System arrangement and method for milling starting materials

Abstract

The present invention relates to a system arrangement (1) for grinding raw materials. Such a system arrangement (1) comprises a stirred ball mill (3) with a filling system (2) for raw materials to be ground and a deflector wheel classifier (4) coupled to the stirred ball mill (3). Both the filling system (2) and the deflector wheel classifier (4) are arranged substantially horizontally with respect to the longitudinal orientation of the stirred ball mill (3). Furthermore, a method for grinding raw materials is shown.

Description

TECHNICAL AREA OF INVENTION

[0001] The present invention relates to a system arrangement for grinding raw materials and an associated method. GENERAL STATE OF THE ART

[0002] The crushing or grinding of raw materials in order to subsequently use the processed raw materials for the production of products requires the use of machines.

[0003] In addition to the time required for the milling process, other resources besides energy are needed to achieve high-quality results, such as skilled personnel and work surfaces.

[0004] An example from the film manufacturing industry is the grinding of fillers, which are then used, for instance, in the production of water vapor-permeable films. Water vapor-permeable films are needed, for example, for diapers and other liquid-absorbing products in the personal hygiene sector or in the construction industry.

[0005] Water vapor permeable films can be used, for example, as breathable plastic films, and their use is conceivable not only in diapers but also in sanitary napkin products or packaging films.

[0006] Common fillers for the applications described above are generally based on forms of calcium carbonate with a particle size distribution of 4 - 6% < 0.4 µm, 50% to 80% < 2 µm and 98% < 4 µm.

[0007] Such a filler is added to a masterbatch of the plastic (PE / PP film) to ultimately produce the film. The aim is a steep particle size distribution with a low proportion of submicron particles below 0.4 µm. This low submicron content reduces viscosity in the extruder and minimizes the need for coating agents. Furthermore, the filler, with a particle size distribution of 4–6% < 0.4 µm, 50–80% < 2 µm, and 98% < 4 µm, improves the permeability of the plastic film. This allows gases, such as air, to flow through the film.

[0008] To improve and homogenize the filler during extrusion for masterbatch production, the filler, or the finished milled filler powder, is typically treated with stearic acid. This process is called coating.

[0009] Prior art already provides for the production of a semi-finished product, which is produced, for example, on roller mills, pendulum roller mills or impact mills.

[0010] Such a precursor can have a particle size distribution of < 75 µm with a low fines content of < 2 µm. This precursor is then fed into wet-operated stirred ball mills, with vertical filling being provided.

[0011] The concentration is set to a maximum value of 30–35 m-%. The stirred ball mill, for example, is operated in such a way that the particle size distribution described above is maintained.

[0012] For further use, this product must be dewatered, dried, coated, and then deagglomerated. In most cases, a further screening step is carried out to remove any hard agglomerates that may have formed. Afterward, this material must be coated again.

[0013] This process is complex and requires a great deal of energy in various forms. The specific process energy from pre-grinding, grinding, and drying ranges up to 1,000 kWh / t, depending on the type of calcium carbonate used (aragonite, limestone, marble, calcite, or similar). BRIEF SUMMARY OF THE INVENTION

[0014] Against this background, the present invention aims to produce a system arrangement with which an energy-efficient grinding process is possible.

[0015] This problem is solved by a system arrangement with the features of claim 1 and by a method with the features of claim 7.

[0016] Accordingly, a system arrangement for grinding raw materials is provided. Such a system arrangement comprises a stirred ball mill with a filling system for raw materials to be ground and a deflector wheel classifier coupled to the stirred ball mill.

[0017] Both the filling system and the deflector wheel classifier are arranged essentially horizontally with respect to the longitudinal orientation of the stirred ball mill. An essentially horizontal orientation allows for certain degrees of freedom, such that a slight offset from the longitudinal direction is considered acceptable for achieving a stable production process. For example, a deviation of up to 20° with respect to the longitudinal direction can be considered acceptable.

[0018] A deviation of up to 20°, for example in an interval of 5° to 20°, preferably 10° to 20°, preferably 15° to 20°, has the advantage that a particularly flexible system arrangement can be provided, since such an arrangement can be reliably combined with a large number of possible additional components. This is particularly advantageous for maintenance and can sometimes have a positive impact on a more favorable cost / benefit ratio in this area during the usage phase.

[0019] Furthermore, a corresponding process for grinding raw materials is provided. Such a process comprises the following steps: providing and operating a stirred ball mill with a filling system; providing and operating a deflector wheel classifier coupled to the stirred ball mill, wherein both the filling system and the deflector wheel classifier are arranged and operated essentially horizontally with respect to a longitudinal orientation of the stirred ball mill.

[0020] One of the underlying ideas of the invention is to ensure a uniform and continuous supply of both fresh raw materials and raw materials that have not yet been ground into the desired form to the presented system arrangement, in order to promote a particularly energy-efficient grinding process.

[0021] The system is designed to achieve a uniform feed rate through a largely horizontal arrangement of components such as the filling system and deflector wheel classifier, thus avoiding the need to push through large quantities of the feed material, as is common with vertically arranged systems. The feed materials to be milled can therefore be fed directly into the system with an average particle size of 4 mm, eliminating the need for pre-milling and, in particular, the associated energy consumption.

[0022] According to one embodiment of the system arrangement, the stirred ball mill has grinding media with a size of between 1 and 10 mm, preferably between 2 and 9 mm, preferably between 3 and 8 mm, preferably between 4 and 6 mm.

[0023] Depending on the desired state of the input materials, a desired grinding result can thus be achieved with low energy input.

[0024] According to a further development of the system arrangement, the coupling between the stirred ball mill and the deflector wheel classifier is designed to provide a closed grinding classifier circuit.

[0025] The material being ground, i.e., the feedstock, can be conveyed from the discharge of the stirred ball mill into a deflector wheel classifier. The bulk material is separated in the coupled deflector wheel classifier. Subsequently, the coarse material can be conveyed directly to the mill, for example, partially by gravity, and thus be completely ground in a closed grinding and classification cycle. A closed grinding and classification cycle is advantageous because it eliminates the need for additional energy-intensive intermediate steps such as complex transfer or further filling of the system with material being ground.

[0026] According to a further development of the system arrangement, the coupling between the stirred ball mill and the deflector wheel classifier is also designed to provide a pneumatically operated grinding classifier circuit.

[0027] The aforementioned advantages can therefore be achieved even more easily.

[0028] According to one embodiment of the system arrangement, the stirred ball mill is designed to be operable exclusively in a dry operating condition.

[0029] The specific energy required for this possible dry process is less than 200 kWh / t, which is significantly lower than the previous wet process. This is because subsequent dewatering and drying are no longer necessary.

[0030] According to a further development of the system arrangement, the system arrangement comprises means and is designed to continuously receive a filling quantity of raw material to be ground, depending on a withdrawal quantity of finished ground raw material.

[0031] In other words, the appropriate amount of material for the final product is continuously added to the mill in the form of fresh material, i.e., raw material to be freshly milled. A mill that is thus continuously optimally supplied can be operated particularly energy-efficiently, as the energy used is utilized in the best possible way.

[0032] According to another embodiment of the presented invention, the system arrangement is designed to produce finished ground starting material at least partially with a particle size distribution of 4 - 6 % < 0.6 µm, preferably < 0.4 µm, 50% - 80% < 3 µm, preferably < 2 µm, and 98 % < 5 µm, preferably < 4 µm.

[0033] Such a finely ground end product is particularly well-suited for use in the production of breathable plastic films, for example. Slight deviations are tolerable as long as a steep particle size distribution with a low proportion in the submicron range below 0.4 µm can be achieved.

[0034] The presented combination and orientation of the respective components of the system arrangement according to the invention particularly promotes the reliable and energy-efficient achievement of this result. In particular, the feed of the raw material to be ground into the actual grinding process, resulting from the essentially horizontal orientation, ensures uniform and energy-efficient processing.

[0035] According to one embodiment of the method according to the invention, the stirred ball mill is provided and operated with grinding media having a size of between 1 and 10 mm, preferably between 2 and 9 mm, preferably between 3 and 8 mm, preferably between 4 and 6 mm.

[0036] Depending on the desired state of the input materials, a desired grinding result can thus be achieved with low energy input.

[0037] According to a further development of the presented method, the stirred ball mill and the deflector wheel classifier are operated while maintaining a closed, pneumatic grinding and classification circuit, so that raw material that has not yet been fully ground is circulated until final grinding.

[0038] The material being ground, i.e., the feedstock, can be conveyed from the discharge of the stirred ball mill into a deflector wheel classifier. The bulk material is separated in the coupled deflector wheel classifier. Subsequently, the coarse material can be conveyed directly to the mill, for example, partially by gravity, and thus be completely ground in a closed grinding and classification cycle. A closed grinding and classification cycle is advantageous because it eliminates the need for additional energy-intensive intermediate steps such as complex transfer or further filling of the system with material being ground.

[0039] According to one embodiment of the method, the stirred ball mill is operated exclusively in a dry operating condition.

[0040] The specific energy required for this possible dry process is less than 200 kWh / t, which is significantly lower than the previous wet process. This is because subsequent dewatering and drying are no longer necessary. In contrast to the state of the art, which relies exclusively on a wet process, i.e., wet milling, the dry milling process presented here eliminates the need for subsequent drying of the milled material, resulting in a particularly energy-efficient process. A dry operating condition in a stirred ball mill is defined, in particular, by the fact that no liquids are added to promote the milling of mineral feedstocks.

[0041] According to a further embodiment of the method, a finished ground starting material is produced by means of the presented method according to the invention, at least partially with a particle size distribution of 4 - 6 % < 0.6 µm, preferably < 0.4 µm, 50% - 80% < 3 µm, preferably 2 µm, and 98 % < 5 µm, preferably 4 µm.

[0042] Such a finely ground raw material or finished product is particularly well-suited for use in the production of breathable plastic films, for example. Slight deviations are acceptable as long as a steep particle size distribution with a low proportion in the submicron range below 0.4 µm can be achieved.

[0043] The combinations and orientations of the respective components of the system arrangement described and to be taken into account in the method according to the invention particularly promote the reliable and energy-efficient achievement of this grinding result. In particular, the feed of the starting material to be ground into the actual grinding process, which results from the essentially horizontal orientation, ensures uniform and energy-efficient processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention is described in more detail with reference to exemplary embodiments shown in the accompanying drawings.

[0045] The accompanying drawings are included to facilitate a further understanding of this invention and are incorporated into and form part of this description. The drawings illustrate the embodiments of this invention and, together with the description, serve to explain the principles of the invention.

[0046] Other embodiments of this invention and many of the intended advantages of this invention are easily understood when they become more understandable by reference to the following detailed description.

[0047] The elements in the drawings are not necessarily drawn to the same scale. Identical reference symbols denote similar parts. Fig. 1 a schematic representation of a system arrangement for grinding raw materials according to an embodiment of the present invention; Fig. 2 a schematic flow diagram for a process for grinding raw materials according to an embodiment of the present invention.

[0048] In the figures, identical reference numerals denote identical or functionally similar components unless otherwise indicated. All directional terms, such as "top", "bottom", "left", "right", "above", "below", "horizontal", "vertical", "back", "front", and similar terms, are used for explanatory purposes only and are not intended to restrict the embodiments to the specific arrangements shown in the drawings. DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

[0049] Fig. 1 Figure 1 shows a schematic representation of a system arrangement 1 for grinding raw materials not shown in detail according to an embodiment of the present invention.

[0050] The raw materials to be ground, which can also be referred to as feed material, are introduced into a schematically depicted stirred ball mill 3 via a schematically represented filling system 2. The stirred ball mill 3 shown is a dry-operated stirred ball mill 3, which is horizontally oriented with respect to its longitudinal direction.

[0051] The stirred ball mill 3 is operated dry, wherein a grinding body not shown in detail in the stirred ball mill 3 can, for example, have a size of between 1 and 10 mm, preferably between 2 and 9 mm, preferably between 3 and 8 mm, preferably between 4 and 6 mm.

[0052] The filling system 2 is divided into a first section A1 and a second section A2 in Fig. 1 The filling system 2 is shown to be arranged essentially horizontally with respect to the longitudinal orientation of the stirred ball mill 3. In particular, the second section A2 is shown to be oriented essentially horizontally. Therefore, the raw materials to be ground, which are not shown in detail, are introduced into the stirred ball mill 3 essentially horizontally via the filling system 2.

[0053] A predominantly horizontal orientation allows for a certain degree of freedom, such that a slight offset from the longitudinal direction can be considered acceptable for a stable production process. For example, a deviation of up to 20° with respect to the longitudinal direction can be considered acceptable. A deviation of up to 20°, for instance within an interval of 5° to 20°, preferably 10° to 20°, or more preferably 15° to 20°, offers the advantage of enabling a particularly flexible system arrangement, as such an arrangement can be reliably combined with a variety of possible additional components. This is particularly advantageous for maintenance and can sometimes have a positive impact on the cost-benefit ratio in this area during the operational phase.

[0054] System arrangement 1 is further equipped with a deflector wheel classifier 4, which is shown coupled to the agitated ball mill 3 via a first feed line 5. The material being ground passes from the agitated ball mill 3 to the deflector wheel classifier 4 via this first feed line 5.

[0055] In this schematic two-dimensional drawing, the deflector wheel classifier 4 is positioned behind the stirred ball mill 3, essentially in the same plane. Therefore, the deflector wheel classifier 4 is arranged essentially horizontally with respect to the longitudinal orientation of the stirred ball mill 3.

[0056] In exemplary embodiments not shown in detail, it is conceivable that the deflector wheel classifier 4 is arranged, for example, essentially to the left of the stirred ball mill 3, with reference to the plane of the image.

[0057] Other arrangements, which essentially provide for an alignment of the deflector wheel classifier 4 in a plane with the stirred ball mill 3, are possible as long as a return of materials to be ground from the deflector wheel classifier 4 to the stirred ball mill 3 via the filling areas provided for this purpose of the stirred ball mill 3 is essentially horizontal with reference to a longitudinal alignment of the stirred ball mill 3.

[0058] A second feed line 6 leads from the deflector wheel classifier 4 back to the stirred ball mill 3. In the deflector wheel classifier 4, the finely ground feed material is separated and fed as finished filler material via a third feed line 7 to a filter system 8. The filter system 8 is not part of the system arrangement 1 and is included here only as an option. The finely ground feed material, now also referred to as fines, leaves the production process in filtered form via a fourth feed line 9.

[0059] The raw material that is not fully ground, which can also be referred to as coarse material, is fed back to the dry, horizontal stirred ball mill 3 via the second feed line 6 and ground again.

[0060] Therefore, the coupling between stirred ball mill 3 and deflector wheel classifier 4, established by means of the first feed line 5 and the second feed line 6, is designed to provide a closed grinding classifier circuit.

[0061] In particular, a feed section Z of the second feed line 6 is shown to be arranged essentially horizontally with respect to a longitudinal orientation of the stirred ball mill 3.

[0062] In this respect, the feed section Z of the second feed line 6 is shown parallel to the second section A2 of the filling system 2, with both being arranged essentially horizontally with respect to a longitudinal alignment of the stirred ball mill 3.

[0063] Fig. 2Figure 1 shows a schematic flowchart for a process M for grinding raw materials according to an embodiment of the present invention. In a first process step M1, a stirred ball mill 3 with a filling system 2 is provided and operated. In a second process step M2, a deflector wheel classifier 4 coupled to the stirred ball mill 3 is provided and operated, wherein both the filling system 2 and the deflector wheel classifier 4 are arranged and operated substantially horizontally with respect to a longitudinal orientation of the stirred ball mill 3. List of reference symbols

[0064] 1 System arrangement 2 Filling system 3 Stirred ball mill 4 Deflector wheel classifier 5 First feed line 6 Second feed line 7 Third feed line 8 Filter system 9 Fourth feed line A1 A2 First section Second section Z Feed section

Claims

1. System arrangement (1) for grinding raw materials comprising a stirred ball mill (3) with a filling system (2) for raw materials to be ground and a deflector wheel classifier (4) coupled to the stirred ball mill (3), wherein both the filling system (2) and the deflector wheel classifier (4) are arranged substantially horizontally with respect to a longitudinal orientation of the stirred ball mill (3).

2. System arrangement (1) according to claim 1, wherein grinding media in the stirred ball mill (3) have a size of between 1 and 10 mm, preferably between 2 and 9 mm, preferably between 3 and 8 mm, preferably between 4 and 6 mm.

3. System arrangement (1) according to claim 1 or claim 2, wherein the coupling between stirred ball mill (3) and deflector wheel classifier (4) is designed to provide a closed grinding classifier circuit.

4. System arrangement (1) according to claim 3, wherein the coupling between stirred ball mill (3) and deflector wheel classifier (4) is also designed to provide a pneumatically operated grinding classifier circuit.

5. System arrangement (1) according to one of the preceding claims, wherein the stirred ball mill (3) is designed to be operable exclusively in a dry operating condition.

6. System arrangement (1) according to one of the preceding claims, wherein the system arrangement (1) comprises means and is designed to continuously receive a filling quantity of starting material to be ground depending on a withdrawal quantity of finished ground starting material.

7. System arrangement (1) according to one of the preceding claims, wherein the system arrangement (1) is designed to produce finished ground starting material at least partially with a particle size distribution of 4 - 6 % < 0.6 µm, preferably < 0.4 µm, 50% - 80% < 3 µm, preferably < 2 µm, and 98 % < 5 µm, preferably < 4 µm.

8. A method for grinding feedstocks comprising the following steps: • providing and operating a stirred ball mill (3) with a filling system (2); • providing and operating a deflector wheel classifier (4) coupled to the stirred ball mill (3), wherein both the filling system (2) and the deflector wheel classifier (4) are arranged and operated substantially horizontally with respect to a longitudinal orientation of the stirred ball mill (3).

9. Method according to claim 8, wherein the stirred ball mill (3) is provided and operated with grinding media having a size of between 1 and 10 mm, preferably between 2 and 9 mm, preferably between 3 and 8 mm, preferably between 4 and 6 mm.

10. Method according to claim 8 or claim 9, wherein the stirred ball mill (3) and the deflector wheel classifier (4) are operated while maintaining a closed pneumatic grinding classifier circuit, so that raw material that has not yet been fully ground is circulated until final grinding.

11. Method according to one of claims 8 to 10, wherein the stirred ball mill (3) is operated exclusively in a dry operating condition.

12. Method according to any one of claims 8 to 11, wherein by means of the method finished ground starting material is produced at least partially with a particle size distribution of 4 - 6 % < 0.6 µm, preferably < 0.4 µm, 50% - 80% < 3 µm, preferably < 2 µm, and 98 % < 5 µm, preferably < 4 µm.

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