A Comparative Study of Various Size Distribution

Abstract

One of the major product specifications of a crystalline material is the crystal size distribution (CSD). In order to monitor and control the CSD in an industrial crystallization process, on‐line sensors are required. Over the years, a number of techniques to measure the CSD have been established. In this paper, three instruments operated in an on‐line fashion and an off‐line method are compared. The instruments were the OPUS, a HELOS/VARIO (both manufactured by Sympatec) and a Malvern 2600c (manufactured by Malvern). They were implemented on an 1100‐l evaporative draft tube baffle (DTB) crystallizer producing ammonium sulfate crystals from aqueous solution. Samples from this crystallizer were also analyzed offline by wet sieving. The results show reasonably good agreement between the different on‐line techniques and the wet sieving technique concerning the shape of the distribution. However, there is a discrepancy regarding the absolute values, which can be explained by the fact that the techniques used are based on different measuring principles.

Advanced Geometrical Modeling of Focused Beam Reflectance Measurements (FBRM)

“…For many particulate products, particle size is an important product specification which should be monitored in line [1]. In the past decade the focused beam reflectance measurement (FBRM) has become one of the most frequently used in line particle characterization techniques [2].…”

Application of in-line monitoring for aiding interpretation and control of dextrose monohydrate crystallization

“…The CSD in dense crystal slurries can be addressed by an automatic sampling and dilution unit (Jager et al, 1987). HE-LOS/VARIO, manufactured by Sympatec Germany, is the second laser diffraction instrument comparable with the Malvern laser diffraction instrument (Neumann and Kramer, 2002). However with this measurement technique, it is challenging to collect a representative sample from an industrial-scale crystallizer and ensure that the temperature is constant enough so that the sample remains representative.…”

Estimation of particle size distributions from focused beam reflectance measurements based on an optical model

“…In order to monitor and control such processes, a characterization of the particles is required. This characterization should be conducted in situ as sampling and off-line particle size analysis often introduce significant errors (Neumann and Kramer, 2002). Focused beam reflectance measurements (FBRM) are very well suited for in situ particle characterization but the measured chord length distribution (CLD) is different from a particle size distribution (PSD) (Hobbel et al, 1991).…”