Patent ID: 11874057
Assignee: L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE
Field: Chemical engineering (Chemistry)
Classification: CPC F | IPC F

Claim 11:
12. The process according to claim 1, further comprising the steps of:
i) introducing a stream derived from the high pressure residue gas into the first distillation column to produce a nitrogen-rich gas stream and an impure methane liquid stream containing at least 5% mol. nitrogen;
ii) at least partially condensing at least part of the nitrogen-rich gas stream in a heat exchanger to produce a nitrogen rich stream;
iii) sending at least part of the liquid nitrogen rich stream to the second distillation column to be separated;
iv) separating the at least part of the liquid nitrogen rich stream to form a methane enriched liquid;
v) sending at least part of the methane enriched liquid to the third distillation column at a first height;
vi) condensing a top gas of the second distillation column In a bottom reboiler of the third distillation column;
vii) sending a liquid nitrogen rich stream from the top of the second distillation column into the third distillation column at a height above the first height;
viii) recovering a methane rich bottom liquid from third distillation column and then pumping the methane rich bottom liquid to a medium pressure of at least 3 bara; and
ix) combining at least part of the permeate from step a), at least part of the impure methane liquid stream and at least part of the methane rich bottom liquid from step b) viii to form a methane product.