A refining system for refining a feed gas (10) includes a first and a second component, the first component having a lower dew point temperature than the second component; the refining system including:—an input section (105) for input of the feed gas including a dehydration unit for dehydrating the feed gas, capable of obtaining a water dew point between −45 and −65° C.;—a pre-cooling section (110) coupled to the input section for receiving the dehydrated feed gas;—a fractionation section (115) coupled to the pre-cooling section for receiving the pre-cooled stream;—an expansion cooling and separation section (120) coupled to the fractionation section for receiving the fractionated gas, including a cyclonic separator device (240); the expansion cooling and separation section having an reflux conduit coupled to the fractionation section for reflux (24) of liquid enriched with the second component to the fractionation section.