New fluid bed coating technology is widely used during gasification and coal combustion processes. The fluidized bed systems are widely used in the gas and coal fuel industry to lower emissions and pollution associated with the fuel production process. A fluidized bed is formed when any number of solid particulate substances (usually kept in a holding vessel) are placed under appropriate conditions to cause the solid/fluid mixture to behave as a fluid. This process is typically achieved through a few common fluid bed coating procedures such as top-spray coating, bottom-spray and tangential spray coating.
Top-spray coating is frequently used by the food, feed and chemical industries as the function of the film mainly serves to improve storage. The film limits and protects against moisture, oxygen or light. Bottom-spray coating is a processing option that utilizes the energies and controls the fluid bed, in order to create a pneumatic mass transport inside a special insert. The special insert consists of a perforated bottom screen, with defined free areas. Most of the air during the process is channeled through the center of the screen, via a tube, which produces a venturi effect. All of this allows for the highest possible coating quality, which is a requirement to produce defined and reproducible drug delivery profiles.
With tangential fluid bed coating, the process involves psychical principles quite similar to bottom-spray coating, instead, the motion of production is provided by a motor driven rotor disc. Otherwise, the quality producing parameters are the same. Other circulating fluidized bed processes, known as bubbling beds can be used as boilers during small scale operations. Bubbling fluidized beds are commonly used as chemical reactors because they provided an appropriate environment. This technique is also becoming more common in aquaculture preparations, for the production of shellfish in integrated multi-trophic aquaculture systems.
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