AU2018264756B2

AU2018264756B2 - Roller mill and method for operating a roller mill

Info

Publication number: AU2018264756B2
Application number: AU2018264756A
Authority: AU
Inventors: Frank Schroers
Original assignee: FLSmidth AS
Current assignee: FLSmidth AS
Priority date: 2017-05-11
Filing date: 2018-04-05
Publication date: 2021-09-30
Anticipated expiration: 2038-04-05
Also published as: PE20200043A1; FI3621742T3; BR112019023541A2; DE102017208014A1; ZA201908218B; EP3621742A1; EP3621742B1; WO2018206200A1; AU2018264756A1; CL2019003207A1; DK3621742T3

Abstract

The invention relates to a roller mill (10) for comminuting a granular material, having a first mill roller (12) and a second mill roller (14) which are arranged opposite each other and can be driven in opposite directions. A mill gap (16) is formed between the mill rollers (12, 14), and at least one of the mill rollers (12, 14) has an edge element (18, 20) at an end region (22, 24, 26, 28) of the mill roller (12, 14), said edge element being designed such that the edge element extends over the mill gap (16) and at least partly covers the end face of the opposing mill roller (12, 14). A scraping element (42, 44) for at least partly removing material is arranged on the end region (22, 24, 26, 28) of the mill roller (12, 14) that is provided with an edge element (18, 20). The invention also relates to a method for operating a roller mill (10), said method having at least the step of: at least partly removing material from an end region of a mill roller (12, 14).

Description

Roller mill and method for operating a roller mill

1. FIELD OF THE INVENTION The invention relates to a roller mill having peripheral elements for comminuting granular material, and to a method for operating a roller mill.

2. BACKGROUND OF THE INVENTION Roller mills are typically used for comminuting ground material such as, for example, limestone, clinker, or similar rocks. In the comminution of ground material in a roller mill it arises that ground material exits the milling gap laterally without having completely or at all passed the milling gap. This leads to a reduction of the throughput rate of the machine and to an increase in the grinding revolutions, which is associated with an enormous input of energy.

In orderforthe lateral outflow of ground material from a milling gap configured between the grinding rollers of a roller mill to be influenced in a controlled manner it is known for peripheral elements to be disposed on one of the grinding rollers. Such a roller mill having peripheral elements is known from utility model DE 20 2014 006 837 U1, for example. An increased specific grinding pressure acts on the peripheral elements, said increased specific grinding pressure leading to high stress on the peripheral elements and thus often leading to wear or breakage on the peripheral elements.

Against this background, it would be advantageous to provide a roller mill having peripheral elements, wherein the peripheral elements are subjected to less stress and wear.

3. SUMMARY OF THE INVENTION A roller mill for comminuting granular material according to a first aspect of the invention comprises a first grinding roller and a second grinding roller disposed opposite one another and drivable in a counter-rotating manner, wherein a milling gap is configured between the opposing grinding rollers. At least one of the grinding rollers comprises a peripheral element at an end region of a grinding roller end, which is configured in such a manner that said peripheral element extends across the milling gap and at least partially covers an end side of the opposite grinding roller.

In accordance with the first aspect, a scraping element for at least partially removing material is attached to a stationary roller frame and disposed to be stationary relative to the grinding rollers and locate over the end region of the grinding roller that is provided with the peripheral element. The scraping element serves in particular for at least partially removing material that has accumulated on the end region of the grinding roller. The material is scraped by the scraping element in the operation of the roller mill, wherein the grinding rollers rotate in a counter-rotating manner. The scraping element is preferably disposed on the end region of the grinding roller in such a manner that said scraping element does not contact the grinding roller. The end region of the grinding roller comprises, for example, the end side of the grinding roller, the grinding roller surface adjacent thereto, as well as a region which surrounds the grinding roller surface and in which material accumulates. For example, such a region comprises a height of more than or equal to 1.5 mm to 3 mm, in particular more than or equal to 2 mm to 5 mm, preferably 4 mm.

The peripheral element comprises in particular an encircling circular ring, preferably a circular disk. The peripheral element is in particular attached to the end side of the respective grinding roller, for example screw-fitted or welded thereto.

An end-side gap is in each case preferably configured between the peripheral elements and the end side of the respective opposite grinding roller. An end-side gap prevents a collision between the peripheral element and the end region of the respective opposite grinding roller in the event of the grinding rollers running off track in which the opposing grinding rollers are no longer mutually parallel.

The grinding rollers comprise in particular a roller main body, wherein the peripheral element is releasably connected to the roller main body of the respective grinding roller. The grinding roller preferably comprises a drive shaft for driving the grinding roller, the roller main body being disposed on said drive shaft. A releasable disposal of the peripheral elements on the roller main body offers the advantage of a rapid and simple replacement of the peripheral elements in the event of wear. The peripheral elements are adhesively bonded, soldered/brazed, welded, or screw-fitted to the roller main body, for example, and preferably comprise a wear-protection feature. The wear protection feature is in particular disposed on the internal face of the peripheral element that points in the direction of the milling gap. Such a wear-protection feature comprises a wear-resistant coating, for example, such as a surface-welding, wear-protection elements, or wear-protection coatings. The peripheral elements are preferably configured from steel.

In the operation of the roller mill, a material layer is usually formed on the surface of the grinding rollers, said material layer having the effect of an autogenous wear protection feature of the roller surface. According to one insight of the inventor, said wear-protection layer is thicker on those end regions of the roller ends that are provided with peripheral elements than on the remaining regions of the grinding rollers. This leads to an increased grinding pressure on account of which the peripheral elements are more heavily stressed and wear or fail more often. The material accumulation on the grinding roller ends on the peripheral elements is reliably prevented by means of the scraping elements. The risk of increased wear and of a failure of the peripheral elements is minimized on account thereof.

According to the first aspect, the scraping element is disposed in such a manner that said scraping element in the operation of the roller mill removes material that has accumulated on the peripheral element and/or on the end region of the grinding roller. The scraping element is disposed so as to be stationary relative to the rotatable grinding rollers so that the grinding rollers rotate relative to the scraping element.

According to a further embodiment, the scraping element is arranged spaced apart from the peripheral element and/or the end region of the grinding roller. The spacing between the scraping element and the peripheral element and/or the end region of the grinding roller is preferably more than or equal to 1.5 mm to 3 mm, in particular more than or equal to 2 mm. A spacing between the scraping element and the peripheral element and/or the end region of the grinding roller prevents contact between the scraping element and the grinding roller and thus minimizes the wear on the scraping element.

The scraping element according to a further embodiment is configured such that the spacing between the scraping element and the peripheral element and/or between the scraping element and the end region of the grinding roller is capable of being set. In particular, the thickness of the material layer on the end regions of the grinding rollers should not exceed a specific value of, for example, 1 mm to 30 mm, in particular 2 mm to 25 mm, preferably 5 mm to 10 mm. A spacing that is capable of being set ensures that the spacing between the otherwise stationary scraping element and the peripheral element and/or the end region of the grinding roller is kept constant in the event of wear on the scraping element. Additionally, the service life of the scraping element is extended, and a replacement in the event of wear is not required.

As noted above, the roller mill comprises a stationary machine frame, the two grinding rollers being mounted to the frame as noted below. The scraping element is attached to that same machine frame. The machine frame comprises, for example, a plurality of frame elements which are connected to bearing jewels of the grinding rollers such that the grinding force acting on the grinding rollers is transmitted to the machine frame. A machine frame of a roller mill comprises in particular a frame element which extends substantially in the axial direction of the grinding rollers and to which the scraping element is preferably attached. The scraping element extends from the machine frame in the direction of the grinding roller towards the end region of the grinding roller.

The roller mill according to a further embodiment comprises at least two scraping elements which are disposed on end regions of opposite roller ends of a grinding roller. The scraping elements are therefore located over opposite end regions of the grinding roller.

According to a further embodiment, the scraping element comprises a scraping plate which is configured from a wear-resistant material such as, for example, tungsten carbide. The scraping plate is disposed on that end of the scraping element that faces the grinding roller and in the operation of the roller mill is in contact with the material to be scraped. The scraping plate is therefore subjected to high wear, wherein a wear resistant material extends the service life of the scraping plate.

The scraping element according to a further embodiment comprises an arm to which the scraping plate is releasably fastened. For example, the scraping plate is clamped or screw-fitted to the arm. The scraping plate in the direction of the grinding roller preferably projects beyond the arm. A releasable fastening of the scraping plate of the scraping element enables the scraping plate be readily replaced, said scraping plate representing the most wear-intensive region of the scraping element. Replacement of the entire scraping element in the event of wear is thus not required.

According to a further embodiment, each of the grinding rollers comprises one peripheral element at the end region of one of the roller ends, configured in such a manner that said peripheral element extends across the milling gap and at least partially covers the end side of the opposing grinding roller. The peripheral elements in terms of the end regions of the grinding rollers are thus disposed so as to be diagonally opposite.

The scraping element according to a further embodiment extends along a peripheral element. In particular, the scraping element extends in the radial direction of the grinding roller, for example so as to be parallel or oblique to the peripheral element. The spacing between the peripheral element and the scraping element is preferably consistent across the length of the scraping element.

The invention furthermore provides, in a second aspect, a method for operating a roller mill for comminuting granular material having a first grinding roller and a second grinding roller which are disposed opposite each other and drivable in a counter rotating manner, wherein a milling gap is configured between the opposing grinding rollers. At least one of the grinding rollers comprises at an end region of opposite ends of the rollers a peripheral element which is configured to extend across the milling gap and at least partially cover an end side of the opposite grinding roller. The method comprises the step of removing material from at least that one of the end regions of the grinding rollers that comprises the peripheral element, wherein the material is at least partially removed from the roller mill, in the operation of the roller mill with rotating grinding rollers, by means of a scraping element that is stationary relative to the grinding rollers and is located over the relevant end region of the grinding roller.

The advantages described in the context of the grinding roller apply in an analogous manner to the method for operating a roller mill for comminuting granular material.

4. BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail hereunder by means of a plurality of exemplary embodiments with reference to the appended drawings in which:

fig. 1 shows a schematic illustration of a fragment of a roller mill in a plan view, according to an exemplary embodiment;

fig. 2 shows a schematic illustration of a fragment of a roller mill in a plan view, according to a further exemplary embodiment;

fig. 3 shows a schematic illustration of a fragment of a grinding roller having scraping elements in a perspective view, according to an exemplary embodiment;

fig. 4 shows a schematic illustration of a scraping element in a perspective view, according to an exemplary embodiment; and

fig. 5 shows a schematic illustration of the scraping element in fig. 4, in a perspective rear view.

5. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Fig. 1 shows a roller mill 10 having a first grinding roller 12 and a second grinding roller 14 which comprise in each case a substantially cylindrical main roller body. The grinding rollers 12, 14 are disposed opposite one another and drivable in a counter rotating manner. A milling gap 16 which extends in the axial direction of the roller body is configured between the grinding rollers 12, 14. The grinding rollers 12, 14 are disposed almost mutually parallel such that the milling gap 16 extending between the grinding rollers 12, 14 comprises an almost consistent width. Each of the grinding rollers 12, 14 furthermore comprises a drive shaft 30, 32 which extends along the central axis through the respective grinding roller 12, 14 and drives the grinding rollers so as to rotate about their central axes. The first and the second grinding roller 12, 14 have identical diameters, wherein the first grinding roller 12 can be longer than the second grinding roller 14.

The grinding rollers 12, 14 comprise in each case a first end region 24, 28 and a second end region 22, 26 which are located on opposite axial ends of the grinding roller. Across the milling gap 16, the first end region 24 of the first grinding roller 12 is located opposite the first end region 28 of the second grinding roller 14, and the second end region 22 of the first grinding roller 12 is located opposite the second end region 26 of the second grinding roller 14.

The first grinding roller 12 comprises two boundary elements, herein referred to as peripheral elements 18, 20, which are present at the axially-opposite end regions of the grinding roller 12. The first peripheral element 18 is attached at the first peripheral region 22 of the first grinding roller 12 and in the radial direction extends beyond the milling gap 16 such that said first peripheral element 18 partially covers the end side (axial end face) of the second grinding roller 14 at the latter's first end region 26. The second peripheral element 20 is attached at the second end region 24 of the first grinding roller 12 and in the radial direction extends beyond the milling gap 16 such that said second peripheral element 20 partially covers the end side (or axial end face) of the second grinding roller 14 at the latter's second end region 28. The arrangement is such that an end-side gap 34, 36 is maintained between the peripheral elements 18 and 20 of the first grinding roller 12 and the respectively facing end sides at the axially opposite ends of the second grinding roller 14.

The peripheral elements 18, 20 in each case comprise a peripherical circular ring which can also be composed of segments, for example, which is attached to the grinding roller 12 in a manner that is not further illustrated. For example, the peripheral elements 18, 20 can be attached to the end sides (i.e. axial end faces) or to the external circumference of the grinding roller 12, in particular the peripherally running surface of the roller main body. For example, an encircling groove may be present on the external circumference of the grinding roller 12 at opposite ends of the roller body in the end regions 22 and 24 in which a respective peripheral element 18, 20 is received. The peripheral elements 18, 20 are configured from a wear-resistant material such as, for example, steel, and comprise a wear-resistant coating in particular on the internal side that faces toward the milling gap 16. The peripheral elements 18, 20 can have a thickness of, for example, 10 mm to 100 mm, and cover the opposite grinding roller 14 by approximately 2 to 20%, in particular 4 to 10%, preferably 3 to 6%, of the roller diameter.

It will be self-understood that in variation of what has just been described, the peripheral elements 18, 20 may be present on the second grinding roller 14 instead of the first grinding roller 12 in which case no peripheral elements are present at the first grinding roller 12.

Fig. 2 shows a further embodiment of a roller mill having a first and a second grinding roller 12, 14 but in which the peripheral elements 18, 20 are arranged differently. The grinding rollers 12, 14 corresponds substantially to the grinding rollers illustrated in fig. 1 but differ in that each of the grinding rollers 12, 14 comprises in each case only one peripheral element 18, 20 rather than two. The first and the second grinding roller 12, 14 have identical diameters and identical lengths and are configured so as to be of substantially identical construction.

The peripheral elements 18, 20 may be described as being located on diagonally opposite at end regions 24 and 26 of the two grinding rollers 12, 14 that do not face each other across the grinding gap 16. That is, the first grinding roller 12 comprises a peripheral element 18 at the first end region 24 thereof which in the radial direction extends across the milling gap 16 and partially covers the end side of the second grinding roller 14 at the first end region 28. The second grinding roller 14 in turn comprises a peripheral element 20 at the second end region 26 thereof which in the radial direction extends across the milling gap 16 and partially covers the end side of the first grinding roller 12 at the second peripheral region 22. The second peripheral element 20 in terms of the first peripheral element 18 is disposed on the diagonally opposite end region 26 of the second grinding roller 14. The grinding rollers 12, 14 are offset in the axial direction such that a first end-side gap 34 is configured between the first peripheral element 18 and the end side of the second grinding roller 14, and a second end-side gap 36 is configured between the second peripheral element 20 and the end side of the first grinding roller 12. The first and the second end-side gap 34, 36 extend in each case in the radial direction.

Fig. 3 shows a fragment of a first grinding roller 12 of the roller mill 10 according to fig. 1, the mill having a roller frame 38 (also referenced herein as machine frame) at which the first and the second grinding roller 12, 14 are secured. The roller frame 38 comprises a support (beam) 40 which extends in the axial direction of the grinding roller 12 and is disposed at a spacing therefrom.

Illustratively, two scraping elements 42, 44, which respectively extend in the direction of the facing respective end regions 22, 24 of the grinding roller 12, are attached to the support 40. The scraping elements 42, 44 are disposed to be spaced apart from the peripheral surface of grinding roller 12 and respectively also from the radially extending surface of peripheral element 18, 20 of the grinding roller 12 such that the scrapers 42, 44 do not touch the grinding roller 12 and the peripheral elements 18, 20. The first scraping element 42 is attached to a region of the support 40 that lies opposite the first end region 22 of the grinding roller 12, wherein the first scraping element 42 in the radial direction of the grinding roller 12 extends along the first peripheral element 18 and is aligned so as to be substantially parallel to the latter. However, other alignments are also possible. The second scraping element 44 in a corresponding manner is disposed opposite the second end region 24 and the second peripheral element 20 of the grinding roller 12. The scraping elements 42, 44 extend in each case along the axially inward-pointing faces of the peripheral elements 18, 20. The scraping elements 4, 44 are configured so as to be mutually identical, for example.

Fig. 3 only shows the disposal of the scraping elements 42, 44 on a roller mill according to fig. 1. A roller mill 10 as illustrated in fig. 2 likewise comprises two scraping elements 42, 44. Each grinding roller 12, 14 of the roller mill 10 illustrated in fig. 2 comprises in each case one scraping element 42, 44 which is attached, for example, to a respective support 40 of the roller frame 38 and, in a manner corresponding to the exemplary embodiment in fig. 3, extends in the direction of that one of the end regions of the grinding roller 12, 14 that has the peripheral element 18, 20.

Fig. 4 shows an enlarged view of an embodiment of a scraping element 42, 44. The scraping element 42, 44 comprises a fastening plate 46 which in the assembled position of the scraping element 42, 44 secures to the support 40 of the roller frame 38. The fastening plate comprises a plurality of fastening bores 48 which serve for fastening the scraping element 42, 44 to the support 40, for example by means of screws.

An arm 50 is attached to the fastening plate 46, said arm 50 extending in relation to the fastening plate 46 at an angle of, for example, approximately 30 to 600, in particular approximately 450, in the direction of the grinding roller 12, 14 (not illustrated). A scraping plate 52 is provided at the arm 50 and fastened to it by means of two screws 54 and a clamping plate 56. The scraping plate extends parallel to the arm 50 beyond the end of the arm that faces away from the fastening plate 46 such that the scraping plate 52 on the arm 50 projects in a radial direction of the grinding roller 12, 14. The scraping plate 52 is clamped between the clamping plate 56 and the arm 50 such that said scraping plate is easy to replace in the event of wear. In an exemplary manner, the scraping plate 52 is received in a clamping receptacle 58 which is located between the clamping plate 56 and the arm 50 and is clamped by means of the clamping plate 56 and the screws 54.

The front edge of the scraping plate 52 in the exemplary embodiment of fig. 4 extends at an angle in relation to the surface of the respective grinding roller 12, 14 such that the spacing between the scraping plate 52 and the surface of the grinding roller 12, 14 is less in the direction towards the grinding roller end. The angle between the scraping plate 52 and the surface of the grinding roller 12, 14 is, for example, 450 to 1350. It is likewise conceivable that the front edge of the scraping plate 52 extends so as to be substantially parallel to the surface of the respective grinding roller 12, 14, in particular in the axial direction of the grinding roller. The lateral face of the scraping plate 52 as well as the lateral face of the arm 50 extend along the respective peripheral element 18, 20. In particular, a gap of more than or equal to 1 mm, in particular more than or equal to 2 mm, is configured between the scraping element 42, 44 and the surface of the grinding roller 12, 14.

The fastening plate 46, the arm 50, the clamping receptacle 58 and the clamping plate 56 are made from steel, for example. The scraping plate 52 is made from a highly wear-resistant material such as tungsten carbide, for example.

Fig. 5 shows a rear view of the scraping element 42, 44 in fig. 4. The arm 50 in an exemplary manner comprises a substantially U-shaped profile, wherein the clamping plate 56 and the clamping receptacle 58 are attached to the arm 50 by means of screws 54 and nuts.

The peripheral elements 18, 20 in the operation of the roller mill 10 prevent material exiting the milling gap 16 laterally, that is in axial direction of the grinding rollers 12, 14. An autogenous wear-protection feature is constructed on the surface of the grinding rollers 12, 14 on account of the accumulation of material. The scraping elements 42, 44 during the rotation of the grinding roller 12, 14 scrape material that has accumulated on the end regions of the grinding roller 12, 14 and thus ensure that the autogenous wear-protection layer does not exceed a specific thickness even in the end regions of the grinding rollers 12, 14 to which the peripheral elements 18, 20 are attached such that the peripheral elements are reliably protected against high pressure on account of accumulated material.

List of reference signs 10 Roller mill 12 First grinding roller 14 Second grinding roller 16 Milling gap 18 First peripheral element 20 Second peripheral element 22 First end region of the first grinding roller 24 Second end region of the first grinding roller 26 Second end region of the second grinding roller 28 First end region of the second grinding roller 30 Drive shaft of the first grinding roller 32 Drive shaft of the second grinding roller 34 First end-side gap 36 Second end-side gap 38 Roller frame 40 Support 42 First scraping element 44 Second scraping element 46 Fastening plate 48 Fastening bores 50 Arm 52 Scraping plate 54 Screws 56 Clamping plate 58 Clamping receptacle 60 Nut

EDITORIAL NOTE

*2018264756*

Please note Claim 6 is missing in the amended claims set filed on 26 August 2021. Total claims are 12.

Claims

Claims

1. A roller mill for comminuting granular material, comprising - a first grinding roller and a second grinding roller which are disposed opposite each other and drivable in a counter-rotating manner, - wherein a milling gap is configured between the opposing grinding rollers, - wherein at least one of the grinding rollers comprises at an axial end region of said grinding roller a peripheral element configured to extend across the milling gap and at least partially cover an axial end side of the opposite other grinding roller, and wherein - a scraping element is present and configured for at least partially removing material from the grinding roller, characterized in that the scraping element is attached to a machine frame at which the grinding rollers are mounted, in that the scraping element is held stationary relative to the grinding rollers, and in that the scraping element is disposed at a location above, in a radial direction of the grinding roller, the axial end of the grinding roller at which the peripheral element is provided.

2. The roller mill as claimed in claim 1, wherein the scraping element is disposed to remove at least part of the material that has accumulated on one or both of the peripheral element and the axial end region of the grinding roller during operation of the roller mill.

3. The roller mill as claimed in any one of the preceding claims, wherein the scraping element is disposed spaced apart from the peripheral element and the axial end region of the grinding roller.

4. The roller mill as claimed in any one of the preceding claims, wherein the scraping element is arranged such that at least one of a spacing between the scraping element and the peripheral element and a spacing between the scraping element and the axial end region of the grinding roller can be selectively set.

5. The roller mill as claimed in any one of the preceding claims, wherein the roller mill comprises two of said scraping elements which are respectively disposed radially above opposite ones of the axial end regions of the grinding rollers.

7. The roller mill as claimed in any one of the preceding claims, wherein the scraping element comprises a scraping plate made from a wear-resistant material.

8. The roller mill as claimed in claim 7, wherein the scraping plate material is tungsten carbide.

9. The roller mill as claimed in claim 7 or 8, wherein the scraping element comprises an arm to which the scraping plate is releasably fastened.

10. The roller mill as claimed in any one of the preceding claims, wherein each of the grinding rollers comprises one said peripheral element at one of the axially opposite axial end regions, and wherein the peripheral elements are located at opposite axial ends of the facing grinding rollers across the milling gap.

11. The roller mill as claimed in any one of the preceding claims, wherein the scraping element extends along the peripheral element.

12. A method for operating a roller mill for comminuting granular material, the roller mill having a first grinding roller and a second grinding roller which are disposed opposite each other and drivable in a counter-rotating manner, wherein a milling gap is configured between the opposing grinding rollers, and wherein at least one of the grinding rollers comprises at an end region of opposite axial ends of the rollers a peripheral element which is configured to extend across the milling gap and at least partially cover an end side of the opposite grinding roller, the method comprising at least the step of: - removing at least partially material from that one of the axial end regions of the grinding rollers that comprises the peripheral element by means of a scraping element that is attached to a machine frame at which the grinding rollers are mounted and which scraping element is held stationary relative to the grinding rollers and is located over the relevant end region of the grinding roller.

13. The method as claimed in claim 12, wherein the material is removed from those axially opposite end regions of the two grinding rollers that have a said peripheral element.