GB716498A - Improvements in or relating to the fractional distillation of high boiling liquid mixtures - Google Patents

Abstract

<PICT:0716498/III/1> In a process for the fractional distillation under reduced pressure of a mixture of high boiling liquids such as fatty acids, wherein superheated steam is passed through the fractionating column and/or a subsequent stripping column, saturated steam is generated by a heat exchange step with the vapours withdrawn from the top of the fractionating column, and this saturated steam is then superheated and used in the fractionating column and/or stripping column. A mixture of cotton seed fatty acids at 50 DEG C., contained in tank 1, is introduced through conduit 2 into dehydrator 3, which is connected to foam - separator 4 and vacuum producer 5. The pressure at the head of the dehydrator is maintained at 3 mm. Super-heated steam is injected into the dehydrator through line 25. Fatty acids entrained in the steam leaving the dehydrator are separated in foam-separator 4. Dehydrated fatty acids, withdrawn from the dehydrator and separator by means of conduits 6a and 6b respectively, are heated to 250 DEG C. in preheating system 7. The preheated acids are introduced, through one of the inlets 9a to 9f, into the side of fractionating column 10, which is heated at the base by reboiler 16 and is connected at the top to evaporative-condenser 11. The cooling side of the condenser contains water, boiling under a pressure of 65 p.s.i.g. The head of column 10 is maintained at a pressure of 3mm. Part of the fatty acid condensate from condenser 11 is returned to the column as reflux, the remainder being withdrawn as product through conduit 13. Part of the bottoms withdrawn from the base of column 10 is passed through conduit 18 to steam stripping column 19, which is maintained at 3 mm., and is surmounted by water-cooled, evaporative-condenser 21, The fatty acid overhead product from column 19 is collected in receiver 23; and non-distilled residue is withdrawn from the base of the column into receiver 33. Hot water is supplied to condensers 11 and 21 from tank 24 by means of conduit 26. The steam evolved in the condensers is passed through lines 27a and 27b to superheaters 28 and 29. The superheated steam from superheater 28 is injected through conduit 30 into reboiler 16, from whence it passes into column 10 through conduit 17, together with the circulating bottoms. Steam from superheater 29 is injected through conduit 31 into the base of stripping column 19. The steam which is injected into columns 10 and 19 passes together with vaporized fatty acids into condensers 11 and 21 repectively, but does not condense therein on account of the high temperature and low pressure; the steam is withdrawn from the condensers and is led to dehydrator 3 through line 25. This steam carries with it a trace of fatty acid in the form of mist, which is subsequently removed in foam-separator 4. The single fractionating column 10 may be replaced by a number of fractionating columns arranged in series. Specification 716,497 is referred to.