Chalmers University of Technology, Sweden

The influence of the slurry pH on the characteristics of a topical unit operation, pressure filtration of bauxite residue slurries, was investigated in this experimental study. The primary aim of the pH adjustment was to mimic an industrial bauxite residue neutralization process, which causes precipitation of aluminate off from the liquid phase. In all of the investigated cases, the pH adjustment was performed with hydrochloric acid. The experiments were carried out by using two types of pressure filters, a Nutsche filter unit used for the acquisition of average filtration data, and a piston press used for measuring local cake characteristics. The Nutsche filter was used to separate the bauxite residue slurry with a pH of 13.3 and 11.0 at three different filtration pressures (300, 450, 600 kPa), while the piston press was operated under a constant filtration pressure of 1200 kPa and with a wider pH range (13.3, 11.0, 7.0). The average particle/agglomerate size increased as the pH was reduced, however, the width of particle size distribution increased as well. Based on the average cake properties, it could be concluded that...

Session: L14 - Slurry Pretreatment by Shearing, Classification, pH-shift
Day: 15 March 2018
Time: 13:00 - 14:15 h

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