Method and apparatus for separating nitrogen from a mixed stream comprising nitrogen and methane

A method of separating nitrogen from a mixed stream comprising nitrogen and methane, the method comprising at least the steps of:

• (a) providing a monolith sorption contactor formed of a unitary construction of active carbon, said contactor housing one or more separation flow channels intersecting the monolith sorption contactor, said one or more separation flow channels having at least one inlet to, and at least one outlet from, said contactor, said one or more separation flow channels defining one or more first internal surfaces of the monolith sorption contactor, said contactor further comprising one or more first external surfaces provided with a barrier layer, said first external surfaces being different from said first internal surfaces;
• (b) passing the mixed stream into at least one of the one or more separation flow channels via the at least one inlet;
• (c) sorbing the methane in the sorption contactor via the one or more first internal surfaces in the at least one of the one or more separation flow channels at a temperature lower than or equal to −60° C. to provide a nitrogen-enriched stream at the at least one outlet;
• (d) interrupting the passage of the mixed stream through the contactor;
• (e) regenerating the contactor by contacting the contactor with a heat exchange fluid stream at the one or more first external surfaces provided with the barrier layer, to heat the contactor to a temperature above −60° C. to desorb methane and provide a cool heat exchange fluid stream;
• and
• (f) withdrawing the desorbed methane as a methane-enriched stream from the at least one outlet from the contactor;
• wherein the barrier layer serves to provide a fluid barrier against passage of the heat exchange fluid into the monolith sorption contactor.