Acoustic emission during the solvent mediated cooling crystallization of citric acid

• Published in: Powder technology Vol. 301; pp. 70 - 77
• Main Authors: Wang, XingJun, Fevotte, Gilles, Huang, Ying, Michelitsch, Thomas M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2016; Elsevier
• Subjects: Acoustic emission; Batch processes; Chemical and Process Engineering; Engineering Sciences; Monitoring and control; PAT; Phase transitions; Solution crystallization; Acoustic emission; Monitoring and control; PAT; Solution crystallization; Batch processes; Phase transitions
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2016.05.057

The potential of Acoustic Emission (AE) for controlling crystallization processes is investigated. The sensing technology is successfully applied to monitor the batch cooling crystallization of citric acid (CA) in water. The solvent-mediated phase transition between the anhydrous and the monohydrated forms of CA is clearly detected from the recorded acoustic measurements. A tremendous amount of acoustic data is recorded by the equipment, and the analysis of the data is focused on the evaluation of AE as a new sensor for monitoring the basic steps of the crystallization processes (i.e., nucleation, growth, phase transition, etc.) A time- and frequency-domain analysis is presented which shows the wealth of the technique. It is finally concluded that AE allows very early detection of nucleation events, provides a means of monitoring the development of the crystallization process and allows monitoring phase transition phenomena obtained through cooling. It is thus suggested that acoustic emission could be valuable in the development of new crystallization monitoring and control strategies: this is all the more interesting that the acoustic piezo-sensor is non-intrusive and does not require any sampling of the slurry, two features which are of tremendous importance in the field of cooling crystallization processes.
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•AE allows very early detection of nucleation events.•The solvent-mediated phase transition is clearly detected.•AE could be valuable in the development of new crystallization monitoring strategies.