Process and apparatus for double-distillation

摘要

In a process for the double-distillation of liquid, particularly water, the primary vapours are wholly or partly condensed by heat-exchange with the primary condensate which for this purpose is in a space, maintained under sub-atmospheric pressure, connected to the primary condensate collecting-reservoir by a throttling-device. The primary condensate is thereby vaporized, and the secondary vapours so formed are condensed to final product, preferably by heat-exchange with the feed liquid. Any vapours not condensed in the primary condensation stage may also be condensed in the condenser / preheater, the condensate being refluxed back to the primary condensate. Live steam, generated in evaporator 20 which contains electrodes 22, 23 flows through elbow-tube 25 to the tubular spiral 7 of heat-exchanger 1, and primary condensate collects in reservoir 2 while uncondensed steam passes to reflux tube 9 of condenser 5. Primary condensate flows through adjustable cock 3 into the outer space 8 of the heat exchanger which is maintained under sub-atmospheric pressure by a vacuum pump connected to nipple 19. Excess primary condensate flows out of reservoir 2 through siphon-tube 11. Primary condensate is re-evaporated in outer space 8; and the steam ascends through entrainment separator 4, the lower part of which contains Raschig rings and baffles 13, and then flows down pipe 15 to the tubular spiral 16 of condenser 5, from which final condensate flows to a receiver through discharge 17. A water-jet pump may be used as vacuum pump; and the water which has passed through the pump may be used as feed water for evaporator 20, after being preheated in condenser 5. The water level in evaporator 20 changes under control of regulator 21, which is supplied with feed water through inlet 40, in order to maintain substantially constant the pressure of the steam delivered to spiral 7. The apparatus is made of glass, quartz, silver or of silverplated or tinned copper. The production of "conductivity water" is referred to.