GB1030000A - Improvements relating to the recovery of volatile substances in freeze drying processes - Google Patents

Abstract

1,030,000. Freeze drying. LEYBOLDHOCHVAKUUM - ANLAGEN G.m.b.H. June 7, 1963 [June 7, 1962], No. 22746/63. Heading F4G. [Also in Division B1] Volatile substances which together with moisture are driven out of material undergoing a vacuum drying process are contacted and retained in or by at least one cooled liquid and thereafter recovered from the liquid. The volatile substances may be retained by condensation and/or absorption or adsorption and/or chemical reaction. In Fig. 1, a freezedrying chamber 1 has a heated supporting surface 11 on which is the material 12 to be dried. This chamber communicates with condenser 2 having heat exchanger 22 cooled by refrigerating machine 21 which machine also cools a liquid, e.g. silicone oil, at 4 which subsequently enters the condenser 2 at nozzle 31. The liquid then runs down exchanger 22, and out through valve 34 into vessel 33 which may conveniently be a centrifuge to remove ice from the liquid phase. Pump 32 then recirculates the liquid whilst through valve 51 at least a part of the liquid can be withdrawn into pipe system 52 and passed to heat exchanger 6 where the volatile substances are removed from the liquid, condensed at 7 and subsequently discharged through valve 74 to collecting vessel 75. The liquid thus regenerated is returned to pipe 3 by pump 62. Vacuum pumps 81 and 82 are associated with freeze drying plant and the regeneration plant respectively. In an alternative embodiment (Fig. 2, not shown), the heat exchanger 22 may be dispensed with if the cooled liquid entering at 31 offers sufficient condensing area without needing to be further cooled. In another embodiment (Fig. 2, not shown), the condenser 2 is preceded by a condenser wherein water vapour is condensed on to a heat exchanger and subsequently discharged after thawing. A third condenser stage is added after condenser 2 which is similar in construction to the second condenser stage but acts as a hydrolyser for the volatile substances, e.g. ethereal oils, by circulating an alkaline solution, e.g. KOH with subsequent recovering of the reaction product and introduction of fresh caustic solution in a separating and refilling device. Oils and organic solvents which have a high vapour pressure at room temperature may also be used. Different non- aqueous volatile substances may be removed by different kinds of physico-chemical absorbers. The cooled liquid may also act as a vehicle for the transportation of ion exchanges and other adsorbents, e.g. active C.