Process for drying a material from solution

A process for obtaining a solid or semi-solid material by drying a solution thereof, comprising the steps of:

• (a) subjecting the solution to vacuum-assisted freezing by introducing the solution into an evacuated chamber in the form of a uniform spray, the droplets of which are at a sufficiently low temperature to ensure that they freeze at the vacuum pressure inside the chamber;
• and
• (b) collecting the frozen droplets of solution on a collecting surface which is positioned in the chamber such that it collects the frozen solution and which is adapted to retain the droplets until they have been dried by sublimation, and controlling the temperature of the collecting surface and the pressure within the chamber so that the frozen solvent sublimes from the collected and retained frozen droplets, the collecting surface having been prepared by being brought to an initial temperature which is not greater than the melting point of the frozen solution at the initial pressure, which is the pressure within the chamber when the spray is introduced thereto, the temperature of the collecting surface and the pressure within the chamber being maintained throughout the sublimation process so as to prevent partial remelting of the frozen droplets as sublimation occurs.