Patent GB-1008394-A (GB)
Title: Recuperating caloric potential of liquefied gas during regasification
IPC: C07C11/04
Filed: 1964-08-06
Abstract: 1,008,394. Cold separation of gas mixtures. LUMMUS CO. Aug. 6, 1964 [Oct. 14, 1963], No. 32013/64. Heading F4P. The cold requirements of apparatus for separating and purifying ethylene from a gaseous mixture thereof with ethane, propane hydrogen methane and carbon monoxide are met by re-gasifying liquid natural hydrocarbon gas drawn from a vessel 10, Fig. 1, at - 161 C. and atmospheric pressure. A first portion of the liquid natural gas having the composition 87% methane, 11% ethane and 2% propane is bled from a line 13 through a reflux condenser 15 of a de-methanizer tower 16, a second portion serves to cool a heat exchanger 23 referred to later and the recombined liquid gas streams serve to cool exchangers 30 . . . 33 and the so warmed wet gas mixture is fed through a line 36 to the de-methanizer column 16 from the head of which substantially pure methane gas is withdrawn through a line 17, the condenser 15, a separator 19, a line 21 and is then heated to ambient temperature in exchangers 40, 41 and passed into a distribution line 46. Liquid ethane and propane withdrawn from the base of column 16 is vaporized in exchangers 48, 51 ethane from an external source is added through a line 54 and the mixture is heated at 52, 53 to produce pyrolysis gas consisting largely of ethylene and ethane but also containing methane, hydrogen, carbon monoxide and C 3  and heavier hydrocarbons. The pyrolysis gas mixture is compressed at 59, Fig. 2, and having been freed of carbon dioxide, hydrogen sulphide and water is liquefied in exchanger 40 and fed through a line 67 to a de-ethanizer column 68 from the head of which gaseous C 1 , C 2  hydrocarbons are withdrawn, partly condensed in said exchanger 30 and fed to a separator 73. The resulting liquid is returned to the column 68 as reflux whilst withdrawn gas is liquefied in exchangers 23, 30 and passed to a de-methanizer column 80 from the bottom of which liquid ethylene and ethane is fed through a line 93 to an ethylene separating column 94 whilst gaseous overhead from column 80 is condensed in exchanger 30 and fed to a separator 84 which supplies reflux to column 80 and gaseous methane containing hydrogen and carbon monoxide to a column 87. Gaseous hydrogen and carbon monoxide is withdrawn through an overhead line 89 and a mixture of liquid methane and carbon monoxide is withdrawn through a line 92. Gaseous ethylene is withdrawn from column 94 through a line 95 and is partly condensed in exchanger 30 and fed to a separator 97 which supplies reflux to said column 94 and from which product gaseous ethylene is withdrawn through a line 98a. Liquid ethane withdrawn from column 94 is vaporized in an exchanger 100 and is fed through a line 56 to form part of the feed to the pyrolysis heaters 52, 53. Liquid C 3  and heavier hydrocarbons are withdrawn from the base of de-ethanizer column 68 and passed to a de-propanizer column 101 overhead propane and propylene being partly condensed at 102 to provide reflux and substantially pure liquid propane which is withdrawn through a line 110 liquid C 4  and heavier hydrocarbons are withdrawn from the base of column 101 through a line 112.