(286f) Continuous Cooling and Membrane-Assisted Crystallization with Airlift Crystallizer

Crystallization plays a substantial role in separation and purification of chemical and pharmaceutical compounds. The common problems in batch crystallisation processes often include large variations in the product quality per batch, inflexibility of the process and complex process controllability. The reason could be difficult handling of wet or semidry crystalline materials and high necessity of operating labour force in batch processes [1]. Furthermore, a common problem in conventional stirred crystallizers is the entanglement of multiple phenomena such as primary nucleation, growth and secondary nucleation.

Initially, batch experiments with airlift crystallizer confirmed that it can suppress secondary nucleation to a higher level than conventional stirred crystallizer [2].

Subsequently, experiments with membrane unit showed its feasibility in assisting crystallization processes by providing sufficient rate and level of supersaturation.

Based on results from membrane unit experiments effective parameters are known as feed temperature and air flow rate. The rate and level of supersaturation can be directly controlled and manipulated by changing these parameters for different process requirements.

In this study the performance of a continuous operated airlift crystallizer is discussed and secondly it is shown that membrane distillation can be applied as an alternative technology for the generation of supersaturation in combination with an airlift crystallizer.

Next, membrane unit and airlift crystallizer were combined. The setup is capable of operating in batch and continuous mode, cooling and membrane-assisted operation. Membrane-assisted Crystallization (MaC), firstly meet the requirements for decoupling the crystallization phenomena toward a more flexible process optimization and secondly it has the potential to operate in continuous mode and to significantly reduce energy consumption and operating labor force.

In this contribution feasibility of performing cooling and membrane-assisted crystallization using airlift crystallizer is presented. It is shown that a continuous membrane-assisted airlift crystallization is believed to be more controllable, flexible and energy efficient.

A model is developed and validated which is capable of predicting the membrane flux and level of supersaturation generation and the crystallization kinetics. The model is used to design and optimize the process.

1. Myerson, A., Handbook of industrial crystallization. 2002: Butterworth-Heinemann.

2. Lakerveld, R., J.J. Van Krochten, and H.J. Kramer, An air-lift crystallizer can suppress secondary nucleation at a higher supersaturation compared to a stirred crystallizer. Crystal growth & design, 2014. 14(7): p. 3264-3275.