EP3541523B1 - Mill - Google Patents

Description

The present invention relates to a mill according to the preamble of claim 1.

Mills are used to crush solids such as coal, minerals or pigments. A distinction is made between pendulum mills, impact mills, bowl mills, roller mills or jet mills according to the type of their construction, this list being only exemplary.

Pendulum mills are characterized by their grinding tools designed as pendulums. These pendulums are suspended from a crosshead, which sits on a shaft, and are pressed radially outwards by the rotational movement of the shaft and the crosshead and against a grinding path located there. Grist gets between the grinding pendulum and the grinding track during the grinding process and is crushed there.

The ground material is then sifted through. During the screening, the sufficiently small particles (fine material) are removed and particles with an excessively large particle size (coarse material) are fed back into the mill in order to be further crushed. This creates a material cycle that particles go through until the desired particle size is reached.

Such a pendulum mill is from, for example DE 10 2009 051 226 A1 known. In this known pendulum mill, a classifier is arranged directly above the grinder. The coarse material is returned via a screw, by means of which the coarse material is first conveyed from the area between the classifier and the pendulum mill to outside with fresh feed material, ie the solid to be ground to be mixed. This mixture is then fed to the pendulum mill above the grinding area. This return is very complex and energy-intensive.

She takes a different path US 5,330,110 , which discloses a pendulum mill with an integrated sifter and a particle circulation device. During particle circulation, all particles are accelerated radially outwards by a rotor and hit the outer wall of the pendulum mill. Coarse and fine particles separate there. In addition, there are the coarse particles on the classifier. All coarse particles are returned to the area below the pendulum through downpipes outside the mill housing. The coarse particles are transported from below into the grinding area again by the flow created within the mill housing and further crushed.

The pendulum mill is similar US 5,279,466 built up. There, however, the coarse material is introduced into the grinding area from above. In both cases, the construction space of the pendulum mill increases, which is disadvantageous.

Alternatively, the return of the coarse material can be carried out in accordance with US 4,830,290 also take place inside the mill housing. With this type of return, however, opposing flows arise: those of the ascending particles moving in the direction of the classifier and those of the falling particles of the coarse material. These two currents interfere, which among other things means that particles that have not yet been sighted are carried away by the coarse material. As a result, particles that are already small enough end up in the grinding area again and may be further crushed. This is undesirable. Overall, the opposite currents lead to an increased power consumption and to a lower throughput of the mill.

The US 2009/0121060 A1 tries to solve this problem by placing a tubular insert in the mill housing. An annular space is formed between the insert and the outer wall of the mill housing, which is provided for the falling particles of the coarse material. The particles rising from the mill area, however, are inside the insert. In this way, the two particle flows are to be separated, thereby avoiding the disadvantages described.

The solution of US 2009/0121060 A1 however, is disadvantageous for several reasons. Firstly, the annular space is very narrow and it is questionable whether the coarse material actually finds its way into the annular space. There is also the possibility that the annulus becomes blocked. Finally, the direct return to the grinding pendulum is not guaranteed. The coarse material passes through the annular space into an area laterally above the grinding rollers. Due to the ascending flow, there is the possibility that particles will not be further crushed at all, but will be swept away by the flow and fed to the classifier. This reduces the throughput of the mill because the particles have to go through the entire cycle again.

From the DE 10 2011 014 592 A1 a roller mill with an integrated classifier is known which has a grinding bowl which rotates about a longitudinal axis of the mill. The grinding bowl is provided with a grinding track on which a feed bed is formed from the feed material. Stationarily arranged grinding rollers roll off the grinding bed.

The coarse material rejected by the classifier falls into a semolina cone, which has an opening on the bottom, which enables the coarse grain to be fed centrally to a distribution cone. Due to turbulence in the grinding chamber, only part of the returned coarse material reaches the grinding rollers.

It is therefore an object of the invention to provide a mill which enables a higher throughput than previous mills.

This object is achieved by a mill with the features of claim 1.

The mill has a mill housing with an interior, in which there is a grinding chamber B1, in which a grinding device with at least one grinding tool is arranged. The classifier is arranged above the grinding device in a classifying room B3 and has a viewing zone. At least one drop device is provided which connects the viewing zone to the grinding chamber. The mill is characterized in that at least one distribution plate is arranged under the classifier, which has at least one drop opening, on which the at least one drop device is arranged.

The mill is preferably a pendulum mill with a rotating grinding device that has at least one grinding tool. The grinding tool preferably has a grinding pendulum with a rotatably mounted grinding roller or grinding roller, which rotates, for example, on a stationary grinding ring. According to a further embodiment, the mill can be a roller mill with a stationary grinding device, which has at least one grinding tool. The grinding tool preferably has a stationary grinding pendulum with a rotatably mounted grinding roller or grinding roller, which interacts, for example, with a rotating grinding bowl.

The grinding track is the surface on which the grinding roller or roller rolls on the grinding ring or grinding bowl.

The longitudinal axis X of the mill is preferably a vertical axis and is preferably identical to the axis of rotation of the mill.

The coarse material rejected by the classifier falls onto the distribution plate arranged under the classifier and from there passes through the at least one drop opening into the relevant fall device. This has the advantage that the coarse material is immediately channeled within the mill housing, so that it largely does not come into contact with the ground material / air flow flowing from the grinding chamber. Through this type of separation of the two flows, the throughput of the mill could be increased by up to 20%. As a result, more regrind per unit of time can be comminuted with the mill according to the invention and the mill can accordingly be operated more economically.

The interior of the mill housing of the mill is in the direction of gravity, i.e. H. from top to bottom, divided into three areas. The viewing area is located in an upper area, which preferably extends from a mill ceiling to a lower edge of the viewing wheel. The grinding area, in which the grinding rollers of the grinding tools are arranged, is located in a lower area. Between these two rooms there is a transport room in which the ground goods are transported upwards to the classifier and the coarse goods rejected by the classifier fall downwards.

The valve disk is located in the transport space, preferably in the upper area of the transport space.

The diameter of the distributor plate is preferably greater than or equal to the diameter of the classifier wheel, in particular greater than or equal to the outer diameter of the classifier. This ensures that all of the coarse material that falls from the classifier sifter zone is captured by the distribution plate.

A circumferential boundary wall is preferably arranged between the classifier and the distribution plate. The boundary wall prevents that from Coarse material falling gently down next to the distributor plate falls down and thus does not get into the drop opening.

The height of the peripheral boundary wall is preferably equal to or less than the distance between the classifier and the distributor plate. The boundary wall preferably has an upper circular edge and a lower circular edge. The diameter of the upper circular edge is preferably larger than the inner diameter of the guide vane ring, in particular larger than the outer diameter of the guide vane ring. The diameter of the lower circular edge is preferably smaller than the diameter of the distribution plate.

Depending on the dimensions of the diameters of the classifier and distributor plate, the circumferential boundary wall can be a cylinder or a cone. A conical boundary wall with a smaller diameter of the lower edge compared to the diameter of the upper edge is used in particular when the diameter Dv of the distributor plate is smaller than the diameter D ₁ or D ₂ .

The circumferential boundary wall is preferably fixed in place on the classifier housing.

In order to distribute the coarse material as evenly as possible, the distributor plate has several drop openings and thus also several drop devices.

Preferably, several drop openings are provided in the distribution plate, which are arranged distributed on a circle K ₁ around the longitudinal axis X of the mill, the diameter of the circle K ₁ preferably being in the range between the diameter of the classifier wheel and the outside diameter of the classifier. In order to prevent a collision of the falling coarse material with the flowing regrind / air flow, a cylindrical wall can also be arranged between the classifier and the distributor plate. The diameter of the cylindrical wall preferably corresponds to the diameter of the distribution plate.

The at least one drop device is preferably arranged in the interior of the mill housing, in particular within the transport space. The advantage is that the mill can be made compact.

Another advantage of the falling device is that the coarse material not only reaches the grinding chamber by means of the falling device, but can also be discharged there specifically at the location where the grinding process takes place.

The at least one falling device preferably extends as far as the respective grinding roller or grinding roller.

In this way, the two flows (coarse material from the classifier to the grinding chamber and ground material from the grinding chamber to the classifier) are separated from one another more effectively. Opposing currents, which hinder each other and lead to turbulence, are largely avoided not only in the transport area, but also in the grinding area.

In order to bring the coarse material as close as possible to the area in which it is to be ground, in an advantageous further development it is provided that the at least one falling device is in each case assigned to at least one grinding tool and that the falling device in the grinding chamber extends to the respective grinding tool.

The at least one falling device preferably extends as far as the respective grinding roller or grinding roller.

In advantageous developments of the mill, it is provided that at least one falling device is arranged between two grinding devices. A falling device is preferably arranged between two grinding tools. The mill particularly preferably has the same number of grinding tools, drop openings and drop devices.

Particularly preferably, at least one outlet of the dropping device is directed onto the mill floor and / or a grinding track and / or a grinding roller.

The outlet direction of the outlet of the dropping device influences the grinding process. The outlet direction is understood to mean the direction in which the coarse material flows from the falling device after leaving the falling device. The outlet direction is in particular arranged perpendicular to an outlet surface of the outlet. The outlet surface is in particular a surface which closes the outlet opening in the falling device. The outlet surface is preferably a plane parallel to the longitudinal axis of the mill.

In advantageous developments of the mill, it is provided that a horizontal component of the outlet direction of at least one falling device lies at an outlet angle γ to a radial direction of a circle K ₂ on which the falling devices are arranged, 70 ° <γ <110 °.

The radial direction that runs through the vertical axis of the associated drop device is considered for a specific outlet. The intersection of the radial direction to be considered with the outlet direction lies on the vertical axis of the associated fall device. The radial direction and the outlet direction form the outlet angle γ. The circle K ₂ is a circular path on which the vertical axes of the falling devices lie or on which the vertical axes of the falling devices move when used as intended, as is preferably the case when used in a pendulum mill. In this way, the coarse material emerges essentially in or against the direction of rotation of the falling devices. The exit against the direction of rotation means that less turbulence is created in the grinding chamber.

It is also advantageous to arrange the horizontal component of the outlet direction of at least one drop device to the radial direction at an outlet angle γ, where -30 ° <γ <+ 30 ° applies. As a result, the coarse material exits essentially along the radius of the circle K ₂ . In this case, the outlet opening from the circle K ₂ can be directed inwards towards the center or outwards. If the outlet opening is directed outwards, the coarse material exits in the direction of the grinding path, as a result of which the coarse material arrives directly in the area in which it is to be ground.

In advantageous developments of the mill, it is provided that at least one falling device tapers at the lower end or has a smaller cross section than the rest of the falling device. This version of the falling device is used in particular when only a small amount of coarse material has to be transported from the viewing zone to the grinding area. If the opening for the coarse material is too large in relation to the amount of coarse material, there can be an insufficient flow.

The at least one falling device preferably has a curved section with an outlet at a lower end.

As a result, the outlet of the falling device can be aligned such that the coarse material from a falling device in a certain direction, in a certain direction Area of the mill or on a specific component of the mill is transported.

The falling device preferably comprises a falling space, a falling pipe and / or a falling hose, which is separated in the interior of the mill housing. The drop area can be separated, for example, by appropriate internals within the mill housing. The cross section of the fall devices can be chosen as desired, with round or polygonal cross sections being preferred for production reasons.

According to a special embodiment, the grinding device and the at least one falling device are arranged so as to be rotatable about the longitudinal axis X. The common rotation of grinding device and falling device or falling devices is preferably used in a pendulum mill.

The distributor plate is preferably arranged on a rotating grinding device.

The pendulum mill has a drive shaft to which the grinding device is attached. The grinding device preferably has a crosshead on which the grinding pendulums are suspended. The at least one distribution plate is preferably fastened to a drive shaft of the mill or to a crosshead fastened to the drive shaft.

The arrangement of the drop openings and thus also the drop devices on a circle enables a uniform load distribution for the crosshead or the drive shaft. Other arrangements can lead to uneven stress, particularly on the drive shaft, thereby reducing its service life.

The material to be ground (ground material) tends to be deposited on a mill base of the mill housing. In an advantageous development of the mill, at least one blade is arranged in the mill housing, each blade being assigned a drop device. The blades are preferably arranged on the mill base and likewise rotate about the axis of rotation X and transport the ground material from the mill base in the direction of the respective grinding roller or the grinding track.

At least one outlet of the falling device is preferably directed onto a blade.

Figur 1

eine Pendelmühle in einer perspektivischen, geschnittenen Darstellung,

Figur 2

die Mahleinrichtung der Pendelmühle mit Verteilteller gemäß Figur 1 in einer perspektivischen Darstellung,

Figur 3

ein Verteilteller der Pendelmühle in einer Draufsicht,

Figur 4

den Verteilteller sowie die Fallrohre einer Pendelmühle in einer perspektivischen Darstellung,

Figur 5

den Verteilteller sowie die Fallrohre einer Pendelmühle gemäß einer weiteren Ausführungsform in einer perspektivischen Darstellung und

Figur 6

eine schematische Darstellung von Teilen einer Pendelmühle gemäß einer weiteren Ausführungsform.

The invention is illustrated and explained below using the figures as an example. Show it:

Figure 1

a pendulum mill in a perspective, sectional view,

Figure 2

the grinding device of the pendulum mill with distribution plate according to Figure 1 in a perspective view,

Figure 3

a distribution plate of the pendulum mill in a plan view,

Figure 4

the distribution plate and the downpipes of a pendulum mill in a perspective view,

Figure 5

the distribution plate and the downpipes of a pendulum mill according to a further embodiment in a perspective view and

Figure 6

is a schematic representation of parts of a pendulum mill according to another embodiment.

Figure 1 shows an embodiment of a mill 10, which is designed as a pendulum mill. The pendulum mill 10 has a longitudinal axis X, which also forms the axis of rotation at the same time. The pendulum mill 10 has a mill housing 20 with an interior 20a which is delimited by a peripheral wall 22, a mill ceiling 25 and a mill floor 21.

The interior 20a of the mill housing 20 is divided into three rooms B1, B2 and B3, which are referred to as grinding room B1, transport room B2 and viewing room B3.

The classifier 100, which has a classifying wheel 110 with the diameter D ₁ , is arranged in the classifying room B3. The classifying wheel 110 is driven by a classifying shaft 114. The classifier 100 also has a guide vane ring 111 which surrounds the classifying wheel 110 and which has the outside diameter D ₂ . The viewing zone 102 of the classifier 100 is located between the classifier wheel 110 and the guide vane ring 111.

Under the sifter 100 there is a grinding device 80 with a crosshead 88 and three grinding tools 81 in the form of grinding pendulums 82, two of which are shown. Each grinding pendulum 82 has a pendulum shaft 84 with a grinding roller 86. The grinding rollers 86 are located in the grinding room B3.

The grinding pendulums are pivotally attached to the crosshead 88. When used as intended, the grinding pendulums 82 are pressed against the grinding track 23 of the grinding ring 27 of the mill housing 20. The ground material is ground between the grinding spaces 86 and the grinding path 23.

A drive device (not shown) which drives a drive shaft 30 is arranged below the mill housing 20. The drive shaft 30 extends from the drive device into the mill housing 20. The crosshead 88 of the grinding device 80 is arranged at the upper end 34 of the drive shaft 30.

The grinding area B1 extends from the mill floor 21 up to an upper edge 26 of the grinding track 23. The viewing area B3 extends from a mill ceiling 25 to a lower edge 116 of the classifier wheel 110. The transport area B2 is located between the areas B1 and B3, in which the distributor plate 40, the crosshead 88 and the pendulum shaft 84 are arranged. The grinding pendulums 82 extend from the crosshead 88 into the grinding chamber B1.

A distribution plate 40 with a diameter Dv which is larger than the outer diameter D _{2 of} the classifier 100 is arranged in the transport space B2 above the crosshead on the drive shaft 30. The distribution plate 40 is rotatably driven by the drive shaft 30 when used as intended. As a result, the distributor plate 40 also rotates about the axis of rotation X. The distributor plate 40 has a round disk in which drop openings 42 are arranged. A distributor cone 43 is arranged in the middle of the distributor plate 40. Of the several drop openings 42, only one drop opening 42 is shown, to which a downwardly extending drop device 60 in the form of a drop tube is fastened.

During operation, the regrind air flow in transport space B2 rises, which is indicated by arrows P1. At the same time, the coarse material is rejected by the classifier 100 in the viewing zone 102 and falls down onto the distribution plate 40, which is indicated by the arrows P2. A circumferential boundary wall 130 is arranged between the classifier 100 and the distribution plate 40, which contacts the currents P1 and P2 in the upper region of the transport space B2 prevented. The boundary wall 130, which is arranged stationary, is designed as a cylinder, the height of which is less than / equal to the distance between the classifier 100 and the distributor plate 40. The diameter of the upper edge of the cylinder is larger than the diameter D _{2 of} the classifier 100. The diameter of the lower cylinder edge is less than / equal to the diameter Dv of the distributor plate 40.

A regrind supply 90 is arranged on the mill housing 20 and has a chute 92 which extends from a region outside the mill housing 20 into the interior of the mill housing 20. A regrind outlet 94 is arranged above the grinding chamber B1 in the transport chamber B2. The material to be ground is introduced into the mill housing by the ground material supply 90.

A suction device 112 is arranged above the classifier 100. The suction device 112 is connected to the interior of the classifying wheel 110 and generates a flow which serves to cause the material ground between the grinding rollers 86 and the grinding track 23 to rise. The material flows from the grinding chamber B1 outside the boundary wall 130 through the transport chamber B2 and into the viewing chamber B3. In the viewing space B3, the material is initially outside the guide vane ring 111 of the classifier 100. Due to the flow generated by the suction device 112, the material reaches the viewing zone 102 through the guide vane ring 111. The classifying wheel 110 separates the material into coarse and fine material. The fine material enters the interior of the classifying wheel 110 and is removed from the mill housing 20 by the suction device 112. The coarse material is rejected by the classifier wheel 110 and, as already described, falls onto the distribution plate 40.

The Figure 2 essentially shows the arrangement of the grinding device 80 in combination with the distributor plate 40 with the distributor cone 42 arranged on the upper side 45 and the drop devices 60 from FIG Figure 1 . Other parts of the pendulum mill are hidden for the sake of illustration.

The distributor plate 40 has three drop openings 42, which are arranged on a circle K ₁ . The center of the circle K ₁ lies in the axis of rotation X. The drop openings 42 are arranged on the circle K ₁ at uniform angular intervals around the axis X. D denotes the direction of rotation of the distribution plate 40. Falling devices 60, which are designed as down pipes, are fastened to the fall openings 42.

In the illustration shown here, the pendulum mill 10 has three downpipes 60. A grinding pendulum 82 is arranged between each two downpipes 60 along an orbit U (circle K ₂ ) of the downpipes 60. A downpipe 60 is likewise arranged along the orbit U between two grinding pendulums 82 in each case. The downpipes 60 are interconnected by struts 68. Vibrations of the downpipes 60 are prevented during operation by the struts 68. Shovels 24 are shown below the downpipes 60, which are connected to the drive shaft 30 via a support structure 28 and are rotatably driven by the latter. The blades 24 move ground material which has deposited on the mill base 21 in the direction of the grinding path 23 in order to be ground between the grinding rollers 86 and the grinding path 23.

A downpipe 60 is thus assigned to each blade 24. In the present case, the outlets 62 of the downpipes 60 are oriented in such a way that the material from the downpipe 60 directly meets the blade 24 after it has left the outlet 62 and is thus immediately fed to the grinding roller 86.

In the Figure 3 the top view of the distribution plate 40 is shown enlarged. It can be seen that the drop openings 42 are arranged on the circle K ₁ . The distribution cone 43 is located in the center of the distribution plate 40.

In the Figure 4 An embodiment is shown in which each down pipe 60 tapers at a lower end 64 and merges there into a curved section 61.

Another embodiment is in the Figure 5 shown. The downspouts 60 do not taper, but each have a curved section 61 at a lower end 64.

Figure 6 shows a schematic bottom view of the grinding device 80 with different arrangements of the downpipes 60. Each downpipe 60 has a vertical axis H. The drop openings 42 of the downpipes 60 are arranged on a circle K ₁ around the axis of rotation X. The circle K ₁ has radial directions R. Of the radial directions R, those are shown which run through the vertical axes H of the downpipes 60. The downpipes 60 each have an outlet direction A. In the Figure 6 all outlet directions A are horizontal. The outlet directions A are each arranged at an angle γ to the radial direction R of the associated downpipe. In two of the downpipes 60 shown, the angle γ is between -30 ° and + 30 °, in the other two downpipes 60 the angle γ is between 70 ° and 110 °.

Reference list

10th

Mill, pendulum mill

20

Mill housing

20a

inner space

21

Mill floor

22

Peripheral wall

23

Grinding track

24th

shovel

25th

Mill ceiling

26

Top edge

27

Grinding ring

28

Support structure

30th

drive shaft

34

top end

40

Distribution plate

42

Case opening

43

Distribution cone

45

Top

60

Falling device, downpipe

61

curved section

62

Outlet

64

lower end

68

strut

80

Grinding device

81

Grinding tool

82

Grinding pendulum

84

Pendulum shaft

86

Grinding roller

88

Crosshead

90

Grist supply

92

slide

94

Grist outlet

100

Classifier

102

Field of vision

110

Classifier wheel

111

Guide vane ring

112

Suction device

114

Classifier wave

116

Lower edge

130

Boundary wall

B1

Grinding room

B2

Transport space

B3

Visual space

A

Outlet direction

D

Direction of rotation of the distributor plate

D ₁

Diameter of the classifier wheel

D ₂

Outside diameter of the guide vane ring, outside diameter of the classifier

Dv

Diameter of the distribution plate

H

Vertical axis

K ₁

circle

K2

circle

P1

Flow arrow

P2

Flow arrow

R

Radial direction

U

Orbit

X

Axis of rotation, longitudinal axis

γ

angle

Claims (15)

1. Mill (10), in particular pendulum mill or roller mill, having a longitudinal axis X and having a separator (100),
   wherein the mill (10) has a mill housing (20) having an inner space (20a), in which there is located a milling chamber (B1) in which a milling device (80) having at least one milling tool (81) is arranged,
   wherein the separator (100) is arranged above a milling device (80) in a separation chamber (B3) and has a separation zone (102), and
   wherein there is provided at least one drop device (60), which connects the separation chamber (B3) to the milling chamber (B1),
   characterised in that
   there is arranged below the separator (100) at least one distributor plate (40, 140) which has at least one drop opening (42) on which the at least one drop device (60) is arranged.
2. Mill according to claim 1, characterised in that the diameter Dv of the distributor plate (40) is greater than or equal to the diameter D₁ of the separation wheel (110).
3. Mill according to claim 1 or claim 2, characterised in that a peripheral boundary wall (130) is arranged between the separator (100) and the distributor plate (40).
4. Mill according to any one of claims 1 to 3, characterised in that
   a plurality of drop openings (42) which are arranged in a circle K₁ are provided in the at least one distributor plate (40).
5. Mill according to any one of claims 1 to 4, characterised in that
   the at least one drop device (60) is associated with at least one milling tool (81), and
   in that the drop device (60) extends in the milling chamber (B1) as far as the respective milling tool (81).
6. Mill according to any one of claims 1 to 5, characterised in that
   at least one drop device (60) is arranged between two milling tools (81).
7. Mill according to any one of claims 1 to 6, characterised in that
   at least one outlet (62) of the drop device (60) is directed towards a mill base (21) and/or a milling track (23) and/or a milling roller (86).
8. Mill according to any one of claims 1 to 7, characterised in that
   a horizontal component of an outlet direction A of the outlet (62) of at least one drop device (60) is located at an angle γ with respect to a radial direction R of a circle K₂, in which the drop devices (60) are arranged, wherein 70° < γ < 110°.
9. Mill according to any one of claims 1 to 8, characterised in that
   a horizontal component of an outlet direction A of the outlet (62) of at least one drop device (60) is located at an angle γ with respect to a radial direction R of a circle K₂, in which the drop devices (60) are arranged, wherein -30° < γ < +30°.
10. Mill according to any one of claims 1 to 9, characterised in that
    the at least one drop device (60) has at a lower end (64) a curved portion (61) having an outlet (62).
11. Mill according to any one of claims 1 to 10, characterised in that
    the drop device (60) comprises a drop space which is separated in the inner space (20a) of the mill housing (20), a drop pipe and/or a drop hose.
12. Mill according to any one of claims 1 to 11, characterised in that
    the milling device (80) and the at least one drop device (60) are arranged so as to be able to be rotated about the longitudinal axis X.
13. Mill according to any one of claims 1 to 12, characterised in that
    the at least one distributor plate (40) is secured to a drive shaft (30) of the mill (10) and/or to a cross-head (88) which is secured to the drive shaft (30).
14. Mill according to any one of claims 1 to 13, characterised in that
    at least one blade (24) is arranged in the mill housing (20), wherein a drop device (60) is associated with each blade (24).
15. Mill according to any one of claims 1 to 14, characterised in that
    at least one outlet (62) of the drop device (60) is directed towards a blade (24).

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