Fluid flow chractericitics on scale deposition in a concentric reducer using CFD approach

Abstract

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Fluid flow phenomenon in a concentric reducer is modelled by computational Fluid Dynamics (CFD) approach to examine the role of fluid velocity in scale formation. Scale formation in alumina refineries is a common phenomenon and it occurs where supersaturated solutions are in contact with solid surfaces. It often leads to serious on-going technical problems and is a major cause of production loss due to equipment downtime required for descaling and cleaning operations. The scale formation mechanism in Bayer process equipment is complex and is not yet fully understood. Numerous researchers indicate that scale growth is strongly affected by fluid velocity while also influenced by a number of other factors such as the quality of bauxite ore, rheological properties of fluid, turbulence and inertia of suspended particles and adhesive property of particles. A numerical study using the Finite Volume Method to analyse the fluid dynamics behaviour of water as it flows through a concentric reducer commonly used in the Bayer plant is presented. The simulation results show a significant variation of the stream-wise (u′ ) and crossstream (u′ ) components of the fluctuating velocity as flow passes through the concentric reducer.