Crystallization kinetics of α-ammonium chloride monitored by in-situ measurement techniques

The design of crystallization processes depends on a sound knowledge of the underlying kinetics. Due to the competitive market situation, a faster implementation of reliable processes becomes increasingly critical, by considering all involve length and time scales. The objective of this work is to study the crystallization kinetics of α-ammonium chloride with manganese chloride as a habit modifier using in-situ measurement techniques. Experimental data are recorded using a batch laboratory crystallizer equipped with a laser-backscattering device and an ultrasound probe measuring a chord length distribution and supersaturation, respectively. Besides nucleation and growth described in literature, additional kinetic mechanisms could be identified being a dead supersaturation zone as well as agglomeration. α-Ammonium chloride seems to be an ideal model system, due to the various kinetic mechanisms and morphologies that can be studied. In order to gain a deeper understanding of the processes involved a multiscale map for crystallization kinetics from solution is developed based on physical-based equations helping in visualizing preferred length and time scales of a specific kinetic phenomena.