Patent GB-1387472-A (GB)
Title: Thermal cycle for the compression of a fluid by the expansion of another fluid
IPC: F25B9/00
Filed: 1972-01-28
Abstract: 1387472 Separating gases; refrigeration L'AIR LIQUIDE SOC ANON POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGE CLAUDE 28 Jan 1972 [1 Feb 1971] 4240/72 Headings F4P and F4H In a process involving a mixture of gases and in which a first relatively volatile is available at a first pressure and a second relatively involatile gas is available at a second, lower, pressure, expansion of the first gas is used to effect pressurization of the second gas with a consequent recuperation of energy. The first gas is supplied via 17, Fig. 1, to the base of a high pressure (H.P.), mixing column 1 and the second gas to the base of a L.P. separating column 2, two fractions being extracted from column 1 and expanded in valves 53, 55 to effect directcontact heat-exchange with the second gas and a liquid fraction from column 2 being pumped via line 50 to column 1, to obtain the second gas at H.P. at 18 and the first gas at L.P. at 16. The process may be used in separating gases, refrigeration or power generation. Separating gases.-A mixture of two gases is supplied to the mid-region of column 2, Fig. 7 (not shown), and some of the more volatile gas issuing at 16 is compressed, forming the feed at 17, whilst some of the less volatile gas issuing at 18 is expanded, a portion of this gas forming the feed 15. In an air separation plant, Fig. 8, the separating column 2 is formed by the lower part of the L.P. stage 59 of a two stage rectification column. Compressed air is cooled in heat exchanger (h.e.) 22 by product oxygen and nitrogen and the major portion is fed to H.P. stage 24 from which O 2 -rich and N 2 -rich liquid fractions are withdrawn via lines 26, 27, cooled in h.e.'s 28, 29 and expanded into the L.P. stage 59 from the top of which product N 2  gas is withdrawn. A small portion of feed air is partially rewarmed in h.e. 22, expanded at 60 and fed to L.P. stage 59, whilst the remaining portion of feed air is led to the bottom of the H.P. mixing column 1, from the top of which product O 2  (95% pure), gas is withdrawn. The two fractions extracted from column 1 are, prior to expansion heat exchanged at 31 with the liquid fraction being pumped from column 2 to column 1. In a modification, Fig. 9 (not shown), yielding pure O 2  at 4À5 ata, the cold for the process is provided by work-expansion of a stream of N 2  gas withdrawn from the top of H.P. stage 24. A fraction rich in argon is withdrawn from L.P. stage 59 and fed to a separator the overheads from which contain 70% argon. The bottoms are added to the liquid fraction being pumped to column 1. Liquid O 2  is withdrawn from the base of column 59 and pumped through h.e.'s (71), 22 and a vaporizer at the top of column 1. In another similar arrangement, Fig. 10 (not shown), some liquid O 2  product is withdrawn from the bottom of column 59. Refrigeration.-In a vaporization-refrigeration cycle, Fig. 12, comprising a compressor 116, condenser 112, expansion valve 171 and vaporizer 113, a portion of compressed gas is fed at 17 to the bottom of the h.p. mixing column 1 where it is mixed with a less volatile fluid pumped from the L.P. separating column 2, a less volatile fraction being withdrawn from the head of column 1, condensed at 114, expanded through valve 115, vaporized in condenser 112  to provide the cold for the main cycle, and fed to the bottom of column 2 where it is heatexchanged in direct contact with two fractions withdrawn from column 1 and expanded through valves 53, 55. From the top of column 2 is extracted a L.P. stream of the original gas which is returned upstream of the compressor 116.