Mass Transfer in Packed and Fluidized Beds

Packed and fluidized beds are commonly used in industrial mass-transfer operations, including adsorption, ion exchange, chromatography, and gaseous reactions that are catalyzed by solid surfaces because they offer a dramatical increase in the sur- 

Mass transfer in both gas and liquid fixed and fluidized beds of spheres has been correlated by Gupta and Thodos (1962) with the equation 

For packed and fluidized beds, the area for mass transfer is usually expressed in terms of a, defined in this case as the area for mass transfer per unit volume of packed bed. It is easy to demonstrate that 

Equation (2-92) suggests that the smaller the packing size, the higher the area available for mass transfer per unit of packed volume. However, pressure drop through the packed bed becomes a limiting factor as the size of the packing material diminishes. 

The column of Example 2.12 is packed randomly with spherical glass beads 3.5 mm in diameter. The water is now supplied as a fine mist that flows down through the packed bed at a flow rate just enough to replace the water lost by vaporization and to keep the surface of the packing wet. Under these conditions, it may be assumed that equation (2-90) applies. 

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