Apparatus for performing fractional distillation in a vacuum

摘要

In a vacuum still comprising an evaporating surface 12 surrounding a central condenser 14, and a rotary perforated member 2 mounted between the evaporating surface and the condenser, means are provided to prevent liquid which collects on the rotary member from being thrown back on to the evaporating surface. In the apparatus shown, the cross-section of the rotary member is a spiral; and the liquid is intercepted by a trough 32 at the outer terminal edge of the spiral. The evaporating surface 12 is heated by steam-jacket 17. The distilland is introduced on to the upper edge of the hot surface via pipe 11 and dished-plate 3 which has perforations 31. The distilland is distributed over the hot surface by brushes 38 fitted to the external edge of trough 32. The brushes may be made of synthetic resin. Some of the liquid evaporates, and the vapours first condense on the outside surface of the rotary member 2; the condensate passes through perforations 13 on to the inside surface from which some of it reevaporates. The liquid which finally condenses on condenser 14 runs down and collects in container 15. The liquid which does not evaporate from the rotary member collects in trough 32 and runs down into chamber 33; a proportion of this liquid may if desired be pumped back to the feed-pipe 11. The liquid-residue which runs off the bottom of the evaporator surface is withdrawn through outlet 24. In a modified form of still, the condensate on the rotary member is prevented from being sprayed on to the evaporator by a series of stationary sheet-metal baffles. Specification 929,747 is referred to.