Evaluation of changes in physicochemical properties in a supercritical antisolvent (SAS) process using 3D turbulent CFD approach

Abstract The precipitation of particles under supercritical conditions is applied to a wide variety of compounds in the pharmaceutical and food industries. The influence of the temperature and pressure dynamics of the flow which is developed in such processes has not been satisfactorily studied. All physical properties can be strongly influenced by these parameters, and the quantification of changes and their impact on the process yield have rarely been studied using a CFD tools. Therefore, a thermodynamic model was proposed considering supercritical conditions of flow coupled to a fluid dynamic model for carbon dioxide and dichloromethane mixing in order to predict the thermodynamic properties and their influence on particle precipitation. These calculations include the density, thermal conductivity, viscosity and diffusivity, determined through Peng–Robinson's EOS, the quadratic mixing rule of Van der Waals and the Riazi & Whitson and Chung methods, respectively. The simulations were performed using a commercial CFD code for pressures between 80 and 160 bar and temperatures between 308.15 and 318.15 K. Due to the mixture being near the critical point, small changes in temperature and pressure lead to important variations in the thermodynamic properties, directly influencing the dynamic mixing process which is related to the size, size distribution and morphology of the particles.