Title page for ETD etd-05052005-095030


Document Type Doctoral Thesis
Author Kornelius, Gerrit
URN etd-05052005-095030
Document Title The design of electrostatically augmented moving bed granular gas filters
Degree PhD(Chemical Engineering)
Department Chemical Engineering
Supervisor
Advisor Name Title
Prof U H J Grimsehl Committee Chair
Keywords
  • granular beds
  • moving granular beds
  • filtration efficiency
  • electrostatic augmentation
  • re-entrainment
  • gas filtration
Date 2004-04-22
Availability unrestricted
Abstract
Granular gas bed filters have been used in industry for a considerable period and mathematical descriptions of dust capture have allowed rigorous design of static beds. Provision for bed movement and electrostatic augmentation, which allows much thinner continuous beds to be used, requires adaptation of design methods for these phenomena.

Design methods that allow for this are developed for a cross-flow bed with vertical bed movement and a number of granule and dust types. Direct current charging is applied to the bed itself and to the particles before they enter the bed. In the case of electrostatic augmentation, it is shown that simple models of spherical particles describe the mechanism adequately. The advantages of pre-charging dust particles before they enter the bed are indicated by calculation and proved experimentally. Parameters to describe the enhancement of filtration efficiency by the collected dust are obtained experimentally.

It is shown that the factors controlling re-entrainment vary with particle size. For the dust particles less than 1,5 micrometers in size, re-entrainment is linked closely to the electrostatic capture mechanism which is dominant in that size range. For particles approaching 10 micrometer, re-entrainment can be neglected as the impaction efficiency, which is dominant for particles of this size and larger, approaches unity. A complex situation exists between these particle sizes as the magnitude and predominance of capture mechanisms in this region are determined by a number of operational parameters.

It did not prove possible to develop predictive equations for re-entrainment efficiency using the results of this study. A number of heuristics are however developed that allow rational design by the use of the empirical parameters found, and that will be valid for the range of parameters used in this work.

2003, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Kornelius, G 2003, The design of electrostatically augmented moving bed granular gas filters, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-05052005-095030/ >

H633/ag

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