GB1454500A - Separation of gases - Google Patents

Abstract

1454500 Separating gases PETROCARBON DEVELOPMENTS Ltd 5 Dec 1973 [21 Dec 1972] 59165/72 Heading F4P A method of separating liquid chlorine from a feed mixture of chlorine, hydrogen and air in ratio 90À6 : 3À1 : 6À3 and in which it is desired to keep the proportion of hydrogen below 5%, this being the concentration which causes the mixture to become explosive, comprises distilling the mixture in column 16 within a temperature range above the critical temperature of hydrogen, such distillation occurring in the presence of CO 2 which is inert with respect to the mixture and is condensible, as is chlorine, above the critical temperature of hydrogen, and the CO 2 being provided as reflux for the distillation and in proportions such that the concentration of hydrogen does not reach the explosive point. As shown in Fig. 1, liquid CO 2 is vaporized in exchangers 18, 14 and expansion valve 19 before being combined with the feed, the combination being warmed in exchanger 13, compressed at 11 and cooled at 12, 13, 14, 15 to approximately -23‹ C. The mixture thus enters the distillation in a partially liquefied state, liquid chlorine being taken from the bottom. The liquid CO 2 fed to reflux condenser 18 is completely evaporated therein, causing CO 2 from the column 16 to condense as reflux. The overhead from column 16 of CO 2 , hydrogen and air is warmed to ambient temperature at 14, 13 and vented to atmosphere. Reboiler 17 is also provided. The liquid CO 2 can be introduced directly as reflux to column 16 (Fig. 3, not shown).