FI65389C - FOER NOETNING UTSATT VAEGG SAERSKILT I KVARN FOER MALNING AV EN MAGNETISK MATERIAL OMFATTANDE CHARGE - Google Patents

Description

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jJSTa W (11) utläggningsskaipt 6 5 389 C (45) Patent ny'inr.oUy 10 C3 1934 'v' ^ (51) k ».Hu /into.3 B 02 C 17/22 FINLAND — FINLAND pi) Θ02201 ( 22) H »k * mhptlvi - ArKekninffd ·! 09.07.80 (22) AlkupUvl — GNtlgMadag 09.07.80 (41) Tullut (ulklMkil - Blhrtt offmtNg lU. 01.8l

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(32) (33) (31) Advance requestedMcuu · —iejlri yrtorlut 13.07.79 Sweden-Sweden (SE) 7906098-¾ (71) Socared SA, 1, Rue Ceard, Geneva, Switzerland-Switzerland (CH) (72) Bertil Brandt, Skellefteä, Sweden-Sverige (SE) (7U) Oy Heinänen Ab (5U) A wall exposed to wear, especially in a mill for grinding a charge containing magnetic material - För nötning utsatt vägg, särskilt i Kvarn för malning av en magnetiskt material omfattande charge

The present invention relates to a wear-prone wall which, in use, is exposed to the abrasive action of a particulate or particulate material comprising magnetic particles. Such walls may have the shape of wall surfaces in trough shafts, gutters, unloading stations for the conveyor belt but above all in mills. In the mining industry, mills are thus used to grind the ore, whereby the walls of the mills are subjected to severe wear and therefore the walls are formed of or clad with a wear-resistant material. Such mills may be ball or bar mills for grinding ore containing a certain amount of magnetic material. The mills can also be mills for primary or secondary grinding, in which the ground material itself consists of a magnetic material, e.g. magnetite, and in which the kaf'-65389 coarse material contained in the charge forms grinding bodies or "pebbles", so-called self-grinding. mills must, as mentioned, have a wear-resistant inside. The mills are therefore often lined with a wear-resistant material, e.g. elastic or plastic material, ceramic material or sometimes steel material1. The lining made of wear-resistant material is usually fastened mechanically by means of fastening bolts, tightening strips, etc. U.S. Patent No. 3,913,651 further proposes that the wear rubber liner for mills and chutes be held against the inside of the mill drum or chute so that the side of the wear rubber layer against the drum or chute is laminated with a layer of permanent magnet material.

The inner lining of the mill has two main functions. One is to provide protection for the mill jacket and mill jacket ends against mechanical and corrosion wear, and the other is to transfer energy from the mill to the charge.

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

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Attempts have been made in various ways to improve the operation and durability of the mill liner and different materials have been used with different profiles on the inside of the liner. Especially when handling hard minerals such as sulfide ores and the like, the steel material has had a relatively short service life because of the significant material loss that has occurred during the year of corrosion in wet milling, in addition to the actual and actual mechanical wear. Therefore, attempts have been made to use rubber to replace steel liners. In addition to good wear properties compared to steel, rubber has improved corrosion resistance and also a sound-absorbing effect during grinding. In addition, the rubber liner is significantly lighter than the steel liners. However, one disadvantage of rubber is its poorer durability withstands sliding wear than steel. In the case of conventional mill liners with longitudinal jacket plates and so-called hoists, i.e. lifting members, it is important that these jacks be replaced when they have been subjected to such severe wear that the charge begins to slide along the liner.

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When hoists are exposed to sliding wear, they are thus exposed to accelerating wear, and with it the intermediate jacket surfaces begin to wear rapidly. Therefore, in order to obtain an economically good inner liner, the hoists must be replaced at the right time, usually 3-4 sets of hoists are used for each replacement of the jacket plates. The lifts are changed at a time when the inner lining profile is better than in the new inner lining in terms of capacity and fine grinding properties. When changing hoists, the grinding capacity can often decrease by 10-20%.

The disadvantages of rubber hoists are thus that the grinding capacity will vary considerably over the lifetime of the hoists and that the hoists must be replaced when the inner lining profile is at its best; in other words, a run-in period with lower capacity and undesirable coarse waste in the outgoing ground material must be allowed. This is especially the case with fine grinding in mills where the speed is more than 75% of the so-called critical speed.

Replacing hoists and sheath plates costs quite a bit in the form of disassembly and installation, as well as downtime costs.

It would be of great advantage if the inner lining of the mill could wear out equally for the entire inner lining and that the service life could be extended to a period of 1 year or longer so that the necessary replacement could be carried out during normal downtime periods, i.e. during holidays.

In order to avoid the need for elevators in ball mills, Jorja Patent Publication No. 22,213 proposes that electromagnets be used during the rotation of the mill to raise the grinding balls of magnetic material to the required height and then lower them onto the material to be ground. According to this Norwegian patent publication, the electromagnets are arranged next to the outer side of the mill drum, which consists of lamellae of magnetizable material, the arrangement being such that the grinding balls are held against the mill drum only during raising to a suitable level.

In mills for non-magnetic powder, electromagnets have also been used to magnetically separate unwanted magnetic material in the powder. Such a 4 65389 magnetic separation device is described in German patent publication 4Θ2 59Θ. In this case, electromagnets are thus used not to replace the hoists but to separate the unwanted material and to ensure that this is fed out through the unwanted material outlet of the separating device.

It is an object of the present invention to improve the inner linings of known mills and to make it possible to prolong their service life.

Another object of the present invention is to provide a wear protection for walls which is self-maintaining, i.e. automatically renewed itself. .

It is a further object of the invention to provide the mill drum with devices which provide automatically renewable wear protection on the inside of the mill drum.

An increase in the rotational speed of the mill is many times desirable because the grinding capacity increases rapidly with the increased speed up to or above the so-called critical speed. At speeds of 80-85% or more of the critical speed, the liner profile may not comprise lifting members, but the liner must have a smooth inner surface. In connection with grinding, the inner liner will be exposed to sliding wear as a result, and accelerated wear will result. Extensive grinding experiments with secondary grinding (fine grinding1 at the so-called critical speed) have been shown to give quite good grinding results. However, this form of grinding has not been able to Another object of the invention is therefore to make it possible to limit this sliding consumption also in mills of this type.

In order to fulfill the above objects, the present invention therefore provides an abrasion-resistant wall which, in use, is exposed to the abrasive action of a particulate or particulate material containing magnetic particles. In this case, the side 65389 of the wall, which is at least subject to wear, is preferably formed of or upholstered with a wear-resistant wall material, e.g. in the form of sheath plates or hoists. According to the invention, the wall must have magnetic devices arranged so as to attract the magnetic particles contained in the charge and to keep them as an automatically regenerating wear layer on the surface exposed to wear, at least in areas normally subject to greater wear than other areas of the wall. characteristic features are set out in the claims.

When the invention is utilized in high speed mills with a smooth inner surface, harmful, sliding wear can be limited if, according to the invention, magnets are fitted to the smooth inner liner in a system that provides a fully covering mattress of magnetic particles that is held in place. magnetically in such a profile that the charge is raised to a suitable level for maximum grinding capacity. Abnormal frictional forces between the charge and the mill drum are received in this fluid bed, thus preventing excessive sliding directly against the inside of the inner liner.

When grinding a non-magnetic material, e.g. sulfide ores, if the invention is exploited, a magnetic material, e.g. magnetite, must be placed in the charge in order to obtain an automatically regenerating wear protection layer on the inner liner. The magnetic material should be relatively fine-grained (up to about 5 mm). Because the finer material settles next to the mill casing, the magnetic material is located in those areas with the inner liner that are coated with an automatically regenerating wear protection layer. Optionally, the magnetic residues that follow the outgoing ground material can be recovered by allowing the pulp, i.e., the finished ground material, to pass through a simple magnetic separation drum of conventional application at the exit of the mill. These residues can then be re-introduced into the grinding circuit or otherwise recovered.

A great advantage of the invention is that the magnetic circuit, when permanent magnets are used, will be permanently closed, on the one hand by the addition of a metal or a mill jacket drum and on the other hand by the magnets of the 6,638,39 magnetic particles and the fine-grained layer attracted. Today, this automatically provides good security against the loss of magnetization.

As mentioned above, it is known per se to use magnetism in connection with mill drums. The mill described in U.S. Pat. No. 3,913,851 holds the wear-resistant elastic liner of the mill in place on the inside of the mill by magnetism. In this case, it is thus the elastic inner liner itself that is held in place by magnetic forces, thus replacing the normal mechanical anchoring of the inner liner. There is no protected circuit at the side of the magnet mill away from the drum, and therefore the risk of gradual loss of magnetization is high. In contrast, the present invention is based on the realization that magnetism could be used to provide an automatically regenerating wear protection for the inside of a mill drum, which in itself may be formed of a wear-resistant material, e.g. an elastic material. The invention is thus based on another technical idea than the invention according to U.S. Pat. No. 3,913,851.

In the mill described in the above-mentioned Norwegian patent publication 22 213, iron grinding balls are lifted with respect to the material and then lowered onto the material to be ground, which will thus not follow the process of lifting in which the magnetic iron grinding balls are attracted. stationary electromagnets arranged against the inside of the mill drum outside the mill drum. In this known mill, the purpose of the electromagnets is different from that of the magnets in the wear-prone wall according to the invention, and a temporary interruption of magnetization is required to release the grinding balls so that they can fall into the material to be ground by gravity in the lower areas of the mill. along the diaper and then expose this to wear. This known mill therefore requires a lining of wear-resistant material, although the wear caused by the grinding balls themselves is reduced. Another object of the present invention is to provide a wear protection which protects the wall, in particular the wall of the mill, from sulfur wear and which automatically renews itself.

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The above and other objects and advantages of the present invention will become apparent from the following few preferred application examples shown in the accompanying drawings.

Figures 1-3 show three examples of a mill having a wall according to the present invention, and the figures show sections cut through a portion of a drum sold and through an inner liner attached thereto.

Figures 4 and 5 show another example of a mill with a wall according to the invention, Figure 5 showing a part along the line V-V in Figure 4.

Figures 6-9 show sections of another example of a mill with walls according to the present invention.

Figures 10 and 11 show examples of a standardized wall element utilizing the principles of the invention, with Figure 10 showing a cross-section along the line X-X in Figure 11 and Figure 11 showing a longitudinal section along the line XI-XI in Figure 10.

Fig. 12 shows a section corresponding to Fig. 10 when the standard element is mounted on the drum of the mill.

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Fig. 13 shows how the principles of the invention can be used to protect walls other than mill drums.

The mill shown in Figure 2 has a mill drum 10 with an inner liner clamped against the inside. This inner lining comprises sheath plates 11 made of wear rubber and having protruding fastening flanges 12. The inner lining also comprises hoists 13 comprising an elastic part or a rubber part 14 with an undercut groove 15 for interaction with an inserted metal rail 16 with bolts 17 fastened by welding. , which protrude through holes made in the mill casing and act together with the washer 1Θ and the nut 19. Bolts and rails can be replaced with T-bolts. The inner liner 11, 13 of the mill is thus held in place by tightening the protruding mounting flanges 12 of the jacket plates 11 against the mill jacket 10 by means of a metal rail 16 inserted inside the grooves 15 cut under the hoists. Other methods of attaching the inner liner are also within the scope of the invention.

According to the present invention, the lifters is provided with a further portion 20 on which is mounted a plurality of permanent magnets 21. The permanent magnets slightly protrude from the surface 13 of the lift of the percussion on the page, ie. front-facing sides when the mill rotates in the direction of the arrow 22. Sometimes, however, it may be advantageous to allow the permanent magnets to terminate immediately below the surface of the hoists. The permanent magnets 21 alternately turn outwards into plus and minus values and thus attract magnetic particles from the mill charge, so that these particles are kept as a layer 23. This layer then acts as an automatically regenerating wear layer for the lifts 13, as the charge encounters this layer and prevents -only to the lifts as if there were no layer 23. Although the magnetic particles in the layer 23 may come off when the charge encounters the layer 23, new magnetic particles in the charge will be replaced, so that the protective layer 23 is also maintained during the continued rotation of the mill drum.

In Figure 1, the automatically regenerating protective layer of magnetic particles is shown only with the left lifter, so that a comparison with conventional lifts can be better understood. The right-hand hoist shows with dotted lines t 100, 101, 102 and 103 how a conventional hoist made entirely of rubber material changed its profile during a long-term experiment in a mill where the principle of the invention was tested in addition to conventional hoists. The part 14 of the hoists 13, the jacket plates and the conventional hoists consisted of the same wear rubber material list. The mill has a diameter of 5.9 m and is continuously used for secondary grinding by means of lump-shaped magnetite and lump-shaped quartz in a mixture (particle size up to 60 mm), so-called "pebbles". Conventional hoists initially have the profile shown by line 100, while lines 101, 102 and 103 represent the residual profile of the remaining hoists after 7 months, 14 months and 21 months of continuous use, respectively. Once the profile 103 was reached, i.e. after 21 months, it was time to insert new conventional lifts. After the same period of time, the rubber part 13 with the hoists 13 provided with permanent magnets 21 had worn only to a small extent, as indicated by the broken line 14 'on the right-hand hoist in Fig. 1.

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During the test period, it was found that the automatically regenerating wear protection layer 23 was not completely homogeneous, but comprised an inner, per se homogeneous layer 23 'of very fine-grained magnetic material and an outer inhomogeneous layer 23' of coarser magnetic mineral granules and highly worn magnetite ore.

The tests carried out show that the invention provides a very substantial improvement in the service life of the inner liner of the mill by providing an automatically regenerating wear protection layer 23 of magnetic, fine-grained material contained in the charge.

Figure 2 shows another example of how the invention has been shown to be applicable to protect a mill drum from wear. In this case, the mill is formed as a primary mill, i.e. a mill for grinding coarse outlet material. The inner lining of the mill is in this case formed corrugated so that the jacket plates 24 are formed in a stepped manner with a low portion 25 and a high portion 26, which, however, is lower than the upper side of the elevators 27. The fastening of the hoists and the jacket plates is carried out in substantially the same way as in Figure 1. However, in the embodiment according to Figure 2, in addition to the hoists 27, the jacket plates 24 were also provided with a metal insert 20 and permanent magnets 21 attached to them. As a result, higher level permanent magnets layer 23 of magnetic particles attracted by the permanent magnets in the same manner as in Fig. 1. Also in this case, it turned out that the protective layer 23 had a layer-like structure with an inner fine-grained sublayer and an outer coarser coarse sublayer. Layer 25 had a thickness of about 5 cm in a 2.9 m diameter mill at the time of the experiment and came to comprise a set of worn grinding balls. Layer 23 formed a floating joint mattress that provided effective protection against abrasion of the inner liner.

Figure 3 shows a further application example in which the lifts 28 are made of a rubber or elastic material and fused together into a metal plate 29 projecting in both directions. These hoists are held in place by a rubber or elastic element 30 with a vulcanized metal profile 31 which acts together with T-bolts 32, washers 33 and nuts 34 and tightens the metal plate 29 against the mill drum 10. As in the previously described embodiments, the lifter 2B has vulcanized permanent magnets 21 mounted on metal attachments 20 and retaining a regenerable protective layer 23 formed by attracting the magnetic particles in the mill charge and retaining the permanent magnets 21 in this case. positioned in such a way that the protective layer 23 also extends the distance of the piece forward of the actual hoist, and thus also protects the low part in front of the hoist where high wear normally occurs.

Figures 4 and 5 show another embodiment of the invention, in which the lifts are formed in a different way and provided with a protective plate. The mill drum 10 is thus coated with a jacket plate 35 connected to metal plates 36 projecting in both directions. Between successive sheath plates 35 are hoists 37 with an outer protective sheath 30 of non-magnetic, wear-resistant metal material. Inside the metal shield 30, there are permanent magnets 21 attached to an insert 20 formed of a magnetic metal material. The permanent magnets and the insert are held in place by a polyurethane rubber layer 39. Other plastic or elastic materials are also conceivable. The hoists are then held in place by an inserted profile rail 40 which is held tensioned against an undercut groove formed in the hoists by means of bolts 41 and nuts 42 projecting out through the mill jacket 10. The permanent magnets 21 are arranged with their plus and minus poles as shown in the drawings, so that a protective layer 23 of magnetic particles from the charge will form on the outer side of the shield 30.

The hoists 37 can be formed relatively short, e.g. 100 mm, whereby the required total hoist length is obtained by placing several hoists in succession and holding them by means of a common mounting rail 40 or by means of several such successive mounting rails. This embodiment is intended in particular for use in rod grinding, i.e. grinding in mills using rod-like grinding pieces and where there is a risk that worn, spear-like rod ends will penetrate and damage the hoists. The magnetic system 65389 is formed symmetrically, which means that the direction of rotation of the mill can be changed.

Figure 6 shows a corresponding embodiment with the permanent magnets arranged symmetrically. In this case, the lifter 43 formed of rubber or other elastic material has a metal profile 44 impregnated with an undercut groove 45 for interaction with the T-bolts 32 and nuts 34. The hoists tighten the sheath plates 35 by means of vulcanized metal plates 36 attached to the sheath plates.

In the embodiment according to Fig. 6, the permanent magnets 21 are attached to the additional part 20, and their · active pole surfaces are at the bottom of the conical notches 4Θ. As a result, the magnetic material contained in the exhaust will fill these conical notches and thus act as a renewable protective layer outside the permanent magnets and also outside the rubber or elastic parts of the lifter 43. Also in this case, the lifter is symmetrical, so that the direction of rotation of the mill can be changed.

In connection with the previously described embodiments, permanent magnets have been used to form a regenerable 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 shield made of non-magnetic material, embedded magnetic steel plates 49 are used, which act as pole plates with electromagnets 50 attached to the magnetic insert 20. The magnets 50, the insert 20 and the pole plates 49 are cast to 39 between the pole plates 49. The electromagnets 50, which are connected to a power source (not shown) via wires (not shown), form a renewable protective layer 23 of magnetic particles contained in the charge. Also in this case the lifter is symmetrical so that the direction of rotation of the mill can be changed.

A major advantage of the disclosed embodiments in which the magnets are attached to an elastic, plastic or rubber material in a vulcanized insert is that the magnets are therefore held elastically and thus better able to withstand possible strong impacts from the large pieces of material 12 included in the charge. 65389

Figures Θ and 9 show another embodiment of a wall according to the present invention used in a ball mill. The inner liner is made of two types of standard elements, one type corresponding to jacket plates and the other type corresponding to "hoists", although this mill does not have lifting members projecting inside the mill. The elements 51 corresponding to the jacket plates have vulcanized metal plates 52 on the mantle side 10 of the mill, and the rubber part 53 of the element extends by a layer 54 over these metal plates. The elements 51 are vulcanized with permanent magnets 21 and thus a metal core 20 acting as a magnetic core is connected to it. Protective plates 55 formed of non-magnetic metal material are attached to the outside of the permanent magnets 21 to protect them. The elastic material portion 53 of the sheath elements 51 has a strip-like protrusion 56 between the rows of permanent magnets to cause the particle layer forming the protective layer 23 to curl upwardly between adjacent magnets and to reduce the risk of the protective layer 23 slipping inside during the initial construction phase.

The wall elements 57 corresponding to the elevators similarly have permanent magnets 21, a metal insert 20 and protective plates 55 which, together with a metal profile bar 5Θ with an undercut groove 59, are vulcanized or cast inside the elastic part 60 of the wall elements 57. The elastic portion, which may be formed of polyurethane rubber, extends through the layer 61 below the portion of the metal profile bar 58 and has a strip-shaped protrusion 62. The wall elements 57 are secured to the sheath drum 10 by T-bolts 46 and nuts 47 and thus firmly tighten the sheath plate 51.

In the illustrated embodiment, the elements 51 and 57 are each made up of four permanent magnets 21 and two metal attachments 20, so that the elements are relatively small and easy to handle during installation. They can, of course, be made to an arbitrary length.

In the embodiment according to Figures Θ and 9, a uniform and approximately uniformly thick protective layer 23 of magnetic particles contained in the powder material is held against the inner liner. In the embodiment shown, the sheath plates 5T have only 13 65389 two rows of permanent magnets 21, but if the sheath plates are formed wider, of course even more rows of magnets can be placed next to each other.

Figures 10-12 show an inner liner formed from standard elements used in a mill. The standard elements 63, which are made with the mold shown in Figures 10 and 11, have an elastic material 64, preferably polyurethane rubber. permanent magnets 21 molded into a suitable plastic material so that the elastic material forms protrusions 65 in which elongate V-shaped notches 66 are formed. The elastic material leaves the other side of the permanent magnets free so that the magnets protrude somewhat from the elastic material. However, it is possible to allow the magnets to protrude out of the elastic material also on the opposite long side. Thus, in this embodiment, there is no metal insert made of magnetic material molded into the elastic material, but the magnetic circuit between the permanent magnets is instead closed by a metal wall, in this case by means of a mill drum provided with a wear layer. This can be seen from Figure 12. In this embodiment, magnetism is thus used not only to provide a protective layer 23 of magnetic particles but also to hold the inner liner firmly against its substrate. The fitting of the elements 63 to the arcuate shape of the mill drum is facilitated by notches 66 and bridges 67 of elastic material remaining below them, which act as elastic springs. The standard elements 64 are formed asymmetrically to facilitate the correct orientation of the elements and to facilitate the correct orientation of its permanent magnets with respect to adjacent elements.

The invention has been described above in connection with rotating mill drums, but it is understood that the invention can also be used for vibrating mills and also for protecting wall surfaces other than mill casings.

The invention is thus applicable to many different types of walls which are exposed to the consumption of material containing magnetic particles which can form the desired, automatically regenerating protective layer. As an example 14 65389 of this, Fig. 13 shows a discharge station 69 of a conveyor belt 70 for conveying particulate material, which material contains magnetic particles, e.g. magnetite concentrate. Figure 13 is only schematic, and the wall elements 68 may preferably be formed according to Figures 10 and 11, although protrusions 65 may not be required. Alternatively, the wall elements may be formed as shown in Figures 8 and 9. As shown in Figure 13, for the most exposed parts of the unloading station 69 and parts of the downhill chute 71, the mouth of which may be above the auxiliary conveyor 72, the carriage, the cargo container, the screen or the like.

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Claims (9)

1. A wall which has magnetic devices (21.50) and which in use is subjected to abrasion of piece or particulate goods comprising magnetic particles, characterized in that the magnetic devices (21.50) are arranged within at least such zones of the surface exposed to abrasion, which are normally subjected to more severe abrasion than other zones of the wall, and are arranged to attract and, as an automatically renewable abrasion protection layer (23), retain magnetic particles in the goods. Wall according to claim 1, characterized in that the magnetic devices (21,50) are embedded in the wall. A wall according to claim 1 or 2, designed as a mill wall with lifters (13,27,2Θ, 37,43), characterized in that the magnetic devices (21,50) are arranged to attract the magnetic particles contained in the goods at least In the iupt's buttocks side. i! IN 4. A wall according to claim 1, 2 or 3, formed as a mill casing wall, characterized in that the magnetic devices (21,50) are arranged at intervals along the entire surface of the wall (57,63) so that, when using the mill, it is covered with it. automatically renew the wear protection layer (23). Wall according to any of claims 1-4, characterized in that the magnets (21) of the magnetic devices are arranged with their active pole surface at the bottom of crater-shaped recesses (48) in the wall (43). Wall according to any of claims 1-5, characterized in that the magnets of the magnetic devices (21.50) are permanent magnets (21). 7. Wall according to any of claims 1-5, characterized in