GB956224A - Method of, and apparatus for, controlling the specific gravity of a heat-treated liquid - Google Patents

Abstract

956,224. Sterilising liquids. ALPURA A.G. Dec. 21, 1962 [Jan. 4, 1962], No. 48309/62. Heading A2D. [Also in Division G1] The end specific gravity of a liquid is controlled in relation to its initial specific gravity in a plant in which the liquid is heated by direct contact with steam and then cooled by expansion with partial evaporation, by varying the difference between the expansion temperature and the initial temperature of the liquid before heating in dependence on variations in at least one of these two temperatures. The sterilisation or pasteurisation of milk, fruit juices and pharmaceutical products are instanced. According to an example, milk pre-heated to a temperature t3 by passage through pre-heater units 3 and 5, Fig. 1, is sterilised by shorttime heating to a temperature t4 of 150‹C. by steam injected from a line 8 at a temperature of 175‹C. and a pressure of 9 Kg. per sq. cm.; the regulation of the steam valve 11 by a temperature-sensitive element 9 ensures that the heating temperature t4 is kept constant. The heated milk is colled rapidly in an expansion chamber 12, held under vacuum by a condenser 17, to an expansion temperature t5 of about 80‹C. and the cooled milk is drawn off along a line 14. A comparator unit 30 and modifying unit 32 regulate the valve 25 supplying heating medium to the pre-heater 5 in accordince with a graph, Fig. 4 (not shown), depicting the requisite variations in temperature difference t5-t3 for a range of expansion temperatures t5 under the operational conditions whereby the specific gravity of the treated milk is kept at the same value as that of the raw milk introduced into the plant. In the regulating system shown in Fig. 2, the measurement of temperatures t3, t5, by elements 41, 42, which are filled with a vapourisable liquid and produce inside bellows capsules 44, 43 pressures corresponding to the temperatures sensed, is transmitted through a calibrated threedimensionable cam 51, Figs. 2 and 3, to the stem 52 of the valve 25. A change in the temperature difference t5-t3 causes the cam to rotate about its shaft 50, while variation in the expansion temperature t5 produces an axial displacement of the cam. In alternative embodiments (i) the temperature difference t5-t3 may be calibrated against the initial temperature t3, (ii) to keep constant a desired end value for the specific gravity, the temperature difference between the initial temperature t3 and the expansion temperature t5 may be adjusted according to variations in both these temperatures, Figs. 6 and 7 (not shown), and (iii) the temperature may be regulated and adjusted by varying the expansion pressure and hence the expansion temperature, Fig. 5 (not shown).