Attrition mill
AssigneesMount Isa Mines Limited, Erich Netzsch GmgH & Co. Holding KG
InventorsPeter Woodall, Udo Enderle
Life of this patent
Estimating the term…
Abstract
An attrition mill comprising a grinding chamber (1), an axial impeller (10), a chamber inlet (3) for admitting coarse particles and a separator comprising a chamber outlet (6) through which fine particles exit from the chamber. The mill is characterized in that a classification as between coarse and the fine particles is performed in the mill upstream of the separator.
Claims36
An attrition mill apparatus comprising:
- a grinding chamber (1) having a grinding stage or stages ("GS");
- one or more inlets (3) for admitting into the apparatus a coarse grinding medium, a slurrying liquid, and a substance to be ground;
- an apparatus outlet (6);
- an axial impeller (10) disposed in the grinding chamber (1) and adapted to cooperate with a slurry of the medium to reduce the particle size of the substance to fine particles;
- a classifier ("CS") within the grinding chamber for classifying particles in the slurry on the basis of particle mass so that a slurry of fine particles flows to said apparatus outlet and discharges from the mill while coarse particles return to the grinding stage or stages ("GS");
- and
- wherein the fine particles pass from the classifier ("CS") to said outlet (6) via at least one passage selected from the group consisting of at least one screened passage (24) and at least one unscreened passage (25), said at least one passage having a minimum passage dimension which is not only greater than the dimension of fine particles discharged, but also is greater than the D50 dimension of the equilibrium grinding medium retained in the mill.
A method for classifying particles in a slurry, comprising a substance to be ground, in an attrition mill having one or more inlets, an apparatus outlet (6), a grinding chamber having a grinding stage or stages ("GS"), an axial impeller (10) disposed in the grinding chamber and adapted to cooperate with a slurry of coarse grinding medium to reduce to fine particles the substance to be ground, comprising the steps of:
- admitting the slurry to a passage (19) having a passage inlet (15A) and a passage outlet (32) disposed opposite or radially inwards of the passage inlet (15A),
- rotating the slurry in the passage about the impeller axis, and
- selecting the velocity of rotation of the slurry having regard to the mass of coarse and fine particles in the slurry to separate the coarse particles from the fine particles so that slurry exiting from the passage outlet contains the fine particles and is substantially free of coarse particles.
A method for classifying particles in a slurry, comprising a substance to be ground, in an attrition mill having one or more inlets, an apparatus outlet (6), a grinding chamber having a grinding stage or stages ("GS"), an axial impeller (10) disposed in the grinding chamber and adapted to cooperate with a slurry of coarse grinding medium to reduce to fine particles the substance to be ground, comprising the steps of:
- admitting the slurry to a passage (19) having a passage inlet (15A) and a passage outlet (32) disposed opposite or radially inwards of the passage inlet (15A),
- rotating the slurry in the passage about the impeller axis, and
- selecting the velocity of rotation of the slurry having regard to the mass of coarse and fine particles in the slurry to separate the coarse particles from the fine particles so that slurry exiting from the passage outlet contains the fine particles and is substantially free of coarse particles,
- wherein the slurry exiting from said passage outlet passes from said passage outlet to the apparatus outlet via another passage wherein the minimum dimension is not only greater than the dimension of the fine particles discharged from the mill but also would pass therethrough 80% of the equilibrium grinding medium content retained in the mill.
A method for classifying particles in a slurry, comprising a substance to be ground, in an attrition mill having one or more inlets, an apparatus outlet (6), a grinding chamber having a grinding stage or stages ("GS"), an axial impeller (10) disposed in the grinding chamber and adapted to cooperate with a slurry of coarse grinding medium to reduce to fine particles the substance to be ground, comprising the steps of:
- admitting the slurry to a passage (19) having a passage inlet (15A) and a passage outlet (32) disposed opposite or radially inwards of the passage inlet (15A),
- rotating the slurry in the passage about the impeller axis, and
- selecting the velocity of rotation of the slurry having regard to the mass of coarse and fine particles in the slurry to separate the coarse particles from the fine particles so that slurry exiting from the passage outlet contains the fine particles and is substantially free of coarse particles,
- wherein the slurry is driven in a rotation by means of a pair of discs spaced apart by a distance less than the spacing between adjacent grinding elements and defining the passage therebetween,
- wherein the impeller includes at least two grinding elements spaced apart by a distance "g" along the axial impeller and the pair of discs is mounted on the rotor and spaced by a distance "c" from an adjacent grinding element, wherein "c" is less than 0.7 times "g".
A method for classifying particles in a slurry, comprising a substance to be ground, in an attrition mill having one or more inlets, an apparatus outlet (6), a grinding chamber having a grinding stage or stages ("GS"), an axial impeller (10) disposed in the grinding chamber and adapted to cooperate with a slurry of coarse grinding medium to reduce to fine particles the substance to be ground, comprising the steps of:
- admitting the slurry to a passage (19) having a passage inlet (15A) and a passage outlet (32) disposed opposite or radially inwards of the passage inlet (15A),
- rotating the slurry in the passage about the impeller axis, and
- selecting the velocity of rotation of the slurry having regard to the mass of coarse and fine particles in the slurry to separate the coarse particles from the fine particles so that slurry exiting from the passage outlet contains the fine particles and is substantially free of coarse particles,
- wherein the slurry is driven in a rotation by means of a pair of discs spaced apart by a distance less than the spacing between adjacent grinding elements and defining the passage therebetween,
- wherein the coarse particles are separated from the fine particles solely by centrifugal force.
An attrition mill comprising:
- a grinding chamber having a grinding stage or stages;
- one or more inlets for admitting into the apparatus a coarse grinding medium, a slurrying liquid, and a substance to be ground;
- an apparatus outlet;
- an axial impeller disposed in the grinding chamber and adapted to cooperate with a slurry of said medium to reduce the particle size of said substance;
- and
- a classifying stage wherein the particles are separated for discharge from the mill from particles to be returned to the grinding stage or stages solely by centrifugal force.
Dependencies are inferred from the claim text.