GRINDING TANK OF A MIXED MILL AND MIXED MILL WITH SUCH A GRINDING TANK

Abstract

The present invention provides a grinding container of a stirred mill with a grinding chamber boundary and a cylindrical container shell having an axial extension and abutting the grinding chamber boundary, comprising an outer shell and an inner shell arranged concentrically with the outer shell, wherein the grinding chamber boundary has a circumferential groove-shaped recess in the area of ​​the inner shell and a first axial end of the inner shell can be lowered into the groove-shaped recess during temperature-induced axial length expansion, and a stirred mill with such a grinding container.

Description

[0001] The present invention relates to a grinding container of a stirred mill and a stirred mill with such a grinding container.

[0002] Stirred mills are used for the fine and ultrafine grinding of solids in liquids or dry materials. Conventional stirred mills consist of a grinding chamber in which a stirring shaft with grinding elements is rotatably mounted. These grinding elements can be designed as solid discs or impact elements and reduce the material to a fineness through impact, shear, and frictional forces generated by the rotation of the stirring shaft. These mills are used in numerous industries, such as the cement and mineral industries, pigment and dye production, the pharmaceutical industry, and food processing.

[0003] In high-temperature applications, such as in metallurgy or specialized chemical processes, the operating temperature of the mill can significantly exceed 100°C, making the thermal expansion of components a critical factor. This is particularly true for the grinding chamber, where temperature differences between the inner and outer shells can lead to high mechanical stresses. These stresses arise because the inner chamber expands more than the cooler outer chamber due to the process heat. This can result in critical mechanical stresses that compromise the integrity of the entire grinding chamber, especially at the connection between the grinding chamber and the chamber lid.To counteract this, conventional stirred mills used in high-temperature applications employ oversized flanges and bolted connections to absorb the stresses that occur. The assembly and disassembly of such mills proves to be time-consuming and often necessitates the use of specialized tools.

[0004] GB 1 559 201 A discloses a dispersing or grinding mill with a cylindrical, double-walled grinding chamber, the inner wall of which allows temperature-related expansion or contraction.

[0005] It is therefore an object of the present invention to create a possibility for effective strain compensation.

[0006] According to the invention, this problem is solved in each case by the subject matter of the independent claims.

[0007] According to a first aspect of the invention, a grinding container of a stirred mill is provided with a grinding chamber boundary and a cylindrical container shell having an axial extension and abutting the grinding chamber boundary, comprising an outer shell and an inner shell arranged concentrically with the outer shell, wherein the grinding chamber boundary has a circumferential groove-shaped recess in the area of ​​the inner shell and a first axial end of the inner shell can be lowered into the groove-shaped recess during temperature-induced axial length expansion.

[0008] According to a second aspect of the invention, a stirred mill with a grinding container according to the invention is provided.

[0009] One of the underlying ideas of the present invention is to avoid thermally induced linear expansion of the grinding container and the resulting stresses in the grinding container elements by means of a design modification of the grinding container or the grinding chamber boundary, for example, the container lid of the grinding container. Advantageously, the design according to the invention at least partially compensates for temperature-induced linear expansion of the inner shell in the axial direction in order to reduce or avoid critical mechanical stresses. The groove-shaped recess of the grinding chamber boundary ensures that the free axial end of the inner shell can expand into the recess in the grinding chamber boundary when temperature-induced expansion occurs.The groove-shaped recess allows the inner shell to expand into the recess until it reaches the bottom of the groove. This prevents premature contact between the inner shell and the grinding chamber boundary. This avoids stress on the grinding chamber boundary and the occurrence of critical mechanical stresses in the connection between the container shell and the grinding chamber boundary. Only when the container temperature causes further expansion of the inner shell, particularly beyond the normal extent, due to rising temperatures, do the resulting mechanical stresses on the grinding chamber boundary need to be absorbed and compensated by the connection between the grinding chamber boundary and the grinding container, i.e., via a grinding container flange and the connecting elements used therein, such as screw connections.However, since in this case the overall stresses that occur and need to be absorbed are reduced and less critical for the integrity of the grinding chamber, the connection between the chamber shell and the grinding chamber boundary, i.e., primarily the grinding chamber flange, can be made smaller. Furthermore, the size and number of fasteners can also be reduced. This has a beneficial effect on the complexity and weight of the entire agitator mill and reduces the effort required for assembly and disassembly.

[0010] Another idea underlying the invention is to be able to use agitator mills further developed according to the invention in applications with high operating temperatures without having to make adjustments in the number and dimensioning of connecting means, such as flange and screw connections.

[0011] Advantageous embodiments and further developments result from the dependent claims relating back to the independent claims and from the description with reference to the figures.

[0012] According to one embodiment, the axial depth of the groove-shaped recess is greater than the axial expansion of the inner shell within a defined operating temperature range of the stirred mill. This allows the thermally induced axial expansion of the inner shell to be accommodated within the recess, so that it encounters a fixed boundary only later. The inner shell thus remains freely movable over almost the entire defined operating temperature range, and jamming between the inner shell and the grinding chamber boundary, which is associated with mechanical stresses, is avoided or significantly reduced.Since, within the defined temperature range, no or only minimal forces act on the container shell and its grinding chamber boundaries due to the expansion of the inner shell, the stress on the screw connections used to join the individual elements of the grinding container is advantageously reduced, allowing them to be designed and dimensioned with less resistance overall. The connections between the individual elements of the grinding container therefore only need to be designed to withstand less critical mechanical stresses that can occur when the thermal expansion exceeds a normal level.

[0013] According to a further development, the radial width of the groove-shaped recess is larger than the wall thickness of the inner sleeve. This larger radial width ensures that the inner sleeve does not become radially jammed in the recess, thus advantageously avoiding thermally induced constraints and material stresses. Furthermore, the inner sleeve can expand axially without hindrance, without its movement being restricted by an overly tight fit.

[0014] According to one embodiment, a sealing element, particularly a compressible one, is provided within the groove-shaped recess. This sealing element ensures a seal during the longitudinal expansion of the inner shell and can be displaced by it without damage. Simultaneously, the sealing element prevents the ingress of ground material or process media into the groove-shaped recess, thus preventing contamination or clogging of the expansion chamber. Due to its compressible nature, the sealing element can also compensate for manufacturing tolerances and ensure a reliable seal even under varying operating conditions. The sealing element also protects the contact surfaces of the recess and the inner shell from abrasive wear caused by ingressing ground material.

[0015] According to a further development, the groove-shaped recess features a circumferential extension to accommodate the sealing element. Advantageously, this extension reliably holds the sealing element in the groove, preventing slippage or dislodgement during operation. The extension is also designed to fully accommodate the sealing element once the axial end of the inner sleeve rests against the base of the groove-shaped recess. This targeted accommodation of the sealing element enables improved sealing, as it can expand and adapt evenly without exerting excessive pressure on adjacent components.

[0016] According to a further development, the sealing element is designed as a sealing ring or as a sealing profile with a shape essentially corresponding to the groove-shaped recess. This specific shape advantageously achieves a precise fit between the sealing element and the recess or axial end of the inner sleeve, further improving the seal. The special profiling of the sealing element ensures a reliable seal against the ingress of ground material or process media into the expansion chamber and, depending on the specific profile shape, can compensate for thermal and mechanical movements without compromising its sealing effect.The sealing profile can have various configurations and can be designed, for example, as a lip profile with a flexible sealing lip, a bead profile with a circumferential bead that ensures uniform contact pressure and improved sealing under pressure, or as a compressible profile with internal chambering, without limiting the invention to these. In the latter embodiment, a hollow chamber located inside the profile allows elastic deformation in several directions, enabling the sealing element to compensate for both axial and radial movements.

[0017] According to one embodiment, a second axial end of the inner shell, opposite the first, is fixed in place within the grinding container. Fixing this second axial end ensures that the temperature-related expansion of the inner shell occurs only in a defined direction, thus preventing uncontrolled material stresses. Furthermore, the inner shell's freedom of movement in only one axial direction reduces the need for complex guide elements or additional sealing mechanisms at both axial ends of the grinding container. Of course, both ends of the grinding container can also be equipped with corresponding compensation arrangements, resulting in a floating mounting of the inner shell.

[0018] According to one embodiment, the inner jacket is arranged radially spaced from the outer jacket. This radial distance advantageously reduces direct heat conduction, resulting in slower heating of the outer jacket and better equalization of temperature differences between the inner and outer containers. The air space or an optional insulating intermediate layer between the two jackets acts as thermal insulation, protecting the mill's outer structure from excessive heating and preventing thermally induced stresses in the outer jacket. Furthermore, since the inner jacket can expand independently of the outer jacket, stresses caused by differing, including radial, thermal expansions between the two jackets are reduced.

[0019] According to a further development, a cooling system is provided between the outer and inner jackets. This cooling system advantageously enables targeted temperature regulation of the inner jacket, thereby preventing excessive heating or overheating and improving the thermal stability of the grinding process. Active cooling reduces the temperature difference between the inner and outer jackets, thus minimizing mechanical stresses and material loads.

[0020] According to a further development, the cooling system around the inner jacket features, in particular, spirally arranged coolant lines. The circumferential, especially spiral, arrangement of the coolant lines allows for large-area and uniform heat dissipation along the inner jacket and minimizes the temperature gradient. The spiral design maximizes the contact area between the cooling medium and the inner jacket, thereby improving heat dissipation and increasing cooling capacity. Uniform cooling, together with the inventive design of the grinding container, advantageously contributes to reducing or preventing thermally induced material stresses.

[0021] According to one embodiment, the outer shell can be fixed to the grinding chamber boundary via a flange connection, in particular by screwing it to the grinding chamber boundary. This advantageously creates a stable connection between the outer shell and the grinding chamber boundary. Due to the design of the container shell according to the invention, in particular by compensating for the thermal expansion of the inner shell, high stresses in the flange connection are avoided.

[0022] This eliminates the need for oversized flange or bolted connections to the grinding chamber boundary, particularly the container lid. Since there are no extreme forces due to thermal stresses to withstand, smaller diameter bolts with lower strength ratings can be used. This smaller size of the bolted connections simplifies disassembly / assembly and maintenance, and eliminates the need for special tools.

[0023] According to one embodiment, the container shell comprises at least two container sections. These sections are detachably connected at their opposing axial ends, for example, via screw flanges, clamps, or other connecting means. By transferring the thermal expansion between the container sections and providing targeted compensation at one axial end of the entire multi-section grinding container, thermal expansion of the entire container shell is enabled while simultaneously preventing uncontrolled or critical stresses. The multi-section design of the container shell advantageously allows for a modular and length-scalable construction. The targeted transfer of thermal expansion allows for simpler design of the section joints, thus eliminating the need for complex expansion joints or elaborate compensation mechanisms between the individual container sections.

[0024] In one embodiment, the grinding chamber boundary is designed as a grinding container lid. This lid design allows the grinding chamber to be easily opened, thus facilitating inspections, maintenance, and cleaning. Naturally, grinding chamber boundaries with corresponding compensation devices can also be provided at both ends of the grinding container.

[0025] According to a further development of the stirred mill, this mill is designed as a high-temperature mill. With the grinding chamber configuration according to the invention, the mill is particularly well-suited for applications with high operating temperatures exceeding 100°C, and in some cases up to 250°C and higher. Due to the targeted compensation for thermal expansion in the inner shell, critical mechanical stresses caused by thermal expansion are reduced within a defined operating temperature range for the respective mill, thereby preventing cracks or deformations and maintaining the structural integrity of the grinding chamber.

[0026] According to a further development of the stirred mill, a temperature control system is integrated into the vessel shell. This system enables precise control of the operating temperature, thereby maintaining a stable milling process and preventing undesirable material changes. Uniform temperature control minimizes temperature differences between the inner and outer shells. Any mechanical stresses that may still occur are reduced or eliminated by the vessel shell according to the invention.

[0027] The above embodiments and further developments can be combined with one another as appropriate. Further possible embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with respect to the exemplary embodiments, even if not explicitly mentioned. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

[0028] The present invention is explained in more detail below with reference to exemplary embodiments and the accompanying figures. The figures show: Fig. 1 a schematic representation of a section of a grinding container according to an embodiment of the invention; Fig. 2 a lateral sectional view of a grinding container section of a grinding container according to an embodiment of the invention; and Fig. 3 a lateral sectional view of a stirred mill according to an embodiment of the invention.

[0029] In the figures of the drawing, identical, functionally equivalent and similarly acting elements, features and components - unless otherwise stated - are each provided with the same reference symbols.

[0030] Although specific embodiments and further developments are presented and described herein, the person skilled in the art will prefer that a multitude of alternative and / or similar embodiments can replace the specific embodiments presented and described without departing from the scope of the present invention. This application is intended to generally cover all variations or modifications of the specific embodiments described herein.

[0031] The accompanying figures are intended to provide a further understanding of embodiments of the invention and serve, in conjunction with the description, to explain the principles and concepts of the invention. Other embodiments and many of the aforementioned advantages become apparent with regard to the drawings. The drawings are to be understood merely as schematic drawings, and the elements of the drawings are not necessarily shown to scale. Directional terminology such as "above," "below," "left," "right," "over," "below," "horizontal," "vertical," "front," "back," and similar terms are used for explanatory purposes only and are not intended to limit the generality of the invention to specific embodiments as shown in the figures.

[0032] Dashed lines in the figures of the drawings indicate that the connections between the components connecting the dashed lines do not necessarily have to have physical contact with each other, but can equally be wirelessly coupled to each other.

[0033] Fig. Figure 1 shows a schematic representation of a section of a grinding chamber 10 of a stirred mill 11 according to an embodiment of the invention. The depicted section shows the essential components for compensating for temperature-induced linear expansion, for example, in a high-temperature stirred mill. The grinding chamber 10 has a grinding chamber boundary 12, for example, in the form of a container lid, which closes off the grinding chamber 13 in the axial direction. The grinding chamber boundary 12 is connected to the container shell 34, which comprises an outer shell 14 and an inner shell 15, surrounds the grinding chamber 13, and defines the outer boundary of the grinding chamber 10. An inner shell 15 is arranged concentrically within the outer shell 14, which is in direct contact with the material being ground and is thus exposed to thermal stresses. The inner shell 15 may also have a wear-resistant coating.The flange-like connecting element 26, which positions the inner shell 15 and the outer shell 14 concentrically, is screwed to the grinding chamber flange 21. The grinding chamber boundary 12 has a circumferential groove-shaped recess 16 into which the first axial end 17a of the inner shell 15 can be lowered in axial direction A due to temperature-induced expansion. The groove-shaped recess 16 allows for compensation of thermal expansion of the inner shell 15 that occurs within a defined range of the operating temperature. During the grinding process in a high-temperature mill at temperatures above 100°C, the inner shell 15 expands more due to the process heat than the cooler outer shell 14.The groove-shaped recess 16 allows the first axial end 17a to extend into the recess 16 until it reaches the base 18 of the recess 16, without impacting the grinding chamber boundary 12 and thereby generating critical stresses in the connection between the container shell 34 and the grinding chamber boundary 12. If further longitudinal expansion occurs due to increasing container temperature, particularly beyond the defined operating temperature range, the resulting stresses are absorbed by the connection between the grinding chamber boundary 12 and the grinding container 10 or container shell 34, i.e., via the grinding container flange 21 and the screw connections 22 inserted therein. Since, however, the overall stresses to be absorbed are reduced in this case, the grinding container flange 21 can be made smaller. Furthermore, the size and number of screw connections 22 can also be reduced.The grinding chamber boundary 12, in the exemplary embodiment a container lid placed on the grinding container 10, thus provides an expansion space into which the inner shell 15 can penetrate to a certain extent when expanding in length, without contacting the grinding chamber boundary 12 and generating mechanical stresses.

[0034] The in Fig. The second axial end 19a of the inner shell 15 (not shown) is fixed in place within the grinding chamber 10. This ensures that the entire axial expansion is directed exclusively towards the groove-shaped recess 16 and compensated there up to a certain expansion limit. A sealing element 20 inserted into the groove-shaped recess 16 ensures a reliable seal between the grinding chamber boundary 12 and the first axial end 17a of the inner shell 15 before and during the axial expansion. The sealing element 20 prevents the ingress of grinding material or process media into the groove-shaped recess 16 and simultaneously protects the contact surfaces from abrasion and contamination.The sealing element 20 is elastic, for example, designed as a sealing ring or sealing profile, and can be compressed by the first axial end 17a of the inner shell 15 during its longitudinal expansion. During this expansion, the sealing element 20 can move into the extension 32 of the recess 16. As soon as the first axial end 17a of the inner shell reaches the base of the groove 18, the sealing element 20 is completely pressed into the extension and thus cannot be squeezed by the inner shell 15 and irreversibly damaged. The extension 32 not only serves as a space for the sealing element 20, which is acted upon by the inner shell 15, but also secures the sealing element 20 in position and prevents it from falling out. Before and during the longitudinal expansion of the inner shell 15 until it reaches the base of the groove 18, the groove-shaped recess 16 is sealed against the grinding chamber 13 by the sealing element 20.The grinding chamber flange 21, to which the chamber shell 34 is attached to the grinding chamber boundary 12, serves to securely fix the components. Due to the inventive design for accommodating the thermal expansion of the inner shell 15, reduced mechanical stresses occur in the grinding chamber flange 21, so that the screw connections 22 and the grinding chamber flange 21 itself can be dimensioned less robustly than in conventional agitator mills 11 without expansion compensation. The number of screw connections 22 on the circumference of the grinding chamber flange 21 can also be reduced.

[0035] Fig. Figure 2 shows a side sectional view of a grinding container section 23 of a grinding container 10 according to an embodiment of the invention. Embodiments are possible in which the grinding container 10 is formed from only one grinding container section 23 as shown here. Fig. Figure 2 shows a section of the construction of the grinding container 10, in particular the arrangement of the inner shell 15 within the outer shell 14 and the possibility of unilateral axial expansion of the inner shell 15 or its compensation. The inner shell 15 is arranged concentrically within the outer shell 14 and extends over the entire axial length L of the grinding container 10. At a second axial end 19a, the inner shell 15 is fixed in place, while the opposite first axial end 17a can be lowered into the circumferential groove-shaped recess 16 of the grinding chamber boundary 12. This allows for directed compensation of the axial expansion of the inner shell 15. The container shell 34 is screwed to the grinding chamber boundary 12 via the grinding container flange 21. Inside the grinding container 10, a stirring shaft 24 is rotatably mounted and is equipped with several stirring elements 25.The rotation of the agitator shaft 24 moves grinding media (not shown) placed in the grinding container 10 within the grinding chamber 13, resulting in fine or ultrafine grinding of the material by the applied impact, shear, and frictional forces. The outer shell 14 is spaced apart from the inner shell 15. In the resulting space 35, a cooling system 36 is provided in the exemplary embodiment. A cooling medium, pumped through the two nozzles 37, circulates around the container shell 34 in the space 35, dissipating the process heat generated.

[0036] Fig. Figure 3 shows a side sectional view of a stirred mill 11 according to an embodiment of the invention. Fig. Figure 3 shows the modular structure of the grinding container 10, i.e., its formation from two connected grinding container sections 23. The individual grinding container sections 23 each exhibit the characteristics associated with Fig. The structure described in section 2 is based on the one already described. Fig. The described configuration of the grinding container boundaries 12 for compensating the longitudinal expansion of the axial ends 17a, b of the respective grinding container sections 23 in groove-shaped recesses 16 is provided at both ends 27, 29 of the grinding container 10. The axial ends 19a, b, located centrally in the grinding container 10, are connected to each other via radially projecting connecting flanges 33 and fixed in position within the grinding container 10. In the agitator mill 11, an agitator shaft 24, equipped with several agitator elements 25, extends over the entire axial length L of the grinding container 10. The agitator elements 25 are arranged such that, through the rotation of the agitator shaft 24, they grind the material to be ground in the grinding container 10 with the aid of the grinding media (not shown) located in the grinding chamber 13. Fig. At the right end 27 of the agitator mill 11, an inlet housing 28 is arranged through which the material to be ground is fed into the grinding container 10. On the opposite side, in Fig. At the left end 29 is an outlet housing 30 through which the ground product leaves the grinding container 10. The agitator shaft 24 is supported by at least one further bearing and guided stably in the grinding container 10. The in Fig. The embodiment of the grinding container 10 shown in Figure 3 allows for a scalable design of the stirred mill 11 by adding further grinding container sections 23, while compensating for the temperature-related linear expansion of the entire inner shell 15 in the respective grinding container sections 23. In the embodiment shown in Figure 3, the grinding container 10 is designed to allow for a scalable design of the agitated mill 11 by adding further grinding container sections 23. Fig.In the arrangement of more than two grinding container sections 23 not shown, expansion compensation in the further grinding container sections 23 is achieved, for example, by providing groove-shaped recesses 16 in connecting flanges of the further grinding container sections 23.

[0037] In the preceding detailed description, various features have been summarized in one or more examples to improve the clarity of the presentation. However, it should be clear that the above description is merely illustrative and in no way limiting. It serves to cover all alternatives, modifications, and equivalents of the various features and embodiments. Many other examples will be immediately and directly clear to the person skilled in the art based on their technical knowledge, given the above description.

[0038] The exemplary embodiments were selected and described to best illustrate the principles underlying the invention and its practical applications. This enables those skilled in the art to optimally modify and utilize the invention and its various embodiments with regard to the intended purpose. In the claims and the description, the terms "including" and "comprising" are used as neutral language terms for the corresponding terms "comprehensive." Furthermore, the use of the terms "a," "a," and "an" is not intended to fundamentally exclude multiple features and components described in this way. Reference symbol list 10 grinding containers 11 Stirring mill 12 Grinding chamber limit 13 Meal room 14 Outer shell 15 inner mantle 16 Exclusion 17a, b first axial end 18 Groove 19a, b second axial end 20 sealing elements 21 Grinding container flange 22 screw connections 23 Grinding container section 24 Stirring shaft 25 stirring element 26 Connecting element 27 End 28 Inlet housings 29 End 30 outlet housings 31 warehouses 32 Extension 33 Connecting flange 34 Container jacket 35 space 36 Cooling system 37 stubs A axial direction L axial length

Claims

[1] Grinding chamber (10) of a stirred mill (11) with a grinding chamber boundary (12) and a cylindrical container shell (34) having an axial extension and with an outer shell (14) and an inner shell (15) arranged concentrically with the outer shell (14), wherein the grinding chamber boundary (12) has a circumferential groove-shaped recess (16) in the area of ​​the inner shell (15) and a first axial end (17a, b) of the inner shell (15) can be lowered into the groove-shaped recess (16) during temperature-induced axial expansion. [2] Grinding container (10) according to claim 1, wherein an axial depth of the groove-shaped recess (16) is greater than an axial longitudinal expansion of the inner shell (15) within a defined course of an operating temperature of the stirred mill (11). [3] Grinding container (10) according to claim 1 or 2, wherein a radial width of the groove-shaped recess (16) is greater than a wall thickness of the inner shell (15). [4] Grinding container (10) according to one of the preceding claims, wherein a sealing element (20) is provided, in particular a compressible one, inserted in the groove-shaped recess (16). [5] Grinding container (10) according to claim 4, wherein the groove-shaped recess (16) has a circumferential extension (32) for receiving the sealing element (20). [6] Grinding container (10) according to claim 4 or 5, wherein the sealing element (20) is designed as a sealing ring or as a sealing profile with a shape substantially corresponding to the groove-shaped recess (16). [7] Grinding container (10) according to one of the preceding claims, wherein a second axial end (19a, b) of the inner shell (15) opposite the first is fixed in position in the grinding container (10). [8] Grinding container (10) according to one of the preceding claims, wherein the inner shell (15) is arranged radially spaced from the outer shell (14). [9] Grinding container (10) according to one of the preceding claims, wherein a cooling system (36) is provided between the outer shell (14) and the inner shell (15). [10] Grinding container (10) according to claim 9, wherein the cooling system has coolant lines extending around the inner jacket (15), in particular in a spiral shape. [11] Grinding container (10) according to one of the preceding claims, wherein the container shell (34) can be fixed to the grinding chamber boundary (12), in particular via a flange connection (21), in particular screwed to the grinding chamber boundary (12). [12] Grinding container (10) according to one of the preceding claims, wherein the container shell (34) is formed from at least two container sections (23). [13] Grinding container (10) according to one of the preceding claims, wherein the grinding chamber boundary (12) is designed as a grinding container lid. [14] Stirred mill (11) with a grinding container (10) according to one of claims 1 to 13. [15] Stirred mill (11) according to claim 14, wherein the stirred mill (11) is designed as a high-temperature range mill. [16] Stirred mill (11) according to claim 14 or 15, wherein a temperature control system is provided integrated in the vessel shell (34).

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