Numerical Modeling Of Mass Transfer And Experimental Investigation Of The Supercritical Antisolvent Process

The supercritical antisolvent (SAS) process has been proposed recently as a new method of micro-particle formation, which can be applied in chemical engineering, bioengineering, medical treatment and pharmacy etc. Because of the lack of the theoretical investigation and the limitation of the experiments, a complete understanding of the SAS process has not got, and the common conclusions how the important process parameters effect on particle characteristics can't be drown. The mass transfer behavior of the droplets is thought to be a key factor effecting on the particle morphology. The study of mass transfer of the droplets is helpful to find out the effect of the operation conditions on particle characteristics, and give an approach of the choice for the operation conditions for the SAS process.A mathematical model of mass transfer between an organic solvent droplet and its antisolvent environment is presented. Through the numerical modeling of mass transfer at the different conditions, the evolution of the droplet in the whole process is analyzed. According to the results of mass transfer modeling for acetone-CO2, ethanol-CO2, and toluene-CO2, the droplet swelling occurs when the solvent is denser than antisolvent, while shrinking occurs at very high pressures for which the antisolvent is the denser component. Furthermore, mass transfer is faster when the solvent and antisolvent are miscible (at the mixture supercritical conditions), as compared to the subcritical conditions for which two phases exist. The results suggest that the solvent-antisolvent critical locus and equal-density locus can be useful guides for selecting SAS operating conditions.The SAS process experiment is used to produce micro-particles of quercetin. The effects of the SAS process parameters on particle morphology are studied. The numerical modeling of mass transfer of the droplets for these processes is given, and the evolutions of the droplet lifetime at different conditions are discussed. The model result is in agreement with the experimental data. So the best operation conditions for the SAS process can be choosen by the modeling of mass transfer.