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Petrak Dieter, Dietrich Stefan, Eckardt Günter, Köhler Michael
Advanced Powder Technology, Volume 22, Issue 2, March 2011
Abstract
Sizing of particles in industrial processes is of great technical interest and therefore different physical-based techniques have been developed. The objective of this study was to review the characteristics of modern sizing instruments based on a modified fibre-optical spatial filtering technique (SFT). Fibre-optical spatial filtering velocimetry was modified by fibre-optical spot scanning in order to determine simultaneously the size and the velocity of particles. Sizing in-line instruments of Parsum GmbH use these measuring principles and may be adapted to different process conditions. Particles with sizes of 50–6000 μm and velocities up to 50 m/s may be measured by the probe system IPP 70. An overview is given to real-time sizing of particles in different technical applications: fluid-bed granulation, high shear wet granulation, Wurster coating, mixing, spray drying, crystallization and milling.
Additional Information:
Parsum-Probes by that utilize SFT measure in-line and can be inserted directly into a process vessel, granulator or line. They are able to measure reliably, even in damp, sticky environments with a typical measurement range spanning 50 to 6000 microns. In-line dispersion systems may be used to ensure consistent presentation, and/or dilute the process stream, where necessary, but these are integral to the probe. SFT probes have no moving parts and are available in different lengths which means that the technology transitions easily from development through to commercial production.
SFT is a number-based, chord length, sizing method that collects data for individual particles to develop a particle size distribution. It involves both spatial filtering velocimetry and spot scanning. Particles falling through a laser beam cast a shadow, interrupting the flow of light to a linear detector array made up of optical fibres. Particle velocity is calculated from the sequential interruption of linearly neighbouring fibre elements of the spatial filter detector, each particle triggering a burst signal, the frequency of which is directly proportional to particle velocity. Particle size is determined using a secondary signal, the pulse signal, which is a measure of the length of time for which the particle blocks a single optical fibre . Measuring a large number of particles generates statistically valid results from which various size parameters and volume-based distributions are derived, depending on the needs of the user.
(Link: www.parsum.de , www.malvern.com )
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