GB620573A - Improvements in vacuum dehydration - Google Patents

Abstract

<PICT:0620573/III/1> Substances such as blood plasma or penicillin broth are dehydrated whilst in the frozen state, by exposing them to a pressure of less than 4.7 mm., compressing the evolved water vapour, and condensing it to liquid water in the early stages of the dehydration, and to ice in the later stages. The dehydration is carried out in a chamber 10 which is connected, via a booster pump, to a condenser 60 and roughing pump 70. The booster pump comprises an ejector nozzle 54 and a diffuser tube 32 which is cooled by cooling fluid circulating through the space 34 between the tube and casing 24. This pump is connected by conduits 52 and 56 to boiler 42 which contains a stable organic liquid of low vapour pressure which, when the pump is in operation, is heated by gas-heated tube 46. The substance to be dehydrated is introduced into trays 16, cooling fluid is circulated through condensing coils 62, and roughing pump 70 is started up. When the pressure is of the order of 4.7 mm., the booster pump is put into operation. The organic vapours from boiler 42 are ejected through nozzle 54 and entrain water vapour which has passed into the booster pump from chamber 10 through conduit 20. The organic vapours are condensed on the walls of diffuser tube 32 and the liquid returns to the boiler through conduit 56. The compressed water vapour passes on, and is introduced into condenser 60 through conduit 58. The rate of flow and temperature of the refrigerating fluid in coils 62 is adjusted so that when the amount of water vapour given off in chamber 10 is large, it is condensed to liquid water and collected by funnel 72, but when the amount given off is small, i.e. at the final stage of the dehydration, it is condensed as ice on the coils 62. When a fresh batch of material is to be introduced, valve 22 is closed and, before it is re-opened, chamber 10 is reevacuated by means of roughing pump 82. The water vapour given off in the first stages of dehydration of the new batch melts the ice built up on coils 62 in the final stages of the previous dehydration. Specification 566,814, [Group XXVIII], is referred to.