Title page for ETD etd-06212011-163616


Document Type Master's Dissertation
Author Brink, Hendrik Gideon
Email deonbrink@gmail.com
URN etd-06212011-163616
Document Title Multi-Vortex distributor : effect on 2-D fluidized bed reactor performance
Degree MEng
Department Chemical Engineering
Supervisor
Advisor Name Title
Mr W Nicol Committee Chair
Keywords
  • pressure fluctuation analysis
  • Thompson model
  • Kunii-Levenspiel model
Date 2011-09-21
Availability unrestricted
Abstract
The influence of the distributor configuration on the mass transfer and bubble sizes in a 2-D FBR was studied for two types of distributor configurations:

  • A novel multi-vortex (MV) distributor with tuyéres directed vertically and horizontally at different heights.
  • A standard perforated plate distributor (baseline).

The ozone decomposition reaction over FCC catalyst was used as an indirect meas-ure of the interphase mass transfer in the bed. The ranged between 0.1 m/s and 0.35 m/s, with air as a fluidizing medium at ambient conditions.

The MV distributor displayed a significant improvement in the conversion cies (χmeasured / χPFR). For all velocities an improvement of between 0% and 30% was measured (average improvement of 14.7%). At Uo0.2 m/s the improvement distributed evenly about the mean improvement, with a minimum improvement of 10%.

The Uc for the respective distributors were determined using absolute pressure fluctuations (baseline distributor) and visual observations (MV distributor) and it was found that the Uc for the MV distributor was lower than that for the baseline:

  • Uc Baceline = 0.30 m/s.
  • Uc MV distributor = 0.25 m/s.

The decrease in Uc indicated that the MV distributor induces faster onset of turbulent behaviour in the FBR which negates interphase mass transfer limitations in the FBR.

The bubble sizes were measured visually and compared to a pressure signal decomposition technique. The bubble size growth for the MV distributor was estimated at .14 times that of the baseline.

Two models were compared to the experimental results, the Kunii-Levenspiel three-phase model and the Thompson generalized bubble-turbulent model. The fitting parameters showed that the mass transfer for the MV distributor is significantly larger than that of the baseline. In addition the MV distributor decreased the axial dispersion in the FBR as Uo → Uoo, which improved the reactor performance to that of an ideal PFR. This phenomenon was observed at Uo > 0.33 m/s.

© 2011 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:

Brink, HG 2011, Multi-Vortex distributor : effect on 2-D fluidized bed reactor performance, MEng dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-06212011-163616/ >

C11/9/142/ag

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