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Precision Coater (Niro)
less contact. Further, it is also important that part
of the air moves horizontally toward the partition With reference to the traditional fluidized bed
to provide the transport energy for moving coater, a large portion of the air flows into the bed
particles to the airlift. The ratio of air volumes around the column. This allows particles to flood
moving in these two directions is dependent upon into area around the spray nozzle by virtue of the
the geometry of the apparatus. Different types of hydrostatic head of the bed. The Precision coater57
air distributor plates have been designed such as (GEA-Aeromatic Fielder, Eastleigh Hampshire,
Gill Plate, Precision coater (Niro) and Huttlin s air UK; presently Niro Inc.) is similar to the Wurster
distribution plate. coater except for its mode of air distribution. The
air distribution plate in the Precision coater
consists of a perforated plate connected to the
Swirl Accelerator (GEA-Aeromatic Fielder). The
The Gill Plate
Swirl Accelerator functions to swirl and accelerate
In past, the sandwich-type construction was the inlet air to impart spinning movement and
employed in fluid-bed systems. In this typically high velocity to particles as they transport
a fine screen of 60-325 mesh covered the air through the partition column where coating takes
distributor plate which retained the finer product place. This modified process changes fluid
in the container. However, the major drawback of dynamics of the particles. Thus in the precision
this was the challenge to keep the screen and air coater more amounts of air are directed into the
distributors clean. To solve this problem, in 1990s coating column via an insert plate and the swirl
the overlap Gill Plate was introduced.56 This plate accelerator as compared to the Wurster coater.
provided excellent air distribution and also there This specific design creates a much higher process
was no need of the fine screen. air speed adjacent to the nozzle and generates a
Batch fluid-bed technology for Niro is developed low-pressure zone that sucks particles into the
by sister-company Aeromatic-Fielder (Switzer- core of the coating tube. The air with high speed
land and UK). Their systems use Gill PlateTM causes individual particulates to spin allowing a
air distributor plate (Fig. 6). The Gill plate is much more uniform coating. Accelerator inserts
extensively employed in continuous fluid-bed with smaller inlet diameters generates higher air
dryers. Unlike the sandwich-type air distributor, velocities, which increases the pressure differen-
the Gill plate is easier to clean. These nonsifting tial across the partition gap. However, it must
Gill plate air distributors are typically appro- be noted that very high air velocities may cause
priate for a unit in which the container is fixed particles to hit onto the top of the chamber causing
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 11, NOVEMBER 2009 DOI 10.1002/jps
FLUIDIZATION TECHNOLOGIES 3945
attrition. The swirl accelerator generates a rota- centre of the bottom. In the equipment there are
tional component to the air stream which when openings at the bottom for spray guns.
combined with the high speed of the air stream
ensures that the individual particles are kept
Air Lift
separate so that it is possible to operate at higher
humid conditions without the risk of agglomera-
The travel of air from the perimeter of the plate
tion. In the process, evaporation rate is also higher
toward the partition should be horizontal in order
such that particles are dried and will not
to move particles at a uniform rate from all areas
agglomerate long before they return to the bed
of the bottom of the down flow bed. The air
around the coating tube. Since the partition gap is
entering through the outer areas of the support
known to affect the pressure differential, it has
plate will not move toward the air lift unless that
greater influence on MFR in precision coating
pathway offers less resistance to flow than the [ Pobierz całość w formacie PDF ]
