Patent Grant
12128427
The present invention relates to a method of controlling a centrifugal separator. The present invention further relates to a centrifugal separator.
WO 2011/093784 discloses a centrifugal system wherein PID controllers are utilised for controlling various parameters such as recirculation flow and backpressure. A separator bowl of a centrifugal separator is also disclosed. Inside the separator bowl a liquid mixture is separated into a heavy component and a light component. The separator bowl is provided with outlet pipes for the heavy component. The outlet pipes follow an interior wall of the separator bowl and extend upwardly towards, and connect to, a heavy component outlet channel.
GB 853733 discloses a centrifuge apparatus for separating liquid material into heavy, light and intermediate fractions. Liquid material is supplied to a separator rotor. Heavy fraction is discharged through nozzles. The light fraction passes through liner plates, which herein are referred to as discs, inside the rotor and is discharged by a skimming device. The intermediate fraction passes from outside the liner plates through tubes and passages. The heavy fraction is partly recircuit via a return passage into the rotor. A valve controls the discharge of intermediate fraction. Moreover, water may be added to the rotor via the return passage for further controlling the flow of intermediate fraction.
A centrifugal separator comprises a separator rotor delimiting a separation space. As exemplified in the above-mentioned documents, such a centrifugal separator may comprise at least one tube extending from a radially outer portion of the separation space towards a central portion of the separation space. A separated heavy phase is conducted via the at least one tube out of the separator rotor. The provision of the at least one tube provides for the heavy phase to be transported out of the separator rotor in a gentle manner, compared to if the heavy phase is ejected from a periphery of the separator rotor. The gentle treatment may be advantageous e.g. when the heavy phase comprises living matter, such as e.g. yeast, or other cells. Gentle treatment may also be advantageous when separating active substances for the manufacturing of pharmaceutical drugs.
Depending on the number of tubes, and/or the internal diameter of the tubes, and/or the properties of the heavy phase, there may be one or more problems with a separator comprising the above discussed at least one tube. The heavy phase may block one or more of the tubes. Only part of the heavy phase may leave the separator rotor via the tubes. Some of the heavy phase may instead remain in some sectors of the radially outer portion of the separation space, such as in a sector where a tube is blocked, or in a sector where there is no tube.
It is an object to remedy, or at least alleviate, at least some of the above-mentioned problems. It would be advantageous to provide a method of controlling a centrifugal separator such that a heavy phase flows reliably out of a separator rotor of the centrifugal separator via at least one tube. Accordingly, there is provided a method as defined in an appended independent method claim related to a method of controlling a centrifugal separator. Further, it would be advantageous to provide a centrifugal separator devised such that a heavy phase flows reliably out of a separator rotor of the centrifugal separator via at least one tube. Accordingly, there is provided a centrifugal separator as defined in an appended independent claim related to a centrifugal separator.
According to an aspect, there is provided a method of controlling a centrifugal separator. The centrifugal separator comprises a separator rotor delimiting a separation space, a stack of frustoconical separation discs arranged inside the separation space, a drive arrangement configured to rotate the separator rotor about a rotation axis at a rotational speed, an inlet for a liquid mixture, a first outlet for a light liquid phase arranged in fluid communication with a central portion of the separation space, a second outlet for a heavy phase, and at least one tube extending from at least one radially outer portion of the separation space towards a central portion of the separator rotor. The at least one tube has an outer end arranged at the at least one radially outer portion and an inner end arranged towards the central portion of the separator rotor. The second outlet is arranged in fluid communication with the inner end of the at least one tube. The method comprises steps of:
Since, the rotational speed of the separator rotor is changed from the first rotational speed to the second rotational speed, such that a heavy phase accumulation at the periphery of the separation space is displaced in a circumferential direction, it may be ensured that the heavy phase accumulation at the periphery is displaced towards the outer end of the at least one tube. Thus, the heavy phase accumulated within the separation space at circumferential positions where there is no tube, is displaced such that the heavy phase is able to flow out of the separation space via the at least one tube. As a result, the above-mentioned object is achieved.
According to a further aspect, there is provided a centrifugal separator comprising: a separator rotor delimiting a separation space, a stack of frustoconical separation discs arranged inside the separation space, a drive arrangement configured to rotate the separator rotor about a rotation axis at a rotational speed, an inlet for a liquid mixture, a first outlet for a light liquid phase arranged in fluid communication with a central portion of the separation space, a second outlet for a heavy phase, at least one tube extending from at least one radially outer portion of the separation space towards a central portion of the separator rotor, and a controller configured to control the drive arrangement. The at least one tube has an outer end arranged at the at least one radially outer portion and an inner end arranged towards the central portion of the separator rotor. The second outlet is arranged in fluid communication with the inner end of the at least one tube. The controller is configured to control the drive arrangement to rotate the separator rotor at a first rotational speed and at a second rotational speed, and the controller is configured to change the rotational speed of the separator rotor from the first rotational speed to the second rotational speed.
Since the controller is configured to control the drive arrangement to rotate the separator rotor at the first rotational speed and at the second rotational speed, and the controller is configured to change the rotational speed of the separator rotor from the first rotational speed to the second rotational speed, it may be ensured that the centrifugal separator is configured to displace a heavy phase accumulation at the periphery of the separation space in a circumferential direction towards the outer end of the at least one tube. Thus, the heavy phase accumulated within the separation space at circumferential positions where there is no tube, is displaced such that it is able to flow out of the separation space via the at least one tube. As a result, the above-mentioned object is achieved.
The centrifugal separator may also be referred to as a disc stack centrifugal separator. The centrifugal separator may be a high speed separator, i.e. a centrifugal separator wherein the separator rotor is rotated at one or more thousands of revolutions per minute (rpm). The separator rotor may also be referred to as a separator bowl.
The first and second rotational speeds are rotational speeds exceeding 0 rpm. The first and second rotational speeds may e.g. exceed 1000 rpm. The first rotational speed differs from the second rotational speed.
The first rotational speed may be higher than the second rotational speed. Thus, the change in rotational speed may be a reduction in rotational speed of the separator rotor. Alternatively, the first rotational speed may be lower than the second rotational speed. Thus, the change in rotational speed may be an increase in rotational speed of the separator rotor. In both instances, the change in rotational speed may bring about the displacement of the heavy phase accumulation at the periphery of the separation space.
The change of the rotational speed of the separator rotor from the first rotational speed to the second rotational speed brings about a rotational speed difference between the heavy phase accumulation and the separator rotor. Due to this rotational speed difference, the displacement of the heavy phase accumulation in the circumferential direction at a periphery of the separation space is achieved.
The provision of the at least one tube provides for the heavy phase to be transported out of the separator rotor in a gentle manner, compared to if the heavy phase is ejected from a periphery of the separator rotor. The gentle treatment may be advantageous e.g. when the heavy phase comprises living matter, such as e.g. yeast, or other cells. Gentle treatment may also be advantageous when separating active substances for the manufacturing of pharmaceutical drugs.
The periphery of the separation space refers to the outward bounds of the separation space, as opposed to the central and middle portions of the separation space. One or more inner surfaces of the separator rotor limit the separation space at the periphery of the separation space. The at least one at least one radially outer portion of the separation space is arranged at the periphery of the separation space.
During separation of the liquid mixture into the light liquid phase and the heavy phase, the heavy phase is collected in a circumferential portion of the separation space, at the periphery of the separation space, and forms a heavy phase accumulation. The circumferential portion extends in a circumferential direction of the separator rotor, and may thus form an imaginary ring or torus inside the separation space.
Due to the displacement in the circumferential direction of the heavy phase accumulation by the change of the rotational speed of the separator rotor from the first rotational speed to the second rotational speed, the heavy phase accumulation does not form a static mass. Namely, while the centrifugal separator is in operation, part of the heavy phase in the heavy phase accumulation leaves the separation space via the at least one tube, and new heavy phase is added to the heavy phase accumulation as heavy phase is separated from the liquid mixture.
According to embodiments, the method may comprise a step of:
According to embodiments, the method may comprise a step of:
The step of periodically repeating the step of changing the rotational speed of the separator rotor from the first rotational speed to the second rotational speed may be performed in various ways. For instance, a timeframe for each repetition of periodically repeating the step of changing the rotational speed may have one and the same length for each repetition. Alternatively, a timeframe for each repetition of periodically repeating the step of changing the rotational speed may differ between at least some of the repetitions, for instance within the below discussed timeframes.
According to embodiments, the step of changing the rotational speed of the separator rotor from the first rotational speed to the second rotational speed may be performed within a timeframe of 1-60 seconds, or within a timeframe of 1-30 seconds, or within a timeframe of 1-20 seconds, or within a timeframe of 3-15 seconds. In this manner, the change in rotational speed may be performed within a timeframe causing displacement of the heavy phase accumulation in a circumferential direction at the periphery of the separation space.
According to embodiments, a rotational speed difference between the first rotational speed and the second rotational speed may be at least 50 rpm, or at least 100 rpm. In this manner, the magnitude of the rotational speed change may be suited to cause displacement of the heavy phase accumulation in a circumferential direction at the periphery of the separation space.
According to embodiments, the step of rotating the separator rotor at a first rotational speed may comprise a step of:
According to embodiments, the centrifugal separator may comprise a braking arrangement arranged separate from the drive arrangement, and configured to brake the rotational speed of the separator rotor. The step of changing the rotational speed of the separator rotor from the first rotational speed to a second rotational speed may comprise a step of:
According to embodiments, the first rotational speed, and/or the second rotational speed, may provide centrifugal separation at 1000 G or more. In this manner, an efficient separation of the liquid mixture into the light liquid phase and the heavy phase may be provided.
According to embodiments, the separator rotor may comprise one or more outlet openings at a radially outer periphery of the separator rotor, the outlet openings connecting a radially outer periphery of the separation space with an ambient environment of the separator rotor. The method may comprise a step of:
According to embodiments, the at least one tube may have an inner diameter within a range of 1.5-10 mm. In this manner, a suitable flow speed of the heavy phase may be achieved in the at least one tube. Thus, the at least one tube may not block up.
According to embodiments, the method may comprise a step of:
According to embodiments, the controller may be configured to periodically change the rotational speed of the separator rotor from the first rotational speed to the second rotational speed. In this manner, the heavy phase accumulation at the periphery of the separation space is intermittently displaced in a circumferential direction towards the outer end of the at least one tube. Thus, the heavy phase may be continuously lead out of the separation space via the at least one tube.
According to embodiments, an inner surface of the separator rotor may be provided with one or more steps along a circumferential direction of the separator rotor. In this manner, part of the heavy phase accumulation at the periphery of the separation space is collected between the steps. Thus, the rotational speed change of the separator rotor from the first rotational speed to the second rotational speed may be efficiently transferred to the heavy phase accumulation, and bring about an efficient displacement of the heavy phase accumulation along the periphery of the separation space in a circumferential direction.
According to embodiments, an inner circumferential surface portion of the separator rotor may form a volute extending in a circumferential direction of the separator rotor from a first circumferential position to a second circumferential position, and wherein the outer end of the at least one tube is arranged in the second circumferential position. In this manner, the inner peripheral surface of the separator rotor leans towards the at least one tube. Thus, the displacement of the heavy phase accumulation in a circumferential direction at the periphery of the separation space by the rotational speed change is enforced by the volute.
Further features and advantages will become apparent when studying the appended claims and the following detailed description.
Various aspects and/or embodiments including particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:
Aspects and/or embodiments will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.
In these embodiments, the drive arrangement 5 forms part of the spindle 4. That is, the rotor arrangement 2 is directly driven by the drive arrangement 5. The drive arrangement 5 comprises an electric motor and a rotor of the electric motor forms part of the spindle 4. In alternative embodiments, the drive arrangement may instead be connected to the spindle. Such alternative embodiments may comprise an electric motor connected to the spindle, e.g. via cog wheels, or a belt drive.
The separator rotor 11 delimits a separation space 6 therein. Inside the separation space 6, continuous centrifugal separation of a liquid mixture takes place during operation of the centrifugal separator 1. Inside the separation space 6 there is arranged a stack of frustoconical separation discs 7. The separation discs 7 provide for an efficient separation of the liquid mixture into at least a light phase and a heavy phase. The light phase may be a light liquid phase. The stack of frustoconical separation discs 7 is fitted centrally and coaxially with the rotation axis (X), and rotates together with the separator rotor 11.
The centrifugal separator 1 may be configured for separating the liquid mixture into at least the light phase and the heavy phase. The liquid mixture may comprise e.g. one liquid, or two liquids. The liquid mixture may comprise solid matter, which may be separated from the liquid mixture as part of the heavy phase.
The centrifugal separator 1 comprises an inlet 8 for the liquid mixture, a first outlet 9 for the light phase, and a second outlet 10 for the heavy phase. In the illustrated embodiments, the liquid mixture to be separated is fed from the top of the centrifugal separator 1 via the inlet 8 centrally down into the separator rotor 11, from which it is distributed in to the separation space 6. During use of the centrifugal separator 1, the separated light phase is lead upwardly to the first outlet 9 from a central portion of the separator space 6. That is, the first outlet 9 is arranged in fluid communication with the central portion of the separation space 6. From a central portion of the separator rotor 11, the heavy phase is lead upwardly to the second outlet 10. How the heavy phase is directed from the radially outer periphery of separation space 6 to the central portion of the separator rotor 11 is discussed in more detail with reference to
The present invention is not limited to any particular types of liquid mixtures or separated fluid phases. Neither is the present invention limited to any particular inlet arrangement for the liquid mixture, nor to any particular first outlet 9 for the separated light phase.
The centrifugal separator 1 further comprises a controller 12 configured to control the drive arrangement 5. More specifically, the controller 12 is configured to control the electric motor of the drive arrangement 5. Such controllers are known and may operate e.g. by controlling the voltage, the current, or the frequency of the electric current supplied to the electric motor, inter alia depending on the type of electric motor. Therefore, the controller 12 will not be discussed in further detail herein.
The controller 12 is configured to control the drive arrangement 5 to rotate the separator rotor 11 at a first rotational speed and at a second rotational speed. The controller 12 may be configured to control the drive arrangement 5 in further ways. For instance, the controller 12 may be configured to start and stop the drive arrangement 5. The controller 12 may be configured to control the drive arrangement 5 to rotate the separator rotor 11 at further rotational speeds, such as at a third rotational speed.
The controller 12 is configured to control the drive arrangement 5 to accelerate the separator rotor 11 to a fixed rotational speed. Further, the controller 12 is configured to control the drive arrangement 5 at one or more fixed rotational speeds, at least for a limited time period. The fixed rotational speed or speeds may correspond to the first rotational speed and/or to the second rotational speed.
According to some embodiments, the controller 12 may be configured to dynamically brake the electric motor of the drive arrangement 5, i.e. convert the electric motor to a generator in order to brake the separator rotor 11. Thus, the controller 12 may actively brake the first rotational speed to the second rotational speed, or vice versa.
According to some embodiments, the centrifugal separator 1 may comprise a braking arrangement 14, 14′ arranged separate from the drive arrangement 5, and configured to brake the rotational speed of the separator rotor 11. In such embodiments, the controller 12 may be configured to control the braking arrangement 14, 14′. The controller 12 may be configured to brake the rotational speed of the separator rotor 11 from the first rotational speed to the second rotational speed with the braking arrangement 14, 14′, or vice versa.
In
The first exemplified braking arrangement 14 comprises a ventilated disc brake. The disc of the disc brake is connected to the spindle 4. When a braking force is applied to the brake disc via brake pads, the rotational speed of the spindle 4 and the separator rotor 11 is braked, for instance from a first rotational speed to a second rotational speed.
The second braking arrangement 14′ comprises a water inlet into a rotor space 16 of the housing 3. In order to brake the rotational speed of the separator rotor 11, water is flushed in sufficient amounts onto the separator rotor 11 inside the rotor space 16. The separator rotor 11 may be provided with one or more fins 18 for enhancing the braking efficiency of the water flushed onto the rotor 11.
While the braking arrangement 14, 14′ is braking the separator rotor 11, the drive arrangement 5 may be switched off. Alternatively, the drive arrangement 5 may assist in the braking of the separator rotor 11 by switch to a braking mode, such as e.g. dynamic braking. When the braking arrangement 14, 14′ is utilised for braking the separator rotor 11, e.g. from the first rotational speed to the second rotational speed, the drive arrangement 5 may be controlled to stabilise the rotational speed of the separator rotor 11 at the second rotational speed.
Again, the separator rotor 11 is configured to be rotated around a rotation axis (X) and delimits a separation space 6 with a stack of frustoconical separation discs 7.
In these embodiments, the liquid mixture is lead into the separation space 6 from a lower side of the separator rotor 11. Channels 20 for conducting the liquid mixture into the separation space 6 are schematically illustrated in
At least one tube 26, 26′ extends from at least one radially outer portion 28, 28′ of the separation space 6 towards the central portion of the separator rotor 11. The at least one tube 26, 26′ has an outer end 30, 30′ arranged at the at least one radially outer portion 28, 28′ and an inner end 32, 32′ arranged towards the central portion of the separator rotor 11 and the second conduit 24. Thus, the second outlet of the centrifugal separator is arranged in fluid communication with the inner end 32, 32′ of the at least one tube 26, 26′. The at least one radially outer portion 28, 28′ is arranged at at least one peripheral portion of the separation space 6.
In these embodiments, the separator rotor 11 comprises two tubes 26, 26′. In alternative embodiments, the separator rotor 11 may comprise only one tube, or more than two tubes, such as e.g. four tubes, seven tubes, ten tubes, or twelve tubes. In the following description reference will be made to only one tube 26. However, the discussion applies to any other tube of the same kind.
During separation of the liquid mixture, the separated heavy phase is collected at the peripheral portion of the separation space 6. The separated heavy phase forms a heavy phase accumulation at a periphery of the separation space 6. Via the tube 26, heavy phase from the heavy phase accumulation is conducted to the central portion of the separator rotor 11. Accordingly, the separated heavy phase is in viscous form, such that it can flow through the tube 26. A pressure difference between the radially inner end 32 of the tube 26 and the radially outer end 30 of the tube 26 promotes the flow of the heavy phase from the peripheral portion of the separation space 6 towards the central portion of the separator rotor 11. The flow of the heavy phase in the tube 26 is indicated with arrows in
The tube 26 may have an inner diameter within a range of 2-10 mm. The inner diameter may be selected depending on the number of tubes 26 and on the amount and viscosity of the heavy phase. A suitable flow speed of the heavy phase in the tube 26 to prevent blockage of the at least one tube 26, 26′ is pursued. Mentioned as an example, a flow speed of about 2 m/s may be suitable for some types of heavy phase.
Optionally, the separator rotor 11 may comprise one or more outlet openings 34, 34′ at a radially outer periphery of the separator rotor 11. The outlet openings 34, 34′ connect a radially outer periphery of the separation space 6 with an ambient environment of the separator rotor 11. The outlet openings 34, 34′ may be intermittently opened. A discharge slide 36, also referred to as sliding bowl bottom, may be utilised in a known manner for opening and closing the outlet openings 34, 34′.
Inside the separator rotor 11 an insert 42 is arranged. The insert 42 is arranged radially outside the stack of separation discs 7. The at least one tube 26, 26′ is secured inside the separator rotor 11 in the insert 42. An inner surface of the insert 42 forms part of an inner surface 44 of the separator rotor 11. A similar insert 42 is discussed in further detail below with reference to
Accordingly, a controller is configured to control the rotational speed of the centrifugal separator between a first rotational speed and a second rotational speed. The change in rotational speed between the first and second rotational speeds is performed in such a manner that the heavy phase accumulation at the periphery of the separation space is displaced in a circumferential direction of the separator rotor 11. Accordingly, the change in rotational speed is sudden, i.e. the change in rotational speed is performed over a limited time period. The controller of the centrifugal separator may be configured to perform one or more steps of the method 100, discussed below with reference to
In the diagrams of
During operation of the centrifugal separator in accordance with the embodiments of
Operation of the centrifugal separator in accordance with the embodiments of
During operation of the centrifugal separator in accordance with
Operation of the centrifugal separator in accordance with the embodiments of
More specifically, after the rotational speed has been changed from the first rotational speed to the second rotational speed, and after the first to third time periods, a-c, have passed, the rotational speed of the separator rotor is changed to a third rotational speed, 3rd, over a fourth time period, d. The third rotational speed, 3rd, may be higher than the second rotational speed, 2nd, as indicated with the full line. Alternatively, the third rotational speed, 3rd, may be lower than the second rotational speed, 2nd, as indicated with the broken line. After a fifth time period, e, the rotational speed of the separator rotor is increased to the first rotational speed, 1st. This change may be done directly to the first rotational speed, 1st, as indicated with the full and broken lines. Alternatively, the increase to the first rotational speed may be performed via a further time period, f, during which the rotational speed is maintained at a different rotational speed, e.g. the second rotational speed, 2nd, before reaching the first rotational speed, 1st, as indicated with the dash-dotted line. According to alternative embodiments, the rotational speed changes of the separator rotor may include more than three different rotational speed levels.
Thus, with reference to
Suitably, the controller 12 is configured to change the rotational speed of the separator rotor 11 from the second rotational speed back to the first rotational speed. Thus, the rotational speed of the separator rotor 11 may again be changed to the second rotational speed for repeated displacement of the heavy phase accumulation.
The controller 12 may be configured to periodically change the rotational speed of the separator rotor 11 from the first rotational speed to the second rotational speed. Accordingly, the controller 12 may also be configured to periodically change the rotational speed of the separator rotor 11 back from the second rotational speed to the first rotational speed. Thus, an intermittent displacement of the heavy phase accumulation at the periphery of the separation space 6 towards the outer end of the at least one tube 26, 26′ may be achieved.
Mentioned purely as examples, changing the rotational speed of the separator rotor 11 from the first rotational speed to the second rotational speed may be performed within a timeframe of 1-60 seconds, or within a timeframe of 1-30 seconds, or within a timeframe of 1-20 seconds, or within a timeframe of 3-15 seconds. The rotational speed difference between the first rotational speed and the second rotational speed may be at least 50 rpm, or at least 100 rpm.
More specific examples, with reference to
The controller 12 may further be configured for changing control parameters of the centrifugal separator 1. For instance, the controller 12 may be configured for controlling at least one of:
In this manner, control parameters of the centrifugal separator may be changed in order to affect e.g. the displacement of the heavy phase accumulation at the periphery of the separation space 6, and/or the flow of the heavy phase through the at least one tube 26, 26′.
The centrifugal separator 1 may be provided with one or more sensors 13 for sensing and/or measuring a parameter of the liquid mixture, and/or of the heavy phase, se
In embodiments of the centrifugal separator 1 comprising the one or more outlet openings 34, 34′ at a radially outer periphery of the separator rotor 11, the controller 12 may be configured for controlling the discharge slide 36 for intermittently opening the outlet openings 34, 34′.
In
In
Thus, the displacement of the heavy phase accumulation at the periphery of the separation space in a circumferential direction is achieved as the rotational speed changes between the first and second rotational speeds.
Due to the displacement of the heavy phase accumulation at the periphery of the separation space, the heavy phase does not settle in one or more circumferential positions, where it could compact to such an extent that it cannot be transported through the at least one tube. Due to the displacement of the heavy phase accumulation at the periphery of the separation space, the heavy phase in viscous form, is moved towards the at least one tube and transported through the at least one tube. Repeated rotational speed changes as discussed herein, ensure that the displacement is repeated, and thus, the heavy phase does not settle in one or more circumferential positions.
Again, the main purpose of the insert 42 is to secure the at least one tube (not shown) inside the separator rotor. In these embodiments, the insert 42 is configured for securing two tubes. The two tubes are each secured in a slot 43, 43′ at the outer surface of the insert 42. The slots 43, 43′ open up towards the inside of the insert 42, via holes 45, 45′. Thus, the outer radial ends of the tubes are arranged in fluid communication with the periphery of the separation space of the separator rotor. Namely, at least part of the separation space within the separator rotor is formed within the insert 42.
The insert 42 provides at least part of an inner surface 44 of the separator rotor, which inner surface 44 is provided with one or more steps 46, 46′ along a circumferential direction of the separator rotor. In these embodiments, the steps 46, 46′ are provided at two axial positions of the insert 42, i.e. at two positions along a direction of the rotation axis of the separator rotor. A first set of steps 46 is arranged at an axial position of the holes 45′. A second set of steps 46′ is arranged axial displace from the holes 45′. Alternatively, only one of the sets of steps 46, 46′ may be provided in the insert 42.
The steps 46, 46′ increase the engagement between the heavy phase accumulation and the separator rotor at the periphery of the separation space, at least in comparison with an even inner surface of the separator rotor. Thus, the steps 46, 46′ assist in the displacement of the heavy phase accumulation at the periphery of the separation space as the rotational speed of the separator rotor changes.
The steps 46, 46′ may be steeper in one circumferential direction than in the other circumferential direction. The steeper faces of the steps 46, 46′ will engage better with the heavy phase accumulation than the less steeper faces. Thus, the effect of the rotational speed change may be increased in one circumferential direction towards the holes 45, 45′ and the tubes arranged therein.
A portion of the inner circumferential surface 44 of the separator rotor may form a volute. The volute extending in a circumferential direction of the separator rotor from a first circumferential position 48 to a second circumferential position 50. The outer end of the at least one tube is arranged in the second circumferential position 50.
Herein, a direction of an extension of the volute is meant to extend from a smaller radius end of the volute towards a larger radius end of the volute. The extension of the volute is clearly visible in
Since the insert 42 is configured for supporting two tubes, the insert 42 comprises two volutes, one volute extending to each tube. The first and second circumferential positions 48′, 50′ of the second volute are indicated in
In the embodiments of
Accordingly, the centrifugal separator comprises a separator rotor delimiting a separation space, a stack of frustoconical separation discs arranged inside the separation space, a drive arrangement configured to rotate the separator rotor about a rotation axis at a rotational speed, an inlet for a liquid mixture, a first outlet for a light liquid phase arranged in fluid communication with a central portion of the separation space, a second outlet for a heavy phase, and at least one tube extending from at least one radially outer portion of the separation space towards a central portion of the separator rotor. The at least one tube has an outer end arranged at the at least one radially outer portion and an inner end arranged towards the central portion of the separator rotor. The second outlet is arranged in fluid communication with the inner end of the at least one tube.
The rotational speed of a separator rotor of the centrifugal separator 1 may be changed as discussed in connection with
The method 100 comprises steps of:
As discussed above, e.g. in connection with
The method 100 may comprise a step of:
The method 100 may comprise a step of:
The step of changing 112 the rotational speed of the separator rotor from the first rotational speed to the second rotational speed may be performed within a timeframe of 1-60 seconds, or within a timeframe of 1-30 seconds, or within a timeframe of 1-20 seconds, or within a timeframe of 3-15 seconds.
As discussed above, a rotational speed difference between the first rotational speed and the second rotational speed may be at least 50 rpm, or at least 100 rpm.
The step of rotating 102 the separator rotor at a first rotational speed may comprise a step of:
The centrifugal separator may comprise a braking arrangement arranged separate from the drive arrangement and configured to brake the rotational speed of the separator rotor, as discussed above, inter alia with reference to
The centrifugal separator suitably is a high speed centrifugal separator. Accordingly, the first rotational speed, and/or the second rotational speed, may provide centrifugal separation at 1000 G or more.
The separator rotor may comprise one or more outlet openings at a radially outer periphery of the separator rotor, the outlet openings connecting a radially outer periphery of the separation space with an ambient environment of the separator rotor, as discussed above, inter alia with reference to
In order to influence the flow of heavy phase through the at least one tube, one or more separator control parameters may be changed based on at least one parameter of the liquid mixture and/or at least one parameter of the heavy phase. Accordingly, the method 100 may comprise a step of:
The at least one parameter of the liquid mixture and/or of the heavy phase may be e.g. temperature, viscosity, and/or solid matter content.
It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the invention, as defined by the appended claims. For instance, the controller 12 may be a distributed controller system, i.e. comprising more than one processing unit for controlling different aspects of the centrifugal separator, the rotational speed of the separator rotor 11, measurements being made, the intermittent opening of outlet openings, activating of a braking arrangement 14, 14′, etc.
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| PCT/EP2020/052847 | 2/5/2020 | WO |
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| WO2020/169343 | 8/27/2020 | WO | A |
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| 20220134358 A1 | May 2022 | US |
