Method and apparatus for grinding material, and use of the method and apparatus

Abstract

The invention relates to a method and an apparatus for grinding material in a grinding apparatus comprising two counter-rotating rotors, an upper rotor (1) and a lower rotor (2), in which method the material to be comminuted is fed into the apparatus through the center of the upper rotor (1). In the apparatus, the material to be comminuted is crushed by rotating compression rolls (4), which are pressed by means of centrifugal force against the inner surface (3a) of the upper rotor (1).

Description

[0001] METHOD AND APPARATUS FOR GRINDING MATERIAL, AND USE OF THE

[0002] METHOD AND APPARATUS

[0003] The present invention relates to a method defined in the preamble of claim 1 and to an apparatus defined in the preamble of claim 6 for grinding material, as well as to a use of the method and apparatus defined in claim 12.

[0004] The method and grinding apparatus according to the invention, hereinafter also referred to as the solution according to the invention, is primarily intended for the fine grinding of materials originating from industrial side streams, for example lime separated from steel slag, into such a particle size that it is suitable for use in cement production as a cement substitute and additive. Advantageously, the grinding apparatus comprises two counter-rotating rotors; an upper rotor and a lower rotor, and the material to be comminuted can be fed into the apparatus through the center of the upper rotor.

[0005] One solution according to the prior art is the applicant's own international patent publication WO 2019141906 Al, which discloses a grinding apparatus intended, for example, for fine grinding of steel slag from industrial side streams. The apparatus comprises two rotors rotating in opposite directions: an upper rotor and a lower rotor. The material is fed into the apparatus through the center of the upper rotor. The solution according to the present invention differs from the solution disclosed in said publication, among other things, in that the upper rotor is provided with a cylindrical outer shell, against the inner surface of which compression rolls arranged in the lower rotor are pressed by centrifugal force, and in that the material to be comminuted, fed from above, is arranged to be crushed between the inner surface of the outer shell and the compression rolls. All other grinding apparatuses otherwise known for the same purpose are single- or double-rotor devices equipped with crushing elements. With the above-mentioned grinding apparatuses, a sufficient impact, i.e. crushing velocity, is not achieved, nor are they sufficiently suitable for the above- mentioned materials.

[0006] The object of the present invention is to eliminate the above- mentioned drawbacks and to provide a simple and inexpensive method and apparatus for grinding material, for example lime separated from steel slag, to such fineness and quality that it can be used, among other things, as a substitute for cement powder, either partially or entirely replacing cement powder. The method according to the invention is characterized by what is defined in the characterizing part of claim 1. Correspondingly, the apparatus according to the invention is characterized by what is defined in the characterizing part of claim 6. Other embodiments of the invention are characterized by what is defined in the other claims.

[0007] In order to achieve the object of the invention, the method according to the invention for grinding material comprises two counter-rotating rotors, an upper rotor and a lower rotor, wherein the material to be comminuted is fed into the apparatus through the center of the upper rotor. Advantageously, the material to be comminuted is crushed against the inner surface of the upper rotor by means of centrifugal force.

[0008] The apparatus according to the invention for grinding material comprises two counter-rotating rotors, an upper rotor and a lower rotor, and the material to be comminuted is arranged to be fed into the apparatus through the center of the upper rotor. Advantageously, the upper rotor is provided with a cylindrical outer shell, against the inner surface of which compression rolls arranged in the lower rotor are adapted to be pressed by means of centrifugal force.

[0009] One major advantage of the solution according to the invention is that the crushing speed of the grinding apparatus increases compared to prior art solutions. This is particularly evident when grinding relatively soft materials, such as lime separated from steel slag.

[0010] The invention is described below, by way of example, with reference to the accompanying drawings, in which

[0011] Figure 1 shows the grinding apparatus in a longitudinal section,

[0012] Figure 2 shows the grinding apparatus in a cross-section, and

[0013] Figure 3 shows a blade as seen in direction A of Figure 2.

[0014] The method and apparatus according to the invention are intended for the fine grinding of various materials, and are also well suited for the fine grinding of materials originating from industrial side streams, for example lime separated from steel slag, to such a particle size that it is suitable for use, for example, in cement production as a cement substitute and additive.

[0015] The grinding apparatus according to the invention, which may also be referred to as a mill, consists of two counter-rotating rotors, an upper rotor 1 and a lower rotor 2, the latter being entirely inside the upper rotor 1 except for its rotational shaft and comprising one or more compression rolls 4. Advantageously, the number of compression rolls 4 may be, for example, eight. The material to be comminuted is arranged to be fed into the apparatus through the center of the upper rotor 1, through the rotational shaft of the upper rotor 1.

[0016] The upper rotor 1 is provided with a cylindrical outer shell 3 opening downward, against the substantially vertical inner surface 3a of which the compression rolls 4 associated with the lower rotor 2 are pressed by centrifugal force when the apparatus is in operation. In this way, the material to be comminuted, falling from above through the rotational shaft of the upper rotor 1, is crushed and comminuted between the inner surface 3a of the outer shell 3 and the compression rolls 4.

[0017] The compression rolls 4 are hingedly attached to the lower rotor 2 via bar-like fastening elements 5 in such a way that the compression rolls 4 exert a resilient compression force against the inner surface 3a of the outer shell 3 when the apparatus is in operation and at least the lower rotor 2 rotates around its central axis.

[0018] The fastening element 5 may comprise, for example, an upper fastening arm, a first end of which is hingedly attached to an upper fastening flange of the lower rotor 2, and a lower fastening arm, a first end of which is hingedly attached to a lower fastening flange of the lower rotor 2, the opposite ends of the fastening arms being connected to the shaft of the compression roll 4, which is preferably a vertical shaft and serves as the rotational shaft of the compression roll 4. The hinged attachment of the fastening arms here means that the arms can pivot around a hinge shaft 5a located at the attachment point of their first end. The hinge structure may comprise, for example, a bearing or a pin. The first ends of the fastening arms of the fastening elements 5 are positioned in the fastening flanges of the lower rotor 2 in such a way that, when the lower rotor 2 rotates, the centrifugal force pivots the second end of the fastening arms in the rotational direction of the lower rotor 2, whereby the compression rolls 4 are pressed against the inner surface 3a of the upper rotor 1. In this case, the first end of each fastening element 5 is hinged to the lower rotor 2 and the second end is connected to the shaft of the compression roll 4 in such a way that a straight line between the central axis of the compression roll 4 and the hinge shaft 5a of the fastening element 5 passes outside the rotational axis of the lower rotor 2. This is clearly seen in Figure 2, in which, however, only two compression rolls 4 with their fastening elements 5 are shown for clarity. In the solution according to the invention, the combined structure of the fastening element 5 and the compression roll 4 is such that the shortest straight distance from the hinge shaft 5a at the first end of the fastening arm of the fastening element 5, in the direction of the fastening arm, to the contact point between the compression roll 4 and the inner surface 3a of the outer shell 3 is greater than the distance of the corresponding hinge shaft 5a from the inner surface 3a in the radial direction of said inner surface.

[0019] On the upper surface 6 of the lower rotor 2 there are blades 7 which, due to centrifugal force, feed the material to be comminuted onto the inner surface 3a of the outer shell 3 of the upper rotor 1. The blades 7 may be straight plates radial to the lower rotor 2 or structures of another shape and orientation .

[0020] Below the lower rotor 2, there is an electric motor 9 connected via a gearbox 8, the electric motor 9 driving the rotation of the lower rotor 2. The rotational shaft of the lower rotor 2 is mounted in bearings on the frame of the apparatus.

[0021] The upper rotor 1 is mounted on bearings 11 in an outer casing 12 of the apparatus, and the rotational power of the upper rotor 1 is transmitted, for example, via belts 13 to a pulley

[0022] 14 of the upper rotor 1.

[0023] The outer shell 3 of the upper rotor 1 is provided with vanes

[0024] 15 that generate an upward airflow inside the apparatus. Advantageously, the vanes 15 are located between the outer casing 12 of the apparatus and the outer shell 3 of the upper rotor 1. The angle of the vanes 15 is adjustable. There may be two or more vanes 15. In the present example, there are four vanes 15.

[0025] In a cover portion 16 of the outer casing 12 of the apparatus there is a suction opening 17 through which particulate matter present between the outer casing 12 and the upper rotor 1 can be sucked, by means of a cyclone or a corresponding suction device, into an external collection container or for further processing. There may be one or more suction openings 17.

[0026] In the method according to the invention, the material to be comminuted is fed into the apparatus from above through the rotational shaft of the upper rotor 1 and is crushed by means of centrifugal force against the inner surface 3a of the upper rotor 1 of the grinding apparatus.

[0027] Centrifugal force is applied to one or more compression rolls 4 attached to the lower rotor 2 by rotating the lower rotor 2 around its central axis, whereby each compression roll 4 is pressed against the inner surface 3a of the upper rotor 1.

[0028] In order to increase the capacity, the material to be comminuted is thrown against the inner surface 3a of the upper rotor 1 under the effect of centrifugal force during the rotation of the lower rotor 2, guided by the blades 7 on the upper surface of the lower rotor 2.

[0029] In the method according to the invention, an upward airflow is also generated inside the apparatus, between the outer casing 12 and the upper rotor 1, by means of the vanes 15 rotating with the upper rotor 1 when the apparatus is in operation .

[0030] The particulate matter present between the outer casing 12 and the upper rotor 1 of the apparatus is drawn through the suction opening 17 in the cover portion 16 into an external collection container or for further processing.

[0031] The method and apparatus according to the invention can be used for one or more of the following: grinding of materials originating from industrial side streams; fine grinding of lime separated from steel slag to such a particle size that it is suitable for use in cement production as a cement substitute and additive; grinding of various soft materials.

[0032] It is obvious to a person skilled in the art that the invention is not limited to the example described above, but may vary within the scope of the claims presented below. Thus, the grinding apparatus is suitable not only for crushing steel slag but also for crushing other slags, such as fly ash or bottom ash, as well as for crushing and comminuting material from mining side streams. The separation of metals from the crushed mass is carried out by methods known per se. For example, iron particles can be separated with a magnetic separator, and other non-magnetic metals can be separated by known chemical methods. It is also obvious to a person skilled in the art that there may be two or even more compression rolls arranged on top of each other, resulting in an increased compression surface area and a corresponding increase in the efficiency of the appa- ratus .

Claims

CLAIMS1. A method for grinding material in a grinding apparatus comprising two counter-rotating rotors, an upper rotor (1) and a lower rotor (2) , wherein the material to be comminuted is fed into the apparatus through the center of the upper rotor (1) , characterized in that the material to be comminuted is crushed by means of centrifugal force against the inner surface (3a) of the upper rotor (1) .

2. The method according to claim 1, characterized in that by rotating the lower rotor (2) around its central axis, centrifugal force is applied to one or more compression rolls (4) attached to the lower rotor (2) , whereby each compression roll (4) is pressed against the inner surface (3a) of the upper rotor ( 1 ) .

3. The method according to claim 1 or 2, characterized in that, during the rotation of the lower rotor (2) , the material to be comminuted is thrown by centrifugal force against the inner surface (3a) of the upper rotor (1) , guided by blades (7) on the upper surface of the lower rotor (2) .

4. The method according to claim 1, 2 or 3, characterized in that, when the apparatus is in operation, an upward airflow is generated inside the apparatus, between an outer casing (12) and the upper rotor (1) , by vanes (15) rotating with the upper rotor (1) .

5. The method according to any one of the preceding claims, characterized in that particulate matter present between the outer casing (12) and the upper rotor (1) is drawn through a suction opening (17) in a cover portion (16) into an external collection container or for further processing.

6. An apparatus for grinding material, the apparatus comprising two counter-rotating rotors, an upper rotor (1) and a lower rotor (2) , into which apparatus a material to be comminuted is arranged to be fed through the center of the upper rotor (1) , characterized in that the upper rotor (1) is provided with a cylindrical outer shell (3) , against the inner surface (3a) of which compression rolls (4) in the lower rotor (2) are adapted to be pressed by means of centrifugal force.

7. The apparatus according to claim 6, characterized in that the compression rolls (4) are hingedly attached to the lower rotor (2) via bar-like fastening elements (5) in such a way that the compression rolls (4) exert a resilient compression force against the inner surface (3a) of the outer shell (3) .

8. The apparatus according to claim 6 or 7, characterized in that a first end of each fastening element (5) is pivotally attached to the lower rotor (2) and a second end is connected to the shaft of the compression roll (4) such that a straight line between the central axis of the compression roll (4) and a hinge shaft (5a) of the fastening element (5) passes outside the rotational axis of the lower rotor (2) .

9. The apparatus according to claim 6, 7 or 8, characterized in that on an upper surface (6) of the lower rotor (2) there are blades (7) which, due to centrifugal force, feed the material, by centrifugal force, onto the inner surface (3a) of the outer shell (3) of the upper rotor (1) .

10. The apparatus according to any one of claims 6 to 9, characterized in that the outer shell (3) of the upper rotor (1) is provided with vanes (15) having an adjustable angular position, the vanes (15) being arranged to generate an upward airflow inside the apparatus.

11. The apparatus according to any one of claims 6 to 10, characterized in that a suction opening (17) is provided in a cover portion (16) of an outer casing (12) of the apparatus, through which particulate matter present between the outer casing (12) and the upper rotor (1) can be drawn, by means of a cyclone or a corresponding suction device, into an external collection container or for further processing.

12. Use of the method according to claim 1 and the apparatus according to claim 6 for one or more of the following: grinding of materials originating from mining and industrial side streams; fine grinding of lime separated from steel slag to such a particle size that it is suitable for use in cement production as a cement substitute and additive; grinding of various soft materials.

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