Experimental investigation of particle contact time at the wall of gas fluidized beds

2005 ◽  
Vol 60 (15) ◽  
pp. 4349-4357 ◽  
Author(s):  
Mohsen Hamidipour ◽  
Navid Mostoufi ◽  
Rahmat Sotudeh-Gharebagh ◽  
Jamal Chaouki
Keyword(s):  
Experimental Investigation ◽  
Contact Time ◽  
Fluidized Beds ◽  
Particle Contact ◽  
Gas Fluidized Beds

Analysis and modeling of particle–wall contact time in gas fluidized beds

2007 ◽  
Vol 62 (17) ◽  
pp. 4573-4578 ◽  
Author(s):  
Reza Zarghami ◽  
Navid Mostoufi ◽  
Rahmat Sotudeh-Gharebagh ◽  
Jamal Chaouki
Keyword(s):  
Contact Time ◽  
Fluidized Beds ◽  
Gas Fluidized Beds

Measurement of contact time distributions in gas fluidized beds

1968 ◽  
Vol 23 (11) ◽  
pp. 1317-1326 ◽  
Author(s):  
E.B. Nauman ◽  
C.N. Collinge
Keyword(s):  
Contact Time ◽  
Fluidized Beds ◽  
Gas Fluidized Beds

The theory of contact time distributions in gas fluidized beds

1968 ◽  
Vol 23 (11) ◽  
pp. 1309-1316 ◽  
Author(s):  
E.B. Nauman ◽  
C.N. Collinge
Keyword(s):  
Contact Time ◽  
Fluidized Beds ◽  
Gas Fluidized Beds

Expulsion of particles from a buoyant blob in a fluidized bed

1994 ◽  
Vol 278 ◽  
pp. 63-81 ◽  
Author(s):  
G. K. Batchelor ◽  
J. M. Nitsche
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Particle Concentration ◽  
Small Concentration ◽  
Numerical Calculations ◽  
Significant Feature ◽  
Average Particle ◽  
Remarkable Property ◽  
Gas Fluidized Beds ◽  
Secondary Instabilities

It is a significant feature of most gas-fluidized beds that they contain rising ‘bubbles’ of almost clear gas. The purpose of this paper is to account plausibly for this remarkable property first by supposing that primary and secondary instabilities of the fluidized bed generate compact regions of above-average or below-average particle concentration, and second by invoking a mechanism for the expulsion of particles from a buoyant compact blob of smaller particle concentration. We postulate that the rising of such an incipient bubble generates a toroidal circulation of the gas in the bubble, roughly like that in a drop of liquid rising through a second liquid of larger density, and that particles in the blob carried round by the fluid move on trajectories which ultimately cross the bubble boundary. Numerical calculations of particle trajectories for practical values of the relevant parameters show that a large percentage of particles, of such small concentration that they move independently, are expelled from a bubble in the time taken by it to rise through a distance of several bubble diameters.Similar calculations for a liquid-fluidized bed show that the expulsion mechanism is much weaker, as a consequence of the larger density and viscosity of a liquid, which is consistent with the absence of observations of relatively empty bubbles in liquid-fluidized beds.It is found to be possible, with the help of the Richardson-Zaki correlation, to adjust the results of these calculations so as to allow approximately for the effect of interaction of particles in a bubble in either a gas- or a liquid-fluidized bed. The interaction of particles at volume fractions of 20 or 30 % lengthens the expulsion times, although without changing the qualitative conclusions.

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