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Modeling of Residence Time Distributions of Twin-Screw Extrusion Processes Considering Various Screw Types
Vincent Kimmel1,2, Dario Zöllig1, Werner Hoheisel3
1Laboratory of Solids Process Engineering, Department of Biochemical and Chemical Engineering, Technical University Dortmund, Emil-Figge-Str. 68, 44227 Dortmund, Germany.
Pharmaceutics
|July 28, 2026
Summary
This study quantifies how different screw elements impact residence time distribution in pharmaceutical hot-melt extrusion. Results show residence time is mainly affected by volume flow, not pressure, aiding process optimization.
Area of Science:
- Pharmaceutical Sciences
- Chemical Engineering
- Process Analytical Technology
Background:
- Hot-melt extrusion (HME) is a key pharmaceutical manufacturing process.
- Residence time is a critical parameter influencing drug product quality attributes like content uniformity and bioavailability.
- Understanding the impact of screw element design on residence time distribution is vital for process control and optimization.
Purpose of the Study:
- To investigate and quantify the influence of various screw element types on residence time distribution in pharmaceutical hot-melt extrusion.
- To characterize the impact of conveying and kneading elements on the axial mixing performance during HME.
Main Methods:
- Utilized a co-rotating twin-screw extruder (28 mm screw diameter) with different conveying and kneading elements.
- Performed tracer experiments to measure concentration-time profiles using inline UV-Vis spectroscopy.
- Applied the Reitz two-compartment model for mathematical description of residence time distribution data.
Main Results:
- Residence time distribution was found to be primarily dependent on volume flow and independent of pressure across all tested screw types.
- Developed screw-type-specific dimensionless parameters to quantify axial mixing performance and residence time effects.
- The derived parameters provide a quantitative measure of screw element influence on HME processes.
Conclusions:
- The study successfully quantified the influence of diverse screw elements on residence time in pharmaceutical hot-melt extrusion.
- Dimensionless parameters, including mixing volume and axial dispersion coefficient, effectively characterize screw element impact.
- Findings align with and quantitatively support existing literature descriptions of HME processes.
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