US 11,946,692 B2
Method for separating a mixture containing at least nitrogen and methane
Paul Terrien, Syracuse, NY (US); Nicolas Chantant, Grenoble (FR); and Jean-Marc Peyron, Creteil (FR)
Assigned to L'Air Liquide, Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude, Paris (FR)
Filed by L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude, Paris (FR)
Filed on Apr. 8, 2022, as Appl. No. 17/716,801.
Claims priority of application No. 2103659 (FR), filed on Apr. 9, 2021.
Prior Publication US 2022/0325951 A1, Oct. 13, 2022
Int. Cl. F25J 3/02 (2006.01)
CPC F25J 3/0233 (2013.01) [F25J 3/0257 (2013.01); F25J 3/0295 (2013.01); F25J 2200/06 (2013.01); F25J 2200/74 (2013.01); F25J 2290/12 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A method for separating a mixture containing at least nitrogen and methane by cryogenic distillation in a system of columns comprising a first column operating in a first pressure and a second column operating at a second pressure lower than the first pressure, the mixture being separated in the first column to form a first gas rich in nitrogen and a first liquid rich in methane, at least a portion of the first gas rich in nitrogen being at least partially condensed in a heat exchanger and returned to the first column, the liquid enriched in nitrogen being sent from the exchanger or from the first column to the second column, a second liquid rich in methane being withdrawn at the bottom of the second column and a second gas rich in nitrogen being withdrawn at the top of the second column, the heat exchanger comprising a stack of plates and fins, the plates being disposed with their axis vertically and the space between the plates forming vertical passages, wherein the first gas enriched in nitrogen is sent into the heat exchanger by the bottom, ascends in a first series of passages of the exchanger and condenses therein at least partially, the liquid formed descending in these passages of the first series and exiting via the bottom of the exchanger, the liquid descending in the second column being distributed to descend in another series of passages of the exchanger, therein evaporating partially to form a biphasic mixture which is collected at the bottom of the exchanger,
wherein no portion of the first liquid rich in methane is sent from the first column to the second column.