GB648979A - Improvements in or relating to the production of oxygen by liquefaction of air - Google Patents

Abstract

648,979. Air separation. HYDROCARBON RESEARCH, Inc. Dec. 19, 1947, No. 33605. Convention date, Dec. 21, 1946. [Class 8(ii)] Carbon dioxide is removed from air prior to liquefaction and rectification by passing a stream of air through a path 12, Fig. 1 in a heat-exchanger 10 in indirect countercurrent heatexchange relationship with a stream of rectification product, e.g. nitrogen in a path 13 and warming a minor portion of the cooled air, e.g. by passing it through a path 11 to a temperature such that on subsequent expansion, e.g. at an engine 29 substantially more of the expanded air is liquefied, and maintaining the temperature difference of the air leaving and of the nitrogen entering the exchanger 10 between 5‹ and 10‹F. and periodically switching the flow of air and nitrogen through their respective paths, e.g. by operating valves 14, 15, to effect removal of deposited carbon dioxide. In operation, air from a branch 16 of the main inlet 9a traverses the switching or reversing valve 14, the path 12, a line 20 the reversing valve 15 to a line 22 from which the said minor portion traverses a line 24 the duct 11 and a line 27 where it is united with a portion of the remaining air in a line 3 before being cooled at the expander 29 and fed into a low pressure rectification column 52. Simultaneously air from a branch 43 traverses a reversing valve 41 a path 34 in a second exchanger 33 in heatexchange with returning oxygen in a path 35, a line 47, and reversing valve 42 and a line 48 leading to the line 30. The air and oxygen paths are switched by the valves 41, 42 and further cooling is effected by nitrogen from the column 52 flowing through a path 36. Cool air from the line 30 not expanded at the expander 29 is further cooled at exchangers 54, 55 by returning oxygen and nitrogen. In a modification each exchanger 10, 33 is divided into two sections, one section only of each exchanger having the switchable paths. In a further modification one reversing exchanger only 80, Fig. 3, is provided and air having passed the reversing valve 14 deposits carbon dioxide in a path 81 where it is cooled by returning nitrogen and oxygen in paths 82, 83 and nitrogen in a non- switching path 85. The said minor portion of cooled air is warmed by passing it through a path 84. Specifications 469,943 and 647,483, [Group XIII], are referred to.