CA3057258C

CA3057258C - Grinding mill, pulp lifter and outer pulp lifter element

Info

Publication number: CA3057258C
Application number: CA3057258A
Authority: CA
Inventors: Alex Heath; Andres PAZ; Adam DEL BIANCO; Tamer EID
Original assignee: Metso Outotec Finland Oy
Current assignee: Metso Finland Oy
Priority date: 2017-03-20
Filing date: 2017-03-20
Publication date: 2024-01-02
Anticipated expiration: 2037-03-20
Also published as: CN211359046U; ZA201906556B; MX2019011115A; BR112019019641A2; AU2017405653A1; WO2018172594A1; EA201992047A1; AU2017405653B2; EA038752B1; CA3057258A1; PE20191522A1

Abstract

An outer pulp lifter element (1) for a pulp lifter (2) for a rotating drum grinding mill (3) comprises a first wall (4) directed towards the discharge end of the grinding mill, and at least one vane (6) protruding from the inner surface (12) of the first wall (4) towards the inside of the drum grinding mill (3) and comprising a guiding surface (10) on the front side of the vane (6). The outer edge (11) of the guiding surface (10) is angled in relation to the inner surface (12) of the first wall (4) in such a manner, that the angle (T) between the inner surface (12) of the first wall (4) and the outer edge (11) of the guiding surface (10) is smaller than 90 degrees.

Description

GRINDING MILL, PULP LIFTER AND OUTER PULP LIFTER ELEMENT
BACKGROUND
The invention relates to grinding mills, and more particularly to pulp lifters and outer pulp lifter elements.
One of the problems associated with the pulp lifters is that the ground material already lifted to the pulp lifter tends to fall back to the grind-ing mill drum. This is inefficient for both the flow rate and power consump-tion.
CN204866029 discloses a discharge end lining plate for a large-scale mining semi-autogenous grinding machine, which is composed of a pulp lifter and a grid plate, wherein a pulp lifter lifting strip is arranged on the pulp lifter, and a grid plate lifting strip is arranged on the grid plate. A
plurali-ty of discharge end linings are circumferentially adjacent to each other, and each of the pulp lifter lifting strips or the lattice lifting strips is composed of an arc-shaped lifting strip 5 and an arc-shaped lifting strip 6, and each adja-cent two pulp lifting implements or a grid plate, wherein a curved lifter 5 of the slurry lifter or the grid plate is connected to the head of the curved lift strip 6 of the other block, and constitutes a combined arc-shaped lifting strip extending to the outer edge of the discharge end liner, adjacent a discharge channel is formed between the two combined arc-shaped lifting strips.
BRIEF DESCRIPTION
It is thus an object of the present invention to provide a new grinding mill, a new pulp lifter and a new outer pulp lifter element. The ob-ject of the invention is achieved by a grinding mill, a pulp lifter and an outer .. pulp lifter element, which are characterized by what is stated in the inde-pendent claims. Some preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on the idea of forming a pocket in the pulp lifter by providing a vane of the pulp lifter element at an angle in relation to the wall of the pulp lifter element.
An advantage of the arrangement of the invention is that a more efficient flow of material and lower power consumption per a unit of ground material produced can be achieved with a simple structure. Some further ad-vantages are disclosed in the detailed description in connection with embod-

2 iments.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which Figure 1 illustrates a grinding mill;
Figure 2 illustrates an embodiment of an outer pulp lifter element for a pulp lifter in connection with a detail of a pulp lifter assembly;
Figure 3 illustrates an embodiment of an outer pulp lifter element for a pulp lifter in connection with a detail of a pulp lifter assembly;
Figure 4 illustrates an embodiment of an outer pulp lifter element in connection with a detail of a pulp lifter assembly;
Figure 5 illustrates an embodiment of an outer pulp lifter in con-nection with a detail of a pulp lifter assembly; and Figure 6 illustrates an angle 0 in an outer pulp lifter element.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 illustrates a grinding mill 3, more specifically a rotating drum grinding mill. Grinding mills are used for processing hard solid material such that large solid material is ground into smaller pieces.
A grinding mill 3 may comprise a cylindrical shell 20 arranged ro-tatably around its longitudinal axis D extending in a horizontal direction.
The material to be ground may be received into the cylindrical shell 20, for in-stance through a feed chute (not numbered). The grinding takes place within the cylindrical shell 20 by lifting and dropping the material to be ground in-side the cylindrical shell 20. Lifter bars or lifter plates (not shown, but their places inside the cylindrical shell are indicated by dotted lines in the Figure 1) may be used for lifting the material inside the cylindrical shell.
According to an embodiment, loose grinding elements, such as balls comprising for in-stance stone or metal material, may be provided inside the cylindrical shell to aid in grinding.
The grinding mill 3 may comprise at least one inlet 21 for receiv-ing a continuous feed of material to be ground. The material to be ground may comprise for instance mineral ore. The grinding mill 3 may also com-prise at least one outlet 22 for continuous discharge of the ground material.

3 The ground material may comprise for instance ore slurry. The inlet(s) 21 and the outlet(s) 22 may be provided at the opposite ends of the cylindrical shell in the direction of the longitudinal axis D of the cylindrical shell.
Thus, a continuous grinding process may be provided by feeding material to be ground into the cylindrical shell 20 through the inlet(s) 21, grinding the ma-terial to be ground while it is moved through the cylindrical shell 20 and moved within the cylindrical shell by lifting and dropping the material to be ground on its way through the cylindrical shell 20, and discharging the ground material through the outlet(s) 22 at the opposite end of the cylindri-cal shell.
The grinding mill 3 may further comprise a grate 23 provided be-tween the interior of the cylindrical shell 20 and the outlet 22. The grate 23 may comprise openings 31 for passing through ground material particles of a predetermined size or smaller. In other words, the openings 31 may be di-mensioned in such a manner that particles of a predetermined size or smaller fit through the openings 31 and may thus be moved towards the outlet 22, and particles that are larger than the predetermined size do not fit through the openings but are dropped back to the interior of the cylindrical shell for further grinding. Thereby the grate prevents particles larger than the prede-termined size passing through the grate. The grinding mill 3 may also com-prise a discharger 24 provided at the outlet 22 end of the grinding mill for discharging the ground material through the outlet 22.
The grinding mill 3 may further comprise a pulp lifter 2. The pulp lifter 2 may comprise at least one outer pulp lifter element 1 and/or a pulp lifter 2 provided between the grate and the discharger for guiding the ground material from the cylindrical shell to the discharger 24. More particularly, the pulp lifter 2 may be arranged to lift the ground material passed through the grate 23 to the outlet 22 for discharging the ground material through the dis-charger 24, when the pulp lifter 2 is arranged to rotate together with the cy-lindrical shell about the longitudinal axis D of the cylindrical shell.
Depending on the embodiment, the pulp lifter 2 may be arranged to rotate, together with the cylindrical shell, in a clockwise or in a counterclockwise direction.
Differ-ent embodiments of such an outer pulp lifter element 1 and/or a pulp lifter 2 are described in the description.
The pulp lifter 2 may comprise at least one outer pulp lifter ele-

4 ment 1. Typically, a pulp lifter 2 comprises multiple outer pulp lifter elements 1. According to an embodiment, an outer pulp lifter element 1 comprises a form of a sector or a truncated sector and a number of such outer pulp lifter elements 1 may be arranged circumferentially side by side, whereby the out-er pulp lifter elements 1 may form a disc-shaped or an annulus-shaped pulp lifter 2. According to an embodiment, a pulp lifter 2 may comprise 15 to 35 outer pulp lifter elements 1. According to another embodiment, a pulp lifter 2 may comprise 18 to 32 outer pulp lifter elements 1.
The disc-shaped or annulus-shaped pulp lifter 2 may comprise a conical shape as can be seen in Figure 1, for example. The pulp lifter 2 may be arranged at the end of the cylindrical shell and to conform to the end of the cylindrical shell in such a manner, that the middle point F of the pulp lifter may be arranged on the longitudinal axis of the cylindrical shell. The pulp lifter 2 may be arranged rotatably in the grinding mill 3, such that the pulp lifter 2 is rotatable together as one entity with the cylindrical shell 20 about the longitudinal axis D of the cylindrical shell. Depending on the embodiment, all the outer pulp lifter elements 1 in a pulp lifter 2 may be similar to one an-other or a pulp lifter 2 may comprise different types of outer pulp lifter ele-ments 1.
Figures 2, 3, 4 and 5 illustrate embodiments of an outer pulp lifter element 1 for a pulp lifter 2, such as a pulp lifter 2 for a rotating drum grind-ing mill 3. More particularly, Figure 2 illustrates a part of such a pulp lifter 2 for a rotating drum grinding mill 3. The outer pulp lifter element 1 may form a sector or a truncated sector of an outer pulp lifter. In other words, the outer pulp lifter element 1 may comprise a sector-like shape or a shape of a trun-cated sector and a plurality of such outer pulp lifter elements 1 may be pro-vided circumferentially, side-by-side to form an outer pulp lifter of a pulp lifter 2.
The outer pulp lifter element 1 may comprise a first wall 4 di-rected towards the discharge end of the grinding mill 3. In other words, the first wall 4 may be arranged on the side of the outer pulp lifter element 1 that is opposite to the side where the grate 23 is provided.
The outer pulp lifter element 1 may also comprise at least one vane 6 protruding from the inner surface 12 of the first wall 4 towards the inside of the drum grinding mill 3. The vanes 6 may be arranged to do the lifting of the material passed through the grate 23 towards the middle of the pulp lifter 2 and, thus, the outlet 22. According to an embodiment, the outer pulp lifter element 1 may comprise exactly one vane 6. According to another embodiment, the outer pulp lifter element 1 may comprise two vanes 6 or a

5 plurality of vanes 6. According to a yet another embodiment, a vane 6 may extend to two or more outer pulp lifter elements 1. In other words, a vane 6 may comprise vane portions that may be provided in different outer pulp lifter elements 1, such that the vane 6 is formed when the outer pulp lifter elements 1 are mounted together.
Each vane 6 may extend from an outer part of the outer pulp lifter element 1 towards the inner end 9 of the outer pulp lifter element 1. In other words, the vane may extend from an area at the perimeter or an area close to the perimeter towards the middle point F of the pulp lifter 2. Thus, the inner end 9 of the outer pulp lifter element 1 refers to the end of the outer pulp lifter element 1 directed towards the middle point F of the pulp lifter 2.
The vane 6 may comprise a guiding surface 10 on the front side of the vane 6. The front side of the vane 6 refers to the side of the vane 6 first in the direction of rotation. In other words, the front side of the vane is the side first receiving the ground material, such as the slurry, for instance ore slurry, when the pulp lifter element 1, and more particularly the vane 6, is in the lift-ing phase of the cycle. The front side of the vane thus depends on the direc-tion of rotation of the pulp lifter 2. In a pulp lifter 2 rotated in first direction, the front side of the vane, thus, is on a first side of the vane 6, whereas the front side of the vane is the opposite side of the vane compared to the first side when the pulp lifter 2 is rotated in the opposite direction.
According to an embodiment, the vane 6 may extend radially from the outer part of the outer pulp lifter element towards the inner end of the outer pulp lifter element, such as in the embodiments of Figures 4 and 5.
According to another embodiment, the vane 6 may extend from the outer part of the outer pulp lifter element towards the inner end of the outer pulp lifter element in a curved manner, such as in the embodiments of Figures 2 and 3. In other words, the vane 6 may comprise a concave guiding surface 10 forming a spiralling formation together with an inner part of the pulp lifter 2. In an embodiment with an opposite direction of rotation corn-pared to that of Figures 2 and 3, an opposite direction of spiralling would

6 provide a similar effect of optimally guiding the ground material towards the middle of the pulp lifter.
At least a part of an outer edge 11 of the guiding surface 10 may be angled in relation to the inner surface 12 of the first wall 4. Throughout the description this feature is referred to the outer edge 11 of the guiding surface 10 being angled in relation to the inner surface 12 of the first wall 4, for the sake of clarity, although the purpose for the angled relation is to form a pocket-like shape preventing the ground material from dropping from the guiding surface and the effect can be achieved even only a part of the outer edge 11 was angled in relation to the inner surface 12 of the first wall 4.
The outer edge 11 of the guiding surface 10 comprises the edge of the guiding surface closest to the outer perimeter of the pulp lifter 2.
Accord-ing to an embodiment, the outer edge 11 of the guiding surface 10 may have a profile or shape of a straight line and this line may be angled in relation to the inner surface 12 of the first wall 4. According to another embodiment, the outer edge 11 of the guiding surface 10 may comprise a concave profile or shape, wherein at least a part of the outer edge 11 is angled in relation to the inner surface 12 of the first wall 4. The angled part of the outer edge may, in such an embodiment, also refer to direction of a tangent along the concave outer edge 11. Similarly, the outer edge of the guiding surface may comprise a convex profile or shape, and the angled part of the outer edge may, thus, also comprise a tangent along the convex outer edge 11. Naturally, the outer edge 11 may comprise a profile or a shape that is a combination of curved and straight portions, whereby at least a part of the outer edge 11 is angled in relation to the inner surface 12 of the first wall 4.
The angle 0 between the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding surface 10 may be smaller than 90 degrees.
The inner surface 12 of the first wall 4 may be parallel to the head of the mill.
In other words, the inner surface 12 of the first wall 4 may be parallel to the discharge end of the mill. The effect of the angle 0 between the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding surface 10 being smaller than 90 degrees is that it directs the ground material flow, such as slurry flow, towards the back of the pulp lifter in a more efficient manner.
An angle 0 in an outer pulp lifter element 1 and a direction of rotation C is shown in detail in Figure 6 for clarification. In a pulp lifter 2 with an opposite direc-

7 tion of rotation, a similar angle 0 but at the opposite side of the outer pulp lifter element would have the same effect.
Some advantages of this kind of an outer pulp lifter element 1 comprise preventing ground material, such as slurry, from being dropped back to the inside of the drum, that is to the interior of cylindrical shell, but without a need for added complexity of the pulp lifter structure for keeping the ground material in the pulp lifter; keeping the ground material flow away from the back face of the grate that typically has a rough texture and tends to slow down the material flow thus decreasing the efficiency of the grinding mill; and reducing wear on the back side of the grate since the ground mate-rial, such as slurry, does race along the back of the grate.
According to an embodiment, the angle 0 between the inner sur-face 12 of the first wall 4 and the outer edge 11 of the guiding surface 10 may be smaller than 88 degrees. According to another embodiment, the angle 0 between the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding surface 10 may be in the range of 20 to 70 degrees. This is particular-ly beneficial, as angles 0 of less than 20 degrees between the inner surface of the first wall 4 and the outer edge 11 of the guiding surface 10 are more difficult and expensive to build, whereas angles of 70 degrees or less can pro-vide good guiding properties for the outer pulp lifter element 1 and its guid-ing surface 10. According to a further embodiment, the angle 0 between the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding sur-face 10 may be in the range of 30 to 60 degrees. According to yet another embodiment, the angle 0 between the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding surface 10 may be about 45 degrees.
According to an embodiment, for instance an embodiment of the Figure 3, an outer pulp lifter element 1 may comprise a second surface 7 ex-tending in a radial direction B of the pulp lifter 2 and forming a front surface of the pulp lifter element 1 in the direction of rotation C of the pulp lifter 2.
The front surface of the pulp lifter element refers to the surface first in the direction of rotation C, which is the surface through which the ground mate-rial, such as slurry, from an adjacent, more particularly preceding, outer pulp lifter element first enters the outer pulp lifter element in question. The sec-ond surface 7 may comprise an opening 8 for receiving ground material from an adjacent outer pulp lifter element. According to an embodiment, the sec-

8 ond surface 7 may be substantially perpendicular to the first wall 4.
In such an embodiment, the direction of the inner surface 12 of the first wall 4 may be defined by the first wall 4 side edge of the opening 8 extending in the direction A-A' in Figure 6 parallel to the head of the mill and the radial direction B of the pulp lifter 2. The outer edge 11 of the guiding surface 10 may comprise the outer edge of the opening 8. The angle 0 be-tween the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding surface 10 may then comprise the angle between the first wall 4 side edge of the opening 8 and the outer edge of the opening 8, such as can be seen in Figure 6, for example.
According to an embodiment, the vane 6 may have an equal angle between the inner surface 12 of the first wall 4 and the guiding surface 10 along the whole length of the guiding surface 10. In other words the vane 6 may be sloped to a similar amount along the whole length of the guiding sur-face 10, that is it may have the same angle compared to direction A-A' in Fig-ure 6, for example, along the vane from the outer end of the vane, that is the end closest to the outer end of the pulp lifter, to the inner end of the vane, that is, the end closest to the outlet and discharger of the grinding mill.
According to an embodiment, the angle between the inner surface 12 of the first wall 4 and the guiding surface 10 of the vane 6 may vary along the length of the guiding surface 10. According to an embodiment, the angle between the inner surface 12 of the first wall 4 and the guiding surface 10 of the vane 6 may be reversed at a point of the guiding surface 10. In such em-bodiments, thus, the angle between the inner surface 12 of the first wall 4 and the guiding surface 10 of the vane 6 at the inner end of the vane and/or at a point along the guiding surface of the vane may be different from the an-gle 0 between the inner surface 12 of the first wall 4 and the outer edge 11 of the guiding surface 10. With such embodiments, an improved movement of the ground material along the guiding surface 10 may be achieved. An em-bodiment, where the angle is reversed at a point of the guiding surface, may be particularly beneficial for guiding the ground material to the discharger and the outlet.
According to an embodiment, the outer pulp lifter element may comprise solid cast steel material. According to another embodiment, the outer pulp lifter element may comprise rubber material finish with a steel

9 frame provided inside. According to a further embodiment, the outer pulp lifter element may comprise an elastomer material, such as urethane.
According to an embodiment, a pulp lifter 2 for a rotating drum grinding mill 3 may comprise at least one outer pulp lifter element 1 as de-scribed in this description.
According to an embodiment, the pulp lifter 2 may further com-prise an inner pulp lifter 16. The vane 6 may then extend to the inner pulp lifter 16.
According to an embodiment, at least a part of the guiding surface 17 of the inner pulp lifter part of the vane 6 may also be angled in relation to the inner surface of the back wall 18 of the inner pulp lifter. According to a further embodiment, the guiding surface 17 of the inner pulp lifter part of the vane 6 may be arranged on an opposite side of the vane 6 on the area of the inner pulp lifter when compared to the area of the outer pulp lifter. The op-posite side of the vane 6 refers to the backside of the vane in the rotation di-rection of the pulp lifter. This is beneficial as the ground material falls to op-posite side due to gravity if the material overtops, that is if it does not exit the pulp lifter through the outlet at the highest point of the rotating cycle of the pulp lifter. According to a further embodiment, the vane 6 may extend to the discharger 24 as well.
According to an embodiment, at least a part of the guiding surface of the discharger part of the vane 6 may also be angled in relation to the inner surface of the discharger wall 26. This inner surface of the discharger wall 26 may form a substantially continuous surface with the inner surface of 25 the back wall 18 of an inner pulp lifter element 16 and the inner surface 12 of the first wall 4 of an outer pulp lifter element 1, when the outer pulp lifter element 1, the inner pulp lifter element 16 and the discharger 24 are assem-bled together, for instance in a grinding mill 3.
According to an embodiment, the grate 23 may comprise at least one grate lifter 27 arranged on the cylindrical shell interior side of the grate 23 for guiding particles of the ground material into the pulp lifter 2 through the openings in the grate 23. This may take place in a manner similar to that of the vanes in the pulp lifter; that is the grate lifters may lift the ground ma-terial as the grate rotates. The outer edge 28 of the grate lifter guiding surface 30 may then be angled in relation to a grate wall 29 facing towards the inte-nor of the cylindrical shell 20 in such a manner, that an angle a between the grate wall 29 and the grate lifter guiding surface 30 is smaller than 90 de-grees at least at the outer edge of the grate lifter 27.
According to another embodiment, the angle a may be smaller 5 than 88 degrees. According to another embodiment, angle a may be in the range of 20 to 70 degrees. According to a further embodiment, the angle a may be in the range of 30 to 60 degrees. According to yet another embodi-ment, the angle a may be about 45 degrees.
According to an embodiment, the angle a may vary along the

10 length of the grate lifter guiding surface 30. According to an embodiment, the angle a may be reversed at a point of the grate lifter guiding surface 30. In such embodiments, thus, the angle at the inner end of the grate lifter and/or at a point along the grate lifter guiding surface may be different from the an-gle a. With such embodiments, an improved movement of the ground materi-al along the grate lifter guiding surface 30 may be achieved. An embodiment, where the angle is reversed at a point of the grate lifter guiding surface, may be particularly beneficial for guiding the ground material to the pulp lifter.

According to an embodiment, the grate lifter and the pulp lifter may be arranged lying on top of each other, and the angle may extend across both grate lifter and the pulp lifter. Thus, the inside face of both the grate lift-er and the pulp lifter may be angled.
Grate lifter may comprise a radial, curved or a spiralling form.
Thus, depending on the intended use, combinations of grate lifter form and pulp lifter vane form may be combined in different ways, such as by combin-ing radial grate lifters and radial pulp lifter vanes, spiralling grate lifters and spiralling pulp lifter vanes, radial grate lifter and spiralling pulp lifter vanes or spiralling grate lifter and radial pulp lifter vanes.
According to an embodiment, the same angle 0 may be extended also to the grate lifter, that is the grate lifter guiding surface and the pulp lift-er guiding surface may have a same angle. These guiding surfaces may even form a continuous guiding surface on both sides of the grate.
According to an embodiment, the grinding mill may comprise a wet grinding mill. The grinding mill may then further comprise at least one inlet for receiving a continuous feed of a process liquor. Depending on em-bodiment, this inlet for process liquor may comprise the inlet 21 or a sepa-

11 rate inlet for the process liquor.
According to an embodiment, the grinding mill 3 may comprise at least one of the following: a grate discharge ball mill, a SAG mill, and an AG

mill.
According to an embodiment, an outer pulp lifter element, an in-ner pulp lifter element and/or a pulp lifter may comprise a spare part of a grinding mill. According to an embodiment, such a spare part may be retrofit-ted to an existing grinding mill. The pulp lifter and its structural parts de-scribed in this description, such as the outer pulp lifter element, the inner pulp lifter element and the grate lifter, may be retrofitted to an existing grinding mill, even though it would originally be of a conventional design, such as conventional radial or spiral pulp lifter and/or grate lifters in existing grinding mills. In other words, the structural parts of a grinding mill of a con-ventional design may be replaced by structural parts described in this de-scription. Thereby, a more smooth and efficient flow of the ground material can be achieved and even a longer life cycle of the spare parts.
It will be obvious to a person skilled in the art that, as the technol-ogy advances, the inventive concept can be implemented in various ways.
The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

12

1. An outer pulp lifter element (1) for a pulp lifter (2) for a rotat-ing drum grinding mill (3), the outer pulp lifter element (1) forming a sector or a truncated sector of an outer pulp lifter and comprising a first wall (4) directed towards the discharge end of the grinding mill, and at least one vane (6) protruding from the inner surface (12) of the first wall (4) towards the inside of the drum grinding mill (3), extending from an outer part of the outer pulp lifter element (1) towards the inner end (9) of the outer pulp lifter element (1), and comprising a guiding surface (10) on the front side of the vane (6) first receiving the ground material, c h ar-acterized in that at least a part of the outer edge (11) of the guiding surface (10) is angled in relation to the inner surface (12) of the first wall (4) in such a man-ner, that the angle (0) between the inner surface (12) of the first wall (4) and the outer edge (11) of the guiding surface (10) is in the range of 20 to 70 de-grees, thereby forming a pocket in the pulp lifter (2) and the guiding surface (10) directing the ground material flow towards the back of the pulp lifter;
and that either the vane (6) has an equal angle between the inner surface (12) of the first wall (4) and the guiding surface (10) along the whole length of the guiding surface (10), or the angle between the inner surface (12) of the first wall (4) and the guiding surface (10) of the vane (6) varies along the length of the guiding surface (10).

2. An outer pulp lifter element (1) according to claim 1, wherein the angle (0) between the inner surface (12) of the first wall (4) and the outer edge (11) of the guiding surface (10) is in the range of 30 to 60 degrees.

3. An outer pulp lifter element (1) according to claim 1 or 2, wherein the vane (6) extends radially from the outer part of the outer pulp lifter element towards the inner end of the outer pulp lifter element.

4. An outer pulp lifter element (1) according to any one of claims 1-3, wherein the vane (6) extends from the outer part of the outer pulp lifter element towards the inner end of the outer pulp lifter element in a curved manner.

5. An outer pulp lifter element (1) according to any one of claims 1, 2 or claim 4, wherein the outer pulp lifter element (1) comprises a second surface (7) substantially perpendicular to the first wall (4), extending in a radial direction (B) of the pulp lifter (1), forming a front surface of the pulp lifter element (1) in the direction of rotation (C) of the pulp lifter (2), and comprising an opening (8) for receiving ground material from an adjacent outer pulp lifter element, such that the direction of the inner surface (12) of the first wall (4) is defined by the first wall (4) side edge of the opening (8) extending in the direction (A-A') parallel to the head of the mill and the radial direction (B) of the pulp lifter (1), the outer edge (11) of the guiding surface (10) comprises the out-er edge of the opening (8), and the angle (0) between the inner surface (12) of the first wall (4) and the outer edge (11) of the guiding surface (10) comprises the angle be-tween the first wall (4) side edge of the opening (8) and the outer edge of the opening (8).

6. An outer pulp lifter element (1) according to any one of claims 1-5, wherein the vane (6) has an equal angle between the inner surface (12) of the first wall (4) and the guiding surface (10) along the whole length of the guiding surface (10).

7. An outer pulp lifter element (1) according to any one of claims 1-6, wherein the angle between the inner surface (12) of the first wall (4) and the guiding surface (10) of the vane (6) varies along the length of the guiding surface (10), whereby the angle between the inner surface (12) of the first wall (4) and the guiding surface (10) of the vane (6) at the inner end of the vane and/or at a point along the guiding surface of the vane is different from the angle (0) between the inner surface (12) of the first wall (4) and the outer edge (11) of the guiding surface (10).

8. An outer pulp lifter element (1) according to any one of claims 1-7, wherein the outer pulp lifter element comprises solid cast steel material.

9. An outer pulp lifter element (1) according to any one of claims 1-7, wherein the outer pulp lifter element comprises rubber material finish with steel frame provided inside.

10. An outer pulp lifter element (1) according to any one of claims 1-9, wherein the outer pulp lifter element comprises an elastomer material.

11. A pulp lifter (2) for a rotating drum grinding mill (3), ch a r -a cterize d in that the pulp lifter (2) comprises at least one outer pulp lifter element (1) according to any one of claims 1-10.

12. A pulp lifter (2) according to claim 11, wherein the pulp lifter comprises an inner pulp lifter (16) and wherein the vane (6) extends to said inner pulp lifter (16).

13. A pulp lifter (2) according to claim 12, wherein at least a part of the guiding surface (17) of the inner pulp lifter part of the vane (6) is also angled in relation to the inner surface of the back wall (18) of the inner pulp lifter.

14. A pulp lifter (2) according to claim 13, wherein the guiding surface (17) of the inner pulp lifter part of the vane (6) is arranged on an op-posite side of the vane (6) on the area of the inner pulp lifter when compared to the area of the outer pulp lifter.

15. A grinding mill (3) comprising a cylindrical shell (20) arranged rotatably around its longitudinal axis (D) extending in a horizontal direction, at least one inlet (21) for receiving a continuous feed of material to be ground at least one outlet (22) for continuous discharge of the ground material, a grate (23) between the interior of the cylindrical shell (20) and the outlet (22) comprising openings for passing through ground material particles of a predetermined size or smaller, whereby the grate prevents par-ticles larger than the predetermined size passing through the grate, and a discharger (24) provided at the outlet (22) end of the grinding mill for discharge the ground material through the outlet (22), charac-terized in that a pulp lifter element (1) according to any one of claims 1-10 or a pulp lifter (2) according to any one of claims 11-14 is provided between the grate and the discharger for guiding the ground material from the cylindrical shell to the discharger (24).

16. A grinding mill (3) according to claim 15, wherein the vane (6) extends to said discharger (24).

17. A grinding mill (3) according to claim 16, wherein at least a part of the guiding surface (25) of the discharger part of the vane (6) is also angled in relation to the inner surface of the discharger wall (26).

18. A grinding mill (3) according to any one of claims 15-17, wherein the grate (23) comprises at least one grate lifter (27) arranged on the cylindrical shell interior side of the grate (23) for guiding particles of the ground material into the pulp lifter (2) through the openings in the grate (23), and wherein the outer edge (28) of the grate lifter guiding surface (30) is angled in relation to a grate wall (29) facing towards the interior of the cylindrical shell (20) in such a manner, that the angle (a) between the grate wall (29) and the grate lifter guiding surface (30) is smaller than 90 degrees at least at the outer edge of the grate lifter (27).

19. A grinding mill according to any one of claims 15-18, wherein the grinding mill comprises a wet grinding mill and comprises at least one inlet for receiving a continuous feed of and process liquor.

20. A grinding mill according to any one of claims 15-19, wherein the grinding mill comprises at least one of the following: a grate discharge ball mill, a SAG mill, and an AG mill.