GB1361345A - Distillation of liquids - Google Patents

Abstract

1361345 Flash evaporators; ;desalination of water J VAN OORD 16 Feb 1972 [17 Feb 1971] 7170/72 Heading BIB Seawater (or other liquid to be purified) is drawn up from annular tank 16 through conduit 20 into chamber 48 where reduced pressure is maintained so that evaporation of water takes place and the temperature of the residual brine is reduced. The vapour is drawn by fans 60 and 62 into upper section 64 of condenser assembly 22, wherein the vapour passes down in countercurrent heat exchange with the cool brine which is flowing through tubes 66. The condensate and residual vapour pass into zone 72 which is supplied with fresh water through spray head 74. Gases are withdrawn from the condenser through tube 30 by means of pump 28. The condensate, i.e. desalinated water, flows down to tank 24 through conduit 84 wherein further heat exchange takes place with the brine flowing through tubes 90. The brine is withdrawn from manifold 92 by pump 43: a portion may be discharged through valve 44 and the remainder is conducted first to tank 18 through valve 46 and then to tank 16. Chambers 48 and 58 are insulated from solar energy by pumping water from conduit 20 via conduit 96 through the double-walled roof 98; the warmed water then enters chamber 48 through apertures 108. In cold weather conditions, the arrangement is modified so that the water cooled in the insulating space is discarded from the system without injection into chamber 48. The operation of pump 26 and the height of the condensate in conduit 84 are regulated by a controller (Fig. 4, not shown), which is also connected to a component for controlling the speed of fans 60 and 62. Circulating pump 43 and temperature sensors 122 and 124 maintain a preset differential between the temperature of the feed liquid and the concentrate respectively. The liquid-level 38 in chamber 48 is also maintained constant by automatic means. A modified apparatus is described wherein the vapour is condensed by heat exchange with a coolant from an external source, and the seawater is preheated in a heat exchanger forming part of a refrigeration system (Fig. 5, not shown). Several units may be interconnected with respect to successive treatment of either the condensate or the concentrate. In such an arrangement, the spent feed of one unit could be used as coolant for the condenser of the following unit.