Analysis of the Dynamics of Particles in a Precipitation Chamber by SAS Technique with Coaxial Injection System Using a One-Way Coupling Euler-Lagrange Approach

Abstract

Precipitation processes such as SAS - Supercritical Antisolvent - based on supercritical fluids have been extensively used in the crystallization of a wide variety of materials in a controlled manner allowing one to obtain nanoscale particles which are almost spherical in shape. The understanding of the dynamics of the particles inside the precipitation chamber allows the decision for operating conditions that are favorable to the precipitation of particles of small size, but there is still a great experimental challenge. In this paper, a Euler- Lagrange approach with one-way coupling was proposed to evaluate the dynamics of particles in a chamber of SAS precipitation prescribing one distribution of particle diameters, assuming values within ranges specified from experimental values. From the software ANSYS CFX used to obtain the solution of the mathematical model, the following variables were analyzed: mixture velocity, the time of trajectory, the dead zones and the average diameter of the precipitated particles. Under an operating pressure of 120 bar and an operating temperature of 313 K, the results showed that the flow pattern is quite complex. There is high speed of mixture at the outlet of the capillary injection. In this region were also observed large changes in the mixture density and large variations in the composition of the mixture.Were observed large particle diameters around the chamber outlet pipe, which suggests that a change in the outlet position of the camera can improve the process yield. The model proved to be a quick and economically versatile tool for a better understanding of the dynamics of particles and, consequently, to select conditions that can give a better control over the performance of the SAS process.