Study On The Fluid Dynamics Of Supercritical Antisolvent Process

Hydrodynamics property of the fluid is one of the main factors influencingsupercritical antisolvent (SAS) process, which influences the size distribution andmorphology produced by SAS process. The hydrodynamics characteristics of SASprocess are studied with Computational Fluid Dynamics (CFD) in this paper.SAS process includes different processes. In this paper, precipitation by acompressed antisolvent (PCA) process and solution enhanced dispersion bysupercritical fluids (SEDS) are studied. In four models with different nozzle structure,the influences of solvent flux, density of carbon dioxide, size of nozzle and thelength-to-diameter ratio on the hydrodynamics properties of SAS process are studiedby means of the turbulent intensity and volume faction distribution of solvent.The results shows that for all studied SAS process, turbulent intensity increasesin field as solvent flux increasing, and the volume fraction of solvent increases. Andas size of nozzle decreases, turbulent intensity increases. For PCA process, turbulentintensity increases as the density of carbon dioxide decreases. When the density ofcarbon dioxide is close to the density of solvent, the distribution of solvent becomesmore uniform. For SEDS process, turbulent intensity increases as the density ofcarbon dioxide decreases. When the density of carbon dioxide is close to the densityof solvent, the distribution of solvent becomes more uniform. Turbulent intensityincreases as the length-to-diameter ratio increases. The two SEDS processes referringto carbon dioxide and solvent are mixed in nozzle before spraying into vessel, obtainhigh turbulent intensity and homogeneous distribution of solvent. Increasing solventflux properly, the density of carbon dioxide closing to the density of solvent,decreasing size of nozzle, increasing the length-to-diameter ratio are of help to obtainbetter results.For existent equipment, turbulent intensity is very little due to its self structure. Inaddition, PEG-6000 is prepared by PCA process. The comparison between experimentresults and simulation results shows that the results obtained from simulation of flowfield with FLUENT software can give good guideline to the study of SAS process.