The Role of Residence Time Distribution in the Continuous Steady-State Mixed Suspension Mixed Product Removal Crystallization of Glycine

Abstract

In this work, a vacuum-driven intermittent transfer technique has been implemented to solve transfer line blockage issues and facilitate steady-state cooling crystallization studies of α-glycine in a single- and two-stage mixed suspension mixed product removal (MSMPR) crystallizer. Experimental residence time distribution (RTD) analysis of the stirred tank MSMPR cascade is performed using an imperfect pulse method of the axial dispersion model to benchmark the mixing performance against that of tubular crystallizers and determine the influence of RTD on steady-state size distribution of α-glycine product. Process analytical technology (PAT) is used to monitor and understand crystallization process dynamics, and the effect of MSMPR operating temperature, mean residence time, and number of MSMPR stages on mean particle size, crystal size distribution, and yield is studied. Results show the significance of nucleation and growth mechanisms alongside RTD in determining steady-state size distribution, and the need for optimum control of supersaturation to benefit from improved RTDs provided by multistage MSMPR crystallizers.