L.B. Bohle White Paper: Fluid Bed Systems for drying, granulation and coating

The latest White Paper from pharmaceutical machinery leaders L.B. Bohle Maschinen und Verfahren GmbH (L.B. Bohle) provides insights on the application of its fluid bed dryers to advanced granulation and coating in tableting.

The technical paper reflects on the implications of L.B. Bohle’s development of fluid bed technology into a combined drying and granulation platform with the addition of spray nozzles, tangentially mounted, allowing pellet coating to be performed as well.

Bohle’s BFS Series Fluid Bed Dryer Granulators with tangential nozzles disposed around a central   BUC® Bohle Uni Cone also offer other advantages, such as significantly reducing required fluid levels and expansion volume, thereby  bringing down overall machine height and installation space, as well as accelerating product transfer and cleaning times with overall efficiency gains.

With all that in mind, the paper details three case studies to highlight the versatility of the Bohle Fluid Bed System in various applications.

• Case study I: A ‘classic’ wet granulation experiment on placebo formulation of fine lactose and corn starch as fillers and povidone as wet binder, performed using BFS 30 pilot scale fluid bed system containing two spraying nozzles and typically suitable for batch sizes ranging from 5 to 40 kg. Sieve analysis results displayed proper agglomeration of the original powder with quite a narrow particle size distribution and small amount of fines, with lactose granules also exhibiting spherical shape as is typical for tangential fluid bed agglomerates, an excellent Hausner Factor of 1.1 and a bulk density of 0.54 g/mL.
• Case study II: A pellet coating study that aimed to produce a sustained release multiparticulate capsule formulation using a BFS 30 in the context of a reformulation of commercial product. For this already existing product a classical fluid bed with Wurster insert was used for production and pellet curing was performed in a traditional oven. The trial used 15kg of 500μm sized Cellets® successively coated with an active layer followed by sustained release polymer dispersion. After curing, dissolution was tested in demineralized water which proved successful sustained release coating and successful reformulation.
• Case study III: A further pellet coating study focusing on a sustained release formulation processed in production scale Bohle BFS 120 and BFS 240 Fluid Bed Systems. Cellets® of 250μm diameter were coated with API and a typical wet binder until 25% mass gain. The second coating layer consisted of  a sustained release polymer solution  containing ethyl  cellulose  until 120% mass gain. Coating in a BFS always led to high yields (≤ 0.4 % agglomerates) even after processing for seven days in a three-shift operation. After a short drying phase at same inlet air conditions for several minutes and cleaning of spray guns, a sustained release polymer dispersion could be started, culminating in curing, again using the BFS platform, set to 950 m³/h inlet air volume at 50° C. This required only three hours, compared to 24 hours needed to achieve the same curing results in a traditional oven.

In summary, the paper shows how using tangential fluid bed technology represents state of the art in pharmaceutical manufacturing for particle coating, granulation and drying. Furthermore with the innovative Bohle Uni Cone BUC® a complete particle fluidization is assured which leads to high coating uniformities and high yields in the final product due to absence of particle twinning effects.

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