GB408259A - Improvements in or relating to vacuum distillation of high boiling point products - Google Patents

Abstract

In the distillation of high-boiling substances such as fatty acids, glycerine, volatile products and fatty acids contained in oils, fats, waxes, &c. without using carrier vapour, and at absolute pressures lower than 10 mm. of mercury, reflux condensation is minimized by providing the still 2 with a deep vapour space 3 above the liquid in the still, and with a tubular baffle 4, so that the vapours first ascend to the top of the still and then descent in the space between the baffle 4 and the still wall 2 to the outlet 5 leading to the condensing system 6, 7, vacuum-producing means such as steam ejectors 8, 9, and a final tubular condenser 11. When the substance to be distilled contains substantial proportions of water or other low-boiling <PICT:0408259/III/1> impurities, the bulk of these may be removed in a preliminary still 1 of similar construction operating at a higher absolute pressure of 25--75 mm. of mercury (e.g. 50 mm. when the main still operates at 2 mm.). The vapours from the still 1 pass through a tubular condenser 19 and pipe 20 to the condenser 11, the outlet P of which is connected to a vacuum pump 10. The space between the baffle 4 and the still wall 2 may be heated by a steam coil 16, the condensate collecting at the bottom of condenser 6 may be heated by a coil 17, and the cooling water of condenser 6 may be maintained at a controlled temperature of over 100 DEG C. by means of an auxiliary condenser 18 which condenses the steam produced by the boiling of the cooling water and returns the condensed water to the condenser 6. The condensate from condenser 19 is discharged into a vacuum receiver 21 co-operating with an extraction pump 22 delivering at atmospheric pressure at 23, and the condensate formed in the baffle space of still 2, and in condensers 6 and 7 is withdrawn by pumps 25, 27, 28 through cooling coils 24, 26. The liquid in the stills is heated by circulating through the tubes 12 by means of the centrifugal impellers 13, as described in Specification 280,666, [Class 32], the tubes 12 being surrounded by a heating medium such as high-pressure steam.