Patent EA-001330-B1 (EA)
Title: Process for separating hydrocarbon gas constituents
Inventor: CAMPBELL WANDA P
IPC: F25J3/02
Filed: 1998-04-16
Abstract: 1. A process for the separation of a gas stream containing methane, C2 components, C3 components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing said C2 components, C3 components and heavier hydrocarbon components or said C3 components and heavier hydrocarbon components, in which process  said gas stream is cooled under pressure to provide a cooled stream; said cooled stream is expanded to a lower pressure whereby it is further cooled; and said further cooled stream is fractionated at said lower pressure whereby the components of said relatively less volatile fraction are recovered, wherein prior to cooling, said gas is divided into gaseous first and second streams; and a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed; said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream; said compressed recycle stream is combined with said gaseous first stream to form a combined stream; said combined stream is cooled to condense substantially all of it; said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position; said gaseous second stream is cooled under pressure sufficiently to partially condense it; said partially condensed second stream is separated thereby to provide a vapor stream and a condensed stream; said vapor stream is expanded to said lower pressure and supplied at a first mid-column feed position to a distillation column in a lower region of said fractionation tower; at least a portion of said condensed stream is expanded to said lower pressure and is supplied to said distillation column at a second mid-column feed position; and the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered. 2. The process as claimed in claim 1, wherein further comprises cooling a gas stream sufficiently to its partial condensation, separating said partially condensed gas steam thereby to provide a vapor stream and a condensed stream, combining said compressed recycle stream with at least said condensed steam to form a combined stream, expanding said vapor stream to said lower pressure and supplying to said distillation column at a mid-column feed position. 3. The process as claimed in claim 1, wherein further comprises cooling a gas stream prior to dividing into first and second streams, expanding said second stream to said lower pressure after dividing and supplying said expanded second stream to said distillation column at a mid-column feed position. 4. The process as claimed in claim 2, wherein further comprises dividing said vapor stream to gaseous first and second streams, combining said compressed recycle stream to said gaseous first stream to form a combined stream, expanding gaseous second stream to said lower pressure and supplying to said distillation column at a first mid-column feed position and expanding at least a portion of said condensed stream to said lower pressure and supplying to said distillation column at a second mid-column feed position. 5. The process as claimed in claim 4, wherein further comprises combining said compressed recycle stream with said gaseous first dtream and with at least the portion of said condensed stream to form a combined stream and expanding said gaseous second stream to said lower pressure and supplying to said distillation column at a mid-column feed position. 6. The process as claimed in claim 1, wherein further comprises cooling said gaseous second stream and expanding to said lower pressure and supplying supplying to said distillation column at a mid-column feed position. 7. The process as claimed in claim 1, wherein further comprises cooling said second stream, sufficient to its partial condensation, separating said partially condensed second stream to provide a vapor stream and a condensed stream, expanding said vapor stream to said lower pressure and supplying to said distillation column at a first mid-colimn feed position. 8. The process as claimed in claims 2 or 5, wherein further comprises expanding at least a portion of said condensed stream to said lower pressure and supplying to said distillation column at a second mid-column feed position. 9. The process as claimed in claims 1, 4 or 7, wherein further comprises cooling said condensed stream and dividing it to a first and second liquid portions prior to said expantion, expantion said first liquid portion to said lower pressure and supplying to said column at a mid-column feed position and expantion said second liquid portion to said lower pressureand further supplying to said column at a higher mid-column feed position. 10. The process as claimed in claim 9, wherein further comprises heating said expanded first liquid prior to supplying it to said disdillation column. 11. The process as claimed in claim 9, wherein further comprises expanding said first liquid portion, directing said expanded first liquid  portion for heat exchange with said condensed stream and is then directing it to said column at a mid-column feed position. 12. The process as claimed in claims 1, 2 or 7, wherein further comprises heating at least a portion of said vapor stream after being expanded to said lower pressure. 13. The process as claimed in any claims 3 to 6, wherein further comprises heating at least a portion of said second stream after being expanded to said lower pressure. 14. The process as claimed in claims 1, 4 or 7, wherein further comprises heating at least a portion of said expanded condensed stream prior to supplying it to a distillation column. 15. The process as claimed in claims 2 or 5, wherein further comprises expanding at least a portion of said condensed stream to said lower pressure, heating of said expanded stream and then supplying it to said distillation column at a second mid-column feed position. 16. The process as claimed in claims 1 or 7, wherein further comprises combining at least portions of said expanded vapor stream and said expanded condensed stream to form a second combined stream and then supplying it to said column at a mid-column feed position. 17. The process as claimed in claim 2, wherein further comprises expanding at least a portion of said condensed stream to said lower pressure and combining it with at least a portion of said expanded vapor stream to form a second combined stream and then supplying it to said column at a mid-column feed position. 18. The process as claimed in claim 4, wherein further comprises combining at least portions of said expanded second stream and said expanded condensed stream to form a second combined stream and then supplying it to said column at a mid-column feed position. 19. The process as claimed in claim 5, wherein further comprises expanding at least a portion of said condensed stream to said lower pressure and combining it with at least a portion of said expanded second stream to form a second combined stream and then supplying it to said column at a mid-column feed position. 20. The process as claimed in claims 1 or 7, wherein further comprises cooling of said condensed stream and then dividing it to a first and second liquid portions prior to said expanding, expanding the first liquid portion to said lower pressure and then supplying it to said column at a mid-column feed position, expanding the second liquid portion to said lower pressure and combining it with at least a portion of said expanded vapor stream to form a second combined stream and supplying it to said column at a higher mid-column feed position. 21. The process as claimed in claim 20, wherein further comprises heating said expanded first liquid portion prior to being supplied to the distillation column. 22. The process as claimed in claim 20, wherein further comprises expanding said first liquid portion, directing said expanded stream for heat exchage with said condensed stream and then supplying it to said column at a mid-column feed position. 23. The process as claimed in claim 4, wherein further comprises cooling said condensed stream and then dividing it to a first and second liquid portions to said expanding, expanding of the first liquid portion to said lower pressure and then supplying it to said column at a mid-column feed position, expanding the second liquid portion to said lower pressure and combining it with at least said expanded second stream to form the second combined stream and supplying it to said column at a higher mid-column feed position. 24. The process as claimed in claim 23, wherein further comprises heating said expanded first liquid portion prior to being supplied to the distillation column. 25. The process as claimed in claim 23, wherein further comprises expandimg said first liquid portion, directing it for heat exchange with said condensed stream and then supplying it to said column at a mid-column feed position. 26. The process as claimed in any preceding claim 1 to 25, wherein further comprises dividing said heated distillation stream to said volatile resudue gas fraction and a recycled stream prior to compression and thereafter compressing said recycled stream. 27. The process as claimed in any preceding claim 1 to 25, wherein further comprises dividing said heated distillation stream to said volatile resudue gas fraction and a recycled stream prior to heating and thereafter compressed to form said compressed recycle stream. 28. An apparatus for the separation of a gas stream, containing methane, C2 components, C3 components and heavier hydrocarbon components, wherein the apparatus enables to separate gas stream by a process as claim