EP0572610B1 - Process for dispersing, mixing or homogenising mixtures and device for implementing it - Google Patents

Abstract

In a process for dispersing, mixing or homogenising solid/liquid and/or liquid/liquid mixtures, the dispersion or emulsion to be homogenised is introduced into a rotating grinding chamber (5) at least partly filled with grinding bodies and bounded by at least two rotary wall components (2, 4). The dispersion or emulsion to the homogenised is taken through the grinding chamber (5) transversely to the axis of rotation (3) of the wall components (2, 4). In a device for implementing the process with a grinding chamber (5) in which there are grinding bodies, the grinding chamber (5) is bounded by at least two wall components (2, 4) which can be rotated and it has at least one inlet and/or outlet aperture (15, 16) on its sides facing and away from the axis of rotation (3).

Description

The invention relates to a process for the continuous dispersing, mixing or homogenizing of solid / liquid and / or liquid / liquid mixtures and to an apparatus for carrying out this process with a disk-shaped or annular space-shaped grinding chamber in which grinding media are arranged.

According to an older proposal according to the Austrian application A 2384/90, a device for mixing, homogenizing or converting at least two components was already known, in which separate mixing tools could be dispensed with. In contrast to known agitators which are immersed in a container, the aim of this older proposal was to set the material to be mixed itself in motion relative to one another, so that a strong relative movement of the material to be mixed with one another is formed in adjacent partial areas. The mixing zone formed in this way should lead to a largely homogeneous mixing in the area of the mixing zone. In order to vary the mixing result, it has also been proposed to pressurize the mixing zone by changing the volume of the rotating container, the use of such a compression pressure being particularly important with regard to the possibility of achieving desired chemical reactions of individual components with one another. Continuous operation was possible with the older proposal in that the mixed material could be drawn off in the axial direction of the container, that is to say in the direction of the axis of rotation, the partial area in which the most intensive mixing took place being open on the opposite end faces from opposite directions , cylindrical containers was limited.

The invention now aims to improve a device of the type mentioned at the outset such that the mixing zone can be substantially enlarged with small structural dimensions and furthermore the possibility is created of homogenization even when substances which are difficult to mix with one another, in particular with solid / liquid mixtures and liquid / liquid mixtures, to achieve a dispersion or an emulsion. At the same time, the method according to the invention is intended to provide the possibility of effectively counteracting the formation of lumps which may occur in the production of such dispersions and of reliably dividing the smallest size of agglomerations. With the method according to the invention, in addition to reliable mixing, wet grinding and intensive dispersion are also to be achieved if liquids of relatively high viscosity are used and, in conventional wet grinding processes, the separability of the grinding media from the liquid components is difficult due to the high viscosity. According to the invention, a reliable and simple separation of grinding media should thus succeed at the same time, despite high viscosity, even when grinding media with an extremely small diameter and extremely low density differences are used for the dispersion to be produced. The use of starting materials with a higher viscosity should also make it possible to process concentrates, as a result of which the throughput, for example in the production of dilutable dyes based on synthetic resin pigments, can be significantly reduced.

To achieve this object, the method according to the invention essentially consists in introducing the dispersion or emulsion to be homogenized into a rotating, disk-shaped or annular space-shaped grinding space, which is at least partially filled with grinding media and is separated by two separately rotatable wall elements which are axially opposed to one another by their inner sides is that the wall elements are driven so that a resulting centrifugal force to the radial The grinding media are separated within the grinding chamber and the dispersion or emulsion to be homogenized is moved or passed through the grinding chamber transversely to the axes of rotation of the wall elements against the direction of movement of the grinding media caused by centrifugal force. A mixing zone is formed between the rotating wall elements by introducing the dispersion or emulsion to be homogenized into a rotating, ring-shaped grinding chamber, which is at least partially filled with grinding media and delimited by two separately rotatable, axially opposite wall elements with their insides axially opposite one another. which overall ensures a relatively large partial area of intensive mixing with small dimensions. At the same time, the at least partial filling of the grinding chamber with grinding media ensures intensive wet grinding, with an intensive acceleration of the grinding media and mixing taking place at the interface between the rotating areas of the grinding chamber. Due to the rotation of the rotatable wall elements and thus the rotation of the grinding chamber, a centrifugal force is simultaneously exerted on the grinding media, which leads to the fact that the grinding media move against one another on a larger diameter of the grinding chamber with high pressure and therefore in this partial area of the grinding chamber a high compression pressure and so that an improved wet grinding result is achieved. Simultaneously with this directed movement of the grinding media in the direction of the centrifugal force, the separation of the grinding media from the emulsion or the dispersion produced is now also improved, so that, for example, the finished mix in a smaller diameter on the side of the grinding chamber opposite this compression can be easily removed without the need for conventional separation techniques, such as the use of filters or sieves, which tend to become blocked. The separation of the grinding media from the dispersion or the emulsion can thus be substantially improved by the process according to the invention, this improvement being among other things therein lies in the fact that the use of sieves or filters when removing the mixture can be dispensed with, for which purpose the process according to the invention is carried out in such a way that the dispersion or emulsion to be homogenized moves transversely to the axis of rotation (s) of the wall elements through the grinding chamber or is passed through.

In the case of wall elements rotating relative to one another, the partial area of intensive mixing between the rotating partial areas of the grinding chamber or mixing chamber is formed by an annular surface which is essentially normal to the axes of rotation. With a corresponding design of the rotating wall elements, the division plane and thus the zone of the most intensive mixing can also lie in a surface which corresponds to the lateral surface of a cone. The mixing or swirling depends on the relative speed that exists between adjacent areas of the mixing or grinding room. If the wall surfaces rotate in opposite directions, this relative speed and thus the dispersing action become particularly high, with a total of a resulting centrifugal force in the grinding chamber to separate the grinding media. The method can therefore advantageously be carried out in such a way that the mixing operation is carried out between wall elements rotating relative to one another at different speeds and / or directions of rotation.

The axes of rotation of the wall elements which can be rotated relative to one another can be different from one another and run essentially parallel to one another, as a result of which a certain eccentricity of the rotational movement in relation to the interface between the particles rotating relative to one another and thus particularly intensive mixing can be achieved.

If the axes of rotation are inclined to one another, a flexing effect can also be used to improve the mixing over the entire radial extent of the grinding chamber be achieved. When using wall elements with mutually inclined axes of rotation, the wall elements can be driven at the same speed and in the same direction of rotation, which means that, despite the slight relative movement between the disks or wall elements and the material to be ground, a total movement of the material to be ground - mixture of grinding media is produced with each revolution. This means that the energy input can take place optimally and there is no risk of local overheating, especially when processing highly viscous masses. The possibility of being able to drive both wall elements at the same speed and still achieve an optimal grinding / mixing effect also means a significant simplification of the overall structure and ultimately improves the centrifugal effect on all grinding media.

The process is preferably carried out in such a way that the mixture or grinding media / grinding material mixture is set in rotation at the same rotational speed as the two wall elements, and that the mixing material or the grinding media / grinding material mixture is at least once in each direction in the direction of the axis of rotation and once in Direction is moved away from the axis of rotation. Overall, this results in the fact that the relative movement between the grinding media / material to be ground and the driving disks or wall elements in the direction of the rotary movement is practically zero, and the exclusive mixing and grinding action becomes effective due to the displacement of the mixture in the radial direction. It is thus possible to set the contact pressure and separating effect solely as a function of the common speed of these disks.

To simplify the seal and to simplify the construction of a corresponding device, the axes of rotation can, however, also be arranged coaxially to one another without further ado. In addition, there is the possibility of creating an additional possibility of premixing under high shear stress even outside the grinding chamber delimited by the rotatable wall elements. For this purpose, the method according to the invention is advantageously carried out in such a way that that the dispersion or emulsion to be homogenized is subjected to a shear stress between rotating surfaces on the outside of the wall elements of the grinding chamber before it enters the grinding chamber, such a procedure using a structurally relatively simple device results in additional intensive mixing.

A good separation of the grinding media from the dispersed or homogenized mixture without complex separation technology can be achieved in that the dispersion or emulsion to be homogenized is conveyed through the grinding chamber counter to the direction of movement of the grinding media caused by the centrifugal force.

The material to be homogenized or dispersed can advantageously be fed in from the outside inwards in the radial direction, the method being able to be carried out continuously in a particularly simple manner in such a way that the homogenized mixture is drawn off via an axial channel. In order to set the appropriate pressure conditions and flow conditions, the outflow via the axial channel can be throttled accordingly. Overall, the possibility of freely selecting the rotational speeds and / or the direction of rotation of the wall elements rotating relative to one another results over a wide range, and the possibility of adjusting the respective flow rate and pressure conditions makes it adaptable to different starting materials, and homogenization and mixing also succeed of difficult to mix, highly viscous substances with simultaneous improvement of the homogenization and the fine distribution or dispersion. The procedure is preferably such that the grinding chamber is filled to a maximum of 75% by volume, preferably 60% by volume, with grinding media with an effective diameter of less than 0.5 mm, preferably less than 0.1 mm.

The device according to the invention for performing this method, which in particular takes up little space and With low constructional and system engineering effort, the adaptability to a wide variety of starting materials with improved homogenization and mixing is ensured, is advantageously designed so that the grinding chamber is delimited by two axially opposite wall elements with their insides, which are separately rotatably driven, and that the grinding chamber has at least one feed and / or one discharge opening on its sides facing and facing away from the axis (s) of rotation. The feed opening can be connected to the radially outer end wall of the grinding chamber, the discharge opening being able to open into an axial channel in a region close to the axis. Both of these openings can be formed in a particularly simple manner by slots extending over the circumference of the grinding chamber, the design advantageously being such that the slots are in a common division plane of the normal to the axis of rotation of the wall elements Grinding room. With such a design, there is a relatively large zone of intensive mixing with at the same time small dimensions in the area of the ring area defined between the rotating partial areas. Instead of forming a slot in the region near the axis as a discharge opening by means of corresponding axial extensions of the wall elements, the discharge opening can of course be formed directly by an axial channel formed in at least one wall element, it being possible for appropriate throttling means to be provided in this channel. The grinding chamber generally has a circular outer circumferential surface and is designed as a torus or annular space in the case of a slot-shaped opening in the region near the axis.

A further improvement in the adjustability of the pressure conditions and the intensity of the wet grinding can of course be achieved if the grinding media are subjected to a particularly close proximity to one another while moving in the direction of the centrifugal force, while simultaneously increasing the pressure forces which become effective towards one another. This is advantageously achieved through a constructive Design in which the grinding chamber delimited by the wall elements of the grinding chamber is tapered in cross-section in a cross-sectional plane containing at least one axis of rotation transversely to this axis of rotation. When the grinding media is moved into such a tapering cone in accordance with the centrifugal force, intensive mixing is ensured over the entire cross-section of the grinding chamber, even outside the area in which the mixing takes place, which improves the homogenization effect and the breakdown of the smallest agglomerates succeed.

The design is advantageously made such that the wall elements are formed by half-shells which are rotatably mounted about a common axis and are connected to separate drives, which results in a simple structure with simple storage. Advantageously, premixing is possible on the outside of the mixing chamber or grinding chamber using high shear forces in that the design is such that a wall element is connected in a rotationally fixed manner to a part that overlaps the second wall element to form a gap, and that the feed line into it Gap opens.

Intensive mixing, in which a shear stress can optionally be dispensed with, can be achieved with an embodiment of the device in which the axes of rotation of the wall elements are arranged inclined relative to one another and adjoin one another at an obtuse angle. If such a device is operated with the same speed and the same direction of rotation of the wall elements, in particular disks, the relative movement of the wall elements is reduced to a cyclical squeeze, which creates a flexing effect, which of course can also be superimposed on shear stress at interfaces when speed or Differences of direction of rotation are permitted.

For further adjustability and adaptability of the conditions to different mixtures, the design is preferably such that the angle between the axes of rotation of the wall elements is infinitely adjustable.

The invention is explained in more detail below on the basis of an exemplary embodiment schematically illustrated in the drawing. 1 shows a partial section through a first embodiment of a device according to the invention for carrying out the method according to the invention; and FIG. 2 shows a modified embodiment of a device according to the invention with wall elements with mutually inclined axes of rotation.

In Fig.1 only half of the rotationally symmetrical design of the device is shown in section, the entire device resulting from reflection on the common axis of the two wall elements delimiting the grinding chamber.

The device for dispersing, mixing or homogenizing solid / liquid or liquid / liquid mixtures consists of a housing, generally designated 1, in which a first wall element 2 in the form of a half-shell is rotatably mounted about an axis of rotation 3 by a drive (not shown in more detail) . The bowl-shaped wall element 2 defines, with a second, also rotatably mounted, bowl-shaped wall element 4, a grinding chamber 5 designed as an annular space, the grinding chamber being indicated by dashed lines in the second half of the drawing by 5 'to illustrate the symmetrical design. In the embodiment shown, the second wall element 4 is also driven to rotate about the axis 3 by a drive, not shown. Storage for the wall element 4 in the housing 1 is indicated by 6. With the first rotating wall element 2 is the outside of the second wall element 4 overlapping part 7 non-rotatably connected, as indicated by 8, the bearings for the first wall element 2 or the part 7 connected thereto are indicated by 9 and 10.

The two shell-shaped wall elements 2 and 4 delimiting the grinding chamber 5 rotate about the common axis 3 at different speeds and / or different directions of rotation. Via a feed line or a connection 11, the material to be mixed or the solid / liquid and / or liquid / liquid mixtures enters the gap 12 between the outer wall 13 of the second wall element 4 and the inner wall 14 of the part connected to the first wall element 2 7, wherein in this gap 12 a strong shear stress of the material introduced is caused by the elements 4 and 7 rotating at different speeds and / or different directions of rotation. The material then passes through a slot or a feed opening 15 into the grinding chamber or annular space 5, in which up to 75 vol.% Grinding media (not shown) with an effective diameter of less than 0.5 mm are arranged in order to disperse, Mixing or homogenizing the supplied materials to assist. Also in the grinding chamber 5, the supplied material is exposed to shear and mixing stresses in that the two wall elements 2 and 4 which delimit or define the grinding chamber are driven at different speeds and / or different directions of rotation, which results in a mixing surface which is essentially of a circular area is formed. The correspondingly mixed or homogenized material is drawn off via a gap 16 facing the axis of rotation 3 between the rotating wall elements and applied via an axial channel 17. The gaps 15 and 16, which define the feed and discharge opening for the material to be mixed or homogenized, lie in a common plane normal to the axis of rotation 3.

The grinding chamber 5 has a cross-section which tapers conically from the region of the discharge opening 16 close to the axis to the region of the supply opening 15 remote from the axis, so that a high grinding element density in the grinding chamber 5 is supported by the direction of movement of the grinding elements in the grinding chamber or annular space 5 in the region of the inlet caused by the centrifugal force is present. At the same time, the arrangement of the inlet and outlet openings in the region of the outlet opening 16 on filters or sieves or the like can be illustrated. to separate the grinding media, since the grinding media are effectively moved away from the axis 3 by the centrifugal force, so that even in the event that the passage cross section of the gap or the discharge opening 16 is larger than the particle size of the grinding media even at high Viscosity of the materials to be mixed prevents the grinding media from escaping due to the high rotational speeds and the stresses. Throttling devices (not shown in more detail) are provided in the axial channel 17 for regulating or controlling the flow in order to achieve a desired result.

In the event that the two wall elements 2 and 4 have mutually different, mutually parallel axes of rotation, there is an eccentric movement of one wall element relative to the other, so that in particular a corresponding narrowing and widening of the gap 12 between the outer surface of the wall element 4 and the inner surface of the rotating part 7 can be achieved.

In the event that the mixtures to be homogenized or dispersed have a greater specific weight than the grinding media, the function of the inlet and outlet openings 15 and 16 can be inverted if the parameters are appropriately selected during the mixing or homogenization.

In the embodiment according to FIG. 2, a shell-shaped wall element 2 is in turn about an axis of rotation 3 by a Drive not shown driven to a rotary motion. With the wall element 2, in turn, a part 7 overlapping the second wall element 4 is connected in a rotationally fixed manner, only the bearings 10 being indicated. In a departure from the embodiment according to FIG. 1, the second shell-shaped wall element has a rotation axis 18 which is different from the axis of rotation 3 of the first wall element 2 and which forms an obtuse angle with the axis of rotation 3. The inclined arrangement of the second wall element 4 relative to the first rotatable wall element 2 results in a grinding chamber 5, the cross-section of which, in turn, tapers from the central region to the regions remote from the axis, the inclined position of the wall element 4 relative to the wall element 2 results in a different cross-sectional area in different sections along the circumference. This makes it possible, when the shell-shaped wall elements 2 and 4 are driven in the same direction and at the same speed, to move the entire material to be homogenized together with the schematically indicated grinding balls 19 at the same time without any significant relative movement between the grinding bodies 19 and the disks 2 or 4 occurs. The mixing and homogenization takes place in this embodiment by a corresponding flexing effect, which is caused by the different cross-sectional areas, especially at the radially outer regions of the grinding chamber 5, by the inclined position of the wall element 4 relative to the wall element 2. A similar flexing effect as in the grinding chamber 5 results in the gap 12 between the outer surface 13 of the wall element 4 and the inner surface 14 of the part 7 which overlaps the wall element 4 and is connected to the first wall element in a rotationally fixed manner. Corresponding preprocessing thus also results in this embodiment before the material enters the grinding chamber 5 via a slot or gap 15, similar to the embodiment according to FIG. 1, the mixed material directly in the embodiment according to FIG the axial channel 17 is withdrawn. Due to the centrifugal force, the grinding media are in turn removed from the axes of rotation 3 or 18 distant regions of the grinding chamber 5 are moved, with the cross-sectional area tapering to a different extent in turn resulting in a particularly high load on the grinding bodies 19 as soon as the material to be mixed or homogenized enters the grinding chamber 5.

In this embodiment, using a whale effect, it follows that the mixing and grinding effect is practically exclusively due to the displacement of the mixture in the radial direction. Overall, it follows that there is no relative movement between the wall elements 2 or 4 and the material to be mixed and that the mixture is moved at least once in the direction of the axes of rotation 3 and 18 and away from them with each revolution of the wall elements.

For adaptability to different material to be mixed or homogenized, the angle between the axes of rotation 3 and 18 can be infinitely adjustable up to a maximum value, starting from an aligned position of the axes 3 and 18.

Claims (14)

1. A method for continuously dispersing, mixing and/or homogenizing solid/liquid and/or liquid/liquid mixtures, characterized in that the dispersion or emulsion to be homogenized is introduced into a rotating disc-shaped or annular grinding space (5) at least partially filled with grinding bodies (19) and delimited by two separately rotatable wall elements (2, 4) arranged in an axially opposed relationship by their inner faces, that the wall elements are driven in a manner to produce a centrifugal force for radially separating the grinding bodies within the grinding space and that the dispersion or emulsion to be homogenized is moved or passed through the grinding space (5) transversely to the axes of rotation (3, 18) of the wall elements (2, 4) in a direction opposite the direction of movement of the grinding bodies brought about by the centrifugal force.
2. A method according to claim 1, characterized in that the mixing stock or grinding body/grinding stock mixture is set in rotation at the same speed of rotation as the two wall elements (2, 4) and that the mixing stock or grinding body/grinding stock mixture at each revolution is moved at least once in the direction towards the axis of rotation (3, 18) and once in the direction away from said axis of rotation.
3. A method according to claim 1 or 2, characterized in that the dispersion or emulsion to be homogenized prior to entering the grinding space (5) is subjected to a shearing stress between rotating surfaces (13, 14) provided on the external sides of the wall elements (2, 4) of the grinding space (5).
4. A method according to claim 1, 2 or 3, characterized in that the homogenized mixture is drawn off through an axial channel (17).
5. A method according to any one of claims 1 to 4, characterized in that the grinding space (5) is filled with grinding bodies (19) of an effective diameter smaller than 0.5 mm, preferably smaller than 0.1 mm, by a maximum of 75 % by vol., preferably 60 % by vol.
6. A method according to any one of claims 1 to 5, characterized in that the mixing procedure is effected between wall elements (2, 4) rotating relative to each other at different speeds and/or in different directions of rotation.
7. An arrangement for carrying out the method according to any one of claims 1 to 6, comprising a disc-shaped or annular grinding space (5), in which grinding bodies (19) are arranged, characterized in that the grinding space (5) is delimited by two wall elements (2, 4) arranged in an axially opposed relationship by their inner faces and capable of being rotatably driven separately, and that the grinding space (5) includes at least one supply and/or one discharge opening (15, 16, 17) on its sides facing, and facing away from, the axis/axes of rotation (3, 18).
8. An arrangement according to claim 7, characterized in that the supply and discharge openings (15, 16) are formed by slits extending about the periphery of the grinding space (5).
9. An arrangement according to claim 8, characterized in that the slits (15, 16) are located in a common plane of partition of the grinding space (5) extending substantially normal to the axis/axes of rotation (3, 18) of the wall elements (2, 4).
10. An arrangement according to claim 7, 8 or 9, characterized in that the grinding space (5) delimited by the wall elements (2, 4) of the grinding space is configured to taper in terms of cross section in a cross sectional plane containing at least one axis of rotation (3, 18), transverse to this axis of rotation.
11. An arrangement according to any one of claims 7 to 10, characterized in that the wall elements (2, 4) are comprised of half-shells mounted so as to be rotatable about a common axis (3) and connected with separate drives.
12. An arrangement according to any one of claims 7 to 10, characterized in that the axes of rotation (3, 18) of the wall elements (2, 4) are arranged to be inclined relative to each other, following upon each other by enclosing an obtuse angle.
13. An arrangement according to any one of claims 7 to 10, characterized in that the angle between the axes of rotation (3, 18) of the wall elements (2, 4) is infinitely variable.
14. An arrangement according to any one of claims 7 to 13, characterized in that one wall element (2) is connected in a rotationally fast manner with a part (7) overlapping the second wall element (4) under the formation of a gap (12) and that the supply duct (11) runs into this gap (12).

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