Wioletta Podgórska

Mixing-precipitation model with application to double feed semibatch precipitation

Abstract A general mixing-precipitation model describing interactions between mixing of various scales (macro-, meso- and micromixing) coupled with the population balance for crystallization is presented. Macro-, meso- and micromixing were interpreted as a circulation through the zones of different rate of energy dissipation, inertial-convective disintegration of large eddies and an engulfment of fluid from the environment, respectively. The model was verified experimentally for double feed semibatch BaSO 4 precipitation. Experiments were carried out in a Rushton type stirred tank reactor. The effects of feed tube positions, addition feed rate, intensity of mixing, initial reagent concentration and volume ratio on particle size distribution and particle morphology were investigated. The model enables prediction of supersaturation profiles in the system and resulting CSD; the predicted history of supersaturation structure explains the influence of operating conditions on crystal morphology.

Kinetic model of cyclohexane oxidation

A model of the process of the catalytic cyclohexane oxidation in the liquid phase, including both reaction kinetics and mass transfer, is presented. As catalysts cobalt napthenate and chromium napthenate were used. The reaction rate constants as well as the activation energies were determined on the basis of the experimental results obtained in a laboratory reactor. A mathematical model of an industrial reactor for the cyclohexane oxidation is also presented. The results of the cyclohexane oxidation simulations are compared with the data from different industrial reactors (CYCLOPOL process).

Scale-up effects on the drop size distribution of liquid-liquid dispersions in agitated vessels

A multifractal formalism describing the fine-scale structure of turbulence, including its intermittency, is applied to express the drop breakage and coalescence frequencies for drops whose diameter falls within the inertial subrange of turbulence. The model predicts the transient drop size distributions of dispersions in stirred tanks and is used to test four methods of scaling-up agitated vessels. Fast and slow coalescing dispersions are considered.