Note: Descriptions are shown in the official language in which they were submitted.
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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-
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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.
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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-
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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
2
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
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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
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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-
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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
12
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-
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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
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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-
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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-
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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.
