Fluid-bed coater modifications and study of their influence on the coating process of pellets

Abstract

Objective: In this study, different modifications of bottom spray fluid-bed coater with draft tube inserted were characterized and evaluated. Materials and methods: After coating the neutral pellets with polymeric solution comprising coloring agent pellet batches were characterized for coating variation, yield and degree of agglomeration. Results: Funnel-shaped distribution plate was found to improve process yield and decrease the degree of agglomeration at selected values of process parameters, whereas coating uniformity was worse in all cases when compared to conventional Wurster chamber. Results of the coating chamber with the swirl airflow generator indicate more uniform deposition of the coating material and in some cases an improved process yield and decreased formation of agglomerates when compared to conventional Wurster chamber. In series of experiments using Wurster chamber, having tangentially oriented air intake slots, which enabled introduction of air above the distribution plate, coating layer was more uniformly deposited on the pellet cores and formation of agglomerates was lower compared to the results obtained in a conventional Wurster coating chamber. Conclusion: Modifications of Wurster coating process by introducing swirling air motion within the draft tube or by introduction of air above the distribution plate have at selected values of process parameters resulted in reduced per-particle coating variation, degree of agglomeration and improved process yield.

Keywords::

• Wurster chamber
• swirl-flow
• funnel-shaped distribution plate
• air intake slots
• coating variation
• degree of agglomeration
• process yield

Acknowledgments

The authors acknowledge the manufacturing of coating process chamber and other modified elements from the Brinox Process systems d.o.o., Slovenia.

Declaration of interest

This work was partly funded by the European Union, European Social Fund. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.