Patent GB-1023309-A (GB)
Title: Fractional distillation of liquid mixtures
IPC: B01D5/00
Filed: 1963-12-27
Abstract: 1,023,309. Fractional distillation; tall oil. SPENCE & GREEN CHEMICAL CO. Dec. 27, 1963 [Dec. 26, 1962], No. 51043/63. Heading B1B. Fractional distillation apparatus, which may be operated under high vacuum and is particularly suitable for separating a mixture of fatty acids into several fractions, comprises at' least two elongated horizontal evaporation vessels connected in series for liquid-flow, the vessels being provided with means for the differential condensation of vapour and return of the condensates to the evaporation zone at spaced points upstream of the points where the condensed components were vaporized, conduits for withdrawing at least two vapour streams from the first vessel, means for condensing these streams and for introducing the condensates at spaced points along the second vessel, and means for withdrawing rectified fractions from the second vessel. The apparatus shown in Fig. 6 comprises six evaporatorcondenser units suitable for the separation of tall oil into rosin acids, fatty acids and other fractions. Each vessel has a platen 24, Fig. 2, with hollow channels 25 for the circulation of heating-medium. An entrainment separator 36 is mounted a short distance above the platen. The wall and top of the vessel is enclosed in a jacket 28 with means for circulating coolant. The liquid being fractionated flows over the platen in the form of a film, and some of the liquid vaporizes as it flows downstream. The vapours condense differentially along surface 31, and the condensates fall back on to the platen upstream from the point of evaporation of the fraction. The upstream end of each unit is provided with a dephlegmating condenser, and one of the units, viz. 103, has two additional dephlegmators 162, 163. The tops of the dephlegmators are connected to a vacuum manifold. Dephlegmators 165 and 166 have water-cooling jackets. Tall oil is dried and introduced through line 120 into unit 101. Two condensate cuts 146 and 147 are removed from dephlegmator 145. Cut 146 is conveyed to the hot platen of unit 102 ; and cut 147 is introduced into the dephlegmator 160 of this unit. Light ends are withdrawn from dephlegmator 160 via line 192. The liquid mixture which has not been vaporized in unit 101 is conveyed through line 199 on to the hot platen of unit 103 where further vaporization takes place, and the liquid leaving unit 103 flows through line 210 to unit 104. Pitch is discharged from unit 104 through line 215. The liquid effluent from unit 102 is conveyed via line 220 into unit 105. Several separated fractions 201-208 from the dephlegmators of units 103 and 104 are introduced at horizontally spaced points along unit 105 where the composition of each fraction matches the composition of the vapour at the particular point where it is introduced. Rosin acids are withdrawn from unit 105 via line 225. A fraction rich in fatty acids and a light ends fraction are withdrawn, via lines 230 and 231 respectively, from the dephlegmator 165 of unit 105. The fatty acids fraction is further rectified in unit 106 from which purified fatty acids are withdrawn via line 240. Residual light ends and a mixture of rosin acids and fatty acids are withdrawn from unit 106 via lines 245 and 236 respectively. In order to increase the purity of the fatty acids withdrawn through line 240, phthalic anhydride and/or maleic anhydride may be introduced into unit 106 in order to suppress phenol and other colour-forming impurities.