Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C15/00—Disintegrating by milling members in the form of rollers or balls co-operating with rings or discs
  • B02C15/004—Shape or construction of rollers or balls
  • B02C15/005—Rollers or balls of composite construction
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C4/00—Crushing or disintegrating by roller mills
  • B02C4/28—Details
  • B02C4/30—Shape or construction of rollers

Definitions

• the present invention relates to a grinding roller for vertical axis mills used for grinding materials such as rocks, coal, cement clinker or other related material such as slag.
• These rollers are particularly wear-resistant thanks to specially shaped reinforcing inserts placed near the working surfaces of the roller, allowing uniform and constant wear over the entire work surface and thus longer service life.
• Grinding rollers for vertical axis mills are well known to those skilled in the art. They are generally made of relatively ductile cast iron in which inserts made of extremely wear-resistant materials, usually chromium cast iron, sometimes including ceramic grains, are included to reinforce the most stressed surfaces during grinding.
• EP 1570905A1 discloses a grinding roller comprising a plurality of peripheral inserts made of material with high wear resistance and high hardness, mechanically sealed in a cast matrix of ductile material with first zones subject to a high stress of wear. as well as second zones subject to low wear stress.
• the roller presents on its peripheral face inserts comprising a contiguous part, and in the second zone, a non-contiguous part.
• WO 9605005 discloses a bimetallic casting part mounted on the hub of a vertical axis milling roller. It comprises a core made of a ductile iron provided with mechanical connection elements in the form of studs which are made integral by casting a casing, made of a non-ductile wear material with a high chromium content.
• WO 2015 / 162047A1 discloses a grinding roller with high mass inserts embedded in a metal matrix composed of ductile iron and steel, the roller comprising inserts with a V / S massivity module of between 3 and 5 cm. Goals of the invention
• the present invention provides a roller reinforced by inserts whose profile has a particular design that causes constant wear of the entire working surface of the roller avoiding local occasional wear. These rollers allow to maintain the performance of the mill to a satisfactory level while minimizing the risks of breakage and reducing manufacturing costs.
• the present invention discloses a grinding roller for a vertical axis mill produced by casting a metal matrix casting, said roller having in its periphery a plurality of reinforcing inserts, including portions of the peripheral surface of the same insert is located at a distance d1 or d2 from the working surface depending on the stresses to wear, said roller comprising:
• the roller comprises at least one or a suitable combination of the following characteristics:
• the roller comprises at least one intermediate zone Z3 connecting the zones Z1 and Z2;
• d1 is less than 10 mm, preferably less than 5 mm and d2 is greater than or equal to 10 mm, preferably greater than 20 mm;
• the roller comprises two zones of high stress Z1 located on either side of a zone of low stress Z2 for a roller for symmetrical use;
• the inserts have on the face facing the work surface ceramic reinforcements
• the inserts contain up to 60% by volume of ceramic grains
• the ceramic grains comprise alumina, zirconia, alumina-zirconia and / or metal carbides;
• the roller is of frustoconical shape.
• Figure 1 shows an example of a vertical axis mill.
• Figure 2 shows a roller with inserts at the periphery and ceramic reinforcements included in these inserts work surface side according to the state of the art.
• Figure 3 shows schematically the grinding mechanism in a vertical axis mill with its turntable and a layer of material to grind.
• Figure 4 shows different examples of embodiments of the invention according to different forms of rollers.
• Figure 5 shows a section of an asymmetrical roller with its different biasing zones, the distances d1 and d2 representing unreinforced thicknesses between the work surface and the insert.
• the distance d1 has been exaggerated with respect to reality.
• Figure 6 shows a section of a symmetrical roller with its different biasing zones, the distances d1 and d2 representing unreinforced thicknesses between the work surface and the insert.
• the distance d1 has been exaggerated with respect to reality.
• Figure 7 shows a grinding roller having an insert without a transition zone between a zone of high wear stress Z1 and a zone of low wear stress Z2.
• Figure 8 shows a symmetrical grinding wheel of the same type as that shown in Figure 6 but which is reinforced only one side and is therefore supposed to be used only one side.
• Z1 Area of maximum stress to wear at the beginning of the use of the roller.
• Z3 Transition zone between zone Z1 and zone Z2.
• d1 distance between the original working surface (new peripheral surface of the roller, not yet used) and the reinforcement insert in zone Z1.
• d2 distance between the original working surface (new peripheral surface of the roller, not yet used) and the reinforcement insert in zone Z2.
• Vertical axis mills are known to those skilled in the art. There are different types and they generally have a table rotating about a vertical axis on which the material to be grinded is fed.
• the mill is equipped with a plurality of very heavy wheels of generally cylindrical or frustoconical shape, called “rollers”, which are positioned above the table. As the table rotates, the material to be ground is driven outwardly by the centrifugal force and passes between the rollers and the table.
• the self-weight and a vertical force applied to the rollers cause compaction and grinding of the bed of material passing below the rollers.
• This material itself serves as a frictional connection between the table and the rollers, so that the rotation of the table causes the rotation of the rollers or vice versa. Grinding in the material bed is by compression and shearing of the material.
• the compressive stresses and the relative speeds between the rollers and the table vary over the width (the thickness) of the roller.
• the level of compressive stress depends on the height of the bed of material and the spacing between the rollers and the table over the width of the roller.
• the wear of the rollers and shields of the table is an inevitable consequence of the grinding process. Manufacturers of vertical axis mills therefore optimize the shapes of the rollers and tables according to the materials to be milled, which makes it possible to obtain an optimum grinding efficiency when the grinding equipment is new.
• the level of wear is not constant over the width of the roller. Over time, more marked wear zones are formed along the generatrix of the rollers, which cause a drop in grinding efficiency and ultimately require the rollers to be replaced.
• This drop in performance is explained by the very operation of a vertical mill.
• This comprises a mechanical safety stop preventing the work surface of the grinding roller from coming into contact with the table.
• this stop is set to provide a safety clearance of about 10 mm between the table and the work surface of the grinding roller.
• EP 1570905A1 discloses a grinding roller comprising a plurality of peripheral inserts made of a material with high wear resistance and high hardness, mechanically sealed in a cast matrix of ductile material with first zones subject to high wear stress, and second areas subjected to low wear stress. In the first zone, the roller presents on its peripheral face inserts comprising a contiguous part and in the second zone, a non-contiguous part. This proposal does not give the expected results, especially for cement crushers.
• the intensity of wear on a roller of a vertical axis mill mainly depends on the abrasiveness of the material, the pressure applied locally and the relative speed between the surface of the roller and the material to be ground. As the mill rotates, the material builds up on the outside of the turntable, resulting in a much greater wear stress on the outer portion of the work surface of the milling roller (see Figure 3). . This is the reason why this part must be particularly reinforced by inserts.
• the invention discloses grinding rollers whose metal matrix is a relatively ductile material such as a GS cast iron or a mild steel. These rollers are provided with a plurality of high-wear inserts distributed over the entire periphery near the work surface of the roller (see Figure 2).
• the originality of the grinding roller according to the present invention lies in the design of the inserts which are profiled such that a portion thereof is in the immediate vicinity, or even flush with the work surface (at the new condition of the roller) at the places of strong stress, and another part set back from the working surface (in new condition of the roller) in the areas of least stress.
• This original distribution of reinforcement makes it possible to ensure more constant wear over the entire width of the working surface of the grinding roller.
• the distance between the portion of the insert near the working surface and the actual working surface in the area of high stress (Z1) is defined by d1.
• the distance between the portion of the insert set back from the working surface and the working surface itself in the zone of low stress (Z2) is defined by d2, the distance d1 in the zone of strong stress (Z1) being always less than d2 in the zone of low stress (Z2).
• d1 d2.
• the concept "flush with the work surface” must however be relativized knowing that the size of grinding rollers whose diameter is sometimes close to three meters for a mass of 15 tons.
• the distance d1 is generally less than 10 mm, preferably 8 mm or even 5 mm or less depending on the practical conditions of the casting.
• the portion of the outer surface of the insert which is set back from the working surface of the grinding roller is at a distance d2 generally greater than 10 mm, preferably greater than 15 mm and particularly preferably greater than 10 mm. 20 mm.
• the inserts will often have a transition zone (Z3) joining the nearby portions and those set back from the work surface. These portions correspond to a zone (Z3) where the outer surface of the insert progressively moves away from the working surface of the roller in new condition.
• the ductile material filling the volume between the outer surface of the inserts and the original surface of the roller thus has a variable thickness on the thickness of the roller.
• the presence of a transition zone Z3 is not always necessary and in some cases, the area of high wear stress Z1 can pass without transition to a zone of low wear stress Z2 ( see Figure 7).
• the roller will therefore have two areas on its working width, the zone 1 (Z1) being subjected to a strong stress where the outer surface of the insert will be closest or flush with the work surface (original profile) of the roller, the zone 2 (Z2) being subjected to a low stress where the outer surface of the insert will be furthest away and set back from the working surface (original profile ) of the roller (peripheral surface).
• the rollers will often have a transition zone 3 (Z 3) corresponding to an average stress intensity where the distances d 1 and d 2 meet.
• the distances d1 and d2 are not necessarily totally constant but may vary slightly with the difficulties encountered in placing the inserts in the molds during the preparation of the casting.
• the invention aims to accelerate wear in the zones 2 and possibly 3, which has the consequence that the wear gradient between the zone 1 and the rest of the thickness of the pebble is lower.
• the rollers can thus keep a profile closer to the original profile and therefore have a longer life.
• the observed increase in life is between 0 and 80%, preferably between 30 and 70%. The most significant improvements have been observed on frusto-conical models.
• the grinding rollers which have an axial symmetry with a generator of revolution giving rise to a roller type "cylinder” or “tire” (see Figure 4) are used on both outer peripheral faces and can be returned (by for example, rollers for RM type mill).
• the inserts may contain ceramic grains (oxides, carbides, nitrides or metal borides, intermetallic compounds) in order to improve the resistance to wear.
• these grains will be arranged in the part of the insert which is closest to the peripheral (original) surface of the roller in zone Z1.
• the arrangement of the ceramic grains is preferably in the form of infiltrable slab by melting of the casting. The slabs are preformed to a desired section and placed in the mold before casting.

Landscapes

• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Crushing And Grinding (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Grinding Of Cylindrical And Plane Surfaces (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2016
  • 2016-10-12 EP EP16193517.6A patent/EP3308861A1/de not_active Withdrawn
• 2017
  • 2017-09-20 MX MX2019004261A patent/MX2019004261A/es unknown
  • 2017-09-20 BR BR112019006614A patent/BR112019006614A2/pt unknown
  • 2017-09-20 DK DK17768810.8T patent/DK3525934T3/da active
  • 2017-09-20 US US16/341,375 patent/US11123742B2/en active Active
  • 2017-09-20 ES ES17768810T patent/ES2965916T3/es active Active
  • 2017-09-20 PT PT177688108T patent/PT3525934T/pt unknown
  • 2017-09-20 KR KR1020197010265A patent/KR20190065283A/ko not_active Application Discontinuation
  • 2017-09-20 CN CN201780058615.1A patent/CN109843442B/zh active Active
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  • 2017-09-20 RU RU2019113884A patent/RU2730026C1/ru active
  • 2017-09-20 WO PCT/EP2017/073701 patent/WO2018069006A1/fr unknown
  • 2017-09-20 CA CA3036461A patent/CA3036461A1/en active Pending
  • 2017-09-20 EP EP17768810.8A patent/EP3525934B1/de active Active
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• 2019
  • 2019-03-26 ZA ZA2019/01867A patent/ZA201901867B/en unknown
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