METHOD FOR PURIFYING HIGH-PRESSURE NITROGEN-CONTAINING NATURAL GAS TO REMOVE HELIUM Russian patent published in 2023 - IPC B01D61/58 

FIELD: gas mixture separation.

SUBSTANCE: method uses three stages of membrane separation. At the first and the second stages, membrane modules with increased selectivity to separable components in the following sequence: He>N₂>CH₄. On the third stage - in the following sequence: He>CH₄>N₂. The permeate flow of the first stage is compressed to the feed gas pressure and divided into two parts, one part is fed to the second membrane separation stage, where commercial natural gas components are separated from the helium concentrate into the retentate flow. The second part is fed to the third stage of membrane separation, where the residual amount of helium is extracted from the helium concentrate into the permeate stream. The third stage retentate stream with a high nitrogen content is used as fuel gas for the plant's own needs. The commercial natural gas leaving the unit consists of the combined retentate streams of the first and second stages of membrane separation, the helium concentrate consists of the combined permeate streams of the second and third stages of membrane separation.

EFFECT: creation of a method for purifying high-pressure nitrogen-containing natural gas to remove helium, which makes it possible to improve the qualitative composition of commercial products - natural gas and helium, and also to increase the volumetric calorific value of commercial natural gas by reducing its nitrogen content.

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