Hostname: page-component-84b7d79bbc-2l2gl Total loading time: 0 Render date: 2024-07-30T22:17:05.033Z Has data issue: false hasContentIssue false
  • English
  • Français

The motion of particles near a bubble in a gas-fluidized bed

Published online by Cambridge University Press:  26 April 2006

M. A. Gilbertson  and
J. G. Yates
M. A. Gilbertson
Affiliation:
Department of Chemical and Biochemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
J. G. Yates
Affiliation:
Department of Chemical and Biochemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
Get access Rights & Permissions [Opens in a new window]

Abstract

Most models of gas bubbles in fluidized beds are based on the assumption of an empty central region, the void, surrounded by a ‘cloud’ or ‘shell’ of particles whose voidage is larger than that of the remote emulsion phase. Batchelor & Nitsche (1994) investigated the formation of a void by tracking the paths of particles initially within a buoyant ‘blob’ of gas that has the form of a toroidal vortex. They showed that the particles dropped through the floor of the blob under the influence of gravity, leaving it empty. This paper extends their method to particles initially outside the blob. It is shown that inertia allows these particles to penetrate the blob and it is the extent of this penetration that determines the size of the void. The void is nearly as large as the blob for small, light particles, but becomes smaller relative to the blob with increasing particle size and weight until it disappears altogether. This provides an explanation for experimental observations of voids smaller than the blob (or ‘cloud’ as it is sometimes known), and suggests that when examining bubbles in a gas-fluidized bed the most significant dimension is the diameter of the blob and not that of the void.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 323 , 25 September 1996 , pp. 377 - 385
Copyright
© 1996 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Batchelor, G. K. 1974 Low-Reynolds-number bubbles in fluidised particles. Arch. Mech. 26, 339–353.Google Scholar
Batchelor, G. K. 1988 A new theory of the instability of a uniform fluidized bed. J. Fluid Mech. 193, 75–110.Google Scholar
Batchelor, G. K. 1993 Secondary instability of a gas-fluidized bed. J. Fluid Mech. 257, 359–371.Google Scholar
Batchelor, G. K. & Nitsche, J. M. 1994 Expulsion of particles from a buoyant blob in a fluidized bed. J. Fluid Mech. 278, 63–81.Google Scholar
Benveniste, D. E., Kinrys, S. & Qassim, R. Y. 1983 Flow past the fluidization bubble: Effect of voidage variation. In Fluidization (ed. D. Kunii & R. Toei), pp. 9–14, Engineering Foundation, New York.
Buyevich, Y. A., Yates, J. G., Cheesman, D. & Wu, K. T. 1995 A model for the distribution of voidage around bubbles in a fluidized bed. Chem. Engng Sci. 50, 3155–3162.Google Scholar
Collins, R. 1989 A model for the effects of the voidage distribution around a fluidization bubble. Chem. Engng Sci. 44, 1481–1487.Google Scholar
Davidson, J. F. 1961 Symposium on fluidisation – Discussion. Trans Inst. Chem. Engrs 39, 232.Google Scholar
Davidson, J. F., Harrison, D. & Guedes de Carvalho, J. R. F. 1977 On the liquidlike behaviour of fluidized beds. Ann. Rev. Fluid Mech. 9, 55–86.Google Scholar
Davies, R. M. & Taylor, G. I. 1950 The mechanics of large bubbles rising through extended liquids and through liquids in tubes. Proc. R. Soc. Lond. A 200, 375–390.Google Scholar
Jackson, R. 1963 The mechanics of fluidized beds part II: The motion of fully developed bubbles. Trans. Inst. Chem. Engrs 41, 22–28.Google Scholar
Jackson, R. 1971 Fluid mechanical theory. In Fluidization (ed. J. F. Davidson, & D. Harrison), chap. 3. Academic Press.
Murray, J. D. 1963 On the mathematics of fluidization. Part 2. Steady motion of fully developed bubbles. J. Fluid Mech. 22, 57–80.Google Scholar
Pyle, D. L. & Rose, P. L. 1965 Chemical reaction in bubbling fluidized beds. Chem. Engng Sci. 20, 25–31.Google Scholar
Rowe, P. N. & Partridge, B. A. 1965 An X-ray study of bubbles in fluidised beds. Trans Inst. Chem. Engrs 43, 157–175.Google Scholar
Rowe, P. N., Partridge, B. A. & Lyall, E. 1964 Cloud formation around bubbles in gas-fluidized beds. Chem. Engng Sci. 19, 973–985.Google Scholar
Yates, J. G., Cheesman, D. J. & Sergeev, Y. A. 1994 Experimental observations of voidage distribution around bubbles in a fluidized bed. Chem. Engng Sci. 49, 1885–1895.Google Scholar