ONLINE PARTICLE-SIZE MEASUREMENT IN DENSE SLURRIES

An automatic dilution unit which enables fast and representative dilution of a process stream, down to the solids concentration required for Fraunhofer diffraction size measurements, has been developed. This unit has been built and tested on a 1-m3 continuous crystallizer producing ammonium sulphate. A Malvern 2600c particle size analyser is used as the actual measuring device. The combined system of dilution unit and sizer is integrated into a supervisory control system. From experimental data, the reproducibility of the average size (m4/m3), the second, third and fourth moments of the Particle Size Distribution (PSD) is estimated to be 2.2%, 2.7%, 2.3%, 3.3%, respectively. The observed trends of the PSD are in accordance with results obtained by sieve analysis. The measurement frequency attained is 30 times per hour. © 1990.