Comparison of Packed and Fluidized Beds

Belter and co-workers developed a periodic countercurrent process for treating a fermentation broth to recover novobiocin. They found that they were able to scaleup the laboratory results to production operations if the two systems have similar mixing patterns and the same distribution of residence times in the respective columns. The mixing patterns are the same when the space velocity (F/%) and the volume ration (f /c) are the same. This is shown in Fig. 22 for the effluent concentration of novobiocin from laboratory and production columns. 

The scaling-up of packed beds is subject to the difficulties of maintaining even flow distributions. Removal of solution through screens on side walls is not recommended and the flow of resin from one section into another of much greater area could distort the resin flow profile. 

Mass transfer coefficients have been correlated for packed and fluidized beds.t The mass transfer coefficients for packed beds are 50 to 100% greater than for fluidized beds. 

The volume of resin in a packed bed is about half that in a fluidized bed, but the packed bed column may be up to eight times smaller. Despite this, a complete fluidized bed operation may still be smaller than a fixed bed operation. Also, fluidized bed columns do not operate at high pressures so they can be constructed more economically. 

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