CA-3172329-C - A CENTRIFUGAL SEPARATOR FOR SEPARATING A LIQUID MIXTURE

Abstract

The present invention provides a separation system for separating a liquid mixture comprising a centrifugal separator, the centrifugal separator comprising: a stationary frame; a rotatable assembly and a drive unit for rotating the rotatable assembly around an axis of rotation; a feed inlet for receiving a liquid mixture to be separated; a first liquid outlet for discharge of a separated liquid light phase; and a second liquid outlet for discharge of a liquid heavy phase. The rotatable assembly comprises a rotor casing enclosing a separation space in which a stack of separation discs is arranged to rotate around a vertical axis of rotation, wherein the separation space receives liquid mixture from said feed inlet. The separation system further comprises a container arranged downstream of said first and/or second liquid outlet for receiving discharged liquid phase, and a scale for measuring the weight of discharged liquid phase in said container.

Inventors

• Per-Gustaf LARSSON

Assignees

• ALFA LAVAL CORPORATE AB

Dates

Publication Date

20260505

Application Date

20210317

Priority Date

20200326

Claims (17)

1. CLAIMS: 1. A separation system for separating a liquid mixture comprising a centrifugal separator, wherein the centrifugal separator comprises: a stationary frame; a rotatable assembly and a drive unit for rotating the rotatable assembly relative the frame around an axis of rotation; a feed inlet for receiving a liquid mixture to be separated, a first liquid outlet for discharge of a separated liquid light phase and a second liquid outlet for discharge of a liquid heavy phase having a density that is higher than said liquid light phase; wherein the rotatable assembly comprises a rotor casing enclosing a separation space in which a stack of separation discs is arranged to rotate around said axis of rotation, wherein the separation space is arranged for receiving liquid mixture from said feed inlet, wherein the rotatable assembly comprises an exchangeable separation insert and a rotatable member; said insert comprising said rotor casing and being supported by said rotatable member; and wherein the separation system further comprises: a container arranged downstream of said first and/or second liquid outlet of the centrifugal separator and arranged for receiving discharged liquid phase; a scale for measuring a weight of the discharged liquid phase contained in said container; and a control unit configured for determining the weight increase of said container as a function of time; wherein the container is suspended in the scale, and wherein the control unit is further configured for determining a flow rate of the discharged liquid phase based on the measured weight increase of said container as a function of time.
2. 2. The separation system according to claim 1, further comprising a tank for receiving the discharged liquid phase being emptied from the container.
3. 3. The separation system according to claim 1 or 2, wherein said container comprises a container inlet for receiving said discharged liquid phase and a container outlet for emptying the liquid phase from the container; and wherein the separation system further comprises valve means for regulating the flow of the discharged liquid phase being emptied from the container.
4. 4. The separation system according to claim 3, wherein the control unit is further configured to control said valve means, and further configured to close said valve means during said determining of the weight increase of said container as a function of time.
5. 5. The separation system according to claim 4, wherein the control unit is further configured to open said valve means such that an outlet flow of the discharged liquid phase from said container is higher than an inlet flow of the discharged liquid phase to said container; thereby emptying said container.
6. 6. The separation system according to claim 5, wherein the control unit is configured to switch between closing the valve means and opening the valve means such that said container is filled and emptied in cycles.
7. 7. The separation system according to any one of claims 1 to 6, wherein the container is arranged downstream of the first liquid outlet.
8. 8. The separation system according to any one of claims 1 to 7, wherein the separation system is free of flow sensors arranged downstream of the first liquid outlet and the second liquid outlet at which said container is arranged.
9. 9. A method for determining a flow rate of a liquid phase being discharged from a centrifugal separator, comprising the steps of: a) providing the separation system according to any one of claims 1 to 8; b) supplying feed to said feed inlet and discharging the separated liquid light phase from said first liquid outlet and discharging the separated liquid heavy phase from said second liquid outlet; c) measuring a weight increase of said container as a function of time; and d) determining a flow rate of said separated liquid light phase and/or said separated liquid heavy phase being discharged to said container based on the measured weight increase of step c).
10. 10. The method according to claim 9, wherein step c) further comprises step c1) of stopping a flow of the discharged liquid phase out from said container during said measuring of the weight increase of said container as a function of time.
11. 11. The method according to claim 10, wherein step c) further comprises step c2) of starting the flow of the discharged liquid phase out from said container, thereby emptying said container after said measuring of the weight increase of said container as a function of time.
12. 12. The method according to claim 11, wherein step c) comprises repeating steps c1) and c2).
13. 13. A method for determining a flow rate of a liquid phase being discharged from a centrifugal separator, comprising the steps of: a) providing the separation system according to any one of claims 1 to 7; b) supplying feed to said feed inlet and discharging the separated liquid light phase from said first liquid outlet and discharging the separated liquid heavy phase from said second liquid outlet; c) measuring a weight increase of said container as a function of time; and d) determining a flow rate of said separated liquid light phase and/or said separated liquid heavy phase being discharged to said container based on the measured weight increase of step c).
14. 14. The method according to claim 13, wherein step c) further comprises step c1) of stopping a flow of discharged liquid phase out from said container during said measuring of the weight increase of said container as a function of time. 5
15. 15. The method according to claim 14, wherein step c) further comprises step c2) of starting the flow of the discharged liquid phase out from said container, thereby emptying said container after said measuring of the weight increase of said container as a function of time. 10
16. 16. The method according to claim 15, wherein step c) comprises repeating steps c1) and c2).
17. 17. The method according to any one of claims 13 to 16, further comprising adjusting a flow sensor arranged downstream of a same liquid outlet at which said 15 container is arranged based on the determined flow of said liquid phase in step d).

Description

1 A CENTRIFUGAL SEPARATOR FOR SEPARATING A LIQUID MIXTURE Technical field The present inventive concept relates to the field of centrifugal separators. More particularly it relates to a centrifugal separator method for measuring the liquid flow of a separated phase from a centrifugal separator. Background 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 the periphery and close to the rotational axis, respectively. WO 2015/181177 discloses a separator for the centrifugal processing of a pharmaceutical product, such as a fermentation broth. The separator comprises a rotatable outer drum and an exchangeable inner drum arranged in the outer drum. The inner drum comprises means for clarifying the flowable product. The outer drum is driven via drive spindle by a motor arranged below the outer drum. The inner drum extends vertically upwardly through the outer drum which fluid connections arranged at an upper end of the separator. The traditional way of measuring a liquid flow of the separated liquid phase from a centrifugal separator is using a flow sensor. Flow sensors are expensive in general and it may be difficult to select an appropriate flow sensor for a specific application since flow sensors may depend on several different measuring principles, all with their own advantages and disadvantages. Measurement errors normally occur if one wants to measure different liquids with the same flow sensor or if the temperature or liquid composition varies over time. There is thus a need in the art for improved methods for methods for measuring the flow of a separated liquid phase from a centrifugal separator. Summary 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 separator and a method for determining the flow rate of a discharged liquid phase. As a first aspect of the invention, there is provided a separation system for separating a liquid mixture comprising a centrifugal separator. The centrifugal 5 separator comprises a stationary frame, a rotatable assembly and a drive unit for rotating the rotatable assembly relative the frame around an axis of rotation; a feed inlet or receiving a liquid mixture to be separated, 1 0 a first liquid outlet for discharge of a separated liquid light phase and a second liquid outlet for discharge of a liquid heavy phase having a density that is higher than said liquid light phase; wherein the rotatable assembly comprises a rotor casing enclosing a separation space in which a stack of separation discs is arranged to rotate around 15 the axis of rotation, wherein the separation space is arranged for receiving liquid mixture from said feed inlet. The separation system further comprises a container arranged downstream of said first and/or second liquid outlet of the centrifugal separator and arranged for receiving discharged liquid phase, and 20 a scale for measuring a weight of discharged liquid phase contained in said container. The stationary frame of the centrifugal separator is a non-rotating part, and the rotatable assembly is supported by the frame, e.g. by means of at least one bearing, for example a ball bearing. 25 The centrifugal separator further comprises a drive unit arranged for rotating the rotatable assembly and may comprise an electrical motor or be arranged to rotate the rotatable assembly by a suitable transmission, such as a belt or a gear transmission. Thus, the drive unit may be arranged to drive the rotatable assembly directly or indirectly via a transmission. 30 The rotatable assembly comprises a rotor casing in which the separation takes place. The rotor casing encloses a separation space in which the separation of the fluid mixture, such as a cell culture mixture, takes place. The rotor casing may be a solid rotor casing and be free of any further outlets for separated phases. Thus, the solid rotor casing 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. However, in embodiments, the rotor casing comprises peripheral ports for intermittent or continuous discharge of a separated phase from the periphery of the separation space. 5 The feed inlet is for receiving the liquid mixture to be separated and for guiding the feed to the separation space. The separation space comprises a stack of separation discs arranged centrally around the axis of rotation. The stack may comprise frustoconical separation