Fluidized-bed entrained

Characterics Fixed bed Moving bed Fluidized bed Entrained flow... 

Reactor typo Fixed bed Fluidized bed Entrained bed Fixed Entrained Turbulent Entrained Miiidizcd... 

Fast erosion leading to size decrease and, in the case of the fluidized bed, entrainment out of the bed... 

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.

Fast Reactor temperature 500 °C, high heating rates >1000 °C/s, short hot vapor residence 1 s Fluidized bed, entrained flow, ablative (contact pyrolysis) 75% 12% char 13%... 

At the very beginning we define the terms that will be used throughout this chapter. Two terms are often used for the flow of solid out of fluidized beds. These are the terms entrainment and elutration. Entrainment means the flux of solids carried out of the fluidized bed by the gas in kg per unit cross-sectional area and second. Elutriation means the classifying effect of the fluidized bed entrainment—it characterizes the selective removal of particles of individual size from the fluidized bed. 

There are a large number of processes where solid catalysts are employed. The process streams are either gaseous or liquid, or a combination of these. The catalysts usually have a high porosity. Especially in the petroleum and petrochemical industries one encounters catalytic reactors of a great variety. Well known reactor types are fixed bed, moving bed, fluidized bed, entrained bed, slurry reactor and three phase packed column. The choice between these reactor types is mostly based on the relative requirements for mass transfer, degree of conversion and heat transfer. Heterogeneous catalysis is a well developed science, with its own specific literature. In this chapter some technical acpects will be presented, particularly those related to scale-up. 

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