Device for separating into fractions a fluid comprising several fractions with double separation

1. A device for separating a flowing fluid into at least two fractions with differing mass density, comprising:

a main tube substantially in the form of a cylinder jacket and having an infeed opening and an outfeed opening located at the opposite outer end;

a first swirl element arranged in the main tube in the vicinity of the infeed opening for imparting a rotating movement to the fluid flowing through the main tube;

a first auxiliary tube placed concentrically in the main tube at a distance from the first swirl element and leading to the outfeed opening of the main tube; and

first discharge means connecting to the jacket of the main tube for discharging a heavier fraction of the fluid;

wherein:

a second swirl element placed in the first auxiliary tube in the vicinity of the infeed opening for imparting a rotating movement to the fluid flowing through the first auxiliary tube;

a second auxiliary tube placed concentrically in the first auxiliary tube at a distance from the second swirl element and leading to the outfeed opening of the main tube; and

second discharge means connecting to the jacket of the main tube for discharging a heavier fraction of the fluid,

wherein the first swirl element has an exit swirl angle greater than the effective entry swirl angle of the second swirl element.

2. The device as claimed in claim 1 , wherein the heavier fractions of the fluid substantially comprise a liquid, and a lighter fraction, which is separated from the heavier fractions and substantially comprises a gas.

3. The device as claimed in claim 1 , wherein the first auxiliary tube is placed at a distance from the outfeed opening, and that the second discharge means connect to the main tube between the first auxiliary tube and the outfeed opening.

4. The device as claimed in claim 1 , wherein a mixer is placed upstream of the first swirl element.

5. The device as claimed in claim 1 , wherein at least one support element is arranged between the first auxiliary tube and the main tube.

6. The device as claimed in claim 5 , wherein axially extending openings are arranged in the at least one support element.

7. The device as claimed in claim 5 , wherein the support element extends over a certain axial distance.

8. The device as claimed in claim 1 , wherein the first and the second discharge means comprise respectively a first and a second discharge tube, each extending downward in a direction with a vertical component.

9. The device as claimed in claim 8 , wherein the first discharge tube comprises a first T-piece which also forms part of the main tube, that the second discharge tube comprises a second T-piece also forming part of the main tube, that the first T-piece is connected to a tube part extending upstream of the T-piece and forming part of the main tube, and the first and the second T-pieces are connected by the support element.

10. The device as claimed in claim 1 , wherein at least one radially extending support element, which closes the main tube downstream, is arranged between the second auxiliary tube and the second T-piece.

11. The device as claimed in claim 1 , wherein the first and the second discharge means comprise respectively a first and a second discharge tube and wherein valves are placed in both discharge tubes for the purpose of maintaining a liquid level in at least one discharge tube, and that both valves are adjustable.

12. The device as claimed in claim 1 , wherein the first and second discharge means are connected to each other for the purpose of pressure equalization between the first and second discharge means.

13. The device as claimed in claim 12 , wherein the first and second discharge means transpose into a shared discharge provided with a single valve for the purpose of regulating a liquid level in both the first and the second discharge means.

14. The device as claimed in claim 11 , wherein at least one of the discharge means is connected above the liquid level to an auxiliary feed tube which ends in the main tube downstream of the second swirl element.

15. The device as claimed in claim 14 , wherein the auxiliary feed tube runs through the centre of the first swirl element so as to thus feed a part of the light fraction from the discharge means back to the infeed opening.

16. The device as claimed in claim 5 , wherein the passage of the openings arranged in the support element is adjustable.

17. A method for separating into fractions a fluid comprising several fractions, comprising the steps of:

placing a first swirl element in a main tube to impart a rotating movement to the fluid flowing through the main tube;

separating the fluid into a heavier fraction of the fluid located on the wall of the main tube and a centrally located lighter fraction through a first auxiliary tube extending concentrically to the main tube; and

discharging the heavier fraction laterally out of the main tube,

placing a second swirl element in the first auxiliary tube to impart a rotating movement to the lighter fraction flowing through the first auxiliary tube;

separating the lighter fraction into a heavier component of the lighter fraction located on the wall of the first auxiliary tube and a centrally located lighter component of the lighter fraction through a second auxiliary tube extending concentrically to the first auxiliary tube; and

discharging the heavier component of the lighter fraction laterally out of the first auxiliary tub;

wherein the first swirl element has an exit swirl angle greater than the effective entry swirl angle of the second swirl element.

18. The method as claimed in claim 17 , wherein the heavier component of the lighter fraction is brought together with at least a part of the heavier fraction.