Patent GB-737387-A (GB)
Title: Improvements in or relating to cold separation of gases
IPC: F25J3/04
Filed: 1952-06-19
Abstract: 737,387. Cold separation of air. JOY MANUFACTURING CO. June 19, 1952 [July 10, 1951], No. 15434/52. Class 8 (2). An air rectification process yielding product oxygen at an outlet 129, Fig. 1, comprises passing compressed air through a reversing valve 8, ducts 12, 18 of a two-part reversing heat exchanger 15 traversed by cold returning nitrogen in ducts 28, 30 and cold product oxygen containing at least 25 per cent liquid in ducts 118, 128 resulting in condensation of carbon dioxide in duct 18, passing the so cooled air through a reversing valve 24, reheating a portion in a duct 46 of a heat exchanger 48 traversed by air, nitrogen or oxygen or a combination thereof after traversing one stage and prior to traversing the other stage of the exchanger 15, e.g. warmed returning oxygen leaving the duct 118 and prior to entering duct 128, expanding said portion in an engine 50 with the performance of external work and feeding at least the unheated portion through a duct 72 to the rectification column 78, preliminarily heating nitrogen from an outlet 90 in an exchanger 58 prior to passing it along a duct 94 and valve 24 to duct 28 where it vaporizes carbon dioxide deposited during the previous cycle, and finally passing it through duct 30 and valve 8. As shown, cold air leaving the valve 24 traverses a filter 40 and is joined by the reheated and expanded portion together with a portion of effluent nitrogen through a valve 112 at a point 70 before traversing a coil 74, the exchanger 58 and a duct 84 leading to the column 78. Part of the effluent nitrogen bypasses the exchanger 58 through a restricted duct 106, and reheater 48 may also be in part by-passed by a restricted duct 126. A heat barrier 133 positioned between the oxygen duct 118 and the nitrogen and air ducts 20, 18 at the bottom two-thirds of the exchanger portion 20 serves to prevent the temperature of returning nitrogen from falling below that at which it vaporizes carbon dioxide. In a modification the wetness of the oxygen leaving the outlet 116 is controlled by a float device. In a further modification using a two-stage column the combined reheated expanded air, the unheated air and the portion of effluent nitrogen are fed to the high-pressure stage of the column, oxygen-rich liquid passes therefrom through the exchanger 58 to the low-pressure stage, and the wet oxygen is taken from the base thereof. In a still further modification using a single column the expanded portion of air is joined by effluent nitrogen and traverses the exchanger 178, Fig. 4 (not shown), and a duct 941 to the exchanger 15. In a modification of the double-column device the effluent nitrogen by-pass 106 is eliminated as is the oxygen duct of the reheater 48. In apparatus for the production of liquid oxygen product at a valved duct 496, Fig. 6, at the base of a column 478 the wet oxygen is forced by a pump P along a duct 504 to duct 506 of portion 420 of exchanger 415 and is returned to the column along a duct 508 which includes a valve 512 controlling a temperature bulb 514 in the duct 442 traversed by that portion of cold air entering the reheater 433 prior to expansion at the engine 450. In a still further apparatus for the production of liquid oxygen the reversing heat exchanger is cooled by partially liquefied air bled from the coil at the base of the column and passed through a separator.