EP2327480A1 - Stirring ball mill - Google Patents

Abstract

The mill has a separating arrangement i.e. sedimentation centrifuge (300), for separating off multiple grinding bodies from a ground or dispersed material e.g. nanosuspension. A product outlet for the material that has been ground or dispersed and freed from the grinding bodies is provided. The ground or dispersed material passes through the separating arrangement into the outlet. The separating arrangement has an axial centrifuge entrance (332) or entrance in vicinity of an axis for the material intermixed with the grinding bodies.

Description

The present invention relates to a stirred ball mill according to the preamble of the independent claim.

Agitated ball mills are used, for example, for comminution or dispersion of solids in a liquid phase, in particular for products from nanotechnology and Feinstmahltechnologie, for example for dye suspensions, enamel paints, printing inks, ceramics, agrochemicals, filler suspensions, cosmetics, food, pharmaceuticals or microorganisms.

In such stirred ball mills, a material to be ground or to be dispersed in a liquid is introduced into the grinding chamber through an inlet and ground or dispersed therein by means of grinding bodies located in the grinding chamber. The material is thereby successively moved through the grinding chamber, whereupon the ground or dispersed material is discharged through a separating device which retains the grinding media, for example through a dynamic separating gap or through a slotted screen and then through an outlet. The basic operation of such stirred ball mills is known and, for example, in EP 0 627 262 or DE 2 215 790 described.

In stirred ball mills, different separation techniques are used to separate the ground or dispersed product from the grinding media. Examples include dynamic separation gaps, which consist of a rotor and a stator, and screens, such as slot screens. by virtue of In general, with higher screens, higher throughput is achievable with screens. In Feinstmahlkörpern (diameter 0.2 mm and smaller), however, very narrow sieve slots are necessary and the associated pressure loss is very high. Accordingly, the achievable throughputs are limited. In addition, regrind particles and grinding media can be deposited on the screen within a very short time, which can lead to blockage of the mill.

EP 0 771 591 and EP 1 468 739 describe a separation of the grinding media with Klassierrädern, where similar mechanisms act as in wind classifiers and wings are installed accordingly. The product-media mixture there must be promoted by a product pump against the centrifugal force of the Klassierrads. As the grinding media is thrown back into the grinding chamber by the sifter action, the product passes into the middle of the classifying wheel and to the product outlet. However, due to the built-in blades, the wheels simultaneously act as strong centrifugal pumps, which build up a correspondingly high pressure in the grinding chamber and thus make it difficult to set a long-term stable grinding process. In addition, the product pump must generate a correspondingly higher pressure in order to convey the millbase through the mill.

It is therefore an object of the invention to propose a stirred ball mill of the type mentioned, in which the abovementioned problems in the Mahlkörperabtrennung do not occur or at least greatly reduced. In particular, the separation of finest grinding media should be guaranteed without the above mentioned disadvantages.

This object is achieved according to the invention by a stirred ball mill, as characterized by the features of the independent patent claim. Advantageous embodiments of the inventive agitator ball mill are the subject of the dependent claims.

In particular, the invention comprises a stirred ball mill for fine grinding or dispersion of a material, a preferably rotationally symmetrical grinding chamber for receiving grinding bodies and for receiving the material to be ground or dispersed. The grinding chamber has an inlet for the material to be ground or to be dispersed and is equipped with a rotating drivable agitator with at least one stirring element for moving the grinding media and the material to be ground or dispersed. In the grinding chamber, a separating device for separating the grinding media from the ground or dispersed material is arranged. The grinding chamber further comprises a product outlet for the ground or dispersed and freed of grinding media Good, wherein the milled or dispersed material passes through the separator into the product outlet. The separator is designed as a rotatably drivable sedimentation centrifuge with an axial or at least close to the axis inlet for mixed with the grinding media Good.

Through the use of a sedimentation centrifuge for separating the grinding media can be dispensed with slot sieves and eliminates the associated problems. Compared with the Mahlkörperabtrennung with Klassierrädern there is the advantage that due to the axial or near-axis feed of the product-millbase mixture to be separated, the latter does not have to be promoted against an increased pressure which is produced by the acting as a centrifugal Klassierrad. The sedimentation centrifuge alone serves as a separator, without the above-mentioned pumping action. The agitator ball mill according to the invention can be set up and operated both horizontally and vertically (and basically also in a direction deviating from these two directions). It would even be conceivable cases in which the agitator and the centrifuge can be arranged at an angle relative to each other, in particular at a right angle.

In one embodiment, the sedimentation centrifuge has a substantially cup-shaped outer rotor and a coaxial inner rotor rotatably connected thereto, wherein there is a substantially annular centrifuge chamber between the outer rotor and the inner rotor.

In a further embodiment, the inner rotor is connected via a coaxial separator tube to a bottom part of the outer rotor, thereby providing the Separatorrohr at its periphery with passages for ground material. Advantageously, the sedimentation centrifuge is rotatably driven via a hollow shaft guided through an end wall of the grinding chamber, and the separator tube opens coaxially into the hollow shaft.

According to a further embodiment, the outer rotor is provided at its periphery with passage openings for separated grinding media.

The inner rotor may have a preferably conical surface at its end facing the inlet, which forms a ring channel with a radially inwardly directed annular flange of the outer rotor.

According to a further embodiment, the sedimentation centrifuge is designed as a plate separator. In this case, at least one preferably conical separator plate is arranged on the separator tube. Advantageously, a plurality of separator plates are preferably arranged equidistantly on the separator tube and the passage openings of the separator tube are arranged between and laterally next to the separator plates.

According to a further embodiment, the sedimentation centrifuge is designed as a decanter, wherein the inner rotor is substantially cylindrical and has a preferably conical end face.

According to a further embodiment, the agitator and the sedimentation centrifuge are designed to be driven independently of each other in a rotationally drivable manner. As a result, in particular the speed and the direction of rotation of the sedimentation centrifuge and the agitator are completely independent of each other adjustable. For example, agitator and sedimentation centrifuge can rotate either in the same direction or in the opposite direction and at the same or different rotational speed. Constructively, this can be achieved, for example, by the fact that the sedimentation centrifuge and the stirrer each have a separate drive shaft and each can be driven by a separate motor. This allows optimal adaptation to practical operating situations.

According to a further embodiment, the agitator and the sedimentation centrifuge are jointly designed to be rotatably drivable. This can be achieved constructively, for example, by the fact that the sedimentation centrifuge and the agitator have a common drive shaft and this can be driven by a motor which drives the common drive shaft.

According to a further embodiment, conveying means, in particular in the form of a conveying screw mounted on the outer rotor, are provided for conveying back grinding media which has passed out of the sedimentation centrifuge into the grinding chamber of the grinding chamber containing the agitator.

According to a further embodiment, the agitator ball mill on a deflecting member, which is at least partially disposed around the at least one stirring member around. This deflecting member serves to direct the material to be ground or to be dispersed into the part of the grinding chamber extending directly around the stirring element. According to one embodiment, the deflection element can be designed to be static, for example it can be arranged stationarily in the grinding chamber, for example it can be fixedly arranged on the inner wall of the grinding chamber. According to another embodiment, the deflection member may be formed dynamically, for example by an extension of the outer rotor of the sedimentation centrifuge. According to a further advantageous embodiment, an additional inlet for feeding additional product suspension or liquid phase of the product suspension and / or dispersing agent is provided in the grinding chamber in order to reduce the strong increase in viscosity, which can occur especially with nanosuspensions.

According to a further embodiment, the inlet or the additional inlet is arranged on the agitator-side end of the grinding chamber or on the centrifuge-side end of the grinding chamber.

Fig. 1

einen Axialschnitt durch ein erstes Ausführungsbeispiel der erfindungsgemässen Rührwerkskugelmühle,

Fig. 2

einen Axialschnitt durch ein zweites Ausführungsbeispiel der erfindungsgemässen Rührwerkskugelmühle,

Fig. 3

einen Axialschnitt durch ein drittes Ausführungsbeispiel der erfindungsgemässen Rührwerkskugelmühle, und

Fig. 4

einen Axialschnitt durch ein viertes Ausführungsbeispiel der erfindungsgemässen Rührwerkskugelmühle

In the following, the agitator ball mill according to the invention will be described in more detail with reference to the attached drawing with reference to four exemplary embodiments. Show it:

Fig. 1

an axial section through a first embodiment of the inventive agitator ball mill,

Fig. 2

an axial section through a second embodiment of the inventive agitator ball mill,

Fig. 3

an axial section through a third embodiment of the inventive agitator ball mill, and

Fig. 4

an axial section through a fourth embodiment of the inventive agitator ball mill

The following definition applies to the following description: If reference signs have been given in a figure for the purpose of clarity of drawing, but are not mentioned in the directly related part of the description, reference is made to their explanation in the preceding or following parts of the description. In addition, for those arrows in a figure which represent the flow of the ground material and / or the grinding media, the intensity of the hatching of the arrows is representative of the proportion of media contained in the stream: the more so an arrow is hatched (the darker an arrow appears), the more grinding media are contained in the stream. Thus, a stream represented by an unshaded (bright) arrow does not contain any media, while a stream represented by an arrow with a heavy hatch (dark arrow) contains a large number of media.

Furthermore, for the sake of simplicity, the material to be ground supplied to the agitator ball mill is referred to below as the ground material and the milled or suspended material produced by the grinding process and freed from grinding bodies is referred to as the product.

This in Fig. 1 illustrated first embodiment of the inventive agitator ball mill comprises a usually substantially rotationally symmetrical, for example, cylindrical grinding chamber 100, in which an agitator 200 and a separator in the form of a sedimentation centrifuge 300 are arranged.

The per se conventionally designed agitator 200 comprises an agitator 210, which sits on a stirrer shaft 220, which is performed by an end wall 101 of the grinding chamber 100 is rotationally driven by a drive motor, not shown. The agitator 200 can also be equipped in a manner known per se with a plurality of stirring elements, possibly also of different design (for example paddle wheels, discs, etc.).

The sedimentation centrifuge 300 sits on a hollow shaft 320, which is performed by the other end wall 102 of the grinding chamber 100 and is driven in rotation by a drive motor, also not shown. Preferably, but not necessarily, agitator 200 and sedimentation centrifuge 300 are coaxially aligned. In practical operation of the stirred ball mill, both the agitator 200 and the sedimentation centrifuge 300 can be horizontal or vertical.

In the embodiments of Fig. 1 . Fig. 3 and Fig. 4 the agitator 200 and the sedimentation centrifuge 300 are independently driven by a motor, in the embodiment of Fig. 2 is the agitator shaft 220 is not out through the end wall 101 to the outside, but rotatably or integrally connected to the sedimentation centrifuge 300, so that the agitator 200 rotates synchronously with the sedimentation centrifuge 300. A separate drive of agitator 200 and sedimentation centrifuge 300 with separate motors provides more degrees of freedom. Thus, for example, the sedimentation centrifuge can be operated at a higher speed than the stirrer in order to correspondingly accelerate the sedimentation of the grinding bodies. Agitator 200 and sedimentation centrifuge 300 can also be driven in opposite directions rotating, whereby a shearing action on the material to be ground is achieved, which can support the grinding.

The sedimentation centrifuge 300 comprises an outer rotor 330, substantially in the shape of a cylindrical cup, and an inner rotor 340 coaxially disposed therein, with a substantially annular centrifuge chamber 350 formed between the outer rotor 330 and the inner rotor 340.

The outer rotor 330 is equipped at its agitator-side end or shortly before this with a radially inwardly projecting annular flange 331 with an axial, a centrifuge inlet-forming opening 332. The peripheral wall of the outer rotor 330 is pierced at numerous points by passage openings 333 which are dimensioned sufficiently large so that grinding media can flow through them out of the centrifuge chamber 350 of the sedimentation centrifuge 300 into the surrounding space of the grinding chamber 100. In the embodiments of the FIGS. 1 and 3 the outer rotor 330 is provided with a coaxial tubular extension 335 which projects axially beyond the centrifuge inlet 332 into the grinding or stirring chamber of the grinding chamber 100 and encloses the agitator 200. The tubular extension 335 may also be provided with a deflection ring (not shown) or may act as such (deflection member). In the embodiment of Fig. 2 no such extension is shown.

The inner rotor 340 is fixedly connected on the hollow shaft side by means of a coaxial separator tube 360 to the bottom region 334 of the outer rotor 330. The separator tube 360 extends coaxially with the hollow shaft 320 and opens into it. In the wall of the separator tube 360 a plurality of passage openings 361 are provided, through which the product located in the sedimentation centrifuge 300 can flow into the separator tube 360 and from there into the hollow shaft 320. The hollow shaft 320 of the sedimentation centrifuge 300 thus forms a product outlet of the agitator ball mill.

In the embodiment of Fig. 1 in which the sedimentation centrifuge is configured as a decanter, the inner rotor 340 has a substantially cylindrical shape with a preferably conical tip facing the centrifuge inlet 332, whose end face (cone surface) is designated by 341. On the outer rotor 330, a screw conveyor 336 is arranged on its lateral surface, which extends into the extension 335 of the outer rotor 330.

In the embodiments of Fig. 2, Fig. 3 and Fig. 4 the inner rotor 340 is formed substantially doppelkonisch and compared to the inner rotor of the Fig. 1 axially much shorter. For the separator tube 360 is designed to be longer accordingly. The end face (conical surface) of the centrifuge inlet 332 facing the tip of the inner rotor 340 is denoted by 341. The bottom part 334 of the outer rotor 330 is tapered on its inside, with the cone angles of the bottom part 334 and the separator tube side conical part of the inner rotor 340 being substantially equal are. Between the conical bottom part 334 of the outer rotor 330 and the inner rotor 340, a plurality of conical separator plates 362 are arranged on the separator tube 360 coaxially substantially equidistantly or integrally formed with the separator tube 360. The passage openings 361 in the wall of the separator tube 360 are distributed over the length of the separator tube 360, so that between the separator plates 362 on the one hand and between the first and the last separator plate and the inner rotor 340 and the bottom part 334 of the outer rotor 330, respectively at least one passage opening 361 is located. In these embodiments, the sedimentation centrifuge is thus constructed essentially in the manner of a plate separator.

In the embodiment of Fig. 1 An inlet 110 for regrind is provided in the agitator-side end wall 101 of the grinding chamber 100 (at the agitator-side end). The ground or dispersed product is discharged through the hollow shaft 320 on the opposite side of the grinding chamber 100. In the embodiments of the FIGS. 2, 3 and 4 is the inlet 110 for the ground material in the hollow-shaft-side end wall 102 of the grinding chamber 100, the product is again discharged through the hollow shaft 320.

The general mode of operation of the stirred ball mill is as follows: The millbase is introduced through the inlet 110 into the grinding chamber 100 and ground and suspended in the agitator 200 by the grinding bodies present there. The mixture of ground Good and grinding media passes through the axial centrifuge inlet 332 into the interior 350 of the sedimentation centrifuge 300. There is a separation the grinding media by being thrown radially outward by the centrifugal action of the rotating sedimentation centriguge. The grinding media pass back into the grinding chamber through the passage openings 333 of the outer rotor 330 and are backwashed to the agitator 200. The freed from the grinding media product flows through the passage openings 361 in the separator tube 360 and from there into the hollow shaft 320 and is discharged through it.

In the embodiments of Fig. 2, Fig. 3 and Fig. 4 The ground material fed through the inlet 110 flows around the outer rotor 330 of the sedimentation centrifuge 300 on its way to the agitator 200. Means emanate from the outer rotor 330 through the passage openings 333 thereof. These grinding media are entrained by the inflowing ground material and conveyed back to the grinding chamber, in which the stirrer 200 and the majority of the grinding media are located.

After grinding, the product-millbase mixture passes through the inlet 332 of the sedimentation centrifuge 300 axially or axially close to this, in the space between the agitator 200 and the outer rotor 330. Due to the centrifugal force, the occurred product-product mixture is accelerated , The flow-through cross-sectional area of the centrifuge chamber 350 between the outer ends of the separator plate 362 and the inner wall of the outer rotor 330 advantageously expands outwardly, so that the flow can settle to achieve a laminar as possible flow at reduced speed and thus the sedimentation of the grinding media on the inner wall of the outer rotor 330 too facilitate, so that as few grinding media are entrained between the separator plate 362. Nevertheless, grinding bodies entrained between the separator plates 362 are thrown outwards and collect on the inner wall of the outer rotor 330 with the grinding bodies already accumulated there, in order then to pass through the passage openings 333 and be conveyed back to the stirring element with freshly fed grinding stock. The interspaces (plate channels) between the separator plates 362 are also advantageously designed so that the most laminar flow possible is achieved. The number of separator plates 362 may be selected according to the desired throughput. The freed from the grinding media product passes through the passage openings 361 in the separator 362 and from there via the hollow shaft 320 to the product outlet.

At the other end (centrifuge side end) of the grinding chamber 100, on the side of the hollow shaft 320, an additional inlet 111 may optionally be provided. Here, additional product suspension, or else the liquid phase of the product suspension and possibly also a dispersant, can be injected in order to reduce the strong increase in viscosity, which occurs especially with nanosuspensions.

In the embodiment of the Fig. 1 the sedimentation centrifuge 300 acts essentially as a decanter. The grinding bodies are thrown outwards by the inner rotor 340 and exit through the passage openings 333 in the outer rotor 330. The attached to the outer rotor 330 screw conveyor 336 promotes the well-worn grinding media back into the grinding chamber. Also in this embodiment may be provided at the other end of the grinding chamber 100, on the side of the hollow shaft 320, an additional inlet 111 can be injected through the additional product suspension or the liquid phase of the product suspension and / or a dispersant to the strong increase in viscosity, especially at Nanosuspensions occurs, decrease.

According to a detailed variant, the agitator 200 or its stirring element 210 may be surrounded by a deflecting ring, which influences the flow conditions in the grinding chamber. The deflection ring may be static or dynamic, in which case it would be attached to the outer rotor and would rotate with it. The agitators may be in various forms, e.g. be designed as paddle wheels, discs, or otherwise. In this case, either only one or more stirring elements can be provided on the agitator shaft.

This in Fig. 4 shown fourth embodiment of the inventive agitator ball mill has a certain similarity with the in Fig. 3 shown embodiment. However, in the embodiment according to Fig. 4 a stationary deflection ring 337 as a deflection firmly connected to the inner wall of the grinding chamber 100. The stationary deflection ring 337 is arranged around the stirring elements 210, which are here, for example, disc-shaped. Also, in the embodiment according to Fig. 4 the optional additional inlet port 111 is not shown, it may or may not be present. Regarding the operation of the embodiment according to Fig. 4 will be to the above description the operation of the embodiment according to Fig. 3 directed.

For the above-described embodiments of the agitator ball mill according to the invention, numerous further detail variants lying within the skill of the person skilled in the art are conceivable. In particular, e.g. the agitator and sedimentation centrifuge drive can be realized in various ways and the agitator and sedimentation centrifuge can be modified in various ways without departing from the scope of the invention. Thus, for example, impellers, disks or other suitable stirrers can be used as stirrers. The invention has been described with reference to the above embodiments of the agitator ball mill. However, the invention is not to be understood as being limited to these embodiments. Rather, numerous changes and variants of such a stirred ball mill are conceivable without departing from the technical teaching of the invention. For example, the return of the grinding media can also by other conveying members such. Paddle wheels done or the sedimentation centrifuge be designed as a tube centrifuge. Further, e.g. Also, the grinding chamber, in which the agitator is located, be partially delimited by a centrally open partition in the grinding chamber of the sedimentation centrifuge.

Claims (15)

Agitator ball mill for the fine grinding or dispersion of a material, with a preferably rotationally symmetric grinding chamber (100) for receiving grinding media and for receiving the material to be ground or dispersed, with an inlet (110) for the material to be ground or to be dispersed, with a rotating drivable agitator (200) with at least one stirring element (210) for moving the grinding bodies and the material to be ground or dispersed in the grinding chamber (100), with a separating device (300) for separating the grinding bodies from the ground or dispersed material and with a product outlet (320) for the milled or dispersed material removed from the grinding media, the milled or dispersed material passing through the separating device (300) into the product outlet (320), characterized in that the separating device is a rotating drivable sedimentation centrifuge (300) with an axial or at least close to the axis inlet (332) for with Well mixed with the grinding media. Agitator ball mill according to claim 1, characterized in that the sedimentation centrifuge (300) has a substantially cup-shaped outer rotor (330) and a rotatably connected thereto coaxial inner rotor (340), wherein between the outer rotor and the inner rotor is a substantially annular centrifuge chamber (350) is located. Agitator ball mill according to claim 2, characterized in that the inner rotor (340) via a coaxial separator tube (360) having a bottom part (334) of the outer Rotor (330) is connected. Agitator ball mill according to claim 3, characterized in that the separator tube (360) is provided at its periphery with passage openings (361) for the ground or dispersed Good. Agitator ball mill according to claim 4, characterized in that the sedimentation centrifuge (300) is rotatably drivable via a hollow shaft (320) guided through an end wall (102) of the grinding chamber (100), and in that the separator tube (360) is coaxial with the hollow shaft (320). empties. Agitator ball mill according to one of claims 2 to 5, characterized in that the outer rotor (330) is provided at its periphery with passage openings (333) for separated grinding media. Agitator ball mill according to one of claims 2 to 5, characterized in that the inner rotor (340) at its inlet (332) facing the end of a preferably conical end face (341) having a radially inwardly directed annular flange (331) of the outer rotor (330) forms an annular channel (342). Agitator ball mill according to one of the preceding claims, characterized in that the sedimentation centrifuge (300) is designed as a plate separator. Agitator ball mill according to claims 3 and 8, characterized in that on the separator tube (360) at least one preferably conical separator plate (362) is arranged. Agitator ball mill according to claim 9, characterized in that on the Separatorrohr (360) a plurality of Separatorteller (362) are preferably arranged gleichabständig, and that the passage openings (361) of the Separatorrohrs (360) between and laterally next to the Separatortellern (362) are arranged. Agitator ball mill according to one of the preceding claims, characterized in that the sedimentation centrifuge (300) is designed as a decanter, wherein the inner rotor (340) is substantially cylindrical and has a preferably conical end face (341). Agitator ball mill according to one of the preceding claims, characterized in that the agitator (200) and the sedimentation centrifuge (300) are designed either independently of each other or jointly rotatable drivable. Agitator ball mill according to one of the preceding claims, characterized in that conveying means (336) are provided for the return of sedimentation from the sedimentation centrifuge (300) grinding media in the mixing chamber containing the agitator (200) of the grinding chamber (100). Agitator ball mill according to one of the preceding claims, characterized in that it comprises a deflecting member, which is at least partially disposed around the at least one agitator, and that the deflecting member is formed either statically, for example, is arranged stationarily in the grinding chamber, or dynamically, for example by an extension (335) of the outer rotor of the sedimentation centrifuge. Agitator ball mill according to one of the preceding claims, characterized in that an additional inlet (111) is provided in the grinding chamber (100) for feeding in additional product suspension or liquid phase of the product suspension and / or dispersing agent.

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