Improved process for continuously separating a gaseous mixture

Abstract

Abstract 266,396. Wade, H., (Naamlooze Vennootschap Philips' Gloeilampenfabrieken). Sept. 23, 1925. Gases, separating mixtures of; diffusion apparatus for gases.-A process for separating the constituents of gaseous mixtures by treatment in a series of diffusion separators, each separator being capable of separating the mixture into at least two fractions, comprises admitting the mixture to one of the separators and delivering the resulting fractions to separators located on each side of that separator; the separators to which the fractions are delivered give rise to further fractions which are returned, in part, to the separator to which the mixture was supplied, and the arrangement is such that the quantity of gas supplied by one separator to a second is almost equal to the quantity supplied to that separator by the second. Instead of, or in addition to, delivering the fractions to separators located on each side of a given separator, one fraction may be returned the separator in which it was produced, the remaining fraction or fractions being delivered to at least one nearby separator; in that event the arrangement is such that the quantity of gas supplied by a separator to a nearby separator is almost equal to the quantity supplied to that separator by the nearby separator. To ensure substantial equality in the amounts of gas exchanged between two separators, the resistance of the path from one separator to a second is made substantially equal to the resistance of the path to that separator from the second. Suitable apparatus comprises a series of five separators a - - e, Fig. 1, to which the mixture to be treated is supplied by a pump 9 through a tube 1 forming part of the middle separator c. Within the tube 1 is a porous tube 2 consisting, for example, of rolled paper and communicating with a tube 3. The tube 3 is connected to a pump 6 supplying the separator b, and the tube 1 is connected through a tube 4 to a pump 5 supplying the separator d. The less diffusible fraction produced in the separator b, and the more diffusible fraction produced in the separator d, are delivered, through tubes 7, 8 respectively, to the pump 9 supplying the separator c. Tubes 10, cooled by liquid air, are provided to free the gases from impurities coming from the pumps. In use, the apparatus is exhausted and the mixture is admitted until a low definite pressure is attained. whereafter the apparatus is put into action and the separated constituents collected in, or continuously withdrawn from, vessels 11, 12 connected to the extreme separators, Fig. 2. shows a modified apparatus in which each of the five separators a<1> - - e<1> has two norous tubes and gives rise to three fractions. The mixture to be treated is supplied by a pump 14 to the middle separator c<1> through a tube 13 enclosing a porous tube 16. The tube 13 is connected by a tube 17 to a tube 18 enclosing a second porous tube 19: the tube 19 is connected to a tube 20. The fraction diffusing through the tube 16 is delivered by a pump 15 to the separator b<1>, the fraction which does not diffuse through the tube 16 but diffuses through the tube 19 is returned bv the tube 20 to the pump 14 and so to the separator c<1>, and the fraction which does not diffuse through either of the porous tubes is delivered by a pump 21 to the separator d<1>. These fractions may be produced in the ratio 1 : 4 : 1 by making the resistances of the tubes 16, 18 each four times as great as the resistance of the tube 19. Reference is made to the separation of mixtures of helium and neon and to the separation of isotopes, for example the isotopes of neon.

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