Integrated membrane emulsification and solution cooling crystallization to obtain a narrow and predictable crystal size distribution

Abstract

• A novel concept integrating membrane emulsification and solution crystallization. • Membrane emulsification enabled the confinement of solution crystallization. • Different droplet size distributions showed different yield and crystal quality. • A narrow crystal size distribution was achieved through monodisperse droplets. • The crystal number density was affected both by supersaturation and droplet size. Solution crystallization processes are challenged by the need to control crystal quality attributes such as the crystal size distribution (CSD). Emulsion crystallization is an attractive process intensification strategy to control crystal quality attributes through miniaturization. Droplets of an emulsion can act as tiny crystallizers by confining crystals so that crystal nucleation and growth are limited by the droplet size with available supersaturation. This work presents a novel process concept based on the integration of membrane emulsification and solution crystallization. A water-in-oil emulsion is created through membrane emulsification and glycine is crystallized inside droplets by cooling. The process is characterized in terms of the droplet size distribution, crystal number density, and CSD as a function of the emulsification method and supersaturation. Large and monodisperse droplets obtained from membrane emulsification can achieve a narrow and predictable CSD with higher productivity compared to a mechanical emulsification method. The crystal number density is strongly affected by the initial supersaturation when using membrane emulsification but not the final CSD. In contrast, the CSD changes with supersaturation when applying a mechanical emulsification method. The CSD obtained from a conventional bulk crystallization process is broader and lacks the control imposed by the uniform droplets from membrane emulsification.