| 摘要 |
<PICT:0744844/III/1> Apparatus for fractional distillation comprising a distillation column and a reflux condenser is associated with at least one external falling-film evaporator consisting of a heated upright tube on the inner wall of which (a) distilland is distributed by wipers or brushes, and a pipe for introducing into the column the vapours generated in the evaporator. The apparatus is particularly suitable for the fractionation of heat-sensitive liquid mixtures; in this case a film evaporator of the type described is used as reboiler for the liquid reaching the base of the column. The vapour formed in such an evaporator has a higher concentration of the higher-boiling constituents than in the case of a circulation evaporator; and consequently the required height of column becomes less at the lower end where the danger of thermal decomposition is greater. In the apparatus shown, the feed liquid is distributed on the inner wall of film-evaporator 1; and the vapours evolved therein are introduced into column 3 while the unevaporated liquid is collected in receiver 2. Liquid from the base of the column flows through siphon 5 into film-evaporator 4; and the vapours evolved therein are passed to the column through pipe 6. The liquid-residue is collected in receiver 7. The vapours leaving the head of the column are condensed in cooler 8. The condensate is separated by distributor 9 into product-distillate which is collected in receiver 10, and reflux which is returned to the column through siphon 11. The system may be evacuated through pipe 12. |
