Lifting Liners for Rotary Tube Mills

Abstract

The present invention relates to a lifting liner intended to form part of the cover of the inner wall of the shell of a rotary mill containing a charge of grinding media, said liner having a cylindrical outer surface that matches the inner surface of the shell, rows with deflector elements and rows without deflector elements, the deflector elements having a protruding radial profile oriented inwards in a direction perpendicular to the surface of the shell, characterised in that the deflector elements form successive rings of zigzag shape, characterized in that an angle alpha relative to a plane perpendicular to the generatrix of the mill is greater than 0°.

Description

[Technical Field]

[0001] The present invention discloses a lifting liner for the first chamber of a horizontal-axis rotary tube mill, which comprises a cylindrical shell intended to accommodate the material to be ground and a certain amount of grinding media (balls, cylindrical pebbles, spherical pebbles). This liner comprises a row of elements with deflectors and elements without deflectors, the elements without deflectors being intended only to protect the shell, and the elements with deflectors being intended to lift the grinding bodies. The lifting capacity of the elements with deflectors can be adapted depending on the material to be ground. [Background technology]

[0002] Horizontal axis rotary mills are well known in the mining industry and in particular in cement production. These mills are equipped with lifting liners for wet and dry grinding. These mills rotate about a horizontal axis and typically contain steel balls of various sizes. The material to be ground is introduced at one side of the mill and, as it progresses toward the outlet, is crushed and ground between the grinding media, which are lifted by deflector elements of the liners as the mill rotates.

[0003] Such mills equipped with these liners are described in particular in the documents EP 0998353 A1, BE 1011286 A3, BE 09301481, WO 0197975 A, US 3869091 A, US 6951315 B2.

[0004] A conventional horizontal axis rotary mill is generally divided axially into two or three successive chambers by diametric partitions. The first chamber, in which coarse crushing of the material is carried out, contains grinding balls generally having a diameter between 60 mm and 100 mm. The second chamber, in which fine crushing is carried out, is equipped with classifying liners and contains grinding balls generally having a diameter between 15 mm and 60 mm.

[0005] The liner according to the invention is a lifting liner intended for the first chamber of a mill. Its performance is measured primarily in terms of its ability to lift while minimizing wear rate, which is typically measured in mm per 1000 hours of operation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] EP0998353A1 [Patent Document 2] BE1011286A3 [Patent Document 3] BE09301481 [Patent Document 4] WO0197975A [Patent Document 5] US3869091A [Patent Document 6] US6951315B2 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to produce a lifting liner that allows for a large number of configurations and a high degree of freedom in use, since wear of the liner's base plate is not linked to wear of the deflector. Deflectors that are subject to significant wear can be optionally replaced individually, without the need to replace the entire liner, if the liner is made up of two parts: the base and the removably attached deflector.

[0008] The lifting effect is achieved by a continuous ring of deflectors that form a lifting passage. These deflectors are arranged in a "zigzag" pattern, either parallel or non-parallel. This arrangement can be accentuated to a greater or lesser extent by carefully selecting the distance between two rings of deflectors, allowing a single modular element to meet a variety of needs. [Means for solving the problem]

[0009] The present invention relates to a lifting liner intended to form part of the cover of the inner wall of the shell of a rotary mill containing a charge of grinding media, said liner having a cylindrical outer surface that matches the inner surface of the shell, rows with deflector elements and rows without deflector elements, the deflector elements having a protruding radial profile oriented inwards in a direction perpendicular to the surface of the shell, characterised in that the deflector elements form successive rings of zigzag shape, characterized in that an angle alpha relative to a plane perpendicular to the generatrix of the mill is greater than 0°.

[0010] Preferred embodiments of the present invention include at least one of the following features or any suitable combination thereof. the angle alpha is in the range between 5° and 25°, preferably in the range between 10° and 25°, particularly preferably in the range between 10° and 21.8°; The liner element with deflector has two parts: a base and a deflector removably mounted to the base. The height of the deflector is between 0.5 and 4 times the diameter of the grinding media, preferably between 1 and 2 times. The distance between successive zigzag rings is constant due to the parallel arrangement of the rings relative to one another. The distance between successive zigzag rings is variable, preferably the successive zigzag rings are positioned opposite each other. - The height of the deflector is between 1 and 2 times the width of the deflector.

[0011] definition In the present invention, a "continuous" ring means that the deflectors are positioned one after the other to form a continuous, but separate, zigzag line of components, so that they are not in direct contact with each other at the junction between the two base plates of the liner, but are generally spaced apart by a few millimeters, this small space being determined by the tolerances always required in ironwork. [Brief explanation of the drawings]

[0012] [Figure 1] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 2] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 3] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 4] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 5] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 6] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 7] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 8] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 9] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 10] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 11] 1A-1C illustrate examples of possible configurations illustrating the present invention. [Figure 12] 1 shows a system for mounting a removable deflector to a base plate: screws attach the deflector to the base plate, which itself is attached to the shell of the horizontal axis mill. DETAILED DESCRIPTION OF THE INVENTION

[0013] Tables 1 and 2 below summarize the information in Figures 1-11 illustrating examples of possible configurations. These examples are intended only to illustrate the invention and are not intended to be limiting. - Angle alpha (10°, 15°, 21.8°) is the angle formed between the deflector and a plane perpendicular to the mill generatrix. The greater this angle alpha, the higher the lifting capacity of the deflector, all else being equal. "Position" (parallel, opposite) refers to the arrangement of successive zigzag rings relative to one another, for example parallel, or non-parallel or alternatively "opposite". - Deflector pitch length (314mm and 628mm), see diagram below. - The distance between the rows of deflectors (500 and 750) is the distance between successive rings of deflectors arranged in a zigzag pattern. The plates with deflectors are in each case separated by one or two rows of liner plates without deflectors.

[0014] [Table 1]

[0015] [Table 2]

[0016] [Figure 12] shows a system for mounting a removable deflector to a base plate. Screws attach the deflector to the base plate, which itself is attached to the shell of the horizontal axis mill.

[0017] The energy required to crush the ore is determined by its particle size and friability, and if a very high crushing energy is required, a large lifting of the charge is required, and therefore the lifting profile needs to be accentuated, which makes most of the grinding balls thrown up and therefore falling down when the mill is rotating, making it relatively inefficient for crushing purposes.

[0018] Conventional lifting liners with lifting plates with radial protrusions wear out at an average rate of 1 mm per 1000 hours of grinding time in cement production applications. For some ores, this rate can be much higher. However, this wear is not uniform: the protrusions wear out at about 1.8 mm / 1000 hours of operation, while the plate recesses wear out at only about 0.4 mm / 1000 hours of operation. For this reason, lifting and therefore grinding performance is significantly reduced at the end of its useful life, requiring complete replacement, even if the liner still weighs about 40% of its initial weight, and therefore its "used weight" is only 60%.

[0019] In light of the above, the objective of the present invention is therefore to separate the lifting function from the shell protection function. The wear of liner elements without deflectors has no bearing on the lifting capacity, and the function of such liner elements is simply to protect the shell. The idea is therefore to combine elements without deflectors with elements with deflectors. This allows the used weight of the liner before replacement to be significantly increased up to 75% of the initial weight, thus extending the useful life of the liner.

[0020] In the case of a liner element consisting of two parts, comprising a base and a removably attached deflector, it may be possible in some cases to replace only the deflector, which affects the lifting capacity, even if the base has already suffered considerable wear.

[0021] The liner according to the invention therefore consists of a combination of a generally flat and smooth plate intended to protect the shell from abrasion, and a plate equipped with deflectors that form a continuous ring and ensure the lifting of the grinding bodies, which are generally steel balls with a diameter of 60 to 100 mm (see for example Figures 5 and 7 illustrated with 100 mm grinding balls).

[0022] The liner plate with deflectors is configured such that the deflectors form a plurality of successive rings with greater or lesser distances between the rings, forming a "zigzag" configuration, the "zigzag" configuration being exaggerated to a greater or lesser extent by the angle alpha formed between the deflector and a plane perpendicular to the mill generatrix (see, for example, Figures 1, 9, and 10, which illustrate three different angles).

[0023] The parameters that have a major influence on the lifting capacity of the liner according to the invention are: - the distance between successive rings of deflectors arranged in a staggered manner and therefore, consequently, the number of liner plates with these deflectors. - zigzag accentuation with an angle alpha between 5° and 25°, preferably between 10° and 25°, this angle being measured relative to a plane perpendicular to the generatrix of the mill. - Arrangement of successive rings in a zigzag pattern relative to each other, for example parallel or non-parallel or alternatively "opposite". - the height of the deflector, which is directly related to the diameter of the grinding ball used. For a grinding ball with a diameter of 100 mm, the height of the deflector generally ranges from 80 mm to 200 mm (generally between 0.5 and 4 times the maximum diameter of the grinding ball, preferably between 0.8 and 2 times).

[0024] The liner according to the invention has a wide range of possible configurations and is therefore flexible in use: some ores require very large lifting capacities with a large number of deflector elements, a large height and a large angle alpha, as opposed to other ores with less severe working conditions, which require a smaller number of rows of deflector plates and a smaller angle alpha.

[0025] The diameter of the grinding balls used in their new condition is generally in the range of 50 mm to 125 mm, preferably in the range of 60 mm to 90 mm, and the height of the deflector must be proportional to the diameter of the balls used, and should be between 0.5 and 4 times, preferably between 0.8 and 2 times the maximum diameter of the grinding balls used. The height of the deflector is generally in the range of 40 mm to 200 mm, preferably in the range of 60 mm to 160 mm, and the width in the range of 50 mm to 90 mm. The distance between two consecutive zigzag rings may be in the range of 200 mm to 800 mm, preferably in the range of 500 mm to 750 mm, and will be adapted depending on the length of the first chamber of the mill. The length of the liner plates may be variable; the length of 314 mm shown in this example corresponds to the DIN standard (DIN 24111) to take into account their mounting system.

[0026] The mill shell is therefore drilled with a number of holes to allow the insertion of bolts for attaching the liner plates. Both the configuration of the drilled holes and their diameter vary depending on the mill manufacturer. DIN, the only standard imposed in Western Europe to date, is characterized by a longitudinal hole distance of 250 mm and a circumferential hole distance of 314.16 mm. The diameter of these holes ranges from 30 mm to 42 mm, depending on the manufacturer and the size of the mill.

[0027] When the deflector and base plate are made as a single piece, the system according to the invention allows for the replacement of only the plate with the deflector when the deflector wears out. However, the deflector may be removably attached to the base, which typically has a thickness ranging from 30 mm to 80 mm depending on the desired service life. This removably attached arrangement allows for the replacement of only the deflector, since it is the deflector that ensures lifting, and wear of the base or liner element without the deflector has minimal effect on the mill performance, and the mill shell is protected.

[0028] Advantages of the liner according to the present invention Since the lifting of the grinding bodies occurs due to friction on the sides of the continuous zigzag rings, rather than on the radial protrusions, the advantages of the liner according to the present invention are as follows: Wear of these rings does not substantially change the ring segment angle alpha, thereby maintaining the same charge lifting level and consistent performance over time. The zigzag continuous rings do not throw the balls towards the bottom of the charge, therefore grinding is more efficient with less collision between the grinding balls and the liner plates. In a two-part design with a removable and therefore separately replaceable deflector, the thickness of the liner base plate can be increased, thereby increasing the portion of the liner available for wear resistance and thus extending the overall service life. This also reduces the percentage of the liner weight lost at the end of its service life. In this case, the deflector can be replaced one or more times before the base plate wears out.

[0029] The liner according to the present invention also provides two major advantages. The base plate and one type of lifter allows for over nine different liner configurations, covering virtually all types of lifting currently required to provide good crushing for the majority of products processed in ball mills for cement production (see table above).

[0030] example Crushing of products ranging from fine and soft products (e.g. crushed limestone less than 4mm, using a 15° / 314 / parallel / 750 configuration) to the coarsest and hardest products (e.g. fused clinker more than 100mm, using a 15° / 628 / opposite / 500 configuration) with an average lifting capacity of Portland clinker (less than 40mm, using a 15° / 628 / parallel / 500 configuration). By increasing the deflector angle alpha, e.g. to 21.8°, it is possible to achieve the same lifting as long as the space between the rings is increased or by reducing the deflector pitch. In contrast, if the deflector angle alpha is reduced, equivalent lifting is achieved by reducing the space between the rings or increasing the deflector pitch. The examples given relate to cement production materials, but can of course be presumptively applied to other materials, especially in the mining sector, such as for example iron ore, gold ore, lead ore or zinc ore, etc. This flexibility allows a significant reduction in the costs associated with the production and management of liner models and allows standardization of liner plates for customers using different ball mills. The arrangement of the continuous ring deflector on the liner according to the present invention has the effect of preferentially retaining the largest and heaviest particles, which are typically found around the periphery of the charge. These larger particles therefore remain in the first chamber of the grinder longer, giving them a better chance of being properly broken down before moving to the mill exit.

Claims

1. A lifting liner intended to form part of the cover of the inner wall of the shell of a rotary mill containing a charge of grinding media, said liner having a cylindrical outer surface that matches the inner surface of the shell, rows with deflector elements and rows without deflector elements, said deflector elements having a protruding radial profile oriented inwards in a direction perpendicular to the surface of the shell, said deflector elements forming continuous rings of zigzag shape, characterized in that an angle alpha relative to a plane perpendicular to the generatrix of the mill is greater than 0°.

2. 2. A lifting liner according to claim 1, wherein the angle alpha is in the range between 5° and 25°, preferably in the range between 10° and 25°, particularly preferably in the range between 10° and 21.8°.

3. 3. The lifting liner according to claim 1 or 2, wherein the liner element having a deflector has two parts: a base and a deflector removably attached to the base.

4. 4. A lifting liner according to any one of claims 1 to 3, wherein the height of the deflector is between 0.5 and 4 times the diameter of the grinding media, preferably between 1 and 2 times.

5. 5. A lifting liner according to any one of claims 1 to 4, wherein the distance between successive zigzag rings is constant due to the parallel arrangement of the rings relative to one another.

6. 6. A lifting liner according to any one of claims 1 to 5, wherein the distance between successive zigzag rings is variable, preferably the successive zigzag rings are positioned opposite each other.

7. 7. A lifting liner according to any one of claims 1 to 6, wherein the height of the deflector is between 1 and 2 times the width of the deflector.

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