A new process for extractive separation with supercritical fluids is described It is characterized by mixing a liquid feed with a dense gas in a special mixing device and the formation of spray particles when this mixture is injected into an extraction zone where the fluid phase is loaded with the extracts. By dividing the extraction into two process steps, mixing and loading, it is possible to adjust the devices and apparatuses for different media. For example, a static mixer or a fluid-assist atomizer can be used as mixing devices. Since the viscosity behavior of the mixture and the suflace tension in dense gases are important for the formation of spray particles, carbon dioxide was measured at pressures up to 70 MPa and the geometry of the extraction zone was optimized by residence times and fluid dynamics.
Two different materials were tested in an apparatus on a semiindustrial scale with different mixing deuices and extraction zones. By measuring fluid loading in the extraction zone, the mass-transfer parameter of a mathematical extraction model could be adapted. The model considers particle formation in the mixing zone, the fluid dynamic in the loading zone, and the mass transfer between spray particles and fluid phase. Calculated concentration profiles make it possible to determine the residence time and the size of the extraction zone for given geometries and fluid dynamics.