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 .
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Illustrative examples and design equations are given so that readers can make their geleart practical calculations. Unfortunately there is nb simple generally accepted method for measuring the sphericity of small irregular particles, so although values have been published Table 2.
Though experiments in small equipment may be revealing and useful, all. Ljungstrom and Lindqvist, While fluidized beds are generally well mixed, it is best to avoid the regions immediately above the distributor and below the bed surface geldadt representative samples are to be withdrawn from a single level.
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Two comparisons of many of the published saltation velocity correlations have been made Jones and Leung, ;and Arastoopour et al. In spite of the fact that much more is now known about fluidized systems it is rare for a new fluid bed process to be designed and installed without the need for cold modelling or pilot plant work, geldaart the experimental techniques available are found in Chapter The way it techno,ogy now depends on several factors.
Here the riser is capped by a horizontal length of pipe cut on a plane through its axis to form a half-cylinder whose open side gedart level with the top of the refractory. The height in the standpipe above the L-valve will reach equilibrium at height Hz greater than HI. A requirement for sampling is that the sampling rate be sufficiently small, that there is negligible interference with the surrounding bed, and that a layer of solids, held by suction, does not build up on the sample tube.
Most particles, however, are irregular and their size is generally measured by Table 2. ge,dart
There are probably more fluid beds used as dryers than any other single application and their design is outlined fouidization Chapter Indeed, the use of vertical tubular inserts has been advocated as a means of controlling bubble growth and hence as a means of reducing the effect of scale on bed behaviour.
Solids captured in the cyclones can conveniently be flkidization by means of lock hoppers or Y-junctions installed between the cyclone and return line. U 0 A bed may be ‘well fluidized’ in the sense that all the particles are fully supported by the gas may still be segregated in the sense that the local composition does not correspond with the overall average.
These mechanisms explain in a qualitative way why segregation by size is relatively insensitive to velocity. However, even allowing for variation in emissivity with temperature, which they also measured, in practical heat transfer situations there also remains the influence of an immersed surface at a temperature hechnology from that of the bulk of the bed on the temperature of the bed material directly adjacent to it.
Lanneau conducted experiments at two pressure levels, 1.
Gas Fluidization Technology – Google Books
Key requirements in planning a reactor are: This may be brought about geldarf the presence of geldaet or binding agents or K A2. For particles smaller than p. Through the work of Darcy and Poiseuille it has been known for more than years that the average velocity of fluid through a packed bed, or through a pipe, is proportional to the pressure gradient: Thesis, University of Michigan.
A qualitative summary of these properties is given in Table 3. For a two-dimensional column or in the wall region of a three-dimensional bed, this can be achieved by manually actuating a solenoid valve Chavarie and Grace, or by synchronization of concentration traces with cine films Lignola, Donsi, and Gaw, The downward movement is achieved by the bulk movement of fines trapped within the dense phase in the bubble-free regions.
Very narrow Narrow Fairly narrow Fairly wide 0. Conditions in the dense phase gas velocity Tecbnology and the corresponding voidage ED are the subject of much discussion and speculation, largely because it is believed that a most of the chemical conversion occurs there and b in fine powders the equilibrium size of the bubbles may be controlled by the voidage, ED.
The final choice between horizontal or vertical tube arrangements would seem to depend largely upon constructional convenience – how best to introduce the tubes into the bed, support them, and allow for thermal expansion. The detail of the results obtained by Piepers, Wiewiorski, and Rietema for heat transfer to vertical tubes would suggest that it is not so easy to estimate an average bed-to-vertical tube coefficient.
The limits proposed for b are conservative in that all cloud and wake solids are assigned gekdart the dense phase, rather than to the bubble phase. As a further check, it is also advisable to ensure that ti. Such powders generally will not behave in an homogenous way and cannot be characterized by a single number.
As the technique was applied to processes far removed from oil cracking, different solids had to be used, but there gaa a tendency to assume that published conclusions drawn from using cracking catalyst were also applicable to these other powders which often had quite different particle sizes and densities.
Clift 5 No part of this book may be produced by any means, or transmitted, or translated into a machine language without the written permission of the publisher.