Laboratory modelling of erosion damage by vortices in slurry flow

Abstract

Erosion damage caused by suspended particles in slurries leads to production loss and on-going maintenance costs. Such damage is common in flow equipment used in slurry transport, including processing equipment in alumina refineries.CSIRO has been conducting research under AMIRA P931 “Multiphase Flow Erosion” projects from 2006 to 2013, under sponsorship funding support from Alcoa, BHP Billiton, Rio Tinto Alcan, Vale and Pentair Valves (Tyco Flow). CSIRO has a continuing focus on building knowledge and methods to improve prediction of the service life of flow equipment under erosion conditions, and to develop strategies to reduce erosion through altered flow design.Interestingly, none of the case studies requested by the industry partners involved simple impingement erosion or sliding bed erosion. The emphasis has been on solving erosion problems using the principles of the underlying multiphase fluid dynamics, which called for an in-depth treatment of non-uniform flows. Consequently the current study was very different from the usual treatment of erosion (which focuses on direct impingement simply because it is easier to model and measure) and instead addressed the much more common industrial problem of localised erosion.By using fluid dynamics modelling, experimental visualisation and quantitative measurements of erosion scars, several fluid dynamic mechanisms have previously been identified as causing severe erosion attacks. These included erosion by vortices, by flashing and by various non-uniform flows. Observations of accelerated wear have shown that vortex erosion is present in many flow geometries critically important in sponsors' plants, e.g. pipe work around a valve, protrusions in a pipe and many conventional engineering designs. This paper focuses on vortex erosion in a variety of flow situations and examines the fluid dynamics and consequent erosion.