Crystallization\nof Glycine in a Dual-Zone Continuous\nSlug-Flow Crystallizer to Improve Crystal Size Distribution

A common objective of various crystallization procedures\nis to\nproduce polymorphic pure crystals that have a narrow size distribution\nand a specific average crystal size. A cooling continuous slug-flow\ncrystallizer with silicone oil as the continuous phase and with separate\nnucleation and growth zones is developed for glycine crystallization.\nA supersaturation of 1.5–2.75, residence times of 8 and 11\nmin, and two crystallizer configurations were utilized for crystal\nproduction. The crystallizer can produce crystals with an average\ncrystal size ranging from 70 to 350 μm, with up to 83% yield.\nThe residence time, feed concentration, and temperature of the nucleation\nand growth zones are the major operational parameters regulated to\nproduce the desired crystals without the need for crystal seeding.\nExperimental and computational validation confirmed that increasing\nthe temperature in the growth zone resulted in the formation of crystals\nwith a narrow size distribution. Consistent and continuous operation\nfor several hours was achieved using the crystallizer. Thus, pure\nα-glycine crystals of the desired crystal size with narrow size\ndistribution can be produced continuously using the slug-flow crystallizer\ndesign presented in this study.