Thesis

Investigation of batch and continuous crystallisation processes using non-invasive Raman and acoustic emission spectrometries

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Awarding institution
  • University of Strathclyde
Date of award
  • 2013
Thesis identifier
  • T13736
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Abstract
  • Crystallisation of L-glutamic acid (LGA) and D-mannitol were studied in batch and continuous reactors using non-invasive, wide area illumination Raman spectrometry to identify the nucleation point, monitor crystal growth and identify the polymorphs formed. Non-invasive broadband acoustic emission (AE) spectrometry was also investigated as a means to monitor the crystallisation profile (by integrating the AE intensity over specific frequency ranges) and changes in particle size (by ratioing the intensities at high and low frequency regions). A design of experiments approach evaluated the effects of solution concentration, oscillation frequency and amplitude, and final temperature on crystal formation and polymorph transformation for batch and continuous oscillatory baffled reactors. For both compounds, concentration had the biggest impact on the particle properties while the main interaction was between the oscillation frequency and amplitude. Comparisons were made with results from crystallisations in batch stirred tank and continuous mixed suspension, mixed product removal (MSMPR) reactors. Metastable α-LGA was more easily obtained in both continuous reactors than conventional batch reactors. Narrower size distributions (e.g. spans of 1.5 - 2 and 4 - 8, respectively) and lower yields (e.g. 20 - 50% and 30 - 70%, respectively) were obtained in the continuous OBR than the MSMPR. The continuous OBR exhibited limited operating conditions, outside of which poor nucleation or blocking of the reactor occurred. The MSMPR reactor was more versatile and could be operated for up to 70 hours compared to several hours for the continuous OBR. The study of D-mannitol in stirred tank and batch OBR explained how different operating conditions (especially oscillation frequency and amplitude) affected the polymorph formed, the rate of crystal formation, particle size range, and the degree of polymorph conversion. The metastable α- and the stable γ-forms were the predominant polymorphs obtained; higher solution concentration and mixing intensity gave more alpha and vice versa for the gamma form.
Resource Type
DOI
Date Created
  • 2013
Former identifier
  • 1032556

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