GB1170872A - Freeze drying system - Google Patents

Abstract

1,170,872. Freeze drying systems. M. L. BREWSTER. 8 March, 1968 [9 March, 1967], No. 11338/68. Heading F4G. A freeze drying system comprises a main room 11 for preparing the wet product to be dried, a freezer 12 for freezing the wet product received from the main room 11, a vacuum drying chamber 14 having aligned inlet and outlet doors 34, 36 at opposite ends thereof, for receiving frozen material from the main room 11 and a dry room 16 of inert atmosphere for handling and packaging of the freeze dried material received from chamber 14. The material in trays may be conveyed through the system on carriers which are moved along an overhead and floor rail system comprising movable and stationary rails. Nitrogen may be continually circulated through the room 16 and air from supply means 72 is supplied to the helmets and suits of the persons working in room 16. The vacuum drying chamber 14 may comprise a longitudinal centre chamber housing the trays between heated plates which may be mounted on cars, and side chambers 116 housing condenser plates 118. The plates 108 separating the chambers may be coated on their inside surfaces with a white epoxy resin paint. The chambers are in communication when valves 110 are open and are connected to a vacuum source by conduits 134. The side chambers may be alternatively sealed off from the centre chamber to allow the condenser plates to be defrosted without interrupting the freeze drying process. Both side chambers may be sealed off to determined whether drying has been completed, which is the case when a pressure sensor indicates no rise in the vapour pressure of the centre chamber. When the drying has been completed the centre chamber is filled with nitrogen to break the vacuum and to saturate the freeze dried material which is subsequently conveyed to room 16. The packaged freeze dried material is conveyed from room 16 to room 11 via air lock 20.