To avoid the preparation of seed crystals some concepts have already been developed to integrate the nucleation into the crystallization process. In addition, high yield, high purity, and specific particle morphology are often required for sufficient product quality. Clogging should be avoided, while a narrow crystal size distribution (CSD) is targeted to simplify and minimize post-crystallization operations. įor continuous operation in crystallization, many aspects have to be considered. Furthermore, the continuous mode has advantages, such as smaller hold-ups, higher product reproducibility, and space-time-yield.
It is not necessary to switch the operation mode from small scale batch to the continuous production of bigger quantities, smallest quantities can already be continuously produced, and similar equipment concepts can be transferred more easily to larger scales. The continuous operation of small-scale equipment is of utmost importance for accelerated process development. No distinct threshold for nucleation could be determined in a wide range of supersaturations of l-alanine in water Since the interest and demand for small-scale, continuous crystallization increases, seed crystals were generated in a coiled tube via sonication and optically investigated and characterized. Nucleation is non-invasive detected using a flow cell equipped with a microscope and camera. Amino acid l-alanine dissolved in deionized water is employed in a supersaturation range of 1.10 to 1.46 under quiet and sonicated conditions. The CFI design was chosen for improved radial mixing and narrow residence time distribution, which is also investigated.
For this purpose, a tube with an inner diameter of 1.6 mm and a length of 6 m was winded in a coiled flow inverter (CFI) design and immersed into a cooled ultrasonic bath (37 kHz). It was found that there is no sharp boundary but rather a transition zone for nucleation under sonication.
Nucleation in continuously operated capillary coiled cooling crystallizers is experimentally investigated under the influence of ultrasound.
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