Centrifugal separator having a forcing device to create a radial leak flow

Abstract

A centrifugal separator includes a frame and a rotating part including a spindle and a centrifuge rotor enclosing a separation space. An inlet channel provides fluid communication into the separation space and includes a rotary channel part, a frame channel part, and a first seal at the interface between the rotary and frame channel parts. An outlet channel provides fluid communication out from the separation space and includes a rotary channel part, a frame channel part, and a second seal at the interface between the rotary and frame channel parts. The inlet and outlet channels are arranged concentrically with each other. A forcing device is provided to generate a leak flow through one of the first and second seals in a first direction from the outlet channel to the inlet channel and to counteract leakage in the opposite direction.

Claims

1. A centrifugal separator comprising: a frame, a rotating part comprising a spindle and a centrifuge rotor enclosing a separation space, the rotating part being supported by the frame to rotate around an axis of rotation, a drive member configured to rotate the rotating part, an inlet channel configured to provide fluid communication into the separation space and comprising a first rotary channel part attached to the centrifuge rotor, the first rotary channel part having an inner surface and an outer surface, a first frame channel part attached to the frame, the first frame channel part having an inner surface and an outer surface, and a first seal provided at the interface between the first rotary channel part of the inlet channel and the first frame channel part of the inlet channel, the first seal contacting the outer surface of the first rotary part and the outer surface of the first frame channel part, and at least one outlet channel configured to provide fluid communication out from the separation space and comprising a second rotary channel part attached to the centrifuge rotor, the second rotary channel part having an inner surface and an outer surface, a second frame channel part attached to the frame, the second frame channel part having an inner surface and an outer surface, and a second seal provided at the interface between the second rotary channel part of the outlet channel and the second frame channel part of the outlet channel, the second seal contacting the outer surface of the second rotary part and the outer surface of the second frame channel part, wherein: the inlet channel and the outlet channel are arranged adjacent to and concentrically with each other, and a forcing device is provided to generate a leak flow through one of the first and second seals in a first direction from the outlet channel to the inlet channel.

2. The centrifugal separator according to claim 1, wherein the inlet channel is configured to feed a product to be separated into the separation space and the outlet channel is configured to discharge a separated primary phase of the product from the separation space, and wherein the forcing device is provided to generate said leak flow from the outlet channel to the inlet channel and thus to counteract, or prevent, leakage from the inlet channel to the outlet channel.

3. The centrifugal separator according to claim 1, wherein at least said one of the first and second seals comprises a rotary seal surface on the respective rotary channel part and a frame seal surface on the respective frame channel part, and wherein the rotary seal surface and the frame seal surface are arranged opposite to each other.

4. The centrifugal separator according to claim 3, wherein the rotary seal surface and the frame seal surface both extend in parallel with a radial plane with respect to the axis of rotation.

5. The centrifugal separator according to claim 3, wherein the forcing device comprises a plurality of at least partly non-radial pumping elements on at least one of the rotary seal surface and the frame seal surface.

6. The centrifugal separator according to claim 5, wherein the pumping elements have a curved shape seen in the direction of the axis of rotation.

7. The centrifugal separator according to claim 1, wherein the forcing device comprises a pump wheel provided to operate on the outlet channel and arranged to force the fluid communication through the outlet channel, and thus to generate said leak flow.

8. The centrifugal separator according to claim 7, wherein the pump wheel is located upstream of said one of the first and second seals.

9. The centrifugal separator according to claim 1, wherein the spindle comprises the first rotary channel part of the inlet channel and the second rotary channel part of the outlet channel.

10. The centrifugal separator according to claim 1, wherein the drive member comprises an electrical motor having a rotor and a stator, and wherein the rotor is fixedly connected to the rotating part.

11. The centrifugal separator according to claim 1, wherein the outlet channel is provided within the inlet channel.

12. The centrifugal separator according to claim 1, wherein the inlet channel is provided within the outlet channel.

13. The centrifugal separator according to claim 1, wherein the centrifugal separator comprises a further outlet channel configured to provide fluid communication out from the separation space and comprising a third rotary channel part attached to the centrifuge rotor, a third frame channel part attached to the frame, and a third seal provided at the interface between the third rotary channel part and the third frame channel part.

14. The centrifugal separator according to claim 13, wherein the further outlet channel is configured to discharge a separated secondary phase of the product from the separation space, and wherein the forcing device is provided to generate a leak flow through the first seal of the inlet channel from the further outlet channel into the inlet channel and thus to counteract, or prevent, leakage from the inlet channel into the further outlet channel.

15. The centrifugal separator according to claim 13, wherein the outlet channel is provided within the inlet channel, wherein the inlet channel is provided within the further outlet channel at least at the interface between the first rotary channel part of the inlet channel and the first frame channel part of the inlet channel, and wherein the forcing device is provided to generate a leak flow through the first seal of the inlet channel from the further outlet channel into the inlet channel and thus to counteract, or prevent, leakage from the inlet channel into the further outlet channel.

16. A centrifugal separator according to claim 2, wherein at least said one of the first and second seals comprises a rotary seal surface on the respective rotary channel part and a frame seal surface on the respective frame channel part, and wherein the rotary seal surface and the frame seal surface are arranged opposite to each other.

17. The centrifugal separator according to claim 4, wherein the forcing device comprises a plurality of at least partly non-radial pumping elements on at least one of the rotary seal surface and the frame seal surface.

18. A centrifugal separator comprising: a frame; a spindle and a centrifuge rotor enclosing a separation space, the spindle being supported by the frame to rotate around an axis of rotation; a fluid channel having concentric channels comprising: an inlet channel comprising a first rotary channel part and a first frame channel part; a first seal provided at the interface between the first rotary channel part and the first frame channel part; an outlet channel comprising a second rotary channel part and a second frame channel part; and a second seal provided at the interface between the second rotary channel part and the second frame channel part of the outlet channel, wherein the first seal is within the outlet channel and contacts an outer surface of the first frame channel part, and a forcing device provided to generate a leak flow through the first seal in a radial direction from the outlet channel to the inlet channel.

19. The centrifugal separator according to claim 18, wherein the second seal contacts an outer surface of the second frame channel part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be explained more closely by means of a description of various embodiments and with reference to the drawings attached hereto.

(2) FIG. 1 discloses a centrifugal separator according to a first embodiment of the invention.

(3) FIG. 2 discloses a longitudinal section of sealing means of the centrifugal separator in FIG. 1.

(4) FIG. 3 discloses a view along the line III-III in FIG. 2.

(5) FIG. 4 discloses a longitudinal section of a variant of sealing means of the centrifugal separator in FIG. 1.

(6) FIG. 5 discloses a centrifugal separator according to a second embodiment of the invention.

(7) FIG. 6 discloses sealing means of the centrifugal separator in FIG. 5.

(8) FIG. 7 discloses a centrifugal separator according to a third embodiment of the invention.

(9) FIG. 8 discloses sealing means of the centrifugal separator in FIG. 7.

(10) FIG. 9 discloses a view along the line IX-IX in FIG. 8.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

(11) FIG. 1 discloses a centrifugal separator according to a first embodiment comprising a frame 1 and a rotating part 2. The rotating part 2 is rotatably supported by the frame 1 to rotate around an axis x of rotation by means of suitable bearing means, for instance in the form of one or more bearings. In the first embodiment the bearing means comprises a first bearing 3a, and a second bearing 3b. The first and second bearings 3a, 3b may comprise roller bearings or ball bearings. The first bearing 3a may be elastically mounted to the frame 1 via a first resilient member 4a having suitable elastic and damping properties. Also the second bearing 3b may be elastically mounted to the frame 1 via a second resilient member 4b having suitable elastic and damping properties.

(12) The frame 1 may be stationary, at least with respect to the rotating part 2. For instance, the frame 1 may be located or mounted on the ground, possibly via an intermediate fundament that may be provided with damping means or configured to provide a damping function of vibrations or other movements of the centrifugal separator. The frame 1 comprises or carries a casing 5.

(13) The rotating part 2 comprises a spindle 6 and a centrifuge rotor 7 attached to the spindle 6. The centrifuge rotor 7 is enclosed by the casing 5. The centrifuge rotor 7 encloses or defines a separation space 8. The centrifuge rotor 7 also comprises a plurality or a large number of separation discs 9 provided in separation space 8. In the embodiments disclosed, the separation discs 9 are conical. However, as an alternative radial or even axial separation discs may be comprised by the centrifuge rotor 7. The centrifugal separator of the embodiments disclosed is of a so called hermetic type with a closed separation space 8.

(14) The centrifugal separator also comprises a drive member 10 for rotating the rotating part 2. The drive member 10 comprises, in the embodiments disclosed, an electric motor directly attached to the spindle 6. The electric motor comprises a rotor 11, which is attached to and extends around the spindle 6, and a stator 12, which is attached to the frame 1. Alternatively, the drive member 10 may be provided beside the spindle 6 and rotate the rotating part 2 via a suitable transmission, such as a belt or a gear transmission.

(15) In the embodiments disclosed, the first bearing 3a and the second bearing 3b are attached to the spindle 6 and provided on a respective side of the drive member 10. The first bearing 3a is provided on the spindle 6 between the drive member 10 and the centrifuge rotor 7, whereas the second bearing 3b is provided on the spindle 6 on the other side of the drive member 10 turned away from the centrifuge rotor 7.

(16) The centrifugal separator comprises an inlet channel 20, an outlet channel 30 and a further outlet channel 40.

(17) The inlet channel 20 is configured to provide fluid communication into the separation space 8 and to feed a product to be separated into the separation space 8. The inlet channel 20 comprises a rotary channel part 21 having an inner and outer surface, the rotary channel part attached to the centrifuge rotor 7, a frame channel part 22 having an inner and outer surface, the frame channel part attached to the frame 1, and sealing means 23 provided at the interface between the rotary channel part 21 of the inlet channel 20, and the frame channel part 22 of the inlet channel 20. The sealing means 23 contacts the outer surface of the rotary channel part 21 and frame channel part 22.

(18) The outlet channel 30 is configured to provide fluid communication out from the separation space 8 and to discharge a separated primary phase of the product from the separation space 8. The outlet channel 30 comprises a rotary channel part 31 having an inner and outer surface, the rotary channel part attached to the centrifuge rotor 7, a frame channel part 32 having an inner and outer surface, the frame channel part attached to the frame 1, and sealing means 33 provided at the interface between the rotary channel part 31 of the outlet channel 30, and the frame channel part 32 of the outlet channel 30. The sealing means 33 contacts the outer surface of the rotary channel part 31 and frame channel part 32.

(19) The further outlet channel 40 is configured to provide fluid communication out from the separation space 8 and to discharge a separated secondary phase of the product from the separation space 8. The further outlet channel 40 comprises a rotary channel part 41 attached to the centrifuge rotor 7, a frame channel part 42 attached to the frame 1, and sealing means 43 provided at the interface between the rotary channel part 41 of the further outlet channel 40, and the frame channel part 42 of the further outlet channel 40.

(20) In addition, the centrifugal separator may comprises a plurality of outlet openings, not disclosed in the figures, provided at the outer periphery of the centrifuge rotor 7 for discharge of a sludge or another further product from the separation space 8. The openings may be permanently open or intermittently openable by means of a valve mechanism as known in the prior art.

(21) Furthermore, each of the separation discs 9 may be provided with one or more feed holes 9a through which the product entering the separation space 8 may be fed into the package of separation discs 9 and distributed onto the separation discs 9.

(22) In the embodiment disclosed in FIG. 1, the primary phase of the product is a relatively light phase whereas the secondary phase of the product is a relatively heavy phase. Furthermore, the primary phase is the minor phase whereas the secondary phase is the main phase. These conditions may of course be the opposite in various variants of the first embodiment disclosed.

(23) The inlet channel 20 and the outlet channel 30 are arranged adjacent to and concentrically with each other. In the first embodiment, the outlet channel 30 is provided within the inlet channel 20. It is of course possible, as an alternative solution, to provide the inlet channel 20 within the outlet channel 30.

(24) The centrifugal separator also comprises forcing means provided to generate a leak flow through one of the sealing means, in the first embodiment the sealing means 33 of the outlet channel 30, in a first direction from the outlet channel 30 to the inlet channel 20, and thus to counteract or prevent leakage in the opposite direction from the inlet channel 20 to the outlet channel 30. As the inlet channel 20 and outlet channel are concentrically arranged, leak flow through the sealing means 33 is in the radial direction.

(25) The sealing means 23, 33 and 43 comprise a respective rotary seal element 25, 35 and 45 attached to the respective rotary channel part 21, 31 and 41, and provided with a respective rotary seal surface 26, 36 and 46, see also FIGS. 2-4. The sealing means 23, 33 and 43 also comprise and a respective frame seal element 27, 37 and 47 attached to the respective frame channel part 22, 32 and 42 and provided with a respective frame seal surface 28, 38 and 48. The rotary seal surfaces 26, 36 and 46 are arranged opposite to the respective frame seal surface 28, 38 and 48. The rotary seal surfaces 26, 36 and 46 and the frame seal surfaces 28, 38, 48 are all plane and extend in parallel with a radial plane p with respect to the axis x of rotation. The rotary seal surfaces 26, 36 and 46 may be arranged to abut the respective frame seal surface 28, 38 and 48 for the rotary seal surface 26, as indicated in FIGS. 2 and 4, and frame seal surface 28, and for the rotary seal surface 36 and frame seal surface 36, as indicated in FIG. 2. These abutting seal surfaces form a so called mechanical seal.

(26) However, it is also possible to arrange the rotary seal surfaces 26, 36 and 46 at a small distance to the respective frame seal surface 28, 38 and 48, leaving a gap, or a thin gap, therebetween as indicated in FIG. 2 for the rotary seal surface 36 and the frame seal surface 38. Such a gap will permit the leak flow mentioned above.

(27) In the first embodiment, the forcing means comprises a plurality of at least partly non-radial pumping elements 60 on at least one of the rotary seal surface 26, 36 and 46 and the frame seal surface 28, 38 and 48. In the embodiment disclosed in FIGS. 1-4, the pumping elements 60 are provided on the rotary seal surface 36 of the rotary channel part 30 of the outlet channel 30. It is to be understood, that the pumping elements 60 alternatively may be provided on the frame seal surface 28, 38, 48, or possibly on both the rotary seal surface 26, 36, 46 and the frame seal surface 28, 38, 48.

(28) In FIGS. 2 and 3, the pumping elements 60 are configured as blades projecting from the rotary seal surface 36. In FIG. 2 the pumping elements 60 are configured in such a way that the blades do not abut the opposite frame seal surface 38. However, it is to be understood that it is possible to let the pumping elements 60 extend so that the blades will abut the opposite frame seal surface 38.

(29) As can be seen in FIG. 3, the pumping elements 60 extend in a non-radial direction. More precisely, the pumping elements 60 extend outwardly and rearwardly with respect to the rotary direction r of the rotary seal surface 60 seen in the direction of the axis x of rotation.

(30) As also illustrated in FIG. 3, the pumping elements 60 have a curved shape seen in the direction of the axis x of rotation. It is to be noted that the pumping elements 60 instead may have a straight non-radial extension seen in the direction of the axis x of rotation.

(31) In the first embodiment, eight such pumping elements 60 are provided. It is to be noted that the number of pumping elements 60 may be less or more than eight, for instance 2-7 or 9 or more.

(32) In FIG. 4, the pumping elements 60 are, instead of comprising blades, configured as or comprising grooves formed in the rotary seal surface 36. In this variant of the pumping elements 60, the grooves may advantageously extend beyond the inner and outer side surfaces of the rotary seal element 35. Furthermore, the rotary seal surface 36 may, but does not have to, abut the frame seal surface 38 as illustrated in EP-B-37210.

(33) FIG. 5 discloses a second embodiment of the centrifugal separator, which differs from the first embodiment in that the forcing means comprises a pump wheel 70 provided in or at the outlet channel 30. The pump wheel 70 is and arranged to promote the fluid communication from the separation space 8, and thus to force the fluid, i.e. the separated primary phase, through the outlet channel 30. In such a way the leak flow through the sealing means 33 of the outlet channel 30 will be generated. The pump wheel 70 is located upstream the sealing means 33 of the outlet channel 30.

(34) In the second embodiment, the pump wheel 70 is driven by a turbine wheel 71 via a drive shaft 72. The turbine wheel 71 is provided in the inlet channel 20 and driven by the fluid flow of the product fed through the inlet channel 20 into the separation space. However, as an alternative to the turbine wheel 71, the pump wheel 70 may be driven by an electrical motor via the drive shaft 72, or via a magnetic coupling, whereby the electrical motor may be provided inside or outside the rotating part 2.

(35) In the second embodiment it may be dispensed with the pumping elements 60. The pumping effect of the pump wheel 70 may be sufficient to force a small part, i.e. the leak flow, of the primary phase through the sealing means 33. However, it is to be noted that the pump wheel 70 may be combined with pumping elements 60.

(36) In the second embodiment, the rotary seal surface 36 and frame seal surface 38 of the outlet channel 30 are provided at a small distance from each other, i.e. with a gap therebetween, in order to permit the above mentioned leak flow therethrough.

(37) FIGS. 7 to 9 disclose a third embodiment of the centrifugal separator, which differs from the one in the first embodiment in that the inlet channel 20 is provided within the further outlet channel 40 along the rotary channel part 21 of the inlet channel 20 and along a substantial part of the frame channel part 21 of the inlet channel 20. The outlet channel 30 is provided within the inlet channel 20 as in the first and second embodiments. Similar to the embodiment of FIG. 2, each channel has a rotary channel part having an inner and outer surface and a frame channel part having an inner and outer surface.

(38) The forcing means are provided to generate a leak flow through the sealing means 23 of the inlet channel 20 from the further outlet channel 40 into the inlet channel 20, thereby preventing leakage from the inlet channel 20 into the further outlet channel 40, and to generate a leak flow through the sealing means 33 of the outlet channel 30 into the inlet channel 20, thereby preventing leakage in the from the inlet channel 20 to the outlet channel 30. Each sealing means contacts an outer surface of the rotary channel part 31 and frame channel part 32.

(39) In the third embodiment, the forcing means comprises pumping elements 60 in the form of blades provided on the rotary seal surface 26 of the inlet channel 26 and the rotary seal surface 36 of the outlet channel 30. The blades on the rotary seal surface 26 and/or the rotary seal surface 36 may of course be replaced by grooves as disclosed in FIG. 4. The blades and/or grooves have the same configuration as the blades disclosed in FIGS. 2 to 4. Also in this case it is possibly to provide the pumping elements 60 on the frame seal surface 28 and/or the frame seal surface 38.

(40) A fourth embodiment of the centrifugal separator differs from the one of the third embodiment in that the pumping elements 60 of the inlet channel 20 on the rotary seal surfaces 26 and/or the pumping elements 60 of the outlet channel 30 on the rotary seal surface 36 have been replaced by a pump wheel 70 of the second embodiment disclosed in FIG. 5. The seal surfaces 26, 28 and/or 36, 38 are arranged at a distance from each to permit the leak flow therethrough.

(41) The present invention is not limited to the embodiments disclosed and described above, but may be varied and modified within the scope of the following claims.