Quality of fluidization

Fluidization quality of fluidized catalyst beds involving a decrease in gas volume... 

Add multiple bed density taps to the regenerator to determine quality of fluidization and identify a damaged or partially plugged air distributor... 

The efficiency of particle-fluid contacting in fluidization, popularly described in terms of the quality of fluidization, has its origin not only in the physical properties of the fluidizing medium and of the solid material of which the particles are composed, but also in the particle characteristics and in the group behavior of the particles while in motion. Particle characteristics include size, size distribution, shape, and surface roughness or texture, while... 

The efficiency of particle-fluid contacting in fluidization, popularly described in terms of the quality of fluidization, has its origin not only in the physical properties of the fluidizing medium and of the solid material of... 

The present model appears to be useful in the design of fluidized bed filters. It does not address questions concerning the quality of fluidization, stickiness of the particles, solids regeneration rates and agglomeration effects. In order to optimize the fluidized bed filter these effects must be considered in conjunction with those aspects to the problem elucidated here. 

Design of fluidized bed crystallizers requires estimates of the required seed bed volume and the quality of fluidization. Fluidization behavior of seed was measured in the laboratory for monosized cuts. For a given volumetric flow rate through any given fluidized bed crystallizer, there is a minimum and maximum particle size which will result. The minimum is that below which the particles will elutriate out the top of the column. The maximum is determined by the size at which removal or controlled attrition (see below) takes place at the bottom. 

Apart from density and particle size, several other solid properties, including angularity, surface roughness and composition may also signiflcantly affect the quality of fluidization. However, in many cases Geldart s classiflcation chart is still a useful starting point to examine fluidization quality of a speciflc gas-solid system. 

Mireur and Bischoff [6] correlated data on k[ and versus easily accessible parameters like uju f and d,/Lf the results are shovra in Figs. 13.4-3 and 4. The curve RTD data was obtained from residence time distribution experiments. These are performed with a nonadsorbable tracer like helium. The reaction experiments leading to the curve conversion data obviously involves adsorbable species. This may explain the difference between the two curves. The correlation is not meant to be d nitive since it does not account for the effect of the particle-size distribution pointed out by de Groot [2], by van Swaay and Zuiderweg [23], and by de Vries et al. [24]. The particle-size distribution is known to affect the quality of fluidization. De Vries et al. found that = Lfki/u, varies linearly as a flinction of the percentage of fines firom 4 at 7 percent fines to about 1.S at 30 percent fines. Also, Ro = is markedly affected by this variable. Nevertheless... 

Loss of fine solids from the bed reduces the quality of fluidization and reduces the area of contact between the solids and the gas in the process. In a catalytic process this means lower conversion. 

Quality of fluidization increases for large particles heat transfer coefficients double from 1 to 10 bar for larger particles but not smaller ones. 

The main effect of increasing pressure will be to raise the gas density pg, but this will have only a slight effect on the particle convective term through its influence on [Eq. (48)]. In the case of small particles, however, the suppression of bubbling caused by increasing pressure (see above) would be expected to increase the heat transfer coefficient by improving the quality of fluidization near the transfer surface. This was observed experimentally by Borodulya et al. (1980), who found an increase of 30% in the maximum heat transfer coefficient for 0.126 mm sand between 6 and 81 bar pressure. 

Volk W, Johnson CA, Stotler HH. Effect of reactor internals on quality of fluidization. Chem Eng Progr 58(3) 44—47, 1962. 

The differences in behavior between small laboratory beds and larger demonstration units can in part be attributed to a switch from porous plate distributors in the small bed to discrete hole or bubble caps in the larger beds. The porous plates give a better quality of fluidization, e.g., smaller bubbles, for shallow beds and beds of moderate depth see Rowe and Stapleton (1961). 

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