GB1021830A - Improvements relating to the heat treatment of liquids with steam - Google Patents

Abstract

1,021,830. Indicating specific gravity. ALPURA A. G. April 23, 1963 [April 25, 1962], No. 16048/63. Heading G1S. [Also in Division A2] In a method for the pasteurisation or sterilisation of milk, fruit juices and liquid pharmaceutical products, involving passing the liquid through first and second preheating stages, bringing the liquid directly together with steam to heat the liquid, cooling the liquid by reducing its pressure and passing at least some of the waste vapour evolved by the liquid during pressure reduction to the first preheating stage to heat the incoming liquid, the rate at which waste vapour is passed to the first preheating stage is continuously controlled to produce a desired preheat temperature of the liquid, and heating medium is supplied from an independent source to the second preheater at a rate and temperature which are constant for long periods of time. It is stated that deviations in the preheat temperature are thus controlled out very rapidly because variations in the rate at which waste vapour is passed to the first preheating stage act upon the expansion pressure to which the liquid is reduced during cooling in such a way as to promote the required correction. Milk is passed through a first preheater 3, a second preheater 5 and, having attained a temperature t 3 , passes through a steam-injector 7 wherein the milk is heated to a temperature t 4 of 150‹C; the injector incorporates a measuring unit 9, a controlling unit 10 and a regulating valve 11 so that the heating temperature t 4 is maintained constant. The milk is cooled immediately in an expansion chamber 12 kept under reduced pressure by an injector condenser 17 to a temperature t 5 and leaves the apparatus through a pipe 15. The waste vapours evolved by the liquid during the pressure reduction are supplied through a pipe 18 to the preheater 3 of the first preheating stage; the preheater 5 is independently heated by steam or hot water. The preheat temperature t 3 is controlled by a unit 28 which delivers a signal through line 29 for opening or closing a valve 36 in the pipe 18. The desired value of t 3 may be adjusted by a unit 32 in accordance with a previously calculated pattern in dependence upon variations in the expansion temperature t 5 . In the case of milk, it is preferred that the final specific weight equal the initial specific weight. The valve arrangement 41, 43, Fig. 2, may replace the single valve 36 of Fig. 1.