EP3485979B1 - Method for detecting the operating state of a centrifuge - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

A generic procedure is in each case from the EP 0 724 912 A2 and the WO 2015/136162 A1 known. This is how it is done in the EP 0 724 912 A1 proposed to record vibration frequencies and intensities of a centrifuge with a measuring sensor as electrical signals and then to subject these signals to a frequency spectrum analysis, whereupon an evaluation is carried out.

In the WO2016/008755 A1 It is proposed to take noise development into account when regulating the operation of a centrifuge. In the DE 40 04 584 A1 In the case of a non-generic filter centrifuge, it is suggested to monitor the withdrawal of the liquid and, if necessary, to interrupt it depending on changes in this process. The technological background also includes: JP 2002 343763 A called.

A suspension to be processed with a centrifuge drum and separated into one or more phases is exposed to a high centripetal acceleration, which in a separator with a vertical axis of rotation can be more than 10,000 times the acceleration due to gravity (more than 10,000 g).

Due to the high forces that occur in these typical operating conditions and the resulting loads on the rotating system, it is desirable to record the current operating state as well as possible when operating the centrifuge in order to be able to monitor, control and, if necessary, optimize it with this information. In addition, it should preferably be possible to reliably identify dangerous conditions as early as possible and to prevent them through appropriate actions.

The solution to this problem is the object of the invention.

The invention solves this problem by the method of claim 1.

100

Erfassen eines zeitlichen Verlaufs eines Körperschallsignals mit wenigstens einem an einem Bauteil der Trommel oder in der Nähe eines Bauteils der Trommel angeordneten Körperschallsensor, insbesondere mit einer vorgegebenen Tastrate;

200

Transformation des jeweils aufgenommenen Körperschallsignales in ein Schwingungs- bzw. Frequenzspektrum;

300

Vergleich des aktuell ermittelten Spektrums mit wenigstens einem oder mehreren bekannten, insbesondere vorgespeicherten Spektren zum Erkennen von Übereinstimmungen bzw. um ggf. vorhandene Übereinstimmungen zu erkennen, wobei im Schritt 300 eine Aussage über den Zustand des Ausgangsproduktes (P) aus dem Vergleich und Erkennen von Übereinstimmungen aus Schritt 300 getroffen wird.

The invention creates a method for detecting the operating state of a centrifuge, which has at least one rotatable drum with an inlet pipe and with at least one liquid outlet and / or a solids outlet, with which, during operation, a flowable starting product in the centrifugal field of the rotating drum into different liquids. and/or solid phases is separated, with at least the following steps for recognizing the operating state:

100

Detecting a time profile of a structure-borne sound signal with at least one structure-borne sound sensor arranged on a component of the drum or in the vicinity of a component of the drum, in particular with a predetermined sampling rate;

200

Transformation of the structure-borne sound signal recorded into a vibration or frequency spectrum;

300

Comparison of the currently determined spectrum with at least one or more known, in particular pre-stored, spectra to recognize matches or to recognize any matches that may be present, wherein in step 300 a statement about the state of the output product (P) is made from the comparison and recognition of matches from step 300 is taken.

An advantageous possibility of the invention is therefore the detection of a specific operating state (e.g. drum overflow) of the centrifuge - in particular a disc separator or a solid bowl screw centrifuge - by means of a structure-borne sound measurement or a corresponding vibration measurement during a time interval and by carrying out the transformation - for example a Fourier transformation - possible Analysis of the measurement signals by comparing the resulting spectrum with previously known spectra. These previously known spectra were preferably determined through experiments and then saved. However, it is also conceivable that they were determined through simulation calculations. The previously known and pre-stored “reference spectra” can include both those spectra that correspond to a problem or malfunction those that indicate trouble-free operation, which can be described as “normal operating patterns”.

When measuring structure-borne sound or vibration in the context of this invention, both the measurement of the vibration speed and acceleration can be used. Electrodynamic speed sensors, laser Doppler sensors, capacitive acceleration sensors, piezoelectric acceleration sensors or piezoresistive acceleration sensors can therefore be used.

This makes it possible to operate the centrifuge closer to the mechanical load limit or to reduce previously necessary mechanical reserves. The now recognizable changes in the operating status of the centrifuge can also be used to draw conclusions about changes in the product to be processed or changes in the technical process.

According to an advantageous variant, it is possible - in particular in real time - to monitor the overflow of the centrifuge drum or cavitation on the gripper of the centripetal pump during the process. A direct detection of these operating states was not possible according to the state of the art, so preset parameters such as inlet flow and/or outlet flow and/or outlet pressure were evaluated or moisture was detected. These systems sometimes work with a time delay, so that reliable detection of certain operating states was not always possible and permissible limit values of the machine according to the state of the art could not always be sufficiently exploited (in the sense of maintaining reserves). This made the operation of the separators less economical. This problem is reduced with the invention.

According to a further development, one or more actions can be initiated depending on the recognition of the operating state according to step 400, whereby initiating the one or more actions can include issuing a warning message or where initiating one or more actions can include issuing a control signal for changing the operation of the centrifuge.

• Geräuschentwicklung der Maschine bzw. der Flüssigkeitsströmung,
• Vermeidung von Emulsionsbildung in der zu verarbeitenden Suspension,
• Reduzierung der Beanspruchung von Bauteilen,
• weniger Gaseinschlag in die Suspension.

Reliable detection and avoidance of undesirable operating states can be used for optimized operational control. For example, the following factors can be optimized:

• Noise development from the machine or the liquid flow,
• Avoidance of emulsion formation in the suspension to be processed,
• Reduction of the stress on components,
• less gas penetration into the suspension.

If an undesirable operating state is recognized based on its typical vibration spectrum, the control of the machine can optionally trigger predetermined reactions in step 400.

With the help of the determined spectrum and the comparison of this spectrum with previously known spectra, not only can certain machine states be detected, but changes in the product to be processed as well as one or more deviations from the previously defined process parameters can also be recognized. If, for example, the viscosity or density of the suspension to be processed changes in such a way that the permissible value range for the centrifuge is exceeded or fallen below, this is also from the spectrum determined on the centrifuge drum - for example on the inlet pipe - by comparison with the previously known spectra recognizable.

According to a particularly advantageous variant of the invention, in step 100 a structure-borne sound sensor arranged on a component of the centrifuge that does not rotate during operation of the centrifuge, in particular a structure-borne sound sensor arranged on a component that does not rotate during operation of the centrifuge in the area of the centrifuge drum, can be used. Because it has surprisingly turned out that directly on such a part - on which the respective sensor is relatively easy to attach and can be read easily via a wired cable or wirelessly - characteristic vibrations also occur to a sufficient extent in the rotating system and with the structure-borne noise sensor can be detected in order to record and distinguish between different or multiple operating states of the centrifuge to be able to. According to advantageous variants of the invention - since they are easy to implement and lead to good results - a structure-borne sound sensor arranged on an inlet pipe that does not rotate during operation of the centrifuge and/or on a start-up, in particular on a gripper, can be used. Alternatively, it is conceivable to arrange a suitable structure-borne sound sensor near this component.

It has also surprisingly been found that it is advantageous if in step 300 at least one of the pre-stored spectra corresponds to an operating state "current or impending overflow of the drum" and if step 300 possibly includes recognition of this operating state. This operating state can be recorded particularly well with the method according to the invention, which allows the operation of the centrifuge to be optimized in a simple manner.

It is also expedient if in step 300 at least one of the pre-stored spectra corresponds to an operating state “current or impending cavitation on the gripper of the centripetal pump” and that step 300 further includes recognizing this operating state.

Further advantageous embodiments of the method according to the invention can be found in the subclaims.

Figur 1:

eine schematische Schnittansicht einer Zentrifuge, welche nach einem erfindungsgemäßen Verfahren betrieben werden kann;

Figur 2:

ein beispielhaftes Diagramm, das den Signalverlauf einer Körperschallmessung über die Zeit an einem Einlaufrohr einer Zentrifugentrommel zeigt;

Figur 3:

ein mittels einer Körperschallmessung an einem Einlaufrohr einer Zentrifugentrommel aufgenommenes Schwingungsspektrum; und

Figur 4

ein Flussdiagramm eines erfindungsgemäßen Verfahrens.

The invention is explained in more detail below using a preferred exemplary embodiment with reference to the accompanying drawings. This exemplary embodiment shows a particularly preferred variant of the invention, but modifications and equivalents as well as further developments to the exemplary embodiment explained can be implemented within the scope of the claims. The use of the indefinite article such as “one” or “one” is not to be understood as a restrictive numerical indication but rather in the sense of “at least one/one or more”. It shows:

Figure 1:

a schematic sectional view of a centrifuge which can be operated using a method according to the invention;

Figure 2:

an exemplary diagram showing the signal curve of a structure-borne noise measurement over time on an inlet pipe of a centrifuge drum;

Figure 3:

a vibration spectrum recorded by means of a structure-borne noise measurement on an inlet pipe of a centrifuge drum; and

Figure 4

a flowchart of a method according to the invention.

Fig. 1 shows a centrifuge - here designed as a separator - for clarifying solids-containing, flowable starting products P from solids with a rotatable drum 1 with a vertical axis of rotation. The starting product P is processed in continuous operation. The separator is a self-draining separator.

This means that the feed of the starting product P - which is a flowable suspension - takes place continuously and the discharge of at least one clarified liquid phase, called clear phase L, also takes place continuously. The drum 1 of the centrifuge, in the design as a self-emptying separator, has a discontinuous solids outlet, whereby the solid separated from the starting product P by clarification is removed at intervals by opening and re-closing outlet nozzles or outlet openings 5. Each of the phases resulting from this separation can - but does not necessarily have to - form a valuable material phase to be recovered. Alternatively, the invention can also be used on nozzle separators or on separators without a solids outlet. It can also be used on separators that do not work continuously in batch operation.

The drum 1 has a drum base 10 and a drum cover 11. It is also preferably surrounded by a hood 12. The drum 1 is also placed on a drive spindle 2, which is rotatably mounted and can be driven by a drive motor. The drum 1 itself is rotatable or forms an essential part of the rotating system of the centrifuge, but it also has individual elements protruding into it that do not rotate during operation.

The drum 1 has a product inlet 4 through which the starting product P is passed into the drum 1. The product inlet 4 opens into an inlet pipe 40, which is designed here as a tube that does not rotate with the rotating system - i.e. does not rotate during operation - and which projects into the drum from above and is aligned coaxially with the axis of rotation D. Alternatively, it would also be conceivable for the inlet pipe 40 to protrude into the drum from below (with a correspondingly different design - not shown here).

The drum 1 also has at least one drain 13 - which is designed here as a peeling disk or as a gripper - which serves to derive a clear phase L from the drum 1. The gripper acts like or forms a centripetal pump. The process 13 can also be carried out constructively in a different way or with other means. It is also conceivable, as an alternative or in addition to the clarification of solids, to separate the starting product P into two liquid phases of different densities. For this purpose, another liquid drain - for example another gripper - is required. The gripper 13 thus also forms a component of the centrifuge that does not rotate with the actual drum 1 during operation but is stationary.

The drum 1 preferably has a plate pack 14 made of axially spaced separating plates. A solids collecting space 8 is formed between the outer circumference of the plate pack 14 and the inner circumference of the drum 1 in the area of its largest inner diameter. Solids, which are separated from the clear phase in the area of the plate stack 14, collect in the solids collecting space 8, from which the solids can be discharged from the drum 1 via outlet openings 5.

For this purpose, the outlet openings 5 can be opened and closed here by means of a piston slide 6, which is arranged in the lower drum part 10 and can be displaced parallel to the axis of rotation (in particular vertically). When the outlet openings 5 are open, the solid S is discharged from the drum 1 into a solids catcher 7. The solids collection space 8 in the drum 1 has a defined solids space volume.

The drum 1 has an actuation mechanism for moving the piston slide 6. Here this includes at least one supply line 15 for a control fluid such as water and a valve arrangement 16 in the drum 1 and further elements outside the drum 1. The inflow of the control fluid such as water is made possible via a metering arrangement 17 arranged outside the drum 1, which is one outside the drum 1 arranged hydraulic line 19 for the control fluid is assigned, so that for a solids emptying of the solids by releasing the valve arrangement 16, the control fluid can be introduced into the drum 1 or, conversely, the inflow of control fluid can be interrupted in order to move the piston slide 6 accordingly, to release the outlet openings 5.

At least one structure-borne sound sensor 22 is arranged on a component of the drum - for example on the inlet pipe 40 - and is designed to record a vibration spectrum. This structure-borne noise sensor 22 is designed as a sensor device for measuring structure-borne noise.

The structure-borne sound to be measured or sensed is the sound that propagates in the component on which the structure-borne sound sensor 22 is arranged. Acceleration sensors can be used as structure-borne sound sensors, which use an effect, for example the piezoelectric effect, to convert the acceleration that occurs as a result of structure-borne sound on the component on which they are arranged into electrically processable signals.

But other sensors such as electrodynamic speed sensors, laser Doppler sensors, capacitive acceleration sensors or piezoresistive acceleration sensors can also be used.

Within the scope of the invention, it is also conceivable to arrange several of the structure-borne sound sensors 22 on one component and/or to arrange structure-borne sound sensors on several components of the centrifuge drum (not shown here) or sensors 20 below the drum 1 in the vicinity of a part of the drum or of the rotating system (e.g. spindle, drum base, etc.).

According to an advantageous variant of the invention, it is provided to provide the at least one structure-borne noise sensor 22 on a component of the centrifuge drum 1 that does not rotate during operation, in particular on the inlet pipe 40 (illustrated here) and/or on the gripper 13 (not shown here). .

Additional sensor devices can optionally be provided, such as a sensor device 3 for determining the flow rate volume/time or one or more parameters, such as mass/time, of the starting product P to be conducted into the drum 1. This is advantageous, but not mandatory.

The structure-borne sound sensor 22 either has evaluation electronics itself or is connected to one. Here, the structure-borne noise sensor 22 is connected, for example, via a data connection 23 to the control and evaluation device 9 (preferably a control computer of the centrifuge), which evaluates the measured values determined.

The system of the drum 1, which rotates during operation, generates structure-borne sound waves both on the components of the drum 1 that rotate during operation and on the components of the drum 1 that do not rotate during operation.

Fig. 2 illustrates by way of example the time signal curve of a structure-borne noise measurement recorded during the operation of an exemplary centrifuge. Fig. 3 shows a frequency spectrum obtained through a transformation. Resonance frequencies known in the system (here around 100 Hz) are clearly visible.

The structure-borne noise sensor 22 can preferably be arranged on the surface of one of the components. But it can also be inserted into a hole or the like in the component. The structure-borne sound sensor 22 is preferably designed to be broadband and designed to measure a relatively wide frequency spectrum, for example between 0Hz and 1 MHz. However, it is also conceivable to tune it relatively precisely to a smaller frequency range to be measured.

Preferably, the analog signal recorded by the structure-borne sound sensor 22 is digitized by the evaluation electronics 9 and stored as a signal curve. Through appropriate filtering, transformation and subsequent analysis of the recorded signal, conclusions can be drawn about the operating status of the centrifuge. This is made possible in particular by making a comparison with previously known spectra that correspond to different operating states.

The control and evaluation device 9 can also serve to control the movement of the piston slide 6 and thus also the time interval until the outlet openings 5 are opened. The actuating mechanism for the piston slide 6 - here in particular the metering arrangement 17 - can be connected to the evaluation and control and evaluation device 9 via a data connection 18. The control and evaluation device has a computer program with a program routine for monitoring and/or controlling and/or regulating the operation. The metering arrangement 17 can, for example, have a piston and one or more valves. It can also be of the type DE 10 2005 049 941 A1 be designed to be able to carry out a variable dosage of the amount of fluid to control and change the duration of the solids emptying and thus the current solids emptying volume. With the metering arrangement 17, the solids emptying volume can be varied, so that, for example, if the solids content in the inlet increases, the solids emptying volume can be increased. A controllable device - for example a controllable valve - can be connected to the inlet, with which the volume flow in the inlet can be changed in order to change the inlet quantity or the current inlet volume V _AP of output product P to be processed per unit of time. This controllable device can be connected to the control and evaluation device 9 via a data connection (not shown here). The aforementioned data connections enable data transmission from or to the control and evaluation device 9. They can each be designed as lines or as wireless connections.

During the clarification of the starting product P to form the clear phase L, trub and other solids contained in the starting product P are collected in the solids collection space 8 of the drum 1 outside the plate pack 14, which fills up.

The signal recorded by the structure-borne sound sensor 22 and the vibration spectrum determined from this now enables a particularly simple and well-functioning determination of the operating state of the centrifuge. This in turn can be used, for example, to monitor and/or control and/or regulate the centrifuge.

This is described in more detail below. The structure-borne sound sensor 22 on the stationary inlet pipe 40 is an example of at least one structure-borne sound sensor which is arranged outside, on or in the drum 1, in particular on a part of the drum 1 that does not rotate during operation.

100

Erfassen eines bzw. des zeitlichen Verlaufs eines Körperschallsignals mit wenigstens einem an einem Bauteil der Trommel oder in der Nähe eines Bauteils der Trommel angeordneten Körperschallsensor 22;

200

Transformation des jeweils aufgenommenen Körperschallsignales in ein Spektrum, insbesondere ein Frequenzspektrum;

300

Vergleich des aktuell ermittelten Spektrums mit wenigstens einem oder mehreren bekannten, insbesondere vorgespeicherten Spektren zum Erkennen bzw. und Erkennen von Übereinstimmungen; und

400

vorzugsweise Ausgeben einer Information, insbesondere einer Warnung und/oder eines Steuerungssignales in Abhängigkeit von dem Vergleich aus Schritt 300.

The following method is then used for detecting the operating state of a centrifuge while carrying out a centrifugal separation of a suspension into at least a first liquid phase and at least one further liquid phase and / or a solid phase in a rotating drum of the centrifuge with the steps 100 to 300 defined at the beginning and if necessary - if necessary - 400 carried out:

100

Detecting one or the time course of a structure-borne sound signal with at least one structure-borne sound sensor 22 arranged on a component of the drum or in the vicinity of a component of the drum;

200

Transformation of the respectively recorded structure-borne sound signal into a spectrum, in particular a frequency spectrum;

300

Comparison of the currently determined spectrum with at least one or more known, in particular pre-stored, spectra for recognizing or recognizing matches; and

400

preferably outputting information, in particular a warning and/or a control signal, depending on the comparison from step 300.

In step 300, the comparison with the known spectrums, in particular frequency spectra, can include including a tolerance range in order to obtain matches to recognize. Accordingly, the output of information in step 400, for example a warning and/or control signal, would only occur if a signal lying outside an expected tolerance range is detected.

• Schwingweg,
• Schwinggeschwindigkeit und/oder
• Beschleunigung

With the structure-borne sound sensor 22, structure-borne sound measurement signals are preferably continuously recorded during operation of the centrifuge (see Fig. 2 ) and - for example using Fourier transformation - into a spectrum (see example Fig. 3 ) transformed. Depending on the sensor, one or more of the following parameters, in particular all of the following parameters, can preferably be recorded:

• swing path,
• Vibration speed and/or
• acceleration

Typically, the structure-borne sound sensor 22 and the signal processing associated with it of the evaluation and control and evaluation device 9 should be designed and therefore suitable for detecting and processing signals with a high sampling rate. This high sampling rate should preferably be greater than 50 kHz and particularly preferably greater than 100 kHz.

The vibration signal recorded in each case is digitized and the spectrum of the vibration signal is generated from the recorded vibration signal using a suitable algorithm for carrying out the mathematical transformation. This spectrum is compared with various known spectra stored in a database, which preferably correspond to different machine states, product states or process states. In this way, various states - for example normal states that indicate trouble-free operation - and/or deviations from such states can be recognized in step 300. In addition, depending on this detection in step 300, one or more actions can be initiated in a further step 400, with which, for example, a desired state is achieved again.

Spectra can be pre-stored which correspond to the operating states “current or impending overflow of the drum” or “current or impending cavitation on the gripper” so that these can be based on the ongoing structure-borne sound measurements and the ongoing comparisons of the recorded spectra with the known spectra can be detected.

With real-time “drum overflow” detection, the flow rate can be increased more safely compared to the old system. This means, among other things, that an uneconomical operating state can be detected. Process optimization can take place in real time. Furthermore, by analyzing the vibration patterns, further statements about the operating state of the separator are conceivable.

If an undesirable operating state is recognized based on its typical vibration spectrum, the machine control can trigger predefined reactions, such as "Detected operating state of overflow of the drum" - reaction: "Reduction of the inlet quantity and/or reduction of the outlet pressure" or "Detected operating state of cavitation on the gripper " Action: "Increase drain pressure and thus increase the immersion depth of the gripper".

However, the frequency spectrum can not only detect certain machine states, but can also detect deviations from previously defined product and/or process parameters. If, for example, the viscosity or the flow rate of the suspension to be processed changes in such a way that the permissible value range for the centrifuge is exceeded or fallen below, this can also be recognized by the vibration spectrum determined on the inlet pipe.

Further examples of conditions that can be identified using the process and the resulting possible countermeasures: "Operation with a product of too high a density" - Action: "Switch off the centrifuge" or "Operation with a product with insufficient precipitation" - Action: "Extension the residence time of the product in the precipitation container upstream of the centrifuge.

Overall, with the methods presented and claimed, the possibilities for diagnosing the condition of the machine, the product and the process engineering process are advantageously increased and the possibilities for corrective actions are also improved.

Reference symbol list

1

drum

2

spindle

3

sensor

4

Product inflow

5

Exhaust openings

6

Piston valve

7

solids catcher

8th

Solids collection room

9

Control and evaluation device

10

drum base

11

Drum cover

12

Hood

13

Sequence

14

Plate package

15

Line for hydraulic fluid

16

Valve arrangement

17

Dosing arrangement

18

Data Connection

19

Hydraulic line

20

sensor

21

Data Connection

22

Structure-borne sound sensor

23

Data Connection

40

Inlet pipe

100 - 400

Procedural steps

L

Clear phase

P

Starting product

S

solid

D

Axis of rotation

Claims (11)

1. Method for detecting the operating state of a centrifuge which has at least one rotatable drum (1) having an inlet pipe (40) and having at least one liquid outlet (13) and/or a solids outlet, by means of which, during operation, a flowable starting product (P) is separated in the centrifugal field of the rotating drum (1) into different liquid and/or solids phases, having at least the following steps for detecting the operating state: 100 detection of a temporal course of a structure-borne sound signal with at least one structure-borne sound sensor (22, 20) arranged on a component of the drum or in the vicinity of a component of the drum (1), in particular with a predetermined sampling rate; 200 transformation of the respectively recorded structure-borne sound signal into a vibration or frequency spectrum; 300 comparison of the currently determined spectrum with at least one or more known, in particular pre-stored, spectra for detecting matches, characterized in that
   in step 300 a statement is made about the state of the starting product (P) from the comparison and recognition of matches from step 300.
2. Method according to claim 1, characterized in that in step 100 a structure-borne sound sensor (22) arranged on a component of the centrifuge which does not rotate during operation of the centrifuge is used.
3. Method according to claim 2, characterized in that in step 100 a structure-borne sound sensor (22) arranged on a component of the centrifuge drum (1) which does not rotate during operation of the centrifuge, in particular inside the centrifuge drum (1), is used.
4. Method according to claim 3, characterized in that in step 100 a structure-borne sound sensor (22) arranged on an inlet pipe (40) not rotating during operation of the centrifuge and/or on an outlet, in particular on a gripper (13), is used.
5. Method according to one of the preceding claims, characterized in that in step 300 at least one of the pre-stored spectra corresponds to an operating state "trouble-free operation" and in that step 300 optionally comprises a recognition of this operating state.
6. Method according to one of the preceding claims, characterized in that in step 300 at least one of the pre-stored spectra corresponds to an operating state "current or threatened overflow of the drum" and in that step 300 optionally comprises a recognition of this operating state.
7. Method according to one of the preceding claims, characterized in that in step 300 at least one of the pre-stored spectra corresponds to an operating state "current or threatened cavitation at the gripper" and in that step 300 optionally comprises a recognition of this operating state.
8. Method according to one of the preceding claims, characterized in that in step 300 a statement is made about the state of the process-engineering process from the comparison and the recognition of matches from step 300.
9. Method according to one of the preceding claims, characterized in that, depending on the detection of the operating state or the state of the starting product (P) or the state of the process-engineering process according to step 300, one or more actions are initiated in a further step 400.
10. Method according to claim 9, characterized in that initiating one or more action(s) according to step 400 comprises issuing a warning message.
11. Method according to one of the preceding claims 9 or 10, characterized in that initiating one or more action(s) according to step 400 comprises outputting a control signal for changing the operation of the centrifuge.

Images