Dynamic modeling of continuous evaporative cooling KCl-NaCl crystallizers

Abstract

Previous work on the modeling of potash crystallizers has been mainly limited to the estimation of crystal size distribution (CSD) in the presence of only one solid component (KCl). In the present study, an attempt has been made to develop a model that incorporates NaCl as a second component that may co-precipitate along with KCl under certain operating conditions. Addition of water to prevent co-saturation or as a means of internal fines dissolution is also taken into consideration. External fines dissolution using a heat exchanger is incorporated in the model. In addition to the CSD, the model is able to predict crystal impurity resulting from co-saturation with NaCl. The predictive capability of the model is tested using limited dynamic experimental data obtained from a 1 m3 pilot plant continuous evaporative crystallizer and the steady-state experimental data from a two-stage evaporative Swenson DTB industrial potash crystallizer circuit. In both cases, a good agreement between the model predictions and the experimental data was noticed.