GB726452A - Heat treatment of liquids - Google Patents

Abstract

726,452. Heat treating liquids. ALPURA AKT.-GES. April 1, 1953 [April 5, 1952], No. 9096/53. Class 49. In heat treating beverages such as milk and fruit juice, e.g. for sterilizing, by the method involving preheating of the liquid by heat exchange from a heating medium, further heating under pressure by introducing steam which at least partly condenses in the liquid, and immediately cooling by subjection to a pressure drop whereby some of the water flashes off in the form of vapour, the final expansion pressure is maintained at constant value and the amount of heat given up by the heating medium is so adjusted so as to determine the amount of water which remains in the treated liquid and thus control its specific gravity. With the apparatus of Figs. 1 and 2, milk is supplied by a pipe 2, is heated in a preheater 3a by heat transfer from vapour and is partially deodourized by spraying into a vacuum vessel 5, the vapour being drawn from the vessel 5 into a spray condenser chamber 25 in which is a droplet separator 27 by the agency of a pump 30 which evacuates the chamber 25 and the vessel 5, and the milk being allowed to flow from the vessel 5 to a collecting tank 9 ; from the tank 9 the milk is pumped along a pipe 10 by means of a pressure pump 13, is heated in a preheater 3b, to a temperature below the atmospheric boiling point, by heat transfer from vapour, is passed by a pipe 11 into a device 12 and there heated by steam injection in a fraction of a second to a temperature above 140‹C., and is passed by a pipe 17 into a vacuum chamber 18 for cooling, the milk so treated being discharged from the chamber 18 by way of a pipe 21 and the vapour produced in the chamber 18 being drawn off into a droplet separator chamber 41 and through a pipe 22, past a throttle 33 therein, to the vapour chambers of the preheater 3a and 3b. In the apparatus of Fig. 1, there is, between that portion of the pipe 22 before the throttle 33 and the condenser chamber 25, a pipe 34 in which is a valve 35 operated by a servo mechanism in response to a pressure-sensitive element 36 in the pipe 22 ; the valve 35 opens or closes according to whether there is a rise or fall in pressure in the pipe 22 and the pressure in the chamber 18 is thus kept constant. Also in the apparatus of Fig. 1, there is, in the pipe 11 where it emerges from the preheater 3b, a temperature-sensitive element 38 which influences a servo-controlled valve 40 in a pipe 28 from the vapour chambers of the preheaters 3a and 3b to the chamber 25 to open or close the valve 40 upon rise or fall in the temperature of the milk flowing in the pipe 11, initiate a fall or rise in pressure in the vapour chambers of the preheaters 3a and 3b and thus decrease or increase the temperature of preheating. In the apparatus of Fig. 2, a specific gravity meter 45 in the milk discharge pipe 21 replaces the temperature-sensitive element 38 in influencing the valve 40, closing or opening movement of the valve 40, increase or decrease in preheating temperature and consequent reduction or increase in the water content of the treated milk occurring upon rise or.fall in the specific gravity of the treated milk above or below the desired value.