On-Line Crystallization Process Parameter Measurements Using Ultrasonic Attenuation Spectroscopy

Abstract

Batch crystallization is an important process in many industries, for example, fine chemicals, foods, and pharmaceuticals. On-line measurement of process parameters, such as crystal size distribution (CSD), crystal shape, solid concentration, nucleation, and growth rates, is important for process understanding and for product quality control. In this paper, L-glutamic acid crystallization process parameters (CSD, concentration, and the onset of crystallization) are monitored in-situ by ultrasonic attenuation spectroscopy, showing that ultrasonic attenuation spectroscopy has significant advantage over existing particle sizing methods such as laser diffraction when measuring concentrated suspensions. However, as currently implemented, the CSD and concentration analyses are conducted off-line because of the complexity of the analysis procedure, which requires lengthy calculation and a large set of physical parameters describing solid and liquid phases. A novel inversion method based on two neural networks working together is developed to determine CSD and concentration directly from ultrasonic attenuation measurements during crystallization. The neural network to recover CSD has 50 hidden neurons and the other with 20 hidden neurons approximates the reference intrinsic attenuation. This approach has been used to obtain parameters of the crystallization process in simulations and experiments. Compared to current analysis methods, neural networks supply solutions essentially instantaneously and without the need to know physical parameters of the solid and liquid phases.

Effects of concentration of dispersions on particle sizing during production of fine particles in wet grinding process

“…Takeda and Goetz [6] and other researchers like Hibberd et al [7] use the technique for characterization of flocculation in different applications. The applications of the technique in domain of crystallization may be consulted in the work of Hipp et al [8], Mougin et al [9], Li et al [10], etc. However, sufficient work has not been performed yet in application of the technique in fine wet grinding processes which are typical in the sense: (i) The change in average particle size of the product is rapid in the grinding mill due to breakage of particles.…”

Applications of ultrasonics in food science - novel control of fat crystallization and structuring

“…For example, we have sized whole milk, separately sizing the protein particle size distribution and that of the milk fat globules [31] [32]. Attempts to use this technique to size crystals during growth have not been overly successful despite considerable effort [33][34][35][36][37][38][39][40][41]because the phase transition itself introduces an additional attenuation term, over and above the scattering terms [30] [42](thermal and visco-inertial) currently included in the inversion models. As a result, empirical methods of analysis were resorted to which suffered from the complicated and variable interaction between the ultrasound field and the crystallising material, we now know that the quasi-continuous acoustic fields can modify the crystal nucleation process [43] and Section 4.3.1 below, An advantage that ultrasound attenuation spectroscopy enjoys over light scattering techniques is its ability to measure concentrated systems and in stirred conditions, so that the emergence of structure can be followed over time.…”

Process Analytical Instrumentation, the Challenges for In-situ Characterization of Complex Particulate Materials

“…Numerous authors [2,3,4,5,6,7,8] have described the benefits of process sensors and stated that there is a rapidly growing acceptance and use. This vision is best summarised in a comment by David Scott from DuPont research in his book Process Sensors [3].…”