DK151086B - ROADS WHICH ARE USED WHEN USING THE USE OF PARTICULAR OR PARTICULAR GOODS CONTAINING MAGNETIC PARTICLES DURING THE USE. - Google Patents

Description

151086

The present invention relates to a wall of the kind set forth in the preamble of claim 1 which, during use, is subjected to wear of unitary or particulate articles containing magnetic particles.

05 Such walls can take the form of wall surfaces in crash shafts, in trenches, in conveyor loading stations, but above all in grinders or mills. In the mining industry, mills are used for grinding ore, whereby the walls of the mills are subject to heavy wear and are therefore formed by or coated with a wear-resistant wall material. Such mills may be ball or rod mills for grinding ore containing a certain amount of magnetic material. The mills can also be mills for primary and secondary milling, where the milling material itself is made up of magnetic material, for example magnetite, and where the coarser goods contained in the load 15 form milling bodies or pebbles, ie. so-called autogenous grinding.

As mentioned, mills for such purposes must have a wear-resistant inner surface. Therefore, the mills are often provided with a liner of wear-resistant material, for example elastomeric or plastic material, ceramic material or sometimes steel material. The lining of slip-resistant material is usually fastened mechanically by means of bolts, clamping rails or the like. In US Patent No. 3,913,851, it is further proposed that a wear-resistant liner for mills and grooves be magnetically held against the inside of the mill drum or the gutter by laminating the rubber layer facing the drum or gutter with a permanent magnetic material.

The mill or mill liner has two main tasks. The first task is to provide protection for the grinding cap and the grinding cap end against mechanical and corrosive wear. The second up gift is to transfer energy from the mill or grinder to the charge.

This means that the appearance of the inside of the mill, the so-called profile, is of great importance for the grinding capacity, especially in the case of secondary grinding (fine grinding).

35 Attempts have been made to improve the function and durability of the mill casing in different ways, and utilizing various materials with different profiles on the inside of the casing. Particularly in the handling of hard minerals, such as sulphide ores, steel material has had a relatively short life, as a not insignificant material loss has occurred as a result of corrosion in connection with wet grinding, apart from the actual and actual mechanical wear.

05 Oer is therefore an attempt to use rubber as a replacement for steel liners. In addition to the good wear properties compared to steel, rubber also has a better resistance to corrosion and also a sound-reducing effect during grinding. In addition, the rubber lining is considerably lighter than steel linings. However, a disadvantage of rubber is the poorer ability of this material to withstand sliding wear than steel.

In conventional mill liners with longitudinal casing plates and so-called lifters, ie. lifting means, it is important that these lifters be replaced when they have been subjected to such a severe wear, that the charge begins to slide along the liner. Thus, when the lifters are subjected to slippery wear, they are subjected to accelerated wear and thus the intermediate sheathing plates also begin to wear down quickly. Therefore, in order to achieve a good lining economy, the lifters must be replaced in a timely manner, and usually 20 to four sets of lifters are included for each set of cutting boards. The lifters are replaced at a time when the casing profile is better than a new casing in terms of capacity and fine milling properties. When replacing the lifters, the grinding capacity can often be reduced by 10-20%.

25 The disadvantages of rubber lifters are such that the grinding capacity will vary substantially throughout the service life and that the lifters must be replaced when the casing profile is best. In other words, a lower capacity run-in period and undesirable coarse residues in the outgoing milling material must be allowed. This is especially true in the case of fine-painting 50 ί mills at a rate of over 75% of the so-called critical speed.

Replacing lifters and cover plates costs a great deal in the form of disassembly and assembly as well as downtime costs.

It would be a great advantage if a mill liner could wear down just as much over the entire liner and if the service life could be extended to a period of one year or more so that the necessary replacements could be performed during normal downtime, ie.

3 151086 holiday periods.

In order to avoid the need for lifters in ball mills, it is proposed in Danish Patent No. 15508 to use electromagnets to lift the male-05 spheres of magnetic material up to the required height during the rotation of the mill and then to release the balls and drop them. down to the goods being milled. According to this Danish patent, the electromagnets are arranged along the outside of a mill drum, which consists of slats of magnetizable material, the arrangement being such that the grinding balls are only held 10 against the mill drum during lifting up to a suitable level.

Electromagnets have also been used in mills for non-magnetic painting to magnetize the unwanted magnetic material in the goods. Such a magnetic separator device is disclosed in German Patent No. 482,598. Thus, in this case, the electromagnets are not used to replace the lifts, but to separate the unwanted material and to ensure that this material is fed through the outlet of the unwanted material.

The object of the present invention is to impart an extended life to a wall of the kind referred to at the outset.

The object is achieved by the peculiar features of the invention set forth in the characterizing part of claim 1.

Increasing the rotational speed of a mill is often desirable as the grinding capacity increases rapidly with increasing speed up to and above the so-called critical speed. At a rate of 80-85% and more of this critical rate, the inner liner profile may not contain lifting members, but the liner must have a smooth inside. During grinding, the liner is thereby subjected to a sliding wear and an accelerated wear results. Comprehensive grinding experiments with secondary grinding (fine grinding) at so-called supercritical speed have been found to give very good grinding results. However, this form of grinding has not been able to become economical due to excessively high lining costs with current inner lining materials.

When the invention is applied to mills or mills which are operated at high speed and have a smooth inside, the harmful sliding wear can be limited by practicing the invention as claimed in claim 4, thereby providing a magnetic covering formed by magnetic particles. fluid bearing magnetically retained in such a profile that the charge is raised to an appropriate level for maximum grinding capacity.

05 Abnormal shear forces between the charge and the mill drum are absorbed into this fluid bed, thus preventing excessive sliding directly against the inside of the inner liner.

When milling non-magnetic material, such as sulphide ore, if the invention is to be utilized, magnetic material, such as magnetite, must be added to the charge so that the wear protection layer which automatically renews can be obtained on the inner liner. The magnetic material should be relatively fine-grained (up to about 5 mm) As the finer material settles at the mill sheath, the magnetic material resides in the zones of the liner to be coated with the self-renewable wear protection layer. Any magnetic residue that accompanies the outgoing paint can be recovered by charging the pulp, ie. the finished grinding material, passing through a simple magnetic separator drum of conventional design at the mill outlet. Therefore, these residues can be reintroduced into the grinding circuit or they can be handled differently.

A great advantage of the invention is that the magnetic circuit, when specified in claim 6, uses permanent magnets, will be closed permanently on one side of the metal insert or the mill drum sheath and on the other side of the fine-grained fine magnet layers of magnetic particles. This automatically provides good security against demagnetization.

In the prior art US Patent No. 3,913,851, a wear and abrasion resistant liner is held in place against the inside of the mill drum by magnetism. In this case, it is thus the lining itself which is held in place by magnetic forces, thus replacing the normal mechanical anchorage of the inner lining. There is no closed magnetic circuit at the magnets away from the facing side of the mill drum, and therefore there is a high risk of successive de-magnetization.

35 The present invention, on the other hand, is based on the recognition that magnetism can be utilized to produce an automatically renewable wear protection for the inside of the mill drum, which itself can be formed of a wear and tear resistant material, for example, an elastic material. The invention is thus based on a different technical idea than the invention according to US Patent 3,913,851.

05 In the mill described in the above-mentioned Danish patent specification 15208, the paint balls made of iron must be lifted in relation to and then dropped onto the goods to be milled, and thus not to follow in the lifting under which they magnetic and iron grinding balls are attracted to the inside of the mill drum 10 by means of the electromagnets located and stationary outside the mill drum. In this known mill, the purpose of the electromagnets is different from the purpose of the magnets in the abrasive wall of the invention. Furthermore, it is a prerequisite that the magnetisation is temporarily canceled in order to release the paint balls, so that they can fall onto the grinding goods which remain in the lower regions of the mill due to gravity and by sliding along the mill sheath and thus exposing it. this one for wear. In this known mill, a lining of a material with strong resistance to abrasion is therefore necessary, even if the wear caused by the paint balls itself is reduced. The present invention goes in another direction by forming a wear protection which protects the wall, especially the mill wall, from wear and tear and automatically renews itself.

The above and other objects and advantages of the present invention will become apparent from the following description of preferred embodiments shown in the drawings, in which Figures 1-3 show three examples of a mill having a wall according to the invention, Figures 4 and 5 show a further example of a mill with a wall according to the invention, Figure 5 shows a section along the line VV in Figure 4, Figures 6 and 7 respectively. through further examples of mills with walls according to the invention, Figures 8 and 9 are a sectional view, respectively, of a plan view of the inside of another example of a wall according to the invention used in a ball mill, Figures 10 and 11 an example of a standard wall-05. Figure 10 illustrates a cross section along line XX of Figure 11, while Figure 11 shows a longitudinal section along line XI-XI of Figure 10; Fig. 12 is a section similar to Fig. 10, but where the standard element is mounted in a mill drum, and Fig. 13 shows how the principles of the invention can be used to protect walls other than mill drums.

The mill shown in Figure 1 has a mill drum 10, the inside of which has an inner liner clamped to it. This inner liner contains casing plates 11, which are made of rubber and have prominent 15 fastening flanges 12. The inner liner also includes lifters 13, which comprise an elastic part or rubber part 14 with a cut groove 15 to cooperate with a metal rail 16 with fixed welded bolts 17 which protrudes through holes in the mill casing and cooperates with a washer 18 and a nut 19. The bolts and rails 20 may be replaced by T-bolts. The mill liner 11, 13 is thus held in place by clamping the protruding attachment flanges 12 on the casing plates 11 against the mill casing 10 by means of the metal rail 16 which is embedded in the cut grooves 15. The other methods for fastening the inner liner are also within the scope of the invention 25 framework..

According to the present invention, the lifters 13 are provided with an insert 20 to which a number of permanent magnets 21 are attached. The permanent magnets extend slightly from the lifts 13 on their impact side, ie. the forward side as the mill rotates in the direction of arrow 22. However, sometimes it may be advantageous to let the permanent magnets stop immediately below the surface of the lifts. The permanent magnets 21 alternately face south and north poles outwardly, thereby attracting magnetic particles in the mill charge so that these particles are retained as a layer 23. This layer serves as a wear protection that automatically renews for the lifters 13 as the charge strikes this layer and is prevented from acting as strongly abrasive on the lifters as if the layer 23 was not present.

7 151086

Of course, the magnetic particles in the layer 23 can loosen when the charge strikes the layer 23, but new magnetic particles in the charge are thereby attracted, so that the protective layer 23 is maintained even during the continued rotation of the mill drum.

05 In Figure 1, the self-renewable wear protection of magnetic particles is shown only in the left lifter in order to make a comparison with conventional lifters better. To the right of Figure 1 is shown in broken lines 100, 101, 102 and 103 how a conventional lifter made entirely of rubber material has changed its profile in TO during a prolonged test run in a mill in which the principles of the invention were tested in parallel with the conventional lifters.

The portion 14 of the lifters 13, the casing plates 11 and the conventional lifters consisted of the same wear rubber material. The mill had a diameter of 5.9 m and was driven continuously for secondary milling 15 by means of unitary magnetite and unitary quartz in mixture (particle size maximum 60 mm), ie. so-called pebbles. The conventional lifters initially had the profile represented by line 100, while lines 101, 102 and 103 represent the remaining lifter profile after continuous operation for 7 months, 14 months and 14 months, respectively. 21 months. When profile 103 was obtained, i.e. After 21 months of operation, it was time to add new conventional lifters. After the same period, the rubber member 14 on the lifters 13 equipped with permanent magnets 21 had only been subject to minor wear, as is indicated by a 25 dotted line 14 'p in the lifter to the right in Figure 1.

During the trial, it was found that the self-renewable wear protection layer 23 was not completely homogeneous, but contained an innermost homogeneous layer 23 'of very fine-grained magnetic material as well as an outer inhomogeneous layer 23 "of coarser magnetic mineral grains as well as severely worn magnetite template bodies.

The tests performed thus show that the invention provides a very substantial improvement in the life of the mill liner by providing the self-renewable wear protection layer 23 of magnetic fine-grained material included in the batch.

Figure 2 shows another example of how the invention has been found to be applicable to protecting a mill drum from wear. In this case, the mill was designed as a primary mill, ie. a grinder for grinding coarse starting material. In this case, the mill liner was wave-shaped in that the sheath plates 24 were formed of the stair tread with a low portion 25 as well as a high portion 26, which, however, was longer than the upper side of the lifts 27.

05 The attachment of lifters and casing plates was carried out in substantially the same manner as in Figure 1. In the embodiment according to Figure 2, however, not only the lifters 27, but also the casing plates 24 were provided with metal inserts 20 and permanent magnets 21 attached thereto.

This results in the permanently higher level permanent magnets forming a slightly inclined surface profile with a protective layer 23 of magnetic particles which are attracted to the permanent magnets in the same manner as in Figure 1. Again, in this case, the protective layer was found to 23 had a layer-like structure with an inner fine-grained sub-layer as well as outer more coarse-grained sub-layer. During the test in a 2.9 m diameter mill, layer 23 had a thickness of approx. 5 cm and the layer came to contain some worn paint balls. Layer 23 formed a fluid and coherent bed or layer which provided effective protection against wear on the inner liner.

Figure 3 shows a further embodiment in which the lifters 28 are made of a rubber or elastomeric material and are co-vulcanized with a metal plate 29 protruding on both sides.

These lifters are held in place by rubber or elastomeric elements 30, which have a vulcanized metal profile 31 and which cooperate with T-bolts 32, washers 33 and nuts 34, and which clamp the metal plate 29 to the mill drum 10. As in the previous described embodiments, the lifter 28 has indwelling permanent magnets 21 mounted on a metal insert 20 and retaining a self-renewable protective layer 23 formed by attracting and retaining magnetic particles in the mill charge by the permanent magnets 21. In this case, the permanent magnets are located on a in such a way that the protective layer 23 also extends a little forward in front of the actual lifter and thus also protects the low portion in front of the lifter, where large wear usually occurs.

Figures 4 and 5 show yet another embodiment of the invention in which the lifters are designed in a different way and are provided with a protective shield. Thus, the lightweight mill 10 is lined with casing plates 35 which are joined by metal plates 36 protruding on both sides. Between successive casing plates 35 are lifters 37 having an outer protective cover 38 of non-magnetic 05 durable metal material. Inside the metal protective shield 38 are permanent magnets 21, which are attached to an insert 20 formed of magnetic metal material. The permanent magnets as well as the insert are held in place by means of a polyurethane rubber layer 39. Other plastic or elastomeric materials are also conceivable. Furthermore, the lifters are held TO in place by means of an inlaid profile rail 40 which is held clamped against the grooves formed and cut into grooves by means of bolts 41 and nuts 42 projecting through the mill sheath 10. The permanent magnets 21 are positioned with their south and north poles. in the manner shown in the drawing, such that a protective layer 23 of magnetic particles from the charge is formed on the outside of the protective shield 38.

The lifters 37 can be made relatively short, for example 100 mm, whereby the required total lifter length is obtained by placing several lifters one after the other and holding them by means of a common fastening rail 40 or by means of several such fastening rails arranged one after the other. This embodiment is particularly adapted for use in rod grinding, i.e. when milling in mills using rod-shaped paint bodies and where there is a risk that worn spear-like rod ends will penetrate and damage the lifters. The magnetic system is designed symmetrically, which means that the direction of rotation of the mill can be reversed.

Figure 6 shows a similar embodiment with symmetrical placement of the permanent magnets. In this case, the plunger 43 formed of rubber or other elastomeric material is a solid vulcanized metal profile 44 with a cut groove 45 to cooperate with T-bolts 32 and nuts 34. The lifter clamps the casing plates 35 by means of the vulcanized metal plates 36 mounted on the casing plates. .

In the embodiment of Figure 6, the permanent magnets 21 are secured to an insert 20 and have their active pole faces lying at the base of tapered recesses 48. Thus, particulate magnetic material included in the charge will fill these tapered recesses and thus serve as a self-renewable protective layer without 10 151086 for the permanent magnets and also outside the rubber or elastomer parts of the lifter 43. In this case too, the lifter is symmetrical, which is why the rotation direction of the mill can be reversed.

In the previously described embodiments, permanent magnets have been used to form the renewable protective layer of magnetic particles. Figure 7 shows another embodiment in which electromagnets are used for the same purpose. This embodiment is similar to the embodiment of Figures 4 and 5, but instead of a protective shield of non-magnetic material, inserted Ί0 magnetic steel plates 49 serving as pole plates on electromagnets 50 attached to a magnetic style insert 20. Magnets 50, insert 20 are used. and the pole plates 49 are molded into a polyurethane rubber layer 39 extending between the pole plates 49. By means of the electromagnets 50, which are connected to a power source 15 which is not shown, a protective layer 23 is formed which can be renewed. of magnetic particles included in the charge. Also in this case, the lifter is symmetrical so that the direction of rotation of the mill can be reversed.

A great advantage of the illustrated embodiment, in which the magnets 20 are secured to an insulating material embedded in elastomeric, plastic or rubber material, is that the magnets are thereby resiliently retained and can thus better withstand any strong shocks from large pieces of material included in the material. in the charge.

Figures 8 and 9 show a further embodiment of a wall of the present invention used in a ball mill. The inference is formed of two types of standard elements, one of which corresponds to the sheathing plates, while the other type corresponds to the "lifts", although this mill does not have into the mill's internal projecting lifting means. The elements 51 corresponding to the casing plates have 50 indented metal plates 52 on their side facing the mill cover 10, and the rubber member 53 of the elements extends with a layer 54 in addition to these metal plates. In the element 51, permanent magnet magnets 21 and the associated metal inserts 20 serve as magnetic cores. Protective plates 55, formed of 35 non-magnetic metal material, are secured outside to the permanent magnets 21 to protect them. The elastomeric member 53 formed by the casing element 51 has a molded elevation 56 between the rows 11 of permanent magnets to bring the particle layer forming the protective layer 23 to arch upwardly between adjacent magnets and to reduce the risk of the protective layer 23 for sliding along the inner liner due to shear forces during initial build-up periods.

The wall elements 57 corresponding to the lifts in a similar manner have permanent magnets 21, metal inserts 20 and protective plates 55 which, together with a metal profile rod 58 with a cut groove 59, are vulcanized or embedded in the elastomer part 60 in the wall element 57. This elastomer part, which may consist of polyurethane rubber, extending with a layer 61 below a portion of the metal profile bar 58 and having a molded support 62. The wall member 57 is secured to the drum sheath 10 by means of T-bolts 46 and nuts 47, thereby clamping the sheath plates 51.

In the illustrated embodiment, each of the elements 51 and 57 is arranged to contain four permanent magnets 21 as well as two metal inserts 20, so that the elements are relatively small and easily manageable during assembly. The elements can of course be made of any length.

20 In the embodiment of Figures 8 and 9, a coherent and rather thick protective layer 23 of magnetic particles contained in the paint is retained against the inner liner. In the illustrated embodiment, the sheath plates 51 have only two rows of permanent magnets 21, but if the sheath plates are to be made wider, 25 more rows of magnets can of course be placed side by side.

Figures 10 to 12 show one of the standard elements designed inner lining used in a mill. The standard elements 63, made in the form shown in Figs. 10 and 11, have permanent magnets 21 embedded in elastomeric material 64, preferably polyurethane rubber or other suitable plastic material, so that the material 64 forms elevations 65 with longitudinal V shaped therein. formed recesses 66. The material 64 leaves one long side of the permanent magnets free, so that the magnets protrude slightly from the elastomeric material. However, it is possible to let the magnets protrude from the elastomeric material also on the opposite long side. In this embodiment, therefore, a metal insert of magnetic material is not

Claims (9)

151086 embedded in the elastomeric material, but the magnetic circuit between the permanent magnets is instead closed by means of the metal wall, in this case a milling drum which is to be provided with a wear protection. This can be seen in Figure 12. In this embodiment, the magnetism is thus used not only to produce the protective layer 23 of magnetic particles, but also to hold the inner liner against its substrate. The alignment of the elements 63 to the arc shape of the mill casing drum is facilitated by the recesses 66 as well as those under these remaining bridges 67 of elastomeric material 10 serving as springs. The standard elements 66 are designed asymmetrically to facilitate proper orientation of the elements as well as their permanent magnets relative to adjacent elements. The invention is described above in connection with rotatable mill drums, but it will be appreciated that the invention can also be used for vibrating mills and also to protect wall surfaces other than mill shells. Thus, the invention is applicable to many different types of walls subjected to abrasion of goods containing magnetic particles which can form the desired and self-renewing shelter. As an example, Fig. 13 shows a unloading station 69 for a conveyor belt 70 for transporting particulate goods containing magnetic particles, for example particles of magnetite. Figure 13 is only schematic, and wall elements 68 can advantageously be formed in accordance with Figures 10 and 11, although elevations 65 are not necessarily necessary. Alternatively, the wall elements may be designed in accordance with that shown in Figures 8 and 9. As can be seen in Figure 13, the principles of the invention have been applied only to the most exposed parts of the unloading station 69 and the downstream shaft 71 below, which can open, for example, an additional conveyor 72, over a carriage, over a freight silo or over a sieve. 1. Wall subjected to wear of magnetic or particulate articles containing magnetic particles during use, the wall preferably consisting of or coated with a wear-resistant wall material (11,13; 24,27,28,20,35 , 37; 43; 51.52; 63.68), CHARACTERIZED IN THAT THE WALL HAS MAGNETIC DEVICES (21.50) THAT ARE DESIGNED TO ATTACH INTO THE MAGAZINE INCLUDING MAGNETIC 05 PARTICLES SO THAT THEY ARE WITHHOLDED AS A WEAR PROTECTION Layer (23) which automatically renews, on the surface of the wall exposed to wear, at least within such zones thereof, which are usually subject to more severe wear and tear than other wall zones. 2. A wall according to claim 1, characterized in that the magnetic device -10 (21,50) is embedded in the wall. A wall as claimed in claim 1 or 2 and formed as a mill wall with lifters (13,27,28,37,43), characterized in that the magnetic devices (21,50) are arranged to attract the magnetic particles contained in the goods, in at least against the butt of the hoists. 15 Wall according to claim 1, 2 or 3 and formed as a mill casing wall, characterized in that the magnetic devices (21,50) are arranged at such intervals that the entire surface of the wall (57,63) is covered by the self-renewable wear protection layer (23 ) during the use of the mill. 20 Wall according to any one of claims 1-4, characterized in that the magnets (21) of the magnetic devices are arranged with an active pole surface at the bottom of crater-shaped recesses (48) in the wall (43). 6. A wall according to any one of claims 1-5, characterized in that the magnets of the magnetic devices (21.50) are permanent magnets (21). Wall according to any one of claims 1-5, characterized in that the magnets of the magnetic devices (21.50) are electromagnets (50). 8. A wall according to claim 7, characterized in that the magnets (50) have a magnetic plate 30 (49) arranged on the exposed side of the wall. 9. A wall as claimed in any one of claims 1-4, 6 and 7, characterized in that the magnets (21) of the magnetic devices are arranged behind a protective shield (38) or protective plate (55) consisting of non-magnetic material.