Method and device for monitoring centrifuge

Abstract

The invention relates to a method and to a corresponding device (VO) for monitoring a centrifuge (Z) for the solid-liquid separation of a suspension (SUS), comprising a centrifuge drum (T) which is connected to at least one frequency-controlled drive in order to generate a rotation of the centrifuge drum (T), the rotation of the centrifuge drum (T) being controlled during the operation of the centrifuge during the course of the separation process. According to the invention, a plurality of variables and parameters of the drive are determined as a function of time, and a periodic operating mode (I, II, III, IV) of the operation of the centrifuge is derived from the correlation of the variables and parameters of the drive, and information about the separation process is automatically determined as a function of the derived operating mode.

Description

Technical Field

[0001] The invention relates to a method for monitoring a centrifuge for solid-liquid separation of a suspension and to a corresponding device. The invention also relates to a corresponding computer program product. Background Art

[0002] A centrifuge is a technical device for separating substances. The operating mode of a centrifuge is based on the centrifugal force that is achieved by the same circular motion of the items to be centrifuged. Particles or media with a higher density migrate to the outside due to their greater inertia. In the process, components with a lower density are squeezed out and thus reach the center.

[0003] Centrifuges such as scraper centrifuges are often used in the pharmaceutical industry or the food industry (e.g. in the extraction of sugar) for the solid-liquid separation of suspensions. Such centrifuges are usually operated according to a preset time-fixed program: the suspension is fed from the reactor into the centrifuge via a time-controlled valve, wherein the time is limited based on empirical values ​​due to the risk of overfilling. The centrifuge has a centrifuge drum which is filled with the suspension as fill material at the beginning of each working step, wherein the centrifuge is initially operated at a first speed (filling speed DZ1, see Figure 2 ) rotates. The centrifuge drum is then accelerated to a second speed (centrifugal separation speed DZ2, which is significantly higher than the first speed) Figure 2 ). This speed is maintained until the desired drying progress is achieved in the filling material. The so-called filter cake remains on the filter cloth. Subsequently, the centrifuge drum is braked to the stripping speed (DZ3, Figure 2 ) and the filling material is removed from the centrifuge bowl by means of a cleaning device or stripping device. After a certain number of these types of processes, the filtration resistance is usually so high due to the added filter cloth or the non-removable substrate that a basic cleaning is necessary. Centrifuges of this type (sieve centrifuges, scraper discharge centrifuges) are often used for the batch production of substances in the pharmaceutical industry.

[0004] The throughput of a centrifuge depends on the filtration resistance, which in turn depends on the particle size distribution. Slight fluctuations in the particle size can lead to significantly different separation times. Therefore, the time control must be parameterized very accurately. Conventionally, for each batch, the parameters necessary for optimal centrifuge operation, such as the mass delivered for material separation and the speed used, are set manually by the centrifuge operator based on empirical values. In traditional condition monitoring, the technical status of the unit is recorded regularly or permanently with the help of sensors and the sensor data obtained is analyzed for subsequent use. However, for centrifuges, this traditional condition monitoring becomes difficult because it is also difficult to place sensors in the separation space inside the centrifuge drum. In addition, traditional sensor technology equipment is always exposed to significant contamination caused by suspensions.

[0005] Some scraper centrifuges have a "paddle" that slides on the rotating liquid or the filter cake separated therefrom with the help of a displacement sensor and thus allows the centrifuge level to be assessed. Unfortunately, these mechanical sensors can transmit incorrect values ​​due to agglomeration of the suspension and, for example, get stuck. As a result, it is not possible to accurately monitor the separation process or the centrifuge status. Non-contact optical sensors with the help of lasers or ultrasound are also prone to malfunctions and difficult to use due to contamination with a high solid content. Therefore, it is necessary to monitor the operation of the centrifuge contactlessly but accurately to ensure a smooth and error-free separation process without installing complex sensor technology equipment on the centrifuge itself or setting unnecessarily short filling times or excessively long centrifugal swing times and thus restricting the throughput capacity of the centrifuge. Summary of the invention

[0006] The object of the present invention is to specify an improved method for monitoring a centrifuge and a separation process to be performed, wherein no sensor technology needs to be arranged in or on the centrifuge.

[0007] This object is achieved by the features of independent claim 1. Advantageous developments of the invention are described in the dependent claims, and claim 9 describes a computer program product.

[0008] The core idea of ​​the invention is to evaluate variables and parameters of a centrifuge drive which are already available for controlling and regulating the centrifuge so that they can be used to monitor the separation process. This can be physical variables such as current, voltage, rotational speed (angular velocity) or torque, but also variables derived therefrom with corresponding parameters such as moment of inertia, angular momentum of the centrifuge drum or mass inflow. The method according to the invention is therefore based both on simple data available from measurement technology, such as current or voltage, and on computationally derived data.

[0009] Therefore, a method for monitoring a centrifuge for solid-liquid separation of suspensions is proposed, the centrifuge comprising a centrifuge drum which is connected to at least one frequency-controlled drive for generating a rotation of the centrifuge drum, wherein during operation of the centrifuge, in the course of a separation process, a plurality of variables and parameters of the drive are determined in a time-dependent manner, and based on the mutual relationship of the variables and parameters of the drive, an operating pattern of a cycle of the centrifuge operation is derived and information about the separation process is automatically derived based on the derived operating pattern.

[0010] The method according to the invention has the advantage that it is possible to provide monitoring of the separation process and the centrifuge itself based on existing variables and parameters of the drive without requiring additional sensor technology equipment. Thus, the invention does not require special additional measuring instruments, but uses instrumentation that is usually already available in frequency converters.

[0011] Advantageously, the method can be implemented in software or firmware at the control level or in a cloud environment and can therefore be flexibly commissioned. In principle, every centrifuge can be equipped with "intelligent" monitoring software based on the method according to the invention. All that is required is a software module suitable for the evaluation. However, the method is particularly suitable for scraper centrifuges or screen centrifuges with batch operation management, wherein different operating modes can be derived within an operating cycle.

[0012] In a first embodiment variant, the filling degree of the centrifuge drum can advantageously be determined or the mass contained therein can be determined. In this embodiment, the centrifuge is monitored so that, in order to deduce the filling pattern, the rotational speed of the drum and the energy of the drive required at least to maintain the rotational speed of the drum are recorded over time and the increase in the rotational inertia of the drum caused by the filling is derived from this. The filled (rotational) mass of the centrifuge drum can thus be determined in a simple manner.

[0013] This embodiment variant is particularly suitable for the operation mode in which the centrifuge drum rotates at the filling speed. First, it is determined how much power the centrifuge consumes in the unloaded state and at a constant speed, and the moment of inertia of the unloaded drum can be derived from this. The centrifuge is then filled (the valve for the mass inflow of the suspension is opened). When the drum is filled, the incoming mass flow must be accelerated to its angular velocity, and the power consumed by the power converter (at a constant angular velocity) is recorded as the additional energy required to accelerate the additional (inflowing) mass. This additional energy is used to derive the mass of the drum filling. The filling valve is then closed. The power consumption of the converter in the filling process is thus significantly increased. Therefore, the integral of the current consumption at this speed is higher than the idling current consumption is a measure of the corresponding mass loaded. Therefore, if the speed is known, the moment of inertia of the centrifuge drum can be simply inferred from the electrical energy required by the drive. When determining the moment of inertia, the centrifuge drum can always be regarded as a hollow cylinder, because the radius of the centrifuge is usually very large relative to the almost negligible layer thickness of the filling material in the drum.

[0014] The advantage of this embodiment variant is that the filling degree of the centrifuge can be determined very simply but quite accurately. Based on the trend of the current or electrical power, the energy required to accelerate the rotating mass, which is characteristic of the filling process, can be measured accurately. The virtual mass growth during the filling process is characteristic of this process.

[0015] For further evaluation, it is essential to determine the idling torque (or the moment of inertia of the drum when unloaded) or the unloaded weight of the drum. Here, the additional energy required to increase the moment of inertia for the centrifuge drum is determined when unloaded during the transition from a first rotational speed (preferably the stripping rotational speed) to a second rotational speed (preferably the filling rotational speed). The (rotating) mass of the unloaded drum is now inferred from this. This is particularly important if the filling degree of a filled centrifuge drum cannot be determined solely by the increase in energy. In this way, the dead weight of a centrifuge drum, which is often very heavy and large, as occurs, for example, in the sugar industry, can be determined very simply.

[0016] In another advantageous embodiment variant, the filling degree of the centrifuge can also be determined simply and accurately. This embodiment variant is particularly suitable for high rotational speeds, i.e., for the rotational speed of the operating mode in which the centrifuge drum rotates at the centrifugal separation speed. Here, based on the mutual relationship of the variables and parameters of the recorded drive, the operating mode "centrifugal drying" is first derived, and the rotational speed of the drum rotation is then periodically changed over time, and the time change of the angular velocity is measured. From this, the energy for acceleration and braking of the drum is derived and the moment of inertia of the drum is calculated. When the zero mass (derived from the moment of inertia of the centrifuge when empty) is known, the filling degree of the centrifuge drum can be determined with the help of the moment of inertia of the rotating mass.

[0017] The advantage of this variant is that small changes in the rotational speed have no effect on the separation process, but the energy changes caused by the acceleration and braking of the drum can be easily measured via the change in angular velocity over time. As in the first variant, the change in energy can be used to infer the moment of inertia of the drum and thus the filling degree.

[0018] In another advantageous embodiment variant, at high speed, the residual moisture of the filter cake is determined by comparing the rotational mass of at least two cycles of speed change. In this embodiment variant, at the centrifugal separation speed of the centrifuge drum, the speed is changed for the first time, the rotational mass is determined, and the process is repeated at least once. If the mass determined in this way no longer changes, there is no longer any residual moisture for centrifugation in the observed filter cake. The determined mass is constant in the case of complete dehumidification. In this way, the residual moisture of the filter cake can be determined very efficiently without intervening in the separation process, for example by sampling. Further, no additional operating costs for the centrifuge are generated. On the one hand, according to this embodiment, the determination of the residual moisture is advantageously integrated into the current operating mode of the centrifuge, and on the other hand, the centrifugal separation process can be terminated when a certain cake dryness is reached. Finally, if the centrifugal process is terminated earlier than initially specified based on empirical values, the operating costs of the centrifuge can even be reduced by means of this embodiment variant.

[0019] In a particularly advantageous variant of the invention, the energy required to maintain or change the rotation of the centrifuge drum is determined in the frequency-dependent converter by means of an integrator. No additional sensor technology equipment is necessary. Thus, the existing measurement architecture is optimally utilized.

[0020] All embodiments of the method according to the invention lead to improved monitoring of the centrifuge, since the evaluation of the existing variables provides a higher degree of accuracy and can be performed fully automatically. The method according to the invention can be provided as a stand-alone application in a process facility or in a local or remote computer system ("cloud"), for example by a service provider in the form of "software as a service".

[0021] The described developments relate both to the method according to the invention and to the device.

[0022] The present invention and / or any of the described developments can also be implemented by a computer program product, in particular a software application, having a storage medium on which a computer program is stored that implements the present invention and / or the developments.

[0023] Advantageously, the computer program product can be transferred to a random access memory of a computing unit and can be executed therefrom by means of at least one CPU. Advantageously, the computer program product can be stored on a data storage device, such as a USB, hard disk or CD-ROM / DVD-ROM, and can be called up or installed therefrom on the computing unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Hereinafter, the present invention is described and explained in more detail based on the embodiments shown in the drawings.

[0025] In the attached drawings, a simplified schematic diagram is shown:

[0026] Figure 1 Block diagram of a horizontal centrifuge and a device for monitoring a centrifuge,

[0027] Figure 2 Graphs of different time trajectories of variables for monitoring a centrifuge during a centrifuge operation cycle, related to different embodiments of the present invention,

[0028] Figure 3 The time trajectory of the inflow and the required motor current in the operating mode resulting from the filling degree of the centrifuge drum according to the first embodiment of the invention is:

[0029] Figure 4 A time trajectory of the rotation speed of a centrifuge according to a further embodiment of the present invention. DETAILED DESCRIPTION

[0030] Figure 1 A simplified block diagram of a horizontal centrifuge Z for solid-liquid separation of a suspension SUS is shown in an exemplary manner. The centrifuge Z has a centrifuge drum T into which the suspension SUS is fed via a pipeline that can be closed by a valve V. The centrifuge drum T has an axis of rotation A that coincides with the axis of symmetry of the centrifuge drum and is located at Figure 1 The centrifuge is arranged to extend horizontally. At any two points of the rotating shaft, there is at least one bearing at each point for support.

[0031] In the embodiment shown, the suspension SUS is introduced into the interior of the centrifuge drum T by means of a so-called filling scraper. In centrifugal mode, the filling material rests on the cylindrical wall of the drum with a substantially uniform thickness due to the centrifugal force. In order to press the liquid through the so-called filter cake, the horizontal centrifuge is accelerated. Centrifugation is continued until the desired residual moisture of the filter cake is reached. When the speed is reduced, the stripping knife SM swings into the filter cake and in this embodiment variant strips the product P vertically downwards via the discharge device.

[0032] For the operation of the centrifuge Z, the centrifuge is connected to a frequency-controlled drive to generate a rotation of the centrifuge drum T. The frequency-controlled drive comprises at least one frequency converter FU, which generates an alternating voltage suitable for the motor from the supplied alternating voltage. The converter FU is connected on the one hand to the three-phase AC motor M and on the other hand to a programmable logic controller SPS for controlling the operation of the motor. The converter has a speed regulating device D, which makes it possible to set any speed of the rotating shaft (physical: angular velocity ω) of the centrifuge drum.

[0033] exist Figure 1 The device VO for monitoring a centrifuge according to the invention, shown by way of example in FIG. , comprises at least one interface (S1, S2, S3) for receiving and exchanging signals of at least one of the motor M, the frequency converter FU and / or the programmable logic controller SPS. Alternatively, the device VO can also have a single interface designed to receive any desired signals and / or data.

[0034] Furthermore, the device VO comprises an evaluation unit AS which is designed to carry out the method according to the invention and which, based on the signals provided, during the operation of the centrifuge Z, in the course of the separation process, records a plurality of variables and parameters of the drive in a time-dependent manner and, based on the mutual relationships between the variables and parameters, derives the operating mode of the centrifuge and, based on the derived operating mode, automatically derives information about the separation process and / or the centrifuge state. The evaluation unit thus serves as a monitoring device and can display the previously determined information to a user via a connection to a display device. According to the invention, this can be the filling degree of the centrifuge or the residual moisture of the filter cake. In principle (not discussed in further detail here), this can also be information about the wear of centrifuge components, such as bearings of the centrifuge bowl or an existing imbalance (=non-rotationally symmetrical mass distribution in a rotating body).

[0035] For this purpose, the evaluation unit AS further comprises at least one processor unit P, at least one memory or archive Sp for storing received signals and at least one memory R in which a program PR with instructions is stored, which executes one of the above-described methods when the program is executed by the processor unit P. The implementation of the invention as a computer program PR can be stored in a working memory R or loaded into the working memory, for example, and can be executed from the working memory by means of at least one processor P.

[0036] Furthermore, the device can have a display unit or be connected to a display unit which is designed such that the centrifuges of the process engineering installation can be monitored on a user interface GUI. The user can interact with the evaluation unit AS of the device VO as desired via the graphical user interface.

[0037] Figure 2 The present invention shows a graph of variables with different time trajectories for monitoring a centrifuge during its operating cycle, in accordance with various embodiments of the invention. The time t is plotted in ms on the abscissa. On the ordinate, various variables are plotted as an example for the operating cycle of a scraper centrifuge for batch operation, with a respective coordinate axis including a corresponding scale being provided for each variable. The bottom curve refers to the measured rotational speed UM of the centrifuge drum. 实际 The measured speed is expressed in revolutions per minute n (rpm) and is proportional to the physical variable of the angular velocity ω. The specified nominal value UM of the number of revolutions of the centrifuge drum in the same unit is superimposed on the measured speed. 额定 Further, the graph shows the motor current I required to drive the centrifuge drum T in A. M and the required electrical power P in kW elTo further understand the operation of the centrifuge, the drum torque M in Nm is used. T The time trajectory of the centrifuge can be compared with the trajectory of other variables. Thus, during operation of the centrifuge, a plurality of variables and parameters of the drive can be determined and analyzed in a time-dependent manner during the course of the separation process.

[0038] By comparing the variables relevant to the operation of the centrifuge, the interrelationships of the variables and parameters are disclosed, from which the individual operating modes of the cycle of the centrifuge operation can be derived. Figure 2 These operating modes are marked with Roman numerals I to IV in the diagram. Information about the separation process can now be automatically derived for each of these operating modes, for example by evaluating the corresponding signals of the motor and the converter. The time series of the drive variables and parameters, in relation to one another, are characteristic of each operating mode. (See the difference in the curve trajectories of the operating modes "centrifugal separation" II and "centrifugal drying" III.)

[0039] In operating mode I, the centrifuge is filled. The unloaded drum initially rotates at a rotational speed DZ3, which usually also corresponds to the stripping speed of the previous operating cycle. In this exemplary embodiment, the unloaded drum is accelerated from about 50 rpm to about 175 rpm at the beginning of the filling mode. The latter is the filling speed DZ1. The measured actual value UM of the rotational speed of the centrifuge drum 实际 Follows the setpoint value UM with time delay 额定 In particular, it can be clearly seen that the motor current I M , the required electrical power P el and drum torque M T is a significant maximum value, which is due to the energy required to accelerate the unloaded centrifuge drum from the first rotational speed to the second rotational speed. According to the invention, within the range of the first maximum value of operating mode I, the area under the curve trajectory of the electric power can be determined as a function of time with the aid of an integrator. From this (based on the electrical energy used to increase the rotational kinetic energy of the centrifuge drum), the moment of inertia of the centrifuge drum in the unloaded state, i.e. the idling torque, can be derived. Then, the filling valve V is opened and the suspension enters the drum. When filling the drum, the incoming mass flow must be accelerated to its angular velocity, whereby the power consumption of the centrifuge increases significantly during the filling process. Therefore, during Figure 2 In the figure, we can see that the motor current I M The second most significant maximum value is the required electrical power P el and drum torque M TThe integral of the current consumption above the no-load current consumption at this speed is therefore a measure of the energy required to accelerate the incoming mass flow to the angular velocity until the centrifuge is fully filled. The time integral of the incoming mass flow (=mass) is proportional to the integral of the power consumption (=electrical work) of the centrifuge bowl. This energy balance can therefore be used to derive the moment of inertia and, from the moment of inertia, the filled mass (rotating mass) of the now filled bowl.

[0040] At the end of operating mode I (ie filling of the centrifuge drum), the filling valve is closed and the speed is "increased" to the centrifuge speed DZ2. In this exemplary embodiment, a setpoint value U of 1000 rpm is specified for the centrifuge speed. 额定 The "centrifugation mode" can be divided into two phases. In operating mode II, the centrifuge requires a lot of energy to reach the rated speed U 额定 , this is Figure 2 This can be seen from the rising trajectory of the required electrical power. As the liquid of the suspension is centrifuged, the filling material loses mass at the same time. The actual speed UM 实际 Increase linearly until most of the liquid is separated. Once the actual speed UM 实际 Reaching rated speed UM 额定 , no additional energy is needed to rotate the drum, and the motor current I M , electric power P el and drum torque M T The "Centrifugation" operating mode is now ended.

[0041] Finally, in operating mode III, the filling material is centrifugally dried at a constant 1000 rpm. Here, the residual moisture can be determined by slight changes in the rotation speed. As soon as there is no more moisture in the filter cake, the moment of inertia of the drum approaches the lower limit value, and the end of the "centrifugal drying" process can be seen. Details can be found in the Figure 4 Description.

[0042] In this example, after operating mode III (centrifugal drying), a setpoint value UM of 50 ppm is set. 额定 This is the stripping speed DZ3 for stripping the filter cake. In this operating mode IV, the measured actual value U of the rotation speed of the centrifuge drum is 实际 Also follows the setpoint value UM with a time delay 额定 , until the speed finally stays at the starting level of the stripping speed DZ3. After this operating mode, a new cycle of the centrifuge operation begins.

[0043] Figure 3 By way of example, it is shown that in the filling operating mode of the centrifuge drum according to the first embodiment of the invention (see Figure 2 In region I), the centrifuge inflow dm / dt and the required motor current I M The time trajectory of Figure 3 In region I', the centrifuge drum is empty (mass inflow dm / dt = 0). Motor current I M does not change, because the drum is driven at a constant speed against a constant frictional resistance. Figure 2 As described in the description of the invention, the rotational inertia J of the centrifuge drum in the no-load state is obtained according to the speed jump caused by the drum accelerating from the stripping speed to the filling speed. 空载 (J=2*Erot / ω 2 , where Erot = rotational kinetic energy = electrical energy (U*I M *t) and ω = angular velocity). Figure 3 In region I”, the centrifuge drum is filled (dm / dt>0). In order to keep the speed constant, the centrifuge requires additional current to accelerate the incoming mass flow to the corresponding angular velocity of the drum. Figure 3 In the region I "', no further mass is supplied to the drum. The additional energy applied is proportional to the area of ​​the integral of the power consumption over time. This can be derived, for example, in the converter of the drive with the aid of an integrator (see Figure 2 ). According to this embodiment, the method is implemented in a software application, which provides the user with information about the filling degree when the "determine filling degree" function is called, without the need to place a special sensor in the centrifuge bowl.

[0044] Figure 4 The time trajectory of the rotation speed UM of a centrifuge according to another embodiment of the invention is shown. Here, at high rotation speeds RPM (here at DZ2 = 1500 rpm), the drum rotation has slight periodic variations compared to the rotation speed. This can be, for example, a sinusoidal vibration or a sawtooth wave. This occurs in particular in the centrifugal drying area (see Figure 2 The change in angular velocity is measured in operating mode III. When accelerating the drum, the motor must apply energy. This can be deduced from the required current of the motor. When braking the drum, the motor acts like a generator and converts the mechanical energy of the machine back into electrical energy. The converter then has to "dissipate" energy, which can be measured as the voltage drop across the resistor in the converter. Here too, the moment of inertia of the drum can be determined with the aid of an energy balance. If, for example, Figure 4As shown in , the centrifuge is started periodically between two rotational speeds with a defined acceleration energy or braking energy, so that the moment of inertia can be measured regularly. For this purpose, it is necessary to query the converter power or the electricity meter periodically. In order to achieve this, the query must be implemented in the facility control system. A small change of, for example, + / -50rpm compared to the rotation speed of 1500rpm has no effect on the separation process. Due to the additional weight of several tens of kilograms of solids precipitated in the suspension and at several thousand revolutions, the acceleration energy of the rising ramp waveform or the braking torque of the falling ramp waveform can be used to derive the moment of inertia in the drying process. According to the present invention, it is necessary to use energy for acceleration that is easy to measure or controlled braking energy, and record the time change of the angular velocity dω / dt. Figure 4 The sawtooth curve shown in can be obtained by accelerating or braking the drum with a constant force and using the change in angular velocity to calculate the moment of inertia, or by specifying the change in angular velocity as a function of time and deriving the power required for this. Figure 4 In the embodiment shown in , two cycles or variations of the rotational speed at different times are shown. The comparison of the rotating mass (inertial mass) obtained in each cycle can be used to determine the residual moisture of the filter cake. If there is still residual moisture, the rotating mass will decrease over time. Ultimately, the residual moisture approaches a limit value over time, whereupon the centrifugal separation process (if necessary earlier than the original setting) ends and the filter cake can be mechanically removed after reaching the stripping speed (DZ3). In pharmaceutical applications and in the fine chemical industry, the dehumidified solid is a valuable product (to be further processed), while the separated liquid is waste. The goal is to keep the residual moisture as low as required and the residual moisture should therefore be monitored.

[0045] Preferably, the invention and the described improvements are implemented in software and in firmware or in a microchip, for example by using a dedicated circuit, or in a combination of software and hardware, for example in a software module that can be read into a converter control system.

Claims

1. A method for monitoring a centrifuge (Z) for solid-liquid separation of suspensions (SUS), the centrifuge having a centrifuge drum (T) which is connected to at least one frequency-controlled drive for generating a rotation of the centrifuge drum (T), in, During operation of the centrifuge, in the course of the separation process, a plurality of variables and parameters of the drive are determined in a time-dependent manner. The invention is characterized in that the operating mode (I, II, III, IV) of the centrifuge operation cycle is derived from the mutual relationship between the variables and parameters of the drive and the information about the separation process is automatically obtained according to the derived operating mode.

2. The method according to claim 1, It is characterized in that In order to derive the filling mode (I), the rotational speed (DZ3, DZ1) of the drum rotation and the energy of the drive (FU) required at least to maintain the rotational speed (DZ1) of the drum rotation are recorded as a function of time, and the increase in the rotational inertia of the drum caused by the filling is derived therefrom, and the filled rotational mass of the centrifuge drum (T) and the mass contained in the centrifuge drum are determined therefrom.

3. The method according to claim 1, It is characterized in that The recorded interrelationships of the variables and parameters of the drive result in the operating mode "centrifugal drying" (III), and at a high rotation speed (DZ2), the rotation speed of the drum is periodically varied over time and the temporal variation of the angular velocity is measured, The energy for accelerating and braking the drum is derived therefrom and the moment of inertia of the drum is calculated and the rotating mass and therefore the filling degree of the centrifuge drum is determined taking into account the idling moment of the drum.

4. The method according to claim 3, It is characterized in that At the high rotational speed (DZ2), the residual moisture content of the filter cake is determined by comparing the rotational masses of at least two cycles of the rotational speed change, which residual moisture content is constant in the case of complete dehumidification.

5. The method according to any one of the preceding claims, It is characterized in that In the case of a frequency-dependent converter, the energy required to maintain or change the rotation of the centrifuge drum is determined with the aid of an integrator.

6. A device (VO) for monitoring a centrifuge (Z) for solid-liquid separation of a suspension (SUS), the centrifuge having a centrifuge drum (T) which is connected to at least one frequency-controlled drive (FU) for generating a rotation of the centrifuge drum (T), - having at least one interface (S1, S2, S3) for receiving a signal from said frequency-controlled drive, and - an evaluation unit (AS) having a data memory (Sp) which is designed to store signals received by the interface (S1, S2, S3), wherein: The evaluation unit (AS) is designed to carry out a method according to any one of claims 1 to 5 .

7. The device according to claim 6, wherein: The evaluation unit (AS) and the data memory (SP) are implemented in a cloud-based environment.

8. A computer program product, comprising instructions which, when the program is executed by a computer, cause the computer to implement the method according to any one of claims 1 to 5.

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