Numerical simulation of two-phase flow in a Wurster coating chamber and comparison with experimental results

• Computational fluid dynamic analysis of a Wurster fluid bed coater was performed.
• Volume fraction of pellets in the draft tube was measured using quick closing valve.
• Particle velocity was measured using a high speed camera.
• Pressure fluctuations in the draft tube were analyzed.
• A relatively good agreement between experiment and simulations was observed.

Pellet coating is commonly performed in a fluid bed coater such as a Wurster coater. Computational fluid dynamics (CFD) simulations and experimental measurements of laboratory-scale Wurster coating were performed. CFD simulations were performed in a 2D axisymmetric space using the two-fluid model. The effect of the Wurster gap and fluidizing airflow rate on gas–solid flow was analyzed in both simulations and experiments. Experimentally, the draft tube two-phase flow was evaluated by measuring the volume fraction of pellets within the draft tube and local particle velocities at the tube exit and by monitoring the local pressure drop fluctuations. A rather good agreement between the simulated and experimental results was observed and thus it can be assumed that this particular simulation setup represents a computationally reasonable tool that provides a valuable insight into the Wurster coating process due to the impact of two-phase flow properties on the process.

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