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64 TABLETING


VERSATILE continuous MANUFACTURING tool


Dr Robin Meier reveals why twin-screw granulation is an efficient starting point to enter the world of continuous manufacturing


T


win-screw granulation (TSG) is a well-established and


extensively described method to perform wet granulation continuously. In the beginning of the 2000s and the following years, the process was described and followed up by several research groups.[1, 2]


continuous process by design and can be a starting point for pharmaceutical companies to launch activities related to continuous manufacturing.


TSG is a fully


Compared to batch granulation, continuous granulation is characterised by a constant in- and output of material through the processing zone. Powder is delivered to two screws, which are co-rotating in a barrel, and transport and shear the material along the process to the granulator outlet. Te major difference between TSG and extrusion is the missing die plate at the end of the machine. Consequently, the wet material does not experience a strong


densification, but solely falls out of the granulator. Te TSG-setup yields several advantages, such as:


l short process residence times <1 min - 10 s


l fast and efficient reaction to process deviations


l reduction of machine footprint and GMP area: the amount of produced granules is determined by the production time


l thereby, elimination of scale- up issues


l mixing and granulation in one step


l possibility to implement 100% in-line product quality- control


l no disposal of failure batches – only non-conforming material is rejected


l execution of experimental plans in shortest time


Te definitive TSG does not


The Bohle Continuous Granulator (BCG) has an openable barrel for fast changeover of screw configuration


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exist. In fact, a TSG provides plenty of adjustable parameters and possibilities to vary the setup. Furthermore, different machines, mainly feeders, can be employed alongside the process, which increase the degree of freedom of the system even further. Te BCG (Bohle Continuous Granulator) is divided into five zones of equal length, from which the last three can be tempered independently from each other. Te temperatures of the different zones are major parameters, which can manipulate the product characteristics, especially during the granulation of freely soluble compounds.[3].


Within the recently developed version


I. Ghebre-Sellassie, M.J. Mollan, N. Pathak, M. Lodaya, M. Fessehaie, Continuous production of pharmaceutical granulation, US 6499984


REFERENCES 1


B1, (2002). 2


E.I. Keleb, A. Vermeire,


C. Vervaet, J.P. Remon, Twin screw granulation as a simple and efficient tool for continuous wet granulation, Int. J. Pharm.,


273 (2004) 183-194. 3


J. Vercruysse, D. Córdoba


Díaz, E. Peeters, M. Fonteyne, U. Delaet, I. Van Assche, T. De Beer, J.P. Remon, C. Vervaet, Continuous twin screw granulation: influence of process variables on granule and tablet quality, Eur. J. Pharm. Biopharm., 82 (2012) 205-211.


of the BCG, a highly effective and flexible tempering of the barrel from above and below the screws is realised. Te barrel of the BCG is openable to allow a fast changeover of the screw configuration as well as a fast cleaning and inspection of the processing zone. Furthermore, each of the five zone offers the possibility to insert different ports in it, to facilitate feeding and the application of process analytical techniques. An important characteristic


is the screw diameter and the length to diameter ratio of the screws. To cover a wide range of throughputs from a few kg/h


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