OBSERVATIONS ON EROSION PATTERNS IN BAYER SLURRIES

Celliers, O.C.

Slurry erosion damage in alumina refineries is predominantly caused by vortices and not by direct impingement, yet much of the wear characterisation of materials of construction is only available as slurry jet data, or dry sand rubber wheel abrasion data. Erosion patterns from different slurry streams in alumina refineries can be analysed to provide insight into the relative contribution provided by the different size fractions, and the type of slurry particles such as sand, iron oxide, clay, or hydrate, under different flow conditions such as sliding bed, direct impingement, turbulence and, in particular, vortices. Used in conjunction with CFD, this analysis of observed erosion patterns then provides a basis for the classification of the erosive conditions present at different refinery locations, and the best candidates for materials to be used to combat erosion; it also provides guidelines for materials development. In so doing we need to reconcile traditional measures to rank and characterise wear materials, with actual observed erosion patterns and field ranking of materials.

With the comparatively mild corrosion conditions present in the Bayer process, observations of erosion patterns in alumina refineries can be particularly useful for the development of a fundamental understanding of the effects of the physical attributes of a slurry on erosion, as the confounding corrosion component of the synergistic erosion-corrosion should be relatively small.