The present invention relates to a centrifugal separator, in particular, a decanter centrifuge, for separating two phases of liquid of different density. The centrifugal separator includes a body configured to rotate in use in a direction of rotation around a horizontal axis of rotation. The axis of rotation extends in a longitudinal direction of the rotating body. A radial direction extends perpendicular to the longitudinal direction. The body includes a bowl. The bowl defines a base provided at a rear longitudinal end of the bowl. The base defines a first rear longitudinal area of the centrifugal separator rear of the base. At least two outlet passages extend through the base. The outlet passages communicating with respective weir edges at respective levels. The weir edges define a level of liquid in the bowl and a level of an interface between the two phases of liquid in the bowl during use of the centrifugal separator. A first of the outlet passages extend axially to a first outlet opening for discharging liquid from the rotating body in the first rear longitudinal area during use of the centrifugal separator. A second of the outlet passages includes a conduit extending to a second outlet opening discharging liquid from the rotating body in a second rear longitudinal area rear of said first rear longitudinal area during use of the centrifugal separator. The second outlet opening is positioned to have a distal edge relative to the axis of rotation placed at a level not above the level of the weir edge communicating with the second outlet opening.
FR-A-2 120 537 discloses a centrifuge of the prior art.
EP-A-1 480 754 discloses an centrifugal separator in which the base comprises an inner annular space receiving in use a light phase of liquid that has passed the weir of the first outlet passage, from which annular space the liquid, in one embodiment (
WO-A-2009/127212, enclosed herein by reference, discloses a centrifugal separator having a base with two outlet passages for a light and a heavy phase of liquid, respectively, whereby one outlet passage extends axially through the base whereas the other outlet passage extends, via an outlet chamber inside the base, radially out of the base to a nozzle directing the out-flowing liquid in a direction opposite the direction of rotation.
It is an object of the present invention to provide a centrifugal separator of the art mentioned by way of introduction, in which both the heavy and the light phase is discharged from the rotating body at a relatively small radius or distance from the axis of rotation in order to reduce the energy consumption of the centrifugal separator.
It should be understood that the expression “level” refers to the radial distance from the axis of rotation, and by analogy to the field of gravity of earth “up” refers to a direction towards the axis of rotation and “down” refers to an opposite direction.
According to aspects disclosed herein there is provided centrifugal separators having a shaft part of a body configured to rotate about an axis of rotating the shaft part extends coaxially with the axis of rotation from a base. The shaft part carries a flange. A conduit extends from the base and through the flange to a second outlet opening. The flange separates the first and the second rear longitudinal area. The flange facilitates preventing re-mixing of the two phases after discharge from the respective outlet openings, and the flange may assist supporting the conduit.
Further according to the invention the centrifugal separator comprises a casing housing the body. The casing comprises a proximal compartment for receiving a liquid discharged from the body though the first outlet opening. The casing includes a distal compartment for receiving liquid discharged from the body through the second outlet opening. The proximal and distal compartments are separated by a partition. Thus the proximal compartment extends the first rear longitudinal area and the distal compartment extends the second rear longitudinal area. Thereby preventing the re-mixing of the two liquid phases. The casing including the partition is divided in at least two parts comprising a lid, whereby the above mentioned flange is surrounded by an annular seal and the partition engages the annular seal, at least when the lid is in a closed position, thereby preventing of re-mixing of the two liquid phases.
In one embodiment the distal edge constitutes the weir edge communicating with the second outlet opening.
In one embodiment the annular seal comprises an inner annular sealing member in sliding engagement with the flange and an outer flexible member providing for a non sliding engagement with the partition when the lid is in a closed position.
In another embodiment the annular seal comprises two semicircular parts attached to either of the two parts of the partition, the semicircular parts being securely mounted to the respective parts of the partition, to form an annular seal when the two parts of the casing and thus the two parts of the partition are brought together by bringing the lid into its closed position.
In one embodiment an outlet housing is placed in the second rear longitudinal area. The outlet housing constitutes part of the conduit. The outlet housing is rotatable around an adjustment axis, and the outlet housing includes a side wall offset from the adjustment axis. The second outlet opening is placed in the side wall. In one embodiment the conduit with the outlet housing is part of an outlet element having a connecting piece rotatably connected to the base. In a further embodiment the outlet element is tubular and has a tube axis coaxial with the adjustment axis. In one embodiment the adjustment axis is parallel with the axis of rotation. By providing an outlet opening in a side wall of such rotatable outlet housing the liquid dischargable by the outlet opening in a direction opposite the direction of rotation, thereby recovering energy from the discharged liquid. Further, when the distal edge of the outlet opening provides the weir edge of the outlet passage in question, rotating the outlet housing will adjust the level of the weir edge.
Generally for cases where a seal between a rotating member such as a flange, e.g. of a rotating body comprising a bowl of the centrifuge (e.g. a decanter centrifuge) and a sectioned partition (e.g. a casing) is required, according to the present invention an annular seal comprises an inner annular sealing member in sliding engagement with the flange and an outer flexible member providing for a non sliding engagement with the partition when the sections thereof are brought together e.g. by bringing a lid carrying a section of the partition into a closed position.
In one embodiment at least one of the weir edges extend in a plane, which is parallel with the base.
In the following the invention will be described in more detail by way of examples of embodiments with reference to the schematic drawing, in which
A rotatable body 1 of a prior art centrifugal separator or decanter centrifuge schematically shown in
For the sake of simplicity directions “up” and “down” are used herein as referring to a radial direction towards the axis 5 of rotation and away from the axis 5 of rotation, respectively.
The bowl 2 includes a base plate 6 provided at one longitudinal end of the bowl 2, which base plate 6 has an internal side 7 and an external side 8. The base plate 6 is provided with a number of liquid phase outlet passages 9 having external openings in the external side 8 of the base plate. Furthermore the bowl 2 is at an end opposite to the base plate 6 provided with solid phase discharge openings 10.
The screw conveyor 3 comprises inlet openings 11 for feeding a feed e.g. slurry to the rotatable body 1. The slurry includes a light or liquid phase 12 and a heavy or solid phase 13. During rotation of the rotatable body 1 as previously described, separation of the liquid phase 12 and solid phase 13 phases is obtained. The liquid phase 12 is discharged through the outlet passages 9 in the base plate 6, while the screw conveyor 3 transports the solid phase 13 towards the solid phase discharge openings 10 through which the solid phase 13 is eventually discharged.
With reference to
The blind end 53 provides an outlet housing 55 with a circular cylindrical side wall 57. The outlet element 51 has an axis extending in parallel to the axis of rotation 45 and constituting an adjustment axis 59 as it will be explained in more detail below. In operation the rotatable body 40 is rotating in a direction of rotation 61 as indicated in
In the embodiment shown the connecting piece 49 is substantially cylindrical like the outlet housing 55 apart from a grove accommodating an O-ring seal 69. Another O-ring seal 71 is accommodated in a recess surrounding the outlet passage 47. The outlet element 51 comprises a circumferential collar 73, which is partly accommodated in another recess surrounding the outlet passage 47. Being circular the connecting piece 49, and therewith the rest of the outlet element 51, is rotatable around the adjustment axis 59.
A screw 75 with a washer 77 is provided beside the outlet element 51 so that tightening the screw 75 urges the washer 77 against the collar 73 thereby clamping the same, whereby rotation of the outlet element 51 is prevented, the screw 75 and the washer 77 constituting an embodiment of a fastener.
Further a scale 79 is provided on the surface of the base 42 beside the recess accommodating the collar 73, and on the collar a mark 81 is provided giving an indication of the angular position of the outlet element 51, the scale 79 and the mark 81 together constituting an embodiment of an indicator.
Though only one outlet passage 47 is shown in
The outlet housing 55 works as follows:
In use the bowl 41 rotates in the direction 61 causing a feed inside the bowl 41 to separate in a heavy solid phase (not shown) and a light liquid phase having a surface at a level 83, which is slightly above the level of the weir edge 65 thereby providing a pressure head driving the liquid phase out of the bowl through the outlet element 51 and the outlet opening 63. The outlet opening 63 should be so large that during normal use of the centrifugal separator it does not run full, but a free space or an air vent between the free surface of the flowing liquid and the opposite edge 67 will be present.
The outlet element 55 is put in an angular position by rotating it around the adjustment axis 59 to bring the weir edge 65 to a desired level corresponding to a desired level 83 of the liquid inside the bowl. If the latter level need to be adjusted the level of the weir edge 65 is adjusted correspondingly by rotating the outlet element 55 around the adjustment axis 59. Due to the circular movement of the adjustment raising the weir edge 65 will at a given point entail that the opposite edge 67 is lowered to a position close to or below the level of the weir edge 65 and at that point liquid will flow over the opposite edge 67 which is not intended. Thus there is a limit to the range within which the level of the weir edge can be adjusted. The larger the angle α is, the smaller is the range within which the level of the weir edge can be adjusted while obtaining the intended function. However the smaller the angle α is the smaller is also the size of the outlet opening 63. These are factors the skilled person will take into consideration when deciding the size of the angle α.
When adjusting the angular position of the outlet element 51 care is taken that the outlet opening 63, as shown in
For adjustment of the angular position of the outlet element 51 the screw 75 is un-tightened to release the collar 73 from the clamping action of the washer 77. The outlet element is turned around the adjustment axis using the scale 79 and mark 81 to control the angle of adjustment, and the screw is tightened again to prevent unintended rotation of the outlet element 51.
Partitions of a casing, which is not shown in detail, but which corresponds to the casing shown in
Being adapted for feeds comprising two liquid phases the base 103 comprises two outlet passages provided at different angular positions relative to the axis of rotation 102.
During use the outlet housing 126 with its weir edge 129 works similar to the outlet housing 55 described with reference to
It should however be noted that the orientation of the outlet opening 128 indicates that the direction of rotation of the rotatable body in this embodiment is opposite to the direction of rotation of the rotatable body of the embodiment shown in
In use the second outlet housing 154 with its weir edge 159 works similar to the outlet housing 55 described with reference to
In one embodiment parts of a unitary element the second outlet housing 154 and the tubular conduit 162 constitute an elongate outlet housing having a first axial length and the second outlet opening 158 extends a second axial length, which is less than half the first axial length. Thereby the second outlet opening 158 is placed remote from the base 103. This provides for discharging one of the liquid phases in the second rear longitudinal area 113 next to the first rear longitudinal area 111, while discharging said liquid phase at a level close to the level of the liquid inside the bowl, which assists minimizing loss of energy. Discharging the liquid in a direction opposite the direction of rotation assists minimizing further the loss of energy or entails recovery of energy from the rotatable body of liquid in the bowl.
For adjustment of the levels 141 and 171 the first and the second outlet elements 121 and 151 are rotated around their respective adjustment axis 133 and 163 using indicators not shown to control the rotation and un-tightening fasteners not shown to allow the rotation. This is similar to the adjustment described with reference to the embodiment shown in
While in the embodiment shown in and discussed with reference to
In order to prevent re-mixing of the two liquid phases after discharge from the respective outlet openings 128 and 158 a seal is provided between the flange 107 and a partition of the casing cooperating therewith.
It should be noted that while the embodiment shown in
In this embodiment the weir plates 229a and 259a, and thus the weir edges 229 and 259, extends parallel to the base 203 and the flange 207, respectively, and further in this embodiment the base 203 and the flange 207 both extends in respective planes perpendicular to the axis of rotation 202.
In one embodiment one of the outlets of the embodiments of
The upper section 35a′ has a foot portion 173a, which has a sufficient size to receive screws 401 (only one of which is shown) for mounting a semicircular sealing element 175a.
One skilled in the relevant art will appreciate that in the embodiment of
Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.
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2010 70482 | Nov 2010 | DK | national |
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PCT/DK2011/050435 | 11/14/2011 | WO | 00 | 7/23/2013 |
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WO2012/062336 | 5/18/2012 | WO | A |
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