Pulsed fluid beds

Fluidization is one of the most commonly used techniques for drying particulate solids. The technique reiies on a high-velocity hot gas stream that creates a fluid bed with speciai hydrodynamic and heat/mass transfer characteristics. Aithough weil entrenched in industry, fluid bed dryers have the following disadvantages that limit their appiication  

A relatively high pressure drop that calls for high-pressure blowers 

Particle shape restricted to those approaching sphere or cuboid 

Bed height limited to between the minimum height that will ensure uniform fluidization and the maximum height allowed by the pressure drop 

Restricted particie size and size distribution polydisperse materials cause excessive entrainment, while both fine and coarse materials do not fluidize well 

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The spouting bed temperature is generally in the range of 150-170 °C, which is close to the maximum spherulite growth rate, and therefore ensures quick completion of the primary crystallization. The material temperature at the outlet of the pulsed fluid bed is usually <180°C. 

Gawrzynski, Z., Glaser, R., and Kudra, T., Drying of powdery materials in a pulsed fluid bed dryer. Drying Technol, 17(7-8), 1523-1532,1999. 

Nitz, M. and Taranto, O.P., Drying of beans in a pulsed fluid bed dryer Drying kinetics, fluid-dynamic study and comparisons with conventional fluidization, J. Food Eng., 80, 249-256, 2007. 

FIGURE 21.38 Principle of a pulsed fluid bed with periodically relocated gas stream. 

Comparison of Some Industrial Band Dryers for Vegetables with the Pulsed Fluid Bed Dryer... 

Glaser, R. 1991. Possibilities for drying of sliced vegetables in pulsed fluid bed. Proceedings of the VII Drying Symposium, Lodz, Poland, pp. 147-154 (in Polish). 

A. Crystallizer fluid bed or pulse fluid bed or paddle crystallizer... 

M. Poirier, T. Kudra, and R. Platon, Pulsed fluid-bed technology—Opportunities for low temperature drying of biomaterials, Proceedings of the Eirst Nordic Drying Conference, Trondheim, Norway, June 27-29, Paper 28 (2001). 

Figure 6.2 Rotation-pulsed fluid bed dryer. (From Gawrz5mski, 1987).

Drying in Pulsed Fluid Beds ACTIVE CHAMBER... 

Figure 6.3 Principle of the pulsed fluid bed with relocated air stream.

Figure 6.4 Pressure drop in a fluidized bed and a pulsed fluid bed dryer with relocated air stream. (Adapted from Zgorzalewicz and Glaser, 1989.)...

Gawrzynski Z. Apparatus for generation of a pulsed fluid bed swirling inside a chamber. Polish Patent No. 150,412, 1987. 

Gawrzynski Z, Glaser R, Stanislawski J, Poirier M, Kudra T. Drying of P P sludge in a pulsed fluid bed dryer. Drying Technology (in press). 

Glaser R, Gawizynski Z. Drying of sliced vegetables in the pulsed fluid bed. Scientific papers of Wroclaw Academy of Economics. Volume Technology 528 71-87, 1990 (in Polish). 

Zgorzalewicz J, Glaser R. Hydrodynamics of a pulsed fluid bed of coarse materials. Chemical and Process Engineering 1 3-21, 1989 (in Polish). 

Gawrzynski Z, Glaser R. Dr5ing in a pulsed-fluid bed with relocated gas stream. Drying Technology-An International Journal 14 1121-1172, 1996. 

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