EP3038819A1

EP3038819A1 - Method for forming molded bodies from a granular material, and corresponding roller press

Info

Publication number: EP3038819A1
Application number: EP14755353.1A
Authority: EP
Inventors: Hans-Werner Schröder; Ralf Wollenberg; Jens-Uwe Repke; Dietmar Trommer; Bastian Lehmann; Raimund Lange; Manfred Erken
Original assignee: RWE Power AG
Current assignee: RWE Power AG
Priority date: 2013-08-29
Filing date: 2014-08-21
Publication date: 2016-07-06
Also published as: DE102013109405A1; CN105473321B; AU2014314392A1; AU2014314392B2; WO2015028377A1; CN105473321A

Abstract

The invention relates to a method for forming molded bodies, wherein a feed flow of a granular material with a specifiable particle size distribution is fed to a roller press (1) with at least two rollers (2, 3) which rotate in opposite directions about a respective rotational axis (4), each of which comprises interacting recesses (13) for the pressing process, said rollers (2, 3) defining a roller gap (5) between each other. The roller press (1) is equipped with rigid rollers (2, 3). The design of the rigid rollers (2, 3) prevents a deflection of a loose roller due to the counter pressure of the granular material in the roller gap (5), thus leading to a consistent pressure in the roller gap (5). In this manner, molded bodies of a specifiable quality can be formed. In a preferred process, the feed flow of granular material to the rollers (2, 3) is kept at a constant level, for example by means of a constant rotational speed of the conveyor screw (9) as a result of a corresponding actuation of the conveyor screw drive (14) using the control unit (6). In particular, molded bodies can thus be produced in a high-pressure method without requiring an additional processing step after the agglomeration or the formation of the molded bodies. In particular, a drying process of the corresponding molded bodies, for example briquettes, can be omitted.

Description

Method of forming molded articles from a granular material and corresponding roller press

The subject matter of the present invention is a method for shaping shaped bodies, in which a granular material, which can consist of one or more substances, in particular at least comprising carbon, is shaped by a roll press into shaped bodies, and a corresponding roll press. A preferred field of application for the present invention is the production of shaped fuel bodies such as briquettes.

Roller presses are used in addition to other types of presses for the production of fuel moldings. There are different procedures. For example, roll presses are used for the pure shaping of the granular material, with a subsequent after-treatment, such as, for example, drying, strengthening the shaped bodies accordingly. Such a method is known for example from DE 199 613 25 C1.

Furthermore, a so-called high-pressure compression is discussed, in which the final strength of the shaped body is achieved by the occurring in the nip of the roller press between at least two rollers specific contact pressure. Roller presses usually have two rotatably mounted counter-rotating rollers, on the surface of which there are corresponding shapes or depressions. The granular material applied to the rolls is transported by the rotation into the nip where it is subjected to a pressure which leads to an agglomeration of the granular medium and thus to the formation of the shaped bodies. The strength of the formed body depends essentially on the spatial and temporal course of the pressure. From the prior art it is known to combine a hard roll with a Loswalze in a roll press. The back pressure of the Loswalze is built by means of external systems, such as hydraulic or gas pressure systems. It is advantageous that the corresponding pressure of these systems can be used as a control variable or controlled variable for the process. The disadvantage, however, is that it comes to avoiding the Loswalze and thus to a change in the nip due to the back pressure, which opposes the granular material of the compaction, so that an uneven pressure curve across the width of the roller and thus a spatially and temporally fluctuating shape body quality is achieved.

On this basis, the present invention has the object, at least partially overcome the known from the prior art disadvantages. This object is achieved with the features of the independent claims, the respective dependent claims are directed to advantageous developments.

The method according to the invention for shaping shaped bodies, in which a supply flow of granular material of a predefinable particle size distribution of a roll press is fed with at least two counter rotating about one axis of rotation rollers each with cooperating wells and optionally webs for pressing, wherein the rollers define a nip between them , characterized by the fact that the roller press is formed with rigid rollers.

The term rigid roller is understood here in particular that it is not a Loswalze, which is pressed for example by means of hydraulic or gas pressure systems against a hard roller. Rather, this is a system with two rigid, so firmly stored rollers through which Position and dimensions of a corresponding nip of preferably 0 mm [millimeter] is defined to 10 mm, more preferably from 1 mm to 2 mm. As a nip while the distance between the two rolls of a roll press is called, which sets as a minimum distance between the profile webs of both rolls on the line connecting the Walzenachsenmittelpunkte (especially in a system with a rigid and a Loswalze) or is set (especially in a System with two fixed rollers).

A procedure with a "zero mm gap" is advantageous if, for example, a binder-free high-pressure briquetting of materials with a grain size of less than 6/0 mm is to be carried out In the case of briquetting with the addition of binders and / or hot briquetting of, for example, sponge iron, the width of the nip is determined, inter alia, as a function of the predefinable press capacity, gap widths of approximately 10 mm being advantageously possible.

The use of two rigid rolls (rigid rolls) no longer causes the deflection of one of the rolls due to the backpressure, which the granular material opposes to compaction, so that spatially and, for specifiable durations, even constant contact pressure in the nip is achieved. With a uniform supply of the feed material, ie a uniform feed stream, and in particular a directed to a constant contact force process control so a uniform quality of the moldings can be achieved. Therefore, the inventive method allows the production of moldings with defined quality requirements, without causing the well-known from the prior art fluctuations in the quality of the moldings. In particular, can by the way of high-pressure agglomeration dimensionally stable Shaped bodies are formed without these need to be subjected to a further treatment step such as drying.

The bodies of the rollers are preferably covered with segments or bandages, in which a predefinable profiling is incorporated, which preferably forms successive depressions or depressions and smooth surfaces (webs) in the direction of rotation. A segment is here understood to mean an element which is screwed onto the body of the roller. Under a bandage is understood here an element which is shrunk onto the body of the roller. The troughs have the same shape on the preferred two rollers. The geometry of the troughs depends on the predeterminable piece size of the shaped bodies, which often depends on the possible utilization of the shaped bodies, on the diameter of the rolls and on the briquetting behavior of the materials. Preferably, a particle size distribution of the material to be pressed in the feed stream is predetermined by a corresponding parameter selection of an upstream grinding process. The axes of rotation of the rollers are preferably aligned parallel to one another in order to be able to define a uniform nip between the rollers. The rollers rotate in opposite directions with identical rotational frequency and are designed in such a way that during rotation in the nip two depressions or a depression and a smooth surface (web) face each other. By the inside and at the edge of the two respective opposite troughs or the opposite trough and smooth surface resulting pressure leads to a compression of the granular material, in which a dimensionally stable shaped body, a so-called compact, is formed. Thus, in particular under high pressure, for example in the range from 80 to 160 MPa [Megapascal], high-pressure agglomeration, for example of shaped fuel bodies, can be achieved. According to a preferred embodiment, the granular material consists at least partially of a fuel, in particular of a coal.

The process according to the invention can be used particularly advantageously for shaping, preferably for high-pressure pressing, of shaped articles of fuel. These shaped fuel bodies consist at least partially preferably of coal, in particular lignite. Other fuels and additives are possible according to the invention. By way of example, further fuels or organic substances, such as, for example, wood chips, straw or the like, and additives, such as, for example, lime, can be added. Furthermore, it is inventively possible to improve the Brikettierverhalten of the granular material by a Brikettierhilfsstoff such as starch and / or a certain amount of water is supplied. According to a further advantageous embodiment, the feed stream is kept constant.

This means, in particular, that the feed flow of granular material into a press chamber, which is located above the rollers, is kept constant. This can be achieved, for example, by the speed of this plug screw being kept constant when using, for example, a plug screw for feeding the feed stream of granular material. A constant supply current allows easy control and regulation of the process, for example via the speed of the at least one roller. Preferably, two rollers are formed, which rotate synchronously with the same rotational frequency.

According to an advantageous embodiment, the rotational speed of at least one roller is dependent on at least one of the following variables:

a) the contact pressure of the rollers and b) the contact pressure of the rollers

regulated.

In particular, when there is a constant supply of granular material, the process according to the invention can thus be carried out in a simple manner. The maximum contact pressure or the maximum contact pressure of the rollers on the granular material or material to be compacted as it passes through the nip can be measured in a simple manner with a force sensor and / or a pressure sensor. Here are preferably used as a force sensor for measuring the contact pressure strain gauges, which are attached for example to a frame of the press. As a pressure sensor is preferably a pressure cell is used, in particular based on a capacitive measuring principle pressure cell, which is advantageously installed between the bearing of the axes of the rollers and the frame of the press. Also preferred is alternatively or additionally an embodiment in which at least one force or pressure sensor is formed in the wells for measuring the maximum pressure or the maximum force, which is set directly in the wells during the pressing of the granular material. Also, the force or pressure values in the nip can be used advantageously for controlling the roll speed.

According to a further advantageous embodiment, the feed stream is continuously conveyed. This can be achieved in particular by means of a corresponding conveying means, such as a stuffing screw. Due to the continuous promotion of a consistent quality of the molded body can be ensured, at the same time a simple control or control of the process is possible. Further preferred in this context is that the granular material is compressed in the feed stream.

Basically, the procedure should be chosen so that the granular material is compacted but not already briquetted in the feed stream. The compression can be carried out in particular when the granular material is fed into a pressing chamber upstream of the rolls. Such compression can be achieved in particular by means of a corresponding conveying means. The densification of the granular material in the feed stream leads to a congruence of the feed stream, ie to a more uniform material feed, and thus to a more uniform loading of the rolls with the corresponding troughs with the feed stream. This results in a homogenization of the quality of the molded body produced. According to a further aspect of the present invention, a roll press is proposed for shaping shaped bodies, which comprises at least a first roll and a second roll, which respectively have cooperating depressions and optionally webs for shaping the shaped bodies, wherein the rolls are each rotatable about an axis of rotation, which are aligned parallel to each other, wherein the rollers are rigid and define a nip between them, further comprising a control unit suitable and intended for carrying out the method according to the invention.

According to an advantageous embodiment, the roller press further comprises at least one of the following probes:

a) a pressure sensor and

b) a force sensor

for measuring at least one of the following sizes acting on the material to be pressed in the nip: a) the pressure and

b) the force.

The measurement of the pressure and / or the force in the nip, ie the contact pressure and / or the contact pressure of the rollers, that is to say the contact pressure and / or the contact pressure on the entire product to be pressed in the intake wedge of the rollers, constitutes a simple controlled variable, by means of which inventive method and thus the roller press can be controlled. It is thus possible, for example, to use the pressure and / or force values for regulating the roller speed for a given supply flow, that is to say for a prescribable mass flow of granular medium into the roller press. The contact force can preferably be measured with strain gauges, the contact pressure preferably with a pressure cell, which can be formed for example between the bearing of the axis of a roller and a frame of the roller press. Alternatively or additionally, it is advantageous to carry out a force and / or pressure measurement in the mold cavities for shaping the moldings, the results of which can alternatively or additionally be used as a controlled variable for controlling the rolling speed. According to a further advantageous embodiment of the roller press this has a conveying means for continuously conveying granular material to the rollers. In this connection, it is particularly preferred if at the same time a compacting means for compacting the granular material is formed during the conveying or the conveying means causes a compression of the material in addition to conveying.

In particular, the conveying means and the compression means may be a so-called plug screw, through which a simultaneous continuous che promotion with a simultaneous compression of the granular material is possible.

Furthermore, a roll press is proposed for shaping moldings, at least comprising a first roller and a second roller, wherein the rollers are each rotatable about an axis of rotation, which are aligned parallel to each other, wherein in opposite directions rotation of the rollers, a granular material between the rollers Moldings is characterized in that the rollers each have a cylindrical surface with depressions and webs which are distributed on the cylindrical surfaces, that in an opposite rotation of the rollers with the same rotational frequency in each case a trough on a roll with a ridge on the respective another roller cooperates to form a shaped body. This roller press is preferably a development of the roller press described above, but this can also be realized independently of the features described above as essential to the invention and characterizing. The corresponding roller press allows advantageously the production of semi-cushioned or half-drop shaped moldings as compacts by high-pressure compression. A corresponding roller press and the corresponding use of such for the production of fuel moldings, in particular of briquettes, without further processing steps such as after treatment would be necessary after the compression. By the described embodiment, in each case a trough cooperating with a web, a force and pressure curve in the compact is advantageously achieved, which allows a corresponding compression to a dimensionally stable shaped fuel body. According to an advantageous embodiment, the at least one trough has a contour which has an inlet curvature and an outlet curvature with different radii of curvature in the direction of rotation. According to an advantageous embodiment, at least one trough is shaped so that a bottom of the trough is inclined to a normal plane to a radius.

The bottom of a trough is understood to be the region which corresponds to a longitudinal side of the corresponding shaped fuel body. A normal plane is understood here to mean a plane to which the radius is normal, that is to say orthogonal. The radius is at least one radius in the region of the depression, in particular a radius in a center of the depression, that is to say a region of the depression which is equidistant from the inlet and outlet bulges in the direction of rotation.

According to an advantageous embodiment of the ground with the normal plane forms an angle of 10 ° and less, especially in a central region of the soil. The central region is understood in particular to mean an area that lies within the, that is, between the edge curvatures.

As a result of the different radii of curvature and / or the inclination of the base to the normal plane of the radius, in particular by 10 ° or less, it is advantageously possible to achieve an easier release or release of the shaped fuel from the trough in operation of the roll press. In particular, by the combination of the different radii of curvature of the inlet and the outlet curvature of the trough and the inclination of the bottom of the trough to the normal plane during the rotational movement of the press roll a force directed tangential to the rotational direction of the press roll testifies, which advantageously reaches a triggering of the fuel molding from the trough.

According to an advantageous embodiment, the troughs are part of segments or bandages that form the cylindrical surface.

A segment is here understood to mean an element which is screwed onto the body of the roller. Under a bandage is understood here an element which is shrunk onto the body of the roller. The formation of the depressions by segments and / or bandages allows a simple construction of the roller press and in particular a simple repair of the roller press in case of wear by replacing the damaged segments and / or bandages. The details and advantages disclosed for the method according to the invention are transferable and applicable to the roll press according to the invention and vice versa. The features listed individually in the claims can be combined with each other in any technologically meaningful manner and can be supplemented by explanatory facts from the description and from the figures, wherein further embodiments of the invention are shown.

The invention and the technical environment will be explained in more detail with reference to FIGS. The figures show particularly preferred embodiments, to which the invention is not limited. In particular, it should be noted that the figures and in particular the magnitudes shown are only schematically. Show it:

1 shows an example of a roller press, Fig. 2 to 3: perspective views of a first type of trough;

Figs. 4 to 5 are perspective views of a second example of a trough;

and

6 to 7 are sectional views of another example of a trough.

Fig. 1 shows schematically a roller press 1 with a first roller 2 and a second roller 3. The rollers 2, 3 rotate in opposite directions about each axis of rotation 4, as indicated by the arrows. The axes of rotation 4 are aligned parallel to each other. The rollers 2, 3 are rigid, that is, they are designed so that a translational movement of the rollers 2, 3 or the axes of rotation 4 is prevented at least in a predetermined range, in particular a predetermined range of contact forces of the rollers 2, 3. Only one rotation about the axes of rotation 4 (as shown by the corresponding arrows) is possible. The rollers 2, 3 define between them a nip 5 on the connecting line of the rotating tabs 4 of the rollers 2, 3. This nip 5 is shown exaggerated in this only schematic drawing for explanation. Preference is given to nips 5 of a size of 0 mm to 10 mm. In the case of binder-free high-pressure briquetting of materials with a crowning of 6/0 mm to 0.5 / 0 mm and even finer grain size a "zero mm-gap" operation is advantageous, the nip between the rollers 2, 3 to a predetermined Safety distance is set, which is preferably in the range of 1 mm to 2 mm.

Furthermore, the roller press 1 comprises a control unit 6, which is connected via corresponding data lines 7, inter alia with the drives of the rollers 2, 3. This control unit 6 is suitable and intended to carry out the method according to the invention and to apply the corresponding components accordingly. Taxes. Via a further data line 7, the control unit 6 is connected to a pressure sensor 8, with which the pressure of the material in the nip 5 can be measured. Furthermore, a force sensor 17 is formed. This is designed as a strain gauge.

Furthermore, the roller press 1 comprises a plug screw 9, which simultaneously serves as a conveyor 10 for the continuous promotion of granular material to the rollers 2, 3 and as a compression means 11 for the compression of the granular material in the promotion. As a result, a feed stream of granular material, not shown here, is continuously and compactly fed to a press chamber 18 above the rolls 2, 3. The plug screw 9 has a plug screw drive 14, which is also connected via a data line 7 to the control unit 6. The granular material is fed to the plug screw 9 via an addition unit 20.

The rollers 2, 3 each have cylindrical surfaces 12 which have troughs 13 on the outside. These troughs 13 are formed for example by screwed-on segments 16 or shrunk bandages. Examples of wells 13 formed by segments 16 are shown in FIGS. 2-5.

In Fig. 2 and 3, a first example of such segments 16 is shown with troughs 13, which represent in cooperation with a corresponding segment 16 on the respective other roller 2, 3 of the roller press 1, a negative mold of the corresponding shaped body as Halbmuldenpressling. The respective segments 16 have troughs 13 in alternation with webs 15. Here, in each case a segment 16, for example the segment 16 shown in FIG. 2, is formed on the first roller 2, while the second segment 16, shown for example in FIG. 3, is formed on the second roller 3. The distribution of the segments 16 on the cylindrical surface 12 of the rollers 2, 3 and the geometry of wells 13 and Webs 15 is chosen so that upon rotation of the first roller 2 and the second roller 3 at the same speed and a correspondingly defined starting position these wells 13 on the two rollers 2, 3 cooperate so that in the nip 5 each have a trough 13 and a ridge 15 opposite and thus a high-pressure pressing of the granular material to the moldings, here in Halbmuldenform takes place. The wells 13 are designed so that a corresponding pressure profile during rotation of the rollers 2, 3 is achieved, which leads to agglomeration and compression of the granular material to the molding. The cylindrical surface 12 can have a multiplicity of depressions 13, which are separated from one another by corresponding webs 15. In particular, over a width of the cylindrical surface 12, a plurality of wells 13 may be formed, so that with a corresponding roller press 1, a plurality of moldings can be formed simultaneously. The granular material can be warmed up before being added to the plug screw, for example by means of steam at a comparatively high temperature, for example in a so-called warm-up bunker. The warming up of the granular material can be assisted by blowing in steam, preferably when filling the tamping screw 9. To this end, vaporization units 19 are formed

4 and 5 show a second example of segments 16 with troughs 13 which are each formed opposite and cooperatively on the cylindrical surface 12 of the first roller 2 and the second roller 3 as in the first example.

The troughs 13 according to FIGS. 2 to 5 can each be part of segments 16 which are applied to the cylinder surface 12 or from which the cylinder surface 12 is formed. Alternatively or additionally, the troughs 13 may be part of bandages which are shrunk onto the cylindrical surface 12. Figures 6 and 7 show another example of segments 16 with troughs 13 for use on rollers 2, 3 in mutually perpendicular sections. The troughs 13 each have a bottom 21, which corresponds to a longitudinal side of the fuel molding. The bottom 21 is part of a contour 22 of the trough 13th

Fig. 6 shows a first section through a segment 16, while Fig. 7 shows a perpendicular section. The segment 16 is mounted on a roller (not shown) 2, 3 and rotates in the direction of rotation 28, as shown in both FIGS. 6 and 7. In the transverse direction to the direction of rotation 28 (see FIG. 6), the contour 22 has two lateral curvatures 29, which have an identical radius of curvature 25, which is indicated here by an arrow in each case. In addition, the bottom 21 is aligned perpendicular to the rotation direction 28 parallel to a normal plane 26 of a radius 27.

Fig. 7 shows a section perpendicular to the section shown in Fig. 6. In the direction of rotation 28 of the bottom 21 is inclined to the normal plane 26 of the radius 27 in the direction of rotation 28 considered center 30, ie the area in the direction of rotation 28 equidistant from an inlet curvature 23 and the extremal point 31 as an outlet curvature 24 and the extremal point 31 is. In addition, the inlet camber 23 has a first radius of curvature 32 and the outlet camber 24 has a second radius of curvature 33, which are not identical. The combination of the slope of the bottom 21 causes in the direction of rotation 28 after pressing a force tangential to the direction of rotation 28 generated, which promotes a trigger release of the pressed shaped fuel body. Thus, the fuel moldings can be solved in a simple manner from the wells 13.

In the examples of depressions 13 shown in FIGS. 2 to 7, these are preferably designed such that they are distributed on the cylindrical surfaces 12 such that in an opposite rotation of the rollers 2, 3 with the same rotational frequency in each case a trough 13 on a roller 2, 3 with a web 15 on the other roller 3, 2 cooperates to form a shaped body by the formation of rigid rollers 2, 3 does not occur to avoid a Loswalze by the back pressure of the granular material in the nip 5 and thus to a constant pressure in the nip 5. As a result, moldings of a predetermined quality can be formed. Preference is given to a process control in which the supply flow of granular material to the rollers 2, 3 is kept constant, for example by a constant speed of the screw conveyor 9 by a corresponding control of the plug screw drive 14 by the control unit 6. By using the stuffing screw 9 takes place a promotion of the granular material to the rollers 2, 3 with simultaneous compression and compression thereof. The control of the method is effected in that due to the constant supply current and the constant nip, the speed of the first roller 2 and the second roller 3 in dependence on the contact pressure of the rollers 2, 3 is controlled. The contact pressure is thereby obtained in a simple manner on the basis of the measured values of the pressure sensor 8 and / or of the force sensor 17. Thus, a simple control of the method can take place, the production of molded articles with defined quality parameters is thus possible. In particular, moldings can be produced in a high-pressure process without having to carry out a further processing step after the agglomeration or molding of the moldings. In particular, can be dispensed with a drying of the corresponding moldings, such as briquettes. LIST OF REFERENCE NUMBERS

1 roller press

2 first roller

3 second roller

4 rotation axis

5 nip

6 control unit

7 data line

8 pressure sensor

9 plug screw

10 subsidies

11 compaction means

12 cylindrical surface

13 trough

14 plug screw drive

15 footbridge

16 segment

17 force sensor

18 pressing chamber

19 evaporation unit

20 addition unit

21 floor

22 contour

23 inlet curvature

24 outlet curvature

25 radius of curvature

26 normal level radius

Rotation direction lateral curvature center

Extremal point first radius of curvature second radius of curvature

Claims

claims

1. A method for shaping moldings, wherein a feed of granular material of a predetermined particle size distribution of a roll press with at least two oppositely rotating about one axis of rotation rollers is fed in each case with cooperating troughs and optionally webs for pressing, wherein the rollers define a nip between them , characterized in that the roller press is formed with rigid rollers.

2. The method of claim 1, wherein the granular material consists at least partially of a fuel, in particular of a coal. 3. The method according to any one of the preceding claims, wherein the feed stream is kept constant.

4. The method according to any one of the preceding claims, wherein the speed of at least one roller in dependence on at least one of the following sizes:

a) the contact pressure of the rollers and

b) the contact pressure of the rollers

is regulated. 5. The method according to any one of the preceding claims, wherein the feed stream is conveyed continuously.

6. The method of claim 5, wherein the granular material is compressed in the feed stream. Roller press (1) for shaping shaped bodies, at least comprising a first roller (2) and a second roller (3), each having cooperating recesses (13) and optionally webs (15) for shaping the shaped bodies, wherein the rollers (2, 3) each about an axis of rotation (4) are rotatable, which are aligned parallel to each other, wherein the rollers (2, 3) are rigid and define a nip (5) between them, further comprising a control unit (6) suitable and intended for Implementation of the method according to one of the preceding claims.

Roller press (1) according to claim 7, further comprising at least one of the following probes:

a) a pressure sensor (8) and

b) a force sensor

for measuring at least one of the following sizes acting on the material to be pressed in the nip:

a) the pressure and

b) the force.

9. roll press (1) according to any one of claims 7 or 8, comprising a conveying means (10) for the continuous conveying of granular material to the rollers (2, 3).

Roller press (1) according to claim 9, having a compaction means (11) compaction of the granular material during the conveyance.

11. roll press (1) for shaping shaped bodies, in particular according to one of claims 7 to 10, at least comprising a first roller (2) and a second roller (3), wherein the rollers (2, 3) are each rotatable about a rotation axis (4) which are aligned parallel to each other, whereby, when the rollers (2, 3) rotate in opposite directions, a granular material exists between the rollers (2, 3) can be pressed into shaped bodies, characterized in that the rollers (2, 3) each have a cylindrical surface (12) with depressions (13) and webs (15) which are thus distributed on the cylindrical surfaces (12), that in opposite directions rotation of the rollers (2 3) with the same rotational frequency in each case a trough (13) on a roller (2, 3) with a web (15) on the respective other roller (3, 2) cooperates to form a shaped body.

Roll press (1) according to claim 11, wherein the at least one trough (13) has a contour which has an inlet curvature and an outlet curvature with different radii of curvature in the direction of rotation.

A roller press (1) according to any one of claims 11 to 12, wherein at least one trough (13) is formed so that a bottom of the trough (13) is inclined to a normal plane to a radius.

A roller press (1) according to claim 13, wherein the bottom of the normal plane is at an angle of 10 ° and less.

Roller press (1) according to one of claims 7 to 14, in which the troughs (13) are part of segments (16) or bandages forming the cylindrical surface (12).