| 摘要 |
<p>An improved process for cryogenically separating helium from a helium-bearing natural gas (2) is disclosed. The process comprises the steps of cooling said natural gas (2) by indirect heat exchange (3) to condense a portion of the methane and condensable C2 and higher hydrocarbons contained therein. The partially condensed natural gas stream then is separated (5) to recover both a first liquid phase effluent stream (4) comprised of a condensed portion of the methane and condensable C2 and higher hydrocarbon compounds and a first vaporous phase (7) comprised of helium, nitrogen and the remaining balance of the methane and condensable C2 and higher hydrocarbon compounds. This first vaporous phase (7) then is cooled (9) to condense a major portion of the remaining methane and substantially all of the remaining C2 and higher hydrocarbons. Separation (13) of this further cooled first vaporous phase provides a second liquid phase effluent stream (12) comprised of a condensed major portion of the remaining methane and the remaining balance of the C2 and higher hydrocarbon compounds and a second vaporous phase (15) comprised of helium, nitrogen and a remaining minor portion of the methane. The second vaporous phase is further cooled by indirect heat exchange (17), its pressure reduced (19) and subjected to a final separation (23). In this final separation (23), a gaseous product stream (25) comprising at least 50 volume percent of helium, the balance being substantially nitrogen, and a third liquid phase effluent stream (22) comprising the remaining minor portion of the methane and a major portion of nitrogen individually are recovered. The process further comprises the combining of the first (8) and second (12) liquid phase effluent stream and the subsequent separation (27) of said streams into a natural gas liquids stream (32) and a residue gas stream (29).</p> |
