REDUCTION OF SLURRY EROSION BY FLOW DESIGN

Graham, L., Wu, J., Short, G., Nguyen, B., Harris, D.

Particulate erosion increases costs associated with equipment repair and loss of production. The traditional solution to reduce erosion of slurry flow equipment has been to use wear resistant materials for construction, such as white iron with various hypereutectic alloys and carbides. An alternative approach is to design the geometry of such equipment to redirect particle flows and minimise the erosion impact. This fluid dynamics-based approach can be simple and effective for reducing erosion. The cause of the erosion and its solution is investigated through laboratory investigations and flow visualisation studies.

Once a cause of the erosion is identified, the flow geometry design can usually be changed to minimise the erosion effect. This paper presents laboratory measurements of erosion causes from a fundamental viewpoint. A few key fluid dynamic mechanisms were found to be related to formation of erosion “hot-spots”: vortex action, jetting and erosion in flashing conditions.

This paper will show that design changes can be developed, modelled and trialled in the laboratory before full-scale implementations. Many such fluid dynamic design changes to reduce erosion have been developed by CSIRO in collaboration with alumina industry technical experts. These modified designs have been implemented in several alumina plants and have remained in operational use for a decade. These include a solution to the erosion of cooling plates in heat exchangers at Rio Tinto’s Yarwun alumina refinery in Queensland, Australia in 2008. Another design change was developed through laboratory modelling to solve a localised wear problem on the bottom of a pressure vessel downstream of a positive displacement pump at the same site. Novel geometrical designs developed to reduce erosion on riser caps and vessel walls in flash tanks have also been investigated in the laboratory studies. These studies suggest that there are plenty of opportunities to reduce erosive wear in flash tanks and full-scale trials will be required to prove these novel designs.