Patent GB-683121-A (GB)
Title: Improvements relating to the separation of component substances from mixtures thereof
IPC: B01D3/00
Filed: 1947-12-29
Abstract: <PICT:0683121/III/1> <PICT:0683121/III/2> <PICT:0683121/III/3> Fractional distillation or chemical interchange reactions are carried out in a plurality of tubes or similar contacting-devices, wherein countercurrent flow of two different phases takes place, and each contact-device is provided with a throttling device through which one of the components of the mixture-being-treated, is withdrawn from the contacting-devices.  Column-stills.  Distilland is supplied via line 71, Fig. 2, to electric-still 72 which is connected to heat-insulated fractionating-column 70 surrounded by four separate heating-jackets 120 to 123; and the vapours enter tubes 5 through capillaries 83. The upper ends of tubes 75 are cooled, and reflux is formed therein, by cooling-space 17 which contains a boiling liquid.  To improve "wetting" the insides of tubes 75 may be roughened, covered with fabric, or coated with waterglass.  The "heads" are withdrawn from the tubes 75 through throttling-capillaries 29, and leave the column via take-off 15. The capillaries 29 ensure that the quantity of "heads" extracted from each tube 75 is the same despite slight variations in pressure from tube to tube.  The reflux leaving the lower ends of tubes 75, passes through filling-material 107 and enters electric-reboiler 103 from which the "bottoms" are withdrawn via syphon 108 to receiver 111.  Cooling-space 17 is connected to a re-cooler 19 wherein the vapours evolved from the liquid in space 17 are condensed; and the arrangement may be such that the descending liquid is heated nearly up to the boiling-point by the ascending vapour.  In Fig. 3, the reflux flowing down the tubes 75 is re-evaporated, by means of hot vapours from boiler 136, in the lower ends of the tubes which are closed but provided with capillaries 127 from which part of the vapours is withdrawn as "bottoms."  In Fig. 4, the vapours leave the upper ends of the tubes through branch-pipes 85.  The majority of the mixed vapour withdrawn through pipe 87 is condensed in cooler 89; and part of the condensate is returned to the tubes through capillaries 86, while the remainder, together with the uncondensed vapour, is withdrawn through one or other of pipes 92 to 94, depending on the reflux ratio to be maintained.  Vertical or parallel plates, fitted with horizontal cooling channels, may be used as contact devices instead of tubes 75; capillary tubes being the means of entry and exit to and fro the spaces between the plates.  In an example, benzene was separated from a mixture containing 10 mol per cent benzene, the remainder being toluene, by fractionation at a pressure of 350 mm.  Methyl acetate was used as cooling-liquid; and a reflux ratio of 18 : 1 was employed.  The overhead, which comprised 99 mol per cent benzene, was takenoff at the rate of 1,000 c.c. per hour.  Another example relates to the separation of benzene and carbon tetrachloride.  Chemical interchange reactions.  In an example, a concentrated solution of ammonium chloride is run down a plurality of vertical tubes; and caustic soda solution is introduced near the foot of each tube, thereby liberating gaseous ammonia which rises through the tubes in countercurrent to the downflowing ammonium chloride. There occurs an increase of concentration of the N15 isotope in the lower part of the tubes.  A capillary outlet for NH3 enriched in N15 is provided in each tube just above the NaOH inlet, while NH3 containing predominantly the N14 isotope is withdrawn from the tops of the tubes.ALSO:A dissolved material is extracted from a liquid into another liquid, by flowing the two liquids countercurrent to each other through a plurality of tubes or similar contacting-devices e.g. parallel plates, each contact-device being provided with a throttling-device such as a capillary tube, through which one of the liquids is withdrawn from the contact-devices.  The detailed examples and the drawings of the specification relate to apparatus for fractional distillation.