Asymmetric distribution in twin screw granulation.

Area of Science:

• Chemical Engineering
• Materials Science
• Process Intensification

Background:

• Granulation is a key process in pharmaceuticals and chemicals.
• Controlling granule uniformity is essential for product performance.
• Twin Screw Granulators (TSG) are widely used but their internal flow dynamics are complex.

Purpose of the Study:

• To investigate material distribution and flow asymmetry in TSG conveying zones.
• To understand the impact of flow asymmetry on granule nucleation and uniformity.
• To identify critical parameters for optimizing the granulation process.

Main Methods:

• Positron Emission Particle Tracking (PEPT) was used to measure transverse asymmetry.
• Material distribution and liquid distribution were analyzed as a function of fill level.
• Granule formation mechanisms were studied.

Main Results:

• Flow asymmetry is inherent to TSG geometry and fill level.
• Low fill levels result in high flow asymmetry, negatively impacting granule nucleation and uniformity.
• Non-uniform wetting due to flow asymmetry leads to heterogeneous final products.

Conclusions:

• Fill level is a crucial control factor for achieving uniform wetting and consistent granule quality.
• Optimizing TSG screw configuration is necessary for secondary granule growth.
• Understanding fill-dependent flow regimes is key to controlling granulation mechanisms.