Patent ID: 8734830

Claim:
A method for preparing ultra-fine particles comprising the steps of: (a) continuously contacting a liquid solution containing a solute in a liquid solvent with compressed fluid at temperature of 30 to 90° C., and pressure of 60 to 300 bar, (b) injecting a resultant product into a mixing unit, (c) homogeneously mixing the product to prepare a single-phase mixture; (d) spray-drying the mixture together with heated compressed air having a pressure ranging from 50 to 1000 kPa and a temperature ranging from 30 to 120° C. via a nozzle into an atmospheric pressure evaporation chamber in which drying gas flows, to form the ultra-fine particles; and (e) collecting the formed ultra-fine particles, wherein the nozzle is a device capable of spraying the single-phase mixture comprising the compressed fluid and the liquid solution, together with the heated compressed air, at a spray outflow part, which allows the mixture to contact with the heated compressed air and comprises a multiple-fluid nozzle for two or more fluids, such as a multiple-fluid coaxial nozzle, and wherein the ultra-fine particles have a uniform particle size distribution of an average particle size particle size of 0.02˜3 micron, in which 10 volume % or less of prepared powder has a size of less than 0.02 micron while 90 volume % or more of the prepared powder has a size of less than 3 micron.