GB753144A - Process and apparatus for double-distillation - Google Patents

Abstract

<PICT:0753144/III/1> In a process for the double distillation of liquids, particularly water, wherein the primary vapours are condensed by heat-exchange with the primary condensate which is maintained under sub-atmospheric pressure so that the primary condensate is re-vaporized, the condensate obtained by condensing the secondary vapours is divided into two streams, one being withdrawn from the system as product and the other being passed, via a liquid-level regulating device, to the primary condensate evaporation zone of the heat exchanger in order to prevent the liquid-level therein from falling due to surplus of heat in the heat-exchange exceeding the heat losses from heat exchanger by radiation. Steam is generated in vaporizer 1 which is supplied with water through level-regulator 6, and contains electrodes 5 run from a source of A.C. Deposition silt is drained from the vaporizer by device 7. The steam ascends over the baffles of entrainment-separator 2, and then passes through tube 12 into spiral 14 of heat-exchanger 3 wherein it condenses to give primary condensate. This condensate flows through tube 15 into the space surrounding float-valve 16, and then passes through capillary 17 and tube 19 into the outer space 20 of heat-exchanger 3, which is evacuated by a vacuum pump connected to tube 27. The primary condensate is re-vaporized in space 20, and the vapours pass up tube 22 into condenser 4, which contains a spiral 26 traversed with cooling water via pipes 25. The secondary condensate flows out of the condenser through tube 27; and part of it is collected in a receiver as product while the remainder flows through branch-pipe 28, float-valve 29 and tube 32 to the outer space 20 of heat-exchanger 3. Float 30 operates in dependence on the liquid-level in space 20.