GB669928A - Improvements in and relating to compression distillation plant - Google Patents

Abstract

<PICT:0669928/III/1> In distilling water using an evaporator of the vapour-compression type, the water is preheated to precipitate a considerable proportion of the scale-forming constituents, by contacting it with superheated steam, the steam being derived by submitting the condensate from the heating-coil of the evaporator to partial flash-vaporization; and the precipitated scale-forming constituents are separated from the heated water before it is introduced into the evaporator. The flashed steam is preferably superheated by use of the waste heat of an I.C. engine, or a gas turbine, or a steam power-plant. Sea-water is introduced through spray 3 into preheater 4 which is supplied with superheated steam through nozzles 5; and the precipitated sludge is blown-down by pump 7. The hot brine from preheater 4 is passed through pipe 8 to evaporator 9, from which concentrated brine is withdrawn through pipe 13. Steam is withdrawn from the top of the evaporator, compressed in axial-flow turbo-compressor 10, and passed through coil 11 which is immersed in the brine. The greater part of the condensate formed inside coil 11 is passed through throttle-valve 15 into separator 16 where some of the condensate flashes into steam. The water which collects in the bottom of the separator, is drawn-off by pump 18 to the distilled-water storage tank. The steam withdrawn from the separator through pipe 19, is compressed in compressor 20; and is then superheated in superheater 21 by heat-exchange with exhaust gases or vapours (flowing through duct 22) from an I.C. engine or gas turbine. That part of the condensate from coil 11 which is not introduced into the separator, is passed through by-pass 23, and is vaporized in heat-exchanger 25 which is heated by the exhaust gases leaving superheater 21; and the steam so formed then passes to superheater 21 where it mixes with that from separator 16. The superheated steam withdrawn from the superheater, is introduced through nozzles 5 into preheater 4. When operating in conjunction with steam powerplant, compressor 20 and superheater 21 may be replaced by a steam-ejector; the by-pass 23 and heat-exchanger 25 are then dispensed with.