Particle-Size Analysis in the Process Environment
The growing trend towards automation in industry has resulted in the development of particle sizing equipment suitable for continuous work under process conditions – even in hazardous areas. The acquisition of particle size information in real-time is a prerequisite for feedback control of the process.
Today the field of particle sizing in process environment is subdivided into three branches of applications.
At-line
is the fully automated analysis in a laboratory.
 |
 |
a) |
b) |
FIG. 1 a) At-line particle sizing module of Sympatec GmbH basing on laser diffraction, with integrated dosing and dry dispersion stage; b) module integrated into a Polysius Polab© AMT for lab automation in the cement industry.
The sample is still taken manually or by stand-alone devices. The sample is transported to the laboratory, e.g. by pneumatic delivery. Several hundred samples can be measured per day allowing for precise quality control of slow processes. At-line laser diffraction is e.g. widely used for quality control in the cement industry.
On-line
places the measuring device in the process environment close to but not in the production line. The fully automated system includes the sampling but the sample is transported to the measuring device. Mainly laser diffraction, ultrasonic extinction, and dynamic light scattering are used.
FIG. 2 Typical on-line out-door application with a representative sampler which scans the cross section on a spiral line in a pipe of 440mm Æ, and a hook-up dry disperser with laser diffraction particle sizer (Sympatec TWISTER 440 & on-line MYTOS).
In-line
implements sampling, sample preparation and measurement directly in the process, keeping the sample inside the production line. This is the preferred domain of laser diffraction (mainly dry), image analysis, focused beam techniques and ultrasonic extinction devices (wet).
 |
 |
a) |
b) |
FIG. 3 a) Typical in-line laser diffraction system with a representative sampler (Sympatec TWISTER & MYTOS), all integrated in a pipe of 100mm Æ; b) In-line application of an ultrasonic extinction (Sympatec OPUS) probe monitoring a crystallization process in a large vessel.
