Experiments were performed at ambient temperature and pressure in a 127 mm inner diameter column with a 55% wt. aqueous glycerol solution, 6-mm spherical borosilicate beads and four gases - helium, air, carbon dioxide and sulphur hexafluoride - giving a 35-fold gas density range. The dispersed bubble flow regime was sustained to higher gas velocities and gas holdups for denser gases. This finding appears to be due to the reduction of the maximum stable bubble size (i.e. enhanced bubble break-up), rather than to formation of smaller bubbles at the distributor with increasing gas density. The effect of gas density was significant both with and without the particles present, with gas holdup increasing, bed voidage increasing and liquid holdup decreasing with increasing gas density. The holdup correlations of Han et al. (1990) have been modified to incorporate the effect of gas density.

AIChE JournalVolume 48, Issue 7 p. 1581-1587 R&D Note Gas holdup in a three-phase fluidized bed M. Safoniuk, M. Safoniuk Dept. of Chemical and Bio-Resource Engineering, University of British Columbia, Vancouver, Canada V6T 1Z4Search for more papers by this authorJ. R. Grace, J. R. Grace Dept. of Chemical and Bio-Resource Engineering, University of British Columbia, Vancouver, Canada V6T 1Z4Search for more papers by this authorL. Hackman, L. Hackman Syncrude Research Centre, Edmonton, Alberta, Canada T6N 1H4Search for more papers by this authorC. A. McKnight, C. A. McKnight Syncrude Research Centre, Edmonton, Alberta, Canada T6N 1H4Search for more papers by this author M. Safoniuk, M. Safoniuk Dept. of Chemical and Bio-Resource Engineering, University of British Columbia, Vancouver, Canada V6T 1Z4Search for more papers by this authorJ. R. Grace, J. R. Grace Dept. of Chemical and Bio-Resource Engineering, University of British Columbia, Vancouver, Canada V6T 1Z4Search for more papers by this authorL. Hackman, L. Hackman Syncrude Research Centre, Edmonton, Alberta, Canada T6N 1H4Search for more papers by this authorC. A. McKnight, C. A. McKnight Syncrude Research Centre, Edmonton, Alberta, Canada T6N 1H4Search for more papers by this author First published: 16 April 2004 https://doi.org/10.1002/aic.690480720Citations: 17AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume48, Issue7July 2002Pages 1581-1587 RelatedInformation

This study tests the scaling approach for three-phase fluidized bed hydrodynamics proposed by Safoniuk, Grace, Hackman, & McKnight (Chem. Eng. Sci. 54 (1999) 4961) based on geometric and dynamic similitude with a limited number (5) of dimensionless groups. Experiments were carried out in two systems in which all five dimensionless groups were matched: an aqueous glycerol solution with glass beads (system 1) and silicone oil with porous alumina particles (system 2), with air as the gas in both cases. Although bed expansions were similar for the two systems, trends differed. Gas holdups were always slightly higher for system 1. The dimensionless transition velocities from dispersed to coalesced flow were similar. The minimum liquid fluidization velocity Reynolds number was slightly higher for system 1 without gas, but somewhat lower with gas present. Differences between the systems are statistically significant, but generally less than 12%, so the dimensional similitude approach gives a reasonable basis for estimating global hydrodynamic parameters under the present operating conditions. The differences between the two systems are attributed to the complex coalescence behavior of liquid mixtures, suggesting that additional dimensionless groups are needed to fully characterize the local dynamic bed behavior.

Vertical gravity settling vessels, usually referred to as primary separation vessels (PSV), are used in separating bitumen aggregates from slurry containing sand and fine clays. The hydrodynamics in the PSV influences the separation efficiency of recovered bitumen through the overall mean flow and turbulent interaction. In order to deepen our understanding of the hydrodynamic conditions in such vessels, this paper presents a combined study of the flow field using Laser Doppler Anemometry (LDA) to measure the velocity field, and computational fluid dynamics (CFD) simulations to validate the CFD model. The investigation shows that the flow geometry has a significant influence on the overall flow pattern in such vessels. It also demonstrates that the CFD simulation is a reliable tool in capturing the complex mean flow pattern observed in experiments. Use of different turbulent models such as the standard k-epsilon model and Reynolds stress model has very little effect on the mean flow field.

A new method of scaling three-phase fluidized beds is presented based upon achieving geometric and dynamic similitude with the aid of the Buckingham Pi theorem. This results in five dimensionless groups that must be matched to ensure hydrodynamic similarity between separate units. Experiments have been carried out to validate this technique by comparing gas hold-up and bed expansion in two different columns operating with significantly different fluid and solids properties, but where efforts have been made to match the five dimensionless groups. These comparisons show mostly favourable agreement between the two units.