CN115734822A

CN115734822A - Method for adjusting the damping of the movement of a press roller of a high-pressure roller press and corresponding high-pressure roller press

Info

Publication number: CN115734822A
Application number: CN202180042823.9A
Authority: CN
Inventors: 尼科·哈森伯格
Original assignee: KHD Humboldt Wedag AG
Current assignee: KHD Humboldt Wedag AG
Priority date: 2020-04-17
Filing date: 2021-03-25
Publication date: 2023-03-03
Also published as: EP4135900A1; DE102020110468A1; WO2021209236A1

Abstract

The invention relates to a method for adjusting the damping of the movement of a floating roll (3) of a high-pressure roller press (1), wherein the high-pressure roller press (1) has a hydraulic system (8) which presses the floating roll (3) against a fixed roll (2) and thereby maintains a predetermined roll gap pressure in the roll gap (7) between the floating roll (3) and the fixed roll (2) when rolling stock passes through the roll gap (7) between the floating roll (3) and the fixed roll (2), characterized in that an adaptive damping adjustment is used which monitors the damping of the mechanical oscillation movement of the floating roll. The invention further relates to a high-pressure roller press with such an adaptive damping control.

Description

Method for adjusting the damping of the movement of a press roll of a high-pressure roller press and corresponding high-pressure roller press

Technical Field

The invention relates to a method for adjusting the damping of the movement of a floating roll of a high-pressure roller press, wherein the high-pressure roller press has a hydraulic system which presses the floating roll against a fixed roll and thereby maintains a predetermined roll gap pressure in the roll gap between the floating roll and the fixed roll when the rolling stock passes through the roll gap between the floating roll and the fixed roll. The invention further relates to a high-pressure roller press having such a control.

Background

For reducing or compacting the granulate, high-pressure roller presses are usually used which are composed of two oppositely running, generally equally large, rotatably mounted rollers which run around at the same peripheral speed and between which a narrow roller gap is formed. The material to be crushed or compacted is led through the roll gap, wherein the material is crushed or compacted under high pressure in the roll gap. The result of this treatment, i.e. the result of the comminution or compacting, is, for the most part, dependent on the material properties of the material to be comminuted. The reduction in the roll gap described here is first achieved by

Et al are described in german laid-open patent publication DE2708053A1 as high-pressure comminution and since then it has been referred to as a type of comminution other than shear milling and crushing.

High-pressure roller presses are in principle different from other presses for comminution. In particular, high-pressure roller presses for comminuting stones cannot be compared with roller presses for comminuting grain. The grain is ground in grain rollers. The cereal roll has a weight range of up to 100kg. The entire device design of the grain roller is very different from that of a high-pressure roller press. The grain roller is also operated in a sheared state. In contrast, high-pressure roller presses do not operate in a sheared state.

High-pressure roller presses are likewise very different from band rollers for rolling steel. The steel strip roll stands out because of its quiet and smooth operation. The steel between the belt rollers is either very stretchable because the steel to be rolled is hot deformed or can be cold deformed. After that, quiet and smooth running of the steel roll is very obvious due to the nature of the rolling process. It is thus possible to operate the belt rollers with two parallel rollers arranged one above the other, wherein the roller gap pressure can be generated by the roller's own weight and also by hydraulic auxiliary means. The problem of vibrations due to the stretchability of the steel to be rolled is not expected. Depending on the steel to be rolled, the strip rolls can reach roll gap speeds of up to 200 km/h. Although the forces acting in the steel belt rollers are many orders of magnitude greater, the steel belt rollers can completely resemble a dough roller that rolls over and spreads the pizza dough. High pressure roller presses for crushing ores and rocks achieve roller gap speeds in the low two digit km/h range at most. By means of the high circumferential speed, the band roller is operated at a rotational frequency and in a desired manner largely deviating from the natural frequency of its own structure. High-pressure roller presses operating at much lower speeds cannot achieve the desired state of the own frequency, which is far from the roller speed.

The invention relates to a high-pressure roller press for comminuting brittle ground material such as rock and ore, wherein the brittleness of the ground material is a mandatory prerequisite for the application of the grinding method to the respective ground material. The strip rolls for steel work at operating limits different from high-pressure roller presses, i.e. with steel that deforms under the rolls, does not spontaneously crumble due to brittleness, and therefore has good extensibility avoiding the pressure in the roll gap. In high-pressure roller presses, the rollers are arranged horizontally next to one another and form a roller gap in which the material to be ground passes vertically. The high pressure roller press has a roll gap pressure of 50MPa or greater. By means of the horizontal support of the rolls and by means of the operation of the brittle material, the overall mechanical behavior of the high-pressure roller press cannot be compared with the mechanical behavior of vertically stacked belt rolls, which in addition run damped and uniformly due to the stretchability of the steel to be rolled. In high-pressure roller presses, the ground material, which is not always the same in shape, passes through the roller gap, and the high-pressure roller presses tend to vibrate due to the high pressure generated by the hydraulic press moving the rollers in the horizontal direction. The vibrations may be caused by very small variations in the properties of the mill. It may happen in this way that the dry brittle grinding material entrains air into the roll gap during the comminution. When there is a part of the already intensively comminuted material in the roll gap which is no longer tolerable to ignore, the air enclosed in the mill batch can likewise spontaneously escape during compaction of the mill batch and before the mill batch spontaneously crumbles due to brittle fracture and thereby yield to the roll gap pressure. Thereby, the oscillation behavior of the high-pressure roller press can be influenced by the non-linear forces, which are not explained with reference to the conventional analysis of damped oscillations. The natural frequency of the high-pressure roller press is in the range of the external excitation frequency in an undesirable manner, such as sudden failure in the event of a brittle fracture, such as spontaneous leakage of air from the highly compacted material, such as the autorotation of the grinding rollers and the feeding by means of an elevator.

For the ideal, energy-saving and low-wear comminution in high-pressure comminution, a large number of parameters of the high-pressure roller press used, in addition to the pressure in the roller gap, are important. For example, it is important that the rollers of the high-pressure roller press used rotate without relative slip, so that the rollers do not grind by the shearing movement of the mill material, but merely squeeze. It has furthermore been found that the correct supply of fresh material into the roll gap of the high-pressure roller press used per time unit also plays an important role in the desired function of the high-pressure roller press used. If a small amount of fresh material is fed to the roll gap per time unit, the high-pressure roller press operates as a crusher, which operates in particular when using rolls designed with hard protective bodies, wherein the granular material to be crushed, which is the fresh material, is crushed by means of a point load. This type of comminution is less energy efficient than high pressure comminution and it does not lead to the desired refined product. In contrast, if too much granulate is fed into the roll gap as new material per time unit, the roller compacted material consisting of new material and recycled material is pressed too strongly in the roll gap, enclosed air can no longer escape and the roll gap of the high-pressure roller press used tends to clog properly. In this case, the rollers mounted in a manner that allows them to move back, the excess fresh material falls through the roller gap in an uncrushed state, and the high-pressure roller press then operates again in the previous state until it has to move back again in order to allow the excess fresh material to pass through the roller gap. The roller press thus enters into a first type of oscillating movement, in addition to the other oscillating movements, and it begins to vibrate mechanically.

In addition to mechanical oscillations of this type, which occur as a result of the rollers moving forward and back again in their yielding bearing at a higher frequency than the material already moving, there is a further oscillatory movement in the high-pressure roller press in the form of an oscillatory movement of the rollers, which is produced by the repeated braking action of the overfilled roller gap on the rotating rollers. Due to this rhythmic braking of the overfilled roll gap and the renewed acceleration of the drive, the rolls enter into a rotational oscillation, wherein the torque and the angular velocity of the rolls fluctuate uniformly and regularly. This is particularly the case when the rolls are driven, in which case the high-pressure roller press has only one driven roll together with one running roll.

A particular type of oscillatory motion can be produced if the overload caused by too much fresh material occurs only in a part of the roll gap. The rollers can then perform a combined oscillation, which is formed by a forward and return movement of the rollers in a horizontal direction perpendicular to the direction of extension of the roller gap and a rotational oscillation. Here, the rollers can likewise undergo a slight, oscillating change in position in which they are rotated by a very small angular value about a vertical axis. In this movement, the roller does not move uniformly with the two bearing bodies carrying it, but the two bearing bodies alternately change their position relative to one end of the roller in each case.

Mechanical oscillatory movements and amplitudes in the form of impacts of short duration and high frequency also occur when excessively large agglomerates of new material pass through, or when components such as metal blocks, hammer heads undesirably in the new material, large steel rivets or steel bolts, excavator teeth or other undesirable metal blocks which cannot be fragmented by high-pressure treatment in the roll gap, which undesirably enter the new material when the raw material is mined, pass through.

Furthermore, if the ground material is not yet in equilibrium in the circuit or the circuit material has a composition which is not yet in equilibrium, a mechanical oscillating movement in the high-pressure roller press can likewise occur during the start-up of the high-pressure roller press. Finally, a mechanical oscillating movement also occurs when a relatively wet and fine-grained new material is introduced.

If the aforementioned frequency of the mechanical oscillation movement happens to reach the frequency of the self-oscillation of the high-pressure roller press, more energy is conducted with each individual oscillation movement to the entire system of the high-pressure roller press, whereby damage to the bearings, the roller surfaces and other components of the high-pressure roller press as a whole can occur, so that there is also the reason that each roller has a self-weight above 50t, while larger rollers can even have a weight of 100t, an oscillating mass of this order of magnitude also posing a very great challenge to a very robust machine frame.

Of course, the configuration of the high-pressure roller press determines that the entire system of the high-pressure roller press is mechanically damped. The damping is provided on the one hand by a hydraulic system in which the hydraulic fluid flows to and fro at a greater speed through a line which is finer than the diameter of the hydraulic strut or through a line which is finer than the diameter of the hydraulic cylinder. In flow through the conduit at high speed, the viscosity of the hydraulic fluid causes a stronger and more likely linear damping. Linear damping can be illustrated by the conventional description of damping vibrations. Furthermore, the movement of the bearing body on the running rail of the dancer consumes a large amount of mechanical energy, also in the form of friction, whereby the oscillating movement is damped. However, the movement of the bearing block is already accompanied less by linear damping, since the transition from static friction (no movement under slight surface deformations in the elastic region) to sliding friction occurs very abruptly. Sliding friction also appears non-linear. The resistance in sliding friction decreases with speed. By means of the relatively large number of possible oscillations, i.e. bending oscillations, torsional oscillations, oscillation damping, which is accompanied by static/sliding friction, oscillations which are damped due to the viscosity of the hydraulic fluid, and the relatively large number of external oscillation excitation factors, a very large number of different self-oscillations, i.e. different resonance frequencies, can be observed in the high-pressure roller press. The higher external oscillation excitation factor is, for example, the periodic feeding of the mill batch through the elevator. The oscillating movement can also be induced by the operating rotational speed during the bearing impact or during the vertical impact movement of the roller.

If the high-pressure roller press falls into an undesired oscillation mode, the high-pressure roller press no longer operates with high energy efficiency and, in addition, is also subjected to mechanically high loads.

In order to avoid or even prevent mechanical oscillating movements in the high-pressure roller press due to overloading of the roller gap with fresh material, the amount of fresh material fed per time unit can be adjusted, for example, in such a way that, when an undesired oscillating movement in the high-pressure roller press is detected, less fresh material is fed into the roller gap per time unit by the feeding device. However, this has the disadvantage that a relatively long return time from the controlled feed device to the detected regulating section of the oscillating movement has to be accepted. Waiting until the changed new feed to the roll gap has effected and the oscillating movement is thereby finally reduced, takes a certain time. At that point, considerable damage to the high-pressure roller press may have already occurred, or it may build up as more frequent adjustment activities are required.

In order to monitor the function of the fragmentation device, the following measures are known from the prior art:

document US2010/0102152A1 describes a cone crusher which is equipped with a proximity sensor, for example an ultrasonic sensor or a laser sensor. By measuring the outlet gap width, the width of the gap can be adapted to the process conditions by lifting or lowering the cone, thereby avoiding uneven rotation which can damage the cone.

US2004/0255679A1 describes a drum mill for comminuting minerals, which has an acoustic sensor in the drum, by means of which an excessive overload of the drum, for example caused by rock-like rocks, can be detected.

DE10132067A1 discloses a method for monitoring dangerous operating states, such as slip, in a roll stand at the acoustic level. For this purpose, the noise or sound level occurring at the roll stand is detected by means of microphones and the frequency spectrum is evaluated analytically.

DE102011018705A1 discloses a method for adjusting the roll gap pressure in relation to the observed vibrations of a high-pressure roller press. The pressure in the hydraulic system varies depending on the operating state, so that the high-pressure roller press can always be operated close to the maximum pressure.

German document DE4414366A1 likewise teaches to reduce the hydraulic pressure when the measured oscillation amplitude exceeds a preset value for a certain time and, conversely, to increase the pressure when the preset oscillation amplitude is no longer exceeded.

German patent DE19647483B4 discloses a high-pressure roller press which has a variable gas-bag accumulator in its hydraulic system, which blocks pressure peaks in the hydraulic system. Pressure peaks occur when material that cannot be fragmented by brittle fracture passes, in which case the heavy roller press forces the rollers to perform a sudden and very rapid deviating movement with the roller gap open when the material passes. When the gas volume of the airbag accumulator changes, the spring constant of the damper system changes, and when the volume in the hydraulic system changes, the pressure rises as a result.

By changing the gas volume in the gas-bag accumulator, the stiffness of the spring system changes.

German laid-open patent application DE102007059072A1 provides teaching on a high-pressure roller press with two dancers. In this high-pressure roller press, the roller gap pressure is likewise maintained by means of a hydraulic system, which acts on the position of the rollers. The teaching also provided at the given location is that it is necessary to keep the flexible lines of the hydraulic system short in order to keep the viscosity-dependent resistance of the pressure medium as low as possible when flowing through the lines. Since the roll gap position must be monitored in the case of two dancers, it is necessary to operate the entire system with as little damping as possible in order to be able to adjust the roll gap position quickly.

No document discloses how these undesirable operating states, which accompany the roller oscillations, are avoided or eliminated as early as in the initial phase or in the forming state.

Disclosure of Invention

It is therefore desirable to be able to monitor the high-pressure roller press so that no mechanical oscillating movements occur. The object of the invention is therefore to operate a high-pressure roller press of this type such that no mechanical oscillation movement occurs.

According to the invention, the object is achieved by the feature that the high-pressure roller press has an adaptive damping in the hydraulic system. Specific methods of adaptive damping are given in claims 2 to 7. The high-pressure roller press has an adaptive damping and consists of a throttle in the hydraulic system and a corresponding regulating device, which are specified in the dependent claims 8 to 13.

The special point of the adjustment is that the high-pressure roller press can be operated despite the oscillation adjustment with constant hydraulic pressure. This protects the hydraulic pump from continuous load changes and allows the high-pressure roller press to operate longer in the ideal state and thereby be more efficient.

Assuming that the oscillation conditions are harmonic, the oscillation can be controlled by a controller

To represent the equation of motion of the oscillating system, where x represents the position coordinates, t represents the time, m represents the mass moved, c represents the damping coefficient, and k represents the return force.

All high-pressure roller presses described to date start from a linear term in the control or regulation of the oscillation situation. The linear term is the return force k in the preceding equation. The restoring force is varied in order to adaptively avoid oscillation tendencies in the event of oscillations. So k is changed in the equation of motion.

The moved mass of the press roll cannot be changed and remains the same. From this point on, the intervention of the damping constant c can be a possibility of an intervention system which follows the aforementioned equation of motion and can nevertheless be described at least in good approximation by this.

In order to avoid vibrations during operation of the high-pressure roller press, the inventive concept provides for the damping to be adapted by means of a control loop (Regelschleife) in such a way that, in the case of detected vibrations, the settling behavior of the dancer of the high-pressure roller press is as closely as possible in accordance with the aperiodic critical damping behavior (aperiodichen Grenzfall) of the damped oscillator. As a guide term, a settling time or a relaxation time is given, during which the system returns to the non-oscillating state again after the occurrence of the inevitable oscillations, for example when a mill constituent which cannot be broken by brittle fracture passes through or when the mill constituent changes and/or when the mill moisture changes. The inevitable oscillations enter the system as a disturbance variable, which is not calculated by oscillation analysis, and the damping term enters the control loop as a control variable. The connecting channel of the regulating circuit is the channel of the dancer roller which is to be prevented from the inevitable oscillations, and the damping of the dancer roller movement, both of which are in an interacting state. Since the dancer can also be subjected to excessive damping, and in the case of excessive damping can be converted into a so-called undesired "overdamped situation" (Kriechfall), a regulation is necessary which, on the one hand, avoids an overdamped situation detectable by oscillation analysis, but, likewise, avoids vibrations which occur if the damping is too low. Since in high-pressure roller presses the observable undesired natural frequency of the dancer roll is close to its operating rotational frequency or close to its harmonics, the high-pressure roller press is liable to excite itself to an oscillating state in operation. The adaptive damping by regulation allows the high-pressure roller press to operate quietly and smoothly, and the high-pressure roller press operates for as little time as possible outside the ideal operating parameter interval of the roller gap. The desired operating parameters are the peripheral speed of the press rolls, the roll gap width, the roll gap pressure and the mill flow, which is the quotient of the mill feed quantity and time.

In the previously known regulating systems for avoiding oscillation states of high-pressure roller presses, it is the ideal operating parameter that is influenced, namely the roll gap pressure, which can be set by the hydraulic pressure and is proportional to the hydraulic pressure, and which can also be regulated by the roll gap width, which necessarily increases when the pressure drops. The average rotational frequency of the pressure roller can be assumed to be approximately constant in view of the large mass and the moment of inertia occurring with the large mass. In a corresponding adjustment by the feed device, the mill flow can likewise be regarded as constant in suitability. The condition of the mill is not sufficiently constant, especially when it comes to mill tending to enclose air and to mill homogeneity. Thus, the variation in mill stock characteristics can be understood as the maximum average disturbance variable, followed by the homogeneity of the mill stock flow. These two disturbances cause the floating rolls of the high-pressure roller press to self-oscillate as a result of the rotation. In comparison with the methods known hitherto, adaptive damping regulation is more suitable for running the roll gap pressure and the roll gap geometry outside the ideal conditions for as little time as possible.

Described here is a method for controlling the damping of the movement of a floating roller of a high-pressure roller press, wherein the high-pressure roller press has a hydraulic system which presses the floating roller against a fixed roller and thereby maintains a predetermined roller gap pressure in the roller gap between the floating roller and the fixed roller when the rolling stock passes through the roller gap between the floating roller and the fixed roller, which method in its specific embodiment can have the following steps: measuring mechanical oscillations on the machine frame in at least one position as a first step, and/or measuring pressure fluctuations in the hydraulic system in at least one position as a first step, and/or measuring current fluctuations of the current consumption of at least one drive motor as a first step, wherein the at least one mechanical oscillations and/or the pressure fluctuations and/or the current fluctuations enter the regulated control loop as at least one disturbance variable. After the measurement, an oscillation analysis is carried out as a mathematical operation in a process computer. Such oscillation analysis may include: low-pass filtering, high-pass filtering, band-pass filtering. Fourier transformation, in particular fast fourier transformation, may be performed. Methods of statistically flattening the data, such as singular value decomposition, may be employed. A mathematical gaussian convolution and noise reduction system can also be used. Finally, a mathematical lock-type booster simulation can also be used, in which the signal to be filtered is modulated with a periodic signal in order to filter the signal. The person skilled in the art is free to choose a desired oscillation analysis method here. After the oscillations are determined by the oscillation analysis, the next step is carried out, namely determining at least one damping constant from the results of the oscillation analysis. The damping constant is a constant before the first order derivative term in the equation of motion for a harmonic, buffered oscillator. In known oscillation conditions, the damping constant may infer a desired settling condition of the overall system. If the damping constant is too large, the dancer of the high-pressure roller press to be adjusted can tend to fall into an undesirable over-damping situation, in which the high-pressure roller press is operating outside of ideal conditions and thereby inefficiently, but consumes energy. If the damping constant is too small, the floating rolls of the high-pressure roller press tend to oscillate mechanically, which causes great damage to the high-pressure roller press, to the foundation, and in the worst case also to the environment, for example, the occurrence of breaks in the building due to vibrations transmitted through the ground to the foundation of the operating site. The next following control step is to compare the at least one damping constant with a respective predetermined damping constant, wherein the respective predetermined damping constant is used as a reference variable in the control loop. The damping constant indirectly describes the settling time or relaxation time of the dancer roll. With the result of the comparison, the next step of the regulation is followed, namely the arrangement of at least one adjustable throttle in the hydraulic system, wherein the throttle position of the respective adjustable throttle enters the regulating circuit as a regulating variable, wherein the respective adjustable throttle in the hydraulic system exerts a damping effect on the movement of the dancer and the regulating circuit is thereby closed. The step of comparing the obtained damping constant with the setpoint damping constant can likewise be carried out by a known PID regulation, but also by a PI regulation, PD regulation or ID regulation, where P stands for "proportional", I stands for "integral" and d stands for "derivative". The measurement and regulation technicians are familiar with this regulation strategy, for which reference is made to the corresponding technical literature.

The details described hereinbefore are particularly suitable for systems for regulating high-pressure roller presses, in which a very large number of necessarily oscillating states are measurable. In contrast to the strip roll, which has a quieter, i.e. vibration-free operating state due to the nature of the rolling process with steel materials having good elongation properties, the high-pressure roller press has vibrations which originate, for example, from the following: relatively high-frequency vibrations due to the use of a roll surface equipped with a large amount of hard bodies, so-called "spiked-in", inhomogeneous mill stock properties, sudden embrittlement of the mill stock to be comminuted, a frequency converter operating with an industrially customary alternating current of 400Hz (so-called mains hum) with a large current consumption around the plant, and frequency converters operating with a current of 50Hz or 60Hz depending on the line frequency, are likewise possible. In certain cases, if the rolls have been cleaned or are sometimes no longer perfectly cylindrical or have surface damage as a wear phenomenon, other oscillations can be produced by bearing impacts and by the rotation of the rolls themselves. Finally, the machine frame exhibits many types of natural frequencies, such as bending oscillations, torsional oscillations, longitudinal oscillations of the steel strip. In the case of high loads, these oscillations can likewise occur as torsional oscillations of the shaft for driving the dancer. Finally, undesirable bearing vibrations due to gear engagement can also be found again in the overall vibration model of the high-pressure roller press.

In order to filter out the vibrations necessary for the adjustment from a complex vibration spectrum and to disregard the unavoidable vibrations, it is suitable to perform a fourier transformation (frequency transformation) for the oscillation analysis and to adjust only by means of peaks (english peaks) found in the spectrum for which the frequency transformation has been performed. The unavoidable vibrations mean, for example, high-frequency power supply hum, bearing damage, the rhythmic loading of the high-pressure roller press with grinding stock by means of a lift, or the undesired rhythmic transport of the high-pressure roller press by means of an overloaded conveyor belt. As a design of the oscillation analysis, the following sequence of steps is applicable: fourier transforming the measured oscillations and/or pressure fluctuations and/or current fluctuations, selecting a predetermined linear combination of the individual frequency components from the Fourier transformed oscillations, deriving a damping constant for each Fourier transformed oscillation from the time series of frequency components, and tuning the damping constant back to the regulator. The damping constant may be determined by regression, wherein the regression calculation is based on a linearized exponential function. The exponential coefficient of the decay curve is obtained in a computational manner by a numerical statistical method. For the evaluation of data analysis on numerical statistics, reference is likewise made here to the corresponding literature.

For the processing of the data, it is suitable to process the data from the measured oscillation diagram before the fourier transformation by means of mathematical low-pass filtering.

Although the microcontrollers used today in the measuring and regulating units are capable of processing very complex, large amounts of data, it is advantageous, in order to simplify the data analysis, to weight the damping constants that have been derived in the regulation of the linear combination according to the specific oscillation state ("oscillation 1 with frequency 1 is significant when oscillation 2 with frequency 2 occurs simultaneously") and to synthesize a weighted damping constant. For this purpose, if more than one damping constant is obtained, it is provided that the different damping constants are weighted and that the weighted damping constants are combined to one value.

A very special type of damping can be achieved by using an adjustable one-way throttle in the hydraulic system. The one-way throttle valve stands out by a fluid flow which is throttled uniformly in both directions, wherein the strength of the throttling effect can be adjusted by means of an actuator. And a check valve is provided in parallel with the throttle valve. The check valve is open to fluid in a first direction and closed to fluid in an opposite second direction. The use of such a one-way throttle valve installed in the hydraulic system enables the dancer roll to move freely with little additional throttling damping and to move again in the hydraulic system independently of the return force of the airbag accumulator (undamped) but only damped on the fixed roll, and also enables the settling time (relaxation time) of the dancer roll to be significantly shortened, thereby further improving the damping effect. A significantly nonlinear term describing the movement of the dancer is introduced into the equation of motion via a one-way throttle. The analytical description and calculation of settling times by means of nonlinear terms is virtually impossible. The mathematical model used as a basis is not important for the regulation system, but only if the relaxation time is used as a basis for the number of zero crossings of the movement and the time required for this as a quantity for the damping constant.

By regulating the high-pressure roller press with a constant pressure, it is necessary for the hydraulic system to have a circuit breaker and/or for the dancer roll to have a stop in order to prevent the dancer roll from directly contacting the fixed roll during idling. If the rollers touch under pressure, it is more likely that the stiffening of the surface by the stiffening body will be impaired here. In order to make the high-pressure roller press insensitive to undesired idle running, it can be provided that the hydraulic system has an automatic pressure cutoff which is activated when the dancer roller approaches the fixed roller more closely than a predetermined value, wherein a mechanical switch on the machine frame detects the approach of the dancer roller to the fixed roller. Similar results can be achieved with mechanical stops.

Drawings

The invention is further elucidated with the aid of the following figures. Wherein:

figure 1 shows a high-pressure roller press with exemplary locations for strain gauges,

figure 2 shows an exemplary raw oscillation diagram of an oscillation detector,

figure 3 shows the oscillation chart of figure 2 after processing through a low pass filter,

figure 4 shows a graph of the processed oscillations of figure 3 after fourier transformation,

figure 5 shows a schematic diagram of the selection of the fourier coefficients of figure 4 over time,

figure 6 shows the fourier series of figure 4 selected by a threshold,

figure 7 shows an inverse of the fourier series selected in figure 6,

figure 8 shows the effect of insufficient (too small) damping on the dancer oscillation condition,

figure 9 shows the effect of ideal (optimal) damping on the dancer oscillation conditions,

figure 10 shows the effect of excessive damping on the dancer oscillation condition,

figure 11 shows a high-pressure roller press with a hydraulic system according to the prior art,

fig. 12 shows a design of a high-pressure roller press according to the invention, with a maximum number of oscillation sensors and optionally a one-way throttle valve,

fig. 13 shows a repetition of fig. 8, 9, 10 resulting from the situation in which an adjustable throttle valve is used, in order to compare with the diagram of fig. 14 in a similar situation in which a one-way throttle valve is used,

fig. 14 shows the graphs of fig. 8, 9, 10 in the case of using the one-way throttle valve.

Detailed Description

Fig. 1 shows a high-pressure roller press 1 of this type with two press rollers rotating in opposite directions as a fixed roller 2 and a floating roller 3, the fixed roller 2 and the floating roller 3 being accommodated in a machine frame 4, which itself is provided at different locations with sensors 20 for detecting an oscillating movement. The two press rolls, i.e. the fixed roll 2 and the floating roll 3 of the high-pressure roller press 1, are pressed against one another by means of the

hydraulic struts

17, 18, without contacting one another in this case. The roller material to be comminuted is fed to the roll gap 7 between the fixed roll 2 and the loose roll 3 of the high-pressure roller press 1 by a feed device not shown here and is comminuted there by the pressure between the two rotating press rolls, i.e. between the fixed roll 2 and the loose roll 3. The comminution is carried out by brittle fracture while avoiding shear stresses. Strain gauges 20 as sensors for detecting an oscillating movement are mounted at different positions of the machine frame 4 of the high-pressure roller press 1. The oscillations measured by the strain gauges 20 are passed on to an evaluation device, not shown here, which compares the amplitude and/or frequency of the measured oscillatory movement with previously determined target values. If the amplitude exceeds a critical value in the case where the frequency obtained by fourier transformation or, in general, by frequency filtering has been preset, the position of the throttle valve, not shown in the figure, changes, whereby the damping of the movement increases. If the intensity of the oscillating movement is below the previously determined critical interval due to the increase in the damping effect of the throttle valve, the damping is slowly reduced by an adjusting strategy, preferably a PID method, so that the roller press 1 always operates in a damping interval which places the mechanical oscillating movement of the dancer roll as much as possible in the event of an aperiodic critical damping of the damped oscillation. Since the entire system of the high-pressure roller press 1 with an unnecessarily linear damping of the movement of the bearing blocks in the machine frame 4 cannot be described in its entirety by the motion equation of the damped harmonic oscillation, the regulating strategy seeks a damping which is as close as possible to the motion diagram of the aperiodic critical damping case, with an initial offset in the first direction, with a very slight return of the super-oscillation and slowly approaching the zero position.

FIG. 2 is shown in an exemplary manner as F ₁ (t) (function 1 as a function of time t) oscillation profiles that can be detected by almost any motion sensor. The abscissa shows the offset of the machine (english displacement) and the ordinate shows the time t (english time). With regard to the sensor for measuring oscillations, consideration is given in particular to: strain gauges 20 at different positions of the machine frame 4. The strain gauges 20 can measure longitudinal oscillations of the metal belt of the machine frame 4, as well as torsional oscillations of the drive shaft. When a metal strip oscillates like a guitar string, acceleration sensors also at a number of locations of the machine frame 4 can measure the bending vibration of the respective metal strip. Although the oscillation of the amplitude of such a local decomposition is very small, usually only within a few μm intervals, it is sufficient to measure typical oscillations. The acceleration sensor can likewise perform a measurement when the entire high-pressure roller press 1 performs a corresponding reverse movement in space due to the oscillating floating roller 3. Recording of pressure in the hydraulic system 8 and measurement of the current consumption of the drive motorThe quantities are suitable as other sources of measurement. Each measurement source has its own superposition of typical, negligible oscillations, for example a very high line frequency or converter frequency when measuring the current consumption, a rotational frequency when measuring the acceleration by means of an acceleration sensor and harmonics thereof, for example the line frequency when measuring longitudinal oscillations and the frequency which occurs as a loud noise due to crushing cracks, i.e. non-gaussian noise with strong signal peaks. The acceleration sensor, which is located directly on the bearing block, receives the actual vibration of the dancer roll as the primary oscillation. The aim of the invention is to adjust the damping state by means of the detected oscillations before a strongly oscillating back-and-forth movement of the dancer roll 3 occurs.

For first processing the utilization signal, it may first be low pass filtered, thereby suppressing the gray scale noise and line frequency. The result of the low pass filtering is presented as F in FIG. 2 in FIG. 3 ₂ (t) (as a function of time t, 2) of the shifted time plot. Basically, two oscillations of different frequencies can also be seen here, namely the main fundamental oscillation and the remnants of harmonics and higher harmonics.

Fig. 4 shows a fourier transform that can be understood to frequency filter the signal in parallel channel a) \8230; \8230b) \8230; n). Fourier transform converts the signal of FIG. 3 into a frequency-time graph, in which the frequency of channel a) is a function F _a (F, t) (according to a function a of frequency F and time t)), the frequency of channel b) as a function F _b (F, t) (function b according to frequency F and time t)), frequency of channel n) as function F _n (f, t) (according to a function n of frequency f and time t)).

The dominant oscillation in channel a) is selected here and is shown in fig. 5 as a) mapped over time t. Damping part e of oscillation ^-(x(a)*1) The coefficient x (a) is adapted to regression analysis in order to derive a damping coefficient by which damping adjustments can be carried out. For the coefficient F _a Regression analysis of the time trend of (f, t) the value x (a) can be determined assuming a negative power trend. It was observed in the present invention that the gradual oscillations of the dancer roll 3 to be avoided can already be typical in advanceIs identified, which is found in the own oscillation frequency of the machine frame of the high-pressure roller press. The strong, heavy steel strip of the machine frame of the high-pressure roller press clearly shows a strong oscillation model of the machine frame before the gradual oscillation of the dancer roll 3 occurs. In order to identify such a model, it is merely necessary to track the high-pressure roller press 1 with a sensitive oscillation analysis and to recognize the oscillation model in a time-wise manner before the floating roller oscillations that are to be avoided occur. This can be done by conventional statistical methods, i.e. by temporal correlation analysis, but it is also possible for the person skilled in the art to identify the model purely by eye. If the model is identified at a single moment, it can be programmed into the regulating device as a typical model that is unique to the machine frame.

Depending on the oscillation model to be observed, it is possible to pick different coefficients after the fourier transformation. In the simplest case, it is also possible to define a threshold value and to recognize all coefficients exceeding this threshold value as the main oscillation component. This process is illustrated in fig. 6, where coefficients a), b) exceed a threshold C (coefficient in english). The inverse of the fourier coefficients indicates that there are oscillations of different phase, dominant, higher harmonics, which correspond to the difference from the own frequency in this example. These two inverse transformed oscillations are shown in fig. 7.

The upper oscillation is shown in fig. 7 as an offset D (english displacement) of the frequency with the coefficient a) over time t). The lower oscillatory graph shows the offset D (english displacement) of the frequency with coefficient b) over time t).

The regulating strategy now derives, from the damping of the oscillations, for example, in fig. 7 by means of a continuous signal (fig. 5), a factor x (a) for damping the equation of motion of the exposed oscillations in the machine frame 4 of the high-pressure roller press 1. This signal is the return signal into the regulation loop. If the damping is too strong and the factor x (a) is therefore too large, the damping of the movement of the dancer roll 3 is reduced by partially opening the throttle valve of the throttle valve in the hydraulic system 8 of the high-pressure roller press 1, and vice versa.

Fig. 8 (too little damping), fig. 9 (ideal damping), fig. 10 (too strong damping) show different adjustment states. If the damping is too low, the dancer roll 3 will stabilize after several oscillation cycles when the oscillations are excited by external forcing, for example by rotation of the dancer roll 3 at a preset rotational speed, which is the rotational speed of a specific roll gap pressure, which is proportional to the hydraulic pressure of the

hydraulic struts

17, 18 and which is an unsuitable material property of the grinding stock. If a 100t heavy roller oscillates back and forth at a frequency significantly greater than 1Hz, the impact thereby transmitted to the ground area can cause damage in the most immediate environment. It has been observed that a non-compliant, unmonitored high-pressure roller press causes fractures in the ground of a nearby operating site. Such a state is to be avoided. If the damping is too great, the high-pressure roller press 1 operates quietly. In the case of an overdamped situation (fig. 10), in which the dancing roll 3 is set back again slowly to the ideal operating point D =0 after deflection, the occurrence of an overdamped situation means that the high-pressure roller press operates inefficiently at this time. The roll gap is too large and the material passing through is not fragmented but rather greatly broken into coarse pieces. The shaded area under the curve in fig. 10 shows the shift in time. The greater the offset D (english displacement), the more inefficiently the high-pressure roller press 1 works. Fig. 9 shows how the dancer roll 3, after deflection, for example by the passage of a shovel tooth or by the passage of an excessively large grinding block, again after a short time of one-time overstriking at time t _max In equilibrium and thereby at the desired operating point.

Fig. 11 shows a high-pressure roller press known from the prior art, which has a fixed roller 2 and a floating roller 3. The dancer 3 is pressed against the fixed roller 2 by means of

hydraulic struts

17, 18. For applying the force, hydraulic fluid from a reservoir 23 is pumped into the pistons of the

hydraulic props

17, 18 by means of a hydraulic pump 19. In order to counteract the sudden load peaks (passage of the excavator teeth, passage of metal blocks, excessively large grinding blocks, etc.), a gas-bag accumulator 14 is provided which has a gas cushion under pressure against which the hydraulic fluid can expand when it leaves the pistons of the

hydraulic props

17, 18 in the form of a shock by the sudden movement of the floating rollers 3 and is flushed back into the pipe system of the hydraulic system.

Fig. 12 shows a design of a high-pressure roller press according to the invention. The important element here is an adjustable throttle 15 or an adjustable one-way throttle 16 between the hydraulic system 8 and the bag accumulator 14. By means of the throttle 15 or the one-way throttle 16, the movement of the dancer roll 3 can be damped when the working pressure in the roll gap is constant. In the case of a one-way throttle valve 16, the hydraulic fluid can flow rapidly and undamped through a bypass 16.2 in the event of a displacement of the dancer 3 in the form of a shock towards the airbag accumulator 14 and expand there. However, the return flow from the pressurized bladder accumulator 14 is damped by the throttle 16.1, since the throttle 16.1 defines a free cross section for the throughflow of hydraulic fluid. The viscosity of the hydraulic fluid thus causes a counter force opposite to the flow velocity of the hydraulic fluid. The high-pressure roller press 1 has different oscillation sensors, which each produce a separate oscillation diagram as the disturbance variable 13. Here, it concerns strain gauges 20 at different positions of the machine frame, acceleration sensors also at these positions, a digital manometer 21 in the hydraulic system 8 for sensing pressure fluctuations, and a digital ammeter 22 for sensing oscillations in the current consumption of the electric drive motor. All of these sensors provide an oscillating chart of the processing utilizations as previously described. From the damping coefficient which has been derived and which represents the oscillation condition of the dancer 3, the regulating device derives a regulating value for the throttle valve 16.1, for example according to a PID regulating strategy. The throttle valve 16.1 acts on the oscillation condition of the dancer 3 and the control loop is thus closed. In the present example of a high-pressure roller press, a position switch 24 is present, which prevents the dancer roll 3 from contacting the fixed roll 2 under pressure. If the dancer roll 3 is too close to the fixed roll 2, the position switch 24 switches off the hydraulic pump 19 in order to avoid damage on the hard reinforcements (press rolls, i.e. the rectangular pattern on the dancer roll 3 and the fixed roll 2).

Fig. 13, 14 show the different effects of the throttle 15 and the one-way throttle 16 on the settling time (relaxation time) of the dancing roll 3. Fig. 13 is a mere repetition of fig. 8, 9, and 10. FIG. 14 shows in the middle example that the choke valve 16 makes the said settling time (relaxation time) t _max Is obviously shortened to t _max,neu . In the yielding movement, the dancer 3, which is not damped or has a lower damping, can be retracted with the roller gap 7 open, which is illustrated in the middle diagram of fig. 14 by a thick arrow to the right, which is very to the left. The bold arrows represent fast, unbraked or undamped motion. In this return movement, the non-return valve 16.2 is open and hydraulic fluid flows through the bypass, the non-return valve 16.2 and through the throttle valve 16.1. In the forward movement of the dancer roll 3 towards the fixed roll 2, the non return valve 16.2 is closed and the hydraulic fluid from the airbag accumulator 14 has to take its way through the throttle valve 16.1. By means of the throttle valve 16.1, the return movement of the dancer 3 takes place relatively slowly and with damping by the pressure in the airbag accumulator 14, wherein the damping is indicated by the left, non-thickened arrow, which can assume a slower movement by means of a stronger damping. In this case, enormous kinetic energy is consumed. The amplitude of the ringing behaves almost as in the case of the throttle valve 15 alone, without the bypass/check valve 16.2, during the return period. As soon as the return point in the overstrike is reached, the dancer roll 3 is again moved free of damping (right-hand, right-hand thickened arrow) into the desired position by the force of the compacted roller. The return action is here faster when a one-way throttle 16 is used than in the case of damping in both directions by means of a throttle 15 acting identically in both flow directions. By a rapid movement in one direction, the settling time (relaxation time) t _max,neu Is significantly shorter, so that the high-pressure roller press 1 is operated only for a very short timeDuring the time interval, outside its ideal operating point. It is pointed out here that by using a one-way throttle, a stronger, non-harmonic element is incorporated into the movement system of the dancer roll 3, which may lead to stronger higher harmonics of the equation of motion and thus to stronger jerking moments (third derivative of position in the equation of motion as a function of time) which can act as shock waves moving through the ground area and which exhibit their influence at undesired positions. However, the great advantage of the invention is that the adaptive damping is adjusted by oscillation analysis, so that the impact occurs in a significantly reduced state. In comparison with the case of damped movements in both directions, unavoidable shocks, for example, generated when the excavator teeth pass through the roll gap, occur as a result of the unbraked or undamped evasive movement of the loose rolls 3 with significantly less shock wave conduction to the ground area. Thus, strong impacts on the ground area or on the machine frame are attenuated, whereas the avoided rhythmic and non-harmonic oscillation components are intensified. Since these stronger oscillating parts are leveled from the beginning, the advantages of the damping method are applicable to the whole field of application.

List of reference numerals

1. High-pressure roller press

2. Fixed roller

3. Floating roller

4. Machine frame

7. Roll gap

8. Hydraulic system

10. Regulator

11. Reference variable

12. Regulating the parameter

13. Amount of interference

14. Air bag type energy accumulator

15. Adjustable throttle valve

16. Adjustable one-way throttle valve

16.1 Adjustable throttle valve

16.2 By-pass, check valves

17. Hydraulic prop

18. Hydraulic prop

19. Hydraulic pump

20. Strain gauge

21. Digital pressure gauge

22. Digital ammeter

23. Storage device

24. Position switch

30. Oscillation chart

31. Fourier transform

a) Time series

b) Time series

D offset

Coefficient of C

e base of natural logarithm

p pressure

time t

t _max Stability approaching time (relaxation time)

t _max,neu Shortened settling time, shortened relaxation time)

f frequency

Function of F

Claims

1. A method for adjusting the damping of the movement of a dancer roll (3) of a high-pressure roller press (1),

wherein the high-pressure roller press (1) has a hydraulic system (8) which presses the floating roller (3) against the fixed roller (2) and thereby maintains a predetermined roller gap pressure in the roller gap (7) between the floating roller (3) and the fixed roller (2) when the ground material passes through the roller gap (7) between the floating roller (3) and the fixed roller (2),

characterised in that adaptive damping regulation is used, which monitors the damping of the mechanical oscillation movement of the dancer roll.

2. Method for adjusting the damping of the movement of a dancer roll (3) of a high-pressure roller press (1) according to claim 1, wherein the adaptive damping adjustment carries out the following adjustment steps:

-measuring mechanical oscillations on the machine frame (4) in at least one position, and/or

-measuring pressure fluctuations in the hydraulic system (8) in at least one position, and/or

-measuring current fluctuations in the current consumption of the at least one drive motor,

wherein the at least one mechanical oscillation and/or pressure fluctuation and/or current fluctuation enters the regulated control loop as at least one disturbance variable,

performing an oscillation analysis as a mathematical operation in a process computer,

deriving at least one damping constant from the results of the oscillation analysis,

-comparing the at least one damping constant with in each case one preset damping constant, wherein the in each case one preset damping constant enters the control loop as a reference variable (11),

-at least one adjustable throttle (15, 16) is arranged in the hydraulic system (8), wherein the throttle position of each adjustable throttle (15, 16) is fed into the control circuit as a control variable (12),

wherein each adjustable throttle (15, 16) in the hydraulic system (8) damps the movement of the dancer (3) and the regulating circuit is thereby closed.

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

using a one-way throttle valve (16) which is connected into the hydraulic system in such a way that

-the movement of the dancer roll (3) allows hydraulic fluid to pass through the throttle (16.1) through a bypass (16.2) in the one-way throttle (16) with the roll gap (7) open,

-the movement of the dancer roll (3) allows only hydraulic fluid to pass through the throttle valve (16.1) in case the roll gap (7) narrows.

4. The method according to any one of claims 2 to 3,

it is characterized in that

The sequence of the following steps in the oscillation analysis:

fourier transforming the measured oscillations and/or pressure fluctuations and/or current fluctuations,

-selecting a preset linear combination of the individual frequency components from the Fourier transformed oscillations,

deriving a damping constant for each Fourier transformed oscillation from the time series of frequency components,

-directing the damping constant back to the adjuster (10).

5. The method of any one of claims 2 to 4,

it is characterized in that

-low-pass filtering the measured oscillations and/or pressure fluctuations and/or current fluctuations before the step of fourier transformation.

6. The method of any one of claims 2 to 4,

it is characterized in that

-weighting the different damping constants,

-integrating the weighted damping constants into one value when more than one damping constant is derived.

7. A high-pressure roller press (1) has

-at least one fixed roller (2), and

-at least one dancer (3),

wherein the high-pressure roller press (1) has a hydraulic system (8) which presses a respective floating roller (3) assigned to the fixed roller (2) against the assigned fixed roller (2) and thereby maintains a predetermined roller gap pressure in the roller gap (7) between the floating roller (3) and the fixed roller (2) when the rolling stock passes through the roller gap (7) between the floating roller (3) and the fixed roller (2),

it is characterized in that the preparation method is characterized in that,

adaptive damping regulation monitors the mechanical oscillating movement of the dancer.

8. The high-pressure roller press according to claim 7,

it is characterized in that the preparation method is characterized in that,

in the hydraulic system (8) there are adjustable throttles (15, 16) which can be adjusted by means of an adjuster (10) for adjusting the damping of the fluid flow in the hydraulic system (8).

9. The high-pressure roller press according to any one of claims 7 or 8,

it is characterized in that the preparation method is characterized in that,

the hydraulic system (8) maintains a constant pressure (p).

10. The high-pressure roller press according to any one of claims 7 to 9,

it is characterized in that the preparation method is characterized in that,

the hydraulic system (8) has an automatic pressure cut-off which is activated when the dancer roll (3) comes into contact with the fixed roll (2) closer than a preset value, wherein a mechanical switch (24) on the machine frame (4) detects the approach of the dancer roll (3) to the fixed roll (2), and/or the high-pressure roller press has a mechanical stop for the dancer roll, which stops the dancer roll from coming into contact with the fixed roll under pressure.

11. The high-pressure roller press according to any one of claims 7 to 10,

it is characterized in that the preparation method is characterized in that,

the regulator (10) operates according to claims 1 to 5.

12. The high-pressure roller press according to any one of claims 7 to 11,

it is characterized in that the preparation method is characterized in that,

the hydraulic system (8) is buffered by a gas bag type energy accumulator (14), and the gas bag type energy accumulator is connected with the hydraulic system (8) through the adjustable throttle valves (15, 16).

13. The high-pressure roller press according to any one of claims 8 to 12,

it is characterized in that the preparation method is characterized in that,

the adjustable throttle (16) is a one-way throttle.