GB1139810A - Vapour-compression distillation - Google Patents

Abstract

1,139,810. Production of pure water; evaporators of the vapour-compression type. COURTAULDS Ltd. 24 May, 1966 [25 May, 1965], No. 22148/65, Heading B1B. Purified water is obtained from aqueous liquors, e.g. sea water, by causing the liquor to flow as a film over one surface of a thin solid film of plastics material, e.g. of polyethylene, compressing the water-vapour evaporated from the liquor film, and condensing the compressed vapour on the reverse side of the solid plastic film. The heat liberated by condensation of the vapour passes through the solid film and provides the heat required for the vaporization of water from the liquor - film. The vapour compression ratio required is below 1.1. In the apparatus shown, tubes 4 made of polyethylene film are mounted between plates 2 and 3 in a concrete tower 1. The lower header 7 is connected to vacuum pump 11. Sea water, supplied through pipe 15, is preheated in heat exchanger 12 and then flows through pipe 16 to distributor plate 8 in tower 1; the sea water then passes through annular openings in plate 8, an annular opening being provided around the periphery of each tube 4, and flows in film-form down the outer surfaces of the tubes. The vapour evolved from the sea water films is drawn from shell 5 into fan 10, and the compressed vapour is blown, via upper header 6, down the interior of the tubes 4. The condensate, i.e. purified water, collects in the lower header 7, then flows through pipe 19 and heat exchanger 12, and is withdrawn from the system through pipe 17. The concentrated brine leaves the shell 5 through pipe 20; some of this brine is recirculated to distributor plate 8 through pipe 21, and the remainder is withdrawn from the system via heat exchanger 12 and pipe 18. In an example, the thickness of the polyethylene film is 0.005 inches; and there are 1800 tubes 4 each of 50 feet length and 1.25 inches diameter.