Bed expansion data

Fig. 6. Qdyn/Qmax for BSA adsorption to fluidized Streamline DEAE at different linear flow rates. Original capacity data from Hjorth et al. [51], liquid residence time calculated from bed expansion data provided in Ref. [51]...

Figure 5.14 Typical bed expansion data for 3.57 mm glass spheres fluidised by shear-thinning polymer solutions [Srinivas and Chhabra, 1991]...

Godard, K. E. and RICHARDSON, J. F. Chem. Eng. Sci. 24 (1969) 363. Correlation of data for minimum fluidising velocity and bed expansion in particulately fluidised beds. 

A wide range of operating conditions is used commercially. Performance data are in Table 12.19. Gas velocities cover a range of 3-20 times the minimum fluidizing velocity or 0.1-2.5 m/sec. Bed expansion ratios are up to 3 or so. As in fluidized bed drying, bed depths are low, usually between 12 and 24 in. Evaporation rates are in the range 0.005-1.0 kg/(sec)(mz). 

Table 4. Adsorption of humanized IgGl to fluidized Prosep-A. Capacity data taken from Beyzhavi [34]. Bed expansion was calculated according to Richardson and Zaki, with U, = 8.9cm/min and n = 5.9, the parameters were obtained as described in Table 2...

Fig. 7. kf versus linear flow rate calculated for BSA adsorption to fluidized controlled pore glass after Rowe (A, Eq. 19, Ref. 74) and after Fan et al. ( , Eq. 20, Ref. 75). Physical data of adsorbent average particle diameter 200 pm, average particle density 1240 kg/m3, BSA diffusion coefficient in solution 7.3-10 11 m2/s, bed expansion calculated according to Richardson and Zaki, U, and n estimated according to Eqs. (3-5)... 

Backwashing is necessary to keep the bed in a hydraulically classified condition, to minimize pressure drop, and to remove resin fines and suspended solids that have been filtered out of the influent water. Normal practice is to backwash at the end of each run for about 15 min, so as to obtain about 50 to 75 percent bed expansion. The flow rate required to achieve this expansion is obtained from the manufacturers data. As noted in the statement of the example, an appropriate flow rate in this case is 6.4gal/(min)(ft2). The total backwash rate is thus [6.4gal/(min)(ft2)](14ft2) = 90 gal/min. The total water requirement, then, is (90 gal/min)(15 min) = 1350 gal (5.11 m3). 

Figure 5 shows typical expansion data measured by Morooka et al. (M41) using unclassified FCC catalyst particles. As soon as the bed reaches minimum fluidization, it starts to expand. After bubbles start to form (i.e., under aggregative fluidization) the bed expands slowly and then... 

From 1963 to 1967 a 1/32 inch extrudate catalyst was used. In 1967 relatively minor modifications were made to accommodate a micro-spheroidal fine catalyst. This eliminated the need for the internal recycle pump previously required to supply the liquid velocity necessary for bed expansion. Operating and performance data have been described previously (3, 4). 

Figure 3 shows the eomparison of the normalized bed height from the H-Oil reactor data and ANN model predicted values after two millions training events. The maximum ARD% is 13.8% with an AAD% of 1.92% for the 85 sets of input data employed. However, if only data with bed height values below the allowable upper level are considered, the max. ARD% and AAD% reduce to 10.7% and 1.43% respectively. It is clearly demonstrated the predicted results from the ANN ebullated-bed expansion model are very close to the literature values. This model by no mean limits its applications just to predict the interface level. It can be extended to eover heat generation in terms of exotherms, spread temperature and/or catalyst average temperature (CAT) from data recorded in the technieal report [15]. 

Bed expansion in particulate fluidization. [Sj permission, data taken from R. H. fPillie/m and M. Kwatik, C/iem. Etiff. Prog., 44 201 (I948). ... 

Little is known about the influence of particle shape on the minimum fluidising velocity and bed expansion of liquid fluidised beds even for Newtonian liquids [Couderc, 1985 Flemmer et al., 1993]. The available scant data suggests that, if the diameter of a sphere of equal volume is used together with its sphericity factor, satisfactory predictions of the minimum fluidising velocity are obtainable from the expressions for spherical particles. Only one... 

The extensive literature data based on absolute pressure fluctuation and bed expansion measurements up to 1989 were correlated by Cai et al. (1989) to be... 

The constant 0.027 is a dimensional constant with units of (cm/s) ". Equation (113) gives reasonable agreement with data from fluidized beds using industrial types of orifice distributor plates. Porous distributor plates, as expressed in Eq. (112), behave as though they contained approximately 1 hole per 10 cm of bed area. The principal effect of adding fines to a fluidized bed of group B powders is the reduction of the mean particle size. At equal values of excess (U — U f), this results in increased bed expansion and solid circulation rates but produces no decrease in mean bubble size. 

Di Felice et al. (1992a) investigated the validity of the full set of scaling laws for bubbling and slugging fluidized beds. They used an experimental facility that permitted the pressurization of different diameter test sections to match the scaling parameters. Minimum fluidization measurements, video measurements of bed expansion, and pressure fluctuation data were used to compare the similarity of five different bed eonfigurations. Three of the beds were scaled properly. 

Gas holdup data in the freeboard region of the bed and the extent of the bed expansion from two cold models (one 8.3 cm ID and the other 91.4 cm ID) were used in their analysis, which satisfactorily verify the hydro-dynamic similarity. More studies are needed based on these two approaches (Luo et al., 1999 Safoniuk et al., 1999) to arrive at general similarity rules for scale-up applications. 

Numerous correlations and models have been developed to predict both bed expansion and bed voidage. There are two types of correlations purely empirical correlations and correlations based on the two-phase theory. Empirical correlations have been reviewed by Thonglimp et al. [15], One should be aware that most of the correlations which have been published were developed from data collected in small laboratory columns. They thus did not take into account the coltimn diameter which has a very important effect on bed expansion, as shown by Figure 2 [31], These correlations should thus be used with extreme caution for the design of large industrial columns. 

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