Patent ID: 12194478

DETAILED DESCRIPTION

Aspects and/or embodiments of the invention 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.

FIG.1schematically illustrates embodiments of a centrifugal separation system1. The centrifugal separation system1comprises a centrifugal separator2and a control system30. The centrifugal separator2is shown in a cross-sectional view inFIG.1.

The centrifugal separator2is configured for separating a liquid feed mixture into a light phase and a heavy phase. The centrifugal separator2comprises a rotor4. The rotor4is configured to rotate about a vertical axis6of rotation and is provided with a separation space8. The centrifugal separator2further comprises an inlet10leading into the separation space8, a light phase outlet12leading from the separation space8, a heavy phase outlet14leading from the separation space8, and a stack16of frustoconical separation disks18arranged inside the separation space8.

The rotor4may be driven by a drive arrangement19to be rotated. In the illustrated embodiments, the drive arrangement19comprises a spindle20and an electric motor22. The rotor4is attached to the spindle20. The spindle20forms part of the electric motor22, i.e. the rotor4is directly driven by the electric motor22. Alternatively, the drive arrangement19may comprise a spindle connected to the rotor, an electric motor, and a transmission arranged between the electric motor and the spindle. Thus, the drive arrangement19may rotate the rotor4about the vertical axis6of rotation. The rotor4is rotatably mounted inside a housing24of the centrifugal separator2.

During separation of the liquid feed mixture in the separation space8of the rotor4, the liquid feed mixture is lead via the inlet10from the centre of the rotor4into the separation space8. The liquid feed mixture is separated into the light phase and the heavy phase. The separated light phase flows radially inwardly between the separation discs18towards the vertical axis6of rotation and out of the rotor4via the light phase outlet12. The separated heavy phase flows radially outwardly between the separation discs18towards a periphery of the separation space8and out of the rotor4via the heavy phase outlet14. Herein, each of the liquid feed mixture, the heavy phase, and the light phase are encompassed by the term process liquid.

Centrifugal separators of this kind are known and come in a number of different types and sizes. The present invention is generally applicable to different types and sizes of centrifugal separators of this kind. Unless specified, e.g. with reference to certain embodiments, the present invention is not limited to the type and arrangement of the inlet10, the light phase outlet12, and the heavy phase outlet14. The inlet10and the outlets12,14may be e.g. open, and/or mechanically hermetically sealed, and/or provided with parring discs. They may be provided at an upper end of the rotor4as illustrated inFIG.1, and/or at a lower end of the rotor4, and/or at an outer periphery of the rotor4, as illustrated e.g. inFIGS.2and3.

As mentioned above, the centrifugal separation system1comprises a control system30. The control system30comprises a control unit32, a first pressure sensor34arranged at a first radial position in the separation space8, and a second pressure sensor36arranged at a second radial position in the separation space8. The first radial position is radially outside the second radial position. The first and second pressure sensors34,36are positioned to be submerged in process liquid during operation of the centrifugal separator.

The first and second pressure sensors34,36are configured to communicate with the control unit32. For instance, pressure measurements from the first and second pressure sensors34,36may be communicated to the control unit32. The control unit32is configured to determine a parameter of the process liquid within the separation space8during operation of the centrifugal separator2based on measurements from the first and second pressure sensors34,36. As mentioned above, each of the liquid feed mixture, the heavy phase, and the light phase are encompassed by the term process liquid.

Each of the first and second pressure sensors34,36is configured to measure a pressure. The first pressure sensor34is configured to measure a pressure of the process liquid. The second pressure sensor36is configured to measure a pressure of the process liquid.

As mentioned above, the control unit32is configured to determine a parameter of the process liquid within the separation space8during operation of the centrifugal separator2based on measurements from the first and second pressure sensors34,36. The parameter may be directly or indirectly utilised during operation of the centrifugal separator2and/or during operation of the separation system1.

According to embodiments, the parameter may be a pressure difference between the first and second pressure sensors34,36. In this manner, conclusions may be drawn from the pressure difference relating to the process liquid in the separation space8. For instance, a radial position of an interface between the light and heavy phases, and/or an interface between sludge and the heavy phase may be determined.

According to embodiments, the parameter may be a density of the process liquid. In this manner, the density of the process liquid may be taken into account during operation of the centrifugal separator2and/or during operation of the separation system1comprising the centrifugal separator2. For instance, the density of the heavy phase may be taken into account when determining a radial position of the in interface between the light and heavy phases.

More specifically, the control unit32may calculate the density of the process liquid present radially between the first and second pressure sensors34,36by utilising pressure readings from the sensors34,36, with knowledge about the force acting on the process liquid, i.e. depending on the rotational speed of the rotor4, and the radial positions of the sensors34,36. For instance, the density may be calculated utilising the formula:

p⁢1-p⁢20.5*w2*(r⁢p⁢12-r⁢p⁢22)*1⁢0-1⁢0
wherein p1 and p2 are the pressures measured by the respective first and second pressure sensors34,36in bar, w is the rotor speed in rad/s, and rp1 and rp2 are the respective radial positions of the first and second pressure sensors34,36in mm.

Mentioned as an example, in order to determine the density of the heavy phase or sludge, the heavy phase or sludge may be permitted to extend radially over the first and second pressure sensors34,36. Once the density has been determined, the first and second pressure sensors may be utilised for determining a radial position of the interface between the light and heavy phases, and/or an interface between sludge and the heavy phase.

Similarly, at the beginning of a separation operation, before any substantial amounts of heavy phase or sludge have accumulated in the separation space8, the density of the light phase may be determined. Then only light phase extends radially over the first and second pressure sensors34,36and the density of the light phase may be calculated.

The centrifugal separation system1may comprise at least one flow controlling means38,40. The control unit32may be configured to control the flow controlling means38,40based on the parameter. The flow controlling means may be utilised for controlling flow of process liquid. This may be advantageous during normal operation of the centrifugal separator2, but may also, or alternatively, be utilised during a particular stage of the operation of the centrifugal separator2, such as e.g. during start-up of the centrifugal separator2and/or the separation of the liquid feed mixture. Below, nonlimiting examples of various flow controlling means are discussed.

According to embodiments, the centrifugal separation system1may comprise a heavy phase valve38arranged in the heavy phase outlet14, wherein the flow controlling means comprises the heavy phase valve38. In this manner, the control unit32may control a flow of heavy phase through the heavy phase outlet14. The heavy phase valve38may be a shut-off valve with only an open and a closed position. Alternatively, the heavy phase valve38may be a proportional valve configured to control the amount of flow there through.

According to embodiments, the centrifugal separation system1may comprise a light phase valve40arranged in the light phase outlet12, wherein the flow controlling means comprises the light phase valve40. In this manner, the control unit32may control a flow of the light phase through the light phase outlet12. The light phase valve40may be a shut-off valve with only an open and a closed position. Alternatively, the light phase valve40may be a proportional valve configured to control the amount of flow there through.

The heavy phase valve38and/or the light phase valve40may be arranged in, or at, the rotor4to rotate together with the rotor4, as indicated inFIG.1by the position of the heavy phase valve38. Alternatively, the heavy phase valve38and/or the light phase valve40may be arranged further downstream in a stationary portion of the respective outlet14,12, as indicated inFIG.1by the position of the light phase valve40.

In the embodiments ofFIG.1, the control unit32of the control system30is arranged in the rotor4. Alternatively, the control unit32may be arranged in a stationary portion of the centrifugal separator2or as part of the centrifugal separation system1outside of the centrifugal separator2as in the embodiments ofFIG.2, or the control unit may be a distributed control unit32,32′ as in the embodiments ofFIG.3.

FIG.2schematically illustrates embodiments of a centrifugal separation system1. The centrifugal separation system1resembles in much the centrifugal separation system1ofFIG.1. Accordingly, in the following mainly the differences between the embodiments will be discussed.

Again, the centrifugal separator2is configured for separating a liquid feed mixture into a light phase and a heavy phase. The centrifugal separator2comprises a rotor4, configured to rotate about a vertical axis6. The centrifugal separator2further comprises an inlet10leading into a separation space8and a light phase outlet12leading from the separation space8. A stack of separation disks18is arranged inside the separation space8.

Mentioned as an example, the mechanism44may comprise a sliding element displaceable by an actuator. The slidable element is configured to be slid between at least one open nozzle position and a position in which at least part of at least one nozzle42is covered.

Again, the centrifugal separation system1comprises a control system30which comprises a control unit32, a first pressure sensor34arranged at a first radial position in the separation space8, and a second pressure sensor36arranged at a second radial position in the separation space8.

The centrifugal separator2comprises a heavy phase outlet14leading from the separation space8. In these embodiments, the heavy phase outlet14comprises nozzles42arranged at an outer periphery of the rotor4. In this manner, a liquid feed mixture having a large heavy phase content may be separated in the centrifugal separator2. At least one of the nozzles42is always at least partially open during operation of the centrifugal separator2. Thus, the heavy phase is continuously ejected through one or more of the nozzles42during operation of the centrifugal separator2.

According to embodiments, wherein the centrifugal separator2comprises flow controlling means, the flow controlling means may comprise a mechanism44for changing a total opening area of the nozzles42. In this manner, the flow of separated heavy phase through the heavy phase outlet14may be controlled.

Accordingly, the control unit32may be configured to control the mechanism44based on the parameter. Thus, the flow of separated heavy phase through the nozzles42of the heavy phase outlet14may be controlled based on the parameter. Mentioned purely as an example, the position of an interface between the light and heavy phases in the separation space8may form a parameter to be utilised for controlling the total opening area of the nozzles42.

In the embodiments ofFIG.2, the control unit32of the control system30is arranged in a stationary portion of the centrifugal separator2or as part of the centrifugal separation system1outside of the centrifugal separator2. The pressure sensors34,36communicate wirelessly with the control unit32, either directly or via a non-shown transmitter or transceiver arranged in the rotor4. Alternatively, the control unit32of the control system30may be arranged in the rotor4, as in the embodiments ofFIG.1, or the control unit may be a distributed control unit32,32′ as in the embodiments ofFIG.3.

FIG.3schematically illustrates embodiments of a centrifugal separation system1. The centrifugal separation system1resembles in much the centrifugal separation system1ofFIGS.1and2. Accordingly, in the following mainly the differences between the embodiments will be discussed.

Again, the centrifugal separator2is configured for separating a liquid feed mixture into a light phase and a heavy phase. The centrifugal separator2comprises a rotor4, configured to rotate about a vertical axis6. The centrifugal separator2further comprises an inlet10leading into a separation space8and a light phase outlet12leading from the separation space8. A stack of separation disks18is arranged inside the separation space8.

Again, the centrifugal separator2comprises a control system30which comprises in this case at least two control units32,32′, a first pressure sensor34arranged at a first radial position in the separation space8, and a second pressure sensor36arranged at a second radial position in the separation space8.

Again, the centrifugal separator2comprises a heavy phase outlet14leading from the separation space8, the heavy phase outlet14comprising nozzles42arranged at an outer periphery of the rotor4.

In these embodiments, the flow controlling means comprises a slidable bowl bottom46configured to open and close the nozzles42. In this manner, the separated heavy phase is only ejected when the slidable bowl bottom46is opening the nozzles42. Put differently, the heavy phase outlet14is only open when the slidable bowl bottom46is in a position where the nozzles42are open. The slidable bowl bottom as such and its operating mechanism is known in the art.

At least one of the control units32,32′ may be configured to control the slidable bowl bottom46based on the parameter. Thus, the flow of separated heavy phase through the nozzles42of the heavy phase outlet14may be controlled based on the parameter. Mentioned as an example, the position of an interface between the light and heavy phases in the separation space8may form a parameter to be utilised for controlling the opening and closing of the nozzles42.

According to further embodiments, the centrifugal separator2comprises a light phase outlet12and a heavy phase outlet14as discussed in connection withFIG.1. The centrifugal separator2further comprises a sludge outlet, wherein the sludge outlet comprises nozzles42arranged at an outer periphery of the rotor4. That is, the sludge outlet comprises nozzles42as discussed in connection withFIG.3. More specifically, instead of forming a heavy phase outlet, the nozzles42form the sludge outlet. The flow controlling means comprises the slidable bowl bottom46configured to open and close the nozzles42, and is controlled by ate least one of the control units32,32′ for intermittently ejecting sludge from the separation space8.

The at least one of the control units32,32′ may be configured to control the slidable bowl bottom46based on the parameter. Thus, the flow of sludge through the nozzles42of the sludge outlet may be controlled based on the parameter. Mentioned as an example, the position of an interface between sludge and heavy phase in the separation space8may form a parameter to be utilised for controlling the opening and closing of the nozzles42.

In the embodiments ofFIG.3, the control system30is a distributed control system comprising the control units32,32′, i.e. the control system30comprises more than one control unit32,32′, e.g. one control unit32arranged in the rotor4and one control unit32′ arranged in a stationary portion of the centrifugal separator2or as part of the centrifugal separation system1outside of the centrifugal separator2. The more than one control units32,32′ may perform different tasks, such as control tasks, calculation tasks, and communication tasks. Alternatively, the control unit32of the control system30may be arranged in the rotor4, as in the embodiments ofFIG.1, or the control unit32may be arranged in a stationary portion of the centrifugal separator2or as part of the centrifugal separation system1outside of the centrifugal separator2as in the embodiments ofFIG.2.

FIG.4schematically illustrates a cross-section through a portion of a centrifugal separator2of a centrifugal separation system1according to embodiments. The centrifugal separation system1resembles in much the centrifugal separation system1of the embodiments ofFIGS.1-3and the embodiments comprising a sludge outlet discussed above. Accordingly, in the following mainly the differences between the embodiments will be discussed.

In these embodiments, the heavy phase outlet14comprises at least one channel48extending within the rotor4from a radially outer portion of the separation space8towards a central portion of the rotor4. The heavy phase outlet14is mechanically hermetically sealed between the rotor4and a stationary portion of the centrifugal separator2.

The flow of the process liquid through the centrifugal separator2is indicated with arrows inFIG.4. The liquid feed mixture enters the rotor4via the inlet10at a lower portion of the rotor4and flows into the separation space8. In the separation space8, the liquid feed mixture is separated into a light phase flow out of the rotor via the light phase outlet12, and a heavy phase flowing out of the rotor4via the heavy phase outlet14. The inlet10and the light phase outlet12are also mechanically hermetically sealed.

The at least one channel48may comprise a tube, i.e. the at least one channel48has the same cross-sectional area along its extension. Alternatively, the at least one channel48may comprise a passage which has a larger cross-sectional area at the radially outer portion of the separation space8than towards the central portion of the rotor4.

Also in these embodiments the centrifugal separator2comprises nozzles42arranged at an outer periphery of the rotor4. Flow controlling means comprising a slidable bowl bottom46are provided for opening and closing the nozzles42.

In these embodiments, depending on the contents of the liquid feed mixture and the resulting phases from the separation thereof, the nozzles42may form part either of a heavy phase outlet, a sludge outlet, or a combined sludge and heavy phase outlet.

Again, the control unit32may be configured to control the slidable bowl bottom46based on the parameter. Thus, ejection of heavy phase and/or a sludge through the nozzles42may be controlled. Mentioned as examples, the position of an interface between sludge and heavy phase, or a position of an interface between the heavy phase and the light phase, in the separation space8, may form a parameter to be utilised for controlling the opening and closing of the nozzles42.

FIGS.5a-5eillustrate cross sections through embodiments of rotors4of centrifugal separators, such as the centrifugal separators2forming part of centrifugal separation systems1discussed above with reference toFIGS.1-4. InFIGS.5a-5edifferent positions and numbers of the pressure sensors arranged in the rotor4are schematically illustrated. The rotors4shown inFIGS.5a-5eare provided with a heavy phase outlet arranged towards a centre of the rotor4. However, the embodiments are not limited to this kind of rotor4. Alternatively, the rotor4may be provided with the heavy phase outlet at the radially outer periphery of the rotor4, or the rotor4may be additionally be provided with a sludge outlet at the radially outer periphery of the rotor4, as discussed above with reference toFIGS.2-4.

The centrifugal separation system1comprises a control system30, as discussed above with reference toFIGS.1-4, and with reference toFIG.6below. The control unit32of the control system30has been illustrated arranged in the rotor4, but the control unit32may be arranged as in any one the embodiments discussed above with reference toFIGS.1-4, or any other suitable manner. Various example embodiments of the control system30will be further discussed with reference toFIGS.5a-5e. Again, the control system30comprises one or more control units32, a first pressure sensor34, and a second pressure sensor36. The first and second pressure sensors34,36are arranged within the separation space8at different radial positions such that they may take pressure readings from process liquid inside the separation space8.

As mentioned above, the first and second pressure sensors34,36are configured to communicate with the control unit32and the control unit32is configured to determine a parameter of the process liquid within the separation space8during operation of the centrifugal separator2based on measurements from the first and second pressure sensors34,36.

Herein, the term radially outside the stack of separation discs corresponds to a radial position outside the radial extension of the stack of separation disks. The term radially inside the stack of separation discs corresponds to a radial position within the radial extension of the stack of separation discs, i.e. a radial position between the inner and outer radii of the stack of separation disks. The term radially inside the stack of separation discs corresponds to a radial position inside the inner radius of the stack of separation disks.

According to embodiments illustrated inter alia inFIGS.5a-5c, and5e, the first pressure sensor34may be arranged radially outside the stack16of separation disks18. Accordingly, the first pressure sensor34may measure a pressure in a portion of the rotor4and the separation space8where separated heavy phase and/or separated sludge accumulates during operation of the centrifugal separator. Thus, the determined parameter may reflect a measurement affected by the heavy phase and/or sludge in the separation space.

According to embodiments illustrated inFIGS.5aand5b, the second pressure sensor36may be arranged radially outside the stack16of separation disks18. Thus, since the second pressure sensor36is arranged radially inside the first pressure sensor34, the second pressure sensor36may measure a pressure in the separation space8, which under some conditions during operation of the centrifugal separator is affected by separated heavy phase and/or sludge and under other conditions during operation of the centrifugal separator is affected by liquid feed mixture or separated light phase. Thus, the determined parameter may reflect e.g. a filling degree of the separation space with heavy phase and/or sludge, or a density of the heavy phase and/or the sludge.

Mentioned as an example, in the embodiments ofFIGS.5aand5b, the parameter may be a pressure difference between the first and second pressure sensors34,36. Monitoring the pressure difference e.g. via the control unit32, will provide information about a radial position of an interface between the light and heavy phases, and/or an interface between sludge and the heavy phase in the separation space8.

In the embodiments of theFIG.5athe first pressure sensor34is positioned at, or close to, an outermost radial position within the separation space8and the second pressure sensor36is positioned towards the stack16. During operation of the centrifugal separator a particular pressure difference may correspond to a particular radial position of the interface. If the pressure difference remains at a constant value within a certain pressure difference range during operation of the centrifugal separator, this indicates that the radial position of the interface remains constant. If the pressure difference remains constant at a maximum pressure difference in value, this indicates that the interface is radially inside the second pressure sensor36.

In the embodiments ofFIG.5bthe first and second pressure sensors34,36are positioned close to each other within the separation space8radially outside the stack16of separation disks18. During operation of the centrifugal separator, before the interface reaches the first pressure sensor34, the pressure difference between the first and second pressure sensors34,36remains constant. Once the interface passes the first pressure sensor34and thus, is between the first and second pressure sensors34,36, the pressure difference starts to increase. This is an indicator of the interface being in a radial position between the first and second pressure sensors34,36. The change in pressure difference as such may be utilised by the control system to control the centrifugal separator, e.g. to open nozzles of the rotor4by operating a slidable bowl bottom of the rotor4.

Mentioned as an example, the radial distance between the first and second pressure sensors34,36may be within a range of 8-50 mm, or within a range of 10-30 mm. The larger the density difference between the light phase and the heavy phase, the smaller the distance between the first and second pressure sensors may be.

According to embodiments illustrated inter alia inFIGS.5c-5eandFIG.1, the second pressure sensor36may be arranged radially within or radially inside the stack16of separation disks18. More specifically, inFIG.5cthe second pressure sensor36is arranged radially within the stack16, and in the embodiments of theFIG.1the second pressure sensor36is arranged radially inside the stack16.

The Second Pressure Sensor36May Measure a Pressure of the Light Phase Separated in the Separation Space8Radially within or Radially Inside of the Stack16of Separation Discs18.

Accordingly, the determined parameter may reflect a measurement affected by the light phase in the separation space. The determined parameter may reflect e.g. a filling degree of the separation space with heavy phase and/or sludge.

Mentioned as an example, in the embodiments ofFIG.5c, the parameter may be a pressure difference between the first and second pressure sensors34,36. Monitoring this pressure difference, will provide information about a radial position of an interface between the light and heavy phases. For instance, during operation of the centrifugal separator a particular pressure difference may correspond to a particular radial position of the interface.

According to embodiments illustrated inter alia inFIG.5d, the first pressure sensor34may be arranged radially within the stack16of separation disks18. In this manner, a pressure difference over the stack16, or part of the stack16, may be monitored. If the pressure difference should exceed a threshold level, conclusions may be drawn about clogging of the stack16of separation disks18.

According to embodiments illustrated inFIG.5e, the control system40may comprise a third pressure sensor50arranged at a third radial position in the separation space8, wherein the third radial position is radially between the first and second radial positions, and wherein the control unit32is configured to determine a further parameter of the process liquid within the separation space8during operation of the centrifugal separator based on measurements from the third pressure sensor50and at least one of the first and second pressure sensors34,36.

The further determined parameter may be utilised during operation of the centrifugal separator and/or during operation of a system comprising the centrifugal separator. The further parameter may be e.g. a pressure difference in, or a density of, constituents of the process liquid. Accordingly, the further parameter may be e.g. a pressure difference between the first and third pressure sensors34,50, a pressure difference between the third and second pressure sensors50,36, or a density based on pressure measurements from the first and third pressure sensors34,50. In the latter case, suitably, the third radial position is radially outside the stack16of separation disks18.

The density based on pressure measurements from the first and third pressure sensors34,50may be calculated during operation of the centrifugal separator when a pressure difference between the first and third pressure sensors34,50no longer changes. This means that the radial distance between the first and third pressure sensors34,50is filled with heavy phase or sludge. As discussed above, with knowledge about the radial positions of the first and third pressure sensors34,50, the rotational speed of the rotor4, and the pressure difference between the first and third pressure sensors34,50, the density of the heavy phase or sludge may be calculated.

FIG.6illustrates a control system30according to embodiments to be utilised in connection with the different aspects and/or embodiments of the invention. The control system30is also indicated inFIGS.1-5e. The control system30comprises at least one control unit32, which may take the form of substantially any suitable type of processor circuit or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression “control unit” may represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The control system30comprises a memory unit53. The control unit32is connected to the memory unit53, which provides the control unit32with, e.g. stored programme code, data tables, and/or other stored data which the control unit32needs to enable it to do calculations and to control the centrifugal separator and optionally a control a system comprising the centrifugal separator. The control unit32is also adapted to store partial or final results of calculations in the memory unit53. The memory unit53may comprise a physical device utilised to store data or programs, i.e. sequences of instructions on a temporary or permanent basis. According to some embodiments, the memory unit53may comprise integrated circuits comprising silicon-based transistors. The memory unit53may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments.

The control system30further comprises the first and second pressure sensors34,36. Optionally, the control system30may comprise the third pressure sensor50. The control unit32communicates with the pressure sensors34,36,50and receives pressure measurements from these sensors. The control unit32is configured to receiving output signals from the sensors34,36,50. These signals may comprise waveforms, pulses or other attributes, which can be detect as information by control unit32, and which can be directly or indirectly converted to signals processable by the control unit32. Each of the connections to the respective sensors may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection. In the embodiment depicted, only one control unit32and memory53are shown, but the control system30may alternatively comprise more than one control unit and/or memory.

The control unit32may be arranged in the rotor4as indicated inFIGS.1-5e. Alternatively, the control unit32may be arranged outside of the rotor4, and may communicate e.g. wirelessly with the sensors34,36,50. In embodiments comprising more than one control unit may comprise one or more control units arranged in the rotor4and one or more control units arranged outside of the rotor4.

The control unit32and sensors34,36,50may be battery powered by batteries arranged in the rotor of the centrifugal separator. Alternatively, the electric energy may be supplied to the control unit and sensors by a generator arranged in the rotor, a rotary transformer, or slip rings.

An example of data may be pressure measurement data. The pressure sensors34,36,50are configured to provide pressure measurements. Optionally, one or more of the sensors34,36,50may provide measurements of other physical quantities such as e.g. temperature measurements. Such temperature measurements may be utilised when determining a density of one or more of the constituents of the liquid feed mixture. Alternatively, a separate temperature sensor (not shown) may provide temperature measurements to the control unit32.

Examples of data tables may be a table containing positions of an interface between e.g. the light and heavy phases mapped against different values of the pressure difference between measurements from the first and second sensors34,36, or from the first and third sensors34,50, or a data table mapping light phase and/or heavy phase density against temperature.

FIG.7illustrates embodiments of a method100of operating a centrifugal separator. The centrifugal separator may be a centrifugal separator2according to any one of embodiments discussed in connection withFIGS.1-4, and/or comprising a rotor4comprising a control system30as discussed in connection withFIGS.5a-6. In the following reference is also made toFIGS.1-6.

Accordingly, the rotor4is provided with a separation space8, an inlet10leading into the separation space8, a first pressure sensor34arranged at a first radial position in the separation space8, and a second pressure sensor36arranged at a second radial position in the separation space8.

The method100comprises steps of:rotating102the rotor4,conducting104liquid feed mixture into the separation space8via the inlet10,submerging106at the first and second pressure sensors34,36in the process liquid,measuring108a first pressure with the first pressure sensor34,measuring110a second pressure with the second pressure sensor36, anddetermining112a parameter of the process liquid based on the first and second pressures.

As discussed above, the parameter of the process liquid may be e.g. a pressure difference between measurements of the first and second pressure sensors34,36, a radial position of an interface between the light phase and the heavy phase, or a density of the heavy phase. Further physical quantities, such as temperature, of the process liquid may be utilised for determining the parameter.

According to embodiments, the parameter may be a pressure difference between the first and second pressure sensors34,36.

According to embodiments, the parameter may be a density of the process liquid.

According to embodiments, the centrifugal separator2may comprise a flow controlling means38,40, and the method100may comprise a step of:controlling114the flow controlling means38,40based on the parameter. See further above, inter alia with reference toFIGS.1-4.

According to embodiments, the flow controlling means comprises a heavy phase valve38arranged in the heavy phase outlet14, the step of controlling114the flow controlling means may comprise a step of:controlling116the heavy phase valve38. See further above, inter alia with reference toFIG.1.

According to embodiments, wherein the flow controlling means comprises a light phase valve40arranged in the light phase outlet12, the step of controlling114the flow controlling means may comprise a step of:controlling118the light phase valve40. See further above, inter alia with reference toFIG.1.

According to embodiments, wherein the centrifugal separator2comprises nozzles42arranged at an outer periphery of the rotor4, and wherein the flow controlling means comprises a slidable bowl bottom46configured to open and close the nozzles42, the step of controlling114the flow controlling means may comprise a step of:controlling120the sliding bowl bottom46to open and close the nozzles42. See further above, inter alia with reference toFIGS.3and4.

According to embodiments wherein the heavy phase outlet comprises the nozzles42, the step of controlling120the sliding bowl bottom46to open and close the nozzles42will result in ejection of accumulated heavy phase from the periphery of the separation space8when the nozzles42are opened.

According to embodiments where in the centrifugal separator2comprises a sludge outlet, the sludge outlet comprising the nozzles42, the step of controlling120the sliding bowl bottom46to open and close the nozzles42will result in ejection of accumulated sludge from the periphery of the separation space8when the nozzles42are opened.

According to embodiments, wherein the heavy phase outlet comprises nozzles42arranged at an outer periphery of the rotor4, and wherein the flow controlling means comprises a mechanism44for changing a total opening area of the nozzles42, the step of controlling114the flow controlling means may comprise a step of:controlling122the mechanism44to change the total opening area. See further above, inter alia with reference toFIG.2.

According to embodiments, wherein the centrifugal separator2comprises a third pressure sensor50arranged at a third radial position in the separation space8, wherein the third radial position is radially between the first and second radial positions, the method100may comprise steps of:measuring124a third pressure with the third pressure sensor50, anddetermining112a further parameter of the process liquid based on the third pressure and at least one of the first and second pressures. See further above, inter alia with reference toFIG.5e.

According to an aspect there is provided a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method100according to any one of aspect and/or embodiments discussed herein, in particular with reference toFIG.7. One skilled in the art will appreciate that the method100of operating a centrifugal separator may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in a computer or control system, ensures that the computer or control system carries out the desired control, such as the method steps102-124according to the invention. The computer program is usually part of a computer programme product which comprises a suitable digital storage medium on which the computer program is stored.

FIG.8shows a computer-readable storage medium90according to embodiments. The computer-readable storage medium90comprises instructions which, when executed by a computer or other control system30, causes the computer or other control system30to carry out the method100according to any one of aspects and/or embodiments discussed herein. The computer-readable storage medium90may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the steps102-124according to some embodiments when being loaded into the one or more control unit32of the control system30. The data carrier may be, e.g. a ROM (read-only memory), a PROM (programmable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a CD ROM disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer-readable storage medium may furthermore be provided as computer program code on a server and may be downloaded to the control system30remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.

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.