System for separating liquid feed mixture

Abstract

The invention provides a system (1) for separating at least a first liquid phase from a liquid feed mixture. The system (1) comprises a centrifugal separator (2) comprising: a centrifugal bowl (4) arranged to rotate about an axis of rotation (X) and in which separation of the liquid feed mixture takes place; an inlet (90) for receiving the liquid feed mixture; and a first liquid outlet (22) for discharging the first liquid phase. The first liquid outlet (22) is hermetically sealed and is free of any dedicated means for converting kinetic energy of the first liquid phase into a pressure flow of the first liquid phase. The system (1) further comprises pressure generating means (73) for supplying the liquid feed mixture to the inlet (90) of the centrifugal separator (2), and the system (1) is configured such that the pressure generating means (73) is a primary flow regulating means arranged for generating the outlet pressure required to deliver the first liquid phase from the first liquid outlet (22).

Description

Technical Field

[0001] The present invention relates to the field of centrifugal separators and more particularly to a system comprising a centrifugal separator for separating at least a first liquid phase from a liquid feed mixture. Background Art

[0002] Centrifugal separators are generally used for the separation of liquids and / or for the separation of solids from liquids. During operation, the liquid mixture to be separated is introduced into a rotating centrifugal bowl, and heavy particles or denser liquids (such as water) accumulate at the periphery of the rotating bowl, while less dense liquids accumulate closer to the central axis of rotation. This allows the separated components to be collected, for example through different outlets arranged at the periphery and close to the axis of rotation, respectively.

[0003] A mechanical seal may be arranged between the fixed part of the centrifugal separator and the centrifugal bowl for sealing the fluid path extending therebetween. In a centrifugal separator with hermetic sealing at the inlet and liquid outlet, the separated liquid phase may be pumped out under pressure by a pump which converts the kinetic energy of the separated phase into pressure. Such a pump may be a pump impeller or a paring device, such as a paring tray. In addition, these devices require a controlled back pressure for optimal functionality.

[0004] In order to produce a process fluid flow through such a gas-tight separator, an inlet pressure may be provided to overcome the pressure drop in the separator. The inlet pressure is typically provided by a feed pump arranged to deliver the feed mixture to be separated to the centrifugal separator. Examples of gas-tightly sealed centrifugal separators are disclosed in documents EP2868210 and EP3769846.

[0005] However, there is still a need for improvements in centrifugal separators having at least one gas-tight outlet.There is also a greater need in the art to provide separation systems that require less energy for the separation process. Summary of the invention

[0006] It is an object of the present invention to at least partially overcome one or more limitations of the prior art.It is, among other things, an object of the present invention to provide a system for separating a liquid feed mixture with reduced energy consumption.

[0007] As a first aspect of the present invention, there is provided a system for separating at least a first liquid phase from a liquid feed mixture, the system comprising:

[0008] A centrifugal separator comprising

[0009] a centrifugal bowl arranged to rotate about an axis of rotation (X) and in which separation of the liquid feed mixture takes place,

[0010] an inlet for receiving the liquid feed mixture, and

[0011] a first liquid outlet for discharging the first liquid phase, wherein the first liquid outlet is hermetically sealed and is devoid of any dedicated means for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase,

[0012] And wherein the system also includes

[0013] pressure generating means for supplying the liquid feed mixture to the inlet of the centrifugal separator, and

[0014] Therein, the system is configured such that the pressure generating device is a primary flow regulating device arranged to generate an outlet pressure required to deliver the first liquid phase from the first liquid outlet.

[0015] As used herein, the term "axially" refers to a direction parallel to the axis of rotation (X). Thus, relative terms such as "above", "upper", "top", "below", "lower" and "bottom" refer to relative positions along the axis of rotation (X). Correspondingly, the term "radially" refers to a direction extending radially from the axis of rotation (X) and therefore perpendicular to the axis of rotation (X). Thus, a "radially inner position" refers to a position closer to the axis of rotation (X) than a "radially outer position". A "radial plane" is a plane extending in the radial direction and having a normal extending in the axial direction. Similarly, an "axial plane" is a plane extending in the axial direction and having a normal extending in the radial direction.

[0016] The "dedicated device for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase" may be a product discharge pump for discharging the first liquid phase. Such a device is usually arranged in the outlet chamber of the centrifugal bowl, such as in a water distribution chamber. The product discharge pump may be a water distribution device, such as a fixed water distribution plate, as known in the art. The product discharge pump may also be a centrifugal pump, such as a pump impeller rotating with the centrifugal bowl. The centrifugal pump may also be a stationary pump.

[0017] "Dedicated means for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase" may be a device that has as its main function the conversion of kinetic energy into a pressure flow. As an example, the "dedicated means" may not form part of the outlet seal. Thus, some parts of the outlet seal, such as a mechanical seal, may convert a small part of the kinetic energy into a pressure flow of the liquid phase. However, the main purpose of such a part of the seal is of course to assist the sealing function of the seal and is therefore not a "dedicated means" according to the first aspect.

[0018] The first liquid outlet is in fluid communication with the separation space of the centrifugal bowl. The first liquid outlet forms a fluid path out of the centrifugal bowl. The first liquid outlet is hermetically sealed. The hermetically sealed outlet can be sealed using a liquid seal (liquid-tight seal) or a mechanical seal. The mechanically sealed hermetic outlet is sealed from the periphery of the rotor and is arranged to be filled with liquid product during operation. Therefore, compared with a separator having a paired disk at the liquid outlet, a mechanically hermetically sealed separator has no liquid-air interface at the outlet.

[0019] In an embodiment, the first liquid outlet is mechanically hermetically sealed.

[0020] The mechanical seal of the mechanically sealed liquid outlet may be a double mechanical seal, i.e. comprising a rotatable part and a fixed part, between which a sealing interface is formed. The sealing interface may extend in a radial plane. The fixed part may be connected to a fixed outlet pipe, while the rotatable part of the seal may be attached to the centrifugal bowl.

[0021] The pressure generating means may be a liquid feed pump. However, the "pressure generating means" may also be realized by supplying the liquid feed mixture from a height above the centrifugal separator. Thus, the system may comprise a tank for the liquid feed mixture to be separated, and such a tank may be arranged at a height above the centrifugal separator in order to generate the required inlet pressure. Thus, the pressure generating means may be "built-in" to the arrangement of the components of the system.

[0022] “The pressure generating device is a main flow regulating device arranged to generate the outlet pressure required for delivering the first liquid phase from the first liquid outlet” means a pressure generating device that generates the maximum outlet pressure for delivering the first liquid phase from the first liquid outlet

[0023] In an embodiment, the pressure generating device is the only flow regulating device arranged to generate the outlet pressure required for delivering the first liquid phase from the first liquid outlet.

[0024] However, the centrifugal separator may be designed such that the centrifugal bowl itself generates a first liquid phase flow from the first liquid outlet during rotation. This may be the case, for example, if the first liquid outlet is arranged at a larger radius than the inlet, such as if the inlet is arranged at the axis of rotation (X) and the first liquid outlet is arranged at a radius from the axis of rotation (X).

[0025] A first aspect of the invention is based on the recognition that a gas-tight outlet can be designed without dedicated means for converting the kinetic energy of the separated liquid phase into a pressure flow, so that, for example, a liquid feed pump is the primary or only means for providing sufficient pressure to the separated liquid phase to flow out of the separator. The pressure generating means (such as a liquid feed pump) can be designed in a more energy efficient manner than conventional means for converting kinetic energy into a pressure flow (such as a water distribution plate or a pump wheel). Thus, the centrifugal separator can be free of any internal means dedicated to generating an outlet pressure for the first liquid phase, other than the rotating centrifugal bowl itself.

[0026] Moreover, the inventors have realized that with such a design, no pressure regulating valve is needed downstream of the outlet to control the back pressure. Such a pressure regulating valve usually causes pressure drop and energy loss. In other words, the first aspect allows the separation system to have no pressure regulating valve downstream of the outlet and thus reduce energy consumption.

[0027] In an embodiment of the first aspect, the centrifugal separator has no other liquid outlet for discharging the further separated liquid phase. Therefore, the centrifugal separator can be a clarifier separator. A clarifier is a centrifugal separator used for solid-liquid separation, which removes solids, such as particles, sediments, from the liquid feed mixture. In doing so, the process liquid becomes clear. Therefore, the centrifugal separator can have a single liquid outlet for the separated liquid phase.

[0028] However, the centrifugal separator may also comprise at least one slurry outlet for the separated solid phase.Such a slurry outlet may be arranged at the periphery of the centrifugal bowl.

[0029] Thus, the centrifugal separator may be arranged to separate the liquid feed mixture into a liquid light phase and a mud phase.

[0030] The at least one slurry outlet may be in the form of a set of open nozzles arranged for continuously discharging the separated slurry phase.Such nozzles may be used when the slurry content of the liquid feed mixture is high.

[0031] Alternatively, the at least one slurry outlet is in the form of a group of intermittently openable outlets. Thus, such outlets may be in the form of a plurality of peripheral ports extending from the centrifuge bowl to the space surrounding the centrifuge bowl exterior. The peripheral ports may be intermittently opened during short periods of time, for example in the order of a fraction of a second, and allow for full or partial discharge of slurry from the centrifuge bowl, using conventional intermittent discharge systems as known in the art.

[0032] As an example, when the centrifugal separator has no other liquid outlet for discharging the further separated liquid phase, the system may also include a tank downstream of the first liquid outlet. The system may then be without any pressure regulating valve between the first liquid outlet and the tank. Such a pressure regulating valve is arranged to generate a back pressure to the first liquid outlet.

[0033] It is usually necessary to have a pressure regulating valve downstream of the liquid outlet, such as a flow regulating valve or a flow control valve, to provide a controlled back pressure for optimal functionality of the centrifugal separator. In almost every installation the back pressure is greater than that required for conveying the separated liquid phase downstream. This pressure drop is an energy loss and in most cases does not have any other benefit. Therefore, the inventors realized that by adopting a gas-tight outlet design without any special device for converting the kinetic energy of the separated liquid phase into a pressure flow of the first liquid phase, the clarifier separator does not need additional back pressure.

[0034] Pressure regulating valves are typically arranged to control the flow of the liquid phase by varying the size of the flow passage.

[0035] Check valves cannot be used as pressure regulating valves in this way.

[0036] The tank may be arranged to hold the discharged first liquid phase for a period of time before its use downstream. Thus, the tank may be a storage tank.

[0037] However, the system may include other process equipment between the centrifugal separator and the tank, such as a heat exchanger, etc. Therefore, the system may also be without any pressure regulating valve between such other process equipment and the tank.

[0038] As another example, the centrifugal separator may be arranged such that the liquid feed mixture enters the centrifugal bowl axially from the top. The liquid feed mixture may then enter the centrifugal bowl via a fixed inlet pipe extending into the bowl. The liquid feed mixture may enter the centrifugal separator at the axis of rotation (X) and the first liquid outlet may be arranged such that the first liquid phase is discharged at a radial distance from the axis of rotation (X). Moreover, the first liquid outlet may also be arranged axially at the top of the centrifugal bowl.

[0039] As another example, the inlet can also be hermetically sealed. As with the first liquid outlet, the inlet can be sealed by a liquid-tight seal or a mechanical seal. The mechanically hermetically sealed inlet is sealed from the periphery of the rotor and is arranged to be filled with a fluid product during operation. Thus, the inlet and the separation space of the centrifugal bowl are connected in a pressure-connected manner.

[0040] As an example, the inlet and the first liquid outlet may be hermetically sealed by at least one mechanical seal.As an example, the sealing interfaces of the at least one mechanical seal may be arranged in the same radial plane.

[0041] The at least one mechanical seal may have a fixing portion that is releasable from the centrifugal bowl in the same single unit. This may facilitate installation and maintenance of the at least one mechanical seal.

[0042] The inlet and the first liquid outlet may be hermetically sealed by a single mechanical seal whose sealing interface is in the same radial plane.The single mechanical seal may comprise a rotatable part (such as a wear ring) and a fixed part (such as a sealing ring) forming a sealing interface between them.

[0043] A sealing assembly and a fixed liquid passage device arranged at the top of the centrifugal separator can be used to seal the inlet and the first liquid outlet. Such a sealing assembly can form an interface between the centrifugal bowl and the fixed liquid passage device. The first liquid path can extend concentrically with the rotation axis between the fixed liquid passage device and the bowl, and the second liquid path can extend radially outside the first liquid path between the fixed liquid passage device and the bowl. The fixed liquid passage device can be releasably connected to the frame of the centrifugal separator. The sealing assembly may include a first seal between the first liquid path and the second liquid path, the first seal extending concentrically with the rotation axis and around the rotation axis, and a second seal between the second liquid path and the space radially outside the second liquid path, the second seal extending concentrically with the rotation axis and around the rotation axis. The first seal may include a first sealing component arranged in the fixed liquid passage device and a first sealing surface arranged in the bowl, the first sealing component having a first axial end face, and the first axial end face and the first sealing surface are configured to be positioned in a sealed abutment manner. The second seal may include a second sealing member arranged in the fixed liquid passage means and a second sealing surface arranged in the bowl, the second sealing member having a second axial end face, the second axial end face and the second sealing surface being configured to be positioned in sealing abutment. The second sealing member is separate from the first sealing member, and the first and second sealing members are separable from the first and second sealing surfaces and released from the housing together with the fixed liquid passage means.

[0044] However, the inlet and the first liquid outlet may also be sealed by two different mechanical seals whose sealing interfaces are in different radial planes.

[0045] As another example, the centrifugal separator may be arranged such that the liquid feed mixture enters the centrifugal bowl axially from the bottom. Thus, the clarifier separator may be a bottom-fed centrifugal separator. The centrifugal separator may then be arranged such that the liquid feed mixture enters the centrifugal bowl from the bottom via the drive spindle of the centrifugal bowl, i.e. at the axis of rotation (X). For such a design, the first liquid outlet may be arranged at the top of the centrifugal bowl, such as at the axis of rotation (X) or at a radial distance from the axis of rotation (X).

[0046] In an embodiment of the first aspect, the centrifugal separator comprises a second liquid outlet for discharging a second liquid phase having a higher density than the first liquid.

[0047] Thus, the first liquid phase may be a liquid light phase and the second liquid phase may be a liquid heavy phase. "Liquid light phase" refers to a separated liquid having a density lower than the density of the "liquid heavy phase". Thus, the liquid feed mixture may be separated into at least a liquid light phase and a liquid heavy phase. The solid phase may also be separated in a centrifugal separator. Thus, the centrifugal separator may be arranged to separate the liquid feed mixture into a liquid light phase, a liquid heavy phase and a solid phase, i.e. a slurry phase, and therefore, the centrifugal separator may comprise a first liquid outlet for the liquid light phase, a second liquid outlet for the light and heavy phases and a slurry outlet for the separated solids.

[0048] The at least one slurry outlet may be in the form of a set of open nozzles arranged for continuously discharging the separated slurry phase.Such nozzles may be used when the slurry content of the liquid feed mixture is high.

[0049] Alternatively, the at least one slurry outlet is in the form of a group of intermittently openable outlets. Thus, such outlets may be in the form of a plurality of peripheral ports extending from the centrifuge bowl to the surrounding space outside the centrifuge bowl. The peripheral ports may be intermittently opened during short periods of time, for example in the order of a fraction of a second, and allow the slurry to be fully or partially discharged from the centrifuge bowl using conventional intermittent discharge systems as known in the art.

[0050] Thus, a centrifugal separator can be a purifier for liquid-liquid-solid separation, which separates two liquids of different densities and solids from each other. With a purifier, the light liquid phase is typically the bulk intended to be cleaned. A centrifugal separator can also be a concentrator, which is arranged to separate three different phases, two liquid phases of different densities and one solid phase and clean the densest / heaviest liquid phase.

[0051] As an example, the second liquid outlet may also be hermetically sealed and without any dedicated means for converting the kinetic energy of the second liquid phase into a pressure flow of the second liquid phase.The hermetic seal may be a hermetic seal as discussed above with respect to the first liquid outlet, such as a mechanical seal.

[0052] For a centrifugal separator comprising a second liquid outlet for discharging a second liquid phase having a higher density than the first liquid, a pressure regulating device may be required downstream of the two liquid outlets for backpressure control, i.e. for controlling the interphase level between the phases in the centrifugal bowl, rather than for liquid transport. The inventors have realised that such a pressure regulating device need not be a flow regulating valve. Therefore, in an example, the system comprises a first pressure regulating device downstream of the first liquid outlet and a second pressure regulating device downstream of the second liquid outlet; wherein the first and second pressure regulating devices are arranged for regulating the interface between the liquid phases in the centrifugal bowl and are devices other than pressure regulating valves.

[0053] Such a pressure regulating device other than a flow regulating valve may be, for example, a positive displacement pump, such as a peristaltic pump.

[0054] Furthermore, according to an embodiment, the second liquid outlet is an open outlet formed by an annular gravity disk.

[0055] Thus, the open outlet and the gravity disc may form an overflow outlet for the separated second liquid phase.The gravity disc may be an annular component which acts as a weir and determines the radial position of the overflow of the separated second liquid phase to the open outlet.

[0056] Therefore, the second liquid outlet cannot be hermetically sealed.

[0057] As discussed above with respect to the clarifier separator, when the centrifugal separator comprises a second liquid outlet, the centrifugal separator may also be arranged so that the liquid feed mixture enters the centrifuge bowl axially from the top. For this purpose, the centrifugal separator may comprise a fixed liquid inlet pipe extending into the centrifuge bowl.

[0058] Furthermore, as an example, the liquid feed mixture may then enter the centrifugal separator at the axis of rotation (X), and the first and second liquid outlets may be arranged such that the first and second liquid phases are discharged at different radial distances from the axis of rotation (X). The first liquid outlet may be arranged at a shorter radial distance than the second liquid outlet. However, the opposite is also possible, i.e. the second liquid outlet is arranged at a shorter radial distance than the first liquid outlet.

[0059] The first and second liquid outlets may be arranged axially at an upper portion of the centrifugal bowl.Thus, the inlet and the two liquid outlets may be arranged at an axial upper portion of the centrifugal bowl.

[0060] As an example, when the centrifugal separator includes a second liquid outlet, the inlet may also be hermetically sealed as discussed above. Thus, the centrifugal separator may have a hermetically sealed inlet and a first hermetically sealed first liquid outlet. The second liquid outlet may then be an open outlet or a hermetically sealed second liquid outlet.

[0061] As an example, the inlet and the first and second liquid outlets may all be sealed by at least one mechanical seal, and wherein sealing surfaces of the at least one mechanical seal may be arranged in a same radial plane.

[0062] The at least one mechanical seal may be a single seal or two or more separate mechanical seals.

[0063] Moreover, as discussed above with respect to the clarifying separator, when the centrifugal separator comprises a second liquid outlet, the centrifugal separator may also be arranged such that the liquid feed mixture enters the centrifuge bowl axially from the bottom. The liquid feed mixture may then enter the centrifuge bowl via a rotating shaft (spindle) for transmitting torque to the centrifuge bowl. Thus, the liquid feed mixture may enter at the axis of rotation (X), the liquid light phase may be discharged at the axis of rotation (X) and the liquid heavy phase may be discharged at a radial distance from the axis of rotation (X).

[0064] All types of centrifugal separators used in the system of the first aspect of the invention may be centrifugal separators arranged for multiple use. Thus, the centrifugal bowl may be a stainless steel bowl. Thus, the centrifugal bowl may be arranged for multiple use. Furthermore, the centrifugal bowl may include a slurry outlet at the periphery of the bowl for intermittently or continuously discharging the separated slurry phase.

[0065] The centrifugal separator of the system of the first aspect of the present invention generally comprises a frame, i.e. a non-rotating part, and the centrifugal bowl can be supported by the frame through at least one bearing device. The centrifugal bowl is generally supported by a main shaft, i.e. a rotating shaft, and can therefore be mounted to rotate with the main shaft. The axis of rotation (X) can extend vertically. Therefore, the centrifugal bowl can be arranged so that the centrifugal bowl is supported by the main shaft at one of its ends (such as at the top of the main shaft). The centrifugal separator may also include a drive component for rotating the main shaft and the centrifugal bowl. The drive component may include an electric motor or be arranged beside the main shaft and rotate the main shaft and the centrifugal bowl through a suitable transmission device (such as a belt or gear drive).

[0066] The centrifugal bowl comprises a separation space. In such a separation space, a stack of separation discs is usually arranged. The separation of the liquid feed mixture occurs in the separation space. The separation discs can be made of metal, for example. In addition, the separation discs can be frustoconical separation discs, i.e., separation surfaces having frustoconical portions forming the separation discs. The separation discs are coaxially arranged spaced apart from each other around the axis of rotation (X) so that a passage is formed between every two adjacent separation discs. The separation discs in the disc stack can be arranged so that the liquid mixture is introduced into the disc stack from a radially outer position. Separation then occurs in the passage between every two adjacent separation discs of the stack.

[0067] The centrifugal separator also includes an inlet for the liquid mixture to be separated (liquid feed mixture). The inlet may include a central inlet chamber from which the liquid feed mixture is directed to the separation space, for example via a channel below or inside a distributor as known in the art. The separation disc stack is usually placed on top of such a distributor.

[0068] As a second aspect of the present invention, there is provided a method for separating a liquid feed mixture in a system according to the first aspect, the method comprising the following steps:

[0069] a) introducing a liquid feed mixture into a centrifugal separator using a liquid feed pump;

[0070] b) continuously discharging the first liquid phase from a first liquid outlet of the centrifugal separator;

[0071] This aspect may generally present the same or corresponding advantages as the previous aspect. The effects and features of this second aspect are generally similar to those described above in conjunction with the first aspect. The embodiments mentioned with respect to the first aspect are generally compatible with the second aspect of the invention.

[0072] The method may also include the following steps

[0073] c) continuously discharging the second liquid phase from the second liquid outlet of the centrifugal separator.

[0074] The method may also include the following steps

[0075] d) intermittently discharging the slurry phase from the centrifugal separator.

[0076] The inventive concepts disclosed herein can be used in separating a variety of different feed mixtures. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The above and additional objects, features and advantages of the inventive concept will be better understood through the following illustrative and non-limiting detailed description with reference to the accompanying drawings. Unless otherwise specified, similar reference numerals will be used in the drawings to represent similar elements.

[0078] Figure 1 is a schematic diagram of a prior art system for separating a liquid feed mixture.

[0079] Figure 2 is a schematic diagram of a system according to the present disclosure in which the centrifugal separator is a top feed clarifier.

[0080] Figure 3 is a schematic diagram of a system according to the present disclosure in which the centrifugal separator is a bottom feed clarifier.

[0081] Figure 4 is a schematic diagram of a system according to the present disclosure in which the centrifugal separator is top fed and has a second liquid outlet.

[0082] Figure 5 is a schematic diagram of a system according to the present disclosure in which the centrifugal separator is bottom fed and has a second liquid outlet.

[0083] Figure 6 yes Figure 2 Detailed view of a centrifugal separator of a system in cross section.

[0084] Figure 7 It further shows Figure 6 Details of the inlet and outlet of a centrifugal separator.

[0085] Figure 8 A perspective view of a single sealing element of a centrifugal separator is shown.

[0086] Fig. 9 A method of separating a liquid feed mixture is schematically shown. DETAILED DESCRIPTION

[0087] The system of the present invention will be further illustrated by the following description with reference to the accompanying drawings.

[0088] Figure 1 A prior art system 1 for separating a liquid feed mixture into a clarified first liquid phase is shown. Thus, the centrifugal separator 2 of the system 1 is a clarifier centrifugal separator arranged for separating a first liquid phase and a mud phase from a liquid feed mixture. The liquid feed mixture enters the centrifugal bowl via a fixed inlet pipe 80 using a liquid feed pump 73. The clarified first liquid phase is discharged in a fixed outlet pipe 81, while the mud phase is intermittently ejected via a group of mud outlets arranged at the periphery of the centrifugal bowl, as is known in the art. The separated mud is collected in a mud tank 70 and the separated first liquid phase is collected in a tank 72 arranged downstream of the first liquid outlet of the centrifugal separator. The first liquid outlet is a mechanically hermetically sealed outlet and is arranged in the centrifugal bowl of the centrifugal separator. The inlet of the centrifugal separator 2 is also mechanically hermetically sealed. In order to generate a process fluid flow through the centrifugal separator 2, an inlet pressure must be provided to overcome the pressure drop in the centrifugal separator 2. The inlet pressure is generated by the liquid feed pump 73.

[0089] During separation in the centrifugal bowl, the separated first liquid phase moves towards the center of the centrifugal bowl and is then pumped out under pressure by a built-in pump wheel, which can rotate with the centrifugal bowl in the first liquid outlet to obtain the desired outlet pressure.

[0090] Thus, the inlet pressure generated by the feed pump 73 is sufficient to overcome the flow resistance through the centrifugal separator to the internal pump wheel at the first liquid outlet. The size of the pump wheel or pump impeller can be sized to suit the outlet pressure requirement.

[0091] Therefore, in Figure 1In the prior art system, the hermetically sealed first liquid outlet comprises a built-in pump wheel arranged to convert rotational energy into a pressure flow of the first liquid phase. The built-in pump wheel is therefore a special device for converting the kinetic energy of the separated liquid phase into a pressure flow. In addition, the centrifugal separator 2 requires a controlled back pressure for optimal functionality. Such a back pressure is generated using a regulating valve 71 arranged downstream of the first liquid outlet, i.e. between the first liquid outlet and the tank 72. Therefore, the regulating valve 71 is arranged to provide pressure in the fixed outlet pipe 81. In Figure 1 Typical pressure values ​​(in psi) in different parts of the system are shown in .

[0092] Therefore, the inventors have realized that the regulating valve 71 and the pump wheel at the liquid outlet used in the prior art system are not necessary. The back pressure generated is greater than that required to transport the separated liquid phase downstream. Therefore, this pressure drop is a loss of energy and in most cases does not have any other benefits.

[0093] exist Figure 2 1 shows a system for separating at least a first liquid phase from a liquid feed mixture according to the present disclosure. The system 1 includes a clarifier centrifugal separator 2. The centrifugal separator 2 will be hereinafter referred to as Figure 5 Let's discuss in more detail. The separator 2 comprises at least: a centrifugal bowl arranged to rotate about an axis of rotation (X) and in which separation of the liquid feed mixture occurs; and an inlet for receiving the liquid feed mixture. The liquid feed mixture enters the centrifugal bowl axially from the top via a fixed pipe 80.

[0094] Furthermore, a first and single liquid outlet for discharging the first liquid phase is hermetically sealed and arranged at the top of the centrifugal bowl. The centrifugal bowl is designed such that the liquid feed mixture enters the bowl at the axis of rotation and leaves the bowl via the first liquid outlet at a radial distance from the axis of rotation. Figure 1 As in the prior art systems, the mud is ejected into the mud tank 70.

[0095] The first liquid outlet is free of any dedicated means, such as a pump wheel, for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase. The system 1 further comprises a liquid feed pump 73 for supplying the liquid feed mixture to the inlet of the centrifugal separator. Due to the arrangement of the first liquid outlet, the liquid feed pump 73 is the main or only flow regulating device, which is arranged to generate the outlet pressure required to transport the first liquid phase from the first liquid outlet downstream via the fixed pipe 81 to the tank 72. Without any water distribution plate or pump wheel, no additional back pressure is required. Therefore, with Figure 1 Compared with the prior art system, the regulating valve ( Figure 1The valve 71 of the first liquid outlet is provided. This greatly reduces the energy consumption of the system. Therefore, the system 1 does not have any flow regulating valve between the first liquid outlet and the tank 72.

[0096] like Figure 3 The system 1 shown in Figure 2 The system is basically the same as that of the present invention. However, in this arrangement, the centrifugal separator 2 is a bottom feed centrifugal separator, meaning that the liquid feed mixture enters the centrifugal bowl axially from the bottom at the axis of rotation. Also in this design, the liquid outlet for the clarified liquid phase is arranged at the top of the centrifugal bowl and there is no special device, such as a pump wheel, for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase. A regulating valve is also not required downstream of the first liquid outlet. In the bottom feed design, the clarified liquid phase can also be discharged at the axis of rotation, i.e., the first liquid outlet for the separated liquid phase is arranged so that the separated liquid phase is discharged at the axis of rotation.

[0097] Figure 4 Another embodiment of a system according to the present disclosure is shown. Figure 4 In the system 1 shown in FIG. 1 , the liquid feed mixture supplied via the liquid feed pump 73 in the fixed pipe 80 is separated into a first liquid phase and a second liquid phase in the centrifugal separator 2. Therefore, the centrifugal separator 1 includes a second liquid outlet for discharging the second liquid phase having a higher density than the first liquid. The slurry phase is discharged to the tank 70 as in the previous example.

[0098] exist Figure 4 In the design of , the second liquid outlet is an open outlet formed by an annular gravity disk. The second liquid outlet is therefore a non-hermetically sealed overflow outlet. The separated liquid heavy phase thus flows out through this outlet into the fixed pipe 82. The liquid heavy phase can be pumped to the tank 74, for example, by means of a pump (not shown) arranged on the pipeline 82. As an alternative, the liquid heavy phase can be collected in the mud tank 70, for example via an internal passage in the separator 2, which will thus allow the separation of the liquid heavy phase from the slurry tank 70. Figure 4 Remove tank 74 from the system.

[0099] The inlet and the first liquid outlet are hermetically sealed and as described in relation to Figure 2 and Figure 3 As in the system discussed, the first liquid outlet does not have any dedicated device, such as a pump wheel, for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase. The separated liquid light phase is discharged to a fixed pipe 81 and collected in a tank 72.

[0100] If the interface position between the liquid light phase and the liquid heavy phase in the centrifuge bowl is to be adjusted, the system 1 may include a pressure regulating device (not shown) between the first liquid outlet and the tank 72. Such a pressure regulating device may be used only to apply back pressure for interface level control in the centrifuge bowl and may be different from a pressure regulating valve.

[0101] The centrifugal separator 1 is also arranged so that the liquid feed mixture enters the centrifugal bowl axially from the top at the rotation axis (X). In addition, the first and second liquid outlets are arranged at the top and are also arranged so that the first and second liquid phases are discharged at different radial distances from the rotation axis (X).

[0102] Figure 5 Also shown is a system 1 in which a liquid feed mixture supplied in a fixed conduit 80 via a liquid feed pump 73 is separated into a first liquid phase and a second liquid phase in a centrifugal separator 2. Thus, the centrifugal separator comprises a first liquid phase and a second liquid phase. Figure 2 The first liquid outlet discussed is for discharging the first liquid phase, and also a second liquid outlet for discharging a second liquid phase having a higher density than the first liquid.The slurry phase is discharged to a tank 70 as in the previous examples.

[0103] The inlet and the first and second liquid outlets are hermetically sealed. The first and second liquid outlets do not have any dedicated means for converting the kinetic energy of the separated liquid phase into a pressure flow. Moreover, the system 1 comprises a first pressure regulating device 85 downstream of the first liquid outlet and a second pressure regulating device 86 downstream of the second liquid outlet. These pressure regulating devices 85, 86 are only used to apply a back pressure for interface level control in the centrifugal bowl, i.e., to control the radial interface level between the first and second liquid phases during operation of the separator 2. The pressure regulating devices 85, 86 may be positive displacement pumps or regulating valves.

[0104] exist Figure 5 In the system, the centrifugal separator 2 is arranged so that the liquid feed mixture enters the centrifugal bowl axially from the bottom at the axis of rotation. The first liquid phase is discharged at the axis of rotation and the second liquid phase is discharged at a radial distance from the axis of rotation.

[0105] Figure 6 The above schematically shows Figure 2 The centrifugal separator 2 in the system in question. The centrifugal separator 2 is configured to separate the liquid feed mixture into a liquid light phase and a mud phase.

[0106] The centrifugal separator 2 comprises a centrifugal bowl 4. The bowl 4 is arranged to rotate about an axis of rotation X extending along an axial extension. Here, the axial extension serves to define the position of parts, components etc. of the centrifugal separator 2.

[0107] The bowl 4 is provided with a separation space 3. A stack 5 of frustoconical separation discs 7 is arranged in the separation space 3. The centrifugal separator 2 further comprises a main shaft 8, which is arranged at a first axial end 10 of the bowl 4 and is arranged to rotate the bowl 4 around the rotation axis X. The main shaft 8 forms part of a drive assembly 9 of the centrifugal separator 2. In the embodiment shown, the drive assembly 9 further comprises an electric motor 11. The bowl 4 is attached to the main shaft 8. The main shaft 8 forms part of the electric motor 11, i.e. the bowl 4 is directly driven by the electric motor 11. Therefore, the drive assembly 9 can rotate the bowl 4 around the rotation axis X. Alternatively, the drive assembly 9 can comprise a main shaft 8 connected to the bowl 4, an electric motor and a transmission arranged between the electric motor and the main shaft 8.

[0108] The centrifugal separator 2 further comprises a frame 12, which at least partially surrounds the bowl 4 and a fixed liquid passage means 14 arranged at a second axial end 16 of the bowl 4. The fixed liquid passage means 14 is releasably connected to the frame 12. Furthermore, the centrifugal separator 2 comprises a sealing assembly 18, which forms an interface between the rotatable bowl 4 and the fixed liquid passage means 14.

[0109] The first liquid path 20 extends concentrically with the rotation axis 6 between the fixed liquid path means 14 and the bowl 4. The second liquid path 22 extends radially outwardly of the first liquid path 20 between the fixed liquid path means 14 and the bowl 4.

[0110] The first liquid path 20 is arranged for guiding the liquid feed mixture into the centrifuge bowl 4 , thereby forming part of a fixed inlet pipe or inlet 90 of the centrifugal separator 2 .

[0111] Hence, the second liquid path 22 forms part of the "first liquid outlet" for discharging the separated liquid light phase out of the centrifuge bowl as discussed above. Hence, the first and second liquid paths 20, 22 are arranged in fluid communication with the separation space 3.

[0112] During separation of the liquid feed mixture in the separation space 3 of the bowl 4, the liquid feed mixture is guided from the center of the bowl 4 into the separation space 3 and the disk stack 5 via the first fluid path 20. The liquid feed mixture is separated into a liquid light phase and a slurry. The separated liquid light phase flows radially inwards between the separation disks 7 toward the rotation axis 6 and flows out of the bowl 4 via the second fluid path 22. The separated slurry phase flows radially outwards between the separation disks 7 toward the periphery of the separation space 3 and flows out of the bowl 4 via an intermittently openable slurry outlet (not shown).

[0113] Figure 7 Schematically shows the Figure 6A cross section of a fixed liquid passage device 14 of a centrifugal separator. The fixed liquid passage device 14 is releasably connected to the frame 12. In the embodiment shown, the fixed liquid passage device 14 is connected to the frame 12 using bolts 15. Alternatively, the connection may include clips, wing nuts, etc.

[0114] In the illustrated embodiment, the first liquid path 20 forms part of an inlet for the liquid feed mixture and the second liquid path 22 forms part of an outlet for the separated liquid light phase.

[0115] The sealing assembly 18 includes a first seal 24 disposed between the first liquid path 20 and the second liquid path 22. The first seal 24 extends concentrically with the rotation axis X and around the rotation axis X. The sealing assembly 18 also includes a second seal 26 disposed between the second liquid path 22 and a space radially outside the second liquid path 22. The second seal 26 extends concentrically with the rotation axis X and around the rotation axis X. The second seal 26 also extends around the first seal 24.

[0116] The first inner seal 24 comprises a first sealing member 28 arranged in the fixed liquid passage arrangement 14 and a first sealing surface 30 arranged in the bowl 4. The first sealing member 28 has a first axial end face 32 arranged in sealing abutment with the first sealing surface 30.

[0117] The second outer seal 26 comprises a second sealing member 34 arranged in the fixed liquid passage device 14 and a second sealing surface 36 arranged in the bowl 4. The second sealing member 34 has a second axial end face 38. The second axial end face 38 and the second sealing surface 36 are arranged in sealing abutment with each other.

[0118] The second sealing member 34 is separate from the first sealing member 28. In this way, two separate seals are provided, which means that each of them can be adjusted independently of the other seal and each of them can also be replaced individually.

[0119] Furthermore, the first and second sealing members 28, 34 can be separated from the first and second sealing surfaces 30, 36, together with the fixed liquid passage device 14 being released from the frame 12. In this way, the first and second sealing members 28, 34 can be easily accessed, for example for maintenance purposes, by disassembling the fixed liquid passage device 14 from the frame 12.

[0120] The first sealing member 28 is biased toward the first sealing surface 30 by one or more first resilient members 37. The second sealing member 34 is biased toward the second sealing surface 36 by one or more second resilient members 39. In the illustrated embodiment, the first and second resilient members 37, 39 comprise a plurality of helical springs. The resilient members may alternatively comprise stacked conical spring washers or resilient rubber material pads or other suitable members or combinations of members.

[0121] The first and second resilient members 37, 39 ensure that the first and second sealing members 28, 34 are biased independently of each other. Thus, the sealing abutment of the first axial end face 32 with the first sealing surface 30 and the sealing abutment of the second axial end face 38 with the second sealing surface 36 are ensured independently of each other.

[0122] The one or more first and second elastic members 37, 39 are arranged outside the first and second liquid paths 20, 22. That is, the first and second elastic members 37, 39 do not form any part of the first and second liquid paths 20, 22 but contribute to the biasing function thereof.

[0123] In the embodiment shown, the first and second sealing surfaces 30, 36 are arranged in one plane extending perpendicularly to the rotation axis 6. In this way, detachability of the first and second sealing members 28, 34 from the first and second sealing surfaces 30, 36 may be provided in a convenient manner.

[0124] However, according to alternative embodiments, the first and second sealing surfaces 30, 36 may each be arranged in different planes axially spaced apart from each other. Such planes may be arranged at an axial distance from each other in the range of 0-25 mm.

[0125] In this example, the first and second sealing surfaces 30, 36 are provided in a single sealing element 58, as shown in FIG. Figure 8 . In this way, the first and second sealing surfaces 30, 36 are conveniently provided in a single element mounted in the bowl 4. The single sealing element 58 forms at least part of the axial end of the bowl 4 at the second axial end 16 of the bowl 4. Thus, the first and second sealing surfaces 30, 36 are arranged at the axial end of the bowl 4 for the first and second axial end faces 32, 38 to abut therewith.

[0126] The single sealing element 58 is a replaceable single component and is therefore releasably fastened to the bowl 4. In the embodiment shown, the sealing element 58 is fastened to the bowl 4 by means of an annular element 59. The annular element 59 is threadedly connected to the body 61 of the bowl 4. The flange 63 of the sealing element 58 is fixed between the body 61 of the bowl 4 and the annular element 59. According to alternative embodiments, the sealing element 58 can be releasably fastened to the bowl 4 in a different manner, for example by means of bolts.

[0127] A single sealing element 58 forming at least part of the axial end of the bowl 4 at the second axial end 16 of the bowl 4 provides a compact sealing assembly 18. The sealing element 58 can be arranged close to the distributor 55 in the bowl 4. For example, the first and second sealing surfaces 30, 36 can be arranged in the range of 0-50 mm from the axial end of the distributor 55. The distributor 55 is arranged concentrically with the rotation axis 6 and supports the separation disc stack. Therefore, separation components, for example in the form of the separation disc 7 shown, are arranged on the distributor 55.

[0128] exist Figure 7 In the drawings, sealing O-rings arranged between the single sealing element 58 and other parts of the bowl 4 and between the respective first and second sealing members 28, 34 and other parts of the fixed liquid passage device 14 are omitted for clarity.

[0129] exist Figure 8 In the perspective view of FIG. 1 , the first and second sealing surfaces 30 , 36 are shown in phantom.

[0130] The first liquid path 20 extends through the sealing element 58 and the second liquid path 22 extends through the sealing element 58. In this way, the sealing element 58 providing the first and second sealing surfaces 30, 36 can be provided in a single element. More specifically, the first liquid path 20 extends through the central opening 65 of the sealing element 58 and the second liquid path 22 extends through a plurality of passages 67 arranged circumferentially around the central opening 65. The first sealing surface 30 is arranged between the central openings 65 and the second sealing surface 36 is arranged radially outside the passages 67.

[0131] The sealing element 58 comprises a flange 63 configured to be secured between the body 61 of the bowl 4 and the annular element 59, see also Figure 7 .

[0132] As an example, the first and second sealing components 28, 34 can be made of carbon-graphite. The sealing element 58 or at least the first and second sealing surfaces 30, 36 can be made of silicon carbide or tungsten carbide. In this way, good sealing and wear resistance can be provided by the first and second seals 24, 26. According to another example that may be suitable when at least one of the process fluids contains abrasives, at least the first and second axial end faces 32, 38 of the first and second sealing components 28, 34 and at least the first and second sealing surfaces 30, 36 of the sealing element 58 can be made of a hard material, such as silicon carbide or tungsten carbide.

[0133] Fig. 9The steps of a method 100 for separating a liquid feed mixture in a system 1 according to the present disclosure are schematically shown. The method 100 comprises: a) a step 101 of introducing the liquid feed mixture into a centrifugal separator using a liquid feed pump, and b) a step 102 of continuously discharging a first liquid phase from a first liquid outlet of the centrifugal separator. Moreover, for a system 1 designed for separating two liquid phases, the method 100 further comprises c) a step 103 of continuously discharging a second liquid phase from a second liquid outlet of the centrifugal separator. Moreover, in order to discharge a slurry phase from the centrifugal separator, the method 100 comprises e) a step 104 of intermittently discharging a slurry phase from the centrifugal separator.

[0134] The present invention is not limited to the disclosed embodiments, but may be varied and modified within the scope of the appended claims. The present invention is not limited to the orientation of the axis of rotation (X) disclosed in the figures. The term "centrifugal separator" also includes a centrifugal separator with a substantially horizontally oriented axis of rotation. In the above, the inventive concept is described mainly with reference to a limited number of examples. However, as will be readily appreciated by a person skilled in the art, other examples are equally possible within the scope of the inventive concept as defined by the appended claims, in addition to the examples disclosed above.

Claims

1. A system (1) for separating at least a first liquid phase from a liquid feed mixture, the system (1) comprising A centrifugal separator (2) comprising a centrifugal bowl (4) which is arranged to rotate about an axis of rotation (X) and in which separation of the liquid feed mixture takes place, an inlet (90) for receiving the liquid feed mixture, and a first liquid outlet (22) for discharging the first liquid phase, wherein The first liquid outlet (22) is hermetically sealed and does not have any dedicated means for converting the kinetic energy of the first liquid phase into a pressure flow of the first liquid phase, And wherein the system (1) also includes pressure generating means (73) for supplying the liquid feed mixture to the inlet (90) of the centrifugal separator (2), and Therein, the system (1) is configured such that the pressure generating device (73) is a main flow regulating device arranged to generate the outlet pressure required for delivering the first liquid phase from the first liquid outlet (22).

2. The system (1) according to claim 1, wherein: The centrifugal separator (2) has no further liquid outlet for discharging the further separated liquid phase.

3. The system (1) according to claim 2, wherein: The system (1) further comprises a tank (72) downstream of the first liquid outlet (22), and wherein the system (1) does not have any pressure regulating valve between the first liquid outlet (22) and the tank (72), wherein the pressure regulating valve is arranged to generate a back pressure on the first liquid outlet (22).

4. The system (1) according to any one of claims 2 or 3, wherein: The centrifugal separator (2) is arranged so that the liquid feed mixture enters the centrifugal bowl (4) axially from the top.

5. The system (1) according to claim 4, wherein: The liquid feed mixture enters the centrifugal separator (1) at the rotation axis (X), and wherein the first liquid outlet (22) is arranged such that the first liquid phase is discharged at a radial distance from the rotation axis (X).

6. The system (1) according to any one of claims 2 to 5, wherein: The inlet (90) is also hermetically sealed.

7. The system (1) according to claim 6, wherein: The inlet (90) and the first liquid outlet (22) are hermetically sealed by at least one mechanical seal (18), and wherein the sealing interfaces of the at least one mechanical seal (18) are arranged in the same radial plane.

8. The system (1) according to any one of claims 2 or 3, wherein: The centrifugal separator (2) is arranged such that the liquid feed mixture enters the centrifugal bowl axially from the bottom.

9. The system (1) according to claim 1, wherein: The centrifugal separator (2) comprises a second liquid outlet (91) for discharging a second liquid phase having a higher density than the first liquid.

10. The system (1) according to claim 9, wherein: The second liquid outlet (91) is also hermetically sealed and does not have any dedicated means for converting the kinetic energy of the second liquid phase into a pressure flow of the second liquid phase.

11. The system (1) according to claim 10, wherein: The system (1) comprises a first pressure regulating device (85) downstream of the first liquid outlet (22) and a second pressure regulating device (86) downstream of the second liquid outlet (91); wherein the first pressure regulating device (85) and the second pressure regulating device (86) are arranged to regulate the interface between the liquid phases in the centrifugal bowl and are devices other than pressure regulating valves.

12. The system (1) according to claim 9, wherein: The second liquid outlet (91) is an open outlet formed by an annular gravity disk.

13. The system (1) according to any one of claims 9 to 12, wherein: The centrifugal separator (2) is arranged so that the liquid feed mixture enters the centrifugal bowl (4) axially from the top.

14. The system (1) according to claim 13, wherein: The liquid feed mixture enters the centrifugal separator (2) at the rotation axis (X), and wherein the first liquid outlet (22) and the second liquid outlet (91) are arranged so that the first liquid phase and the second liquid phase are discharged at different radial distances from the rotation axis (X).

15. The system (1) according to claim 14, wherein: The inlet (90) is also hermetically sealed.

16. The system (1) according to claim 15, wherein: The inlet (90) and the first (22) and second (91) liquid outlets are sealed by at least one mechanical seal (18), and wherein the sealing surfaces of the at least one mechanical seal (18) are arranged in the same radial plane.

17. The system (1) according to any one of claims 9 to 16, wherein: The centrifugal separator (2) is arranged such that the liquid feed mixture enters the centrifugal bowl (4) axially from the bottom.

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