Lyophilization method and apparatus for producing particles

An apparatus for producing particles comprising:

• a solution source supplying a solution comprising a solvent and a solute;
• a fluid source supplying a compressed fluid, wherein the compressed fluid comprises a first fluid component and a second fluid component that have freezing points at different temperatures relative to each other, and the first fluid component has a higher freezing point relative to the second fluid component, and the first fluid component operates as a blowing or expanding agent and the second fluid component operates as a freezing agent;
• a mixer in fluid communication with the sources for mixing the solution and the compressed fluid together to form a mixture, and for maintaining the mixture at a first pressure sufficiently high so as to maintain the compressed fluid in a compressed state;
• an expansion assembly in fluid communication with the mixer for spraying the mixture across a pressure drop to form mixture droplets, the expansion assembly comprising a nozzle configured so that the solution and fluid are sprayed therethrough, the nozzle being further configured to have a contra-current, co-axial, single or multiple opening configuration, the mixture droplets comprising the solute and frozen solvent;
• and
• a freeze-dry apparatus that is in communication with the expansion assembly for subliming the frozen solvent, and thereby removing the frozen solvent from the solute, whereby solute particles are produced that are generally free of the solvent.