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
  • B02C13/00—Disintegrating by mills having rotary beater elements ; Hammer mills
  • B02C13/14—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices
  • B02C13/18—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor
  • B02C13/1807—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor the material to be crushed being thrown against an anvil or impact plate
  • B02C13/1835—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor the material to be crushed being thrown against an anvil or impact plate by means of beater or impeller elements fixed in between an upper and lower rotor disc
  • B02C13/1842—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor the material to be crushed being thrown against an anvil or impact plate by means of beater or impeller elements fixed in between an upper and lower rotor disc with dead bed protected beater or impeller elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C13/00—Disintegrating by mills having rotary beater elements ; Hammer mills
  • B02C13/14—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices
  • B02C13/18—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor
  • B02C13/1807—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor the material to be crushed being thrown against an anvil or impact plate
  • B02C13/1814—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor the material to be crushed being thrown against an anvil or impact plate by means of beater or impeller elements fixed on top of a disc type rotor
  • B02C13/1828—Disintegrating by mills having rotary beater elements ; Hammer mills with vertical rotor shaft, e.g. combined with sifting devices with beaters rigidly connected to the rotor the material to be crushed being thrown against an anvil or impact plate by means of beater or impeller elements fixed on top of a disc type rotor with dead bed protected beater or impeller elements

Definitions

• the invention relates to a centrifugal mill with a centrifugal mill rotor, which is rotatably mounted in a centrifugal mill housing about an axis of rotation in a working direction of rotation and has a plurality of centrifugal chambers, each of the centrifugal chambers being assigned a centrifugal scoop along which the material to be ground during operation of the centrifugal mill due to centrifugal forces a radially inner feed material moves to a radially outer tear-off edge at which it emerges from the centrifugal mill rotor, each centrifugal vane comprising a vane wall with a radially inner end edge and a radially outer end edge, and a wear unit attached to the radially outer end edge of the vane which the tear-off edge is arranged, the blade wall being curved and assigning its concave surface to the regrind moving along it.
• a curved course does not necessarily mean a curved, for example circular, curved course, but rather also a polygonal course. This means that it is possible, for example, to assemble the curved blade wall from a plurality of flat blade wall plates.
• centrifugal mill is known for example from the prospectus of the applicant "BHS rotor mills”.
• the applicant has for the first time given the task of improving the mill feed area with regard to the energy consumption and wear of the centrifugal mill and its grinding result.
• centrifugal mill of the type mentioned at the outset, which has exactly two centrifugal chambers, and in which the radially inner end edges of the blade walls of the two centrifugal blades when the two tear-off edges are connected to one another and the central perpendicular is formed on this connecting line in which Is arranged near this perpendicular line, the radially inner end edge of each blade wall preferably being arranged, starting from the radially outer end edge thereof, in an angular range from approximately 20 ° in front of the central line to approximately 20 ° in the vertical line.
• the applicant has overridden a prejudice prevailing in the professional world, according to which the centrifugal mill rotor should have at least three, better still at least four centrifugal chambers, since the grinding stock is distributed over as large a number of centrifugal chambers as possible from each of the skidding shovel only a correspondingly small amount of regrind needs to be accelerated towards the tear-off edge.
• this has a favorable effect on the wear of the centrifugal mill rotor and, on the other hand, ensures that each regrind particle is accelerated along essentially the same conditions along the centrifugal scoop to its tear-off edge, according to the opinion prevailing in the specialist world.
• a centrifugal mill according to the invention is generally designated 10, the centrifugal mill housing 12 and the centrifugal mill rotor 14 being shown only roughly schematically.
• the baffle 20 can, as shown for example in the brochure "BHS rotor mills", either be formed by a plurality of baffle plates made of wear-resistant material (see page 6 of the brochure) or alternatively by a material bed made of ground material that has already been crushed (see page 8 of the prospectus).
• the coordinate system [x, y] according to FIG. 2 is one with respect to the mill housing 12 and thus with respect to an external observation. aft fixed coordinate system. 2 therefore shows the absolute movement of the regrind particle 1 6 in the mill housing 12.
• the representation of the movement of the regrind particle 1 6 in this co-rotating coordinate system [x ', y'] is therefore particularly suitable for demonstrating relative movements of the regrind particle 1 6 with respect to the rotor 14.
• it is precisely these relative movements that are necessary for the intake of the regrind, i.e. the transition of the regrind particles 1 6 from the feed plate 18 into the centrifugal chamber 22 delimited by the centrifugal scoop or the centrifugal arm 24 is of crucial importance.
• This movement phase ends when the particle 16 hits the material bed 26 which forms when the centrifugal vane 24 rotates and protects the vane wall 28 from wear.
• the particle 16 is braked when it is drawn in and its relative speed with respect to the centrifugal blade 24 is reduced to zero.
• the particle 1 6 is pre-shredded.
• the particle 16 or its fragments is accelerated radially outward along the surface 26a of the material bed 26 until it leaves the rotor 14 at the tear-off edge 30 of the centrifugal vane 24 at point C and is accelerated to the baffle 20. In the event of an impact against the impact wall 20, the main comminution of the particle 1 6 takes place.
• the probability of drawing in compared to the probability of reflection can be increased in a simple manner by increasing the length of the peripheral section between two successive centrifugal blades 24 relative to the peripheral length of the reflection surface 26b. This can be done in a particularly effective manner by moving from a three-chamber mill, as shown in the brochure "BHS rotor mills", to the two-chamber mill according to the invention.
• the range of possible impingement points of the particles 16 on the material bed surface 26a of the centrifugal blade 24 is also increased at the same time.
• the exit velocity of the particles would also have been due to the different path over which the particles 16 can be accelerated towards the tear-off edge 30 along the remaining length of the material bed surface 26a 1 6 from the rotor 14 and thus their kinetic energy must vary to a great extent, which would inevitably also have had a negative effect on the result of the comminution.
• the position of the radially inner end edges of the vane walls of the two centrifugal blades in the two-chamber centrifugal mills according to the invention proves to be an essential feature for the quality of the grinding result. If this radially inner end edge is too close to the associated radially outer end edge of the blade wall, it can happen that regrind fed onto the distribution plate 18 emerges from the centrifugal rotor 14 without ever having come into contact with a centrifugal blade 24. These uncontrolled regrind particles 16 understandably impair the quality of the comminution result to a considerable extent.
• the radially inner end edges of the blade walls are arranged in the vicinity of the central perpendicular to the connecting line of the tear-off edges of the two centrifugal blades, preferably in an angular range from approximately 20 ° to approximately 20 ° after this central perpendicular.
• a blockage of the regrind supply can also be prevented by arranging the radially inner end edge of each blade wall at a radial distance from the axis of rotation that is at least about 30%, preferably at least about 40%, of the radial distance of the tear-off edge of the blade wall from the axis of rotation ,
• the convex surfaces of the blade walls form the outer surface of the centrifugal mill rotor
• the wear occurring on the outer surface of the centrifugal mill rotor can be reduced as a result of regrind moving back radially inward from the baffle wall, since the distance between the outer surface the centrifugal mill rotor is larger than the distance of the tear-off edges from the baffle by this design measure on a considerable part of the rotor circumference.
• a substantial amount of the regrind that moves back from the baffle wall radially inward can drop down due to gravity before it hits the outer surface of the centrifugal mill rotor and causes wear there.
• the tear-off edge can be provided adjacent to or above and / and below the associated grinding material outlet opening of the centrifugal mill rotor, preferably with striking surfaces pointing essentially orthogonally to the circumferential direction, which are preferably made of low-wear material. With their striking surfaces, these striking elements can grind and shred regrind that moves back radially inwards from the baffle.
• the radially inner end edges 32 of the centrifugal blades are also one Wear due to collisions with regrind particles 1 6 exposed. It is therefore proposed in a development of the invention that wear elements are also provided on the radially inner end edges 32 of the blade walls 28.
• US 4,690,341 discloses a three-chamber centrifugal mill and a four-chamber centrifugal mill as well as a two-chamber centrifugal mill as a possible embodiment variant.
• the known two-chamber centrifugal mill differs from the two-chamber centrifugal mill according to the invention, however, in a number of operationally essential features, which will be explained in more detail below with reference to FIG. 6.
• This FIG. 6 is the result of a minor addition to FIG. 4 of US 4,690,341.
• the reference symbols according to US 4,690,341 will therefore be used:
• the outer surface of the rotor of the known two-chamber centrifugal mill is essentially circular-cylindrical.
• this circular cylinder shape As small as possible
• the grinding material outlet openings adjoining the tear-off edges 86 are also very small.
• the blade walls 56 and 58, to which the wear units 80 carrying the tear-off edges 86 are fastened run along chords of the circular cylinder, ie in a straight line from a first point on the outer circumference of the rotor to a second point on the outer circumference of the rotor.
• the following walls 34 are also provided on the outer circumference of the rotor, on which wear plates 44 are attached, which protect the rotor against regrind from the impact wall.
• This embodiment of the rotor as a closed rotor has various disadvantages compared to the embodiment of the rotor as an open rotor according to the invention.
• the opening angle ⁇ of the logarithmic spiral which forms on the surface 26a of the material bed 26 now depends in practice on the properties of the ground material. If, for example, the centrifugal mill is loaded with moist sand with a water content of about 15% for sand finishing, an opening angle of the logarithmic spiral of about 25 ° is established. On the other hand, when crushing relatively round gravel, the opening angle is between about 35 ° and about 45 °, while when crushing pre-broken chippy material it is between about 45 ° and about 55 °. If one now examines the two-chamber centrifugal mill known from US Pat. No.
• a base plate 40 with a roughly "mirrored S" shape can be seen.
• the blade walls 28 of two centrifugal blades 24 are arranged, for example welded, on this base plate 40.
• the radially outer end 28a of these blade walls 28 is designed to be particularly wear-resistant and also carries a wear unit 42 on which a wear element 44 carrying the tear-off edge 30 is arranged.
• the wear element On the right-hand centrifugal vane 24 in FIG. 1, the wear element is shown in its worn state 44 'with the corresponding position 30' of the tear-off edge.
• a wear element 46 is also shown on the radially inner end 28b of the centrifugal wall 28, the worn state of which is again indicated by 46 '.
• FIG. 1 the courses of the logarithmic spirals of the surfaces 26a of the material bed 26 are shown both for the unworn state and for the worn state of the centrifugal blades 24, specifically for a material with an opening angle of 25 ° (moist sand) and on the other hand for a material with an opening angle of 45 ° (pre-broken split material).
• the blade wall 28 is always reliably protected from wear by the material bed 26, since it assigns its concave surface 28c to it, and that only the wear parts 44 and 46 intended for this purpose are exposed to wear are.
• These wearing parts 44 and 46 can, however, be replaced in a simple manner if required, the transition from the three-chamber construction to the two-chamber construction further improving the accessibility of these wearing parts.
• FIG. 1 also shows that the radially inner end 28b of the blade wall 28 is arranged in the vicinity of the perpendicular perpendicular M on the connecting line V of the tear-off edges 30 of the two centrifugal blades 24 is.
• the radial distance of the inner edge 32 of the wear element 46 from the axis of rotation X is denoted by d in FIG. 1.
• the striking elements 50 arranged in the region of the tear-off edge 30 can be seen with their striking surface 50a.
• FIG. 1 also shows the enormous width of the outlet openings 52 in comparison with the US Pat. No. 4,690,341, in which there is evidently no risk of these outlet openings 52 becoming blocked.

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• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Crushing And Pulverization Processes (AREA)
• Milling Processes (AREA)
• Crushing And Grinding (AREA)
• Signal Processing For Digital Recording And Reproducing (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7663911

Family Applications (1)

Country Status (4)

Cited By (3)

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Family Cites Families (3)

• 2000
  • 2000-11-20 DE DE10057433A patent/DE10057433A1/de not_active Ceased
• 2001
  • 2001-11-19 AT AT01985818T patent/ATE294642T1/de active
  • 2001-11-19 DE DE50106140T patent/DE50106140D1/de not_active Expired - Lifetime
  • 2001-11-19 WO PCT/EP2001/013368 patent/WO2002040166A2/fr not_active Application Discontinuation
  • 2001-11-19 EP EP01985818A patent/EP1335794B1/fr not_active Expired - Lifetime

Non-Patent Citations (1)

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