The influence of horizontal internals on the flow pattern in dense fluidized beds. An X-ray investigation.

J.-J. van Dijk and A.C. Hoffmann, Department of Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and
D. Cheesman and J.G. Yates, Department of Chemical and Biochemical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom.

Abstract
The influence of horizontally placed internals on the physical behaviour of a dense fluidized bed has been observed using an X-ray technique. The internals were sieve-like baffles with an aperture size two orders of magnitude larger than the diameter of the bed particles. Both a freely bubbling bed and single injected bubbles were observed. For the latter, the bubbles were caused to emerge from a layer more opaque to X-rays into one more transparent. In this way the flowpattern around the bubble and the wake could be observed. The results show that the baffles do not influence the mean bubble size or velocity significantly, confirming earlier indirect observations. It is also shown that the wake material is removed from the fluidization bubbles by the baffles. Results are given as statistics for bubble size and rise velocity as a function of the fluidization velocity with and without baffles present, and sequences of X-ray images showing the effect of the baffles.