Turbulent fluidized beds

The turbulent fluidized bed has a similar or slightly lower soHds volume fraction than the vigorously bubbling bed. There is considerable transport of soHds out of the turbulent bed and the bed level is not very distinct. Large-scale cyclones are needed to return soHds to the bed. On average, the bed inventory passes through the cyclones several times per hour. 

Bed density can then be predicted from 1 — ). The expression for is appHcable for turbulent fluidized beds and for the turbulent... 

Fig. 17. TDH above vigorously bubbling or turbulent fluidized beds as a function of bed diameter from 0.025 to 7.5 m (27).

At high gas velocities in the bed, the stable bubbles break down into unstable voids that continuously disintegrate and reform. This type of bed is said to be operating in the turbulent fluidized-bed regime, and is characterized by higher heat- and mass-transfer rates than in the bubbling bed. As the gas velocity is increased further, the... 

As a result of the existence of bubbles/voids in turbulent fluidized beds, the hydrodynamic behavior of turbulent fluidization under relatively low gas velocity conditions is similar, to a certain extent, to that of bubbling fluidization. However, distinct differences exist under relatively high gas velocity conditions, thus rendering many correlations previously developed for the bubbling regime invalid for the turbulent regime. 

Results obtained in the fast fluidized bed reactor show that both the conversion of butene and the yield of butadiene are increased by about 15 to 25% as compared to the turbulent fluidized bed reactor. It is reported that this process is being commercialized in Liaoning Province, in northeast China. 

Wang, Z. Investigations on String Operation of Fast and Turbulent Fluidized Bed (Chinese, The Proceeding of 4th National Conference on Fluidization, p. 201 (1987). 

Yamazaki, R., Asai, M., Nakajima, M., and Jimbo, G. Characteristics of Transition Regime to a Turbulent Fluidized Bed, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 720-725. Somerset, Pennsylvania (1993). 

Maleic anhydride/phthalic anhydride Regenerator bubbling bed/turbulent fluidized bed regime Turbulent fluidized bed regime... 

Fig. 1 Typical equipment configurations for (A) dense (bubbling, slugging or turbulent) fluidized bed reactors (B) circulating fluidized bed reactors. Heat transfer surfaces or baffles that might be present in (A) or (B) are not shown.

Chaouki, J. Gonzalez, A. Guy, C. Klvana, D. Two-phase model for a catalytic turbulent fluidized bed reactor application to ethylene synthesis. Chem. Eng. Sci. 1999, 54, 2039-2045. 

Bubbling and turbulent fluidized beds are operated with small granular or powdery non-friable catalysts. Rapid deactivation of the solids can then be... 

Fig. 10.4. A schematic representation of a turbulent fluidized bed. The illustration shows that in a turbulent fluidized bed entrainment is significant and an internal cyclone with solids recycle through a dipleg is required. Reprinted from [82] with permission from Elsevier.

Turbulent Fluidized Bed B Counter-cnrrent contacting is beneficial... 

Models for turbulent fluidized bed reactors are normally based on one dimensional gas flow, despite the significant radial density gradients observed experimentally [56, 57],... 

Foka M, Chaouki J, Guy C, Klvana D (1994) Natural Gas Combustion in a Catalytic Turbulent Fluidized Bed. Chem Eng Sci 49(24A) 4269-4276 Froment GF, Bischoff KB (1990) Chemical Reactor Analysis and Design. John Wiley and Sons, New York, Second Edition... 

---