Fluidized Bed Coating and Granulation

Richard Turton, Gabriel L Tardos, and Bryan J. Ennis 

The main goal of this chapter is to provide a technical basis or framework for analyzing fluidized bed coating and granulation operations. 

It is the hope of the authors that this chapter will be of value to the practicing technologist and also will provide a basis for focused research in the many areas of this field which is still required. 

The use of fluidized beds to coat and agglomerate particles dates back over forty (40) years. Currently, fluidized beds are used to coat a variety of particles in the size range of 50 pm - 1 cm, with a variety of functional and 

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The primary applications for large-scale jetting fluidized beds are in the area of coal gasification as described by Yang et al. (1995), Kojima et al., (1995), and Tsuji and Uemaki (1994). Smaller scale applications are for fluidized bed coating and granulation to be discussed in Chapter 6. 

R. Turton, G. I. Tardos, B. J. Ennis, Fluidized bed coating and granulation, Fluidisation, Solid Handling and Processing, Chapter 7, (W.C. Yang, Ed.) Noyes Publications, Westwood,... 

Hemati, M., Cherif, R., Saleh, K., and Pont, V., Fluidized bed coating and granulation Influence of process-related variables and physicochemical properties on the growth kinetics. Powder TechnoL, 2003,130,18-34. 

Turton R, Tardos G, Ennis BJ. Fluidized Bed Coating and Granulation. In Yang WC, Fluidization, Solids Handling Processing, New Jersey Noyes Publications, Westword, 1999. 

Wan, L. S. C., and Lai, W. F., Factors Affecting Dmg Release from Drug-Coated Granules Prepared by Fluidized-Bed Coating, Int. J. Pharmaceutics, 72 163-174(1991)... 

The hydration state of risedronate sodium was monitored continuously in a fluidized bed dryer and correlated to data on the physical stability of tablets made from the monitored material [275]. The final granulation moisture was found to affect the solid-state form, which in turn dictated the drug s physical stability over time. The process of freeze-drying mannitol was monitored continuously with in-line Raman and at-line NIR spectroscopies [276]. The thin polymer solvent coatings, such as poly(vinyl acetate) with toluene, methanol, benzene, and combinations of the solvents, were monitored as they dried to generate concentra-tion/time profiles [277]. 

Important industrial applications for fluidized bed reactors are also discussed, including fluid catalytic cracking (Chapter 14), gasifiers and combustors (Chapter 15), chemical production and processing (Chapter 16), coating and granulation (Chapter 17), and ffuidized bed drying (Chapter 18). 

However, in various coating and granulation experiments a change in the shape of the distribution is observed, for example a dispersion of the distribution. In Fig. 7.45 the results of five different coating experiments are shown, which were conducted in Wurster equipment, a conventional fluidized bed apparatus (FB) in top and bottom spray configuration, and a spouted bed apparatus (SB) in top and bottom spray configuration. Although identical initial conditions were used and the process conditions are comparable (see Tab. 7.6), different final distributions are achieved. This effect cannot be explained by the common model of Eq. 7.34, but it underlines the influence that different types of equipment with different flow patterns may have on the process result. 

The vacuum fluidized bed technique is already being applied for drying, coating and granulating processes at laboratory size as well as for full production scale (Figure 13.2). Relationships and parameters, which have been determined in detailed experimental studies researches stay obtained while up-scaling to production scale [7]. 

Nienow, A. W., Fluidized Bed Granulation and Coating Application to Materials, Agriculture and Biotechnology, Proceedings of the First International Particle Technology, Forum, Denver, CO., USA (1994). 

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