Fluid Bed Particle Processing

The present text introduces the use of fluidised bed processing in the context of wet granulation and coating. The text also covers introductory information about the mechanical properties of dry granules. This is a scientific field rarely taught at universities or engineering schools around the world although it has enormous and ever increasing relevance to the chemical and biochemical industries. Often students are left with nothing but qualitative tendencies and hands-on experience as no textbook yet covers all relevant subjects treated in this text.

Being part of the powder technology field it is the aim of this text to narrow the gap between applied engineering and quantitative models and theory. The text is aimed at undergraduate university or engineeringschool students working in the field of chemical or biochemical engineering. Newly graduated as well as experienced engineers may also find relevant new information as emphasis is put on the newest scientific discoveries and proposals presented in recent years of scientific publications. In order to provide a firm theoretical background several of the relevant formulas have been derived in the appendix which is often impossible to find elsewhere even in scientific literature. It is the hope that such theoretical considerations may help the reader to understand how particle technology is closely related to other branches of chemical science and chemical engineering. The literature list may also hopefully be an inspiration for further reading in the small but highly important field of fluid bed processing.

I alone am responsible for any misprints or errors but I will be grateful to receive any critics and suggestions for improvements.

Copenhagen, September 2006

Peter Dybdahl Hede

1. Introduction to fluid bed processing
   1. Types of fluid beds
   2. Important fluid bed parameters
   3. The Geldart classification of particles
   4. Advantages and disadvantages of fluid bed operations
2. The process and principles of Wet agglomeration
   1. Introduction to the stages of the granulation processes
   2. Wetting and nucleation
   3. Granule growth behavior
   4. Breakage and attrition
   5. Simulation of the aggl. – a brief review on population balance theory
   6. Summing up on wet aggl. – Qual. guidelines for param. influencing aggl.
3. Granule coating principles and properties in fluid beds
   1. Parameters describing the coating process and result
   2. Product, system and operating param. Aff. the coating process and effic.
   3. Influence of product and formulation vari. on coated granule morphology
   4. Aggl. or Coating?? – Qual. trends and attempts of find. a boundary param.
   5. Qualitative description of key parameters governing the coating process
4. Mech. prop. of gran. and coating layer – strength and breakage mech.
   1. Properties characterising the granule strength
   2. Types of breakage mechanisms
   3. Towards a quantitative prediction of breakage mechanisms
   4. Qualitative trends of parameters affecting breakage
   5. Modern approach – a brief rev. on computer sim. of granule breakage
   6. Strength test methods – a brief review
   7. Summing up on granule strength
5. Summary
6. Table of symbols
7. Literature
8. Appendix A1: Derivation of the equation 2.5
9. Appendix A2: From equation 2.5 to equation 2.7
10. Appendix A3: Derivation of the dimensionless spray flux
11. Appendix A4: Deriv. of Stokes viscous no. and Stokes critical viscous no.
12. Appendix A5: Derivation of equation 3.1 describing the coating thickness
13. Appendix A6: Derivation of equation 3.4
14. Notes