Patent GB-756901-A (GB)
Title: Improvements in the cold separation of gas mixtures
IPC: F25J3/04
Filed: 1954-10-11
Abstract: 756,901. Cold separation of gas mixtures. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Oct. 11, 1954 [Oct. 9, 1953], No. 29296/54. Class 8(2). In a low temperature gas mixture fractionating apparatus wherein thermal energy is extracted from the head of a rectification column 1, Fig. 1, by removal of vapour through a duct 15 to a space adjacent the freezer of a refrigerator 17 of the reversed hot gas engine type where it is condensed and returned to the column as reflux, at least part of the condensate is forced by bubble pump action up ducts 21, 22 so as to discharge into the column at a point above that at which it leaves the refrigerator 17 and means is provided whereby the supply of reflux is governed by the level of liquid, i.e., the high boiling constituent in the evaporatorboiler 2 of the column 1 ; the remainder of the condensate being withdrawn from the column through a duct 24 and a liquid trap 25. In operation air freed of water vapour and carbon dioxide and cooled by oxygen vapour returning from the boiler 2 through a heat exchanger 4 traverses an annular cooling duct 8 and enters the column 1 through apertures 9 at subatmospheric pressure. The forcing of liquid nitrogen up ducts 21, 22 which rise from an annular duct 20 supplied with liquid nitrogen from the refrigerator 17 is effected by vapour plugs generated by heat conducted along a copper rod 26 connected to the ducts 21, 22 and to one end of a copper rod 27 having its other end connected to the warm end of the exchanger 4 and its mid-portion connected to vanes 30 located in an overflow chamber 29 of the liquid oxygen boiler 2. Cooling of the vanes 30 by overflowing liquid oxygen results in decreased flow of reflux nitrogen up ducts 21, 22 and a consequential fall in the oxygen level in boiler 2. Forcing of liquid nitrogen up a discharge duct 23 is effected by vapour plugs generated by heat conducted through the wall of duct 8. In a modification the latter means effects the forcing of reflux nitrogen up ducts 21, 22 and flow of reflux is effected by heat conducted along a copper rod having one end connected to the duct 23 and the other end dipping in the overflow chamber, the oxygen content of which being at a higher temperature than the incoming liquid nitrogen results in an increased discharge of nitrogen from the column and a corresponding decreased supply of reflux to it. In a further modification vapour rising from the boiler 2, Fig. 5, is condensed to provide reflux by vaporization of an auxiliary liquid, e.g., nitrogen traversing a condenser 50 and is also condensed by vaporization of said nitrogen traversing a condenser 51 and collected in an annular duct 62 from which it is discharged from the column through a duct 63. Nitrogen vapours from condensers 50, 51 are led to the refrigerator 18 where they are condensed and the condensate is supplied through a duct 55 to an annular duct 56 from which it is forced by bubble pump action effected by thermal conduction along rods 61, 27 and vanes 30 as described with reference to Fig. 1 up ducts 57, 58 to the condenser 50. Liquid nitrogen from duct 56 is also forced up ducts 59, 60 to condenser 51 by bubble pump action effected by thermal conduction through the wall of annular duct 8. The proportion of reflux supplied to the column to the liquid discharged through duct 63 depends on the relative amounts of auxiliary liquid supplied to the condensers 50, 51 and this in turn depends on the level of liquid oxygen in the boiler 2. Specifications 695,857 [Group XIII], 756,895, and 756,897 are referred to.