Fluidised bed granulation and coating: Applications to materials, agriculture and biotechnology

In this review, firstly fluidised bed granulation and coating as a concept is introduced and critically compared briefly with other similar techniques. The way in which different types of granules can be produced is then discussed and related to the balance of break-up forces and binding strengths. This basic concept is then linked to the conditions of atomisation of the liquid feed, to the different independent techniques for controlling break-up forces and to the effect of the properties of the material to be granulated. This section concludes with a consideration of binder selection, both underlying theories and practical selection. Finally, three applications of the technique are introduced in which particles of desired properties have been engineered. These are i) the production of tungsten carbide granules for cutting tools and specialist applications; ii) the coating of vegetable seeds with chemical and bio-control agents; and iii) the manufacture of selective adsorbent particles for use in bioproduct recovery. The article highlights the great versatility of the technique and how an understanding of it can be used to advantage to produce particles to meet a wide range of specifications.