This method comprises passing a residual stream into a flash drum to form a gaseous overhead flow and liquid bottom flow, and feeding the bottom flow into a distillation column,
It comprises cooling the overhead flow in a heat exchanger to form a cooled overhead flow.
It comprises the extraction of a gaseous overhead stream at the head of the distillation column, and the formation of at least one effluent stream from the overhead stream and/or from the top stream.
The separation of the cooled overhead flow comprises passing the cooled overhead flow into an absorber, and injecting a methane-rich stream into the absorber to place the cooled overhead flow in contact with the methane-rich stream.