Method and apparatus for operating a comminution device with a rotor having a large moment of inertia, in particular a chipper, shredder, refiner, crusher or mill

Abstract

Method for operating a comminution device with a rotor (1) having a large moment of inertia, in particular a chipper, shredder, refiner, crusher or mill, wherein the comminution device - includes an electric primary drive (12) for driving the rotor (1) during the comminution operation and - an electric secondary drive (15) for accelerating and / or decelerating the rotor (1) outside of the comminution operation, as well as - a power converter (16) for supplying the secondary drive (15) with electrical energy, - a rotary encoder (20) for detecting the rotation of the rotor or secondary drive (15), - an evaluation unit (19) for recording and evaluating the signals from the rotary encoder (20), - a first controller (21) and a second controller (22) for outputting a manipulated variable to the power converter (16), and - a data processing and control unit (17), wherein a) the primary drive (12) is de-energized or the data processing and control unit (17) de-energizes the primary drive (12), b) the data processing and control unit (17) outputs a signal about the target speed to the first controller (21), c) the rotary encoder (20) detects the number of pulses generated by the rotation of the secondary drive (15) and outputs it as a signal to an evaluation unit (19), d) the first controller (21) in a first control loop extracts the actual rotational speed from the signals of the evaluation unit (19), compares the actual rotational speed with the target rotational speed and determines a manipulated variable from the comparison, e) the first controller (21) outputs the manipulated variable to the converter (16), and f) the process steps c) to e) are repeated until the target rotational speed is reached, and wherein the rotor (1) is positioned g) upon reaching the first knife change position, a reference signal is generated and output to the data processing and control unit (17), h) the data processing and control unit (17) outputs a signal about the target position of the rotor (1) for the next knife change position to the second controller (22), i) the evaluation unit (19) determines the actual position of the rotor (1) from the number of signals from the rotary encoder (20) after generating the reference signal and outputs it to the second controller (22), j) the second controller (22) in a second control loop compares the actual position with the target position, determines a manipulated variable from the comparison and outputs the manipulated variable to the converter (16), wherein k) the process steps i) to j) are repeated until the target position is reached, and wherein I) the first control loop and second control loop form a cascade control system.

Description

[0001] The invention relates to a method for operating a comminution device with a rotor having a large moment of inertia according to the preamble of claim 1 and to a device for carrying out the method according to the preamble of claim 5.

[0002] In the field of mechanical process engineering, comminution devices with a comminution rotor equipped with comminution tools are widely used. These include, for example, chippers, shredders, refiners, crushers, hammer mills, and eddy current mills. Due to the properties of the feed material and the type of comminution, the rotors of these devices are extremely robust. As a result, suitable rotors typically have a weight of several tons and thus a very high moment of inertia. During comminution, these rotors operate at speeds of up to 400 rpm. -1and more, for which electric motors with a power output of 3,000 kW and more are used.

[0003] The very high moment of inertia of the rotor necessitates special precautions, especially when starting the rotor up to the operating speed and when adjusting the rotor for changing the shredding tools, since electric motors with 3,000 kW and more cause a very high current consumption during the start-up and acceleration phase of the rotor, which in the worst case leads to an overload of the power grid.

[0004] To prevent this, known devices are equipped with two drives: a primary drive for the shredding operation and a secondary drive for accelerating and adjusting the rotor. German patent DE 10 2015 005 859 A1 describes a disc chipper whose secondary drive is a hydraulic motor that accelerates the rotor to the predetermined speed. Such drives have proven effective in practice, but they have the disadvantage that the kinetic energy inherent in the rotating rotor is converted into heat when the rotor stops and is thus lost. This waste heat also leads to an undesirable warming of the hydraulic oil in the secondary drive, altering its viscosity and therefore its characteristics.

[0005] Furthermore, a drum chipper with a shredding rotor is known from DE 10 2008 061 734 A1. The rotor is driven during shredding by an electric motor, which is coupled to the rotor via a gearbox. For accelerating, decelerating, and stopping the rotor, the drum chipper has an additional motor, which, like the drive, is controlled by a microcontroller based on data acquired by a sensor device.

[0006] Against this background, the invention aims to further develop and improve known methods for operating comminution devices and corresponding devices.

[0007] This problem is solved by a method having the features of claim 1 and a device having the features of claim 5.

[0008] Advantageous further training opportunities arise from the sub-requirements.

[0009] The present invention is aimed in particular at comminution devices whose rotor is characterized by its large moment of inertia. A large moment of inertia within the meaning of the invention exists when the moment of inertia of the rotor is at least 5,000 kg*m². 2 is, preferably at least 10,000 kg*m³ 2 . Comminution devices with such a rotor include, for example, refiners, crushers, mills, and chippers, whereby rotors of disc chippers, in particular, can have a moment of inertia of over 20,000 kg*m at a corresponding diameter. 2 The invention further assumes that rotors with a large moment of inertia cannot be easily accelerated from a standstill by the primary drive, as the resulting high current peaks would threaten to overload the power supply.

[0010] Based on this, the invention is founded on the idea of ​​providing an electric drive as a secondary drive, wherein the rotor is accelerated to its rated speed by a control system for the secondary drive according to the invention, and subsequently the primary drive alone takes over the driving of the rotor. In this way, each drive can be designed for the specific requirements of its application and thus operated within its optimal performance range. For example, the power of the primary drive can be in a range of 200 kW to 3,000 kW, and the power of the secondary drive in a range of 11 kW to 200 kW.

[0011] Compared to hydraulic secondary drives, the primary advantage is that components for a hydraulic system, such as oil reservoirs, pumps, electric motors, filters, hoses, pressure relief valves, control valves, fittings, and the like, are not required, thus eliminating the associated costs. Furthermore, the secondary drive can draw its electrical power from the primary drive, resulting in a significant reduction in investment for the drive system due to the synergistic effects.

[0012] Another advantage over hydraulic secondary drives becomes apparent when braking the rotor, where the kinetic energy inherent in the rotor has previously been converted into waste heat, with the effects already described. An electric secondary drive avoids this problem, as the operating temperature has no influence on its operation.

[0013] Preferably, the electric secondary drive is used as a generator to produce electrical energy when the rotor is decelerating. This energy is then fed into the power grid via the frequency converter. In this way, the secondary drive acts as a brake, reducing the time it takes for the rotor to come to a complete stop. A portion of the released energy can thus be recovered and used in other areas of the system.

[0014] According to the invention, the first controller for regulating the speed and the second controller for positioning the rotor form a cascade control system, with the associated control loops nested within each other. This allows for increased control accuracy.

[0015] Furthermore, in advantageous embodiments of the invention, the absorption of electrical energy during the acceleration phase and / or the output of electrical energy during the braking phase of the rotor is limited in order to prevent overloading of the system. For example, for this purpose, the input of electrical energy during recuperation operation can follow a linear deceleration ramp.

[0016] Furthermore, the arrangement of a gearbox between the primary drive and the rotor proves advantageous in order to be able to operate the rotor at the optimal speed for the application, regardless of the speed of the primary drive.

[0017] The invention is explained in more detail below with reference to an embodiment shown in the drawing, which demonstrates the implementation of the invention on a disc chopper, without, however, limiting the invention to that.

[0018] The single figure shows a schematic top view of the essential plant components of a disc chipper as well as the components and dependencies necessary for control and regulation.

[0019] A chipping disc 1, housed in a casing (not shown), is shown. Its central through-hole is fixed to a drive shaft 2 and it is rotatably mounted in bearings 3. The front of the chipping disc 1 is designated with reference numeral 4, and the rear with reference numeral 5. Chipping knives (not shown), extending approximately radially in the plane of the disc, are arranged on the front 4. The material to be fed, for example, logs, is fed to these knives at an oblique angle to the plane of the disc. For example, up to 20 or more chipping knives can be arranged on the chipping disc 1 at uniform circumferential distances from one another. During the chipping process, the material passes through the chipping disc 1, and the chipped material is discharged from the rear 5.

[0020] The chopping disc 1 can have a diameter of 4 m or more and, due to its large weight, a moment of inertia of 24,000 kg*m. 2and more. During operation, the chopping disc 1 rotates, for example, at a predetermined speed of between 200 min⁻¹. - 1 and 300 min -1 The chopping disc 1 with chopping knives and drive shaft 2 essentially forms the rotor.

[0021] In the shredding process, the shredding blades are subject to natural wear, which affects the quality of the final product. To ensure consistently high quality, the shredding blades must therefore be changed at predetermined intervals. For this purpose, the shredding disc 1 is moved into a suitable blade-changing position, locked in place, and then moved to the next blade-changing position to replace the next blade. This process is repeated until all worn shredding blades have been replaced.

[0022] To fix the chopping disc 1 in a knife change position, the disc chopper has a locking device 6 fixed to the chopping disc 1 with a bracket 7 and an axially adjustable locking bolt 8, which can be engaged with bores in a predetermined position on the rear 5 of the chopping disc 1.

[0023] The chopping disc 1 is connected via a coupling 9 to a gearbox 10, the gearbox input of which is connected via a further coupling 11 to a primary drive 12 in the form of a three-phase motor. The power of the primary drive 12 can be 200 kW, preferably 500 kW, or more. In the present embodiment, the primary drive has a power of 3,000 kW and is supplied directly or via a frequency converter (not shown) from the power supply network 13.

[0024] A secondary drive 15, which can also be a three-phase motor, acts on the shaft of the primary drive 12 via a further coupling 14. The drive shafts of the primary drive 12 and the secondary drive 15 are coaxial and connected to each other via the coupling 14. The secondary drive 15 is supplied with electrical energy via a power converter 16, in this case a frequency converter, which in turn is supplied from the power supply network 13. The power of the secondary drive 15 is preferably in the range between 11 kW and 200 kW and is 200 kW in the present embodiment.

[0025] The operation of a comminution device according to the invention comprises several operating modes, which in particular include starting the device from standstill into comminution operation or braking the device from comminution operation to standstill, for example in the course of carrying out maintenance and repair work, as well as adjusting the rotor to the individual knife change positions when replacing the chopping knives.

[0026] According to the invention, a suitable system for controlling and regulating the device comprises a higher-level microprocessor-controlled data processing and control unit 17, as well as sensors for detecting the current state of the device, which are connected to the data processing and control unit 17. The sensors include, in particular, a reference point sensor 18, past which a reference mark is passed when the chopping disc 1 rotates. This reference mark is registered by the reference point sensor 18, whereupon a reference signal is output to the data processing and control unit 17. The absolute rotational position of the chopping disc 1 can then be determined from the known arrangement of the reference mark relative to the chopping disc 1. Preferably, the reference mark is attached to the rotating part of the device such that the chopping disc 1 is in one of the possible blade-changing positions when the reference mark is registered by the reference point sensor 18.

[0027] Furthermore, the system for controlling and regulating the device includes a microprocessor-controlled evaluation unit 19, to which another sensor for controlling and regulating the device is connected. This additional sensor, in the form of a rotary encoder 20, continuously detects the rotational movement of the chopping disc 1 and outputs a signal about the rotational movement to the evaluation unit 19. For this purpose, the rotational movement of the chopping disc 1 through 360° can be divided into a multitude of increments, with the rotary encoder 20 registering each increment as a pulse and outputting a corresponding signal to the evaluation unit 19. The evaluation of the data from the rotary encoder 20 in the evaluation unit 19 includes, among other things, determining the degree of rotational movement by summing the number of pulses or increments.The rotational speed can be deduced from the time interval between two pulses; the absolute current position of the rotor can be determined from the number of pulses after the rotor has assumed a known position.

[0028] Furthermore, the system for controlling and regulating the device comprises a first controller 21 and a second controller 22, which, depending on the selected operating mode and the current state of the device, each output a signal to the converter 16 for controlling the secondary drive 15. The first controller 21 represents a first control loop for regulating the rotational speed of the rotor, and the second controller 22 represents a second control loop for regulating the absolute rotational position of the rotor.

[0029] The starting up of a comminution device according to the invention into the "comminution operation" mode is carried out from a state in which the primary drive 12 is de-energized. The operator switches the device into comminution operation, whereupon the data processing and control unit 17 outputs a signal with the target speed of the primary drive 12 or secondary drive 15 to the first controller 21, for example 2000 min⁻¹. -1 , which, taking into account the reduction by the reduction gear 10, results in a rotational speed of the chopping disc 1 of, for example, 400 min -1 corresponds.

[0030] Simultaneously, the rotary encoder 20 sends a signal to the evaluation unit 10 as soon as it registers a pulse. Since the chopping disc 1 is initially stationary, the evaluation unit 19 receives zero pulses. The evaluation unit 10 then calculates the actual rotational speed of the chopping disc 1 from the number of pulses per unit of time and outputs this as a signal to the first controller 21.

[0031] In the first controller 21, the actual rotational speed is compared with the target rotational speed, and if a deviation is detected, a manipulated variable is calculated and output as a signal to the frequency converter 16. Based on this manipulated variable, the frequency converter 16 increases the electrical power supply if an acceleration of the rotor and thus an increase in the rotational speed of the secondary drive 15 is desired, or decreases the electrical power supply to reduce the rotational speed.

[0032] By iterating these steps, the electrical power for the secondary drive 15 is increased or decreased until the target rotational speed of the chipping disc 1 or the primary drive 12 is reached. The evaluation unit 19 reports this event to the data processing and control unit 17, which then switches off the frequency converter 16 and thus the secondary drive 15, and switches on the primary drive 12. In this embodiment, the primary drive 12 is supplied with electrical energy directly from the mains 13 and subsequently drives the chipping disc 1 alone during the shredding process.

[0033] If the shredding device needs to be brought from shredding operation to a standstill, for example for maintenance and repair work or to change the blades, the operator switches the device to the "Stop" operating mode. The data processing and control unit 17 then interrupts the supply of electrical energy to the primary drive 12 and subsequently switches the frequency converter 16 to recuperation mode. In recuperation mode, the secondary drive 15 is driven by the still-rotating shaft of the primary drive 12, with its components acting as a generator. The electrical energy generated in this process is then fed back into the power supply network 13 via the frequency converter 16.

[0034] To avoid overloading the system during recuperation, the generated electrical energy can be limited, for example by specifying a target curve, such as a deceleration ramp.

[0035] To perform a blade change, the operator switches the stationary shredding device to "blade change" mode. In this mode, the rotor, and thus the shredding disc 1, is moved from one blade change position to the next at the operator's initiative.

[0036] Analogous to starting up the device in the comminution operation, the rotor is accelerated by the secondary drive 15 to a speed suitable for adjusting the rotor.

[0037] This is done by specifying a target speed from the data processing and control unit 17 to the first controller 21 and regulating the supply of electrical energy by the controller 21 and the frequency converter 16 as already described until the actual speed corresponds to the target speed.

[0038] At the same time, the data processing and control unit 17 outputs a setpoint value to the second controller 22 for the number of pulses to be generated by the rotor in the rotary pulse generator 20 after receiving the reference signal from the reference point sensor 18 in order to assume the next knife change position.

[0039] During the slow rotation of the rotor in adjustment mode, the reference mark located on the rotor is moved past the reference point transmitter 18, whereupon this outputs a reference signal to the data processing and control unit 17, which is then forwarded to the evaluation unit 19.

[0040] Triggered by this event, the evaluation unit 19 begins counting the pulses received from the rotary encoder 20 after receiving the reference signal, with the sum being continuously output as the actual value to the second controller 22. In the second controller 22, the actual value is compared with the stored setpoint value in a second control loop. If the actual value and setpoint value match, the controller 22 outputs a signal to the frequency converter 16, which interrupts the supply of electrical energy to the secondary drive 15. Since the drive for the rotor is now deactivated, the rotor comes to a standstill in the next blade-changing position and is locked in this position by means of the locking device 6. After the chipper blades have been replaced, the locking device 6 releases the locking mechanism, and the operator initiates a further adjustment of the rotor as described.

Claims

[1] Method for operating a comminution device with a rotor (1) having a large moment of inertia, in particular a hacker, shredder, refiner, crusher or mill, wherein the comminution device - includes an electric primary drive (12) for driving the rotor (1) during the comminution operation and - an electric secondary drive (15) for accelerating and / or decelerating the rotor (1) outside of the comminution operation, as well as - a power converter (16) for supplying the secondary drive (15) with electrical energy, - a rotary encoder (20) for detecting the rotation of the rotor or secondary drive (15), - an evaluation unit (19) for recording and evaluating the signals from the rotary encoder (20), - a first controller (21) and a second controller (22) for outputting a manipulated variable to the power converter (16), and - a data processing and control unit (17), wherein a) the primary drive (12) is de-energized or the data processing and control unit (17) de-energizes the primary drive (12), b) the data processing and control unit (17) outputs a signal about the target speed to the first controller (21), c) the rotary encoder (20) detects the number of pulses generated by the rotation of the secondary drive (15) and outputs it as a signal to an evaluation unit (19), d) the first controller (21) in a first control loop extracts the actual rotational speed from the signals of the evaluation unit (19), compares the actual rotational speed with the target rotational speed and determines a manipulated variable from the comparison, e) the first controller (21) outputs the manipulated variable to the converter (16), and f) the process steps c) to e) are repeated until the target rotational speed is reached, and wherein the rotor (1) is positioned g) upon reaching the first knife change position, a reference signal is generated and output to the data processing and control unit (17), h) the data processing and control unit (17) outputs a signal about the target position of the rotor (1) for the next knife change position to the second controller (22), i) the evaluation unit (19) determines the actual position of the rotor (1) from the number of signals from the rotary encoder (20) after generating the reference signal and outputs it to the second controller (22), j) the second controller (22) in a second control loop compares the actual position with the target position, determines a manipulated variable from the comparison and outputs the manipulated variable to the converter (16), wherein k) the process steps i) to j) are repeated until the target position is reached, and wherein I) the first control loop and second control loop form a cascade control system. [2] Method according to claim 1, characterized by , that the data processing and control unit (17) switches off the secondary drive (15) after reaching the target speed and the data processing and control unit (17) supplies the primary drive (12) with electrical energy. [3] Method according to claim 2, characterized by , that to slow down the rotor (1) the data processing and control unit (17) switches off the primary drive (12) and The data processing and control unit (17) initiates the recuperation operation by using the secondary drive (15) as a generator and the power converter (16) feeds the generated electrical energy into the supply network (13). [4] Method according to claim 3, characterized by that the electrical energy fed into the supply network follows a linear deceleration ramp. [5] Comminution device for carrying out a method according to one of claims 1 to 4 comprising a rotor (1) equipped with comminution tools, an electric primary drive (12) for driving the rotor (1) during comminution operation, and a secondary drive (15) for accelerating and / or decelerating the rotor (1) outside of comminution operation, wherein the secondary drive (15) is formed by an electric motor, characterized by , that the device comprises a first controller (21) with which the rotational speed of the rotor (1) can be controlled in a first control loop, and a second controller (22) with which the absolute rotational position of the rotor (1) can be controlled in a second control loop, and the first control loop and the second control loop form a cascade control system. [6] Comminution device according to claim 5, characterized by , that the secondary drive (15) has an electrical power output between 11 KW and 200 KW. [7] Comminution device according to claim 5 or 6, characterized by , that the primary drive (12) has an electrical power output between 200 KW and 3,000 KW. [8] Comminution device according to any one of claims 5 to 7, characterized by , that the moment of inertia of the rotor (1) is at least 5,000 kg*m 2 amounts. [9] Comminution device according to any one of claims 5 to 8, characterized by , that a reference point sensor (18) is arranged in the drive train of the rotor (1). [10] Comminution device according to any one of claims 5 to 9, characterized by , that a gearbox (10) is interposed between the primary drive (12) and the rotor (1). [11] Comminution device according to any one of claims 5 to 10, characterized by, that the gearbox (10) has a reduction ratio between 1 : 1 and 1 :

5. [12] Comminution device according to any one of claims 5 to 11, characterized by a stationary locking device (6) with which the rotor (1) can be fixed in a blade-changing position.

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