GB187260A - Improvements in or relating to methods of and apparatus for heating or cooling liquids or admixed solids and liquids in evaporative and like treatment thereof - Google Patents

Abstract

187,260. Rigby, T. May 10, 1921. Drawings to Specification. Multiple-effect apparatus; vapours, utilizing for effecting further evaporation; crystallizing. -In evaporating liquids in multiple-effect apparatus, particularly of the kind described in Specification 180,963, in which the liquid is fed in parallel to the effects, the liquid is passed in series through a number of multiple-effect plants, the temperature ranges of which coincide or overlap substantially. In concentrating brine or other liquid the boiling-point of which rises on evaporation, the first effects of each plant are preferably supplied with steam from the same source and the last effects are connected to the same condenser, and the number of effects in each succeeding plant is progressively diminished. In evaporating cane or beet sugar solutions, the concentration obtained in the last plant may be such that crystals separate in the effects of this plant, or crystallization may be effected outside the plant in crystallizing vessels which may be supported on wheeled devices or in heated pans in which slow evaporation takes place. When the concentrated liquid is to be cooled to cause crystallization or for other purposes, the vessel containing the liquid is connected to the vapour spaces of effects at progressively lower pressures as to cause the liquid to flash off steam and to lower the temperature in stages. The method of cooling the concentrate and recovering the heat for use in the evaporating process may be used in plant in which the multiple-effect apparatus is replaced by apparatus of the kind described in Specification 12462/11, in which the vapours evolved on evaporation are compressed and used as the heating-agent. In concentrating impure liquids such as seawater, which at one stage of the concentration will deposit impurities, such as calcium sulphate &c., on cooling, the cooling may be effected by flashing-off vapours from the solution by connection with effects of lower pressure, during the passage of the solution from one evaporating plant to the next. The solution may be preheated before passage into the next plant by heat-exchange with the solution from the first plant. According to one Provisional Specification, the control device described in Specification 180,963 for controlling the passage of vapour from one effect to another may be used also to control the inflow of liquid into the effect.