l-Glutamic Acid Precipitation: Agglomeration Effects

In this work, the effect of agglomeration on the final particle size distribution is investigated for batch precipitation processes carried out in stirred tank reactors. Agglomeration kinetics of α l-glutamic acid was determined based on seeded batch experiments by a combination with a population balance model and an integral parameter estimation technique. Different modeling approaches for the description of agglomeration are applied and assessed. The empirical model only takes into account the influence of supersaturation and stirring rate on the agglomeration process, while it neglects size dependencies. In the more rigorous modeling approaches, the agglomeration kernel is decomposed into a size-dependent collision frequency and an agglomeration probability. Computational fluid dynamics (CFD) is used to model the turbulent flow in the stirred reactor and to extract information about the shear rate distribution, which in turn can be used to incorporate the dependence of the agglomeration kernel on the local shear rate. The population balance model accounting for nucleation, growth, and agglomeration is used to predict the particle size distribution in precipitation experiments.