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™ (Fluidized 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).