Method and device for separating fractions of a mixture

1. A method for separating fractions of a mixture to be separated, in a device ( 1 ) having:

several chromatography columns ( 21 , 22 , 23 , etc.) mounted in series,

a single separation zone constituted by a constantly open separation loop comprising, at the inlet of the open separation loop an eluent-injection point ( 6 ) for injecting eluent into one of the columns and, at the outlet of the open separation loop, a draw-off point ( 8 ) for withdrawal of a fraction of the mixture, with no other fluid circulating between the inlet and the outlet of the open separation loop, the method comprising:

a mixture injection stage for discontinuous injection of the mixture to be separated into the open separation loop ( 4 ),

a collection stage for collection of at least two fractions, and

a shifting stage for shifting by at least one column the eluent-injection point ( 6 ) and the fraction draw-off point ( 8 ) of the separation loop ( 4 ),

wherein

(a) during the shifting stage, the eluent-injection and draw-off points of the separation loop are shifted at different times, or

(b) said device further comprises at least one other loop, or

(c) in which the eluent-injection and draw-off points of the separation loop are not contiguous.

2. The method according to claim 1 , in which the mixture injection stage is carried out independently of the collection and shifting stages.

3. The method according to claim 1 , in which the mixture is injected at the inlet of a column which is different from the column where the eluent is injected.

4. The method according to claim 1 , in which the mixture is injected into the separation loop, at a point distant from the eluent-injection and collection points of at least one column.

5. The method according to claim 1 , in which the shifting of the eluent-injection and collection points is carried out in the direction of flow of the mixture to be separated in the columns.

6. The method according to claim 1 , in which at least two fractions are collected successively at the collection point of the separation loop.

7. The method according to claim 1 , wherein the device comprising two columns in series,

the inlet of the separation loop being at the inlet of one of the columns and

the outlet of the separation loop being at the outlet of the other column, the collection stage comprising the collection of two fractions at the draw-off point at the outlet of the separation loop, one of the fractions, the extract, being more retained in the columns than the other fraction, the raffinate, which is less retained in the columns.

8. The method according to claim 1 , in which, during the shifting stage, the eluent-injection and draw-off points of the separation loop are shifted at different times.

9. The method according to claim 8 , in which, during the shifting stage,

the eluent-injection point of the separation loop is shifted by at least one column towards the draw-off point of the separation loop, in the direction of flow of the mixture to be separated in the columns, at least one column remaining between the injection point and the draw-off point.

10. The method according to claim 9 , in which, during the shifting stage,

the draw-off point of the separation loop is shifted in the direction of flow of the mixture to be separated in the columns, by as many columns as the number by which the eluent-injection point of the separation loop has been shifted.

11. The method according to claim 9 , the device also comprising:

at least one other loop, every other loop being open and comprising at the inlet another eluent-injection point and at the outlet another collection point, the method comprising, after shifting the eluent-injection point of the separation loop by at least one column,

the shifting by at least one column of the draw-off point of one of the other loops.

12. The method according to claim 11 , in which each loop is eluted with eluents of a different kind or of different compositions.

13. The method according to claim 9 , in which, after the shifting of the eluent-injection point of the separation loop by at least one column,

at least one other loop appears with at least one shifted column, every other loop having appeared being open and comprising at the inlet another injection point and at the outlet another draw-off point.

14. The method according to claim 8 , in which each loop other than the separation loop ( 4 ) ensures the desorption of the most-retained fractions of mixture in the columns or the regeneration of the columns.

15. The method according to claim 1 , in which, during the shifting stage,

the eluent-injection and draw-off points of the separation loop are shifted simultaneously.

16. The method according to claim 15 , wherein

said device comprises at least one other loop, every other loop being open and comprising at the inlet another eluent-injection point and at the outlet another draw-off point, and

the collection stage also comprising collection at the draw-off point of every other loop.

17. The method according to claim 16 , in which each loop is eluted with eluents of a different kind or of different compositions.

18. The method according to claim 16 , in which, during the shifting stage of the eluent-injection and collection points of the separation loop,

the other eluent-injection and collection points of every other loop are shifted simultaneously with the eluent-injection and collection points of the separation loop.

19. The method according to claim 1 , in which the eluent-injection and draw-off points of the separation loop are contiguous.

20. The method according to claim 1 , in which the eluent-injection and draw-off points of the separation loop are not contiguous.

21. The method according to claim 20 , in which the eluent-injection and draw-off points are separated by at least one other separation loop.

22. The method according to claim 1 , in which the injection is only carried out during certain periods.

23. The method according to claim 1 , the method being cyclical.

24. The method according to claim 1 according to which the eluent used is a single-phase fluid constituted by at least one gaseous product at ambient pressure and temperature.

25. The method according to claim 1 according to which the eluent used is a fluid containing at least carbon dioxide in the supercritical state.

26. The method according to claim 1 according to which the eluent used is a homogeneous fluid containing at least carbon dioxide.

27. The method according to claim 1 , in which the eluent is recycled by means chosen from the group consisting of distillation, evaporation and the use of membranes.

28. The method according to claim 1 , wherein said device further comprises at least one desorption loop comprising, at the inlet of the desorption loop, an injection point ( 46 ) for injection of eluent into a column of the desorption loop, and, at the outlet of the desorption loop, a draw-off point ( 48 ) for withdrawing a fraction of the mixture, and

wherein said method further comprises shifting by at least one column the eluent injection point ( 46 ) and the fraction draw-off point ( 48 ) of said at least one desorption loop,

wherein the eluents at the inlet of the separation loop and the inlet of said at least one desorption loop have different compositions.

29. A method for separating fractions of a mixture to be separated, in a device ( 1 ) having:

several chromatography columns ( 21 , 22 , 23 , etc.) mounted in series,

a single separation zone constituted by a constantly open separation loop comprising, at the inlet of the open separation loop an eluent-injection point ( 6 ) for injecting eluent into one of the columns and, at the outlet of the open separation loop, a draw-off point ( 8 ) for withdrawal of a fraction of the mixture, the method comprising:

a mixture injection stage for discontinuous injection of the mixture to be separated into the open separation loop ( 4 ),

a collection stage for collection of at least two fractions, and

a shifting stage for shifting by at least one column the eluent-injection point ( 6 ) and the fraction draw-off point ( 8 ) of the separation loop ( 4 );

wherein said device further comprises at least one desorption loop comprising, at the inlet of the desorption loop, an injection point ( 46 ) for injection of eluent into a column of the desorption loop, and, at the outlet of the desorption loop, a draw-off point ( 48 ) for withdrawing a fraction of the mixture, and

wherein the eluents at the inlet of the separation loop and the inlet of said at least one desorption loop have different compositions.

30. A method for separating fractions of a mixture to be separated, in a device ( 1 ) having:

several chromatography columns ( 21 , 22 , 23 , etc.) mounted in series,

a single separation zone constituted by a constantly open separation loop comprising, at the inlet of the open separation loop an eluent-injection point ( 6 ) for injecting eluent that is recycled by chosen from the group consisting of distillation, evaporation and the use of membranes into one of the columns and, at the outlet of the open separation loop, a draw-off point ( 8 ) for withdrawal of a fraction of the mixture, the method comprising:

a mixture injection stage for discontinuous injection of the mixture to be separated into the open separation loop ( 4 ),

a collection stage for collection of at least two fractions,

a shifting stage for shifting by at least one column the eluent-injection point ( 6 ) and the fraction draw-off point ( 8 ) of the separation loop ( 4 ).