Loosening ground pellets in stirred sand mills

Abstract

The invention provides a method for loosening grinding pellets, in particular compacts or fillers of grinding beads, in a grinding chamber of a stirred sand mill. For this purpose, a fluid is introduced in a time-defined manner into the grinding chamber of the stirred sand mill by means of a feed device provided for this purpose. After the grinding aggregate compact is dissolved, the supply of the fluid is stopped again. The invention further provides a corresponding stirring type mill and a feeding device for fluid.

Description

TECHNICAL FIELD

[0001] The present invention relates to a stirred bead mill provided with grinding beads, in particular to loosening or dissolving a compact of grinding beads present in the grinding chamber of a stirred bead mill. BACKGROUND

[0002] Stirred mills or stirred bead mills have a wide range of applications in the grinding and dispersing of solids in liquids. They are used, for example, for the production of adhesives, printing inks, cosmetics, pharmaceuticals, or also for the production of raw materials for battery slurry, in particular silicon. In such mills, a generally cylindrical grinding chamber is formed in the grinding vessel, which is delimited by the inner wall of the grinding chamber.

[0003] The grinding stock is fed into the grinding chamber through a feed channel and is ground together with auxiliary grinding beads or grinding beads such as ceramic beads by rotating the stirrer. Such stirred bead mills can have a rotor that rotates within the grinding chamber and are optionally equipped with stirrer means on the rotor and optionally also on the vessel wall. A stirred bead mill of this type can be arranged such that the central longitudinal axis of the grinding chamber extends in the vertical direction during operation. Such stirred bead mills with stirrer means on the rotor and possibly also on the vessel wall are also used with the central longitudinal axis of the grinding chamber arranged horizontally. Another type of stirred bead mill to which the present invention can be applied has a stirrer shaft arranged around a central longitudinal axis and rotatable around said axis, to which a plurality of grinding discs are attached. These are usually arranged such that the central longitudinal axis extends in the horizontal direction when in operation.

[0004] After processing, the grinding stock in the grinding chamber is removed through a product outlet.

[0005] When the grinding stock in the grinding chamber is removed after the grinding operation has been completed, the grinding beads remain in the grinding chamber when the stirrer is at rest. In this case, there is a risk that the grinding beads collect together (i.e. form a compact) in the locations in which they are retained under the influence of gravity when the mill is at rest. The grinding bead charge in the grinding chamber can then block the rotor and make it impossible to restart the rotor.

[0006] In the past, attempts have been made to remove small amounts of grinding beads with a piston device to eliminate such compacts. However, such processes are very complex and cannot be carried out by all types of mill. For example, a device for achieving this purpose is described in DE 2 051 003.

[0007] DE 2 230 766 A1 describes a method and a device for grinding solids contained in a liquid, wherein the liquid flows from a reservoir to a mill and back. The mill contains grinding means such as beads, wherein the grinding means are prevented from entering the line arranged between the mill and the reservoir by a sieve.

[0008] CN 216778978 U describes a vertical sand mill with a detachable inner cylinder, wherein a filter screen for holding grinding beads is arranged on the inner cylinder.

[0009] It is therefore the object of the present invention to provide a simple device for loosening or dissolving a compact of grinding granules in a stirred sand mill so that the rotor is no longer blocked and the mill can be started.

[0010] This object is achieved by the features of the independent claims. The dependent claims define preferred embodiments of the invention. SUMMARY

[0011] The invention provides a method for loosening a compact of grinding granules, in particular grinding beads, in the grinding chamber of a stirred sand mill. To this end, a fluid is introduced into the grinding chamber of the stirred sand mill in a time-limited manner by means of a feed device provided for this purpose. After the compact of grinding granules has dissolved, the supply of fluid is stopped again. The introduced fluid can remain in the grinding chamber and can be flushed away together with the product during a subsequent work. To this end, the fluid should be compatible with the product.

[0012] The introduction of the fluid, in particular of a fluid flow, makes it possible to bring the grinding granules out of their assumed position in the compact. By wetting and / or lubricating the outer surface of the grinding granules, the compact of grinding granules can be disturbed and thus loosened and at least partially dissolved.

[0013] The fluid can be a liquid such as an organic solvent or water, a gas such as nitrogen, air or oxygen, or a liquid / gas mixture. The fluid is preferably water.

[0014] The method according to the invention can be carried out while the stirred sand mill is in a stationary state. Once the fluid has been introduced and the compact of grinding granules has been loosened, the stirred sand mill can be started while the fluid is located in the grinding chamber.

[0015] The method can also be carried out while the stirred sand mill is stopped, i.e. when the rotational speed of the stirrer arranged in the grinding chamber is reduced. In this case, the fluid is introduced into the grinding chamber before it is stationary.

[0016] The method according to the invention can be carried out automatically, wherein the fluid is introduced into the grinding chamber in an automated manner before the stirred sand mill is started and / or stopped.

[0017] Preferably, the fluid flows through the grinding aggregate retaining device, in particular through the screen, as the fluid is introduced into the grinding chamber.

[0018] The pressure at which the fluid is introduced into the grinding chamber is preferably below the maximum pressure, for example below 3 bar.

[0019] The amount of fluid introduced is preferably at least 2% and at most 90% of the volume of the grinding chamber.

[0020] The invention also provides a stirred sand mill. The stirred sand mill generally has a grinding chamber arranged in a grinding vessel, a product inlet for introducing grinding stock into the grinding chamber, a product outlet for taking off ground grinding stock, a stirrer rotatably arranged in the grinding chamber and a plurality of grinding aggregates arranged in the grinding chamber. The stirred sand mill according to the invention also has a feed opening for introducing fluid into the grinding chamber and a feed device which can be connected to the feed opening and is configured to introduce fluid into the grinding chamber. Existing openings, for example openings for completely emptying the grinding chamber comprising grinding aggregates, can also be used as feed openings for fluid. The feed device for fluid is preferably arranged in the lower region of the grinding chamber.

[0021] The stirred sand mill can also have a control device for automatically introducing fluid into the grinding chamber before starting and / or stopping the stirrer.

[0022] The diameter of the grinding aggregates is preferably between 0.03 mm and 2.0 mm, preferably between 0.05 mm and 0.8 mm.

[0023] The feed device for fluid preferably has a grinding aggregate retaining device, in particular a screen.

[0024] The grinding aggregates should be at least 20% larger, preferably 30% to 50% larger, in diameter than the smallest dimension of the passages of the grinding aggregate retaining device. The grinding aggregate retaining device is preferably made of hardened steel, preferably of ceramic or hard metal.

[0025] In order to be able to retrofit existing stirred sand mills, the invention also provides a feed device for connecting to the grinding chamber of a stirred sand mill for introducing fluid into the grinding chamber. The feed device has a valve, a feed line connected to the valve and a grinding aggregate retaining device. BRIEF DESCRIPTION OF DRAWINGS

[0026] The invention is described in more detail below with reference to the drawings, in which:

[0027] Figure 1 The lower side of a stirred sand mill with fluid connection according to the invention is shown, and

[0028] Figure 2 The fluid connection to the screen in the feed opening is schematically shown. DETAILED DESCRIPTION

[0029] In Figure 1 The grinding vessel 10 of the stirred sand mill can be seen in Fig. 1. In the embodiment shown, the cylindrical grinding vessel 10 with an inner grinding chamber is arranged such that the central longitudinal axis is oriented vertically. An additional connection via which fluid can be introduced into the stirred sand mill and in particular into the grinding chamber of the stirred sand mill is indicated by the lower arrow.

[0030] Due to the effect of gravity, the grinding granules accumulate at the lower end of the vertically oriented stirred sand mill when the sand mill is in a stationary state. An opening is provided in the lower end surface 11 of the grinding vessel 10, which can serve as a feed opening for the fluid. A feed device 20 is arranged at the opening, by means of which the fluid can be introduced into the grinding chamber. In addition, Figure 1 A valve actuator 23 of the feed device 20 is shown, which makes it possible to open or close the valve 21 for supplying the fluid. The feed device 20 also has a tube 22 for guiding the fluid from a fluid reservoir (not shown) to the feed opening.

[0031] Fluids, for example liquids such as water or organic solvents, or gases such as nitrogen, air or oxygen, can be introduced into the grinding chamber of the stirred sand mill, preferably into the region in which the grinding granule compaction takes place, via the fluid inlet. This can be on the lower end surface 11 on the lower side of the grinding vessel 10, as shown in the figure. However, it is also possible to correspondingly connect to the side wall of the grinding chamber, but preferably even in the lower part of the grinding vessel 10, even if the stirred sand mill has a horizontally oriented central longitudinal axis.

[0032] By introducing the fluid, the grinding granules can be brought out of their assumed position. By additionally wetting or lubricating the grinding granule outer surface, the grinding granule compaction can be disturbed and thereby at least partially dissolved. The stirred sand mill can thus be started up and operated normally again. After the start, the introduced fluid preferably remains in the grinding chamber and is discharged from the grinding chamber together with the ground grinding stock during the subsequent work. The introduced fluid should therefore be compatible with the product to be ground, i.e. it should not contaminate or otherwise render the product to be ground unusable.

[0033] The grinding granule compaction can in particular occur when the machine is in a stationary state and there is no grinding stock in the grinding chamber. The method according to the application is therefore generally used after the stirred sand mill or rotor has been stationary, in particular before the machine is filled with grinding stock and restarted.

[0034] However, the method can also advantageously be used during the standstill of the stirred sand mill when the grinding stock has usually already been discharged. If the rotor speed is reduced before the standstill, the rotor can suddenly stop before the stirred sand mill is stopped due to poorly positioned grinding granules or compacted grinding granules. In order to counteract the compacting of the grinding granules also in this case, it has been found that the introduction of the fluid according to the method according to the application is useful during the reduction of the rotational speed to a certain rotational speed, for example 600 rpm. The method according to the application can also be used during a flushing operation of the grinding chamber while the rotor is running.

[0035] The fluid can be supplied by manually opening a valve. However, it is also possible to automatically supply the fluid by means of a control device upon starting or stopping the stirred mill. In this case, the fluid can be automatically injected during a start-up operation before starting the stirrer, and after the fluid has been supplied, the stirrer can be started with a predetermined delay. Likewise, the fluid can be automatically supplied with a predetermined rotational speed when the fluid supply is stopped.

[0036] When carrying out the method according to the application, the fluid is introduced in a constant or pulsating manner over a limited period of time. The pressure of the fluid to be introduced is of course below the maximum permissible pressure of the grinding chamber, usually at most about 3 bar. When the fluid is introduced, the amount of fluid introduced is limited and / or monitored. Usually, a small amount of fluid is already sufficient to dissolve the compacting. For example, 2% of the volume of the grinding chamber can already be sufficient. However, fluid amounts of up to about 90% of the volume of the grinding chamber can also be introduced.

[0037] In order to ensure that the grinding granules remain in the grinding chamber during the execution of the method according to the application, the feed opening for the fluid is provided with a grinding granule retention device, in particular with a sieve. The openings of the sieve should be smaller than the diameter of the grinding granules used. If, for example, the grinding granules have a diameter of 0.1 mm, the width of the slits of the sieve should be, for example, 0.03 mm to 0.05 mm. It is particularly preferred that the method according to the application can be used when smaller grinding granules are used, wherein the diameter of the grinding granules is between 0.03 mm and 2.0 mm, preferably between 0.05 mm and 0.8 mm. The sieve can be made of hardened steel or, preferably, also of ceramic, including from hard metal.

[0038] By way of example, Figure 2 The use of a sieve 25 on the fluid feed opening is shown. The sieve 25 is preferably arranged flush with the inner surface of the grinding chamber, in the shown embodiment on the base plate of the grinding container. This is the area where compacting of the grinding granules often occurs due to the action of gravity.

[0039] Fluid is introduced into the grinding chamber of the stirred sand mill via the feed line, usually a hose 22, through the feed valve 21 and through the sieve 25 or usually through an attrition bead retention system such as a sieve or a nozzle by means of an opening provided for this purpose. The openings provided in the grinding chamber according to the application, i.e. the fluid feed, the product inlet, the product outlet, the attrition bead filling, the emptying of the attrition beads into or out of the grinding chamber, can all be realized by different openings in the grinding chamber. However, it is also possible within the scope of the present application to use the fluid feed for completely emptying the grinding chamber and thus also removing the attrition beads in the grinding chamber by removing the sieve. It is even conceivable to use an existing feed or discharge opening in the grinding chamber for the method according to the application. If necessary, the feed device 20 must be connected to this existing opening, which has a feed line, a valve and an attrition body retention device, i.e. for example a sieve.

Claims

1. A method for loosening compacted material or filler of grinding particles in the grinding chamber of a stirred sand mill, characterized in that... Fluid is introduced into the grinding chamber of the stirred sand mill in a time-limited manner by means of a feeding device (20) designed for this purpose, and the fluid supply is stopped again after the grinding agglomerates have dissolved.

2. The method according to claim 1, wherein, By introducing the fluid, specifically through a fluid flow, the grinding agglomerates are carried out of their assumed positions in the compaction, and the grinding agglomerate compaction is loosened and at least partially dissolved by wetting and / or lubricating the outer surfaces of the grinding agglomerates.

3. The method according to claim 1 or 2, wherein, The fluid is a liquid such as an organic solvent or water, a gas such as nitrogen, air or oxygen, or a liquid / gas mixture, wherein the fluid is preferably water.

4. The method according to any one of the preceding claims, wherein, The stirred sand mill is stationary before the fluid is introduced and starts up after the fluid is introduced, while the fluid is located in the grinding chamber.

5. The method according to any one of the preceding claims, wherein, To stop the agitated sand mill, the rotational speed of the agitated mill arranged in the grinding chamber is reduced, and the fluid is introduced into the grinding chamber before it comes to a complete stop.

6. The method according to any one of the preceding claims, wherein, Before starting and / or stopping the agitated sand mill, the fluid is automatically introduced into the grinding chamber.

7. The method according to any one of the preceding claims, wherein, The fluid flows through the grinding pellet holding device (25) during its introduction into the grinding chamber, specifically through the screen.

8. The method according to any one of the preceding claims, wherein, The pressure at which the fluid is introduced into the grinding chamber is below the maximum pressure, for example, below 3 bar.

9. The method according to any one of the preceding claims, wherein, The amount of fluid introduced is at least 2% and at most 90% of the grinding chamber volume.

10. A stirred sand mill, wherein the stirred sand mill has the following features: The grinding chamber is arranged in the grinding container (10). The product inlet is used to introduce grinding materials into the grinding chamber. The product outlet is used to remove the grinding material after grinding. A stirrer, rotatably arranged in the grinding chamber, and Multiple grinding particles, said multiple grinding particles being arranged in the grinding chamber, characterized in that The stirred sand mill also has a feed inlet and a feeding device (20), the feed inlet preferably being arranged in the lower region of the grinding chamber for introducing fluid into the grinding chamber, and the feeding device being connectable to the feed inlet and configured to introduce the fluid into the grinding chamber.

11. The stirred sand mill according to claim 10, further comprising a control device for automatically introducing the fluid into the grinding chamber before starting and / or stopping the agitator.

12. The stirred sand mill according to claim 10 or 11, wherein, The diameter of the grinding particles is between 0.03 mm and 2.0 mm, preferably between 0.05 mm and 0.8 mm.

13. The stirred sand mill according to any one of claims 10 to 12, wherein, The feeding device for the fluid has a grinding agglomerate retaining device (25), specifically a screen, wherein the grinding agglomerate size is preferably at least 20% larger in diameter than the minimum size of the channel of the grinding agglomerate retaining device (25), and even more preferably 30% to 50% larger.

14. The stirred sand mill according to claim 13, wherein, The grinding agglomerate retaining device (25) is made of hardened steel, preferably of ceramic or hard metal.

15. A feeding device (20) for connecting to a grinding chamber (10) of a stirred sand mill to introduce fluid into the grinding chamber, the feeding device having a valve (21), a feed line (22) and a grinding pellet holding device (25), the feed line being connected to the valve (21).

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