Main entry under title: Gas fluidization technology. ‘A Wiley-Interscience publication.’ Includes index. 1. Fluidization. I. Geldart, D, TPF65G37 ISBN 0. permission of the publisher. Gas fluidization technology. ‘A Wiley-Interscience publication.’ Includes index. 1. Fluidization. I. Geldart, D, TPF65G37 Powder Technology The behaviour of solids fluidized by gases falls into four clearly recognizable groups, characterized by density difference (ϱs–ϱf) and mean D. Geldart. Powder Technol., 6 (), p. 2. R.H. Wilhelm, M. Kwauk .
|Published (Last):||21 April 2008|
|PDF File Size:||8.11 Mb|
|ePub File Size:||2.57 Mb|
|Price:||Free* [*Free Regsitration Required]|
Two possible beds are considered Fig.
However, coarses have been found in the cyclones of a commercial zinc roaster having a 9 m high freeboard Avedesian, and of a fluid bed combustor with a 3. Geldart and Kelsey showed the importance of support geometry with respect to whether or not bubble splitting is induced.
The most extensive series of measurements on heat transfer to a single immersed tube was carried out by Vreedenberg, although he worked predominantly over the rising range of the heat transfer versus the gas flowrate-curve. The upper surface of the bubble is approximately spherical, and its radius of curvature will be denoted by r.
Fundamentals of Fluidized-bed Chemical Technoloy, Butterworths. The reaction is assumed to be isothermal and to involve negligible volume change. Always use the largest Uso to calculate Usa1t, however.
There was a problem providing the content you requested
Over a period of several months the conversion efficiency decreases and a sample of powder from the bed is found to have a particle porosity of 0. Using CFD to model fluidized beds 4. The rise velocity of such a slug is given see Clift, Grace, and Weber, by: If the gas velocity is gradually increased, a pressure drop curve OAB Fig. Yang and Keairns reviewed the correlations available for predicting the length of the ‘jet’ established when gas enters a fluidized bed vertically, concluded that none was sufficiently general, and proposed their own: For conservative design, A: Various accounts of the development of this and other fluidized bed processes have been given Jahnig, Campbell, and Martin, ;Kunii and Levenspiel, and a comprehensive account of the industrial scene up to was given by Geldart, ; but the most complete and carefully researched account is that given by Squireswho has been associated with process invention and development involving fluid beds since If operation with a range of gas rates is anticipated, the distributor should be designed to give sufficient pressure drop at the lowest gas rate foreseen.
The presence of horizontal tubes appeared to make relatively little difference in the experiments cited, in which fines were reinjected near the distributor.
Particles enter when the inner pipe is slid outwards exposing a small hole near the closed end. The results for first-order irreversible reaction in Table In materials having a wide size range, particularly heldart having a large mean size, segregation by size tends to occur at velocities close to Umf for the mixture. These relative pressure fluctuations are akin to Lanneau’s heterogeneities, but apart from noting the approach to an almost uniform fluidization in the For horizontal jets, another correlation due to Merry may be used: Bubbles can envelop and adhere to vertical tubes, and this causes elongation and increased velocities of rise Grace and Harrison, ; Rowe and Everett, ; Hager and Thomson, ; Rowe and Masson, ; Yates etal.
Solidsmixint Very low Moderate 5. Cherneca 70, Chemical Eng. The history of fluidization contains examples of processes which were developed but were either never built on a commercial scale or were built and operated for only a short time.
: Gas Fluidization Technology (): D. Geldart: Books
Bubbles in commercial fluidized beds usually have sizes in the range 0. Therefore, it is recommended that J.
Under such circumstances the tube surface temperature may approximate to to oe, leading to an apparent emissivity of about 0. As the velocity of the gas is slowly raised, the heterogeneous, two-phase character of the bed first peaks, then gradually gives way to a condition of increasing uniformity culminating in the turbulent state Fig.
Horizontal cylinders in fluidized beds lead to some bubble generation at or near the equator, to a film of gas on the underside, and to a stagnant cap of particles on the top surface Fluidjzation and Harrison, Since upward mechanisms 1 and 2 and the return downward motion of mechanism geldat increase with gas velocity, they tend to be self-cancelling.
Gas Fluidization Technology
Uo and ED are extremely difficult to measure directly in bubbling beds though they can be predicted for quiescent fluidization of fine powders. High Velocity Fluidized Beds 7. Alternatively, the riser may be capped and the cap. Baeyens made a study of particle movement caused by bubbles and suggested that for particle gaas over the entire plate: