GB1350766A - Water desalination device - Google Patents

Abstract

1350766 Evaporators, flash type; desalination of water DEFENCE SECRETARY OF STATE FOR 19 April 1971 [12 March 1970] 11813/70 Heading B1B Irrigation water is obtained from brine or well water by passing it through a series of adjoining flash chambers 11 each comprising an evaporator tray, a condenser and a condensate tray, the chambers being arranged so that they are vertically staggered in helical array; and the preheated feedwater flows upwards through the evaporator trays from the lowest chamber. The apparatus shown comprises a hexagonal shell 10 of reinforced concrete which contains eighteen trapezoidal chambers 11 accommodated in three turns of a helix. Two-thirds of the shell 10 is below the ground. The top chamber is connected to a vacuum pump. The side walls of each chamber are common to the adjoining chambers, while the evaporator tray form the bottom of one chamber and the top of the chamber vertically below (where there is such a chamber). The trays are connected by reverse siphon devices each comprising holes in the side walls and a duct wall. The condensate tray divides the chamber into a minor upper portion and a major lower portion, and is provided with apertures and bubble-caps. A bundle of finned condenser tubes passes through the upper space of each chamber. The vapours evolved from the water in the evaporator tray pass through the bubble caps of the condenser trays and flow to the condenser tubes from which the condensate drips into the condenser tray. In the central tube 12 of the apparatus there is mounted a gas turbine 14 which drives an electrical generator 13. Air for the turbine is supplied through intake filter 18. The hot gases exhausted from the turbine flow to thermal transformer 15 which comprises a pair of interconnected heat exchangers wherein heat is transferred from the hot gases to the feedwater by means of a circulating mixture of diphenyl and diphenyl oxide which is vaporized in one heat exchanger and condensed in the other. Before discharge from the system, the exhaust gases are passed in heat exchange with the liquid in the lowest evaporator tray. The feedwater is preheated in heat exchanger 20 and then flows into tank 19 where it is mixed with some of the brine leaving the highest flash chamber; the mixture (if desired, after treatment by electro-dialysis) is passed through the condenser tubes and the thermal transformer 15, and the hot mixture is then introduced into the evaporator tray of the lowest chamber 11. Condensate (purified water) flows up through the condenser trays, and is withdrawn from the system through coil 22. Brine is discharged from the system through coil 21.