An alternative process is to produce the active in a granular form during primary pharmaceutical production. These granules can then be blended with the excipients during secondary production. Most excipients used today can be purchased in a quality suitable for direct compression and an additional granulation/drying step then is not required. Alternatively active and excipients can be mixed together in the liquid phase and then be dried- as granules- together. To do so it is necessary to carry out the drying at the end of primary production in a FSD™ (Fluidised Spray Dryer) spray dryer.
The feed, which can be an aqueous or organic solution or a suspension of solids is pumped to the atomisation device which can be a nozzle or a rotary atomiser (spinning disk). Here the liquid droplets and the hot drying gas are brought into contact, usually in a co-current mode. Using
the thermal energy of the hot air the liquid evaporates and the solids form particles. The exhaust air carrying vapour and particles leaves the drying chamber at the base. These particles are then removed from the exhaust air stream by gravity, a cyclone, a filter or a combination of these methods. Depending on the TS (Total Solids) of the feed, the atomisation and the material characteristics, the process will form single particles in a range between 2 and 250 μm. Drying single particles larger than typically 100 μm requires mostly the use of tall form dryers (an extremely high execution of a spray dryer).
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