CFD simulation on flow and mixing process in different horizontal self-cleaning single-shaft kneaders

Abstract

The horizontal self-cleaning single-shaft kneader possesses excellent mixing performance and has many industrial applications in bulk polymerization, polycondensation and polymer devolatilization. Hence, the objective of this research is to investigate the hydrodynamics and mixing performance of different new types of self-cleaning single-shaft kneaders by using the finite element method (FEM) simulation and particle tracking technique. Both the distributive mixing process of randomly distributed material points between halves of kneaders and the local distributive mixing process of a cluster in selected positions were analyzed. The effect of kneader geometry structure on hydrodynamics and mixing performance was also analyzed. The FEM simulation were validated by using a small visual experimental device. There hardly exists the flow dead zone in the self-cleaning kneader. The area of region with high velocity magnitude increases with the number of dynamic kneading bars and decreases with the number of static kneading bars. The area with high shear rate increases with the number of both dynamic and static kneading bars due to small clearance. There exists the periodical intermeshing interaction between the static kneading bars on kneader wall and the dynamic kneading bars on rotating shaft. What counts is that the distributive mixing process and mixing efficiency can be enhanced and improved by the periodical intermeshing interaction.

Keywords

• Single-shaft kneader
• Computational fluid dynamics (CFD)
• Finite element method (FEM)
• Particle tracking
• Flow pattern
• Mixing