CN110799269A

CN110799269A - Vertical roller mill

Info

Publication number: CN110799269A
Application number: CN201780091920.0A
Authority: CN
Inventors: 乔里·朗格尔; 保罗·奥托; 保罗·艾尔威尔斯; 安德烈·贝茨
Original assignee: Loesche GmbH
Current assignee: Loesche GmbH
Priority date: 2017-06-13
Filing date: 2017-06-13
Publication date: 2020-02-14
Also published as: AR112136A1; WO2018228675A1; EP3618964A1; JP2020523192A; DK3618964T3; JP6894986B2; EP3618964B1

Abstract

The invention relates to a vertical roller mill with a rotatable grinding bowl, on which a grinding bed consisting of grinding material is formed during operation. In addition, at least two stationary, rotatable grinding rollers are provided which, in operation, roll over the grinding material, wherein the grinding material is fed to the grinding rollers by rotation of the grinding bowl. According to the invention, a device for scraping off abrasive material is provided upstream of the respective grinding roller, which device is also used for removing a portion of the scraped-off abrasive material upstream of the grinding roller.

Description

Vertical roller mill

Technical Field

The invention relates to a vertical roller mill having a rotatable grinding bowl on which, in operation, a grinding bed for grinding material is formed, and having at least two immovable, rotatable grinding rollers which, in operation, roll on the grinding bed. The grinding material is fed to the grinding roller by rotating the grinding bowl about its center.

Background

In a typical vertical roller mill, the grinding material to be comminuted is usually fed from the center of the grinding bowl. By the rotation of the grinding bowl, the supplied grinding material is transported from the center of the grinding bowl to the edge of the grinding bowl and accelerated in the direction of rotation by the centrifugal force. The grinding material is accelerated by the peripheral speed (i.e. the rotational speed) of the grinding bowl. However, because this occurs by virtue of friction at the surface, the abrasive material does not reach the exact circumferential, or tangential, velocity of the grinding bowl at any location along the radius of the grinding bowl.

In a typical vertical roller mill, there are essentially three distinct streams of grinding material. They are here the flow of abrasive material of the newly supplied material, the flow of abrasive material of the rejected classifier particles, and the flow of abrasive material from the internal circulation.

New abrasive material refers to abrasive material that has just been introduced into the abrading process. Classifier particles refer to material rejected by a classifier in, for example, a roller mill with an integrated classifier. The two abrasive material flows can be fed onto the centre of the grinding bowl in a relatively aligned manner, ideally assuming that the rotation of the grinding bowl results in an even distribution over the grinding bowl. However, since there is usually no constant material flow in particular in the classifier particles and in the output of new grinding material, the grinding bed formed over the entire surface of the grinding bowl is not necessarily uniform.

In addition, the third flow of abrasive material formed by the internal circulation has to be taken into account. The internal circulation, in particular of a vertical roller mill operated in air circulation mode, refers to the material that is conveyed towards the classifier by being lifted by the primary air flow after falling onto the edge of the grinding table (instead of the material that is conveyed all the way to the classifier) falling back into the grinding bowl. Also falling into this category are: the abrasive material, which is transported directly away from the grinding table and deposited again, as a result of the circulating air flow or the turbulence present therein.

Since various devices (e.g., grinding rollers) exist in the vertical roller mill, various air flows and turbulences are generated, and thus it cannot be assumed at all that the material supplied to the grinding bowl is uniform.

The result of all this is that the grinding bed formed on the grinding bowl itself is uneven or inconsistent. This means that the height of the grinding bed, in particular, can vary considerably at various locations of the grinding bowl at different times. It should furthermore be taken into account that if the grinding bowl is provided with a raised grinding bowl edge, grinding material may intentionally accumulate to some extent at this edge and form an uphill or downhill slope which results in a greater height of the grinding bed.

For all these reasons, the grinding rollers cannot be provided with a uniform flow of grinding material with a uniform grinding bed, but have to be continuously adapted to various grinding bed heights by means of hydraulic damping.

Basically, three problems arise in this case.

Uneven introduction of abrasive material along the entire width of the grinding roll can lead to uneven wear of the grinding roll. This is especially the case where a retaining edge is provided where more material is present.

Another problem with non-uniform grinding beds is that the surface pressure varies across the width of the grinding roll and thus uniform and optimal grinding cannot be performed.

In addition, there is a problem that vibration is generated due to irregularities of the polishing bed during the polishing work. Above a certain level, these vibrations cannot be damped by the hydraulic spring, thereby limiting the maximum operating speed of the grinding bowl and thus its maximum rotational speed.

A number of approaches are known to partially address these problems.

An alternative is described, for example, in WO 2011/044966 a 1. In this case, an additional preparation roller is provided upstream of the actual grinding roller, which is used for pre-compressing the grinding material on the grinding bowl. The expected result is that a part of the air present in the grinding bed due to its loose packing can be removed from the grinding bed and, in addition, a more uniform grinding bed height can be obtained when entering the grinding gap between the actual grinding roller and the grinding bowl.

Another option for adjusting the height of the grinding bed is known from WO 2004/012693 a 1. In this case, a pusher which can be used to adjust the height of the grinding bed is provided in the region before the grinding roller. The pushers are driven onto or into the grinding bed at different heights, and material accumulates in front of these pushers. In this way, a grinding bed having a desired height or height distribution can be adjusted before the grinding roller.

Disclosure of Invention

It is therefore an object of the present invention to propose a vertical roller mill with a high operational smoothness.

According to the invention, this object is achieved by a vertical roller mill having the features of claim 1.

Advantageous embodiments of the invention are described in the dependent claims and in the description and the figures and the description of the figures.

In the case of the vertical roller mill according to the invention, an abrasive material scraping mechanism is provided before the individual grinding rollers in the direction of rotation of the grinding bowl. Each of these abrasive material scraping means is designed to remove a part of the abrasive material located on the grinding bowl from the grinding bowl before the respective grinding roller.

The basic idea behind the invention is the recognition that: overall, even if the grinding material is actively removed from the grinding bowl and is therefore not supplied to the grinding rollers for further grinding, a more efficient grinding or comminution can be achieved with lower energy consumption or higher productivity.

According to the invention, this can be achieved by: the abrasive material is actively removed from the grinding bowl by an abrasive material scraping mechanism. In contrast to the prior art, it is thereby possible that the abrasive material does not accumulate on the grinding bowl in any way or that the abrasive material is compacted as a result of compression. Thereby, a very uniform flow of abrasive material can be provided to the abrasive roll. Within the meaning of the present invention, "homogeneous" is understood to mean, in particular, a uniform abrasive height and a similar compression, i.e. the density of the abrasive on the grinding bed. In particular, similar densities can be achieved by an equivalent or similar precompression.

This uniformity allows the entire vertical roller mill system to operate at a higher production rate. This means in particular that the grinding bowl can be operated at a higher rotational speed than a vertical roller mill without abrasive material scraping means. The grinding roller can thus rotate faster and pulverize more ground material per unit time. Thus, the original contradiction is solved, i.e. higher productivity and higher efficiency can be obtained due to the active removal of grinding material from the grinding bowl. Furthermore, preventing or mitigating vibration allows the associated limitations on productivity and performance to be eliminated, or set to higher levels.

In principle, the abrasive material scraping means can be designed in any desired manner. However, it is preferable that the abrasive scraping mechanism includes a base plate and a scraper arranged on the base plate. It is advantageous if the base plate and/or the scraper are made of ceramic or carbide or, more precisely, they comprise the above-mentioned materials at particularly exposed portions in order to reduce wear due to scraping off the abrasive material or due to the abrasive material passing under the base plate.

The two-piece design has the advantage that the blade can be replaced separately, which wears more than the base plate. The provision of a squeegee on the substrate also provides the following advantages: in addition to the scraping action, the grinding bed can be made more stable. The abrasive material scraping means can likewise be of one-piece design, i.e. have one-piece base plates or one-piece scrapers.

In particular, an effective removal or diversion of the abrasive material from the grinding bowl can be achieved by providing the side of the abrasive material scraping means facing away from the grinding roller with a concave shape. In this case, the scraper can have, in particular, a plow shape. It has been shown that on the basis of this shape, grinding material can be removed effectively, or even cut off, and the entrained flow of grinding material can be removed easily from the grinding bowl. In addition, the wear caused by the forming process is relatively minimal by this shape compared to other shapes.

Advantageously, the abrasive material scraping means are designed such that the abrasive material to be removed is transported beyond the grinding bowl over the edge of the grinding bowl. If the grinding mill is operated in an air circulation mode, the grinding material removed from the grinding bowl in this way can be conveyed by the circulating air flow to the classifier; it can be returned to the grinding bowl as reject material by means of an internal or external grinding cycle; alternatively, it may be rejected as grit by the classifier and returned to the grinding bowl as such.

Pneumatic conveying back to the grinding bowl, for example together with or independently of the feed material, can also be used if the grinding mill is not operated in air circulation mode. Scraping and transporting excess abrasive material out of the grinding bowl has proven to be the most energy efficient method for removing the excess abrasive material.

Advantageously, the abrasive material scraping means are designed to cause the abrasive bed formed in front of the abrasive roll to have a uniform height and/or a uniform density (e.g. packing density) by removing abrasive material. Since a uniform grinding bed having a height as constant as possible is supplied, the grinding rollers can run more smoothly, and thus vibration in the grinding mill can be reduced. The type of uniformity of the grinding bed can be considered to depend on the exact shape of the grinding bowl and grinding roller. For example, if a conical grinding roller and a grinding bowl which is straight or flat in this region are used, the grinding bed formed should ideally be parallel to the surface of the grinding bowl. The situation is different if spherical grinding rollers are used, in which case the grinding track formed on the grinding bowl will generally be shaped accordingly.

In this case, it is important for the invention that the grinding bed has a constant height, or a substantially constant or uniform height. This feature can be understood as the abrasive material fed to the grinding roller having a height and/or density that is optimal for the grinding roller and its profile. This does not necessarily mean that it is uniform over the entire length or width of the grinding roller. Within the meaning of the present invention, the two terms "grinding table" and "grinding bowl" in connection with the roller mill can be considered as equivalent.

The height of the grinding bed after the grinding bed scraping mechanism can be any desired height. Advantageously, the aforementioned height before the grinding roller is larger than the grinding gap between the grinding roller and the grinding bowl, seen in the direction of rotation of the grinding bowl. That is, this ensures that there is sufficient material in the grinding gap to be comminuted by the grinding roller. This comminution is caused by the grinding rollers exerting pressure in the direction of the grinding bowl. If the height of the grinding bed before the grinding roller is only as high as the grinding gap, not enough grinding material can be ground. In this case, the difference between the bulk density before entry into the grinding gap and the maximum compressed density in the grinding gap is significant, wherein the height of the grinding bed before the grinding roll and the height of the grinding bed in the gap are proportional to their respective densities.

In this case, it is advantageous if the height of the abrasive material scraping device is designed to be adjustable. In this way the height of the mechanism above the grinding bowl is adjustable, whereby the height of the grinding bed can also be changed. The height at which the grinding material is fed to the grinding rollers can be varied depending on the grinding material to be ground and the exact design of the roller mill, whereby the respective process to be performed can be optimized.

The abrasive material scraping means may extend over a part of the width of the abrasive roll or over the entire width of the abrasive roll. Depending on the abrasive material to be comminuted and the shape of the grinding roller, it is advantageous if the abrasive material scraping off mechanism does not extend over the entire width of the grinding roller, so that a part of the grinding bed which has not yet become smooth is also provided at the grinding roller. In addition, this has the result that the complexity and the forces acting on the abrasive material scraping mechanism are reduced, which means that a less robust design is possible and thus wear can be reduced. A further advantage is achieved in that abrasive particles with a diameter larger than the distance between the abrasive scraping means and the grinding bowl can be fed into the area of the grinding roller not covered by the abrasive scraping means and comminuted by it.

In an advantageous embodiment the grinding bowl comprises a holding rim for holding grinding material transported from the centre of the grinding bowl towards the rim of the grinding bowl due to the rotation of the grinding bowl. In this case, it is preferred that the abrasive material scraping means extend from the holding edge of the grinding bowl along the width of the grinding roller towards the centre of the grinding bowl.

Due to the presence of the retaining edge, a slope of abrasive material is typically formed at the retaining edge which is significantly higher than the rest of the grinding bed. An abrasive material scraping mechanism may be used to clear such a ramp by removing the ramp from the grinding bowl. Given that it is significantly higher than the rest of the grinding bed, this particular slope can lead to uneven wear of the grinding rollers. Since the abrasive material scraping mechanism is able to clear the slope, the wear on the grinding roll will be more uniform over the entire width of the grinding roll. As to how it looks in vertical section, the appearance of the ramp should be reshaped from an imaginary triangle to an imaginary rectangle upon entering the grinding roll gap. As shown by experiments, the energy consumption for doing so can be significantly reduced by using a plough.

The abrasive material scraping means may be arranged at an angle relative to the rotation direction of the grinding bowl. In this case, the distance between the side of the abrasive material scraper means facing away from the grinding roller and the surface of the grinding bowl is preferably greater than the distance between the side of the abrasive material scraper means facing the grinding roller and the surface of the grinding bowl. In other words, the abrasive material scraping mechanism (and in particular its base plate) is angled relative to the grinding bed so that pre-compression can be performed. Pre-compression may be used substantially to remove air located in the grinding bed from the grinding bed so that the pre-compressed grinding bed may be provided to the grinding roller, thereby reducing vibrations and oscillations at the grinding roller that must be damped by its damping system. This makes it possible to run the roller mill more smoothly, so that the rotational speed of the grinding bowl can be increased further and the efficiency and productivity can be improved.

Advantageously, the abrasive material scraping means extends as far as possible into the grinding gap and even in the vertical projection plane of the grinding roller. This can be achieved in particular by the substrate extending as far as possible into the grinding gap, or almost as far as possible into the grinding gap. Since the abrasive material scraping mechanism or its base plate extends almost to the grinding gap, it can be ensured that a uniform grinding bed is fed to the grinding gap, and thus to the grinding roller, with a relatively high level of reliability. If the grinding bed is pre-compressed relatively far before the grinding roller, for example by using a preparation roller, as compared to this embodiment, the grinding bed may be disturbed when being transported from the pre-compressed position to the actual grinding roller, resulting in an unstable operation. In this connection, in order to keep the distance between the grinding gap and the abrasive material scraping means as small as possible, it is advantageous if the abrasive material scraping means extends appropriately in the vertical projection plane of the grinding roller on the grinding bowl.

The aeration of the grinding material can also be improved by providing fins on the bottom of the grinding material scraper, in particular on the base plate, which extend into the grinding bed, said fins extending substantially in the direction of rotation of the grinding bowl. These fins or protrusions form grooves on the grinding bed, which in this state are also ideally fed to the grinding rollers. Thereby, air escaping from the abrasive material in the grinding gap due to the pressure of the grinding roll acting on the grinding bowl is provided with a path through which the air can leave the abrasive material. The vertical roller mill can be operated more smoothly since no sudden mill bed aeration occurs but air can escape continuously, whereby the roller mill can be operated at higher speeds and thus with higher productivity.

It is known to provide water injection to counteract vibrations in the roller mill. Conventionally, for this purpose, water is sprayed to a position before the grinding roller on the grinding bed to increase the density and internal friction of the ground material, resulting in smoother running. Advantageously, in this context, nozzles can be provided on the bottom of the abrasive material scraping means, in particular on the base plate, in order to introduce fluid into the grinding bed. Vertical mills are also commonly used for drying. This means that the temperature in the grinding space is typically 90 ℃ or higher. When water injection is used, it is difficult to ensure that water is injected all the way onto or into the grinding bed. The embodiments presented herein differ in that water or other fluid is injected directly into the grinding bed. In addition, injection pressure can be used to affect the depth of penetration of the fluid, allowing a tighter and more easily comminuted grinding bed to be formed with lower water usage. Lower water usage is advantageous in terms of energy, since less water can have to be evaporated during mill drying.

Drawings

The invention will be explained in more detail below by means of exemplary embodiments and with reference to the drawings, in which:

fig. 1 shows a side view of an abrasive roll with an abrasive material scraping mechanism according to the invention;

FIG. 2 shows a view from direction II of FIG. 1;

fig. 3 shows a top view of a grinding roll with an abrasive material scraping mechanism according to the invention;

fig. 4 shows a side view of an abrasive roll with an abrasive material scraping mechanism according to the invention;

FIG. 5 shows a view in the direction V of FIG. 4;

fig. 6 shows a side view of a grinding roll with abrasive material scraping mechanism with water injection according to the invention; and is

Fig. 7 shows an enlarged view of the nozzle for water injection.

Detailed Description

Fig. 1 shows a schematic view of a grinding roll 4 on a grinding bowl 3, and also shows an abrasive material scraping mechanism 10 according to the invention.

The grinding bowl 3 rotates in the direction of rotation 8. The grinding bowl 3 is typically of circular design. The abrasive 20 is fed to the center of the grinding bowl, and the abrasive 20 is moved or conveyed outward by the rotation of the grinding bowl 3 or the centrifugal force generated thereby. Thereby, the grinding bed 20 is formed on the grinding bowl 3. By rotation of the grinding bowl 3, the grinding material 20 is fed to the grinding rollers 4 and is crushed at its grinding gap 5 by means of the pressure from the grinding rollers 4 and potentially additional pressure on the grinding rollers 4.

As shown in the figures, the grinding bed 20 is often not uniform in shape, in particular before the abrasive material scraping means 10 in the direction of rotation 8, according to the invention. This results in a large variation in the force acting on the grinding roller 4 over time as the grinding roller 4 rolls over the grinding bed 20. These forces can be partly damped by means of the damping system of the grinding roll 4, but above a certain intensity they also produce so-called "vibrations" of the grinding roll 4 or of the entire system, i.e. of a vertical grinding mill provided with a grinding bowl 3 with a plurality of grinding rolls 4. Once the vibration occurs, the rotation speed of the grinding bowl 3 cannot be further increased, and thus the productivity cannot be further increased.

In many embodiments, the grinding system is typically designed such that the grinding bowl has a constant rotational speed. Thus, the occurrence of vibrations represents an upper limit for the productivity and/or the fineness of the ground material. This means that a given system cannot reach the desired values, or that the productivity and/or fineness cannot be further increased. However, if the use of an abrasive material doctoring process may lead to reduced vibrations in the overall process, new equipment with higher grinding bowl rotational speeds and higher productivity may be planned and proposed.

Abrasive material scraping mechanisms 10 according to the present disclosure may be used to prevent or reduce vibration. The above-mentioned mechanism is located before the grinding roll 4 with respect to the direction of rotation 8 of the grinding bowl 3. In the embodiment shown here, the abrasive material scraping means 10 comprises two basic parts, which may have a two-piece design, but may also have an integrated design. First, a scraper 14 may be provided, which scraper 14 may remove or scrape off the grinding bed 20 from the pile of material that has built up over a height h₁The abrasive material 22. This is clearly shown in fig. 2, from which it is possible to obtain that the removed grinding material 23 is transported out of the grinding bowl 3.

Second, a base plate 12 is also provided, and a squeegee 14 is fixed to the base plate 12. The base plate 12 extends as far as possible towards the grinding gap 5 between the grinding roller 4 and the grinding bowl 3. The grinding gap 5 can be considered as the point or area where the distance between the grinding roll 4 and the grinding bowl is minimal.

The bottom of the base plate 12 can extend substantially parallel to the grinding bowl 3, whereby the abrasive material scraping means 10 can also extend substantially parallel to the grinding bowl 3. However, the abrasive material scraping device 10 can also be arranged slightly inclined such that the distance h between its side facing away from the grinding roller 4 and the upper surface of the grinding bowl 3₁More than the distance between its side facing the grinding roll 4 and the upper surface of the grinding bowl 3. In FIG. 1, the latter distance is referred to as h₂。

If the abrasive material scraping means 10 is arranged at an angle, i.e. at an angle α relative to a line parallel to the surface of the grinding bowl 3, the abrasive material 22 forming the grinding bed 20 can be pre-compressed slightly, which means in particular that ventilation is performed, ventilation is understood in this context to mean that air which is present in the grinding bed 20 due to loose packing of the abrasive material 22 is removed from the grinding bed 20 and causes the particles to be more densely packed, which in turn causes the force exerted on the grinding roll 4 to be more uniform, and thus a smoother operation.

As can be seen in particular from fig. 1, the scraper 14 has a plow-like design. This can be seen again in connection with fig. 2. In this case it has been found to be advantageous for the scraper 14 to have a concave shape which is preferably designed such that the above-mentioned shape is able to transport the already scraped-off grinding material 23 over the grinding bowl edge and out of the grinding bowl 3.

Although not clearly shown in fig. 1, the abrasive material scraping means is suspended in a flexible manner, so that the height h₁And height h₂Is adjustable. This is preferred because of the different heights h, depending on the production rate and abrasive material 22 used₁And h₂Is most preferred. However, it is essential in this context that the height h₂Is always greater than the height of the grinding gap 5, i.e. the height h₃. Otherwise, a reduction in the productivity of the abrasive material 22 results.

Further advantages of the abrasive material scraping mechanism 10 according to the invention will be explained in the following with reference to fig. 2, which fig. 2 shows a view from direction II in fig. 1.

In fig. 2, the retaining edge 6 can be seen at the edge of the grinding bowl 3. Abrasive material 22 moving outwards from the centre of the grinding bowl 3 towards the edge of the grinding bowl 3 accumulates at the edge and results in a ramp 25, also called abrasive wedge. In a similar manner, the ramp or upper ramp 25 is positioned towards the centre of the grinding bowl 3, since the material 22 is introduced there and is transported outwards towards the edge of the grinding bowl 3 only as a result of the rotation, thereby being dispersed.

As shown in fig. 2, abrasive scraping mechanism 10 begins near retaining edge 6. It is thus possible to clear the abrasive material wedge 25 at the retaining edge 6 and thereby remove deposits from the grinding bed 20, so that the most uniform and consistent grinding bed 20 as possible can be formed on which the grinding rollers 4 roll.

In addition, fig. 3, 4 and 5 illustrate another embodiment of an abrasive scraping mechanism 10 according to the present invention. Herein, fig. 3 shows a top view of the grinding roll 4. Fig. 4 shows a side view of a grinding roll 4 with an abrasive material scraping mechanism 10 according to the invention. Finally, the view in the direction of V in fig. 4 is shown in fig. 5.

In the embodiment shown here, a fin-like elevation 16 is provided on the bottom of the base plate 12, which is pressed into the grinding bed 20. These projections 16 are thus pressed into the air escape grooves 31 in the grinding bed 20. The purpose of these grooves is to allow air displaced by the grinding bed 20 compressed in the grinding gap 5 to escape. In this case, in order to prevent the air escape grooves 31 that are produced from being filled again with abrasive material 22, it is important that the abrasive material scraper means 10 or the fins 16 or fin-like projections are as close as possible to the grinding gap 5, but they end just before said gap in order to leave room for escaping air. In another embodiment, the fin-like protrusion 16 may also have a hollow interior with a channel that opens into the space above the base plate for selective venting of air.

Finally, fig. 6 and 7 show a further embodiment of an abrasive material scraping mechanism 10 according to the invention. In this case, a side view of the grinding roller 4 is shown again in fig. 6. Fig. 7 shows an enlarged view of the nozzle 25 for water injection provided in this embodiment.

Behind the scraper 14, one or more nozzles 35 are provided in the base plate 12, which nozzles communicate with a supply line 37. Fluid, in particular water, can be introduced directly into the grinding bed 20 via the supply line 37. This is particularly useful to further displace any remaining air and increase the density of the grinding bed. Water injection is a known means for preventing or reducing vibrations during operation of the vertical roller mill. An advantage of the embodiments shown herein is that by injecting water directly into the grinding bed 20, it is possible to ensure that water enters the grinding bed 20 without substantial loss.

Vertical roll mills are generally used for mill drying, in which case the temperature in the mill space is 90 ℃ or more. In this case, if water is simply sprayed or atomized, there is a fundamental problem in that it is not guaranteed that water can actually enter the grinding bed 20 and remain there. By injecting directly before the grinding gap 5, it is less likely that water has evaporated. A smaller amount of water is advantageous in terms of energy, since less water has to be evaporated during the mill drying process.

Also shown in the embodiment shown here is a protective ceramic layer 33 which serves to reduce wear on the base plate 12 and blade 14.

Therefore, a very smooth operation can be achieved using the vertical roller mill and the abrasive material scraping mechanism according to the present invention, thereby improving productivity.

Claims

1. A vertical grinder is provided with:

a rotatable grinding bowl (3) on which, in operation, a grinding bed (20) of grinding material (22) is formed, and

at least two immovable, rotatable grinding rollers (4) which, in operation, roll on a grinding bed (20),

wherein the grinding material (22) is fed to the grinding roller (4) by rotation of the grinding bowl (3),

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

an abrasive material scraping mechanism (10) is arranged in front of each grinding roller (4) relative to the rotation direction (8) of the grinding bowl (3), and

each abrasive material scraping device (10) is designed to remove a part of the abrasive material (22) located on the grinding bowl (3) from the grinding bowl (3) before the respective grinding roller (4).

2. The vertical roller mill according to claim 1, characterized in that the abrasive material scraping mechanism (10) comprises a base plate (12) and a scraper (14) provided on the base plate (12).

3. Vertical roller mill according to claim 1 or 2, characterized in that the side of the grinding material scraping means (10) facing away from the grinding roller (4) has a concave shape.

4. Vertical roller mill according to any of claims 1 to 3 characterized in that the abrasive material scraping means (10), in particular the scraper (14), has a plow shape.

5. Vertical roller mill according to any of claims 1 to 4, characterized in that the grinding material scraping means (10) are designed such that the grinding material (22) to be removed can be conveyed out of the grinding bowl (3) over the edge of the grinding bowl (3).

6. Vertical roller mill according to any of claims 1 to 5, characterized in that the grinding material scraping means (10) is designed to be formed with a uniform height (h) before the grinding roller (4) by removing grinding material (22)₂) The grinding bed (20).

7. Vertical roller mill according to any of claims 1 to 6, characterized by the grinding bed height (h) after the grinding material scraping means (10) in relation to the direction of rotation of the grinding bowl (3)₂) Is larger than the grinding roller (4) anda grinding gap (5) between the grinding bowls (3).

8. Vertical roller mill according to any of the claims 1 to 7, characterized in that the height of the grinding material scraping means (10) is designed to be adjustable, so that the height of the grinding material scraping means above the grinding bowl (3) can be set.

9. Vertical roller mill according to any of the claims 1 to 8 characterized in that the abrasive material scraping means (10) extends over a part of the width of the grinding roller (4) or over the entire width of the grinding roller (4).

10. Vertical roller mill according to any of the claims 1 to 9, characterized in that the grinding bowl comprises a holding edge (6).

11. Vertical roller mill according to any of the claims 1 to 10 characterized in that the abrasive material scraping means (10) extend from the holding edge (6) of the grinding bowl (3) along the width of the grinding roller (4) towards the centre of the grinding bowl (3).

12. Vertical roller mill according to any of claims 1 to 11, characterized in that the grinding material scraping means (10) is arranged at an angle relative to the direction of rotation (8) of the grinding bowl (3), the distance (h) between the side of the grinding material scraping means facing away from the grinding roller (4) and the grinding bowl (3)₁) Is larger than the distance between the grinding bowl (3) and the side of the grinding material scraping mechanism facing the grinding roller (4).

13. A vertical roller mill according to any one of claims 1 to 12, characterized in that the grinding material scraping means (10) is arranged to extend as far as possible towards the grinding gap (5) and in the vertical projection plane of the grinding roller (4).

14. Vertical roller mill according to any of the claims 1 to 13, characterized in that on the bottom surface of the grinding material scraping means (10), in particular on the base plate (12), fins (16) are provided which extend into the grinding bed (20), said fins extending substantially in the direction of rotation (8) of the grinding bowl (3).

15. Vertical roller mill according to any of the claims 1 to 14 characterized in that nozzles (35) are provided on the bottom surface of the abrasive material scraping means (10), especially on the base plate (12), to introduce fluid into the grinding bed (20).