Induced nucleation by gassing and its monitoring for the design and operation of an MSMPR cascade

Flow Map for Hydrodynamics and Suspension Behavior in a Continuous Archimedes Tube Crystallizer

The Archimedes Tube Crystallizer (ATC) is a small-scale coiled tubular crystallizer operated with air-segmented flow. As individual liquid segments are moved through the apparatus by rotation, the ATC operates as a pump. Thus, the ATC overcomes pressure drop limitations of other continuous crystallizers, allowing for longer residence times and crystal growth phases. Understanding continuous crystallizer phenomena is the basis for a well-designed crystallization process, especially for small-scale applications in the pharmaceutical and fine chemical industry. Hydrodynamics and suspension behavior, for example, affect agglomeration, breakage, attrition, and ultimately crystallizer blockage. In practice, however, it is time-consuming to investigate these phenomena experimentally for each new material system. In this contribution, a flow map is developed in five steps through a combination of experiments, CFD simulations, and dimensionless numbers. Accordingly, operating parameters can be specified depending on ATC design and material system used, where suspension behavior is suitable for high-quality crystalline products.

Protein crystallisation with air bubble templates: case of gas–liquid–solid interfaces

Crystal formation on air bubble–liquid interface, as soft template to efficiently prompt nucleation of proteins.

Microbubbles as Heterogeneous Nucleation Sites for Crystallization in Continuous Microfluidic Devices

Injecting a stream of microbubbles and thereby introducing a heterogeneous interface is proposed for enhancing nucleation and controlling particle formation in continuous microfluidic devices. Different gas and liquid flow rates were investigated to establish the two-phase flow regime map and to identify the optimum characteristics for microbubble flow. Subsequently, the effect of microbubbles was studied for the cooling crystallization of paracetamol. An enhanced nucleation rate compared to that in the operation without bubbles was observed and the presence of microbubbles results in the formation of more crystals, which indicates that nucleation is faster than that in operation without bubbles, i.e., the metastable zone width is reduced. Determining the crystal yield confirmed that a larger mass of crystals is obtained in a two-phase flow with microbubbles. Furthermore, results showed that the presence of microbubbles allows crystallizing continuously without clogging of the microreactor.