GB780272A - Method and device for distilling aqueous salt solutions to obtain potash water - Google Patents

Abstract

Pure water is obtained from sea water and other aqueous salt solutions by bringing a spray or jet of the preheated aqueous solution into contact with a hot gas such as air, under subatmospheric pressure, whereby partial evaporation of the water takes place, compressing and independently heating at least part of the mixture of water-vapour and gas so obtained and then passing the hot compressed mixture in heat-exchange relationship with fresh solution and gas whereby the solution and the gas are heated while the water-vapour condenses from the mixture to yield pure water. In the apparatus shown, the aqueous solutionis pumped in through conduit 23a; and air is sucked into manifold 20 by blower 22. The aqueous solution flows up through radiator 13 which forms the <PICT:0780272/III/1> inner path of triple-path heat-exchanger 12, which surrounds cylindrical evaporating chamber 1. The air rises through the outer annular path 17 of the heat-exchanger, while hot compressed water-vapour/air mixture (see later) flows down in the intermediate path between the two up-flow paths. The solution, now at a temperature between 85 DEG and 212 DEG F., passes through duct 3 which delivers it as a jet into chamber 1. The preheated air, which has a temperature between 100 DEG and 250 DEG F., is introduced into the lower part of the chamber through duct 4. Partial evaporation of the downflowing solution takes place as it falls through the upflowing air. Part of the mixture of water-vapour and air is drawn from the chamber through stack 6a into rotary compressor 7a; and the compressed mixture discharged therefrom is heated by gas burners 8. The remainder of the moist air in chamber 1 is withdrawn through stacks 7, and mixes with the hot compressed portion in the throats of convergent-divergent systems 8a. All the moist air, which is now hot and compressed, is collected in duct 10 and then delivered by ducts 11 to the heat-exchanger. The pure water condensed in the heat-exchanger collects in annular chamber 31, from which air escapes as shown by arrows 29. Non-evaporated solution is discharged from the apparatus via valve 33. Another embodiment is described wherein the water-vapour/air mixture may be heated by solar energy, the cooling of the mixture is effected in two separate heat-exchangers, and a third heat-exchanger is provided wherein the solution to be treated is preheated by the concentrated solution leaving the apparatus. Specification 760,517 is referred to.