GB691789A - Improvements in or relating to stills - Google Patents

Abstract

<PICT:0691789/III/1> Double-effect distillation, particularly of sea water in portable stills, is effected using a burner to heat the first effect, i.e. the higher pressure effect, and allowing distilland to flow continuously through the boiler of the first effect while the second effect is intermittently charged with disstilland and emptied of distillation residues. The first effect is preferably operated at atmospheric pressure and the second under reduced pressure produced by a hand pump. In the portable apparatus for distilling sea-water shown in the Figure the first-effect comprises copper-boiler 1, burner 6, steam outlet-pipe 12, and constant-level brine off-take 3; and the second-effect comprises evaporator 14, steam outlet-pipe 23, condenser 24, receiver 26, and discharge-valve 29. Coil 13 is common to both effects, for it is the condenser of the first-effect and the heater of the second. Distilled water from both effects is collected in vessel 27. A pipe 34 drains the brine from evaporator 14 to steam-trap 10 via valve 35 and pipes 36, 9. Valve 35 has a double-bore; and it admits air via pipe 39 to the top of the evaporator while the latter is being drained. When it is desired to operate the apparatus, water is charged to boiler 1 and feed-tank 25, burner 6 is ignited, valves 29 and 35 are closed, and the pressure in the second-effect is slightly reduced by hand-pump 40. When the water in boiler 1 has begun to boil, valves 33 and 31 are opened, and water is thereby supplied to boiler 1 and evaporator 14. Valve 31 is closed when the water in evaporator 14 reaches a suitable level, as indicated by gauge 20. The supply to the boiler, which passes through heater 17, pipe 18 and auxiliary tanks 8 and 7 before entering the boiler through tube 7a, is adjusted so that the water in the boiler overflows at a slow rate via off-take 3, pipe 9 and steamtrap 10. Excessive deposition of salt in the boiler is thereby avoided. When the brine-level is evaporator 14 has become low, valves 29 and 35 are opened. The brine is thereby discharged from the evaporator; and the distilled water collected in receiver 26 flows into vessel 27 which already contains the distilled-water obtained from boiler 1. Valves 29 and 35 are then closed, the pressure in the second-effect is again reduced by pump 40, and the evaporator is recharged by opening and closing valve 31. In the meantime the first-effect can operate continuously. Specification 691,791, [Group XII], is referred to.