Centrifugal separator with sludge space plates

Abstract

A centrifugal separator for separating a fluid mixture into components includes a rotor which forms within itself a separation space delimited by a rotor wall, and includes a set of separation plates defining separation passages there between. An inlet is arranged for supply of a fluid mixture to be separated and a first outlet is arranged for a separated lighter first component of the fluid mixture. A sludge space is being defined as an annular portion of the separation space radially outside the separation plates. A second outlet is arranged for discharge of a separated denser second component of the fluid mixture extending from the radially outer portion of the sludge space. A plurality of sludge space plates, which sludge space plates are separate components from the separation plates, is arranged in the sludge space, extending outwardly and in an annular direction with respect to the rotational axis, while forming a gap between the sludge space plates and the rotor wall.

Claims

1. A centrifugal separator for separating a fluid mixture into components, comprising: a frame; a rotor which is rotatably supported in the frame around a rotational axis, which rotor forms within itself a separation space delimited by a rotor wall, and comprising a set of separation plates defining separation passages there between; an inlet extending into the rotor for supply of a fluid mixture to be separated in the separation space; a first outlet for a separated lighter first component of the fluid mixture extending from a radially inner portion of the separation space; a sludge space being defined as an annular portion of the separation space radially outside the separation plates; a second outlet for a separated denser second component of the fluid mixture extending from the radially outer portion of the sludge space; and a plurality of sludge space plates arranged in the sludge space and connected by connecting plates arranged in an axial direction, an inner edge of the sludge space plates being radially spaced from an outer edge of the separation plates, the sludge space plates extending perpendicular to the rotational axis and disposed perpendicular to the connecting plates, wherein the plurality of sludge space plates are spaced from one another in an axial direction with respect to the rotational axis, wherein the sludge space plates are separate components from the separation plates, and wherein a gap is formed between the sludge space plates and the rotor wall.

2. The centrifugal separator according to claim 1, wherein the sludge space plates are in the form of spaced annular discs enclosing the separation plates.

3. The centrifugal separator according to claim 1, wherein the radial extent of the sludge space plates is varied to provide the gap between the sludge space plates and the rotor wall, and wherein the gap between the sludge space plates and the rotor wall is at least 3 mm.

4. The centrifugal separator according to claim 1, wherein the space between the outer edge of the separation plates and the inner edge of the sludge space plates is at least 3 mm.

5. The centrifugal separator according to claim 1, wherein the sludge space plates are arranged at a mutual distance which is larger than the distance between the separation plates defining separation passages there between, which mutual distance of the sludge space plates is in the range of 2-40 mm.

6. The centrifugal separator according to claim 1, wherein the number of sludge space plates is in the range of 5-30.

7. The centrifugal separator according to claim 1, wherein the sludge space plates are connected to form a unit by said connecting plates.

8. The centrifugal separator according to claim 1, wherein the plurality of separation plates is a stack of frustoconical discs.

9. The centrifugal separator according to claim 8, wherein the frustoconical discs are provided with a number of openings distributed around the periphery of each disc to form passages extending through the stack.

10. The centrifugal separator according to claim 1, wherein the sludge space plates are arranged at a mutual distance which is larger than the distance between the separation plates defining separation passages there between, which mutual distance of the sludge space plates is in the range of 5-20 mm.

11. The centrifugal separator according to claim 1, wherein the sludge space plates are arranged at a mutual distance which is larger than the distance between the separation plates defining separation passages there between, which mutual distance of the sludge space plates is about 10 mm.

12. The centrifugal separator according to claim 1, wherein the number of sludge space plates is in the range of 10-20.

13. A centrifugal separator for separating a fluid mixture into components, comprising: a frame; a rotor which is rotatably supported in the frame around a rotational axis, which rotor forms within itself a separation space delimited by a rotor wall, and comprising a set of separation plates defining separation passages there between; an inlet extending into the rotor for supply of a fluid mixture to be separated in the separation space; a first outlet for a separated lighter first component of the fluid mixture extending from a radially inner portion of the separation space; a sludge space being defined as an annular portion of the separation space radially outside the separation plates; a second outlet for a separated denser second component of the fluid mixture extending from the radially outer portion of the sludge space; and a plurality of sludge space plates arranged in the sludge space and connected by connecting plates arranged in an axial direction, an inner edge of the sludge space plates being radially spaced from an outer edge of the separation plates, the sludge space plates being planar and disposed perpendicular to the connecting plates, wherein the plurality of sludge space plates are spaced from one another in an axial direction with respect to the rotational axis, wherein the sludge space plates are separate components from the separation plates, and wherein a gap is formed between the sludge space plates and the rotor wall.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention is now described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a cross-section of a centrifugal separator having a set of sludge space plates.

(3) FIG. 2 shows a cross-section of a rotor of a centrifugal separator having a set of sludge space plates.

DESCRIPTION OF EMBODIMENTS

(4) FIG. 1 shows a centrifugal separator 1 for separating a fluid mixture into components, such as for separating water and particles from an oil based fluid mixture. The separator has a frame 2 supporting a centrifugal rotor 3 around a rotational axis x by means of a spindle 20 connected to the frame by a first and a second bearing. The rotor is driven by a motor, such as an electric direct drive motor 21 as illustrated. The rotor forms within itself a separation space 4, delimited by a rotor wall 5, wherein a set of separation plates 6 in the form of a stack of frustoconical separation discs is arranged. The separation discs forms separation passages 7 between each pair of adjacent discs. A stationary inlet 8 extends into the rotor for supply of a fluid mixture to be separated to the separation space. A first outlet 9 for a separated lighter first component of the fluid mixture extends from a radially inner portion of the separation space. A sludge space 10 is defined as an annular portion of the separation space radially outside the separation plates, and a second outlet 11 for discharge of a separated denser second component of the fluid mixture extends from the radially outer portion of the sludge space.

(5) The rotor 3 is now further described with reference to FIG. 2. The rotor forms within itself a separation space 4, delimited by a rotor wall 5, wherein a set of separation plates 6 in the form of a stack of frustoconical separation discs is arranged. The separation discs forms separation passages 7 between each pair of adjacent discs. Each separation disc is provided with a number of openings or cut-outs 17 distributed around the periphery of each disc to form passages 18 extending through the stack in an axial direction to distribute the flow of fluid to be separated through and over the disc stack. The rotor further comprises a distributor 16 delimiting a central inlet space 23 in the rotor, which is connected to the separation space 4 via passages in the rotor. The distributor supports the stack of separation discs. A stationary inlet 8 extends into the inlet space for supply of a fluid mixture to be separated. A first outlet 9 for a separated lighter first component of the fluid mixture extends from a radially inner portion of the separation space 4. A sludge space 10 is defined as an annular portion of the separation space radially outside the separation discs. A plurality of second outlets 11 distributed around the circumference of the rotor extend from the radially outer portion of the sludge space for discharge of a separated denser second component of the fluid mixture, denoted sludge. The opening of the second outlets 11 is controlled by an operating slide 24 arranged to be displaced from the closed position in short periods of time for discharge of the sludge collected in the sludge space, as known in the art.

(6) In the sludge space 10 a plurality of sludge space plates 12 in the form of annular sludge space discs is arranged, enclosing the separation plates and extending perpendicularly outwardly with respect to the rotational axis x, as seen in FIG. 2. The sludge space discs extend in a direction perpendicular to the axial direction. Unlike the separation plates, which are frustoconical, the sludge space discs are planar and extend in only the radial direction. The sludge space discs are separate components from the separation plates. The sludge space discs are configured such that a gap 13, 13′ is formed between the sludge space discs and the rotor wall. The gap is provided to enable sludge collected between the sludge space plates to flow towards the second outlets during discharge of sludge. The gap is formed between the sludge space discs and the conical rotor wall since the radial extent of the sludge space discs is varied between the discs to adapt their extent to the conical shape of the rotor wall. The size of the gap may be varied to fit the properties of the sludge to be separated from the fluid, but it should preferably be above 3 mm, and typically 5-10 mm.

(7) The sludge space discs 12 are provided at a mutual distance 15 from one another. In the example shown the distance between the sludge space discs is constant over the stack of sludge space discs. The number of sludge space plates is preferably in the range of 10-20, depending on the size of the rotor. The distance between the sludge space discs is several times larger than the distance between the separation discs forming the separation passages. The distance between the sludge space discs may be varied to fit the properties of the sludge to be separated from the fluid, but it should preferably be in the range of 2-40 mm, more preferably in the range of 5-20 mm, such as of about 10 mm.

(8) The sludge space discs 12 are further arranged such that gap 14 is formed between the separation discs and the sludge space discs. The gap between the separation discs and the sludge space discs is preferably at least 3 mm. Since the separation plates are in the form of frustoconical discs provided with cut-outs in the form of slits to distribute the flow of fluid to be separated through and over the disc stack, which slits are cut-outs that are open towards the outer radius of the separation disc, the gap may be provided to reduce pressure drop over the disc stack. If cut-outs are provided in the form of holes that are closed towards the outer radius of the separation disc the gap between the separation discs and the sludge space discs may be minimised.

(9) The sludge space plates are connected to form a unit by a plurality of connecting plates 19, as seen in the detailed view of FIG. 3, arranged in an axial direction and evenly distributed around the rotational axis. Typically the connecting plates are arranged in a plane including the rotational axis x and extend from a radially inner position outside the separation discs to a radially outer position in the region of the rotor wall, thus extending in a radial direction whereby the sludge space plates 12 are disposed perpendicular to the connecting plates 19. Thus the connecting plates divide the annular sludge space into sectors of similar size, acting to minimise flow and turbulence in the tangential direction in the sludge space. The connecting plates may extend to the rotor wall, at least to form contact points to support the unit. The connecting plates may further be configured such that to provide a gap 13/13′ between the connecting plates and the rotor wall, and wherein the gap between the connecting plates and the rotor wall preferably is at least 3 mm. Thus sludge collected between the sludge space plates may more easily flow towards the second outlets during discharge of sludge and to facilitate cleaning of the sludge space. The unit of sludge space plates and connecting plates may be supported by the connecting plates coupling to the radially outer portion of the stack of separation discs 6 and/or by the radially outer portion of the distributor 16.

(10) During operation, the rotor 3 is rotated at an operational speed, a fluid mixture to be separated into components is introduced into the inlet space 23 of the rotor by the inlet 8. The fluid is transported to the separation space via passages in the rotor, by means of centrifugal forces. The flow of fluid is then distributed over the stack of separation discs 6 via the axial passages 18 provided by the cut-outs 17 in the discs, and into the separation passages 7 between adjacent separation discs. In the separation passages denser and lighter components of the fluid mixture are separated. Lighter components of the fluid (e.g. oil) are transported radially inwardly towards the first outlet 9 for a separated lighter first component of the fluid mixture, which first outlet extends from a radially inner portion of the separation space. From the first outlet chamber fluid may be peeled by a peeling device as known in the art. Denser components of the fluid (such as water and solid particulate matter, i.e. sludge) are transported radially outwardly in the separation space towards the sludge space 10. The denser components pass between the sludge space plates and collect at the radially outer portion of the sludge space, inside the second outlets 11.

(11) The sludge space discs arranged in the sludge space tend to reduce currents, turbulence or flow in directions along the rotational axis of the sludge space. Such currents having an axial flow component may have the undesired effect to bring along particles already separated from a liquid mixture of components. Thereby the risk of particles (solid and/or fluid) separated in the separation passages being brought along by such flow and reintroduced in another separation passage is reduced. The sludge space discs thus tend to increase the separation efficiency of the separator.

(12) To empty the sludge space from sludge, discharge is initiated by displacing the operating slide 24 to open the second outlets 11. Sludge collected in the sludge space is then discharged through the second outlets by means of centrifugal force. Sludge collected in the passages between adjacent sludge space plates is displaced outwardly, into the gap 13/13′ between the sludge space plates and the rotor wall and out through the second outlets. The outlets are then closed by moving the operating slide to the closed position.

(13) In an embodiment not shown the centrifugal separator as previously described further comprises a third outlet for a third component, denser than the first component, extending from the radially inner portion of the sludge space. This denser third component of the fluid mixture may be a denser liquid component, such as water. A top disc is provided at the upper end of the stack of separation discs. The top disc delimits a passage between the top disc and the rotor wall for a denser third component separated from the fluid mixture extending from the radially inner portion of the sludge space, connected to the third outlet. The top disc is configured to extend radially outside the frustoconical plates, and the sludge space plates extend radially inside an outer portion of the top disc. In this embodiment the unit of sludge space plates and connecting plates may be supported by the top disc. Among the denser components separated from the fluid mixture, the least dense components, such as water, flow over the radially outer edge of the top disc towards the third outlet. From third outlet chamber fluid may be peeled by a peeling device as known in the art.