(146b) Fluid Bed in a Flash

Fluid Bed in a Flash

O. Scheibelhofer¹, Roland Hohl¹,
Sharareh Salar Behzadi¹, Detlev Haack², Kai Koch³,
Stefan Sacher¹, Jose C. Menezes¹, J. G. Khinast^1,4

¹ Research
Center Pharmaceutical Engineering GmbH, Graz, Austria

²
Hermes Arzneimittel GmbH, Munich, Germany

³
Innojet Herbert Hüttlin, Steinen, Germany

⁴
Institute for Process and Particle Engineering, Graz University of Technology,
Graz, Austria

Email for correspondence: otto.scheibelhofer@rcpe.at
(O. Scheibelhofer),

khinast@tugraz.at (J.G. Khinast)

Fluid Beds are a versatile and widely used
unit operation in the pharmaceutical industry. Putting to use their property of
very large particle to air contact surface, they are an advanced step for
drying, coating and more. A great deal of interest has already been invested,
concerning the properties of fluid beds, especially their geometry and flow
pattern. Mostly, this is a field for simulations.

Nonetheless, the efficiency of fluid beds
is often driven by the experience of their operators. This is a result of fluid
beds being very sensitive to subtle changes, which can affect the flow pattern
significantly, even dis-enabling the fluid bed process as a whole. Even more
so, this increases the difficulty of placing sensors in such environment,
making systematic experimental investigations an exhaustive work.

To overcome some of these difficulties,
near-infrared spectroscopy seems a natural choice, for two reasons. First, the
method is non-invasive, or even contactless, so to avoid the disturbance of the
established flow pattern. Secondly, the method can be very fast and can
therefore cope with the time-scale of flow inside the bed.

A single NIR probe is used for monitoring
the fluid bed and following the trajectory of our process, for this a process
NIR from Sentronic is used.

However, as there are different zones of
flow and progress inside the bed, a single probe is not enough, to get an idea
of the overall maturity inside the fluid bed.

Here we used a new spectrometer prototype
provided by EVK, Raaba, Austria in order the monitor a coating process. The
prototype is based on a push-broom principle, but instead of a line, a
standardized port plate enables the mapping of different near-infrared probes,
via a prism-grating-prism system onto the detection chip. As a consequence,
several positions inside the fluid bed can be monitored simultaneously, with a
frequency of several Hz. even more, the records of the probes can be directly
compared, as they are guaranteed to be recorded at the same time, and there is
no spectrometer drift in between probes, etc.

The probes are distributed inside the fluid
bed vessel at carefully chosen positions, at the wall, in order to not disturb
the flow pattern, but give at the same time the most relevant information.

The information gained is of value twofold.
First, it tells about the process itself, and can be used to estimate necessary
process time and quality. Second, it tells about the mechanisms inside the
fluid bed, spatial differences, etc.; which is very valuable for final probe
positioning, the task of up-scaling, and more.

Estimation of the sample positions and the
process is done with risk analysis, and design of experiments is also used for
generating an experimental setup pattern. Within the multiprobe measurement
system, we will also evaluate the sample position of the single probe.

Figure
1: The Ventilus 2.5 fluid bed
reactor is shown., with the Sentronic NIR probe attached.