Abstract: The invention relates to a spray freeze dryer apparatus and method of using same for use in drying or concentrating a raw material which at ambient conditions has a solid and an aqueous portion. The dryer includes a chamber and a chamber pressure reduction device; an inlet nozzle or nozzles through which the raw material is injected into the chamber; and a collection surface or surfaces which collect a frozen portion of the raw material. The chamber is kept at a pressure below the triple-point pressure of the aqueous portion of the raw material. Several additional features are described to control the thickness of the layer on the collection surface.