Endoscopy-Based in Situ Bulk Video Imaging of Batch Crystallization Processes

External bulk video imaging (eBVI) of crystallization processes has proven to be a promising technique for metastable zone determination. In this contribution the endoscopy-based in situ bulk video imaging (iBVI) method is introduced. The video data are processed using the mean gray intensity method and by a digital image processing technique which aims to detect the first crystals during nucleation. The experiments have been carried out in a small-scale calorimeter CRCv4, during which the compensation heater and infrared spectroscopy signals were monitored. It is concluded that monitoring the onset of the apparent nucleation, formation of particles with detectable size, using the mean gray intensity (MGI) trend delivers similar performance to the calorimetric and IR spectroscopy signal, whereas the crystal recognition method is the fastest, allowing detection of nucleation earlier. The endoscopy-based nucleation monitoring technique is proposed as a complementary tool to existing process analytical technologies (PAT) since it provides an in situ, low-cost, robust, probe-based method for metastable zone identification which can be easily integrated and automated with existing laboratory hardware and software.