Method for operating a roller press for the compacting or briquetting of material and roller press for compacting or briquetting material

Abstract

The invention relates to a method for operating a roller press (1) for the compacting or briquetting of material, wherein the roller press (1) has two counter-rotating press rollers (2) between which a roller gap is formed, and wherein at least one of the roller surfaces of the press rollers is provided with a profiling, wherein the material is pressed in the roller gap between the roller surfaces to form a sheet (3) or to form briquettes or a briquette strand, wherein the rollers are preferably cooled during operation. The method is characterised in that at least one characteristic variable is continuously determined during operation, which characteristic variable depends on the formation of caking of the material on the profiled roller surface or on the profiled roller surfaces, and in that one or more operating parameters of the press are changed depending on the at least one determined characteristic variable in order to reduce the caking.

Description

[0001] Method for operating a roller press for compacting or briquetting material and roller press for compacting or briquetting material

[0002] Description:

[0003] The invention relates to a method for operating a roller press for compacting or briquetting material, wherein the roller press has two counter-rotating (e.g., rotationally driven) press rollers (i.e., compacting rollers or briquetting rollers) between which a roller gap is formed, wherein the roller surface(s) of one or both press roller(s) is / are provided with a profile (e.g., corrugation or briquette troughs), wherein the material is pressed in the roller gap between the (profiled) roller surfaces into a slug or briquettes or a briquette strand. Preferably, the roller surfaces are cooled (during operation) and consequently tempered by cooling.

[0004] Furthermore, the invention relates to a roller press which is operated by such a method and which is designed either as a compacting press for compacting material or as a briquetting press for briquetting material.

[0005] The roller press, which is a briquetting press or a compacting press, is designed as a high-pressure roller press in which the material, e.g., granular or loose material, is compressed in the roller gap under high pressure. In a compacting press, the material is compressed in the roller gap into a continuous strand of material, referred to as a slug. In a briquetting press, the material is compressed in the roller gap by the briquetting tools (with briquette troughs) arranged on the roller surfaces into briquettes or a briquette strand made up of a plurality of briquettes. In both cases, at least one of the press rollers is connected to the other by force-generating means, e.g., hydraulically.

[0006]

[0007] Press roll adjustable. The press rolls can, for example, each have a roll core (with a shaft) and a bandage arranged on the roll core or tool segments arranged on the roll core, wherein the bandage or the segments are provided with the roll surfaces and thus form the roll surfaces.

[0008] The roller press, in its compacting form, is used, for example, for the production of fertilizer granules through so-called press granulation or compacting granulation. The starting material (e.g., inorganic substances) is pressed under high pressure in the high-pressure roller press and compacted, creating a strand of material, the so-called slug. This process step is called press agglomeration. This is usually followed by a further step (with a separate system component, e.g., a crusher and / or mill) of granulation by comminution of the slug, followed preferably by classification.

[0009] In a briquetting press, the roller surfaces are usually formed by a bandage or segments equipped with briquette troughs. The starting material is pressed in the roller gap into the aforementioned briquettes or a briquette strand. The briquette strand can be separated into briquettes in a subsequent process step. Briquetting is used, for example, to produce HBI (Hot Briquetted Iron), by directly pressing reduced iron into briquettes.

[0010] During operation, compacting presses, for example, tend to cause the material to stick to the profiled roller surfaces when compacting inorganic substances for fertilizer production. This sticking is also referred to as melting. The melting tendency depends on the

[0011]

[0012] The temperature of the roller surfaces depends on the feed temperature and, consequently, the temperature of the hot feed material. The melting tendency can also be indirectly influenced by the ambient temperature, since at higher ambient temperatures the temperature of the feed material generally rises due to reduced heat loss. With higher feed temperatures, the melting tendency increases. For this reason, the rollers of compacting presses for fertilizer production, for example, are cooled during operation, e.g., by internal cooling, which also leads to cooling of the roller surfaces to counteract the melting tendency. The same applies to briquetting.

[0013] For example, DE 10 2012 106 527 A1 discloses a press roll for a roller press with a roll core and a coolable bandage attached to the roll core. Several axially parallel cooling channels are arranged in the bandage below the surface of the bandage, distributed around the circumference and connected to an axial central channel in the roll core via radial inlet and outlet channels. The cooling from the central channel to the cooling channels in the bandage is distributed via distributor rings connected to the front of the bandage.

[0014] The production of fertilizer granules using a roller press and a downstream two-roller mill is described, for example, in DE 10 2020 131 638 A1. The focus of this state-of-the-art technology is the cooling of the grinding rollers of the two-roller mill, which is located downstream of the high-pressure roller press and serves to crush the fertilizer slurry.

[0015] Methods for monitoring the operation of a high-pressure roller press are known from DE 10 2020 114 815 A1 and DE 10 2020 114 835 A1.

[0016]

[0017] Monitoring the operation of roller presses is particularly well known for roller presses that are not used for compacting or briquetting material, but rather for comminuting it, and are also known as high-pressure roller mills. The primary focus is on monitoring wear or damage to the roller surfaces. Examples can be found in WO 2023 / 104294 A1, WO 2022 / 023869 A1, WO 2014 / 068453 A1, WO 200809016 A1, and DE 21 2021 000 130 U1.

[0018] DE 20 2015 106 156 U1 describes a roller mill with a sensor unit that measures the distance to a grinding surface during operation to monitor wear. An evaluation unit takes a determined wear value into account when controlling these drives. This allows the drive control of the two rollers to be adjusted so that the wear of the rollers can be influenced according to a specified criterion. For example, in the event of greater wear, the respective roller is subjected to a lower torque in order to equalize the cumulative wear of both rollers.

[0019] Furthermore, DE 197 31 975 A1 discloses a method for preventing the sticking of briquetted material to the roller surface of a briquetting press. This involves spraying a lubricant emulsion atomized with a gas onto the roller surface. Intermittent spraying is possible. Furthermore, the dosage can be automatically adjusted via a control system, depending on the sticking behavior.

[0020]

[0021] WO 2018 / 036978 A1 relates to monitoring and control systems for the automated optimization of grinding and rolling systems, in particular grinding and rolling systems for grinding and / or crushing grains or for processing by comminuting and homogenizing viscous material, in particular chocolate masses, printing inks and the like.

[0022] DE 10 2020 130 265 A1 describes a roller system used, for example, in the production and processing of a rubber or silicone material. A wetting device for applying a liquid is provided to reduce adhesion of the material to the roller.

[0023] Furthermore, JP 2017-030034A discloses a roller with an integrated device for cooling the bearings of the roller.

[0024] WO 2007 / 025395 A1 describes a method for monitoring the operating condition of rotating rollers in an industrial plant. Vibrations during operation of a roller are detected and, based on this information, measures can be taken during operation, e.g., the emission of a visual or acoustic alarm signal or even the shutdown of at least part of the plant. The focus is on roller mills for grain processing or rolling mills for processing suspensions such as chocolate or paints.

[0025] Based on the prior art, the object of the invention is to provide a method by which the operation of a roller press for compacting or briquetting material and consequently the operation of a compacting press or briquetting presses can be optimized.

[0026]

[0027] To achieve this object, the invention teaches in a generic method of the type described at the outset that during operation at least one parameter is determined continuously (i.e. at intervals or continuously), which parameter depends on the formation of caking of the material on the profiled roll surfaces, and that one or more operating parameters of the press are changed depending on the parameter (or parameters) determined in order to reduce caking on the roll surfaces.

[0028] The invention is based on the realization that buildup on the rollers of a compacting press or briquetting press, and the resulting tendency to melt, negatively impacts operation, as increasing buildup reduces press productivity. For example, during compaction, buildup can reduce flake thickness and thus reduce productivity. Reducing flake thickness also leads to an increase in the proportion of unwanted returns, which in turn reduces press productivity and generally negatively impacts the formation of buildup. On the other hand, the formation of buildup also depends on the surface quality of the rollers, as increasing surface roughness, for example, can lead to an increase in buildup.The increase in adhesions can in turn lead to corrosion of the surfaces, which results in an increase in roughness, which in turn negatively influences the tendency to adhesions in the manner described.

[0029] Based on this knowledge, the process according to the invention reduces and minimizes adhesions by

[0030]

[0031] The formation of adhesions and consequently caking is continuously monitored during operation. This is achieved by the continuous determination of a parameter that depends on the formation of caking of the material on the profiled roller surfaces. Such a parameter can be determined, for example, by direct measurement with a measuring device, e.g. with a sensor. This can be a vibration sensor, for example, so that a vibration value of the roller press is determined as the parameter. The invention has recognized that vibrations of a roller press are sensitive to the extent of caking and consequently to the tendency to melt, so that melting can be detected very effectively by monitoring vibrations. In principle, however, other parameters and consequently measured variables that depend on caking on the roller surfaces are also possible. Alternatively, the parameter can be a fluctuation value of a machine parameter, e.g.the width of the roll gap, the contact pressure of one or both press rolls and / or the motor current or the motor torque of one or both press roll drives can be determined. For this purpose, one or more measuring devices with, for example, one or more sensors can be provided. The sensor(s) measure, for example, the width of the roll gap, the contact pressure and / or the motor current or the motor torque. From the measured values, a fluctuation value is determined using the measuring device (or an evaluation device, which can also be part of the measuring device), which is a measure of the fluctuations in the respective machine parameter. This fluctuation value can be used as a measure of the caking within the scope of the invention.

[0032] Alternatively, data can be recorded in a measuring device that has one or more sensors or a camera, and the parameter can be determined (indirectly) from this data using a computer.

[0033] Monitoring the roller surface with a camera or a camera system, whereby a computer can use the image data obtained to obtain information about caking and consequently determine a parameter that is representative of the extent of the caking.

[0034] Of particular importance is that the method according to the invention reacts specifically to the formation of caking by changing one or more operating parameters of the press as a function of the determined characteristic and consequently as a function of the extent of caking, in such a way that the caking is reduced. According to the invention, the tendency to melt is therefore specifically counteracted by a predetermined control or regulation of the system. The roller press is therefore operated according to the invention in such a way that the caking that occurs during operation is removed again by suitable variation of the operating parameters of the press, i.e. the press is freed of caking during operation.

[0035] The operating parameter that can be varied to free the build-up and thus counteract the tendency to melt can be, for example, the pressure of the roller press and consequently the pressing pressure, i.e. the pressing pressure is varied during operation depending on the determined parameter, e.g. depending on vibrations or fluctuations in a machine parameter of the press. The invention is based on the finding that the build-up that occurs during operation can be removed again if (e.g. temporarily) the initially set pressing pressure is reduced by a certain amount. By reducing the pressing pressure, build-up can be reduced and, if necessary, removed. If, within the scope of the method according to the invention, due to the monitoring of the parameter

[0036] If it is determined that the buildup has reduced, the pressure can then be increased again, e.g., to a previously specified normal value. The onset of surface growth, which can be caused, for example, by high temperatures of the feed material, is thus detected, and in one embodiment, the pressure is adjusted accordingly. This reduces the energy input and normalizes the roller surface. If the parameter(s) improve, the pressure can then be increased again, e.g., to the original level.

[0037] Alternatively or additionally, the caking can be counteracted by changing the cooling and / or the temperature, i.e. the cooling and / or the temperature of the rollers, e.g. a surface temperature, is used as a variable operating parameter. This is because the rollers of the roller press are preferably each equipped with a cooling system. This can be internal cooling, e.g. via the shaft or the roller core, e.g. via a core bore. By cooling the roller body itself, the surfaces of the roller and consequently the profiled roller surfaces can also be cooled. Alternatively or additionally to internal cooling via the core, the tire or the segments can be cooled, e.g. via cooling channels. By changing the cooling, the surface temperatures of the roller surfaces can be changed, so that either the cooling itself or the resulting surface temperature can be used as the operating parameter. For example, ifIf melting or caking is detected in an operation with certain parameters, e.g., a certain pressing pressure and a certain temperature, this caking can be counteracted by reducing the temperature and, for example, by increased cooling. If this prevents the caking.

[0038] reduced, the cooling can then be reduced again and thus the temperature increased.

[0039] Alternatively or additionally, the feed temperature of the material to the roller gap can also be changed as an operating parameter, ie caking can be reduced by reducing the feed temperature, whereby the feed temperature can then be increased again if necessary after the caking has been reduced.

[0040] Alternatively or additionally, the roller speed can also be used as a variable operating parameter, i.e., the roller speed can be adjusted to reduce buildup. If, for example, buildup is detected during operation, the roller speed can be reduced. Due to the reduced throughput, this leads to an improved cooling effect and thus a reduction in buildup, so that the tendency to melt can also be counteracted by adjusting the speed.

[0041] Alternatively or additionally, the amount of material fed can also be changed as a variable operating parameter. This means that the amount of material fed to the roller press, or the flow rate or mass flow, can be changed to reduce caking. If, for example, caking is detected during operation, the amount of material fed (e.g., the flow rate or mass flow) can be reduced by adjusting the corresponding upstream units, e.g., screw conveyors, conveyor belts, or throttle valves or openings. Due to the reduced throughput, this leads to an improved cooling effect and thus to a reduction in caking, so that caking or the tendency to melt can be counteracted by varying the material feed.

[0042]

[0043] Furthermore, as an alternative or additional option, the operating parameter for reducing caking can be to reduce the return fraction, i.e., the proportion of fines returned. This can be achieved, for example, by changing the shredding process, which influences the return fraction.

[0044] Overall, the variable operating parameters of a roller press include, in particular, the pressing pressure, the cooling and / or surface temperature and / or the speed of the rollers and / or the amount of material fed in (or the quantity flow or mass flow) and / or the proportion of returned material.

[0045] In principle, it may be expedient to change only one of the operating parameters, e.g., only the pressure or only the temperature, to prevent or reduce caking. However, it is also within the scope of the invention to optionally change several operating parameters to counteract caking.

[0046] The operating method for reducing buildup can be implemented as a control system. However, closed-loop control is particularly preferred. The operating parameter(s) are modified by closed-loop control such that a deviation of a determined actual value of the characteristic from a target value of the characteristic is reduced, in particular minimized. For example, this can be a control system with variable pressing pressure, i.e., the pressing pressure is modified in a closed-loop control such that the deviation of the actual value of the characteristic, e.g., vibrations or fluctuations, from a predetermined target value is minimized.

[0047]

[0048] It can be advantageous to specify certain limits for setting the operating parameter during control so that, for example, arbitrarily low pressing pressures are not set to reduce caking. Consequently, the operating parameter or parameters can be changed, e.g. during control, on the condition that one or more specified maximum or minimum values ​​of the operating parameter or parameters are not exceeded or undercut. It is therefore preferable to define limit values ​​in the control system. It is always advantageous to carry out a target value / actual value comparison for the purposes of control. The actual values ​​can be recorded in the manner already described, e.g. by measurements with one or more measuring devices. A direct measurement of a parameter, e.g. using a sensor, e.g. a vibration sensor, pressure sensor or position sensor, can be considered.Alternatively, the parameter or the actual value of the parameter can be determined indirectly by recording data with one or more measuring devices or with a camera and calculating the parameter from this data.

[0049] The tendency to melt, which the invention aims to counteract, is due in practice, among other things, to the fact that the feed material is usually warm or hot. For example, when compacting inorganic material for the production of fertilizer granules, a certain temperature is generally required to achieve high-quality compaction. For this reason, arbitrarily strong cooling cannot be achieved, as this would impede compaction.

[0050]

[0051] Overall, the change in the operating parameters according to the invention should be carried out with the proviso that the quality of the produced flakes or briquettes or briquette strand is not impaired or does not fall below their quality requirements.

[0052] The control or regulation strategy can also be variably adapted to the respective conditions, e.g., the type of feed material or its mixing ratio and / or the ambient temperature of the press, e.g., outside and / or inside temperatures. For example, a "day mode" and a "night mode" and / or a "summer mode" and a "winter mode" can be provided and implemented in the control system.

[0053] Particularly preferably, the process is carried out using a roller press for compacting material and, consequently, using a compacting press. This can involve, for example, the compaction of inorganic material, in particular for the production of fertilizer granules, wherein at least one roller surface is provided with a profile (e.g., a ridge) for producing a slurry.

[0054] Alternatively, the process can be carried out using a roller press designed as a briquetting press and intended, for example, for briquetting directly reduced iron and consequently for producing briquettes (hot briquetted iron), wherein the roller surfaces of a briquetting press are provided with briquetting tools, ie with briquette troughs, which form the profiled roller surface.

[0055] The invention relates not only to the described method, but also to a roller press of the type described, which has two counter-rotating press rollers, between which a roller gap is formed and whose

[0056] at least one roller surface (or both roller surfaces) is / are provided with a profile. It can be a roller press as a compacting press or briquetting press. The roller press according to the invention is equipped with a control device (e.g. a control and / or regulating device) which is designed to carry out the described method. In particular, this control device (e.g. as a regulating device) can be implemented with a control algorithm of the type described. Furthermore, the roller press preferably has at least one measuring device with which the at least one parameter which, for example, flows into the control process can be determined directly or indirectly. Reference is made to the explanations for the claimed method, which also apply to the claimed roller press.

[0057] The invention will be explained in more detail below with reference to drawings which merely represent exemplary embodiments.

[0058] Fig. 1 schematically simplified a plant for the production of fertilizer granules with a roller press,

[0059] Fig. 2 schematically simplified a roller press with a control and / or regulating device for carrying out the method according to the invention and

[0060] Fig. 3 is a process diagram relating to an embodiment of the process according to the invention.

[0061] Figure 1 shows a simplified schematic representation of a plant for the production of granules, e.g., fertilizer granules. The plant comprises a roller press 1 (as a compacting press) with two counter-rotating

[0062] rotating press rollers 2, between which a roller gap W is formed. The starting material M, e.g. inorganic substances for the production of fertilizer, is fed onto the roller press 1 and compacted in the roller gap W between the press rollers 2 into a strand of material, the so-called slug 3. The slug 3 is then crushed into granules 5 in one or more comminution units, e.g. roller mills 4. The material emerging from the mills 4 is classified in a classifying device 6, e.g. a screening device, and the end product EP is thus discharged, while fine material R is returned and fed back to the roller press 1. The present invention relates to the operation of the roller press 1 provided within the system according to Figure 1.

[0063] This roller press 1, which in the exemplary embodiment is designed as a compacting press and can alternatively also be designed as a briquetting press, is shown in simplified form in Figure 2. It has the already mentioned, counter-rotating press rollers 2, between which a roller gap W is formed. The roller surfaces of one or both press rollers 2 are provided with a profile. In the case of a compacting press, this is, for example, a corrugation. The starting material M is drawn between the two press rollers 2 into the gap W and there compacted into the aforementioned scab 3. The press rollers 2 are each cooled and consequently provided with a cooling device (not shown), which serves in particular to cool the surfaces of the rollers. This is because the starting material M is usually fed onto the roller press 1 in a hot state at high temperatures.In this case, the material M tends to adhere to the profiled surfaces, particularly due to the high temperatures, and consequently to melt onto them. These adhesions 7 are indicated in simplified form in the process diagram shown in Figure 3.

[0064]

[0065] This tendency towards melting is counteracted according to the invention. For this purpose, at least one parameter is continuously determined during operation which depends on the formation of caking 7 of the material M on the profiled roll surfaces. As a parameter, for example, a fluctuation value can be determined which is determined by measurement using a sensor 8 from fluctuations in a machine parameter, e.g. fluctuations in the gap width of the roll gap. With the help of the sensor 8, the gap width of the roll gap W and from this a fluctuation value can be determined. By monitoring this fluctuation value, the formation of melting can be detected and responded to. According to the invention, one or more operating parameters of the press are changed depending on the determined parameter, e.g. depending on the fluctuation value determined using the sensor 8, and thus caking 7 is reduced or removed.

[0066] In the illustrated embodiment, the pressure and consequently the pressing pressure P can be adjusted as operating parameters, depending on the determined characteristic and consequently depending on the detected fluctuations. This is indicated in Figure 3. After the formation of deposits 7 on the surface (process step A), these deposits 7 are detected directly or indirectly using the sensor 8 (process step B), and the pressing pressure P is then adjusted (process step C). This results in a reduction in the energy input and thus in a normalization of the roll surface (process step D). This, in turn, is detected via the sensor 8 by changing the characteristic and consequently the sensor signal for its measurement (process step E). The control device 9 reacts to this in the sense of regulation by increasing the operating parameter, namely the pressing pressure P, again (process step F).

[0067]

[0068] Figure 3 therefore shows a control strategy for dealing with caking on the rollers of a compacting press or briquetting press. The operating parameter(s) (e.g. the pressing pressure P) are changed by means of a control system in such a way that the deviation of an actual value of a parameter from the target value of the parameter is reduced. The pressing pressure P mentioned above can be used as an operating parameter. Alternatively or additionally, the variable cooling or a variable temperature T of the press rollers 2 can also be used as an operating parameter. This allows the cooling to be adjusted in response to the deviation of the actual value from the target value of the parameter and thus the surface temperature of the rollers can be changed and, in particular, reduced. By reducing the surface temperature, the caking is counteracted and the roller surface is cleared. As soon as this is detected, the temperature can be increased again.Alternatively, the feed temperature TA of the material M fed into the roller gap can also be used as an operating parameter. Furthermore, the rotational speed n of the press rollers can be used. Alternatively or additionally, it is possible to use the mass flow Ä of the supplied feed material as an operating parameter by adjusting the feed devices upstream of the roller gap (e.g., conveyor screws or belts, throttle valves or openings). Alternatively or additionally, it is also possible to use the return material fraction R and consequently the percentage of return material as an operating parameter.

[0069] The control strategy shown in Figure 3 can be implemented with the roller press shown in Figure 2. In Figure 2, in addition to the roller press 1 with the two press rollers 2, a detection device, e.g., a sensor 8 for detecting vibrations, is shown. The sensor can record an actual value I (e.g., for the fluctuation value). This is connected to a control device

[0070]

[0071] 9 (or a controller of a control device), which is supplied with a setpoint value S for, e.g., the fluctuation value and consequently the characteristic variable. The control device 9 or the controller detects a deviation between the setpoint value S and the actual value I and reacts by changing the operating parameter, e.g., the pressure P and / or the temperature T and / or the feed temperature TA and / or the speed n and / or the mass flow of the supplied starting material and / or the return material portion R.

[0072] For example, a press can initially be operated with a surface temperature T of 125 °C and a specified pressure P of 180 bar. If caking is detected, e.g., due to rising temperatures, the pressure can be reduced to 165 bar, for example, and the surface can be cleared. The pressure P can then be increased back to the initial value.

[0073] It may be advantageous to specify certain limits for the setting of the operating parameter (e.g. P and / or T) during the control process, so that, for example, arbitrarily low pressing pressures are not set to reduce caking. Consequently, the change in the operating parameter P or the operating parameters P, T, e.g. during the control process, can be made subject to the proviso that one or more specified maximum or minimum values ​​of the operating parameter or parameters are not exceeded or undercut. Consequently, limit values ​​are preferably defined in the control process. This applies not only to the operating parameters P and T given as examples, but also to the additional operating parameters TA, n, 111 and R or other possible operating parameters. Details are not shown in the figures.

Claims

Patent claims:

1. A method for operating a roller press (1) for compacting or briquetting material, wherein the roller press (1) has two counter-rotating press rollers (2), between which a roller gap (W) is formed and at least one of whose roller surfaces is provided with a profile, wherein the material (M) is pressed in the roller gap (W) between the roller surfaces to form a slug (3) or to form briquettes or a briquette strand, wherein the rollers (2) are preferably cooled during operation, characterized in that during operation at least one parameter is continuously determined which depends on the formation of caking (7) of the material (M) on the profiled roller surface or surfaces, and in that one or more operating parameters of the press are changed depending on the at least one determined parameter in order to reduce caking (7).

2. Method according to claim 1, characterized in that one or more operating parameters of the press are changed as a function of the at least one determined characteristic variable in such a way that caking (7) is reduced by reducing or increasing the characteristic variable or variables by changing the operating parameter or parameters.

3. Method according to claim 1 or 2, characterized in that the operating parameter or parameters are changed by means of a control such that a deviation of a determined actual value (I) of the characteristic or the characteristic variables from a target value (S) of the characteristic or the characteristic variables is reduced, in particular is minimized.

4. Method according to one of claims 1 to 3, characterized in that the change in the operating parameter or parameters, e.g. during control, is carried out with the proviso that one or more predetermined maximum values ​​or minimum values ​​of the operating parameter or parameters are not exceeded or undershot.

5. Method according to one of claims 1 to 4, characterized in that the press (1) is operated with a variable pressure (P) as an operating parameter and that the pressure (P) is changed as a function of the determined characteristic value, e.g. by a control system.

6. Method according to one of claims 1 to 5, characterized in that the press (1) is operated with a variable cooling and / or a variable (surface) temperature (T) and / or a variable feed temperature (TA) as operating parameters and that the cooling and / or the temperature (T) and / or the feed temperature (TA) is changed as a function of the determined characteristic variable, e.g. by a control system.

7. Method according to one of claims 1 to 6, characterized in that the press (1) is operated with a variable feed of the starting material, e.g. with a variable flow rate or mass flow of the supplied starting material as operating parameters and that the supplied material quantity or the flow rate or mass flow (™) of the supplied starting material is changed depending on the determined parameter, e.g. by a control system.

8. Method according to one of claims 1 to 7, characterized in that the press (1) is operated with a variable speed as an operating parameter and that the speed is changed as a function of the determined characteristic value, e.g. by a control system.

9. Method according to one of claims 1 to 8, characterized in that the characteristic variable, e.g. as an actual value (I), is determined directly by a measurement using a measuring device, e.g. a sensor (8).

10. Method according to claim 9, characterized in that a vibration value, e.g. as an actual value, is determined as a characteristic variable using a vibration sensor (8).

11. Method according to one of claims 1 to 8, characterized in that a fluctuation value is used as the characteristic variable, which is determined from fluctuations in a machine parameter, which are determined, for example, with one or more measuring devices.

12. Method according to claim 11, characterized in that the fluctuation value is determined from fluctuations in the gap width of the roll gap, fluctuations in the contact pressure of one press roll or both press rolls or fluctuations in the motor current or the motor torque of one drive or both drives of the press rolls, e.g. with one or more measuring devices which, e.g. with one or more sensors, record measured values ​​and determine a fluctuation value therefrom.

13. Method according to one of claims 1 to 8, characterized in that data is recorded by measurement using a measuring device, e.g., one or more sensors or a camera, and the characteristic value, e.g., as an actual value, is determined from these data using a computer.

14. A method according to any one of claims 1 to 13 for compacting inorganic material, in particular for producing fertilizer granules, wherein one or both roller surfaces are provided with a profile for producing a slurry.

15. A method according to any one of claims 1 to 13 for briquetting material, e.g., directly reduced iron, to produce briquettes (e.g., hot briquetted iron, HBI), wherein the roller surfaces are provided or equipped with briquetting tools having briquette troughs that form the profiled roller surface.

16. Roller press (1) for compacting or briquetting material, with two counter-rotating press rollers (2), between which a roller gap (W) is formed and one or both of whose roller surfaces is / are provided with a profile, and with a control device (9) for operating the roller press, characterized in that the control device (9) is set up to carry out the method according to one of claims 1 to 15.

17. Roller press according to claim 16, with at least one measuring device for determining the at least one characteristic variable.

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