Fluid-bed coaters

Chisso-Asahi uses a spouted bed process for the production of their coated materials (12). A 12,000 t/yr faciHty is located in Japan. The semicontinuous process consists of two batch fluid-bed coaters. A dilute polymer solution is prepared by dissolving 5% polymer and release controlling agent into a chlorinated hydrocarbon solvent such as trichloroethylene. The solution is metered into the spouted bed where it is appHed to the fertilizer core. Hot air, used to fluidize the granules, evaporates the solvent which is recovered and reintroduced into the process. Mineral talc, when used, is either slurried into the polymer solution or introduced into the fluidizing air. 

Test runs using a 150 mm diameter fluid bed coater indicated that a batch of 2 kg of material could be coated using a liquid spray rate of 10 ml/min for 50 minutes and a fluidizing gas rate of 40 scfm. It is desired to scale-up this process to a batch size of 200 kg of bed material. For the scaled up process, determine the bed size the liquid and airflow rates and the new run time. 

Equipment type The type of coater will need to be selected. Conventional or perforated pan and fluid bed coaters are potential options. 

Coater load What is the acceptable tablet load range of the equipment Having too large a pan load could cause attrition of the tablets because of the overall tablet weight in the coater. In the case of a fluid bed coater, there may not be sufficient airflow to fluidize the tablets. 

Extrusion/spheronization (marum) Screw extruder, Marumerizer, Fluid bed coater Inexpensive raw materials Continuous process Complex multi-step process High dust during process and in product Requires highly concentrated enzyme... 

Fluid bed (layering/ coating) Fluid bed coater Single, contained reactor Flexible formulation Tough uniform granules Batch process Difficult rework... 

A more detailed overview of the development of continuous fluidised bed systems is covered in a review by Teunou and Poncelet (2002). Figure 16.7 shows a schematic diagram of a continuous top-spray fluid bed coater. 

Figure 372. Schematic representations of the product handling sections of three fluidized bed coaters. (a) Top spray, (b) tangential spray (rotary fluid bed coater), (c) bottom spray (Wurster coating system)...

The methionine and lysine monohydrochloride cores are produced by a melt-binder extrusion spheronization process. Particle diameters are ranging from 1.5 to 2.5 mm. The coating is composed of hydrophobic substances and a pH-sensitive polymer which is able to dissolve or swell in the acidic abomasal medium. The cores are coated in a fluid-bed coater using a solvent-free process (Fig. 3). 

Top spray. In the top spray system, the coating material is sprayed downward on to the fluid bed such that as the solid or porous particles move to the coating region, they become encapsulated. Top spray fluid-bed coaters produce higher yields of encapsulated particles than either bottom or tangential sprays. 

After drying the particles in a fluid-bed dryer and removal of over- and undersized materials by sieving, the beads are coated in a fluid-bed coater with one or two coating layers to obtain white or colored beads and to have a tough protecting layer that completely avoids the development of enzymatically active dust. 

With the high demand for encapsulated materials in the global market, fluid-bed coaters have become more popular. They are used for encapsulating solid or porous particles with optimal heat exchange [105]. The Hquid coating is sprayed onto the particles and the rapid evaporation helps in the formation of an outer layer on the particles. The thickness and formulations of the coating can be obtained as desired. Different types of fluid-bed coaters include top spray, bottom spray, and tangential spray (Fig. 1.16). 

Raman and Gray (1994) layered PST, glycerin, and a wax and surfactant blend onto nonpareil seeds in three passes using a fluid-bed coater. These were then compressed into tablets. The in vitro dissolution results indicated some delayed release. 

Trichoderma Gist-brocades MgS04-7 H2O (24) Glatt WSG-60 fluid-bed coater 80-50 105 + 120 12 30 111 + 120... 

Requirements for achieving and maintaining uniform solids concentration throughout the tank—of interest particularly for slurry catalyst reactors and for feeding downsneam equipment (e.g., centrifuges, continuous stirred tank reactors, fluid bed coaters)... 

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