Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04B—CENTRIFUGES
  • B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
  • B04B1/04—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with inserted separating walls
  • B04B1/08—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with inserted separating walls of conical shape
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04B—CENTRIFUGES
  • B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
  • B04B1/10—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with discharging outlets in the plane of the maximum diameter of the bowl
  • B04B1/14—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with discharging outlets in the plane of the maximum diameter of the bowl with periodical discharge
  • B04B1/16—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with discharging outlets in the plane of the maximum diameter of the bowl with periodical discharge with discharging outlets controlled by the rotational speed of the bowl
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04B—CENTRIFUGES
  • B04B11/00—Feeding, charging, or discharging bowls
  • B04B11/04—Periodical feeding or discharging; Control arrangements therefor

Definitions

• the present invention relates to the field of high-speed centrifugal separators, and more specifically to a method for operating a high-speed centrifugal separator.
• High speed centrifugal separators are generally used for separation of liquids and/or for separation of solids from a liquid.
• liquid mixture to be separated is introduced into a rotating centrifuge bowl and heavy particles or denser liquid, usually 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.
• Separation members such as a stack of frustoconical separation discs, are usually used within the rotating bowl in order to enhance the separation performance.
• An example of a high-speed centrifugal separator is described in patent application EP 3315205 .
• a solid phase is separated from the liquid feed mixture.
• Such solid phase may be intermittently discharged during the separation process. This is a process that occurs for a fraction of a second, during which the centrifuge bowl is partially or fully emptied from a sludge phase containing the solid phase.
• liquid such as water
• Such discharged liquid may contain portion of a valuable liquid phase, which is why is it desired to discharge as "dry" sludge as possible.
• a main object of the present invention is to provide a method and system for operating a centrifugal separator that may provide for a decreased loss of liquids in a discharged solid phase.
• the centrifugal separator comprises a centrifuge bowl arranged to rotate around an axis of rotation (X) and comprising a separation space, in which surface enlarging inserts are arranged, and a sludge space arranged radially outside the separation space; a drive member for rotating the centrifuge bowl around the axis of rotation (X).
• the centrifuge bowl further comprises an inlet for supply of the liquid feed mixture, at least one liquid outlet for discharge of a separated liquid phase, a sludge outlet arranged for intermittently discharging a separated solid phase from said centrifuge bowl.
• the centrifugal separator may be a disc-stack centrifugal separator, e.g. as disclosed in US20210107014 .
• Step a) of rotating the centrifuge bowl is performed using a drive unit of the centrifugal separator.
• This may for example be an electrical motor.
• the centrifuge bowl may be rotated at a speed that is above 2000 rpm, such as above 4000 rpm.
• Step c) of separating the liquid feed mixture may comprise separating the liquid feed mixture into two liquid phases of different density, as well as a solid phase.
• Step d) of discharging a solid phase may include discharging the separated solid phase as sludge from the outer periphery of the centrifuge bowl to a space between the centrifuge bowl and a surrounding, stationary hood.
• the sludge outlet arranged for intermittently discharging a separated solid phase may comprise a plurality of openable ports arranged in the centrifuge bowl wall.
• Step e) of measuring the decrease in rotational speed may be performed by a speed sensor.
• a speed sensor may be arranged to measure the rotational speed of the centrifuge bowl and/or a spindle or shaft to which the bowl is attached.
• Step e) may comprise continuously measuring the rotational speed of the centrifuge bowl, also during step c), and thereby measuring the decrease in rotational speed after discharge. "Immediately after discharge” thus comprise measuring the decrease in rotational speed that is due to the solid discharge of step d).
• Step f) of controlling the centrifugal separator may comprise one or several different control measures of the centrifugal separator, such as determining and/or controlling parameters of the operation of the centrifugal separator.
• the control measures may for example relate to the intermittent discharge system used is step d), a feed pump used in step b) or the drive member used for step a).
• the first aspect of the invention in based on the insight that the decrease in rotational speed experienced after a discharge of solid phase may be related to the separation process and the contents of the discharged phase, and that such information may be used for controlling and thereby optimising the separation process.
• the characteristics of the speed drop may be correlated to the physical properties of the discharged phase, and that this may be used e.g. improve the separation process.
• step e) comprises measuring the Absolute rotational speed decrease and/or the Rate of rotational speed decrease that is due to the discharge of solid phase in step d).
• the "Absolute rotational speed decrease” thus refers to difference in rotational speed before discharge to the minimum speed experienced after discharge. Typically, the rotational speed will quickly decrease to minimum value and then more slowly recover to the rotational speed before the discharge. The minimum speed may occur within a couple of seconds, such as within five seconds, after discharge.
• the "Rate of rotational speed decrease” refers to the initial rate of speed decrease, i.e. relates to the initial derivative of the speed vs time function.
• the initial derivative may have a more or less constant value before the speed has dropped to the Absolute rotational speed decrease.
• step e) may comprise measuring the Absolute rotational speed decrease and measuring the Rate of rotational speed decrease.
• step e) may comprise measuring one of the Absolute rotational speed decrease and the Rate of rotational speed decrease.
• a first discharge having a large Absolute rotational speed decrease and a large rate of Rate of rotational speed decrease may contain less liquid, i.e. be more "dry", as compared to a second discharge in having a lower Absolute rotational speed decrease and a lower rate of Rate of rotational speed decrease.
• the Rate of rotational speed decrease may be measured in an initial period after discharge, wherein said initial period is less than 1.0 s, such as less than 0.5 s.
• the information received from measuring the Absolute rotational speed decrease and the Rate of rotational speed decrease may be used for controlling the separator to increase the yield. Consequently, the step f) may comprise controlling the centrifugal separator so as to regulate the dryness of a subsequent discharge of a solid phase based on the measurements in step e).
• the dryness of a discharge relates to the amount of liquid present in the discharge.
• a dry discharge has thus less amount of liquid compared to a wet discharge. Regulating the dryness is thus regulating the liquid amount of the discharge.
• Regulating the dryness may be increasing the dryness of the discharged sludge, i.e. decreasing the amount of liquid that is discharged together with the solid phase. This may reduce losses of liquid - which may be or contain a valuable process product of the separation process- during intermittent discharge of the solid phase.
• the dryness may be regulated by adjusting the time to a subsequent discharge of a solid phase.
• the dryness may be regulated by adjusting the rotational speed of the centrifuge bowl.
• the dryness may be regulated by adjusting the flow rate of liquid feed mixture that is supplied to the centrifugal separator. One or several of these actions may be performed to regulate the dryness of the discharge of a subsequent solid phase.
• the speed of the rotor may be increased to increase the separation performance.
• the flow rate of liquid feed mixture may be decreased to increase the separation performance.
• step f) of controlling comprises controlling the system used for intermittently discharging a separated solid phase from the centrifuge bowl.
• the system used for intermittently discharging the separated solid phase may comprise a sliding bowl bottom within the centrifugal separator that opens and closes a set of ports in the bowl wall, as known in the art.
• Controlling the intermittent discharge system in step f) may comprise controlling the amount or pressure of operating fluid, such as water, used for activating the opening or closing movements of the sliding bowl bottom.
• step f) of controlling may comprise controlling the time during which the sludge outlet is open. This may be achieved by controlling e.g. the volume or pressure of the operating fluid that is supplied to the centrifuge bowl.
• the measurements of the decrease in rotational speed as a function of time immediately after a solid discharge may be used as a feedback to the intermittent discharge system.
• step d) may comprise discharging a solid phase of volume V1 from the centrifuge bowl
• step f) of controlling the centrifugal separator may comprise controlling the intermittent discharge system to discharge a solid phase of volume V2, wherein V2 is larger or smaller than V1, during a subsequent discharge of solid phase.
• Step f) may as a complement or alternative comprise adjusting the time before a subsequent discharge to increase or decrease the volume of the solid phase that is discharged.
• step f) may comprise controlling the intermittent discharge system to check the operation status of the intermittent discharge system.
• the measurements of the decrease in rotational speed as a function of time immediately after a solid discharge may be used to check if the intermittent discharge system seems to function in a normal way, and if not, an alarm signal may be triggered to the operator.
• step f) of controlling comprises controlling a device arranged in connection to the inlet or a liquid outlet for estimating the amount of solid phase within the centrifuge bowl.
• the centrifugal separator may comprise a device for estimating the amount of solids present within the centrifuge bowl. Such estimation may be performed continuously.
• the device may for example be a turbidity meter that is used for estimating the amount of solids present in the liquid feed mixture supplied to the separator, and such turbidity measurements may be used for determining the volume of solids within the bowl (see for example WO 2022268516 ).
• the method of the present invention thus provides for feedback to such a device and may aid in calibrating such a device.
• measuring the decrease in rotational speed in step e) is measured at a sampling rate that is higher than 2 times per second.
• Such a high sampling rate may increase the resolution and the data quality of the speed measurements, especially if determining the Rate of rotational speed decrease.
• the decrease in rotational speed in step e) may be measured at a sampling rate so that a measurement point is acquired for every revolution of the centrifuge bowl.
• Such high sampling rate may facilitate the determination of e.g. the Rate of rotational speed decrease, which may be measured during the first 0.5 seconds after discharge.
• centrifugal separator for separating at least one liquid phase and a solid phase from a liquid feed mixture
• This aspect may generally present the same or corresponding advantages as the former aspect. Effects and features of this second aspect are largely analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect.
• the centrifugal separator of the second aspect may thus be used for performing the method of the first aspect as discussed above.
• the centrifugal separator is for separation of a liquid feed mixture.
• the liquid feed mixture may be an aqueous liquid or an oily liquid.
• the centrifugal separator may be for separating solids and one or two liquids from the liquid feed mixture.
• the centrifuge bowl encloses by it walls a separation space and a sludge space.
• the separation space in which the separation of the fluid mixture takes place, comprises surface enlarging inserts, i.e. separation members that may be in the form of a stack of separation discs.
• the separation discs may e.g. be of metal.
• the separation discs may be frustoconical separation discs, i.e. having separation surfaces forming frustoconical portions of the separation discs.
• the separation discs may be arranged coaxially around the axis of rotation at a distance from each other such that to form passages between each two adjacent separation discs.
• the centrifuge bowl of the separator may be arranged to be rotated around vertical axis of rotation, i.e. the axis of rotation may extend vertically.
• the centrifuge bowl is usually supported by a spindle, i.e. a rotating shaft, and may thus be mounted to rotate with the spindle. Consequently, the centrifugal separator may comprise a spindle that is rotatable around the axis of rotation (X).
• the centrifugal separator may be arranged such that the centrifuge bowl is supported by the spindle at one of its ends, such at the bottom end or the top end of the spindle.
• the centrifugal separator may further comprise a stationary frame in which the centrifuge bowl is mounted.
• the frame may comprise an upper hood section that covers the centrifuge bowl.
• the drive member is arranged to rotate the centrifuge bowl around the axis of rotation.
• the drive member may comprise an electrical motor arranged to drive e.g. a spindle directly or may for example be provided beside the spindle and rotate the rotating parts of the centrifugal separator by a suitable transmission, such as a belt or a gear transmission.
• the centrifugal separator also comprises an inlet for supply liquid mixture to be separated (the liquid feed mixture).
• This inlet may be arranged for receiving the liquid feed mixture and be arranged centrally in the centrifuge bowl, thus at the rotational axis.
• the centrifuge bowl may be arranged to be fed from the bottom, such as through a rotating spindle onto which the centrifuge bowl is mounted. However, the centrifuge bowl may also be arranged to be fed from the top, such as through a stationary inlet pipe extending into the bowl to the inlet.
• the at least one liquid outlet for a separated liquid phase may be in the form of one or two liquid outlets. Such liquid outlets for separated liquid phase or phases may be arranged at the top or the bottom of the centrifugal separator.
• the centrifugal separator is also arranged for discharging a solid phase - that may also contain some liquid - to the surrounding space around the centrifuge bowl.
• This is performed by the sludge outlet, which may be in the form of a set of ports arranged to be opened intermittently during operation.
• the sludge outlets may thus be a number of ports arranged at or near the periphery of the centrifuge bowl.
• the centrifugal separator may further comprise an intermittent discharge system arranged for intermittently opening and closing the sludge outlet during operation, as known in the art.
• the centrifugal separator may be arranged for emptying a partial content of the bowl during such an intermittent discharge (partial discharge) or arranged for emptying the whole content of the centrifuge bowl during intermittent discharge (full discharge).
• the intermittent discharge system may comprise an operating slide in, e.g. in the form of a sliding bowl bottom, which is axially movable between a closed position, in which the sludge outlets are closed, and an open position, in which the sludge outlets are open. Keeping the operating slide in a closed position may be effected by supplying fluid to the centrifuge bowl, e.g. to a channel to a closing chamber in order to hold the operating slide in the closed position. Opening the ports may be affected by supplying opening water e.g. to an opening chamber or to a valve member within the bowl.
• the sensor is arranged to measure the decrease in rotational speed as a function of time immediately after intermittent discharge of a separated solid phase.
• the sensor may thus be a speed sensor.
• the sensor may be arranged to measure the speed of the bowl itself or the speed of a spindle that supports the bowl.
• the drive member may thus be connected to such spindle.
• the sensor may be configured for measuring the speed of the centrifuge bowl continuously, even between discharge of the solid phase.
• the sensor may be configured to measure the rotational speed in an initial period after discharge, wherein the initial period is less than 1.0 s, such as less than 0.5 s.
• the sensor may be configured for measuring the decrease in rotational speed at a sampling rate that is higher than 2 times per second.
• the may be configured for measuring the rotational speed of the centrifuge bowl at a sampling rate so that a measurement point is acquired for every revolution of the centrifuge bowl.
• the sensor of the present disclosure is operable to generate a sensor output indicative of the rotational speed of the centrifuge bowl.
• the control unit is configured to communicate with the sensor, and with help of such input from the sensor control the centrifugal separator.
• the determination of the decrease in rotational speed as a function of time immediately after intermittent discharge may be performed by the sensor or control unit.
• the control unit may be arranged in a stationary part of the centrifugal separator.
• the control unit may comprise any suitable type of programmable logical circuit, processor circuit, or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions.
• the control unit may comprise a processor and an input/output interface for communicating with the sensor that measures the rotational speed.
• the control unit may be the overall centrifugal separator control unit, which may e.g. regulate the rotational speed and/or the flow rate of liquid mixture that is separated.
• control unit is configured to determine the Absolute rotational speed decrease and/or the Rate of rotational speed decrease that is due to the discharge of solid phase based on the measurements from the sensor, and to control the centrifugal separator based on such determination.
• the Absolute rotational speed decrease and the Rate of rotational speed decrease is as defined in relation to the first aspect above.
• control unit is configured to control the centrifugal separator by regulating the dryness of a subsequent discharge of a solid phase based on the measurements from the sensor.
• the dryness may be regulated by adjusting the time to a subsequent discharge of a solid phase, adjusting the rotational speed of the centrifuge bowl, and/or adjusting the flow rate of liquid feed mixture that is supplied to the centrifugal separator.
• the control unit may hence be configured for controlling the drive unit to rotate the centrifuge bowl at a certain operational speed.
• the control unit may further be configured for controlling an inlet feed pump or a system that determines the time to a subsequent discharge of solid phase.
• control unit is configured to control a system used for intermittently discharging a separated solid phase from said centrifuge bowl.
• control unit may further be configured to control an intermittent discharge system of the centrifugal separator, i.e. to control when to perform an intermittent discharge of a solid phase.
• the control unit may be configured for controlling the amount or volume of operating fluid used, and or the pressure of the operating fluid used by such an intermittent discharge system for opening and closing the sludge outlet.
• the control unit may thus be configured to control the system used for intermittently discharging a separated solid phase from the centrifuge bowl based on the measurements from the sensor.
• the control unit may as a complement or alternative be configured to control the system used for intermittently discharging a separated solid phase from the centrifuge bowl based on e.g. a set timer interval or by a set pressure of the operating fluid used by the intermittent discharge system.
• the centrifugal separator may thus comprise an intermittent discharge system as discussed in relation to the first aspect above.
• the control unit may further be configured to generate an alert signal if it is determined from the measurements from the sensor that there is a malfunction in the intermittent discharge system.
• control unit is configured to control a device arranged in connection to the inlet or a liquid outlet for estimating the amount of solid phase within the centrifuge bowl.
• such device may be a turbidity meter.
• turbidity meter may be arranged in connection to the inlet or a liquid outlet of the centrifugal separator and may be used by the control system to estimate the volume or amount of solid phase present within the centrifuge bowl.
• Fig. 1 show a cross-section of an embodiment of a centrifugal separator 1 which in this embodiment is arranged to separate a solid phase, a liquid heavy phase and a liquid light phase from a liquid feed mixture.
• the centrifugal separator 1 comprises a centrifuge bowl 10 which is arranged to rotate around an axis of rotation (X) together with spindle 7 onto which the bowl 10 is mounted.
• the spindle 7 is supported a bottom bearing 5 and a top bearing 6.
• the centrifuge bowl 10 is attached to the upper portion of the spindle 7 and forms within itself a separation space 9a in which centrifugal separation of the liquid feed mixture takes place during operation.
• the separation space 9a within the centrifuge bowl 10 is provided with a stack of frustoconical separation discs 17 in order to achieve effective separation of the liquid feed mixture, such as separation discs disclosed in EP3315203 .
• the separator 1 comprises a stationary hood 2 that surrounds at least the upper portion of the centrifuge bowl 10.
• the hood 2 thus defines at least part of a surrounding space 3 in which the centrifuge bowl 10 is arranged.
• the spindle 7 is in this example a hollow spindle that is used for introducing the liquid feed mixture to the inlet 11 of the centrifuge bowl 10.
• the inlet 11 and the hollow spindle is sealed by an inlet seal 19 to a stationary inlet pipe 40.
• the centrifuge bowl 10 further comprises a liquid outlet 12 for discharging a separated liquid light phase and a liquid outlet 13 for discharging a liquid heavy phase.
• the liquid light phase outlet 12 is arranged at a smaller radius than the liquid heavy phase outlet 13.
• the liquid outlets 12, 13 are sealed using an outlet seal 15.
• the inlet 19 and/or outlet 15 seal could be a mechanical seal.
• the centrifuge bowl 10 further comprises a solid phase outlet 14 for discharging a separated solid phase from the sludge space 9b - which is located radially outside the separation space 9a - to the surrounding space 3.
• the solid phase outlet 14 takes the form of a plurality of intermittently openable sludge outlets arranged at the outer periphery of the centrifuge bowl 10.
• the solid phase outlets 14 form part of the intermittent discharge system.
• the opening of the sludge outlets 14 of the intermittent discharge system is controlled by means of an operating slide 31 arranged within the bowl 10 and actuated by supply of operating water supplied via line 30 to the centrifuge bowl 10.
• the operating water is supplied via an operating water module (OWM) 40.
• OOM operating water module
• the operating slide 31 is movable between a closed position in which the sludge outlets 14 are closed, and an open position, in which sludge outlets 14 are open.
• operating water in the form of closing water supplied by the OWM 40 may act on the operating slide 31 to close the outlets 14.
• the draining of the water and thereby opening of the sludge outlets 14 may also be initiated by introducing operating water, such as opening water, from the OWM 40.
• Discharged solid phase is collected under the hood 2 and further directed to vessel 20.
• the vessel 20 is in the form of a cyclone and thus arranged for collecting the separated solid phase discharged from the centrifuge bowl 10.
• the vessel 20 is further connected to a discharge device 25 in the form of a sludge pump for discharge of sludge and liquid present in the vessel 20.
• the centrifugal separator 1 further comprises a drive motor 4 configured to rotate the centrifuge bowl 10 in relation around the axis of rotation (X).
• the drive motor 4 may be connected directly to the spindle 7 or connected to the spindle 7 via a transmission means.
• the centrifuge bowl 10 is caused to rotate by torque transmitted from the drive motor 4 to the spindle 7.
• liquid mixture to be separated is supplied to the hollow spindle 7 and inlet 11 using the inlet feed pump 41.
• the liquid mixture to be separated is brought into the separation space 9a within the centrifuge bowl 10 and further between the separation discs of the stack that is fitted in the separation space 9a.
• a separated liquid light phase moves radially inwards between the separation discs and is discharged via the liquid light phase outlet 12 to the stationary outlet pipe 12a, whereas separated liquid heavy phase is discharged via the liquid heavy phase outlet 13 to the stationary outlet pipe 13a.
• Heavier components in the liquid mixture e.g.
• the separated solid phase is emptied intermittently from the solid phase outlets 14 by actuating the operating slide 41 to move axially downwards for fractions of a second using operating water supplied via the OWM 40.
• the amount and/or pressure of such operating water may decide the time during which the sludge outlets 14 are open, and thereby the volume or amount of sludge that is discharged via the sludge outlets 14.
• liquid from the liquid feed mixture is discharged together with the solid phase, which means that the solid phase is discharged as sludge with a varying content of liquid.
• the centrifugal separator 1 further comprises a speed sensor 51 arranged for measuring the rotational speed of the rotating spindle 7 and also the decrease in rotational speed as a function of time immediately after intermittent discharge of a separated solid phase.
• the sensor 51 is arranged to measure the rotational speed of the spindle 7, but it may as well be arranged for measuring the rotational speed of the centrifuge bowl 10.
• the centrifugal separator 1 further comprises a control unit 50.
• This control unit 50 may be the unit that controls operation, such as rotational speed, of the centrifugal separator 1.
• the control unit 50 may thus control drive unit 4, as indicated by arrow C2.
• the control unit 50 is in this example also configured to control the OWM 40, such as controlling when to initiate a sludge discharge as well as the amount and/or pressure of the operating liquid used for opening the sludge outlets 14, as indicated by arrow "C1" in Fig. 1 .
• the control unit 50 is configured to control the inlet feed pump 41, as indicated by arrow "C3".
• the centrifugal separator 1 further comprises an inlet turbidity meter 52, that is used for estimating the amount of solids within the liquid feed mixture and hence the amount of solids that may be present within the centrifuge bowl 10.
• the control unit 50 is in this case also configured for communicating with the inlet turbidity meter 52.
• control unit 50 further communicates with the speed sensor 51, as indicated by arow "A" and is further configured to control the centrifugal separator 1 based on the measurements from the sensor 51.
• control unit may be configured to control one or several of the intermittent discharge system via the OWM 40, the drive motor 4, the turbidity meter 52 and the inlet feed pump 41.
• the control unit 50 is in this case configured to determine the Absolute rotational speed decrease and the Rate of rotational speed decrease that is due to the discharge of solid phase based on the measurements from the sensor 51, and thus to control the centrifugal separator 1 based on such determination.
• control unit 50 may comprise a device having processing capability in the form of processing unit, such as a central processing unit, which is configured to execute computer code instructions which for instance may be stored on a memory.
• the memory may thus form a computer-readable storage medium for storing such computer code instructions.
• the processing unit may alternatively be in the form of a hardware component, such as an application specific integrated circuit, a field-programmable gate array or the like.
• the control unit 50 may comprise communication interface, such as a transmitter/receiver interface, via which it may receive data from the speed sensor 51.
• the control unit 50 may thus be configured for receiving information of the rotational speed of the centrifuge motor as well as the rotational speed decrease after a discharge of a separated solid phase.
• the communication interface may be used for sending operational requests to any of the OWM 40, the drive motor 4, the turbidity meter 52 and the inlet feed pump 41. The operational requests are based on the received data from the speed sensor 51 and the analysis of such data. The analysis will be described further in relation to Figs 2-4 below.
• control unit 50 may be configured to send operational requests to the intermittent discharge system of the centrifugal separator (used for intermittently discharging a separated solid phase) based on the measured rotational speed decrease, or signal that the intermittent discharge system functions ok or that it is a malfunction in such an intermittent discharge system.
• control unit 50 may be configured to send operational requests to a unit of the centrifugal separator 1 to regulate the dryness of a subsequent discharge of a solid phase based on the measurements from the sensor 51.
• the dryness may be regulated by sending requests to the OWM 40 to adjust the time to a subsequent discharge of a solid phase or to adjust the amount and/or pressure of the operational liquid used to initiate the subsequent discharge.
• control unit 50 may be configured to send operational request to the drive motor 4 to adjust the rotational speed of the centrifuge bowl 10.
• control unit 50 may be configured to send operational request to inlet feed pump 41 for adjusting the flow rate of liquid feed mixture that is supplied to the centrifugal separator.
• control unit 50 may be configured to send operational requests to the turbidity meter 52 to aid in calibrating the functions of such a turbidity meter 52.
• Figs. 2-4 show in more detail an embodiment on how the measurements of the decrease in rotational speed may be measured and evaluated in the method of the present disclosure. More specifically, the steps discussed below in relation to Figs. 2-4 may be performed as part of steps e) or f) in the method of the present disclosure.
• Fig. 2 shows the measured rotational speed as a function of time as measured by a speed sensor 51 during a discharge of a solid phase from the centrifugal separator 1.
• the rotational speed is measured at a sampling rate so that a measurement point is acquired for every revolution of the centrifuge bowl 10.
• the rotational speed drops quickly from an operational speed v3 down to a minimal rotational speed v1 before slowly returning to the previously held operational speed.
• the Absolute rotational speed decrease Va is measured as v3-v1.
• this Absolute rotational speed decrease Va may be in the range of a hundred to a few hundred rpm.
• the time between t1 and t2 may be less than 0.5 seconds, and the time between t1 and t4 may be about 20-30 seconds.
• Fig. 3 shows a close-up view of the graph in Fig. 2 to provide for a more detailed analysis of the Rate of rotational speed decrease R that occurs immediately after discharge of the solid phase.
• the graph in Fig. 3 is the same as the graph in Fig. 2 but seen during a shorter period of time.
• Time points t1 and t2 in Fig. 3 corresponds to time points t1 and t2 in Fig, 2 , etc.
• the Rate of rotational speed decrease R is measured as the linear decrease in rotational speed that occurs during the initial period after discharge, which may be less than 1.0 s, such as less than 0.5 s after discharge.
• the speed sensor 51 may be operable to send the measured rotational speed to the control unit 50, and the control unit 50 may be configured to determine at least one, or both, of the Rate of rotational speed decrease R and the Absolute rotational speed decrease Va.
• the inventors have found that both the Rate of rotational speed decrease R and the Absolute rotational speed decrease Va correlate to physical characteristics of the discharged solid phase. These parameters R and Va may thus be used alone or in combination to give information about the discharged solid phase, and thus provide for controlling the centrifugal separator.
• the Rate of rotational speed decrease R is plotted against the Absolute rotational speed decrease Va for a number of hypothetical individual discharges (plotted as "x") in Fig. 4 . It has been found that the Rate of rotational speed decrease R for example correlate well with the Absolute rotational speed decrease Va and that these parameters follow an overall linear relationship (as illustrated by the arrow in Fig. 4 ). This allows for finding clusters of solid discharges having more or less the same characteristics. In the graph of Fig. 4 , the data points "x" have been grouped into four clusters, as represented by group G1, G2, G3 and G4.
• the grouping was based on both parameters, i.e. on both the Rate of rotational speed decrease R and the Absolute rotational speed decrease Va. In other examples, only one of these parameters may be used to group individual discharges. This may give an easier data evaluation but may led to less precise grouping.
• the centrifugal separator may be controlled in different ways. As an example, it may be determined, e.g. by the control unit 50, that a discharge is wet (e.g. corresponding to a discharge in Group 1 or 2 in Fig 4 ), and that the time before a subsequent discharge should be increased in order to allow for the accumulation of more solids within the centrifuge bowl before making the next solid discharge.
• a discharge is wet (e.g. corresponding to a discharge in Group 1 or 2 in Fig 4 )
• the time before a subsequent discharge should be increased in order to allow for the accumulation of more solids within the centrifuge bowl before making the next solid discharge.
• control unit 50 may be configured to receive measurements of the decrease in rotational speed as a function of time immediately after a discharge of a solid phase, determine the Rate of rotational speed decrease R and the Absolute rotational speed decrease Va, comparing the determined R and Va to prestored values, and control the centrifugal separator based on such comparison.
• the comparison may comprise categorizing an individual discharge as belonging to one prestored group out of a number of prestored groups of discharges.
• the groups of discharges may comprise "dry discharge (Group G4)", “medium dry discharge Group G3)", “medium wet discharge (Group G2)” and "wet discharge (Group G1)".
• the different prestored group of discharges may be connected to one or several control measures to be performed, such as one or several of the above-discussed ways of controlling the centrifugal separator 1, i.e. controlling the intermittent discharge system, controlling the dryness of a subsequent discharge, controlling the drive motor 3, controlling the turbidity meter 52 and/or controlling the liquid feed pump.
• control measures such as one or several of the above-discussed ways of controlling the centrifugal separator 1, i.e. controlling the intermittent discharge system, controlling the dryness of a subsequent discharge, controlling the drive motor 3, controlling the turbidity meter 52 and/or controlling the liquid feed pump.
• the method 100 for operating a centrifugal separator for separating at least one liquid phase and a solid phase from a liquid feed mixture is illustrated in Fig. 5 .
• the method 100 comprises a step a) of rotating 101 the centrifuge bowl 10 at a rotational speed. This speed may be the operational speed of the centrifugal separator, such as speed of above 2000 rpm, such as above 4000 rpm.
• the method 100 further comprises a step b) of supplying 102 the liquid feed mixture to the centrifuge bowl 10 and a step c) of separating 103 the liquid feed mixture in the centrifuge bowl 10 into at least one liquid phase and a solid phase.
• the method 100 comprises a step d) of discharging 105 the solid phase from the centrifuge bowl 10. This may be an intermittent discharge of a solid phase.
• the method 100 further comprises step e) of measuring 106 the decrease in rotational speed as a function of time immediately after step d). This step may comprise measuring the Absolute rotational speed decrease and the Rate of rotational speed decrease that is due to the discharge of solid phase in step d).
• the rate rotational speed decrease may be measured in an initial period after discharge. Such initial period may be less than 1.0 s, such as less than 0.5 s.
• the step e) of measuring 106 the decrease in rotational speed in step e) is measured at a sampling rate that is higher than 2 times per second, such as measured at a sampling rate so that a measurement point is acquired for every revolution of the centrifuge bowl.
• the method 100 further comprises the step f) of controlling 107 the centrifugal separator (1) based on the measurements in step e).
• Step f) may comprise controlling the centrifugal separator 1 so as to regulate the dryness of a subsequent discharge of a solid phase based on the measurements in step e).
• the dryness may be regulated by adjusting the time to a subsequent discharge of a solid phase, adjusting the rotational speed of the centrifuge bowl, and/or adjusting the flow rate of liquid feed mixture that is supplied to the centrifugal separator.
• step f) of controlling may comprise controlling the system used for intermittently discharging a separated solid phase from said centrifuge bowl 10 and/ or controlling a device 52 arranged in connection to the inlet 11 or a liquid outlet 12,13 for estimating the amount of solid phase within the centrifuge bowl 10.
• centrifugal separator also comprises centrifugal separators with a substantially horizontally oriented axis of rotation.

Landscapes

• Centrifugal Separators (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=90735249

Family Applications (1)

Country Status (2)

Citations (8)

• 2024
  • 2024-04-16 EP EP24170494.9A patent/EP4635630A1/de active Pending
• 2025
  • 2025-03-26 WO PCT/EP2025/058293 patent/WO2025219038A1/en active Pending

Patent Citations (8)

Also Published As

Similar Documents

Legal Events