Patent GB-742779-A (GB)
Title: Improvements in process of, and apparatus for low-temperature separation of air
IPC: F25J3/04
Filed: 1953-12-23
Abstract: 742,779. Cold separation of air. UNION CARBIDE & CARBON CORPORATION. Dec. 23, 1953 [March 24, 1953], No. 35741/53. Class 8(2). Refrigeration during at least a period of working a continuous air separation process wherein compressed air freed of moisture and carbon dioxide by separated nitrogen and oxygen returning through regenerators or heat exchangers is provided by feeding liquid oxygen, nitrogen or air from an external container to the rectification column at a rate sufficient to supply refrigeration additional to that gained by cooling of the incoming air and an optional expansion thereof with the production of external work. In normal operation air from a compressor 110, Fig. 4, having traversed one or other of a pair of regenerators 111, the other being derived by return. ing nitrogen, and passages 150, 153 of regenerators 159, 157 cooled by returning oxygen is fed to a scrubber 123 cooled by low pressure nitrogen in a coil 145. The resulting liquid passes through an expansion valve 135, filters 136, and a duct 137 to the low pressure column 129, which is also supplied by a pump 173, with liquid oxygen from an insulated container 170 having a filling connection 175, whereas the vapour from scrubber 123 traverses a duct 124 to the high pressure column 125. Normal demand for gaseous oxygen of 95 per cent purity may be met by mixing compressed air in a valved duct 183 with product oxygen in a valved duct 160 and delivering through a duct 182. Pure oxygen may be drawn through the duct 160 by a compressor 161 controlled by a pressure responsive member 187 and discharging through a duct 163. Additional demand is met by a pump 180 drawing liquid oxygen from the container 170 and discharging it through a vaporizer 178, a check valve 186 and ducts 179, 163 ; additional air being supplied to the rectification columns by a booster compresser 185. In a modification refrigeration during a normal working period is provided by expansion at a turbine 54, Fig. 1, of a portion of scrubber vapour which has been warmed in a passage 57 by incurring dry air in a duct 56 tapped from near the base of regenerators 11, 12 and containing a little carbon dioxide which is condensed in passage 57. Periodic deriming of passage 57 and the closing down of turbine 54 is effected without discontinuing the rectification process by closing valves 60, 61, 71, 72 and opening a valve 62 to by-pass the tapped air to the scrubber 23 ; the necessary refrigeration being supplied by passing liquid oxygen from a container 80 through a duct 82 to the oxygen collecting chamber 30 of the low pressure column 29. A peak demand for oxygen gas is met by pumping liquid oxygen from the container 80 through a duct 93 and a vaporizer 96 to a duct 92 where it supplements the normal oxygen drawn from a duct 52 by a compressor 90 discharging into a duct 91. In a further modification the additional refrigeration to meet peak demand for oxygen is provided by liquid nitrogen in an external container and in a still further modification the external oxygen is replaced by liquid air. Specification 633,222, [Group XXVI], is referred to.