EXPERIMENTAL DESIGN OF CRYSTALLIZATION PROCESSES USING TAGUCHI METHOD

Miran Hvalec, Andreja Goršek, and Peter Glavič

Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova 17, Maribor, Slovenia

Abstract

Crystallization has become one of the most important unit operation in the chemical industries. The need to reduce the time from product discovery to market introduction is an inherent concern. In order to achieve the prescribed product quality characteristics, the process of engineering experimentation has to be optimized. Therefore, an experimental design method for crystallization processes is presented in this paper. Initially, the standardized Taguchi method was used to plan a minimum number of experiments. After identifying the working levels of the design factors and the main performance characteristics of the product under study, the method can be successfully applied to the crystallization processes. The simultaneous variations of the main crystallization parameters and their interactions were investigated using orthogonal array technique. A statistical analysis of ‘signal-to-noise’ ratio was followed by performing a variance analysis. After developing some special criteria, which depend on performance objectives, the optimal levels of the design factors were determined.

Crystallization of KNO₃ with desirable particle size as a performance characteristic was used to illustrate the design procedure. The effects of rotational frequency of the stirrer, linear cooling rate and added admixture on final particle size were studied. In order to keep the selected parameters constant during the experiment and to ensure reproduction of entire experiment the automated reaction calorimeter RC1 was used.

Key words: Taguchi method, crystallization, particle size