New generation of industrial crystallizers Numerical simulation of a bubble growth induced by laser

Abstract

Production of crystals of different chemicals with the desired properties is a not trivial task and great number of studies have been carried out in order to understand the crystallization kinetics. Notwithstanding all these efforts, further investigation is needed to understand the underlying physics and the sequence of events that leads to crystallization. Moreover, introduction of novel technologies that facilitate the crystallization process and, as a result, produces crystals with the desired and controlled quality are essential. In this thesis, several technologies such as the laser-induced crystallization, ultrasound-induced crystallization, air-lift crystallization, oscillatory baffled crystallization and the high-gravity crystallizer have been studied and their main features are presented. In particular, the study focuses on the laser-induced crystallization or, more specifically, on the growth of a bubble that is induced by laser irradiation in an aqueous solution of ammonium sulfate. The numerical part of study is based on the volume of fluid (VOF) framework and the Schnerr and Sauer cavitation model (G.H.Schnerr, A.J.Sauer, F.I.C.M.F, 2001) to model the bubble growth. The simulations consider mass and energy transfer during the phase change in a stagnant ammonium solution. The simulation results show that the mass fraction of ammonium sulfate increases as a result of evaporation of solvent from liquid into the bubble. The increase of solute concentration during the expansion of a bubble is recognized as a driving force for nucleation. In the same time, it also increases the probability of formation of stable clusters.. The predicted values for the bubble radius as a function of flow time are found to be lower than the experimental data and the maximum predicted bubble radius is higher than the maximum bubble size in another sudy (A. Soare et.al, Cryst. Growth Des, 2011).