GB666094A - Improvements in processes for liquefaction and possible separation of gases - Google Patents

Abstract

666,094. Gas separation &c. L'AIR LIQUIDE, SOC. ANON. POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES G. CLAUDE. July 15, 1949 [July 24, 1948], No. 18726/49. Class 8 (ii) In a gas liquefying or a gas mixture separation process wherein cooling is effected in at least one heat exchanger and in a cold expander operated at liquefaction temperature with the production of external work, cold is supplied to the exchanger by expanding with external work a gas taken at or near the temperature of the surrounding atmosphere and transferring this cold directly or indirectly over the whole length of the exchanger or at least over its warmer portion. As applied to an air separation process wherein air at 5 to 6 atmospheres pressure after being cooled in nitrogen and oxygen regenerators N, O, Fig. 1, and a cold expander D is separated in a two stage column A, B, the regenerators N<SP>1</SP>, O<SP>1</SP> undergoing regeneration by returning nitrogen and oxygen from the column B are supplied with cold by taking from their warm ends a portion of the carbon dioxide and water bearing nitrogen and oxygen, compressing to 150 atmospheres pressure at compressors C<SP>1</SP>, C2, expanding to about one atmosphere at warm expanders D<SP>1</SP>, D<SP>2</SP> and returning the so warmed nitrogen and oxygen to the regenerators N<SP>1</SP>, O<SP>1</SP> at points preferably above the region of condensation of carbon dioxide. In a modification about three per cent of the air being cooled in the exchanger M is removed therefrom at a point where water vapour has been condensed, is expanded and fed into the regenerator N<SP>1</SP> under regeneration and a second small portion of air removed from the regenerator N at a point where carbon dioxide has been condensed is expanded and fed into the regenerator N<SP>1</SP> at a point below the entry of the first expanded portion. In a further modification nitrogen from the top of the high-pressure column A, Fig. 3, is divided into a first portion which is warmed in an exchanger 3 embedded in the regenerator N<SP>1</SP> and into a second portion which is joined by some of the nitrogen leaving the exchanger 3 before traversing the cold expander D. This cold nitrogen is then joined by nitrogen' from the top of the low pressure column B and is supplied to the regenerator N<SP>1</SP>. The remainder of the nitrogen leaving the exchanger 3 is further warmed in an exchanger 6 before traversing a warm expander D5 and being supplied to the regenerator N<SP>1</SP> at a point intermediate its length.