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Wall build up in spray dryers

Hassall, Guy (2011)
Eng.D. thesis, University of Birmingham.

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Most granular laundry detergents are manufactured through spray drying. One drawback of this process is wall build-up, which negatively effects process operation, safety and product quality.

Macro and micro-scale observations showed the amount and micro-structure of deposits changed significantly across the dryer. These changes were linked to changes in particle
properties during drying. Measurements of deposition ranged from 1 - 10 kgm-2, or 2 - 10% of the total slurry sprayed, depending on location, operating conditions and slurry/powder properties. Wall deposition appeared to be time dependent.

Wall deposition was broken down into two critical steps; collision frequency, describing how many and how often particles hit the wall and, collision success rate which describes particle’s behaviour upon contact with the wall. Collision frequency was investigated using Particle Imagine Velocimetry (PIV) to measure both fluid and particle dynamics. Finding both to be time dependent, and to vary with position and operating conditions.

To investigate collision success rate, particle physical and mechanical properties were studied, revealing mutual dependence of all properties on both formulation and particle size. Impacting these particles at a range of velocities and angles found that the fraction of particles that broke ranged from 0 - 100% and restitution coefficients from 0.1 - 0.8.

Type of Work:Eng.D. thesis.
Supervisor(s):Simmons, Mark J. H.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemical Engineering
Subjects:TP Chemical technology
Institution:University of Birmingham
ID Code:2945
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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