Application of Ultrasonics in the On-line Determination of Supersaturation

Abstract

An ultrasonic technique is used to develop a method based on the measurement of both ultrasonic velocity and temperature of the supersaturated media for the on-line determination of the supersaturation. It is demonstrated by the example of aqueous K 2 SO 4 solution in a seeded batch crystallizer. The feasibility of this technique was investigated using a commercial available sensor. The experimental measurements for the desupersaturation versus time trajectory proved that this technique can be successfully employed to measure supersaturation with sufficient accuracy and precision. Such sensor is preferred in the on-line application due to its fast response and the availability to be applied directly in the slurries without any need to the solid-liquid separation.

Ultrasonic crystallization monitoring technique for simultaneous in-line measurement of liquid and solid phase

“…The calibration procedure for the liquid concentration is described in detail e.g. in [9]. For the investigated urea-water system the following correlation (R 2 ¼0.999) for the concentration (c), which is dependent on the temperature (T) and the ultrasonic velocity in the liquid phase (v l ) could be found as…”

“…3 the protected sensor is capable to measure accurately in-line the liquid concentration during the dynamic crystallization process. This was proven and explained in detail in previous studies [9,10]. The carried out investigations aimed at showing the significant changes in the concentration if crystal growth takes place in consequence of the precisely generated supersaturation (compare with temperature profile).…”

“…In this study, a robust ultrasonic technique (single frequency) is introduced, which belongs to the series of new inexpensive PAT developments. This PAT is still only known to be a fast, easy and robust analyzing tool for the liquid phase [9,10]. It is aimed to show in a proof of concept that besides the liquid concentration the solid phase also (with respect to suspension density and mean crystal size) can be accurately monitored in a dynamic crystallization process by the ultrasonic crystallization monitoring technique (UCM).…”

“…These techniques include, but are not limited to, conductivity [6], density [7], turbidity [8], ultrasonic (single frequency) [9,10], in-line microscopy [11], laser backscattering (FBRM or 3D ORM) [5,[12][13][14], laser diffraction [15], attenuated total reflection-Fourier transform infrared (ATR-FTIR) [16] or ultrasonic attenuation spectroscopy (UAS), which correlates ultrasonic attenuation with a spectra of frequencies [4,[17][18][19][20][21][22]. All these techniques are established and applied to monitor/control crystallization processes.…”

Monitoring concept of single-frequency ultrasound and its application in dynamic crystallization processes

“…Here, the ultrasound-based technologies have clear advantages, because most materials are ultrasonically transparent and hence allow the analysis of a broad variety of sample types [1,[11][12][13][14]. The overlapping effects of liquid and solid state, however, make the analysis of ultrasound challenging.…”