EP0405518A2 - Milling surfaces for roller mills - Google Patents

Abstract

The invention relates to a grinding surface of roller mills and roller mills, and more particularly to the grinding surface of grinding rollers and a grinding track. Since the previous solutions for increasing the service life of the grinding surfaces are considered to be inadequate, ceramic segments (10) are now used as wear armor, which are also fixed to the base body or base shell (5) against dynamic stress forces.

Description

The invention relates to a grinding surface of grinding rollers and / or a grinding track in roller mills or roller mills according to the preamble of claim 1.

The aforementioned term of the grinding surface of roller or roller mills is understood below to mean in particular the mutually facing surfaces of the grinding roller or rollers and the grinding path of the rotating grinding bowl of a roller or roller mill, with the corresponding grinding gap between these facing grinding surfaces for comminuting materials such as Cement raw material, cement clinker, coal or the like is provided.

A grinding surface of the generic type is known from DE 26 43 307 A1. There, the grinding surface relates to a grinding roller, which, seen over its circumference, has armor elements made of a more wear-resistant material than the roller shell. These armor elements are positively inserted in dovetail-like grooves in the roller jacket and secured with flange rings on the axial faces. For this grinding surface, wear-resistant armor elements alternate with the softer material of the roll shell. These material differences ultimately lead to the fact that with such an off laying the grinding surface locally there is greater wear and tear even on the harder metal materials or the softer material on the grinding surface is more worn away, so that even loosening and possibly complete falling out of the form-fitting armor elements can occur.

The transition to increasingly harder alloys of ferrous materials for the grinding surfaces only brings about a relatively minor improvement in tool life in the range from 10 to about 20%. On the other hand, there are also limits to the oversizing of grinding rollers or the grinding path, since it had to be found that the controllability of oversized roller mills decreases towards the partial load range, so that in this direction only an uneconomical solution to the wear problem is seen.

It is known that ceramic materials have a significantly more favorable abrasion behavior than iron materials (DE-GM 87 08 401.5), which is why these materials have also been used for years to line static assemblies such as slides, cyclones and the like. However, considerable problems arise when using ceramic materials for assemblies that are predominantly exposed to dynamic loads.

While ceramic components have virtually no thermal expansion, the metallic assemblies, such as the base body or roller shell of a grinding roller, have a relatively high coefficient of thermal expansion, so that joining problems occur with such a combination of ceramic components and metallic components.
On the other hand, ceramic components are extremely sensitive to brittle fracture, which is why point loads, bending and torsion tensions must be kept from ceramic components. These components are also not designed for impact loads.

Based on these disadvantages, the invention is based on the object of designing a grinding surface of the generic type in such a way that longer service lives of the grinding surface but also simplification in terms of maintenance are achieved.

This object is achieved according to the invention in a generic grinding surface by the features of the characterizing part of claim 1.

The invention therefore proceeds to form the grinding surface from a segment-like armor, which consists of a much more wear-resistant material, namely a ceramic material, than the fastening body on which the segments are attached. This idea of the invention is, however, structurally supplemented by a largely form-fitting support of the segments, as a result of which the dynamic stress forces, such as circumferential, shear and shear forces, are absorbed by a corresponding form-fitting design of the fastening body of the segments. For this implementation, the outer surface of the fastening body is given a step-like contour in axial section, the individual steps forming cylindrical surfaces of different diameters in a grinding roller. This step-shaped contour can be provided in the case of a grinding roller on the base jacket, which is usually attached to the base body of the roller. However, it is also possible to fasten the individual segments directly onto a base body of the roller via the step-shaped contour.

Due to the step-like design of the base body or the base shell of a grinding roller, the thrust forces acting on the segments in the axial direction can be absorbed via the shoulders of the individual steps.

With regard to the absorption of tangential forces, that is to say forces in the circumferential direction of the grinding surface, parallel keys are provided between the base casing and the segments, which prevent displacement of the screwed-on ceramic segments in the circumferential direction. The feather keys are usually designed as metallic wedges or cuboids, which are inserted into corresponding grooves in the base casing, e.g. are screwed in and protrude about half of their vertical extension freely beyond the cylindrical bearing surface of the base jacket and can form a positive fit with recesses in the end faces of the segments in this area. The parallel keys can be assigned to the segments both individually and to a certain number of segments.

In addition or instead of the parallel keys, the segments can also be tangentially supported by corner areas of polygonal ring surfaces. This constructive solution to absorb dynamic forces in the tangential direction is based on the circular shape of a single cylinder surface, e.g. of the roll shell in radial section and replaces the circular arc with a straight line of the length of the corresponding ceramic element in the circumferential direction. At the transition from one straight line to the other, a step or shoulder is additionally formed, against which the corresponding ceramic segment is supported in order to absorb shear forces in the tangential direction. The surfaces of the ceramic segments which are adjacent to one another in the area of this step therefore have a different radial dimension, since the outer grinding surface has a circular contour.

Seen in axial section, the longitudinal edges of the steps in the base or base body of the grinding roller run essentially axially parallel to the axis of the grinding roller. These longitudinal edges preferably form an inclination angle in the range of approximately 5 ° to 45 °, preferably approximately 30 °, in relation to the grinding surface formed by the segments. The shoulders of the steps stand perpendicular to the longitudinal edges and are aligned so that the axial forces can be absorbed.

Known screw, weld and / or adhesive connections are used for the static fastening of the ceramic segments to the base jacket. Such an adhesive layer can expediently be used in the grinding surface according to the invention to compensate for unevenness between the ceramic segments and the outer surface of the steps. Due to the provided shoulders and feather keys, however, the screw fastenings provided for a static holder are kept free of shear, shear and bending forces. The insertion openings for the screw fastenings of the segments are closed flush with the rest of the grinding surface after the static fixing of the segments, which e.g. can be realized by inserting plugs. Slightly existing gaps between the joints of adjacent segments are compensated for with a suitable adhesive material.

To avoid point loads between segments of a grinding roller and segments of the grinding path of a roller mill, the distance between the rocker arms and the grinding bowl is mechanically limited by stop screws or stop buffers so that there is always a minimal roller gap and no direct contact between grinding surfaces.

A very similar concept of fastening the individual ceramic segments for the grinding surface of a grinding roller can also be implemented on the grinding path of the grinding plate. A corresponding grinding plate made of ferrous material is designed with a stepped surface in the radial direction. These circular steps then in turn receive ceramic segments, which in this case can have a block-like radial cut. The segments can also have step-like transitions on the grinding surface, for example in the range of 3 mm. However, an aligned transition of the segments is advantageously preferred for a flat grinding surface.

Due to the lower abrasion of the ceramic segments for the corresponding grinding surfaces, longer downtimes of the roller mill and thus a loss of production are prevented. The service life can therefore be improved by the fastening method of the segments compared to conventional, hardened, metallic wear armor, but also with regard to purely static fastening of ceramic linings.

Also with regard to maintenance measures on the wear parts of the grinding rollers or grinding track, there are advantages in that the ceramic grinding surface can be replaced in segments, whereas in the case of metallic wear jackets, but also with jacket segments, the use of heavy lifting devices was usually necessary. The construction of the grinding surfaces with ceramic segments therefore makes it easy to handle these segments, which are light in comparison to metal, so that a considerable reduction in service costs can be achieved.

In addition, a segmented, ceramic grinding surface enables the basic material of the roll shell to be made from cheap materials instead of expensive, hardened metal materials. The base body therefore remains attached to the base body of the grinding roller and is not affected by it even when the grinding surface is replaced. The ring-shaped segment and / or sector armoring of the grinding surfaces with ceramic material therefore leads to a cost reduction with regard to the wearing parts, the specific costs of e.g. DM / t / h in the range of about 40% of the previously applicable costs can be classified.

The invention therefore goes the way to use wear segments made of non-metallic materials, preferably highly wear-resistant ceramics, with the metallic base body or base shell in such a way that, in addition to the purely static holding function of the segments, those occurring during the comminution process between the grinding roller and grinding bowl dynamic forces can be absorbed without affecting the static holding elements.

• Fig. 1a einen Aufriß durch eine Wälzmühle mit Kennzeichnung der Mahlflächen;
• Fig. 1b einen Axialschnitt durch den Mantel einer Mahlwalze, ohne Grundkörper und Schwinghebel;
• Fig. 2 einen vergrößerten Ausschnitt des Basismantels im Axialschnitt mit entsprechender Mahlfläche;
• Fig. 3 eine bruchstückartige perspektivische Explosionszeich­nung einer Mahlfläche;
• Fig. 4a einen Teilausschnitt eines Radialschnittes durch das Beispiel nach Fig. 2 im Bereich der Stoßfuge der Seg­mente mit einer etwa achsparallel verlaufenden Paß­feder;
• Fig. 4b einen Radialschnitt entsprechend Fig. 4a mit polygona­ler Ringfläche an Stelle von Paßfedern;
• Fig. 4c eine Vergrößerung des Teilbereichs der polygonalen Ringfläche nach Fig. 4b im Bereich der Stufe;
• Fig. 5a eine perspektivische Ansicht einer Mahlschüssel mit Mahlplatte, deren Mahlfläche mit Keramiksegmenten aus­gelegt ist;
• Fig. 5b eine Draufsicht auf die Mahlschüssel nach Fig. 5a mit Teildarstellung der Anordnung der Keramiksegmente; und
• Fig. 5c einen bruchstückartigen Radialschnitt durch die Mahl­fläche der Mahlschüssel nach Fig. 5a.

The invention is explained in more detail below with the aid of schematic drawings. Show it:

• 1a shows an elevation through a roller mill with identification of the grinding surfaces;
• 1b shows an axial section through the jacket of a grinding roller, without a base body and rocker arm;
• 2 shows an enlarged section of the base jacket in axial section with a corresponding grinding surface;
• 3 is a fragmentary perspective exploded view of a grinding surface;
• 4a shows a partial section of a radial section through the example according to FIG. 2 in the region of the butt joint of the segments with a parallel key running approximately axially parallel;
• 4b shows a radial section corresponding to FIG. 4a with a polygonal ring surface instead of feather keys;
• 4c shows an enlargement of the partial area of the polygonal ring surface according to FIG. 4b in the area of the step;
• 5a shows a perspective view of a grinding bowl with a grinding plate, the grinding surface of which is lined with ceramic segments;
• 5b shows a plan view of the grinding bowl according to FIG. 5a with a partial representation of the arrangement of the ceramic segments; and
• 5c shows a fragmentary radial section through the grinding surface of the grinding bowl according to FIG. 5a.

In Fig. 1a, a roller mill 50 is shown schematically in elevation, which has an attached, integrated sifter 51. Above the grinding bowl 52 and its grinding path 53, grinding rollers 54 are arranged in the figure, which resiliently oppose the rocking lever 55 the regrind present on the grinding track can be pressed. The grinding bowl 52 is usually set in rotation via a gear. The streamlines with broken lines show the flow conditions of the air / dust mixture in the roller mill and the integrated classifier.

The area M is marked with a circle, which is decisive according to the invention with regard to the design of the grinding surfaces and is considered in more detail in the further exemplary embodiments.

In Fig. 1b an axial section through a grinding roller 1 is shown. The roller shell 4 is arranged on the base body, not shown, so that the grinding surface 3 comes to lie approximately parallel to the corresponding grinding surface of a grinding bowl. In the direction of the axis 2, the rocker arm for the grinding roller 1 would normally extend upward.

The lower section of the roll shell 4 is shown in FIG. 2 on an enlarged scale. The base jacket 5, which is usually made of an iron material, has, in the example, a plurality of steps 12 in the direction of the grinding surface 3, the transitions of which are designed as shoulders 13. While the longitudinal edges 32 of the steps 12 run approximately axially parallel to the axis 2, the shoulders 13 are approximately perpendicular to the axis 2.

Seen over the circumference of the grinding roller, the longitudinal edges 32 of the steps 12 form cylindrical surfaces which are covered with segments 10 made of a ceramic material. The angle of inclination α between the approximately horizontally provided grinding surface 3 and the longitudinal edge 32, which can be, for example, between 5 ° and 45 °, leads to segments 10 in the form of a truncated wedge.

With regard to their static support, the individual segments 10 are fixed by means of a screw 1.4 engaging through an opening on the side of the grinding surface at approximately a right angle to the axis 2 in the base casing 5. For additional static Fixing can also be provided between the base jacket 5 and the inner surface of the respective segment 10, an adhesive material that additionally creates a material balance between unevenness of the abutting surfaces.

Since this static support of the ceramic segments 10 is not sufficient for the dynamic loading of the grinding rollers, the left side flanks of the segments lie at least partially and possibly up to approximately 80% of their extension against shoulders 13 in order to be able to absorb forces directed axially to the left. The adjoining three rows of the segments 10 are bounded and fixed on the outside by an outer shoulder 20 and on the inside by an inner shoulder 19 of the base jacket 5.

In the perspective, fragmentary view according to FIG. 3, 12 pins 17 are indicated on the annular circumferential steps. These pins are intended for engagement in the openings 16 of the wedge-shaped segments 10. In these cases, the static mounting takes place via a nut 18, as shown in FIG. 4a. The opening 16 can be closed, for example, using a stopper 15 flush with the grinding surface 3.

The radial section through a roller shell according to FIG. 4a shows the design of the bond between segments and base shell 5 for absorbing forces in the circumferential or rotational direction D. For this purpose, the inner end faces 24 of the segments 10 have L-shaped areas in the region of their abutments or L-complementary recesses 27. A key 25, essentially cuboid in cross section, fitted into a U-shaped groove 30 of the base jacket 5 engages in this recess 27 of adjacent segments 10 largely in a form-fitting manner. The feather key 25, which in the example in the base jacket 5 is wider than in the segment region, therefore absorbs the tangential forces acting on the contact surfaces 26 and thus prevents shear and shear stress on the pins 17. The feather keys 25, which are usually made of a steel material, therefore block movement of the ceramic segments 10 in one or the other direction of travel of the roll shell.

The joint gap 31 formed between adjacent segments 10 at the joints 23 can be filled, for example, with ceramic adhesive 28, so that direct contact of the segments 10 with one another is prevented, but also a compensation is achieved on the grinding surface.

The feather keys 25 can expediently be present at the joints of two adjacent segments 10. However, it is also possible to assign a parallel key 25 of this type to a plurality of segments 10 for absorbing the tangential forces occurring thereon. An adhesive layer 22 which may be present at the interface 21 between the segment and the base jacket 5 can also serve to compensate for unevenness in the material.

FIG. 4b schematically shows a radial section through the cylinder surface of a grinding roller that is comparable to FIG. 4a. In this embodiment according to FIG. 4b, however, the tangential forces which act on the ceramic segments 10 are absorbed by means of an alternative construction. The circular cylindrical surface of the individual steps 12 according to FIG. 3 are formed in the example according to FIG. 4b by a polygon of individual straight lines 34, the latter forming a step 35 at the transition to the subsequent straight line 34 '. Since the radial height 36 'of the ceramic element 10 is kept larger than its radial height 36, the radially inner region 37 of the respective ceramic segment 10 is supported in the circumferential direction against the step 35, which can be incorporated directly into the support body 5. The feather keys according to FIG. 4a can therefore be replaced in a simple and advantageous manner by means of such a polygonal ring surface.

The ring structure of the ceramic segments 10 is therefore automatically secured against twisting in relation to the metallic base jacket by the double support against dynamic stresses in the axial and tangential direction. Such twisting of individual segments was previously conceivable in that when the roller shell and grinding bowl were paired, no pure rolling movement occurred over the entire shell width, if not by accident the axes of rotation of the roller shell and the grinding bowl in met at a point on the grinding track level. The interaction of feather keys 25 and shoulders 13 or the design as a polygonal ring surface 38 therefore allows the armoring of the grinding surface to be designed with ceramic segments 10 as well, with serious advantages compared to conventional roller jackets.

5a to 5c the further grinding surface 49, which is however now assigned to the grinding bowl 52, is shown schematically in more detail. The perspective view according to FIG. 5a initially shows a "spider web-shaped" arrangement of the individual segments 41 on the grinding plate 40. The segments 41 of the grinding surface 49 have a trapezoidal contour in plan view, as shown in FIG. 5b, the outer segments being larger Have polygon lines.

5c, the grinding bowl 52 receives a metallic grinding plate 40 in the sense of an insert. The surface of the grinding plate 40 itself is designed with step-like sections 43. The steps 43 go over shoulders 42 into the adjacent step. Ceramic segments 41 are positively fixed on these steps 43. This fixation is expediently carried out analogously to the fixation of the segments 10 on the base jacket 5. In the example according to FIG. 5c, the segments 41 have a square contour and lie positively against the shoulders 42 or longitudinal edges of the steps 43. The segments 41 go along in the radial direction of the grinding bowl slight protrusions 44 of, for example, 1 mm to 3 mm into the next segment 41. The grinding track surface 49 accordingly has a step-like contour. Depending on the requirements, flat grinding track surfaces with a continuous grinding surface transition from segment to segment can also be built.

The design of the grinding surface 3 of the grinding rollers, but also that of the grinding surface 49 of the grinding bowl with ceramic segments, therefore offers excellent wear protection, with the additional addition that maintenance measures can be carried out much more cost-effectively due to the segmentation and the lighter weight.

Claims (9)

1. grinding surface of grinding rollers and / or a grinding track in roller mills or roller mills,
with fastening bodies made of iron material or similar material,
wherein the grinding surface has a segment-like armor made of much more wear-resistant material than the fastening body, and
the segments are positively fixed,
characterized by
that the segments (10; 41) consist of a ceramic material or a ceramic compound,
that the outer surface of the segments (10; 41) forms the entire grinding surface (3; 49),
that for the form-fitting fixing of the segments (10; 41) against dynamic stress forces at least in the radial direction of the grinding track surface of the roller or roller mill, the surface of the fastening body (5; 40) facing the grinding surface (3; 49) of a grinding roller (1) or grinding plate ( 40) is stepped in axial section and the shoulders (13; 42 'of the steps (12.20; 43.42) support the segments (10; 41) of the armor. 2. Grinding surface according to claim 1
characterized by
that the longitudinal edge (32) of the respective step (12) forms an angle of inclination (α), in particular in the range from 5 ° to 45 ° with respect to the grinding surface (3). 3. grinding surface according to one of claims 1 or 2,
characterized by
that the segments (10; 41) at least in the area of their butt joints (31) are positively secured against dynamic tangential forces by corner areas (35) of a polygonal ring surface (38) and / or by feather keys (25). 4. grinding surface according to one of claims 1 to 3,
characterized by
that the segments (10; 41) with their inner surface (24) are non-positively fixed via a screw, weld and / or adhesive connection to the base jacket (5) or to the grinding plate (40). 5. grinding surface according to one of claims 1 to 4,
characterized by
that the segments (10; 41) and grinding rollers (1) form a plurality of polygonal ring bodies which, in axial section, produce adjacent cylindrical rings of different diameters with their inner surface. 6. grinding surface according to one of claims 1 to 5,
characterized by
that the fastening body (5) of a grinding roller (1) is the base body or a base jacket (5) of the grinding roller (1). 7. grinding surface according to one of claims 3 to 6,
characterized by
that the feather keys (25) are fixed in the fastening body (5) and largely engage in a form-fitting manner in the end-side recesses (27) of the segments (10). 8. grinding surface according to one of claims 1 to 7,
characterized by
that butt joints (31) between the segments (10) are filled with ceramic adhesive (28). 9. grinding surface according to one of claims 4 to 8,
characterized by
that openings (16) for screw connections in the segments (10) are encapsulated largely flush with the grinding surface (3).

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