Static bed height

Polyethylene beads of relatively narrow size distribution with a harmonic mean diameter of 2800 mm and a particle density of 910 kg/m3 were used as the bed material. A static bed height of 1.4 m was employed. 

Figure 6. Influence of the static bed height on jet attrition of spent FCC catalyst in a submerged jet test facility (Dt = 0.05 m, uor= 100 ms 1, dor = 2 mm. (Werther andXi. 1993.)...

Again, as in the case of jet attrition, attention must be paid in the experimental determination of Ra bub to the isolation of the attrition that is due to bubbles. There are basically two ways to do this. The one is to use a porous plate distributor in order to avoid any grid jets. The other is the procedure suggested by Ghadiri et al. (1992a) which is depicted in Fig. 7 the measurement of the production rate of fines at different values of the static bed height permits to eliminate the grid jet effects. 

Figure 29 (Qin and Liu, 1982) shows the behavior of individual particles above the distributor recorded by video camera of small clusters of particles, coated with a fluorescent material and spot-illuminated by a pulse of ultra violet light from an optical fiber. The sequential images, of which Fig. 29 just represents exposures after stated time intervals, were reconstructed to form the track of motion of the particle cluster shown in Fig. 30. Neither this track nor visual observation of the shallow bed while fluidized, reveal any vestige of bubbles. Instead, the particles are thrown up by the high velocity jets issuing from the distributor orifices to several times their static bed height.

Recently, Hays et al. [26] reported on of several cases where particle clustering was inferred in flnidized bed systems. In the first case, they attempted to reproduce why highly variable entrainment rates were observed in a commercial-scale fluidized bed even though steady-state was presumed. Tests were conducted in a 6 inch (15-cm) diameter fluidized column with a static bed height of 52 inches (132 cm) of the same Geldart Gronp A powder (dp5o of 55-60 microns) used in the commercial process. The test unit was operated in batch mode at a superficial gas velocity of 0.66 ft/sec (0.2 m/sec). 

Figure 9-24 Interfacia] areas as functions of gas velocity and static bed height [from data of Strumillo and Kudrn 2).

ISlHnm Static Bed Height, 1.25-l(gim s Flux S9 C inlet Temperature... 

Limestone stoichiometric ratio (controlled) Total static bed height, inches of 11.5 gram 1.2 1.2... 

Table 10.2 Dominant fluctuation frequencies (Hz) of 500- and 705-pm glass particles in a 19-cm-i.d. cylindrical fluidized bed with static bed height of 19 cm...

Gukhman number (see Table 4.10) heat transfer coefficient, kW/(m K) mass transfer coefficient, kg/(m s) static bed height for spouted beds, m specific enthalpy, kJ/kg... 

The cylindrical drying chamber is 0.55 m in diameter and 0.72 m high. The nominal static bed height is 0.36 m (62 kg of polycarbonate beads) and the dynamic bed height is 0.42 m. A vacuum pump with controllable power evacuates evaporated moisture from the drying chamber to the condenser. 

The volumetric evaporation rate, heat utilization factor, and dynamic bed height need to be taken from experimentally obtained correlations. The static bed height (//,) can be chosen assuming that for a particular drying material, its residence time in the small and large dryers is the same ... 

Since the material hold-up below the clogging point is related to the mass of inert particles, the static bed height can thus be determined. 

It should be noted that the term fluidization does not adequately reflect the bed behavior as particles in the PFB are vibrated rather than fluidized. Thus, at incipient pulsed fluidization (also called the lower pulsed fluidization velocity) and above, the bed performs as the vibrated or vibro-fluidized bed with frequency and amplitude depending on air velocity, static bed height, and frequency of the air stream relocation (GawrzynsM and Glaser, 1996 Blacha-Jurkiewicz, 1987). With increasing air velocity, more air bubbles and isolated spouts appear in the bed this velocity is called the upper (developed) pulsed fluidization velocity. Above this velocity, the bed turns into a classical... 

The static bed height in the fluidized bed is usually expressed in terms of the ratio of the static height of bed materials (//) to the column diameter (D). A bed height... 

All experimental conditions used have been summarized in Table 4.11 in which both the membrane length at both sides and the static bed height were kept at 80 mm. 

Table 4.11 Operating Conditions Used in the Experiments Both Membrane Height and Static Bed Height Were Kept as 80 mm at Both Sides...

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