Nonlinear Oscillations in Ammonium Sulfate Crystallization:  A Comparison of Different Model Predictions

In this paper, the focus is on nonlinear oscillations of ammonium sulfate crystallization. This system has been studied intensively in the past and can be viewed as a standard test system for crystallization processes. The focus is on crystallizers with fines dissolution and classified product removal. Using methods from numerical bifurcation analysis, we investigate how stability in such a system depends on the various operational parameters, like cut sizes and recycle rates of fines dissolution and product classification. Theoretical predictions of three different population models are compared with each other: (i) a model with simple kinetics and ideal fines classification, (ii) a model with complex kinetics involving breakage due to attrition and ideal fines classification, and (iii) a model with simple kinetics and nonideal fines classification. It is found that predictions of the instability regions with models i and ii are rather close. In contrast, the nonideal fines classification can change the stability rather drastically.