A centrifugal separator for separating a liquid mixture

Abstract

The present invention provides a centrifugal separator (1) for separating a liquid mixture into at least one separated liquid phase. The separator is comprising a reusable portion (2) arranged for use in multiple separation processes and a single use portion (10) arranged for being replaced between separation processes. The single use portion (10) comprises a separator insert (11) in which the separation takes place, said insert (11) forming a preassembled interchangeable unit, and at least one tube (12) arranged for transporting liquid mixture to said separator insert (11) and / or at least one separated phase from said separator insert (11). The reusable portion (2) comprises a stationary frame (3) in which said separator insert is mounted and a drive unit (4) arranged for rotating said separator insert (11) in relation to the stationary frame (3) around an axis of rotation (X). The centrifugal separator (1) further comprises at least one sensor (20) for measuring a physical property of the liquid feed mixture or a separated liquid phase. The at least one sensor (20, 30) comprises a sensing element (21, 31) that is responsive for said physical property, and a processing unit (22, 32) configured for converting the sensed physical property to an electrical variable. At least said processing unit (22, 32) is arranged in the reusable portion (2) of the centrifugal separator (1).

Description

[0001] A CENTRIFUGAL SEPARATOR FOR SEPARATING A LIQUID MIXTURE

[0002] Technical field

[0003] The present inventive concept relates to the field of centrifugal separators.

[0004] More particularly, it relates to a centrifugal separator comprising a reusable portion and a single use portion.

[0005] Background

[0006] Centrifugal separators are generally used for separation of liquids and / or solids from a liquid mixture or a gas mixture. During operation, fluid mixture that is about to be separated is introduced into a rotating bowl and due to the centrifugal forces, heavy particles or denser liquid, such as water, accumulates at the periphery of the rotating bowl whereas less dense liquid accumulates closer to the central axis of rotation. This allows for collection of the separated fractions, e.g. by means of different outlets arranged at different radii from the rotational axis.

[0007] In the field of pharmaceuticals, biopharmaceuticals, biotechnology and thereto related fields, separation of substances from a liquid mixture, such as separation of cells from a cell culture mixture, are performed in a sterile environment. Traditionally, equipment made e.g. from stainless steel has been used, which equipment is sterilised between production batches. However, lately, disposable centrifugal separation equipment made for single use, i.e. for separation of one product batch or a limited number of product batches, has been introduced. Such centrifugal separation equipment comprises a base unit configured to be reused and for no contact with the product and single use portions, which are configured to be exchangeable and to come into contact with the product.

[0008] In order to monitor and / or control such single use separation processes, a number of single use sensors are typically used. These however need to be replaced between each separation process due to contamination from any of the processed liquids. This leads to large costs and increased waste. Thus, there is a need in the art for improved sensor solutions for centrifugal separators used in single use applications.

[0009] Summary

[0010] It is an object of the invention to at least partly overcome one or more limitations of the prior art. In particular, it is an object to provide a centrifugal separator for single use application that lead to a reduced waste.

[0011] As a first aspect of the invention, there is provided a centrifugal separator for separating a liquid mixture into at least one separated liquid phase, said separator comprising a reusable portion arranged for use in multiple separation processes and a single use portion arranged for being replaced between separation processes, wherein said single use portion comprises

[0012] - a separator insert in which the separation takes place, said insert forming a preassembled interchangeable unit, and

[0013] - at least one tube arranged for transporting liquid mixture to said separator insert and / or at least one separated phase from said separator insert; and wherein said reusable portion comprises

[0014] - a stationary frame in which said separator insert is mounted;

[0015] - a drive unit arranged for rotating said separator insert in relation to the stationary frame around an axis of rotation (X); wherein the centrifugal separator further comprises at least one sensor for measuring a physical property of the liquid feed mixture or a separated liquid phase, said at least one sensor comprising

[0016] - a sensing element that is responsive for said physical property, and

[0017] - a processing unit configured for converting the sensed physical property to an electrical variable; wherein at least said processing unit is arranged in the reusable portion of the centrifugal separator.

[0018] The centrifugal separator may be arranged for separating the liquid mixture into one or two liquid phases, such as a liquid light phase and / or a liquid heavy phase, in which the liquid heavy phase has a density that is higher than the liquid light phase. Consequently, the centrifugal separator may comprise a single outlet for a discharged liquid phase or two outlets for discharged liquid phases. The centrifugal separator may be for continuous separation of a liquid feed mixture, in which the liquid mixture is fed continuously to the separator. However, the centrifugal separator may also be for batch processing of e.g. the contents of a fermentation tank.

[0019] The first aspect of the invention is based on the insight that even though the centrifugal separator is a so-called single use separator, at least part of the sensor or sensors used could be reused. Thus, at least the processing portion, such as electronics etc, can be placed in the reusable portion, whereas only the sensing element - if needed - may be placed in the single use portion. This severely reduces waste.

[0020] The single use portion comprises a separator insert, such as a replaceable insert as known from e.g. WO 2020 / 120357. Thus, such an insert may be configured to be mounted to the reusable portion of the separator, such as to a rotatable support in the stationary frame of the reusable portion. The separator insert may thus easily be inserted into and taken out of the reusable portion between separation processes. The exchangeable separator insert may thus be for processing of one product batch, such as a single product batch in the pharmaceutical industry, and then be disposed. The exchangeable separator insert may comprise a polymeric material or consist of a polymeric material.

[0021] Further, the insert may comprise an inlet for the liquid mixture that is to be separated and an outlet or outlets for the separated phases. The insert may form within itself a separation space which may or may not comprise discs or blades that enhances the separation efficiency. Such discs may be in the form of a stack of separation discs, e.g. frustoconical separation discs, as known in the art.

[0022] The single use portion further comprises at least one tube. The at least one tube may be part of a tube kit that is configured to be mounted to the separator insert either before or after the separator insert has been mounted to the reusable portion. Thus, the “at least one tube” may comprise an inlet tube and one or two outlet tubes for separated phases. In addition, one or several disposable containers may be part of the single use portion of the centrifugal separator. Such disposable containers may be used for collecting the separated phases and / or used for measuring the flow rate of the liquid feed mixture any separated phase. A disposable container may be a flexible bag and may be arranged for being cyclically filled and emptied.

[0023] The tube used for transporting the liquid mixture may be a polymeric tubing, such as a silicone tubing.

[0024] The reusable portion of the centrifugal separator comprises a stationary frame in which the single use insert is mounted. The frame may thus comprise a rotatable support for the single use insert. The stationary frame may be arranged to support the separator insert by means of at least one bearing, for example a ball bearing.

[0025] Further, the reusable portion comprises a drive unit, such as a motor, arranged for rotating the single use insert around an axis of rotation, which may be a vertical axis of rotation. As an example, the drive unit may be arranged to rotate a rotatable support for the single use insert. The drive unit may be integrated in the stationary frame. The drive unit may be an electrical motor arranged to rotate the rotatable support directly or indirectly by a suitable transmission, such as a belt or a gear transmission. The drive unit may also be a magnetic drive unit comprising magnetic bearing devices. As an example, the single use insert may be rotatably mounted with magnetic bearing devices within the stationary frame, such as rotatably mounted at two positions along the axial extent of the single use insert. The magnetic bearing devices may operate e.g. according to a combined electro- and permanent-magnetic principle to rotate the single use insert.

[0026] The centrifugal separator further comprises at least one sensor for measuring a physical property of the liquid feed mixture or a separated liquid phase. Accordingly, the sensor or sensors may be arranged upstream and / or downstream of the separator insert.

[0027] The centrifugal separator may comprise at least two, such as at least three, sensors, which may or may not be of the same sort and may or may not measure the same physical property.

[0028] A sensor may for example be selected from an inductive sensor, capacitive sensor, photoelectric sensor, ultrasonic sensor and a magnetic field sensor.

[0029] As an example, the physical property measured by a sensor may be selected from the temperature, the pressure, the flow and the turbidity of the liquid feed mixture or a separated liquid phase.

[0030] In embodiments, the physical property measured by a sensor is selected from the temperature, the pressure and the turbidity of the liquid feed mixture or a separated liquid phase.

[0031] The sensor comprises a sensing element that is responsive for the physical property, and a processing unit configured for converting the sensed physical property to an electrical variable, such as an electric signal that may be measured and processed. The processing unit may further comprise may comprise electronics that amplifies or changes the form of the electric signal. According to the inventive concept, at least the processing unit is arranged in the reusable portion of the centrifugal separator.

[0032] The processing unit may further comprise e.g. an output indicator for displaying the results and / or a communication unit that is configured to be connected to a control unit and send the results to such a control unit for storing or further processing. The control unit may be part of the sensor itself or may for example be part of a common control unit used for several sensors. The control unit may further be configured to also control functions of the centrifugal separator, e.g. based on the readings from one or several sensors. As an example, the centrifugal separator may comprise several sensors connected to the same processing unit or control unit.

[0033] The sensor may be an active or passive sensor. If it is an active sensor, the sensor may further comprise a power supply or be configured to be connected to a power supply.

[0034] In embodiments, the sensing element of the at least one sensor is arranged in said single use portion of the centrifugal separator. Thus, the sensing element may be disposable together with the tube of the single use portion whereas e.g. all electronics may be placed on the reusable portion of the sensor. In addition, the sensor may comprise one or several connectors arranged in the single use portion and configured to connect the sensing element or elements to one or several processing units in the reusable portion. As an example, several sensing elements may share the same connector. In this way, the waste of a sensor may be reduced to a very small amount of metal and a connector.

[0035] As an example, the sensing element may be a strain gauge element or a thermocouple element. Such elements may be attached directly onto or into a plastic tubing of the single use portion.

[0036] The strain gauge may in the form of an etched grid or thin wire and may be configured to work as a pressure sensor.

[0037] The thermocouple element may comprise two dissimilar metals joined together as one end to form a junction that generates a voltage when experiencing a temperature change.

[0038] In embodiments, also the sensing element is arranged in said reusable portion of the centrifugal separator.

[0039] In this way, waste may be reduced to a minimum. As an example, the whole sensor may be reused with the reusable portion.

[0040] As an example, the sensor may be a clamp-on sensor configured for being arranged on or interact with the at least one tube for measuring a physical property of the liquid feed mixture or a separated liquid phase. A “clamp-on sensor” is a sensor that interacts with the tube without needing to cut into or modify the tube. Thus, the clamp-on sensor may be a non-invasive measurement device configured to be attached externally to the tube without needing to penetrate the tube. This thus further reduces any risk for contamination of the liquid mixture being processed in the centrifugal separator and transported within the tube. The clamp-on sensor may comprise a clamp-on element for engaging the surface of the tube.

[0041] As an example, the clamp-on sensor may be configured for measuring the the turbidity, pressure or temperature of the liquid within the tube. The inventors have found that these physical properties may be suitable for clamp-on sensing and may be important for controlling the separation process.

[0042] Thus, in embodiments, the sensor is a clamp-on sensor configured for being arranged on or interact with the at least one tube for measuring a physical property of the liquid feed mixture or a separated liquid phase, wherein the physical property is the turbidity, the pressure or the temperature of the liquid feed mixture or a separated liquid phase within the tube.

[0043] According to an example, the clamp-on sensor is a turbidity sensor and configured for measuring the scattered light, back-scattered light or absorbed light from particles within said tube.

[0044] Accordingly, such the amount of scattered light or absorbed light may directly be related to the turbidity of the liquid in the tube. Higher turbidity means more particles are present, resulting in more scattered light.

[0045] As an example, the clamp-on sensor for measuring the turbidity may comprise a clamp-on element for engaging with said tube, a transmitter for emitting light into the tube at the position of the clamp-on element and a detector for detecting the scattered light, back-scattered light or absorbed light.

[0046] The clamp-on element allows the sensor to be securely attached to the tube. The transmitter may be configured for transmitting light in the visible spectrum, such as near-infrared (around 850 nm) or red light (around 660 nm). Such wavelengths may provide a good balance between sensitivity to suspended particles and minimal interference from the colour of the liquid such as water, within the tube. The detector may accordingly be sensitive to the wavelengths emitted by the transmitter.

[0047] In such a sensor, the transmitter and detector may form the “sensing element” of the sensor.

[0048] Moreover, the tube may be a flexible tube and may have an outer diameter that is large enough so that the outer surfaces of the tube are flattened out when being engaged with the clamp-on element.

[0049] In that way, the light emitted by the transmitter is less scattered by the tube itself and thereby increases the sensitivity of the sensor. The clamp-on element and the flexible tube may be arranged such that outer surfaces are flattened out to form a plane having a normal that is substantially parallel to the light emitted by the transmitter. The tube may in a non-engaging position have rounded outer surfaces. These may conform to flat surfaces of the clamp-on element, thereby being flattened out at least to some extent. According to an example, the clamp-on sensor is a pressure sensor and is configured for measuring the expansion force or the contraction force of said tube and convert said force to a pressure within said tube.

[0050] Thus, the expansion or contraction of the tube may be converted, e.g. by using a calibration formula, to a pressure value.

[0051] As an example, the clamp-on sensor may comprise a load cell for measuring the expansion force and / or the contraction force and a clamp-on element for fixating said tube to the load cell.

[0052] The load cell may thus function as a transducer that converts the mechanical force experienced by the load cell to an electrical signal. The load cell may comprise a strain gauge that deforms by the expansion force and / or contraction force of the tube, thereby changing an electrical characteristic, such as its electrical resistance. The clamp-on element allows the tube to be securely attached to the load cell. The load cell may thus function as the “sensing element” of the sensor.

[0053] Furthermore, the processing unit of the sensor may then be configured for receiving information of the measured expansion force and / or contraction force and converting the measured force to a pressure value. Such conversion may be performed using a calibration formula or a pre-set calibration curve. Such calibration curve may have been pre-calculated by subjecting the tube to different known pressures - such as different air pressures or known pressures from other medium, such as water - so as to relate the measured tube expansion and / or contraction forces by the load cell to specific pressure values. The calibration formula may also take the impact from the ambient temperature and / or the temperature of the liquid within the tube into account.

[0054] The above conversion of the measured force by the load cell to a pressure may alternatively be performed in a control unit of the centrifugal separator, such as the control unit that is also used for controlling other functions of the separator, such as rotational speed etc.

[0055] According to another example, the clamp-on sensor is a temperature sensor configured for measuring the temperature of the outside surface of the tube.

[0056] The outside surface of the tube may reflect the temperature of the liquid within the tube and may be used as an indirect measurement of the liquid temperature. However, the processing unit of the sensor may be further configured for is further configured for receiving input of the measured temperature of the outside surface of the tube and converting the received input to a value representing the temperature of the liquid within the tube. Such conversion of the temperature of the outside surface of the tube to the temperature of the liquid within the tube may be performed by using a calibration formula or a pre-set calibration curve. Such calibration curve may have been precalculated by subjecting the tube to media of different known temperatures so as to relate the measured temperature of the outside surface of the tube to the temperature of the liquid within the tube. As an example, the above conversion may also involve taking the ambient temperature into account, i.e. also taking the ambient temperature as input for the conversion.

[0057] As an example, the clamp-on sensor may comprise a clamp-on element for fixating the sensor to the tube and a detector for measuring the radiation from the tube.

[0058] The detector may be positioned to measure the temperature of the outside surface of the tube at the position of the clamp-on element.

[0059] As an example, the detector may be an infrared (IR) detector. The spectral range of the IR detector may e.g. be between 8-14 pm.

[0060] However, in other examples, the clamp-on sensor for measuring the temperature comprises a thermocouple wire that is clamped to the outside surface of the tube. In other examples, the clamp-on sensor for measuring the temperature comprises a Resistance Temperature Detector (RTD), a thermistor or a Semiconductor-Based Sensors that is clamped-on or engaged to the outer surface of the tube.

[0061] Furthermore, the separator insert may further be as disclosed in WO 2020 / 120357. Thus, the insert may comprise an inlet for receiving a liquid feed mixture to be separated, at least one liquid outlet for discharge of a separated liquid phase. As an example, the insert may comprise a liquid light phase outlet and a liquid heavy phase outlet, in which the liquid light phase has a density that is lower than the density of the liquid heavy phase. The inlet and the outlet or outlets may be arranged at one axial end of the separator insert, or they may be arranged at different ends. As an example, all inlet and outlets may be on the axial upper portion of the insert. As a further example, the inlet may be at one axial end portion, whereas one or both of the outlets are arranged on the opposite axial portion.

[0062] The separator insert may thus be a centrifuge bowl and may be free of any further outlets for separated phases. Thus, the separator insert may be solid in that it is free of any peripheral ports for discharging e.g. a sludge phase accumulated at the periphery of the separation space. The insert may enclose a separation space in which the separation of the liquid feed mixture, such as a cell culture mixture, takes place during operation, and wherein the separation space is arranged for receiving liquid feed mixture from the inlet.

[0063] The separation space within the separator insert may comprise a stack of separation discs arranged centrally around the axis of rotation. The stack may comprise frustoconical separation discs. The separation discs may alternatively be axial discs arranged around the axis of rotation.

[0064] The separation discs may e.g. comprise a metal or be of metal material, such as stainless steel. The separation discs may further comprise a plastic material or be of a plastic material.

[0065] The reusable portion may also comprise a separator control unit, which may be configured to control the speed of the drive unit. The separator control unit may further be configured to receive input from one or several sensors as discussed herein above and to control the separation process based on such input.

[0066] Brief description of the drawings

[0067] The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise.

[0068] Fig. 1 is a schematic view of an embodiment of a centrifugal separator having a reusable portion and a single use portion.

[0069] Fig. 2 is a schematic view of another embodiment of a centrifugal separator having a reusable portion and a single use portion.

[0070] Fig. 3 is a schematic perspective view of a sensor of the centrifugal separator that can be used for detecting turbidity.

[0071] Fig. 4 is a schematic perspective view of the sensor of Fig. 3 being clamped-on to a tube.

[0072] Fig. 5 is a schematic view of the cross-section of the sensor of Fig. 4.

[0073] Fig. 6 is a schematic perspective view of a sensor of the centrifugal separator that can be used for detecting pressure.

[0074] Fig. 7 is a schematic view of the cross-section of the sensor of Fig. 6.

[0075] Fig. 8 is a schematic perspective view of a sensor of the centrifugal separator that can be used for detecting temperature. Fig. 9 is a schematic view of the cross-section of the sensor of Fig. 8.

[0076] Fig. 10 is a schematic view of the cross-section of the reusable portion of a centrifugal separator arranged for receiving a separator insert.

[0077] Fig. 11 is a schematic view of the cross-section of the reusable portion of Fig. 10 into which a separator insert has been mounted.

[0078] Detailed description

[0079] Fig. 1 schematically shows a centrifugal separator 1 according to an embodiment of the invention. The separator 1 is for separating a liquid mixture into two separated liquid phases - a liquid light phase and a liquid heavy phase. As indicated by the dotted sections in, the centrifugal separator 1 comprising a reusable portion 2 that may be use in multiple separation processes and a single use portion 10 arranged for being replaced between separation processes. The centrifugal separator is thus what is referred to as a “single use” separator and may be used in the pharmaceutical industry for e.g. separating a cell phase (the liquid heavy phase) from a cell culture mixture. The liquid light phase could then comprise e.g. a biomolecule that has been produced by the cells.

[0080] The single use portion 10 comprises a separator insert 11 in which the actual separation takes place. This insert 11 is adapted to be mounted to within the stationary frame 3 of the reusable portion. The separator insert 11 forms a preassembled interchangeable unit which may be sterilized and may be discarded after use. The insert forms the centrifuge bowl and usually comprises polymeric parts. Furthermore, the insert 11 comprises connections to at least one tube 12. In this example, tubes 12a, 12b, 12c may be connected to the insert 11. As an alternative, all or some of the tubes 12a, 12b, 12c are provided together with the insert 11 as a preassembled unit. Tube 12a is arranged for transporting the liquid mixture to be separated to the separator insert 11 , whereas tube 12b and 12c are arranged for transporting the discharged separated liquid heavy phase and the discharged liquid light phase, respectively, from the separator insert to any unit (not shown) downstream of the separation process. Thus, the centrifugal separator 1 may form part of an overall separation or production process, such as a bioprocess for producing a biopharmaceutical.

[0081] Moreover, the outlet tube 12c for the separated liquid light phase is connected to a receiving bag 13 as discussed in e.g. W02021191023A1. By measuring the weight increase over time in such a bag, the flowrate of the separated and discharged liquid light phase may be estimated. The single use portion 10 is in the centrifugal separator 1 the only portion that that comes in contact with the liquid mixture to be separated or any of the separated liquid phases.

[0082] The reusable portion 2 comprises in this example a stationary frame 3 in which the separator insert 11 is mounted as well as a drive unit 4 in the form of a motor that is arranged for rotating the mounted separator insert 11 in relation to the stationary frame 3 around a vertical axis of rotation (X). The motor 4 may be arranged to rotate the insert 11 at a high rate, such as above 500 rpm, such as above 1000 rpm, such as above 2000 rpm, such as above 5000 rpm. The stationary frame 3 and the separator insert 11 will be further discussed in relation to Figs. 10 and 11 below.

[0083] In order to monitor the separation process and sometimes also control the separation process, the centrifugal separator 1 further comprises at least one sensor 20, 30. In the example shown in Fig. 1 , the separator 1 comprises a first sensor 20 for measuring a physical property of the separated liquid light phase in tube 12c and a second sensor 30 for measuring a physical property of the separated liquid heavy phase in tube 12b. The physical properties may for example be selected from pressure, temperature and turbidity, as will be further explained in relation to Figs. 3- 9 below.

[0084] A sensor 20, 30 of the centrifugal separator 1 comprises a sensing element 21, 31 that is responsive to the physical property to be measured and a processing unit 22, 32 configured for converting the sensed physical property to an electrical variable. A processing unit 22, 32 may thus comprise processing circuitry for converting the physical variable to an electrical variable. Such circuitry may further comprise signal conditioning circuitry configured amplify, filter or modify the electrical signal. In this example, the sensors 20, 30 each further comprise a communication unit 23, 33 comprising electronics for communicating the signal to a control unit 34. In the example of Fig. 1 , the control unit is a central control unit configured for receiving input from both sensors 20, 30. However, in other embodiments, each sensor 20, 30 may comprise or be connected to its own control unit. The control unit 34 may be connected to or be the control unit used for controlling other portions of the centrifugal separator 1 , such as the speed of the drive motor 4. As is understood, this control unit 34 may be a stand-alone component arranged remotely from - but in communicative connection with - the separator 1 but may alternatively be embedded in the separator 1 for separator control. The control unit 34 may comprise a central processing unit (CPU) and may be embodied in the form of one or more microprocessors. As is understood, the communicative connection of a control unit 34 with the separator 1 may be wired or wireless.

[0085] According to the inventive concept, at least the processing unit 22, 32 of at least one of the sensors 20, 30 is arranged in the reusable portion 2 of the centrifugal separator 1. This is in contrast to prior art single-use separator systems , in which the whole sensor has been part of the single use portions and hence been discarded after use. According to the present invention, at least the processing unit 22, 32 may be reused, thereby severely minimizing waste. If the sensor 20, 30 further comprises a communication unit 23, 33, also such unit may be reused, i.e. form part of the reusable portion 2 of the separator 1.

[0086] In the specific example illustrated in Fig. 1, the sensing elements 21 , 31 of the sensors 20, 30 are however arranged in the single used portion 10 of the separator. Such sensing elements 21, 31 may be arranged on and configured to interact with the tube 12. The sensing elements 21 , 31 may for example be a strain gauge if measuring the pressure within a tube 12 or a or a thermocouple element if measuring a temperature within the tube 12. Thus, if an etched grid (or thin wire) constituting a strain gauge attached directly onto or into a weldable piece of plastic tubing could be made to work as a pressure sensor.

[0087] As an example, a sensing element 21, 31 may be supplied together with, integrated with or attached to the single-use tube 12 and comprise a connecting element 21a, 31a. Upon mounting the single use portion 10 to the reusable portion 2 before a separation process, the connecting element 21a, 31a may be used to link the sensing element 21 , 22 (e.g. using a wire) to a processing unit 22, 32 of the sensor in the reusable portion 2. A connecting element 21a, 21b, may thus be configured to link the strain gauge or thermocouple element to the processing unit.

[0088] The connecting element 21a, 31a may for example be a screw terminal or a plug connector.

[0089] Hence, the waste originating from the sensor 20, 30 would be reduced to a small amount of metal and the connector.

[0090] However, in other embodiments, the sensor 20, 30 is arranged so that whole sensor 20, 30 may be reused, i.e. be part of the reusable portion 2. Such an embodiment is illustrated in Fig. 2, which shows the same centrifugal separator 1 as discussed in relation to Fig. 1 above but with the difference that also the sensing element 21 of sensor 20 and the sensing element 31 of sensor 30 are arranged in the reusable portion 2 of the centrifugal separator 1. Such sensor 20, 30 could be a clamp-on sensor configured for being arranged on or interact with the inlet tube 12a, or any of the outlet tubes 12b, 12c. The clamp-on sensor could be arranged for measuring a physical property of the liquid feed mixture or a physical property separated liquid phase, such as the pressure, temperature or turbidity. Such clampon sensors 20 will be further discussed in relation to Figs. 3-9 below.

[0091] During operation of a centrifugal separator 1 of any of Fig. 1 and Fig. 2, the separator insert 11 is mounted within the stationary frame 3. Inlet tube 12a, and the two outlet tubes 12b, 12 c are connected to the insert before liquid feed mixture to be separated is fed to the separator insert 11 via inlet tuber 12a. The separator insert 11 thus functions as the separator bowl in which the separation takes place. The separated liquid heavy phase is discharged to outlet tube 12b and the separated liquid light phase, having a density that is lower than the density of the liquid heavy phase, is discharge via outlet tube 12c. The sensors 20, 30 measure a physical property of the discharged phases, such as the pressure or temperature, and this information is sent to control unit 34. The control unit 34 may then be configured to control the separation process based on the input from one or several of the sensors, such as increasing or decreasing the rotational speed of the separator insert 11 and / or adjust the counter pressure in any of the liquid outlets 12b, 12 c. This may be for controlling the separator split within the bowl, i.e. how large fraction is discharged as liquid heavy phase and liquid light phase, respectively.

[0092] Figs. 3-5 shows an embodiment of a clamp-on sensor 20 for measuring the turbidity of the liquid feed mixture or any of the discharged separated liquid phases. Such clamp-on sensor 20 is thus arranged to interact with a tube 12 of the single use portion of the separator 1 and may be reused, i.e. it does not come in contact with the liquid within the tube 12 during use. The clamp-on sensor 20 is a turbidity sensor and is configured for measuring the scattered light, back-scattered light or absorbed light from particles within the tube 12. Such measurements are well known parameters representing the turbidity within a liquid.

[0093] The turbidity sensor 20 comprises a base portion 27 from which a first 28 and a second 29 projection that are spaced apart and extend in a first direction Y1 , forming a channel 24 for receiving a tube 12 therebetween. The channel 35 extends in a second direction Y2 that is perpendicular to the first direction Y1. A flat surface 38 of the first projection 28 and an opposite flat surface 37 of the second projection for two side surfaces of the channel 35. These surfaces have a normal that is substantially parallel to the extension of the channel 35, and thus perpendicular to both the first Y1 and second Y2 direction. The two projections 28, 29 form a clamp-on element 24 hat is arranged for engaging with the tube 12 in which the turbidity is to be measured. The sensor 20 further comprises a transmitter 25 for emitting light into the tube 12 at the position of the clamp-on element 24 and a detector 26 for detecting the scattered light, back-scattered light or absorbed light. In this example, the transmitter 25 is arranged within the first projection 28 and the detector 26 is arranged in the second projection 29. With such a setup, the turbidity sensor 20 may be arranged for measuring the scattered light at a specific angle or absorbed light. If the sensor 20 is for measuring back-scattered light, then both the transmitter 25 and detector 26 could be placed within the same projection 28, 29.

[0094] The transmitter 25 and detector 26 thus forms the sensing element 21 of the sensor 20.

[0095] Fig. 4 further illustrates a tube 12 being engaged with the clamp-on element 24 of the sensor. In this way, the turbidity of a liquid within the tube 12 may be measured by the transmitter 26 and the detector 25. As further illustrated in the cross-section shown in Fig. 5, the channel 35 in which the tube 12 is arranged has a slightly smaller diameter D than the outer diameter d of the tube 12. If the tube 12 is a flexible tube, this means that the outer surfaces of the tube 12 are flattened when being engaged with the clamp-on element, as illustrated by the dotted cross-section 12d of the tube 12 in Fig. 5. Due to the flat inner surfaces 38, 37 of the first 28 and second 29 projections that forms the channel 35, the outer surface of the tube 12 may conform to the inner surfaces 38, 37 and be flatted out at the position of the transmitter 25 and detector 26. In this way, the light path between transmitter 25 and detector 26 does not extend to a rounded surface, which may severely increase the measurement accuracy and decrease light being reflected on the otherwise rounded outer surfaces of the tube 12.

[0096] Figs. 6 and 7 show an embodiment of a clamp-on sensor 20 for measuring the pressure of the liquid feed mixture or any of the discharged separated liquid phases. The sensor 20 is thus a pressure sensor and is configured for measuring the expansion force and / or the contraction force of an elastic tube 12 and convert the measured force to a value of the pressure within the tube. In order to do this, the clamp-on sensor 20 comprises a load cell 40 - as seen in the cross-section of Fig. 7 - arranged for measuring the expansion force and / or the contraction force of the tube 12. The load cell 40 is connected to a clamp-on element 24, which is arranged for fixating the tube 12 to the load cell. The clamp-on element 24 is arranged on a support plate 41 having through holes 42 for firmly connecting the support plate to other fixed structures, such as a fixed structure of the centrifugal separator 1. The clamp-on element 24 forms a channel 36 in which the tube 12 is arranged. The channel 36 may have a width slightly smaller or equal to the outer diameter of the tube 12. If the tube is an elastic tube 12, it may thus be firmly attached to the clampon element 12. The clamp-on element 24 thus has a hook-shaped profile protruding from the support plate 41 and extending along the length of the channel 36 for receiving the tube 12. However, the clamp-on element 24 be any other suitable element, tube clamp or pipe clamp arranged for fitting snugly over the tube 12 in which the pressure is to be measured.

[0097] As indicated in Fig. 7, the tube 12 fitted into the clamp-on element 24 rests on a connector portion 43 of the load cell 40. The force from the tube expansion or contraction is measured with the loadcell 40, and connected to the load cell 40 is a processing unit 22 configured for converting the load cell value to a pressure value. Accordingly, the processing unit 22, 32 is configured for receiving information of the measured force and converting the measured force to a pressure value. For this, the processing unit 20 may comprise suitable circuitry. The values from the load cell 40 may be converted to a pressure using e.g. a formula, calibration curve or lookup table specific for the type of tube 12 used. Such formula, calibration curve or lookup table may have been calculated by analysing the tube 12 before being used in the separation process, e.g. by measuring the load cell output when subjecting the tube to different known air pressures within the tube.

[0098] All components of the clamp-on pressure sensor 20 may be part of the reusable portion 2 of the centrifugal separator 1, thereby decreasing the amount of waste generated in the separation process.

[0099] Figs. 8 and 9 show an embodiment of a clamp-on sensor 20 for measuring the temperature of the liquid feed mixture or any of the discharged separated liquid phases. In this example, the clamp-on sensor 20 is a temperature sensor configured for measuring the temperature of the outside surface of the tube 12. Either the temperature of the outside surface may be used as an indirect measurement of the temperature within the tube 12, or it may be recalculated to the temperature within the tube 12. The clamp-on sensor 20 comprises a clamp-on element 24 for fixating the sensor 20 to the tube 12 and a detector 50 for measuring the radiation from the tube 12. As discussed in relation to the sensor of Fig. 6 and 7, the clamp-on element 24 is arranged on a support plate 41 having through holes 42 for firmly connecting the support plate to other fixed structures, such as a fixed structure of the centrifugal separator 1. The clamp-on element 24 forms a channel 36 in which the tube 12 is arranged. The channel 36 may have a width slightly smaller or equal to the outer diameter of the tube 12. If the tube is an elastic tube 12, it may thus be firmly attached to the clamp-on element 12. The clamp-on element 24 thus has a hookshaped profile protruding from the support plate 41 and extending along the length of the channel 36 for receiving the tube 12. However, the clamp-on element 24 be any other suitable element, tube clamp or pipe clamp. The detector 50 is arranged at the position of the clamp-on element 24 for measuring the temperature of the outside of the fixed tube 12. The sensor 50 rest on a support structure 51 that is perpendicular to the surface of the support plate 41. In this example, the detector 50 is an infrared (IR) detector for measuring the IR radiance, and thus temperature, of the tube 12. The detector 50 is connected to a processing unit 22 of the sensor 20, which may comprise circuitry for converting the sensed temperature to an electrical signal. In addition, the processing unit may be configured for converting the received signal to a temperature of the liquid within the tube. In other words, the processing unit 22 is further configured for receiving input of the measured temperature of the outside surface of the tube 12 and configured converting the received input to a value representing the temperature of the liquid within the tube 12. In order to do this a formula, calibration curve or lookup table may be used. Such formula, calibration curve or lookup table may also take into account the ambient temperature, since this will affect the measured outside temperature of the tube 12. Further, such formula, calibration curve or lookup table may have been calculated by analysing the tube 12 before being used in the separation process, e.g. by measuring the outside temperature of the tube 12 when subjecting the tube to different liquids having different temperatures at different ambient temperatures.

[0100] All components of the clamp-on temperature sensor 20 may be part of the reusable portion 2 of the centrifugal separator 1 , thereby decreasing the amount of waste generated in the separation process.

[0101] Fig. 10 and 11 gives some further details of the stationary frame 3 and the separator insert 11 of the centrifugal separator 1. In the disclosed example, the insert 11 has fluid connections in both top and bottom, but the overall principle is the same as the separator insert 11 shown in Figs .1 and 2, in which all fluid connections are at the top.

[0102] Fig. 10 schematically illustrates a cross section through the stationary frame 3 in an embodiment of the centrifugal separator 1. The stationary frame 3 comprises a rotational support 62 for receiving a separator insert 11 within housing (the insert 11 is not shown in Fig. 10). In this example, the stationary frame 3 comprises a vertical member 61 and at least part of the drive unit 4, in the form of an electrical drive motor, may be arranged in the vertical member 61 and be connected to the rotational support 62 via belt 5. The rotational support 62 is in turn supported via one or several bearings 63 within the housing 66 to rotate about vertical rotational axis X. The stationary frame 3 is stationary during use of the centrifugal separator 1 but may be movable e.g., in order to be positioned at different locations at a production facility of the user. For this purpose, the stationary frame 3 may be provided with wheels 68.

[0103] Seen along the rotational axis X, the rotatable support 62 has an upper axial end comprising a first opening 71 and a lower axial end comprising a second opening 70. The first 71 and second 70 opening form through holes in the rotatable support 62. The rotatable support 62 delimits an inner space 64 that is configured for receiving at least one part of a separator insert 11 therein. Thus, the inner space 64 is accessible via each of the first 71 and second 70 openings. Accordingly, the first 70 and second openings 71 are configured for fluid connections of the separator insert 11 to extend therethrough. See further with reference to Fig. 11 below.

[0104] Access to the inner space 64 is provided via a cap 72. Thus, the exchangeable separator insert 11 may be mounted in and removed from the inner space 64. The housing 66 comprises a lid 65 and in an open position of the lid 64, access is provided to the rotational support 62 16 inside the housing 66 e.g., for exchange of a separator insert 11.

[0105] The inner space 64 of the rotational support 62 is delimited at least in part by an inner surface 67. The separator insert 11 may have a same external shape to an extent that it fits inside the inner space 64. The separator insert 11 , when fitted in the inner space 64 abuts against at least part of the inner surface 67. Thus, the separator insert is supported by the inner space 26 of the rotational support 62.

[0106] According to alternative embodiments, the rotational support 62 may be provided with only the first opening 71 or only the second opening 70, in which case all fluid connections of the exchangeable separator insert 11 extend only through the relevant first 71 or second 70 opening.

[0107] In Fig. 11 , the exchangeable separator insert 11 is shown mounted in the rotational support 62 of the stationary frame 3. Part of the exchangeable separator insert 11 is received in the inner space 64 of the rotational support 62. In this embodiment, a fluid connection in the form of an inlet tube 12a for the liquid feed mixture to be separated as well as a fluid connection in the form of tube 12c for a separated liquid light phase extends through the axial lower opening 70 of the rotational support 62, whereas a single fluid connection in the form of tube 12b for a separated liquid heavy phase extends through the axial upper opening 71. These fluid connections are connected to channels in a lower mechanical seal 85 and an upper mechanical seal 86, respectively. These seals 85, 86 may form part of the separator insert 11 or may form part any other part of the single use portion 10 of the centrifugal separator 1. The separator insert 11 forms within itself a separation space in which a separation aid in the form of a stack of separation discs 19 is mounted.

[0108] During operation, liquid feed mixture to be separated is supplied via the inlet tube 12a into the separation space of the insert 11. Due to a density difference, the liquid feed mixture is separated into a liquid light phase and a liquid heavy phase. This separation is facilitated by the interspaces between the individual discs in the stack of separation discs 19. The liquid heavy phase may comprise particles, such as e.g. cells.

[0109] The separated liquid heavy phase is collected from the periphery of the separation space and is discharged via outlet tube 12b. Separated liquid light phase is instead forced radially inwardly between the separation discs 19 and is led out of the separator insert 11 to outlet tube 12c.

[0110] The exchangeable separator insert 11 may be exchanged for each new batch of liquid feed mixture which is to be separated. Alternatively, the exchangeable separator insert 11 may be exchanged for each new type of liquid feed mixture, which is to be separated.

[0111] In the above, the inventive concept has mainly been described with reference to a limited number of examples. However, as is readily appreciated by a person skilled in the art, other examples than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims

CLAIMS1. A centrifugal separator (1) for separating a liquid mixture into at least one separated liquid phase, said separator comprising a reusable portion (2) arranged for use in multiple separation processes and a single use portion (10) arranged for being replaced between separation processes, wherein said single use portion (10) comprises- a separator insert (11) in which the separation takes place, said insert (11) forming a preassembled interchangeable unit, and- at least one tube (12) arranged for transporting liquid mixture to said separator insert (11) and / or at least one separated phase from said separator insert (11); and wherein said reusable portion (2) comprises- a stationary frame (3) in which said separator insert is mounted;- a drive unit (4) arranged for rotating said separator insert (11) in relation to the stationary frame (3) around an axis of rotation (X); wherein the centrifugal separator (1) further comprises at least one sensor (20) for measuring a physical property of the liquid feed mixture or a separated liquid phase, said at least one sensor (20, 30) comprising- a sensing element (21 , 31) that is responsive for said physical property, and- a processing unit (22, 32) configured for converting the sensed physical property to an electrical variable; wherein at least said processing unit (22, 32) is arranged in the reusable portion (2) of the centrifugal separator (1).

2. A centrifugal separator (1) according to claim 1, wherein the sensing element (21 , 31 ) of the at least one sensor (20) is arranged in said single use portion (10) of the centrifugal separator (1).

3. A centrifugal separator (1) according to claim 2, wherein the sensing element (21 , 31) is a strain gauge element or a thermocouple element.

4. A centrifugal separator (1) according to claim 1 , wherein also said sensing element (21, 31) is arranged in said reusable portion (2) of the centrifugal separator (1).

5. A centrifugal separator (1) according to claim 4, wherein said sensor (20, 30) is a clamp-on sensor configured for being arranged on or interact with the at least one tube (12) for measuring a physical property of the liquid feed mixture or a separated liquid phase.

6. A centrifugal separator (1) according to claim 5, wherein said clamp-on sensor (20, 30) is a turbidity sensor and is configured for measuring the scattered light, back-scattered light or absorbed light from particles within said tube (12).

7. A centrifugal separator (1) according to claim 6, wherein the clamp-on sensor (20, 30) comprises a clamp-on element (24) for engaging with said tube (12), a transmitter (25) for emitting light into the tube (12) at the position of the clamp-on element (24) and a detector (26) for detecting the scattered light, back-scattered light or absorbed light.

8. A centrifugal separator (1) according to claim 7, wherein said tube (12) is a flexible tube and has an outer diameter (D) that is large enough so that the outer surfaces of the tube (12) are flattened out when being engaged with the clamp-on element (24).

9. A centrifugal separator (1) according to claim 5, wherein said clamp-on sensor (20, 30) is a pressure sensor and is configured for measuring the expansion force and / or the contraction force of said tube (12) and convert said force to a pressure within said tube (12).

10. A centrifugal separator (1) according to claim 9, wherein said clamp-on sensor (20, 30) comprises a load cell (40) for measuring said expansion force and / or contraction force and a clamp-on element (24) for fixating said tube (12) to the load cell (40).

11. A centrifugal separator (1) according to claim 10, wherein said processing unit (22, 32) is further configured for receiving information of said measuredexpansion force and / or contraction force and converting the measured force to a pressure value.

12. A centrifugal separator (1) according to claim 5, wherein said clamp-on sensor (20, 30) is a temperature sensor configured for measuring the temperature of the outside surface of the tube (12).

13. A centrifugal separator (1) according to claim 12, wherein said processing unit (22, 32) is further configured for receiving input of the measured temperature of the outside surface of the tube (12) and converting the received input to a value representing the temperature of the liquid within the tube (12).

14. A centrifugal separator (1) according to claim 12 or 13, wherein said clampon sensor (20, 30) comprises a clamp-on element (24) for fixating the sensor (20) to the tube (12) and a detector (50) for measuring the radiation from the tube.

15. A centrifugal separator (1) according to claim 14, wherein said detector (50) is an infrared (IR) detector.

Images