The effect of the impeller speed on the product crystal size distribution (CSD) a 22 liter draft tube (DT) crystallizer

In draft tube (DT) crystallizers secondary nuclei originate predominantly f rom collisions between crystals and the impeller. The formation step of the se nuclei is a complex process depending on the attrition behavior of the c rystalline material and the two-phase flow pattern in the vicinity of the i mpeller. In order to develop crystallizer models with a predictive value fo r different operational conditions or for different scales of operation a m echanistic description of the secondary nucleation rate is a prerequisite. In this paper the predictive capability of a mechanistic model framework wa s studied by comparing the dynamic trend of the predicted median crystal si ze L-50 with the experimentally obtained one. The model is in good agreemen t with the experimental data regarding the predicted steady-state L-50 and the amplitude of the start-up oscillation. The dynamic behavior predicted b y the model, however, differs from the measured one regarding the oscillati on frequency and phase for reasons that will be addressed in the future. (C ) 1999 Elsevier Science B.V. All rights reserved.