Secondary nucleation of α-glycine induced by fluid shear investigated using a Couette flow cell

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Abstract

A Couette cell flow device was designed and an experimental procedure was developed to enable a quantitative study of the effects of fluid shear on secondary nucleation using a fixed seed crystal under controlled supersaturation, temperature, and flow conditions. This approach excludes mechanical impact which is often considered to be the principal source of secondary nucleation, for example through crystal attrition. We found that secondary nucleation rates of a-glycine in aqueous solutions induced by fluid shear were very significant and about 6 orders of magnitude higher than primary nucleation rates at the same conditions. Secondary nucleation rates per seed crystal were found to be about one order of magnitude lower compared with the magnetically stirred vials investigated previously, where a single seed crystal was freely moving, and thus its mechanical impacts could not be ruled out. Computational Fluid Dynamics was used to calculate the wall shear stress along the surface of fixed seed crystals placed in the Couette cell gap at rotation rates between 100 and 600 rpm investigated here. This approach allows relating the secondary nucleation rate to the wall shear stress so that quantitative models can be developed capturing the effects of fluid shear on secondary nucleation kinetic. Such models will then facilitate scale-up and transfer of secondary nucleation kinetics between various equipment used in industrial crystallisation processes.
Original languageEnglish
Number of pages10
JournalCrystal Growth and Design
Early online date10 Jun 2024
DOIs
Publication statusE-pub ahead of print - 10 Jun 2024

Keywords

  • Couette cell flow device
  • fluid shear
  • secondary nucleation
  • α-glycine
  • crystallisation processes

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