A Short-Cut Method for the Quantification of Crystallization Kinetics. 2. Experimental Application

Abstract

For the design of crystallization processes, the specific substances have to be characterized in terms of their thermodynamic properties but also with respect to the corresponding crystallization kinetics. In an accompanying theoretical study, a short-cut-method was suggested and demonstrated for the quantification of different kinetic mechanisms, i.e. growth, dissolution and nucleation. Here, this method will be utilized for the estimation of parameters comprised in kinetic sub-models for three different substances. The experimental procedures as well as the data analysis will be discussed and the quality of the parameter estimates will be evaluated by comparing predictions of a population balance model using the identified parameters with the results of corresponding validation experiments. AbstractFor the design of crystallization processes, the specific substances have to be characterized in terms of their thermodynamic properties but also with respect to the corresponding crystallization kinetics. In an accompanying theoretical study, a shortcut-method was suggested and demonstrated for the quantification of different kinetic mechanisms, i.e. growth, dissolution and nucleation. Here, this method will be utilized for the estimation of parameters comprised in kinetic sub-models for three different substances. The experimental procedures as well as the data analysis will be discussed and the quality of the parameter estimates will be evaluated by comparing predictions of a population balance model using the identified parameters with the results of corresponding validation experiments.

A Short-Cut Method for the Quantification of Crystallization Kinetics. 1. Method Development

“…Change of the particle number (N(t)) of the CSD due to nucleation (B 0 ) [7]. Solid lines: Initial state; Dashed lines: Evolution of the state.…”

“…Parameters corresponding closely to the well-studied compound potassium aluminum sulfate dodecahydrate (potassium alum) were selected in the present study. The solubility curve measured in own preliminary experiments [7] was expressed using a 4 th order polynomial (eq. 14, Fig.…”

“…Several authors investigated the crystallization kinetics of potassium alum over the past decades either with empirical approaches [11,16] or based on thermodynamics [17]. In this article, kinetic equations and parameters are applied related to results of the mentioned own preliminary experimentally studies applying the short-cut-method analyzed here in more detail [7]. The parameter of the assumed power law sub-models (eq.…”

“…The initial mass of the crystal phase was adjusted in the simulations to 0.57 g Seed /kg Solvent (5% of the expected product mass on average). Based on the available knowledge regarding the specific system [7], this ensures a good observability of the growth process while the initial crystal surface area is not strongly limiting the attainable supersaturation. Except for the initial temperatures all assumed parameters, which are summarized in table 3, were kept constant during all experiments.…”

“…The results shown in figure 3 reveal, that all three sets of process parameters were well selected to cover reasonable ranges super-and undersaturation during the cooling and heating ramps, respectively. This selection was guided by the available a priori knowledge about the system considered [7]. Nevertheless, if first estimates of the crystallization kinetics exist, efficient tools [18,19,20] can be utilized to improve the selection of process parameters and to enhance the accuracy of the subsequent parameter optimization by setting convenient experimental conditions.…”