Method and device for the cryogenic separation of a methane-rich flow

A method for the cryogenic separation of a methane-rich feed flow also comprising carbon dioxide and a second impurity selected from the group consisting of nitrogen, oxygen, and a combination thereof, said method comprising the steps of:

• i) sending the methane-rich feed flow to an adsorption purification unit to produce a carbon dioxide-lean flow having less carbon dioxide relative to the methane-rich feed flow;
• ii) cooling at least part of the carbon dioxide-lean flow to produce a cooled flow;
• iii) sending at least part of the cooled flow to a distillation column;
• iv) withdrawing a methane-rich product flow from the distillation column, the methane-rich product flow being richer in methane relative to the methane-rich feed flow;
• v) withdrawing a flow rich in the second impurity from the distillation column, the flow rich in the second impurity being richer in the second impurity relative to the methane-rich feed flow,
• vi) vaporizing at least part of the methane-rich product flow;
• vii) regenerating the adsorption purification unit using a regeneration fluid comprising at least part of the vaporized methane-rich product flow, such that a second product stream comp sing methane and carbon dioxide is produced;
• viii) monitoring the carbon dioxide content of the second product stream;
• and
• ix) maintaining the carbon dioxide content of the second product stream within a given threshold.