AU2011208950A1

AU2011208950A1 - Vented bottom ring assembly

Info

Publication number: AU2011208950A1
Application number: AU2011208950A
Authority: AU
Inventors: Mark Wild
Original assignee: Bradken UK Ltd
Current assignee: Bradken UK Ltd
Priority date: 2010-01-28
Filing date: 2011-01-28
Publication date: 2012-08-02
Also published as: PL400394A1; GB2489862A; WO2011091477A1; GB201212795D0

Abstract

A vented bottom ring assembly for a grinding mill, the assembly having an axis and comprising: a bottom ring having opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending between the major surfaces; one or more intermediate members disposed on the outer peripheral edge; and a throat ring extending about the outer peripheral edge and being fixed to the one or more intermediate members.

Description

WO 2011/091477 PCT/AU2011/000089 Vented Bottom Ring Assembly Technical Field The present invention relates generally to a grinding apparatus and more particularly to 5 grinding mills of the type having a bottom ring with airflow passages, on which one or more grinding rolls, balls, or tyres are adapted to travel. Such grinding mills include ring-ball grinding mills. It may also include grinding mills of the roll and race type having a bottom ring on rotatable grinding table(s). Such grinding mills have particular application in the grinding of coal for use in power plants and the invention is herein 10 described in that context. However it is to be appreciated that the invention is not limited to that use and, for example, may be used in other grinding applications such grinding of coal for cement plants and other industrial and steel milling applications, grinding raw materials in cement plants, grinding of phosphates and other raw materials in chemical plants. 15 Background Ring-ball grinding mills are commonly used in power generating plants to produce coal dust used as a fuel in the generation of electrical power. The grinding mill includes a bottom ring which is typically fitted to a grinding table and a plurality of grinding rolls 20 or balls which travel on the grinding ring in a raceway formed on the bottom ring. An annular passage may be provided between the bottom ring and the mill wall to allow air flow through the mill. As coal is crushed in the grinding mill air may be caused to flow upwardly through the passage to lift and carry dust particles out of the mill typically into a fuel stream for the power plant. 25 Roll and race type of grinding mills are also known for use a pulverisers for coal. These grinding mills have a bottom ring on rotatable grinding table, and have airflow passages. The grinding table is provided with a race for rollers on fixed axes to rotate in, and as the grinding table is rotated, the rollers rotate against the race to crush the 30 coal. The grinding table may be monolithic or segmented, and the airflow passages assist in lifting the dust particles as described above.

WO 2011/091477 PCT/AU2011/000089 -2 In one form, the annular passage is formed by a throat ring which includes the annular passage and which is fitted around the outer peripheral edge of the bottom ring. In the past problems have been encountered in fixing the throat ring to the bottom ring to form a vented bottom ring assembly for use in such grinding mills. 5 Summary According to a first aspect, the present invention provides a vented bottom ring assembly for a grinding mill, the assembly having an axis and comprising a bottom ring having opposite major surfaces extending transverse to the axis, and an outer peripheral 10 edge extending between the major surfaces. The assembly further includes one or more intermediate members disposed on the outer peripheral edge and a throat ring extending about the outer peripheral edge, the throat ring being fixed to the one or more intermediate members. is In one form, the intermediate member is continuous about the outer peripheral edge. In a particular form, the intermediate member is in the form of a steel metal band which extends about the outer peripheral edge. According to the first aspect, the throat ring of a vented bottom ring assembly is 20 mounted on the outer peripheral edge of the bottom ring through one or more intermediate members. Such an arrangement has particular application where the bottom ring is made from white cast iron (otherwise known as "white iron"). White iron exhibits good hardness and abrasion resistance and therefore it is well suited in grinding equipment. However the white iron does not lend itself to be easily drilled and 25 tapped. The vented bottom ring assembly according to the first aspect of the invention ameliorates this problem by mounting the throat ring to one or more intermediate members mounted on the outer peripheral edge of the bottom ring, rather than directly to the bottom ring. The one or more intermediate members may be made from a material, such as mild steel, which can be drilled and tapped. This allows for edge 30 mounting of a throat ring to a white iron bottom ring which previously has not been possible.

WO 2011/091477 PCT/AU2011/000089 -3 In one form, the outer peripheral edge of the bottom ring includes a recess and the one or more intermediate members are located within the recess. In one form, the recess may extend continuously about the peripheral edge of the bottom ring or, in another form, may only extend around part of the peripheral edge. In one form, the recess may 5 be made up of multiple recess portions which may be spaced apart from one another and which collectively may form the recess. In a particular form, the throat ring includes one or more radially inwardly directed lugs that locate in the recess in the outer peripheral edge. In a particular embodiment the 10 one or more lugs of the throat ring seat on the intermediate member(s) and in one form, this seating occurs within the recess in the outer peripheral edge of the bottom ring. In one form, the throat ring is fixed to the intermediate members by mechanical fasteners which in one form are bolts which are screwed into tapped holes drilled into 15 the intermediate member(s). In a particular form, these mechanical fasteners extend generally axially through the holes formed in the one or more lugs of the throat ring. In a particular form, the bottom ring includes axially extending slots adjacent the outer peripheral edge. The axial slots extend from one of the major surfaces of the bottom 20 ring to the recess in the outer peripheral edge. In a particular form, these slots are arranged to receive respective ones of the mechanical fasteners to fix the throat ring to the intermediate member. In another form, the throat ring is fixed to the one or more intermediate members by 25 welding. In one form, the throat ring comprises a plurality of throat ring segments. In a particular form, the throat ring segments are arranged and fixed to the intermediate members to form the throat ring. 30 In a further aspect there is provided a vented bottom ring assembly having an axis and comprising a bottom ring formed of white cast iron and having opposite major surfaces WO 2011/091477 PCT/AU2011/000089 -4 and an outer peripheral edge extending between the major surfaces. The bottom ring further includes a throat ring extending about the outer peripheral edge, the throat ring incorporating one or more axially extending passages and being mounted to the bottom ring along its outer peripheral edge. 5 In one form, the outer peripheral edge of the bottom ring includes a recess and at least a portion of the throat ring locates within the recess. In a particular form, the portion of the throat ring includes an inwardly directed rim that locates in the recess in the outer peripheral edge. In yet another form, the throat ring includes one or more radially 10 inwardly directed lugs that locate in the recess in the outer peripheral edge. In one form, the throat ring is continuous about the outer peripheral edge. In one form, the throat ring is not fastened to the bottom ring, but rather is held in place by its dimensional relationship with the bottom ring. For example a continuous throat ring is is held in fictional engagement against the bottom ring peripheral edge or located within a recess formed in that peripheral edge. In one form, the throat ring comprises a plurality of throat ring segments. In a particular form, at least one throat ring segment is fixed to another throat ring segment 20 to form a continuous ring about the outer peripheral edge. In one form the segments may be connected together by mechanical fasteners. In another form, at least one throat ring segment is fixed to another throat ring segment by welding. In one form of the second aspect the throat ring is mounted to the outer peripheral edge 25 using one or more intermediate members as described in any form above with reference to the first form. In a particular form the intermediate is continuous about the outer peripheral edge and in a particular form is formed from material such as a mild steel band. 30 In one form the throat ring is integrated with the band so as to have the dual functions of providing a vent for the bottom ring and act as a safety band for the bottom ring. In one form the ring and band are integrated by being formed as a single element (such as WO 2011/091477 PCT/AU2011/000089 - 5 through casting). The integrated throat ring and band may be formed in segments which are interconnected around the peripheral edge to form the continuous ring around that edge. 5 In a further aspect, there is provided a bottom ring assembly for a grinding mill, the assembly having an axis and comprising a bottom ring having opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending between the major surfaces; and one or more intermediate members disposed on the outer peripheral edge; the assembly being configured to allow a throat ring mountable on the outer 10 peripheral edge to be fixed to the one or more intermediate members. In yet a further aspect, there is provided a bottom ring for a grinding mill, the bottom ring having an axis, opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending between the major surfaces, the bottom ring including a is recess disposed in the outer peripheral edge, and a plurality of axially extending slots disposed adjacent the outer peripheral edge, the axial slots extending from one of the major surfaces to the recess in the outer peripheral edge. In another aspect, there is provided a throat ring mountable to a bottom ring of a 20 grinding mill, the throat ring comprising a body having an inner wall and an outer wall, the walls -being spaced apart to form an annular passage therebetween, and a retaining formation extending inwardly from the inner wall, the retaining formation being arranged locate on an outer periphery of the bottom ring. In one form, the retaining formation comprises a plurality of inwardly directed lugs. In one form, the retaining 25 formation comprises an inwardly directed rim. In yet another aspect there is provided a method of fixing a throat ring to a bottom ring to form a vented bottom ring assembly for a grinding mill, comprising fixing the throat ring to an intermediate member disposed on an outer peripheral edge of the bottom ring. 30 Brief Description of the Drawings It is convenient to hereinafter describe an embodiment with reference to the WO 2011/091477 PCT/AU2011/000089 -6 accompanying drawings. The particularity of the drawings and the related description is to be understood as not superseding the generality of the preceding broad description of the invention. 5 In the drawings: Fig. 1 is a plan view of a vented bottom ring assembly mounted in a grinding mill; Fig. 2 is a edge elevation of the assembly of Fig. 1, with the mill wall assembly omitted for clarity; Fig. 3 is a schematic perspective view of the bottom ring assembly for use in the vented 10 bottom ring assembly of Fig. 1; Fig. 4 is a schematic view of a throat ring segment for use in the assembly of Fig. 1; Fig. 5 is a sectional view along section line A-A of Fig. 1; Fig. 6 is a sectional view along section line B-B of Fig. 1. Fig. 7 is a sectional view similar to Fig. 6 in an alternative embodiment of the vented is bottom ring assembly. Fig. 8 is a sectional view similar to Fig. 6 in yet an other alternative embodiment of the vented bottom ring assembly. Detailed Description of the Drawings 20 Figs. 1 and 2 illustrates a vented bottom ring assembly 10 mounted within a grinding mill wall 100. The bottom ring assembly 10 includes three main components, being a bottom ring 12, a throat ring 14 and an intermediate member 16 which is fitted on an outer peripheral edge 18 of the bottom ring 12. The assembly 10 includes an axis CL and is typically arranged to rotate about that axis in operation. The throat ring 14 is 25 arranged to be fixed to the intermediate member 16 (which in the illustrated form is a mild steel band) to as will be explained in more detail below. As best shown in Fig. 3, the bottom ring 12 includes opposite upper 20 and lower 22 surfaces and incorporates the outer peripheral edge 18 is disposed between those 30 surfaces. The upper surface 20 is dished to form an annular raceway and is arranged to receive one or more grinding rolls or balls which moves across that upper surface 20. The bottom ring 12 is typically a cast component and in one form is made from cast WO 2011/091477 PCT/AU2011/000089 -7 white iron. Cast white iron exhibits high wear resistance and hardness. However it is to be appreciated that the bottom ring may be manufactured from other materials. The peripheral edge 18 of the bottom ring includes a recess 24 which incorporates an 5 upwardly facing ledge surface 26 on which the intermediate member 16 locates. The bottom ring 12 further comprises a plurality of axially extending slots 36 which extend adjacent the outer peripheral edge 18. These axial slots extend from the major surface 20 to the recess 24. These axial slots 36 are arranged to provide access for mechanical fasteners to fix the throat ring in position as will be described below. 10 The intermediate member 16 is fitted so as to locate within the edge recess 24 of the bottom ring 12. The member 16 as shown is a continuous band (in one form made of mild steel). The intermediate member may be made from an elongate strip where the ends of the strip are joined (by for example a welding, or by mechanical fastener) to is form the band. In this way the intermediate member 16 may be fitted into the edge recess 24 of the bottom ring 12 without requiring the memberl6 to be expandable (the ends of strip which form the intermediate member are joined together after locating the strip in the recess). 20 In the illustrated form, the intermediate member is continuous about the peripheral edge 24 but in an alternative form (not shown) the intermediate member may be located across only a portion of the peripheral edge, and or made from discrete components. An advantage of having the intermediate continuous is that no separate fixing of the member 16 to the peripheral edge is required as the intermediate member16 is held in 25 the recess 24 merely by the geometry of the components. The intermediate member 16 further comprises tapped holes 28 which are spaced about the member 16. These tap holes are in an upper surface 30 of the member 16 which is opposite the surface 32 which locates on the ledge 26 in the recess 24. The tapped 30 holes 28 are arranged to receive mechanical fasteners which in the illustrated form are bolts 34 which are used to fix the throat ring 14 to the intermediate member 16. These tapped holes 28 are arranged to align with the axial slots 36.

WO 2011/091477 PCT/AU2011/000089 -8 As best illustrated in Fig. 4, the throat ring 14 comprises inner and outer walls 38, 40 which are spaced apart to form a generally annular passage 42. Vanes 44 may be disposed in the annular passage to hold the walls 38, 40 apart and to direct air flow in s the passage 42. The throat ring 14 when fitted to the bottom ring 12 extends about the peripheral edge of the bottom ring 12 and together the bottom ring 12 and throat ring 14 form a vented bottom ring assembly. In the illustrated form, the walls 38, 40 are mutually inclined so that the passage tapers 10 towards an upper surface 46. However it is to be appreciated that the throat ring 14 may be configured with other shaped passages 42 ( for example with a passage extending only around discrete portions of the peripheral edge of the bottom ring, or the passage being other than tapering towards the upper surface 46). 15 The throat ring 14 further comprises a retaining formation which in the illustrated form is an inwardly directed rim 48 and a plurality of lugs 50 which extend inwardly from the rim 48. The rim 48 and lugs 50 are arranged to locate within the recess 24 on the peripheral edge 18 of the bottom ring. More specifically, the rim 48 is arranged to seat on the upper surface 30 of the intermediate member 16. In the illustrated form, the rim 20 48 extends over an outer edge portion of the intermediate member 16, while the lugs 50 are arranged to extend over the majority of the upper surface 30. Further the lugs 50 in the illustrated form include apertures 52 (which extend axially) which are arranged to receive the mechanical fasteners 34. In use the holes 52 are arranged to align with both the tapped holes 28 in the band and the axial slots 36. Once in position, the throat ring 25 14 can be simply fixed to the peripheral edge of the bottom ring by the mechanical fasteners 34 which locate through the axial slots 36 in the bottom ring and the holes 52 in the throat ring and engage in the tapped holes 28 in the intermediate member 16. The mechanical fasteners 34 remain accessible from the top surface 20 through the axial slots 36, thereby allowing for easy disassembly of the components. 30 Accordingly, a simple fixing system is provided for fitting a throat ring 14 to the peripheral edge 18 of a bottom ring 12. A feature of the arrangement is that the bottom WO 2011/091477 PCT/AU2011/000089 -9 ring 12 may be cast as a single piece, i.e. incorporating the peripheral recess 24 and axial slots 36 and in one form this is cast in white iron. The intermediate member (which in one form comprises a mild steel band) is then fitted to the peripheral edge and locates within the edge slot 24 of the bottom ring. The ends of the intermediate 5 member are joined together to form a continuous band. This band may have the dual function of providing a fixing point for the throat ring 14 and also act as a safety band to hold the bottom ring together if the bottom ring failed and cracked into multiple pieces. The intermediate member 16 is then able to receive the fasteners 34. If required, and as illustrated, the intermediate member 16 incorporates tapped holes 28 to receive io the fasteners. This tapping may be done after assembly of the band or prior to installation. Fig. 7 illustrates an alternative embodiment of the vented bottom ring assembly 210. For simplicity, like features have been provided with the same labels. In this embodiment, the throat ring 214 is welded to the intermediate member 216 fitted to the is peripheral edge 18. The weld 255 may be in lieu of, or provide further support to fasteners 34, described above. To fix the throat ring 214 to the intermediate member 216, the vanes 44 of the throat ring 214 are welded directly to the intermediate member 216. Advantageously, the inner wall 38 and lugs 50 may be omitted from the throat ring 214. 20 In a further embodiment, the throat ring is mounted onto the bottom ring without a separate "intermediate member". In this embodiment, the features of the "intermediate member" may be integrally fabricated with the throat ring before the throat ring is installed onto the peripheral edge. The assembly 310 of this further embodiment will 25 now be described with reference to Fig. 8. The throat ring 314 is fabricated with an inwardly directed rim 316, similar to intermediate member 216. This may be achieved by welding a band to vanes 44 and/or other throat ring components to form the throat ring 314. Alternatively the band may be integrally formed with other components of the throat ring, for example, by casting the throat ring 314 to include rim 316. The 30 throat ring in turn may then be mounted to the peripheral edge 18, by positioning the inwardly directed rim 316 in the recess 24. The methods of mounting the throat ring to the bottom ring may include the techniques used to fit the intermediate member 16 to WO 2011/091477 PCT/AU2011/000089 - 10 the bottom ring 12 as described in the embodiments described above. In a further embodiment, the throat ring comprising of a plurality of throat ring segments are directly mounted to the bottom ring. The throat ring segments may be 5 similar to the segments illustrated in Fig. 4, albeit adapted to directly mount to the bottom ring without an intermediate member as described above. In a further embodiment, lugs similar to lugs 50 in Fig. 4, are incorporated at the ends of the throat ring segments. The lugs provide regions to fasten adjacent throat ring 10 segments together for mounting to the bottom ring. Fastening may include the use of mechanical fasteners or use of welds. The bottom ring may further include a plurality of axial extending slots adjacent to the outer peripheral edge, similar to axial slots 36 in the previous embodiments. The axial slots are positioned to correspond to the lugs at the end of the throat rings, thereby allowing easy access for the respective mechanical 15 fasteners. Alternatively, the axial slots provide easy access for welding corresponding throat segments together. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, 20 the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. It is to be understood that, if any prior art publication is referred to herein, such 25 reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the invention.

Claims

1. A vented bottom ring assembly for a grinding mill, the assembly having an axis and comprising: 5 a bottom ring having opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending between the major surfaces; one or more intermediate members disposed on the outer peripheral edge; and a throat ring extending about the outer peripheral edge and being fixed to 10 the one or more intermediate members.

2. An assembly according to claim 1, wherein the one or more intermediate member is continuous about the outer peripheral edge. 15

3. An assembly according to claim 1 or 2, wherein the outer peripheral edge of the bottom ring includes a recess and the one or more intermediate members locate within the recess.

4. An assembly according to claim 3, wherein the throat ring includes one or more 20 radially inwardly directed lugs that locate in the recess in the outer peripheral edge.

5. An assembly according to claim 4, wherein the lugs of the throat ring seat on the one or more intermediate members. 25

6. An assembly according to any preceding claim, wherein the throat ring is fixed to the one or more intermediate members by mechanical fasteners.

7. An assembly according to claim 6, when dependent on claim 5, wherein the 30 mechanical fasteners extend generally axially through the one or more lugs. WO 2011/091477 PCT/AU2011/000089 - 12

8. An assembly according to claim 7, wherein the one or more lugs include holes to receive the mechanical fasteners.

9. An assembly of any one of claims 6 to 8, wherein the bottom ring further 5 includes a plurality of axially extending slots adjacent the outer peripheral edge, the axial slots extending from one of the major surfaces to the recess in the outer peripheral edge and being arranged to receive respective ones of the mechanical fasteners to fix the throat ring to the intermediate member.

10 10. An assembly according to any one of claims 1 to 5 wherein the throat ring is fixed to the one or more intermediate members by welding.

11. An assembly according to any preceding claim, wherein the throat ring comprises a plurality of throat ring segments. 15

12. A vented bottom ring assembly for a grinding mill, the assembly having an axis and comprising: a bottom ring formed of white cast iron and having opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending 20 between the major surfaces; and a throat ring extending about the outer peripheral edge, the throat ring being mounted to the bottom ring along its outer peripheral edge.

13. An assembly according to claim 12, wherein the outer peripheral edge of the 25 bottom ring includes a recess and at least a portion of the throat ring locates within the recess.

14. An assembly according to claim 13 wherein the portion of the throat ring includes an inwardly directed rim that locates in the recess in the outer 30 peripheral edge. WO 2011/091477 PCT/AU2011/000089 - 13

15. An assembly according to claims 13 or 14 wherein the throat ring includes one or more radially inwardly directed lugs that locate in the recess in the outer peripheral edge. s

16. An assembly according to any one of claims 12 to 15, wherein the throat ring is continuous about the outer peripheral edge.

17. An assembly according to any one of claims 12 to 16, wherein the throat ring is a split ring. 10

18. An assembly according to any one of claims 12 to 16, wherein the throat ring comprises a plurality of throat ring segments.

19. An assembly according to claim 18, wherein at least one throat ring segment is 15 fixed to another throat ring segment by mechanical fasteners.

20. An assembly according to claim 18, wherein at least one throat ring segment is fixed to another throat ring segment by welding. 20

21. An assembly according to claim 12, further comprising one or more intermediate members mounted on the outer peripheral edge, and wherein the throat ring is fixed to the bottom ring via the intermediate member.

22. An assembly according to claim 21, wherein the intermediate member is 25 continuous about the outer peripheral edge.

23. An assembly according to any one of claims 12 to 22, wherein the bottom ring is formed of white cast iron. 30

24. A bottom ring assembly for a grinding mill, the assembly having an axis and comprising: WO 2011/091477 PCT/AU2011/000089 - 14 a bottom ring having opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending between the major surfaces; and one or more intermediate members disposed on the outer peripheral edge; the assembly being configured to allow a throat ring mountable on the s outer peripheral edge to be fixed to the one or more intermediate members.

25. An assembly according to claim 24, wherein the one or more intermediate member is continuous about the outer peripheral edge. 10

26. An assembly according to claim 24 or 25, wherein the outer peripheral edge of the bottom ring includes a recess and the one or more intermediate members locate within the recess.

27. An assembly according to claim 26, wherein a space is provided in the recess to 15 accommodate an edge of the throat ring so as to mount the throat ring edge on the one or more intermediate members.

28. An assembly according to either claim 26 or 27, wherein the bottom ring further includes a plurality of axially extending slots adjacent the outer peripheral edge, 20 the axial slots extending from one of the major surfaces to the recess in the outer peripheral edge and being arranged to receive respective ones of the mechanical fasteners to fix the throat ring to the one or more intermediate members.

29. An assembly according to any one of claims 24 to 28, wherein the throat ring 25 comprises a plurality of throat ring segments.

30. An assembly according to any one of claims 24 to 29, wherein the one or more intermediate members include tapped holes to receive respective mechanical fasteners to fix the throat ring to the one or more intermediate members. 30

31. An assembly according to any one of claims 24 to 30, wherein the bottom ring is formed of white cast iron. WO 2011/091477 PCT/AU2011/000089 - 15

32. A bottom ring for a grinding mill, the bottom ring having an axis, opposite major surfaces extending transverse to the axis, and an outer peripheral edge extending between the major surfaces, the bottom ring including a recess s disposed in the outer peripheral edge, and a plurality of axially extending slots disposed adjacent the outer peripheral edge, the axial slots extending from one of the major surfaces to the recess in the outer peripheral edge.

33. A bottom ring according to claim 32, wherein the bottom ring is formed of 10 white cast iron.

34. A throat ring mountable to a bottom ring of a grinding mill, the throat ring comprising a body having an inner wall and an outer wall, the walls being spaced apart to form an annular passage therebetween, and a retaining formation is extending inwardly from the inner wall, the retaining formation being arranged locate on an outer periphery of the bottom ring.

35. A throat ring according to claim 34, wherein the retaining formation comprises a plurality of inwardly directed lugs. 20

36. A throat ring according to either claim 33 or 34, wherein the retaining formation comprises an inwardly directed rim.

37. A method of fixing a throat ring to a bottom ring to form a vented bottom ring 25 assembly for a grinding mill, comprising: fixing the throat ring to an intermediate member disposed on an outer peripheral edge of the bottom ring.