AGITATOR BALL MILL

Abstract

An agitator ball mill comprising a grinding chamber having a cylindrical wall, and further having a rotatably mounted agitator shaft extending into the grinding chamber and on which at least one agitator element is arranged inside the grinding chamber. The mill further comprises an inlet for supplying to the grinding chamber material to be ground and grinding bodies, an outlet for removal of the ground material, and an induction heater for the material to be ground located in the grinding chamber, the induction heater comprising an inductor and a susceptor. The at least one agitator element comprises a susceptor material which forms the susceptor of the induction heater, wherein the inductor comprises at least one coil which is arranged outside the cylindrical wall of the grinding chamber and encompasses the grinding chamber, and wherein the cylindrical wall of the grinding chamber consists of an electrically and magnetically non-conductive material.

Claims

1. An agitator ball mill having: a grinding chamber which has a cylindrical wall; a rotatably mounted agitator shaft which extends into the grinding chamber and on which at least one agitator element is arranged inside the grinding chamber; an inlet configured to supply material to be ground and grinding bodies to the grinding chamber; an outlet configured to remove ground material; and an induction heater configured to heat the material to be ground, the induction heater comprising an inductor and a susceptor; wherein: the at least one agitator element comprises the susceptor, the inductor comprises at least one coil which is arranged outside the cylindrical wall of the grinding chamber and encompasses the grinding chamber; and the cylindrical wall of the grinding chamber consists of an electrically and magnetically non-conductive material.

2. The agitator ball mill of claim 1 wherein two or more agitator elements are arranged on the agitator shaft spaced apart from one another along the agitator shaft, and wherein the inductor comprises two or more coils which are arranged along the cylindrical wall of the grinding chamber in a manner such that the magnetic fields they generate each act upon only one of the agitator elements.

3. The agitator ball mill of claim 2 wherein the coils are designed to be separately controllable.

4. The agitator ball mill of claim 1 further comprising a high-frequency generator for supplying the coil or the coils with alternating current at an operating frequency of the high-frequency generator, wherein the operating frequency of the high-frequency generator is in the range of 1 kHz to 1 MHz.

5. The agitator ball mill of claim 2 further comprising a high-frequency generator for supplying the coil or the coils with alternating current at an operating frequency of the high-frequency generator, wherein the operating frequency of the high-frequency generator is in the range of 1 kHz to 1 MHz.

6. The agitator ball mill of claim 3 further comprising a high-frequency generator for supplying the coil or the coils with alternating current at an operating frequency of the high-frequency generator, wherein the operating frequency of the high-frequency generator is in the range of 1 kHz to 1 MHz.

7. The agitator ball mill of claim 4 wherein the induction heater has a natural frequency, and wherein the operating frequency of the high-frequency generator is at or close to the natural frequency of the induction heater.

8. The agitator ball mill of claim 5 wherein the induction heater has a natural frequency, and wherein the operating frequency of the high-frequency generator is at or close to the natural frequency of the induction heater.

9. The agitator ball mill of claim 6 wherein the induction heater has a natural frequency, and wherein the operating frequency of the high-frequency generator is at or close to the natural frequency of the induction heater.

10. The agitator ball mill of claim 1 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

11. The agitator ball mill of claim 2 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

12. The agitator ball mill of claim 3 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

13. The agitator ball mill of claim 4 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

14. The agitator ball mill of claim 5 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

15. The agitator ball mill of claim 6 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

16. The agitator ball mill of claim 7 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

17. The agitator ball mill of claim 8 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

18. The agitator ball mill of claim 9 wherein the cylindrical wall of the grinding chamber is encompassed by a cooling jacket through which a cooling medium can be conducted.

19. An agitator ball mill having: a grinding chamber which has a cylindrical wall; a rotatably mounted agitator shaft which extends into the grinding chamber and on which at least one agitator element is arranged inside the grinding chamber; an inlet configured to supply to the grinding chamber: material to be ground; and grinding bodies; an outlet configured to remove ground material; and an induction heater configured to heat the material to be ground, the induction heater comprising an inductor and a susceptor; wherein: the at least one agitator element comprises the susceptor, the inductor comprises at least one coil which is arranged outside the cylindrical wall of the grinding chamber and encompasses the grinding chamber; the cylindrical wall of the grinding chamber consists of an electrically and magnetically, non-conductive material; the at least one agitator element is two or more agitator elements arranged on the agitator shaft spaced apart from one another along the agitator shaft; and the at least one coil is two or more coils which are arranged along the cylindrical wall of the grinding chamber in a manner such that the magnetic fields they generate each act upon only one of the agitator elements.

20. An agitator ball mill having: a grinding chamber which has a cylindrical wall; a rotatably mounted agitator shaft which extends into the grinding chamber and on which at least one agitator element is arranged inside the grinding chamber; an inlet configured to supply to the grinding chamber; material to be ground; and grinding bodies; an outlet configured to remove ground material; and an induction heater configured to heat the material to be ground, the induction heater comprising an inductor and a susceptor; wherein: the cylindrical wall of the grinding chamber consists of an electrically and magnetically non-conductive material; the at least one agitator element: comprises the susceptor, and is two or more agitator elements arranged on the agitator shaft spaced apart from one another along the agitator shaft; and the inductor comprises at least one coil which: is arranged outside the cylindrical wall of the grinding chamber; encompasses the grinding chamber; and is two or more coils which are arranged along the cylindrical wall of the grinding chamber in a manner such that the magnetic fields they generate each act upon only one of the agitator elements; and the coils are configured to be separately controllable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Further advantageous aspects will become evident from the following description of illustrative embodiments of the agitator ball mill according to the invention with the aid of the drawing, in which:

[0020] FIG. 1 shows an axial section through a first illustrative embodiment of the agitator ball mill according to the invention, and

[0021] FIG. 2 shows an axial section through a second illustrative embodiment of the agitator ball mill according to the invention.

DETAILED DESCRIPTION

[0022] The following observations apply in respect of the description which follows: where, for the sake of clarity of the drawings, reference signs are included in a Figure but are not mentioned in the directly associated part of the description, reference should be made to the explanation of those reference signs in the preceding or subsequent parts of the description. Conversely, to avoid overcomplication of the drawings, reference symbols that are less relevant for immediate understanding are not included in all Figures. In that case, reference should be made to the other Figures.

[0023] As the sectional view of FIG. 1 shows, the agitator ball mill according to the invention comprises a cylindrical grinding chamber 1 which is bounded by a cylindrical wall 2 and by an inlet-side end wall 3 and an outlet-side end wall 4. Passing through the inlet-side end wall 3 there is an agitator shaft 5 which is rotatably mounted externally or in the end wall and on which, in the illustrative embodiment shown, three agitator elements 11, 12 and 13 are arranged spaced apart from one another axially, i.e. along (that is to say in the direction of the longitudinal axis) the agitator shaft inside the grinding chamber 1. In the illustrative embodiment shown, the agitator elements 11, 12 and 13 are configured as accelerators; they are joined to the agitator shaft 5 for conjoint rotation therewith and during operation are rotationally driven by the agitator shaft 5. In the inlet-side end wall 3 there is arranged an inlet 6 for supplying material to be ground and grinding bodies to the grinding chamber 1, and in the outlet-side end wall 4 there is provided an outlet 7 for removal of the ground material, which outlet is separated from the grinding chamber 1 by a separator screen 8 that holds back the grinding bodies. In the outlet-side end wall 4 there is an annular channel 9 which is open towards the interior of the grinding chamber 1. During operation, the agitator shaft 5 and thus the agitator elements 11, 12, 13 (here: the accelerators) joined thereto for conjoint rotation therewith are set in rotation by an external motor (not shown). The agitator elements 11, 12 and 13 can be paddle-wheel-like, as shown, or, for example, be in the form of simple agitator discs.

[0024] The grinding chamber 1 is encompassed by an outer cooling jacket 10 in such a way that between the cooling jacket 10 and the cylindrical wall 2 of the grinding chamber 1 there is formed an annular hollow space 15 through which a cooling medium can be conducted as required. The supply and discharge lines for the cooling medium are not shown for the sake of clarity.

[0025] In terms of its structure and mode of operation the agitator ball mill according to the invention thus far corresponds to the aforementioned art, as represented, for example, by EP 3 102 332 B1. The person skilled in the art therefore requires no further explanation in that regard.

[0026] To heat the material to be ground, which flows through the grinding chamber 1 from inlet 6 to outlet 7 when the agitator ball mill is in operation, the agitator ball mill is equipped with an induction heater comprising a coil 20 as inductor which, during operation of the agitator ball mill, is supplied with alternating current by a high-frequency generator G (shown only symbolically in the drawing). The induction heater, in addition to comprising the inductor (coil 20), also comprises a susceptor. The coil 20 is arranged outside the grinding chamber 1 in the hollow space 15 formed between the cooling jacket 10 and the cylindrical wall 2 of the grinding chamber. The coil 20 supplied with alternating current generates an alternating (electro)magnetic field which passes through the cylindrical wall 2 of the grinding chamber 1 into the interior of the grinding chamber, because the cylindrical wall 2 of the grinding chamber 1 consists of an electrically and magnetically non-conductive material. The alternating magnetic field acts upon the agitator elements 11, 12 and 13, which are here made from a suitable electrically conductive material, for example from chromium steel or nickel-based alloys, which is also suitable for the grinding process, and generates eddy currents therein which heat the agitator elements 11, 12 and 13. The heat generated in the agitator elements 11, 12 and 13 in that way is transmitted from the agitator elements 11, 12 and 13 to the material to be ground and heats that material.

[0027] In order for the induction heating to be able to function, the cylindrical wall 2 of the grinding chamber 1 consists of a material through which the magnetic field of the coil 20 is able to pass as far as possible without hindrance. The material of the cylindrical wall 2 of the grinding chamber 1 is therefore neither electrically nor magnetically conductive, as already mentioned. A suitable material for the cylindrical wall 2 of the grinding chamber 1 is, for example, a ceramic, for example silicon carbide. As likewise mentioned, in the illustrative embodiment shown the agitator elements 11, 12 and 13 as a whole consist of an electrically conductive susceptor material in which eddy currents can be induced. The agitator elements 11, 12 and 13 can, however, alternatively consist only partly of a susceptor material or comprise such a susceptor material, in which case, however, the remainder of the agitator element consists of a material having high thermal conductivity and must likewise be suitable for the grinding process. A magnetic shield 30, which encompasses the coil 20 externally and laterally, concentrates the magnetic field generated by the coil 20 inwards onto the agitator elements 11, 12 and 13. The agitator shaft 5 can consist of an electrically and magnetically non-conductive material, so that it is itself not heated by the magnetic field of the coil 20.

[0028] The illustrative embodiment of the agitator ball mill according to the invention shown in FIG. 2, likewise in axial section, differs from the illustrative embodiment of FIG. 1 solely in that instead of the single coil 20 extending over virtually the entire length of the grinding chamber 1 there are three axially shorter coils 21, 22 and 23 which are designed to be separately controllable and which are arranged along the grinding chamber in a manner such that they each radially encompass one of the agitator elements 11, 12 and 13. Here, the inductor is formed by the three coils 21, 22 and 23. Three magnetic shields 31, 32 and 33 concentrate the magnetic fields of the coils 21, 22 and 23 onto the agitator elements 11, 12 and 13 and shield the magnetic fields towards the outside. All other parts of the agitator ball mill are the same as in the illustrative embodiment of FIG. 1 and accordingly have the same reference signs.

[0029] The magnetic fields generated by the three coils 21, 22 and 23 each act upon only the agitator element 11 or 12 or 13 located radially opposite the respective coil. The division of the inductor into (here) three independent coils 21, 22 and 23 allows the material to be ground to be heated differently in different (axial) zones, which is advantageous for certain applications. For this reason, the coils 21, 22 and 23 are individually controllable, which can be effected either by means of three independent high-frequency generators or by means of a high-frequency generator having a plurality of outputs.

[0030] Through suitable control of the coil or coils it is possible to achieve zonal control of the temperature of the material to be ground. The control of the temperature can be additionally supported through cooling by means of a cooling medium which can be conducted through the hollow space 15.

[0031] The coil 20 or the coils 21, 22 and 23 are supplied by the high-frequency generator G shown only diagrammatically in the drawing. The operating frequency of the high-frequency generator G can be in the range of 1 kHz to 1 MHz.

[0032] The induction heater has a natural frequency which is determined by the coil or coils and the susceptors or agitator elements. Ideally, the operating frequency of the generator G for supplying the coil or coils with alternating current (which has that operating frequency) is as close as possible to or at the natural frequency of the induction heater. The optimum operating frequency can be determined empirically.

Embodiments

[0033] Embodiment 1. An agitator ball mill having a grinding chamber (1) which has a cylindrical wall (2), further having a rotatably mounted agitator shaft (5) which extends into the grinding chamber (1) and on which at least one agitator element (11, 12, 13) is arranged inside the grinding chamber (1), having an inlet (6) for supplying material to be ground and grinding bodies to the grinding chamber as well as an outlet (7) for removal of the ground material, and having an induction heater for the material to be ground located in the grinding chamber (1), the induction heater comprising an inductor and a susceptor, wherein the at least one agitator element (11, 12, 13) comprises the susceptor, wherein the inductor comprises at least one coil (20; 21, 22, 23) which is arranged outside the cylindrical wall (2) of the grinding chamber (1) and encompasses the grinding chamber (1), and wherein the cylindrical wall (2) of the grinding chamber (1) consists of an electrically and magnetically non-conductive material.

[0034] Embodiment 2. The agitator ball mill according to embodiment 1, wherein two or more agitator elements (11, 12, 13) are arranged on the agitator shaft (5) spaced apart from one another along the agitator shaft, and wherein the inductor comprises two or more coils (21, 22, 23) which are arranged along the cylindrical wall (2) of the grinding chamber (1) in a manner such that the magnetic fields they generate each act upon only one of the agitator elements (11, 12, 13).

[0035] Embodiment 3. The agitator ball mill according to embodiment 2, wherein the coils (21, 22, 23) are designed to be separately controllable.

[0036] Embodiment 4. The agitator ball mill according to any one of the preceding embodiments, which comprises a high-frequency generator (G) for supplying the coil (20) or the coils (21, 22, 23) with alternating current at an operating frequency of the high-frequency generator (G), wherein the operating frequency of the high-frequency generator is in the range of 1 kHz to 1 MHz.

[0037] Embodiment 5. The agitator ball mill according to embodiment 4, wherein the induction heater (20, 11, 12, 13; 21, 22, 23, 11, 12, 13) has a natural frequency, and wherein the operating frequency of the high-frequency generator (G) is at or close to the natural frequency of the induction heater.

[0038] Embodiment 6. The agitator ball mill according to any one of the preceding embodiments, wherein the cylindrical wall (2) of the grinding chamber (1) is encompassed by a cooling jacket (10) through which a cooling medium can be conducted.

[0039] The invention has been explained above with reference to illustrative embodiments, but is not intended to be limited to those illustrative embodiments; rather, the person skilled in the art will be able to conceive numerous modifications without departing from the teaching of the invention. For example, it is also possible for more or less than three agitator elements to be provided in the grinding chamber and the agitator elements can be configured as desired. In addition, it is also possible for the induction heater to comprise only two or more than three inductor coils. Furthermore, in the case of a plurality of coils, individual coils can also act upon two or more agitator elements simultaneously.

[0040] Thus, persons skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration rather than of limitation. The present invention is limited only by the claims that follow.