Numerical Study of Flow Through a Reducer for Scale Growth Suppression
- Publication Type:
- Thermofluid Modeling for Energy Efficiency Applications, 2016, pp. 119-148
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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 being 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. It is common knowledge that, if the particles approach the wall at right angles, the chance to cross the laminar sub-layer to accumulate scale on the solid surface increases. The components (stream-wise (. u'x) and cross-stream (. u'r)) of the fluctuating velocity play a critical role in whether the potential for scale formation is increased or suppressed.In this chapter, a numerical study using the Finite Volume Method to analyze the fluid dynamics behavior of water as it flows through a concentric reducer used in the Bayer plant is presented. The simulation results show a significant variation of the stream-wise (. u'x) and cross-stream (. u'r) components of the fluctuating velocity as flow passes through the concentric reducer. In the reducer, the cross-stream (. u'r) component is greater than that at the walls of the straight pipes connected to the reducer. The variation of the cross-stream component of the fluctuating velocity is believed to be accountable for the increase in scale deposition at the reducer section.
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