US 11,874,057 B2
Process to separate nitrogen from methane by permeation and cryogenic distillation
Martin Raventos, Champigny-sur-Marne (FR); and Paul Terrien, Syracuse, NY (US)
Assigned to L'Air Liquide Societe Anonyme Pour L'Etude Et L'Exploitation Des Procedes Georges Claude, Paris (FR)
Filed by L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude, Paris (FR)
Filed on Jul. 16, 2021, as Appl. No. 17/377,967.
Prior Publication US 2023/0022033 A1, Jan. 26, 2023
Int. Cl. F25J 3/02 (2006.01)
CPC F25J 3/0295 (2013.01) [F25J 3/0233 (2013.01); F25J 3/0257 (2013.01); F25J 2200/20 (2013.01); F25J 2205/40 (2013.01); F25J 2205/80 (2013.01); F25J 2280/50 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A process for the separation of nitrogen from a feed stream comprising methane and nitrogen, with a methane content between 4 and 12% mol, the process comprising the steps of:
a) separating the feed stream by means of a rubbery-type membrane to produce a permeate enriched in methane at a pressure greater than 2 bara and a non-permeate that is a nitrogen-enriched residue gas at a pressure greater than 2 bara;
b) processing of the high-pressure residue gas in a cryogenic separation unit to produce a methane rich liquid and a nitrogen-enriched gas; and
c) measuring the nitrogen concentration of the nitrogen-enriched gas,
wherein the pressure of the membrane permeate is controlled as a function of the nitrogen concentration in the nitrogen-enriched gas.