GAS FLUIDIZATION TECHNOLOGY GELDART PDF
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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It is the bubbling phenomenon which causes particle circulation patterns be established. In Fluidization Eds 1.
Gas Fluidization Technology – Google Books
Typical conditions for such an operation are given by Avedesian Lanneau suggested that the change was accompanied by the breakdown of slugs into smaller bubbles containing a higher proportion of solid particles. This qualitative agreement is encouraging and. To represent the degree of non-uniformity of a fluid bed, Lanneau defined the parameter ‘heterogeneity’ as the mean deviation of the instantaneous point density from the time-averaged bed density Fig.
Subscript 1 denotes conditions at the inlet to gledart bed. The provision of the other elements shown depends on the particular application contemplated.
However, for fast reactions, bplays a significant role. In this regime, some particles may move slowly in dense phase flow along the bottom of the pipe, while, simultaneously, others travel in suspension in the gas in the upper part of the pipe. However, the signals are difficult to interpret and subject to significant error in the presence of local homogeneous combustion of gaseous components like CO and methane Lim et aI.
Gas fluidization technology
Indeed, the use of fluidkzation tubular inserts has been advocated as a means of controlling bubble growth and hence as a means of reducing technoogy effect of scale on bed behaviour. Further work should be directed towards the phenomenon of segregation by size and density difference, particularly on a larger scale and at higher Example 5.
Capacitance elements have also been mounted on vertical and horizontal tubes Ozkaynak and Chen, ; Chandran and Chen, ; Fitzgerald, Catipovic, and Jovanovic. Always use the largest Uso to calculate Usa1t, however.
The average of the velocities at which the bubbles appear and disappear is called the minimum bubbling velocity or bubble point and generally coincides with the maximum bed height for deep beds; premature bubbling can be caused by non-uniform distributors or protuberances in the bed, but the maximum values of Umb have been correlated by Abrahamsen and Geldart and found to depend on the gas and particle properties: Qureshi and Creasy concluded, from a review of published information, that the distributor pressure drop required for satisfactory operation was given by: Normally this requirement imposes no further restriction on ti.
Calculate UmJUmf for cold model, initial, and final reactor conditions, using Eq. Since the gas is already accelerated then, from Eg. These conditions are considered to be satisfied if the sampling tube is much smaller than the bed dimensions and if the mean gas velocity in the tube is Umf or less.
Geldart and his team produced a very comprehensive and well edited book. If it is desirable to separate the load-bearing and gas distribution requirements, the gas can be introduced into the bed by a pipe grid, shown schematically in Fig. The test conditions, experimental methods, and the results of these investigations are summarised in Table 7. Shell Powder Blower Gas distributor Heat exchanger for fluidizing gas 6.
Defluidization can be regarded as a special case of segregation in that some or all of the bed, usually that near the distributor, may be immobile.
Gas Fluidization Technology
Thus ‘bubbling’ will occur if the powder is spoutable and is therefore in group D. It should be noted that ti. Because the technique of fluidization is used in many different industries for drying, combustion, catalytic reactions, granulation, calcination, etc. I I Thiel and Potter V 5.
One useful way is to specify the relative spread, uld m’ This is obtained by using the cumulative percentage undersize versus the: Entrainment within the channels or bubbles at velocities which exceed the terminal velocities of the fines. It may readily be demonstrated that this component is negligible.
If the gas velocity is reduced while continuing to feed at the constant mass flux G1, the frictional resistance, and thus the pressure drop in the line, will decrease. If excess gas is injected through the tube, the additional bubble stream will create a pumping action.