Framework for the analysis of crystallization operations

Crystallization is often applied in the production of salts and/oractive pharmaceutical ingredients (API), and the crystallization step is an essential part of the manufacturing process for many chemicals-based products.In recent years the monitoring and analysis of crystallization operations has received increased attention due to the growing need to control more sophisticated production lines as well asto measure/monitor the final product characteristics.
Crystallization operations involve a combination of several phenomena, and different kinetic models are required for their modeling. Growth of the crystals occurs in multiple dimensions and the relative rates of different growth and other kinetic phenomena control the shape and size distribution of the final product. Including several dimensions in the crystallization will allow a more general description of the kinetic phenomena and thecrystallization operation. In order to have a full description of a crystallizer a combination of constitutive (kinetic) models is needed. Development of appropriate constitutive models requires data, which for size distributions in crystallization operations is available in the form of chord length distribution data (from Focused Beam Reflectance Measurements (FBRM)). Use of this data for modeling requires a data translation procedure.
The objective of this paper is to present a modeling procedure for systematic development of constitutive models for use in design, analysis and simulation of crystallization operations. This procedure has three main features:A data handling and translation feature, a constitutive model identification feature and a model application feature.For different crystallization operation scenarios, the measured data is translated to create an image of the product. Through the model identification option, the parameters of the constitutive models embedded within the crystallizer model are regressed to match the translated product image. With the models identified, they are applied to understand, design and/or analyze various crystallization operational scenarios.
The paper will present the constitutive model development procedure as part of a general crystallization modeling framework. It will highlight the different features through a case study involving measured data and use it to develop models and finally, the use of the model to analyze different crystallization operations.