WO2021089912A1

WO2021089912A1 - Mill

Info

Publication number: WO2021089912A1
Application number: PCT/FI2020/050708
Authority: WO
Inventors: Pertti Hänninen
Original assignee: Moviator Oy
Priority date: 2019-11-04
Filing date: 2020-10-28
Publication date: 2021-05-14
Also published as: EP4054766A4; EP4054766A1

Abstract

This invention relates to a mill for crushing steel slag or bottom ash to separate metals and slag, which mill comprises a casing (1), a cover plate (2), a bottom plate (3) and a crushing mechanism (4) inside the casing (1) by means of which crushing mechanism (4) the steel slag and/or the bottom ash are crushed. The crushing mechanism (4) comprises an inner rotor (5) and an outer rotor (6), and the material to be crushed is arranged to be fed to the center area of the inner rotor (5), from where it is ejected by centrifugal force to the outer rotor (6) and further outwards through the outlets (7). The mill comprises a lower rotor (8) below the inner rotor (5) and outer rotor (6), which lower rotor (8) is arranged to receive its rotational motion from its own power source.

Description

MILL

The present invention relates to a mill as defined in the preamble of claim 1, which mill is intended for crushing steel slag or bottom ash so that metals and slag materials can be separated.

Most of the mills of the prior art, which are intended for crushing steel slag or bot tom ash, are single rotor mills or they comprise other kinds of crushing mecha nisms. The problem with the mills of that kind is that the required impact velocity for crushing of sufficient quality is not achieved. Thus, the mills of that kind are not adequately suited for the materials mentioned above.

The simple and inventive solution presented in the international patent publication No. W02019/141906 A1 is intended to eliminate this problem. The mill according to the WO publication comprises a crushing element with two rotors, an inner ro tor and an outer rotor that are rotating opposite to each other. In that way the im pact velocity can be doubled.

The mills of the prior art are mainly also so-called dry mills. One significant prob- lem then is that when they are in operation, they emit a huge amount of fine dust which is often also toxic.

Finnish patent No. FI128329B presents one way to solve the problem of the mills of the prior art. Experiments and the use of the mill described in the patent have shown that the quality of the crushed material is exactly what is desired.

The object of the present invention is to eliminate the drawbacks of the prior art in general described above and to further develop the mill described in the Finnish patent. One object of the invention is also to improve the effectiveness of the mill so that the outcome of the crushed material is easily adjustable by the speeds and rotation directions of the rotors of the mill. The mill according to the invention is characterized by what is presented in the characterization part of claim 1. Other embodiments of the invention are characterized by what is presented in the other claims.

In order to achieve the objectives of the present invention, the present invention provides a mill for crushing steel slag or bottom ash to separate metals and slag. The mill comprises a casing, a cover plate, a bottom plate and a crushing mech anism inside the casing by means of which crushing mechanism the steel slag and/or the bottom ash are crushed. The crushing mechanism comprises an inner rotor and an outer rotor, and the material to be crushed is arranged to be fed to the center area of the inner rotor, from where it is ejected by centrifugal force to the outer rotor and further outwards through the outlets. Preferably, the mill com prises a lower rotor below the inner rotor and outer rotor, which lower rotor is ar ranged to receive its rotational motion from its own power source.

The solution according to the invention has the advantage that thanks to the third rotor under the two other rotors the outcome of the crushed material is easily ad justable by the speeds and rotation directions of the rotors of the mill. Another advantage is the air gap between the driving shaft of the outer rotor and the feed er hopper, which air gap makes it possible to feed among other things pressur ized air or compressed air to the crushing mechanism. Along with the pressurized air also water and/or various chemicals may be fed to the crushing mechanism so that, for instance the water disintegrates into small droplets among the pressur ized air. This prevents poisonous particles from exiting the mill with dust particles. Also, various chemicals that may be fed separately or together with the air and/or water may be made to react positively with small poisonous particles of the crushed materials and thus to prevent detrimental emissions effectively on their own behalf. Yet one advantage is that air/water mixture improves the distribution of the material to be crushed and also cools the material at the same time.

In the following, the invention will be described in detail by the aid of examples by referring to the attached simplified and diagrammatic drawings, wherein Fig. 1 presents in a cross-sectioned side view a mill according to the inven tion,

Fig. 2 presents in a cross-sectioned side view a crushing mechanism of the mill according to the invention, and

Fig. 3 presents in a top view a mill according to the invention cross- sectioned along the section line A-A in figure 1.

The mill according to the invention is intended for crushing steel slag so that met- als and slag materials can be separated. The mill comprises a casing 1 , a cover plate 2 and a bottom plate 3. Inside the casing 1 the mill comprises a crushing mechanism 4 by the help of which the steel slag can be crushed. The mill also comprises a feeder hopper 7 through which the material to be crushed is fed into the casing 1 of the mill, and further the mill comprises a power arrangement to power the mill, and also a control system to control and adjust the operations of the mill.

The crushing mechanism 4 comprises two co-axial contra-rotating rotors; an inner rotor 5 and an outer rotor 6 which are rotating opposite each other. The rotors 5 and 6 overlap each other vertically so that the inner rotor 5 is substantially below and totally or partially inside the outer rotor 6. The inner rotor 5 comprises a sub stantially circular bottom plate 5e and a group of radial rotor vanes 5a fastened onto the bottom plate 5e. Preferably, the rotor vanes 5a of the inner rotor 5 ex tend upwards from the bottom plate 5e inside the inner circle of the crushing blades 6a of the outer rotor 6.

The outer rotor 6 is the uppermost rotor and comprises a substantially circular cover plate 6e and a group of crushing blades 6a in its outer circumference. The crushing blades 6a of the outer rotor 6 extend downwards outside the outer circle of the vanes 5a of the inner rotor 5 so that advantageously the lower ends of the crushing blades 6a of the outer rotor 6 are near the upper surface of the bottom plate 5e of the inner rotor 5 or below it.

In addition to the two rotors 5 and 6 the crushing mechanism 4 according to the invention also comprises a third rotor or a lower rotor 8 in the casing 1 below the rotors 5 and 6. The lower rotor 8 comprises a bottom plate 8e and a group of crushing blades 8a in its outer circumference. Preferably, the crushing blades 8a of the lower rotor 8 extend upwards outside the outer circle of the inner rotor 5. In order to improve the capacity of the mill and reduce blocks the bottom plate 8e of the lower rotor 8 comprises openings 9 which may preferably be between the crushing blades 8a that are in the outer circumference of the lower rotor 8. The openings 9 may, for instance, be semicircular in shape and extend from the outer circumference of the bottom plate 8e towards the center of the bottom plate 8e, or the openings may also be circular or of any shape in the area of the bottom plate 8e of the lower rotor 8.

In figures 1 and 2 the mill and its components are cross-sectioned in a side view so that for the sake of clarity all the components are not cross-sectioned, and all the components are not wholly shown. For instance, only the closest vanes 5a and crushing blades 6a, 8a to the cross-section plane are shown in the figures.

All the three rotors 5, 6, 8 are co-axial and have their own driving shafts 5b, 6b and 8b and power sources, such as electric motors. The driving shaft 6b of the outer rotor 6 is a hollow shaft and is advantageously bearing-mounted on the cover plate 2 of the casing 1. The power and rotational motion for the driving shaft 6b of the outer rotor 6 is preferably transmitted from its own power source through a transmission belt 6c and driving shaft pulley 6d that is fastened onto the driving shaft 6b.

Correspondingly, the driving shaft 8b of the lower rotor 8 is also a hollow shaft and is advantageously bearing-mounted on the bottom plate 3 of the casing 1. The power and rotational motion for the driving shaft 8b of the lower rotor 8 is preferably transmitted from its own power source through a transmission belt 8c and driving shaft pulley 8d that is fastened onto the driving shaft 8b.

The driving shaft 5b of the inner rotor 5 is preferably bearing-mounted inside the hollow driving shaft 8b of the lower rotor 8. The power and rotational motion for the driving shaft 5b of the inner rotor 5 is preferably transmitted from its own power source through a transmission belt 5c and driving shaft pulley 5d that is fastened onto the driving shaft 5b.

The control system of the mill comprises adjustment means by the help of which the speed and/or direction of rotation of each rotor 5, 6, and 8 may be adjusted. Preferably, rotational speeds and directions of rotation of the rotors 5, 6 and 8 can be adjusted independently of each other. The control system and adjustment means may be in common to all the power sources of the rotors 5, 6 and 8, or each power source may have its own control system and adjustment means.

The feeder hopper 7 comprises a funnel-shaped upper part 7a and a tubular low er part 7b that is inserted into the hollow driving shaft 6b of the outer rotor 6 and preferably extends down into the center area of the inner rotor 5. The material 12 to be crushed is arranged to be fed through the feeder hopper 7 into the center area of the inner rotor 5, from which it is ejected by the centrifugal force onto the crushing blades 6a of the outer rotor 6, and further down to the lower rotor 8. Af ter the lower rotor 8 the crushed material falls out from the casing 1 through the outlet openings 10 which are below the lower rotor 8 in the bottom plate 3 of the casing 1.

Below the feeder hopper 7 the mill comprises a cone 11 tapering upwards from the bottom plate 5e in the center of the inner rotor 5. The cone 11 is arranged to guide the steel slag or bottom ash onto the vanes 5a of the inner rotor 5. The mill according to the invention also comprises a feed channel 13 to feed pressurized air, water or chemicals or their mixtures into the material inside the casing 1 , for instance in the direction of arrow 14. The feed channel 13 may be a circular gap between the driving shaft 6b of the outer rotor 6 and the feeder hop- per 7, and it may extend downwards into the center area of the space between the inner rotor 5 and the outer rotor 6. The feed channel 13 makes it possible to feed among other things pressurized air to the crushing mechanism 4. Along with the pressurized air also water and/or various chemicals may be fed to the crush ing mechanism 4 so that, for instance, the water disintegrates into small droplets among the pressurized air. This prevents poisonous particles from exiting the mill with dust particles. Also, various chemicals that may be fed separately or together with the air and/or water may be made to react positively with the small poison ous particles of the crushed materials and thus to prevent detrimental emissions effectively.

Preferably, the components of the mill have been manufactured of a suitable steel material with both durability and toughness.

It is obvious to the person skilled in the art that the invention is not restricted to the example described above but that it may be varied within the scope of the claims presented below. Thus, for example, the mill is also suitable not only for crushing steel slag and bottom ash but also for crushing other slag materials. The separation of the metals from the crushed material is carried out by methods known per se. Iron particles can be separated, for example, by a magnetic sepa- rator and other non-magnetic metals, for example, by known chemical methods. There may be more than just two vanes and crushing blades in the perimeter of the rotors, for example four, six, eight or even more.

Claims

1. A mill for crushing steel slag or bottom ash to separate metals and slag, which mill comprises a casing (1), a cover plate (2), a bottom plate (3) and a crushing mechanism (4) inside the casing (1) by means of which crushing mechanism (4) the steel slag and/or the bottom ash are crushed, and which crushing mechanism (4) comprises an inner rotor (5) and an outer rotor (6), and that the material to be crushed is arranged to be fed to the center area of the inner rotor (5), from where it is ejected by a centrifugal force to the outer rotor (6) and further outwards through outlets (7), characterized in that the mill comprises a lower rotor (8) be low the inner rotor (5) and outer rotor (6), which lower rotor (8) is arranged to re ceive its rotational motion from its own power source.

2. A mill according to claim 1 , characterized in that each of the three rotors (5, 6, 8) has its own power source, such as an electric motor, by means of which the rotational speeds and directions of the rotors (5, 6 ,8) are arranged independently of each other.

3. A mill according to claim 1 or 2, characterized in that the mill comprises a con- trol system and adjustment means to independently control and adjust the speed of rotation of each rotor (4, 5, 8).

4. A mill according to claim 1 , 2 or 3, characterized in that the mill comprises a control system and adjustment means to independently control and adjust the direction of rotation of each rotor (4, 5, 8).

5. A mill according to any of the preceding claim above, characterized in that the outer rotor (6) comprises a tubular driving shaft (6b) and the lower rotor (8) com prises a tubular driving shaft (8b), and inner rotor (5) comprises a driving shaft (5b) that is placed inside the tubular driving shaft (8b) of the lower rotor (8).

6. A mill according to any of the preceding claim above, characterized in that the mill comprises a feeder hopper (7) having a tubular lower part (7b) that is inserted into the hollow driving shaft (6b) of the outer rotor (6) and preferably extends down into the center area of the inner rotor (5).

7. A mill according to any of the preceding claim above, characterized in that the mill comprises a feed channel (13) to feed pressurized air, water or chemicals or their mixtures into the material inside the casing (1).

8. A mill according to claim 7, characterized in that each of the feed channel (13) is a circular gap between the tubular driving shaft (6b) of the outer rotor (6) and the lower part (7b) of the feeder hopper (7).

9. A mill according to any of the preceding claim above, characterized in that the below the tubular lower par (7b) of the feeder hopper (7) the mill comprises a cone (11) tapering upwards from the bottom plate (5e) in the center area of the inner rotor (5).

10. A mill according to any of the preceding claim above, characterized in that the crushing members of the lower rotor (8) are upwardly extending crushing blades (8a).

11. A mill according to any of the preceding claim above, characterized in that the lower rotor (8) comprises a bottom plate (8e) which comprises openings (9) for the crushed material to fall through the openings (9).

12. A mill according to claim 11 , characterized in that are the openings (9) are one or more of the following: between them semicircular in shape and extend from the outer circumference of the bottom plate (8e) between the crushing blades (8a) towards the center of the bottom plate (8e); circular in shape in the free area of the bottom plate (8e); of any shape in the free area of the bottom plate (8e).