Patent EA-004469-B1 (EA)
Title: Method and installation for separating a gas mixture and gases obtained by said installation
Inventor: PARADOWSKI HENRI
IPC: F25J3/02
Filed: 2001-12-13
Abstract: 1. Process for separation of a mixture cooled under pressure, containing methane and C2 and higher hydrocarbons, into a final methane-rich light fraction (1) and a final heavy fraction (2) rich in C2 and higher hydrocarbons, comprising a first stage (I) in which (Ia) said mixture cooled under pressure is separated, in a first flask (B1), into a relatively more volatile first top fraction (3) and a relatively less volatile first bottom fraction (4), in which (Ib) the first bottom fraction (4) is introduced into a middle part of a distillation column (C1), in which (Ic) in the lower part of the column, the final heavy fraction (2) rich in C2 and higher hydrocarbons is collected as the second bottom fraction (2), in which (Id) there is introduced, after pressure reduction in a turbine (T1) the first top fraction (3) in an upper part of the distillation column, in which (Ie), in the upper part of the column, a second methane-rich top fraction (5) is collected, in which (If), in order to obtain the final light fraction (1), the second top fraction (5) then undergoes compression and cooling, and in which (Ig) a first sample fraction (6) is taken from the final light fraction (1), this process comprising a second stage (II) in which (IIa) the first sample fraction (6) is introduced after cooling and liquefaction, into the upper part of the distillation column, characterized in that it comprises a third stage (III) in which (IIa) the first bottom fraction (4) is subjected to a number of sub-stages including heating, passage into a second flask (B2), and separation into a relatively more volatile third top fraction (7), and a relatively less volatile third bottom fraction (8), in which (IIIb) the third bottom fraction (8) is introduced into the middle part of the distillation column, and in which (IIIc) the third top fraction (7) is introduced, after cooling and liquefaction, into the upper part of the distillation column. 2. Process according to claim 1, characterized in that a second sample fraction (9) is removed from the first top fraction (3), and that this second sample fraction (9) is introduced into the upper part of the distillation column after cooling and liquefaction. 3. Process according to claim 2, characterized in that said second sample fraction (9) is cooled and partly condensed, then separated into a third flask (B3) into a fourth relatively more volatile top fraction (10), which is cooled and liquefied, then introduced into the upper part of the distillation column, and a fourth relatively less volatile bottom fraction (11), which is heated, then separated in a fourth flask (B4) into a fifth relatively more volatile top fraction (12) which is cooled and then introduced into the upper part of the distillation column, and a fifth relatively less volatile bottom fraction (13) which is heated and then sent into said second flask. 4. Process according to any of the preceding claims, characterized in that, in order to obtain the final light fraction (1), the second top fraction (5), after it leaves the distillation column, undergoes heating, a first compression in a first compressor (K1) coupled with a pressure reducing turbine (T1), a second compression in a second compressor (K2), and cooling. 5. Process according to claim 3, characterized in that the upper part of the distillation column comprises at least two successive stages, the first of which is the lowest, and the fifth top fraction (12) is introduced above the first stage. 6. Process according to claim 3, characterized in that the upper part of the distillation column comprises at least three successive stages, the first of which is the lowest, and the fifth [sic; fourth] top fraction (10) is introduced above the second stage. 7. Process according to claim 2, characterized in that the upper part of the distillation column comprises at least two successive stages, the first of which is the lowest, and the second sample fraction (9) is introduced above the first stage. 8. Process according to any of the preceding claims, characterized in that the upper part of the distillation column comprises at least three stages, the first of which is the lowest, in which the first sample fraction (6) is introduced in a lower part of the last stage, and in which the third top fraction (7) is introduced below the last stage. 9. Process according to any of the preceding claims, characterized in that the third top fraction (7) is introduced in the first stage of the upper part of the distillation column. 10. Process according to any of the preceding claims, characterized in that the middle part of the distillation column comprises at least two successive stages, the first of which is the lowest, and in which the third bottom fraction (8) is introduced at least into the first stage, and in that the first top fraction (3) is introduced above the first stage. 11. Methane-rich gas obtained by the process according to any of the preceding claims. 12. Liquefied gas rich in C2 and higher hydrocarbons, obtained by the process according to any of claims 1-11. 13. Installation for separation of a mixture cooled under pressure containing methane and C2 and higher hydrocarbons, into a methane-rich final light fraction (1) and a final heavy fraction (2) rich in C2 and higher hydrocarbons, comprising the means to carry out a first stage (I) in which (Ia) said mixture cooled under pressure is separated in a first flask (B1) into a relatively more volatile first top fraction (3) and a relatively less volatile first bottom fraction (4), in which (Ib) the first bottom fraction (4) is introduced into the middle part of a distillation column (C1) in which (Ic), in the lower part of the column, the final heavy fraction (2) rich in C2 and higher hydrocarbons is collected as the second bottom fraction (2), in which (Id) there is introduced, after pressure reduction in a turbine (T1), the first top fraction (3) into an upper part of the distillation column, in which (Ie) a second methane-rich top fraction (5) is collected in the upper part of the column, in which (If), in order to obtain the final light fraction (1), the second top fraction (5) undergoes compression and cooling, and in which (Ig) a first sample fraction (6) is taken from the final light fraction (1), this installation comprising the means to carry out a second stage (II) in which (IIa) the first sample fraction (6) is introduced, after cooling and liquefaction, into the upper part of the distillation column, characterized in that it comprises the means to carry out a third stage (III) in which (IIIa) the first bottom fraction (4) is subjected to a number of sub-stages, including heating, passage into a second flask (B2), and separation into a relatively more volatile third top fraction (7) and a relatively less volatile third bottom fraction (8), in which (IIIb) the third bottom fraction (8) is introduced into the middle part of the distillation column, and in which (IIIc) the third top fraction (7) is introduced into the upper part of the distillation column after cooling and liquefaction. 14. Process according to claim 13, characterized in that the lower part of the distillation column comprises a number of stages connected in pairs to one or more lateral reboilers.