Abstract

The objective of this study was to assess the mixing performance of a horizontal paddle blender for mono-disperse and bi-disperse particles. The assessment was performed through the application of the Discrete Element Method (DEM) simulations, experiments, and Analysis of Variance (ANOVA). EDEM 2.7 commercial software was utilized for the mono-disperse simulations while LIGGGHTS(R)-PUBLIC 3.3.1, an open source software, was used for the bi-disperse simulations. DEM models were validated with experimental data. Simulations were performed to explore the effect of impeller rotational speed, vessel fill level, particle number composition, and particle loading arrangement on mixing quality defined by the Relative Standard Deviation (RSD) index. The flow pattern and mixing mechanisms were examined through granular temperature, particle diffusivity, and Peclet number. The impeller rotational speed was the most influential parameter on the mixing performance of mono-disperse particles. The particle number composition was the dominating parameter on the mixing quality of bi-disperse particles

Highlights

  • The mixing kinetics and flow patterns of non-cohesive, monodisperse, spherical particles in a horizontal paddle blender were investigated using experiments, Analysis of Variance (ANOVA), and discrete element method (DEM)

  • The validated Discrete Element Method (DEM) model was utilized to examine the effects of three impeller rotational speeds i.e. 10, 40, 70 RPM, three vessel fill levels defined as the volume fraction of mixture bed to the vessel volume i.e. 40, 50, 60 %, and the particle loading arrangement of the mixing components defined as Top-Bottom and Front-Back relative to the front view of the vessel on the overall mixing quality quantified evaluated by the Relative Standard Deviation (RSD) mixing index

  • This conclusion is in good agreement with the results obtained in the mixing kinetic section, where an increase in impeller rotational speed resulted in higher chaotic motion of particles which in turn produced lower RSD

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Summary

Chapter 1: Introduction

Powder mixing is instrumental to a variety of industries including chemicals, food, cosmetics, mining, agriculture, plastics, and pharmaceuticals [1]. The objective of this study was to extensively investigate the mixing performance of a horizontal laboratory-scale agitated paddle blender by investigating the mixing kinetics, flow pattern and segregation mechanism of mono-disperse and bi-disperse particles. This was done by implementing experiments, ANOVA technique and DEM simulations. Chapter five and six summarize the results of the mixing kinetics, flow pattern of mono-disperse and bi-disperse particles in a horizontal paddle blender by using experiments and DEM simulations. Chapter seven draws conclusions and presents recommendations for future investigations based on the results obtained from Chapters five and six

Chapter 2: Fundamentals of powder mixing and literature review
Mixer classification and mixing mechanisms
Paddle and Plow mixers
Discrete Element Method (DEM)
Chapter 3: Specification of experimental set-up
Experimental method for mono-disperse investigation
Computational method for mono-disperse investigation
Introduction
Model validation
Mixing Kinetics: effect of operating parameters on mixing performance
Effect of impeller rotational speed (RPM)
Effect of vessel fill level
Effect of particle loading arrangement
Analysis of Variance (ANOVA)
Granular temperature
Particle diffusivity and Peclet number
Mixing kinetics
The effect of particle number composition
The effect of operating parameters for 50% 3 mm – 50% 5 mm bi-disperse mixture
Diffusivity coefficient and Peclet number
Chapter 7: Conclusion and recommendations
Bi-disperse investigation
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