EP3799960A1 - Agitator mill - Google Patents

Abstract

The invention provides an agitator mill for treating flowable grist. The agitator mill has a grinding container, a grinding chamber which is delimited by a container wall, and an agitator with a rotor that can be rotated about the central longitudinal axis. Tools are attached to the rotor and extend in the direction of the container wall. The agitator mill also has an inner stator which is arranged inside the rotor. A regrind discharge channel is formed between the rotor and an outer wall of the inner stator, through which the regrind is guided to the separating device and then to a discharge line. The grinding chamber is at least partially filled with grinding media. A separating device is arranged above the inner stator. In the direction of flow of the ground material, a ground material discharge space is formed behind the grinding body separating device. A device for setting a minimum level and / or a device for reducing the volume is installed in the grinding stock discharge space.

Description

The invention relates to an agitator mill according to the preamble of claim 1.

The invention refers to the European patent specification EP 1 992 412 A1 . Such an agitator mill is known from this. Agitator mills are used to disperse suspensions, i.e. solids in liquids. This is used, for example, in the manufacture of adhesives, printing inks, cosmetics and pharmaceuticals. For this purpose, the ground material is fed via a feed channel into a grinding chamber of the agitator mill, which is formed between the outer wall of a rotor and a container wall, and is crushed together with auxiliary grinding bodies, such as ceramic balls, which are also referred to below as grinding bodies, and with the help of tools , which are arranged on the rotor and possibly also on the container wall. Agglomerates are dispersed and crystal structures are broken up by the stirring movement. The original particle size can be reduced from 100-500 µm to less than 3 µm. The finished product is then directed via a grinding material discharge channel through a grinding body separating device, in particular in the form of a protective sieve, into a grinding material discharge space arranged behind the separating device and then to a drainage line. The rotor forms a kind of rotating cage around the separating device.

The problem with such vertical agitator mills is that air remains in the area of the separating device after start-up. In operation, it is also desirable to keep the residence time distribution narrow and to allow plug flow in the device. Furthermore, with conventional agitator mills, deposits of the previous product can occur, which can negatively affect the quality of the subsequent product. This entails extensive cleaning after every product change. Cleaning devices that are used in conventional agitator mills have a displacement body which, due to the required mobility, has to be relatively small in its dimensions.

The invention aims to provide an improved agitator mill which overcomes these problems. Furthermore, the invention is intended to provide the possibility of realizing the improvements for existing agitator mills by a simple conversion.

The essence of the invention is to reduce the dead space volume behind or within the separating device. Furthermore, it can be achieved that a flow rate of the product is increased. By using a device to reduce the volume of the grinding material discharge space and in particular by inserting a cylindrical body, a so-called filling body, with a central opening, in particular generally in the form of a hollow cylinder, the dead space behind or within the separating device can be reduced. Furthermore, the filler body can be designed in such a way that it ensures a minimum level of the product. Furthermore, by means of a device for setting a minimum level, it can be ensured that product outflow is only possible above a certain minimum level. Both devices can also be used together. With the present invention, the dead space behind the separating device or the protective sieve of the agitator mill can therefore be reduced and / or the position of the product outflow can be shifted upwards. By reducing the volume of the grinding material discharge space, the flow rate is also increased and, as a result, contamination of the channel walls can be reduced or largely avoided by the material flowing through.

In particular, the agitator mill according to the present invention has a grinding container and a grinding chamber, which is delimited by a container wall and is at least partially filled with grinding media, and an agitator with a rotor which can be rotated about a central longitudinal axis which is essentially vertical during operation. An inner stator is arranged inside the rotor. A grinding material discharge channel is formed between the rotor and an outer wall of the inner stator, through which the grinding material is guided through a grinding body separating device in the direction of a discharge pipe. The grinding media separating device is preferably designed in the form of an essentially vertically arranged cylinder, in particular a cylinder sieve, with a height H. In the direction of flow of the ground material, a ground material discharge space is formed behind the grinding body separating device. In the Mahlgutabführraum is a device for setting a minimum level of the Product arranged within the Mahlgutabführraums. The interior of the separating device preferably forms the regrind discharge space and the minimum level in the regrind discharge space is greater than or equal to 0.85 H.

The invention further comprises an agitator mill for treating flowable material to be ground with a grinding container and a grinding space which is delimited by a container wall of the grinding container and is at least partially filled with grinding media. Furthermore, the agitator mill has an agitator with a rotor that is rotatable about a central longitudinal axis which is essentially vertically arranged during operation. An inner stator is arranged inside the rotor. A grinding material discharge channel is formed between the rotor and an outer wall of the inner stator, through which the grinding material is guided through a grinding body separating device in the direction of a discharge pipe. In the direction of flow of the ground material, a ground material discharge space is formed behind the grinding body separating device. A device for reducing the volume of the grinding material discharge space is arranged in the grinding stock discharge space.

The grinding media separating device is preferably designed in the form of an essentially vertically arranged cylinder with a height H, the interior of which forms the grinding stock discharge space. The device for reducing the volume of the Mahlgutabführraums can be formed by a filler body. The filling body preferably closes product-tightly with a discharge base of the agitator mill and has an overflow height h of the product in the vertical direction, the height H of the grinding body separating device being greater than the overflow height h. Preferably, h is greater than or equal to 0.85 H, particularly preferably greater than or equal to 0.95 H.

The filling body is preferably an essentially cylindrical hollow body. The device for reducing the volume of the Mahlgutabführraums can be made of plastic or metal or ceramic. The device for reducing the volume of the grinding material discharge space can be designed to be temperature-controlled.

The separating device is preferably a cylinder screen. The device for reducing the volume of the grinding stock discharge space can also be removable.

The device for reducing the volume of the grinding material discharge space preferably reduces the volume of the grinding material discharge space by at least 70%.

Tools that protrude into the grinding chamber are preferably attached to the rotor and, if appropriate, to the container wall.

The device for setting a minimum level as described above can also be used in the agitator mill with the device for reducing the volume. Both devices can be used separately or together to achieve the object of the present invention.

The invention further comprises a method for operating and cleaning an agitator mill with the use of a device for reducing the volume of the grinding stock discharge space of the agitator mill as described above. As a result, when the agitator mill is in operation, the flow rate of the grist through the grist discharge space is high enough to reduce product deposits, in particular in the grist discharge space of the agitator mill.

The dead volume behind the separating device can be reduced by the devices according to the invention for setting a minimum level in the grinding stock discharge space and / or for reducing the volume of the grinding stock discharge space, which can in particular be built into an existing agitator mill. This means that the mill can be almost completely filled before the grist can flow out. By increasing the outflow speed, a carry-over of the ground material is avoided, and this means that product loss and cleaning costs can be reduced. This is used by the cleaning method according to the invention.

• Fig. 1 einen Ausschnitt einer Rührwerksmühle gemäß einer Ausführungsform der Erfindung als vertikalen Längsschnitt,
• Fig. 2 eine schematische Schnittansicht eines Füllkörpers gemäß einer Ausführungsform der Erfindung und
• Fig. 3 eine Perspektivansicht eines Füllkörpers gemäß einer Ausführungsform der Erfindung.

Further features, advantages and details emerge from the following description of the invention with reference to the drawings. Show it

• Fig. 1 a section of an agitator mill according to an embodiment of the invention as a vertical longitudinal section,
• Fig. 2 a schematic sectional view of a filler body according to an embodiment of the invention and
• Fig. 3 a perspective view of a filling body according to an embodiment of the invention.

Figure 1 shows a longitudinal section through an agitator mill according to the invention. In a conventional manner, the agitator mill has a grinding container 2 with an internal grinding chamber 8. The grinding chamber 8 is at least partially filled with grinding media (not shown). The agitator mill also has an inner stator 22 and a rotor 35 rotatable about a central longitudinal axis 19. In this case, a grinding material discharge channel, which is also part of the grinding chamber 8, is formed between an outer wall 23 of the inner stator 22 and an inner wall of the rotor 35. Tools 38, which protrude into the space between the rotor 35 and a container wall 9 of the grinding container 2, can be attached to the rotor 35. The tools 38 can alternatively or additionally be arranged on the container wall 9. The grinding stock is usually poured into the agitator mill from above and ground in the grinding chamber 8 by means of the grinding media. At the lower end of the grinding chamber 8, the material to be ground is fed to the inside of the rotor 35, i.e. into the part of the grinding chamber 8 between the inner stator 22 and the inside of the rotor 35. There it flows upwards, where any grinding media that may have migrated to the outside into the grinding chamber 8 are deposited. Above the inner stator 22 there is a separating device 30, for example a cylindrical protective screen, which is designed to be rotationally symmetrical to the central longitudinal axis 19. The separating device 30 prevents the flow of grinding media into a downstream drain line 4, which is located inside the inner stator 22. The completely ground grist flows through the separating device 30 inward into the discharge line 4. Arrows in the Fig. 1 illustrate the direction of flow of the grist through the agitator mill. The agitator mill has an outflow base 42 below the grinding media separating device 30. This is arranged on the inside with respect to the grinding media separating device 30. The drainage line 4 is preferably arranged in the middle of the outflow base 42. Furthermore, the discharge base 42 can be designed to taper conically in the direction of the discharge line 4. In other words, a radially outer side of the outflow base 42 can be arranged higher in a vertical direction than the drainage line 4 during operation in order to simplify the product flow into the center and thus in the direction of the drainage line 4.

Within the separating device 30, a device for reducing the volume of the grinding material discharge space, in particular a filling body 1, is attached, which increases the volume of the Mahlgutabführraums behind the separating device 30 is reduced. This also reduces air inclusions in the product, which can increase the efficiency of the machine. The separating device 30 is preferably not closed, so that a product flow through the entire surface of the separating device 30 is ensured. This can be seen in the figure by a reduction in the cut surface in the area of the grinding material discharge space behind the separating device 30. In the following, reference is made to the device for reducing the volume of the grinding material discharge space as a filler body 1. The filling body 1 is preferably designed to be product-tight with the drainage base 4, so that the end product can only flow off above the filling body 1. The filling body 1 can be, for example, a cylinder with a central opening or a cylindrical hollow body. The filling body 1 can also be designed as an essentially cylindrical, rotationally symmetrical body. For example, the top and / or bottom of the filling body 1 can be completely or partially beveled. In the case of a hollow cylindrical shape, the upper and / or lower sides can each have a different inclination and / or inclination direction in the direction of the central longitudinal axis 19 than in the direction of the outside. Depending on the design of the separating device 30, different shapes of the filling body 1 can thus be expedient. In the case of a product-tight design with the drainage floor 42, a minimum level or a level that the product has in the malgut removal space is thus also ensured in a vertical agitator mill during operation. For this purpose, the filling body 1 has drainage channels 41 which define the overflow height h. However, the filling body 1 can also be smooth on the upper side, that is to say without channels. The height H of the separating device 30 is greater than the overflow height h of the filling body.

In particular, a minimum level of the product of at least 85% of the height of the grinding media separator through the packing should be guaranteed, so h ≥ 0.85 H applies to the overflow height h of the packing. Preferably, h is about 0.95 H. Through the shown packing 1 In addition, the volume of the grinding material discharge space is reduced, for example, by at least about 70% and the height of a channel 41, which is formed immediately behind the separating device 30 by the filler body 1 used, is reduced to, for example, about 10 mm, resulting in a flow rate of up to 2 m / s leads, with which an excellent cleaning of the grist discharge channel 4 can be achieved.

The filling body 1 can be designed to be removable. The filling body 1 can, however, also be designed or manufactured in one piece with the outflow base 42 or the cover of the grinding material discharge space.

In another preferred embodiment, the filling body 1 is designed in such a way that it does not end in a product-tight manner with the drainage base 42. Thus, only a reduction in the volume within the separating device 30, i.e. the grinding stock discharge space, is ensured, but not the above-mentioned minimum level of the product. For example, spacers can ensure a defined distance from the drainage floor 42, between which the product can run off.

The filling body 1 can also be designed to be temperature-controlled. It can thus be ensured that the insertion of the filling body 1 does not change or maintain the desired temperature of the product during the dispersing process. Furthermore, the packing 1 can be connected to an existing temperature system of the agitator mill, which is used in particular to cool the components of the agitator mill. The separating device 30 is generally designed to be static, i.e. the filling body 1 also does not perform any rotational movement. It is therefore easy to connect to the temperature system of the agitator mill. If the filling body 1 is made in one piece with the machine, the temperature control can already be provided during the manufacturing process.

According to a further preferred embodiment, a device for setting a minimum level can furthermore be provided, which, in the case of a vertical agitator mill, sets a minimum level of the product in the Malgutabführraum during operation. In other words, a minimum level or a minimum product level is ensured or guaranteed in the regrind discharge space. This reduces the dead space in the grist discharge space. This reduces the air pockets in the product and ensures faster and more efficient processing and flow of the product. This device for setting a minimum level can be provided separately from or in addition to the filler body 1. For example, the drain line 4 can be lengthened in such a way that it extends up to a certain height in the grist removal space, ie within the separating device 30. This height is preferably at least 0.85 H. In other words, the product level within the grist removal space is at least 0.85 H. Particularly preferred the height of the device for setting a minimum level of the product is 0.95 H. The device for setting a minimum level can be designed to be removable or in one piece with the drain line 4. The device ends in a product-tight manner with the drainage floor 42. The device for setting a minimum level can also be designed to be adjustable or controllable.

The packing according to the in Fig. 1 The embodiment shown is separated in a sectional view in FIG Fig. 2 shown. The filling body 1 is designed to be rotationally symmetrical and adapted to the grinding stock discharge space behind the separating device 30 of an existing agitator mill. Due to the special design of the filling body, the in Fig. 1 The channel 41 shown, which defines the overflow height h, is formed with a reduced cross section, as a result of which the flow rate is increased accordingly.

Fig. 3 shows a perspective view of the filling body 1 according to a preferred embodiment. A preferred arrangement of the channels 41 can also be seen here. Other arrangements or dimensions can also be expedient.

When the agitator mill is started up, the air in the outlet area should be displaced by the product as quickly as possible in order to avoid the formation of air cushions in the mill. So far, the product flows out of the agitator mill at the lowest point of the separating device, with the air remaining above in the agitator mill. By means of the filler body according to the invention and / or the device for setting a minimum level, the liquid or product drain can be moved upwards or to the highest point of the separating device. The dead space volume behind or within the separating device is thus reduced, since the product can only flow out above the filling body or the device for setting or ensuring a minimum level. This means that the mill can be completely filled before the grist flows out through the separating device.

After the product to be dispersed has passed the separating device, it should leave the agitator mill as quickly as possible. The residence time distribution should therefore be kept narrow and plug flow is preferred.

In conventional agitator mills, product deposits can occur precisely in the area of the product removal, i.e. in particular in the grist removal area and drainage line. This means that the agitator mill must be laboriously cleaned by the user before each product change, since the product deposits from the previous product may otherwise be present in the current production. Such product carry-over can have a negative impact on the quality of the subsequent product. By increasing the flow rate and avoiding air inclusions in the product by reducing the volume of the grinding stock discharge space and / or increasing the product level within the grinding stock discharge space according to the present invention, such deposits and the resulting product loss can be reduced or even avoided.

As described above, the object of the present invention can be achieved by setting a minimum level of the product in the grinding stock discharge space and / or by reducing the volume in the grinding stock discharge space. In particular, the embodiments can be used individually as alternative solutions or in combination in order to achieve the aim of the invention.

The invention further comprises a method for operating and cleaning an agitator mill by means of the above-described device for reducing the volume of the grinding stock discharge space. This achieves the advantages set out in the present description. Correspondingly, by using the device according to the invention for reducing the volume of the grinding stock discharge space according to the method according to the invention, when the agitator mill is operated, the flow rate of the grist through the grinding stock discharge space is high enough to reduce product deposits, especially in the grinding stock removal space of the agitator mill.

By inserting a filling body or cylindrical hollow body and / or a device for setting a minimum level according to the invention, the cleaning effort of the agitator mill and also the use of cleaning agents can be reduced. Furthermore, there is less product loss in production and a narrower and therefore more favorable residence time distribution. Air present in the agitator mill can be displaced when it is started.

The packing according to the invention can be used in existing vertical agitator mills. No complex and expensive conversion is necessary for this; simple subsequent installation or retrofitting can be carried out.

Depending on the separating device, other shapes than a cylindrical shape can also be expedient.

This solution can be used in particular for all vertical agitator mills with a sieve-like separating device.

List of reference signs

1

Packing

2

Grinding container

4th

Drainpipe

8th

Grinding room

9

Container wall

19th

Central longitudinal axis

22nd

Inner stator

23

Outer wall

30th

Grinding media separator

35

rotor

38

Tools

41

channel

42

Discharge base

H

Overflow height

H

Height of the grinding media separator

Claims (14)

Agitator mill for handling free-flowing grist, - With a grinding container (2) and a grinding chamber (8) which is delimited by a container wall (9) of the grinding container (2) and is at least partially filled with grinding media, and - With an agitator with a rotor (35) which is rotatable about a central longitudinal axis (19) which is arranged essentially vertically during operation, and - With an inner stator (22) which is arranged inside the rotor (35), and - A grinding stock discharge channel is formed between the rotor (35) and an outer wall (23) of the inner stator (22) through which the grinding stock is passed through a grinding media separating device (30) in the direction of a discharge pipe (4), with the grinding stock behind in the flow direction the grinding media separator (30) has a grinding stock discharge space, - characterized in that a device for setting a minimum level of the product is arranged in the grist removal space within the grist removal space. Agitator mill according to claim 1, wherein the grinding media separating device (30) is designed in the form of a substantially vertically arranged cylinder with a height H, the interior of which forms the grinding material discharge space and the minimum level in the grinding material discharge space is greater than or equal to 0.85 H. Agitator mill for handling free-flowing grist, - With a grinding container (2) and a grinding chamber (8) which is delimited by a container wall (9) of the grinding container (2) and is at least partially filled with grinding media, and - With an agitator with a rotor (35) which is rotatable about a central longitudinal axis (19) which is arranged essentially vertically during operation, and - With an inner stator (22) which is arranged inside the rotor (35), and - A grinding stock discharge channel is formed between the rotor (35) and an outer wall (23) of the inner stator (22) through which the grinding stock is passed through a grinding media separating device (30) in the direction of a discharge pipe (4), with the grinding stock behind in the flow direction the grinding media separator (30) has a grinding stock discharge space, - characterized in that a device for reducing the volume of the Mahlgutabführraums is arranged in the Mahlgutabführraums. Agitator mill according to claim 3, wherein the grinding media separating device (30) is designed in the form of a substantially vertically arranged cylinder with a height H, the interior of which forms the grinding material discharge space, and the device for reducing the volume of the grinding material discharge space is formed by a packing (1). Agitator mill according to claim 3 or 4, wherein the packing (1) closes product-tightly with a discharge base (42) of the agitator mill and has an overflow height h of the product in the vertical direction, the height H of the grinding body separating device (30) being greater than the overflow height h,
where h is greater than or equal to H 0.85. The agitator mill according to one of claims 3 to 5, wherein the filler body (1) is a substantially cylindrical hollow body. The agitator mill according to one of claims 3 to 6, wherein the device for reducing the volume of the grinding stock discharge space is made of plastic or metal or ceramic. The agitator mill according to one of claims 3 to 7, wherein the device for reducing the volume of the grinding stock discharge space is designed to be temperature-controlled. The agitator mill according to any one of claims 3 to 8, wherein the separating device (30) is a cylinder screen. Agitator mill according to one of Claims 3 to 9, the device for reducing the volume of the grinding stock discharge space being removable. Agitator mill according to one of Claims 3 to 10, the device for reducing the volume of the grinding stock discharge space reduces the volume of the grinding stock discharge space by at least 70%. Agitator mill according to one of Claims 3 to 11, tools (38) which protrude into the grinding chamber (8) are attached to the rotor (35) and optionally the container wall (9). Agitator mill according to one of Claims 3 to 12, with the device for setting a minimum level according to Claim 1. A method for operating and cleaning an agitator mill, with the use of a device for reducing the volume of the grinding stock discharge space of the agitator mill according to one of the preceding claims,
characterized in that, when the agitator mill is in operation, the flow rate of the grist through the grist discharge space is large enough to reduce product deposits in particular in the grist discharge space of the agitator mill.

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