A conditional sampling controlled diffraction-based particle sizing instrument Available to Purchase

The development of a process control and monitoring instrument for particle size distribution measurements in high temperature, turbulent environments is reported. The instrument consists of a standard Malvern 2600 HSD particle size analyzer augmented with conditional sampling hardware. Conditional sampling was implemented to ensure that beam wander effects in the measurements were eliminated. This was accomplished by ensuring that the diffracted light profile, resulting from scattering by particles in the sample volume, was recorded only while the laser beam was correctly aligned on the Malvern detector. The utility of the technique was demonstrated through a simple experiment during which beam wander, simulating a similar effect caused by refractive index variations in a turbulent system, was applied to the diffracted light profile resulting from laser beam propagation through a known size distribution of polystyrene micro-spheres. Results indicate that the Sauter mean diameters (SMDs) of the sample, obtained in the presence of the “synthetically generated turbulence”, were consistent with static readings for small induced beam wander frequencies and amplitudes. Data at higher frequencies or amplitudes was unattainable due to the bandwidth limitations of the electro-mechanical shutter used in the current version of the conditional sampling hardware. Further studies are underway to improve instrument bandwidth by substituting an acousto-optic modulator for the shutter. These results will be reported in a subsequent publication.