Download the full-sized PDF of Aggregation and Sedimentation of Fine SolidsDownload the full-sized PDF



Permanent link (DOI):


Export to: EndNote  |  Zotero  |  Mendeley


This file is in the following communities:

Graduate Studies and Research, Faculty of


This file is in the following collections:

Theses and Dissertations

Aggregation and Sedimentation of Fine Solids Open Access


Other title
Fine particles
Differential settling
Type of item
Degree grantor
University of Alberta
Author or creator
Omidghane, Mehdi
Supervisor and department
Yeung, Anthony (Chemical and Materials Engineering)
Liu, Qi (Chemical and Materials Engineering)
Examining committee member and department
Sanders, Sean (Chemical and Materials Engineering)
Nikrityuk, Petr (Chemical and Materials Engineering)
Xiao, Huining (University of New Brunswick)
Department of Chemical and Materials Engineering
Chemical Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
In many applications, it is desired to separate unwanted fine particulates from a liquid by gravity settling. An efficient separation, however, will be feasible only if a combination of aggregation and sedimentation occurs. To understand the kinetics of such a process, a mathematical model that accounted for aggregation and sedimentation was developed. The simulation was based on Smoluchowski’s equation of population balance, with the collision frequency determined by Brownian motion and differential settling, while treating the aggregates as fractal objects as the particles collide and aggregate. One of the most important issues here is that aggregating systems, especially those encountered in particle technology and separation processes, often involve non-uniform particle distributions. Situations with evenly distributed aggregates are very rare in practice, but this continues to be the “default assumption” in many theoretical treatments. This study addressed this issue by developing a series of experiments and numerical model to properly account for non-uniform particle sizes and their spatial variations. Our results showed that the rate of settling could be improved significantly if the particles aggregated (the settling time may be reduced from hours to minutes). Experimentally, we showed that, depending on the strength of interaction between the particles, different settling regimes were observed. It was also observed that under certain experimental conditions, an initial ‘induction time’ appeared before the apparent onset of sedimentation. It appears that the particles required some ‘waiting time’ before commencement of aggregation. Our simulations showed that the observed ‘induction period’ may in fact be a kinetic phenomenon that was independent of the nature of the inter-particle forces (i.e. on the microscopic scale, the particles began to aggregate immediately without any delay). Our simulation showed that inter-particle attraction could significantly affect the rate of aggregation and sedimentation. Larger attractive forces also resulted in a perceptible clear liquid-suspension interface; as such forces diminished, the clear liquid-suspension interface became more diffuse and eventually appeared as a gradual concentration gradient. A novel approach was used to predict formation of this ‘mud line.’ We have also demonstrated that sedimentation kinetics are largely insensitive to the initial particle size distribution; an explanation for this observation is discussed.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication

File Details

Date Uploaded
Date Modified
Audit Status
Audits have not yet been run on this file.
File format: pdf (PDF/A)
Mime type: application/pdf
File size: 4421775
Last modified: 2015:10:22 06:03:07-06:00
Filename: Omidghane_Mehdi_201410_PhD.pdf
Original checksum: 22a9f9ebf563ef0a939e9c678082545c
Activity of users you follow
User Activity Date