Apparatus and method for rounding graphite flakes of a graphite material

Description

[0001] The present invention relates to a device and a method for rounding graphite flakes of a graphite material according to the features of the independent claims. State of the art

[0002] The invention relates to a method for producing graphite powder, in particular for rounding flake graphite. Graphite consists of carbon and occurs naturally, but can also be produced artificially. Artificial graphite is produced, for example, from lignite, hard coal or oil by coking, which produces crystals. However, the crystals produced in this way are only uniform if the production process takes place in many stages. This is correspondingly expensive. Natural graphite occurs as amorphous graphite, flake graphite or vein graphite; in particular, natural graphite forms grey to black hexagonal crystals that are usually arranged in layers one above the other. Amorphous graphite is similar to artificial graphite, i.e. the crystal size is small.

[0003] Graphite is characterized by high heat resistance and very good electrical and thermal conductivity. Graphite powder is used, for example, in the production of batteries, particularly as a negative electrode material. Publication DE 11 2013 005 116 T5 describes a carbon-containing material for lithium-air battery cathodes that exhibits higher capacity than conventional carbon-containing materials.

[0004] Publication DE 11 2016 000 490 T5 describes a method for producing a graphite powder for a negative electrode material for a lithium-ion secondary battery, which comprises a method in which a graphite precursor is pulverized and a method in which the mixture of the pulverized graphite precursor and an alkaline compound is subjected to a graphitization treatment by heating the mixture at 2800 to 3500°C.

[0005] Patent DE 1286386 B describes a beater or centrifugal impact mill with a classifier consisting of a cylindrical grinding chamber in which a centrifugal rotor and, coaxially to the centrifugal rotor, a centrifugal classifier consisting of a separately driven classifier rotor are arranged. A guide ring is arranged between the crushing rotor and the centrifugal classifier. This guide ring surrounds the centrifugal classifier at a radial distance and, together with the grinding chamber wall, forms an annular channel equipped with guide vanes.

[0006] The published patent application DE 19520325 A1 discloses a classifier mill with an interior space surrounded by a housing in which an air classifier and a grinding rotor with grinding tools are arranged.

[0007] The utility model describes a device for impacting cutting tools with graphite material. The cutting device consists of a gear ring and a rotating disc. When the material enters a gap between the rotating disc and the gear ring, the natural crystalline graphite flakes are processed by impact, cutting, and friction in the air stream, thereby forming spherical or spheroidal grains.

[0008] For certain applications, rounded graphite flakes are required, in particular graphite powder is required that has graphite particles of a certain particle size and preferably a homogeneous rounded shape, in particular without corners and edges. Description

[0009] The object of the invention is to provide a device and a method with which a graphite powder comprising rounded graphite particles, for example for use in the production of batteries, can be produced in a simple and cost-effective manner.

[0010] The above object is achieved by a device for rounding a graphite material, in particular graphite flakes, and a method for rounding a graphite material, which comprise the features in the independent patent claims. Further advantageous embodiments are described in the subclaims.

[0011] The device comprises a feed device for supplying the graphite material to be rounded, a plurality of rounding tools designed to rotate in a rotating manner, at least one guide device which has a plurality of guide elements and an inner guide ring and which guides the graphite material to the rounding tools and / or a separating device, and a separating device for separating fine material and ultrafine material that would interfere with subsequent processing steps. A plurality of rounding tools are arranged in a regular arrangement on a disk rotating about an axis of rotation and in a direction of rotation; in particular, the rounding tools are attached in a regular arrangement to the outer circumference of the rotating disk. Furthermore, the device has at least one product outlet via which the graphite material processed and, in particular, rounded within the device can be removed from the device.Furthermore, it is provided that a cover ring is arranged above the rounding tools. The cover ring preferably extends over all rounding tools arranged on the outer circumference of the disk. The cover ring leads to improved internal flow guidance of process air and thus also of the graphite material guided within the process air within the device. In particular, the cover ring enables advantageous circulation of the graphite material within the device. The cover ring prevents the coarse graphite material, in particular the graphite flakes and / or already rounded graphite particles, from being thrown upwards by a pressure wave formed on the rounding tools and being guided over the rounding tools by the process air without contact with the rounding tools.In particular, the cover ring enforces multiple operative contact between the coarse graphite material and the rounding tools by limiting the movement space of the process air that guides and / or transports the graphite material and increasing the number of contacts between the graphite material and at least one rounding tool. In particular, the cover ring prevents graphite material from circulating through the device without operative contact with at least one rounding tool. Furthermore, the device comprises a suction device for product material assigned to the product outlet, wherein a suction position of the suction device is formed directly on the inner guide ring and wherein the suction device extends radially to the inner guide ring.

[0012] The graphite material conveyed in the process air stream is imparted with a swirl by single or multiple active contact with at least one rounding tool of the device. The at least one guide device redirects the swirled graphite material in a largely vertically upward direction and feeds it to the separating device with virtually no swirl. This ensures optimal flow to the separating device, resulting in a high degree of separation accuracy.

[0013] The feed device for the graphite material to be processed is arranged above the rotating disk with the rounding tools. The rotating disk is preferably arranged within a cylindrical component, wherein the longitudinal axis of the cylindrical component and the axis of rotation of the rotating disk coincide. The inner surface of the cylindrical component represents, at least in part, the so-called impact surface for the graphite material. The graphite material introduced into the interior of the device via the feed device is grasped by the rounding tools, accelerated, and guided against the impact surface. The impact surface and the rounding tools are preferably designed such that the graphite material impacts the rounding tools at different angles and, in particular, multiple times before being guided to the impact surface.This allows a particularly advantageous deformation of the graphite flakes to be achieved, in particular the desired folding of the graphite flakes is achieved.

[0014] When the graphite material hits the rounding tools, the corners of the graphite flakes are folded and wrapped around the core of the respective graphite flake. Smaller graphite particles agglomerate into larger, particularly spherical, particles. Furthermore, the initial internal porosity is minimized during rounding. The graphite particles rounded in this way have a smaller surface area than the original graphite flakes. This results in a lower irreversible capacitance and also a long service life. The smooth surface of the rounded graphite particles prevents flaking or flaking. The powder with the rounded graphite particles has an increased tamped density and thus a high and, in particular, increased energy density.The powder with rounded graphite particles is particularly suitable for the production of lithium-ion batteries because the lithium ions have easier access to the graphite through the cavities formed between the rounded graphite particles. In particular, the lithium ions accumulate in the planes between the folded graphite flakes. The powder with rounded graphite particles is chemically cleaned and coated again after rounding and before use in battery production, etc.

[0015] The separation device can, for example, be designed as an air classifier with a classifier wheel in order to remove any abrasion in the form of fine material and / or ultrafine material that may arise during the rounding of the graphite flakes during the ongoing rounding process. The separation device is arranged above the disk with the rounding tools. The axis of rotation of the rotating disk with the rounding tools and the axis of rotation of the classifier wheel preferably coincide. In particular, the classifier wheel is arranged coaxially above the rotating disk with the rounding tools. A supply nozzle for process air is formed in the lower region of the device. The process air is supplied in particular from bottom to top and is guided to the rounding area, in particular the rounding tools, and via the guide apparatus to the separation device. In addition, there is an internal circulation of process air within the device.This circulation of process air brings the graphite material to the rounding tools multiple times. Furthermore, the process air entrains the fine and / or ultrafine material and removes it from the device via the separating device.

[0016] According to one embodiment, the rounding tools each comprise a side surface facing in the direction of the rotation axis, which is preferably convex in the direction of the rotation axis and / or has a radius in the direction of the rotation axis or is formed by a plurality of polygons. In particular, it can be provided that the rounding tools each have a longitudinal axis that coincides with a radial emanating from the axis of rotation of the disk. The side surface of the rounding tool facing the axis of rotation of the disk has a radius or is designed as a polygon. Preferably, the side surface is subdivided mirror-symmetrically by the radial. The design of the side surface facing the axis of rotation of the disk in a convex shape, as a radius or as a polygon with a plurality of partial regions arranged at an angle to one another leads to gentle stress on the graphite material.In particular, the selected shape of the rounding tools increases the probability that the graphite material will impact at a 90-degree angle, which is advantageous for the folding process. Thus, every active contact between the graphite material and a rounding tool preferably triggers a folding process. This folds the graphite material in the desired manner and, in particular, prevents it from being crushed, since there is always a central contact between the surface of the rounding tools and the graphite material.

[0017] According to one embodiment, a distance between adjacent rounding tools is between 0.5 times a width of the rounding tools and five times the width of the rounding tools. The width of the rounding tools is determined orthogonally to the radial on which the respective rounding tool is arranged. In particular, this is a radial starting from the axis of rotation of the disk on which the rounding tools are arranged. In contrast, a length of the rounding tools is determined on the radial starting from the axis of rotation of the disk. Preferably, the distance is less than three times the width of the rounding tools, particularly preferably less than 1.5 times the width of the rounding tools.

[0018] The number of rounding tools is preferably between 15 and 35 rounding tools per m circumference of the rotating disk on which the rounding tools are arranged.

[0019] According to the invention, the guide apparatus comprises a plurality of guide elements and an inner guide ring. In particular, the guide elements are arranged on at least one guide ring. In this case, it can be provided that the number of guide elements is fewer than the number of rounding tools. Alternatively, the number of guide elements can correspond to the number of rounding tools or the number of guide elements can be higher than the number of rounding tools. The graphite material fed via the feed device strikes the guide ring and is guided past the classifier wheel, so that any fine material and / or ultrafine material already present is separated from the device during the ongoing process. The graphite material then strikes the rotating disk with the rounding tools, which generate the energy for the rounding.The graphite material is captured, accelerated and thrown against the impact surface, causing the graphite material to fold and therefore become rounded.

[0020] The graphite material is preferably treated in the device for a defined time, during which it comes into active contact with the rotating rounding tools several times and is shaped accordingly. The time is in particular dimensioned such that it can be assumed that after the time has elapsed, the graphite material largely consists only of rounded graphite particles, which can advantageously be used for the production of batteries. After the rounding process is completed, in particular after a predefined processing time has elapsed, the rounded graphite particles are removed from the device via a product outlet; for example, the product is suctioned out of the device. The product is suctioned off directly at the inner guide ring of the guide device.This ensures that only product that has previously passed the classifier wheel, removing the fines and / or ultrafines, is removed from the device.

[0021] The guide apparatus comprising the guide elements and the guide ring is arranged above the rotating disk with the rounding tools. In particular, the guide apparatus is arranged statically within the device. According to one embodiment, the guide elements of the guide apparatus are designed as guide plates which are arranged on the guide ring. The guide plates are arranged and / or formed in regions in a plane perpendicular to the rotating disk and to a tangent of the rotating disk above the rounding tools. In particular, the guide plates extend essentially perpendicularly radially to the axis of rotation of the rotating disk with the rounding tools. Preferably, the lower region of the guide plates is bent counter to the direction of rotation of the rotating disk, so that an obtuse angle is formed between the bent region and the vertical region of the guide plate.The bent section ensures optimized, impact-free entry of the graphite particles into the vertical section of the guide device, which includes the guide elements. In particular, the bent section of the guide element supports the prescribed redirection of the swirling fine and / or ultrafine material in a direction perpendicular to the rotating disc. The air flow within the device first guides the supplied graphite material past the separator wheel, impacts the rotating disc, and is then directed to the rounding tools and the impact surface.

[0022] According to one embodiment, the addition of graphite material is regulated via a control device of the device. The control device controls, for example, the drive of the rotating disk with the rounding tools and / or the drive of the cutting device and / or other machine components of the device; in particular, the control device controls the respective speed of the rotating disk and / or the cutting device. For example, the control device can regulate the addition of graphite material based on a so-called cut-off value. When the running device is filled with graphite material, the current consumption of the drives increases. The control device contains information on at least one cut-off value, in particular information on current consumption values of the drives. When a defined cut-off value or both defined cut-off values are reached, the supply of further graphite material is stopped.For example, the feed device comprises a valve which is controlled by the control device when the cut-off value is reached and is closed based on the control signal so that no further graphite material enters the device.

[0023] During the course of the rounding process, the current consumption values can fall again so that the measured values can provide information about the progress of the rounding process. In particular, according to one embodiment it can be provided that if a second defined current consumption value, which is also referred to as the second switch-off value, is not reached, the dosing and / or material feeding can be started again. The drives of the rotating disk and / or cutting device are not switched off during the entire process as long as there is still graphite material in the device. Alternatively it can be provided that after complete filling, i.e. after the first switch-off value has been reached, the device is operated for a defined time, which was determined empirically in advance, for example, and after which the rounding of all graphite flakes is reliably completed.Controlling the supply of graphite material above the cut-off value ensures that the device is not overfilled and, in particular, that the device is reproducibly filled in the same way during each production cycle.

[0024] The product outlet, through which the rounded graphite particles are removed from the device after the rounding process has been completed, comprises - as already described above - a suitable suction device for the product material. The suction position of the suction device is formed directly on an inner guide ring of the guide device, and the product outlet extends in particular radially to the inner guide ring. The suction device (also referred to as the suction unit) generates a negative pressure. For product removal, the suction unit is opened, and the extracted air is discharged into a separation device, for example a cyclone with a filter. The product, comprising the rounded graphite particles, is separated from the extracted air.In conjunction with this volume flow, the product is pneumatically conveyed out of the process chamber, and the product concentration in the process chamber of the device decreases rapidly until the device is completely emptied. During the product removal process, the removal of fine and / or ultrafine material via the separating device and the stressing of the graphite particles by the rounding tools arranged on the rotating disk continue to be active.

[0025] According to the invention, the suction unit has a suction position directly on the inner guide ring of the guide apparatus. The product is removed by the suction unit, in particular, radially to the inner guide ring. During the rounding of the graphite material, the suction unit is closed, for example, by a movable cylinder extending radially to the inner guide ring. To remove the rounded graphite material, the suction unit is opened by moving the movable cylinder, and the product-air mixture comprising the rounded graphite particles is sucked into the suction unit.

[0026] To further optimize the process conditions, the speed at which the rotating disk, and thus the rounding tools, are moved can be varied during operation. For example, a low rotation speed can be selected initially, which is then increased to a maximum rotation speed during operation. Alternatively, it can also be advantageous for certain processes to start at a high speed and then reduce it during operation. The device is preferably operated with a maximum rotation speed of the rotating disk between 60 meters per second and 120 meters per second (relative to the circumference of the disk).

[0027] The device and method according to the invention allow for the simple and cost-effective production of rounded graphite particles optimized for battery production. Specifically, the graphite flakes are rounded by folding the corners of the graphite flakes and wrapping them around the core of the graphite flakes. This allows smaller graphite particles to agglomerate into larger spherical or sphere-like particles. Furthermore, the rounding process minimizes the internal porosity of the graphite particles, which is also advantageous for battery production.

[0028] The device according to the invention is characterized in particular by its small machine size. In particular, no abrasion or only small amounts of abrasion in the form of fine material and / or ultrafine material are generated within the device, which is removed immediately. In particular, the abrasion is removed directly during the rounding process and before and during product removal from the device, so that the device and the method achieve particularly good yields of rounded, at least largely fines-free, homogeneous graphite material. In particular, the device and the method produce a particularly homogeneous, largely abrasion-free product which in particular has a tapped density of at least 800 grams per liter.

[0029] It should be expressly mentioned at this point that all aspects and embodiments explained in connection with the device according to the invention equally relate to or can be partial aspects of the method according to the invention. Therefore, if certain aspects and / or relationships and / or effects are mentioned at any point in the description or in the claim definitions for the device according to the invention, this equally applies to the method according to the invention. The same applies conversely, so that all aspects and embodiments explained in connection with the method according to the invention equally relate to or can be partial aspects of the device according to the invention.Therefore, if at one point in the description or in the claim definitions of the method according to the invention certain aspects and / or relationships and / or effects are mentioned, this applies equally to the device according to the invention. Character description

[0030] In the following, exemplary embodiments will explain the invention and its advantages in more detail with reference to the accompanying figures. The relative sizes of the individual elements in the figures do not always correspond to the actual sizes, as some shapes are simplified and others are enlarged relative to other elements for better illustration. Figure 1 shows a device according to the invention for rounding graphite flakes of a graphite material. Figures 2A to 2Eshow the graphite material - in particular the graphite flakes used - before, during and after processing within a device according to the invention. Figures 3A to 3D show various views of a further embodiment of a device according to the invention for rounding graphite flakes of a graphite material. Figures 4A and 4B show different views into the interior of another embodiment of a device according to the invention. Figures 4A and 4B show different views of a part of the device. Figures 4C and 4D show different designs of the impact surface.

[0031] Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals are shown in the individual figures that are necessary for the description of the respective figure. The illustrated embodiments merely represent examples of how the device or method according to the invention can be configured and do not represent a definitive limitation.

[0032] Figure 1shows a device 1 according to the invention for rounding graphite flakes GF of a graphite material GM. The device 1 comprises a housing 2 designed approximately as a vertical cylinder, on the upper side of which a feed device 3 for supplying the graphite material GM is arranged, in particular a feed device 3 for supplying graphite flakes GF. In particular, in the exemplary embodiment shown, the feed device 3 is designed as a downpipe 4, but it can also be provided that the graphite material GM is supplied via an injector feed.

[0033] The graphite material GM impacts rounding tools 5. The corners of the graphite flakes GF are folded and wrapped around the core of the respective graphite flake GF. Smaller graphite particles agglomerate into larger, particularly spherical particles. Furthermore, the initial internal porosity is minimized during rounding. The graphite particles vGT rounded in this way have a smaller surface area than the originally used graphite flakes GF. This results in a lower irreversible capacitance and also a long service life. The smooth surface of the rounded graphite particles vGT prevents flaking or flaking. The powder with the rounded graphite particles vGT has an increased tamped density and thus a high energy density.The powder is particularly suitable for the production of lithium-ion batteries because the lithium ions have easier access to the graphite through the cavities formed between the rounded graphite particles (vGT). In particular, the lithium ions accumulate in the planes between the folded graphite flakes. The powder with the rounded graphite particles is chemically purified again after rounding and before use in battery production, etc., and then coated.

[0034] The device 1 comprises a plurality of rounding tools 5 arranged on a rotatably movable disk 7. The graphite material GM introduced into the interior of the device via the feed device 3 is grasped by the rounding tools 5, accelerated, and guided against an impact surface 6. The impact surface 6 represents, in particular, a region of the cylindrical inner surface 21 of the housing 2.

[0035] The rounding tools 5 are arranged, in particular, circumferentially and at regular intervals from one another on the outer circumference of a rotating disk 7, which is connected to a first drive 9 via a first drive shaft 8. The impact surface 6 and the rounding tools 5 are designed such that the graphite material GM impacts the rounding tools 5 at different angles, thereby achieving a particularly advantageous deformation, in particular folding, of the graphite flakes GF. The rounding tools 5 are optimized, in particular, for the highest possible number of particle impacts at different impact angles.

[0036] The device 1 further comprises a separating device 10, for example an air classifier with a classifying wheel 11. During the rounding of the graphite flakes GF, abrasion in the form of fine material and / or ultra-fine material FM can arise. Since the desired end product EP should preferably contain only rounded graphite particles vGT, the fine material and / or ultra-fine material FM is separated from the rounded graphite particles vGT directly within the device 1 and removed from the device 1. The separating device 10 is arranged above the disk 7 with the rounding tools 5. The classifying wheel 11 is connected to a second drive 13 via a second drive shaft 12. In particular, it is provided that the first drive shaft 8 and the second drive shaft 12 are arranged coaxially.

[0037] Process air PL is supplied from bottom to top via a supply nozzle 14 in the lower area of the device 1, in particular below the rotating disk 7 with the rounding tools 5, and is directed to the rounding area and via the guide elements 25 to the separating device 10. The process air PL entrains the fine material and / or ultrafine material FM and removes it from the device 1 via the suction nozzles 16.

[0038] Within the device 1, the graphite material GM comes into active contact at least once with at least one rounding tool 5, whereby the graphite material GM is imparted with a swirl. The guide elements 25 redirect the swirl-bearing graphite flakes GF, the swirl-bearing rounded graphite particles vGT, and the swirl-bearing fine material and / or ultrafine material FM in a vertical direction, in particular perpendicular to the rotating disk 7, and thus reach the separating device 10 at least largely without swirl. This ensures optimal flow to the separating device 10, resulting in high separation accuracy.

[0039] According to one embodiment of the invention, the graphite material GM is fed via the feed device 3 to the process chamber 40 of the device 1. The graphite material GM strikes the guide ring 41 and is guided past the classifier wheel 11, so that any fine dust already present is separated. The graphite material GM then strikes the disk 7 with the rounding tools 5, which generate the energy for the rounding. In particular, the graphite material GM is captured by the disk 7 with the rounding tools 5, accelerated, and thrown against the impact surface 6. During these first two process steps, the product outlet 17 is closed, as described in connection with the Figures 3A and 3D described in more detail below.

[0040] The process air PL enters the housing 2 of the device 1 via the supply nozzle 14 and flows through a gap 45 formed between the disc 7 with the rounding tools 5 and the impact surface 6. As it flows through the gap 45, the stressed graphite particles are selectively presented to the separator wheel 11 by the air volume flow through the guide ring 41. The material, which now comprises at least partially rounded graphite particles, returns to the disc 7 with the rounding tools 5 in an internal flow. The fine dust, in particular fine material and / or ultrafine material FM, leaves the device 1 with the process air and / or process air PL via the extraction nozzle 16.

[0041] The rounded graphite particles vGT (cf. Figures 2D and 2E) are withdrawn through the product outlet 17 via a suction device similar to an injector feed. The suction takes place directly on the inside of the guide ring 41. This ensures that no graphite material GM is withdrawn from the device 1 that has not previously been guided past the classifier wheel 11.

[0042] The graphite material GM is treated in the device for a defined time, during which it comes into active contact with the rotating rounding tools 5 several times, whereby the graphite flakes GF are folded and transformed into rounded graphite particles vGT. After a predefined time, it can be assumed that the graphite material GM largely consists only of rounded graphite particles vGT. The final product in the form of rounded graphite particles vGT can now be removed from the device 1 via a product outlet 17 and used, for example, for the production of batteries.

[0043] To further improve the stress on the graphite material GM through improved flow guidance, it can be provided that a cover ring 18 is arranged above each of the rounding tools 5. The cover ring 18 advantageously extends over all of the rounding tools 5 arranged on the circumference of the rotating disk 7 and enables advantageous circulation of the graphite particles to be rounded, since the cover ring 18 optimizes the flow guidance of the graphite particles within the device 1. This cover ring 18 prevents, in particular, the coarse graphite material GM, in particular the graphite flakes GF and / or already rounded graphite particles vGT, from being thrown upwards and circulating through the device 10 without contact with the rounding tools 5. The cover ring 18 enforces, in particular, multiple operative contact between the rounding tools 5 and the coarse graphite material GM.

[0044] According to one embodiment, the device 1 further comprises a control device 20, by means of which, for example, the first drive 9 and / or the second drive 13 and thus the speed of the classifier wheel 11 and / or the rotational speed of the disc 7 with the rounding tools 5 can be regulated and / or adjusted according to the product requirements.

[0045] Furthermore, it can be provided that the addition of graphite material GM is regulated based on a so-called cut-off value. In particular, this cut-off value is generated by the device 1 itself. When the running device 1 is filled with graphite material GM, the current consumption of the drives 9, 13 increases. The control device 20 contains information on at least one cut-off value, in particular information on current consumption values of the drives 9, 13. When a defined cut-off value or both defined cut-off values are reached, the supply of further graphite material GM is stopped. For example, the feed device 3 (see also description of the Figures 3A to 3C ) a valve which is controlled by the control device 20 when the cut-off value is reached and is closed due to the control signal so that no further graphite material GM enters the device 1.

[0046] During the rounding process, the current draw values can decrease again, providing information about the progress of the rounding process. In particular, according to one embodiment, if a second defined current draw value, also referred to as the second cutoff value, is undershot, the dosing and / or material feed can be restarted. The drives 9, 13 are not switched off as long as graphite material GM is still present in the device 1.

[0047] Alternatively, it can be provided that the device 1 is operated for a defined time after complete filling, ie after reaching the first switch-off value, which has been determined empirically in advance, for example, and after which the rounding of all graphite flakes GF is safely completed.

[0048] Controlling the supply of graphite material GM above the cut-off value ensures that the device 1 is not overfilled and, in particular, is filled in a reproducible manner in each production cycle.

[0049] The rounding of the graphite material GM using the device 1 described here and according to the method described here can be divided into three steps: filling, rounding, and discharging. These three steps cannot be clearly separated from one another, but are described individually below.

[0050] During filling, the graphite material GM is introduced into the process chamber 40, for example, by an injector. The process chamber 40 is also flowed through by an air flow process air PL with a circulation imposed on the rotating disk 7. The rounding tools 5 on the rotating disk 7 accelerate the graphite particles together with the process air PL in the direction of the inner surface 21 of the housing 2 and the graphite particles follow the air flow to the classifier wheel 11. The graphite particles then pass through the circuit defined by the air flow again. The power consumption of the second drive 13 of the classifier wheel 11 increases depending on the product load. In this way, the device 1 can be filled to a selected level and a direct process value is obtained which can be used as a switching point. During filling, if necessary.The dosage may be temporarily "re-dosed" to compensate for initial weight and / or concentration losses. However, once the desired level is reached, the filling process ends and the second rounding step begins.

[0051] In reality, the second rounding step begins as soon as the first graphite material GM enters device 1. This is because rounding begins as soon as the first graphite particles are guided in the air stream of the process air PL. However, we consider the above-mentioned switching point of the classifier flow generated within device 1 to be the uniform starting point. As soon as the desired fill level in device 1 is reached, dosing is not restarted until after the third discharge step, even if the predefined switching point is undercut at a later time. This is necessary to guarantee a uniform rounding time for all graphite particles. Varying the process parameters over the rounding time course can be useful in some areas.

[0052] The third discharge step is carried out in particular using a suction unit. The suction unit generates a negative pressure and is connected to the device 1 through a suction nozzle closed with a flap. At the beginning of the third discharge step or product removal step, the suction unit is opened and the extracted air is guided into a separating element. One embodiment of a suction unit 65 is described below in connection with the Figures 3A and 3Ddescribed. A cyclone with a filter, for example, is suitable as a separation device. Here, the product, including the rounded graphite particles, is separated from the gas. In conjunction with this volume flow, the product is pneumatically conveyed out of the process chamber 40, and the concentration decreases rapidly until it is completely emptied. During the process, the removal of fine material and / or ultrafine material FM and the stressing of the particles by the rounding tools 5 arranged on the rotating disk 7 continue to be active.

[0053] Figures 2A to 2E show the graphite material GM - in particular the graphite flakes GF used as starting material - before, during and after processing within a device 1 according to the invention. In particular, Figures 2A and 2B Different graphite flakes GF used as starting material in different magnifications. The graphite material GM according to Figure 2Acontains mainly small graphite flakes GF, while in Figure 2B essentially contains large graphite flakes gGF. Figure 2C shows an intermediate stage in the rounding of graphite material GM, in which partial rounding has already taken place by folding the large graphite flakes gGF and / or by agglomeration of small graphite flakes kGF. Figures 2D and 2E show rounded graphite material GM within the device according to the invention, which essentially only contains rounded graphite particles vGT and which in particular does not have any fine material and / or very fine material.

[0054] Figures 3A to 3D as well as Figures 4A and 4B show various views of a further embodiment of a device 1 according to the invention for rounding graphite flakes GF of a graphite material GM. In particular, Figure 3A a vertical cross-section through an upper area of the device 1 with closed suction unit 65, Figure 3Bshows an enlarged view of a section of Figure 3A , Figure 3C shows a horizontal cross-section through an upper region of the device 1 and 3D figure shows a vertical cross-section through an upper area of the device 1 with the suction unit 65 opened.

[0055] On the top side of the housing 2 of the device 1, a feed device 3 in the form of a downpipe 4 is provided for feeding the graphite material GM containing, for example, graphite flakes GF. A rotating disk 7 is arranged in the interior of the device 1. On the top side, on the outer circumference of the disk 7, adjacent to an inner circumferential surface 21 or the guide ring 41 of the housing 2 of the device 1, rounding tools 5 are arranged and / or fastened in a regular arrangement. The disk 7 is seated on a drive shaft 8 and is driven by it in rotation about a rotational axis D. The inner circumferential surface 21 is designed adjacent to the disk 7, in particular as an impact surface 6, and has a structuring or profiling that supports the folding and / or agglomeration of the graphite material GM.

[0056] The graphite material GM fed through the downpipe 4 strikes the rotating rounding tools 5 arranged on the rotating disc 7 and the rotating rounding tools arranged thereon, is accelerated, and guided against the impact surface 6. The graphite material GM is then guided by the ascending air flow from the guide element 25 to the separator wheel 11.

[0057] Preferably, the suction unit 65 has a suction position AP directly on the inner guide ring 15 of the guide apparatus. The product is removed by means of the suction unit 65, in particular radially to the inner guide ring 15. During the rounding of the graphite material GM, the suction unit 65 is closed by a movable cylinder 66 extending radially to the inner guide ring 15. The cylinder 66 is located, in particular, in a so-called closed position 66c (cf. Figure 3A). In particular, in this case, only air L is sucked in by the suction unit 65 via the secondary air nozzle 67. This prevents graphite material GM from being sucked out before it can hit the rounding tools 5 and the impact surface 6. The suction unit 65 is only opened for the removal of the rounded graphite material vGT via the product outlet 17 by moving the movable cylinder 66 (see 3D figure ). In particular, a product-air mixture comprising the rounded graphite particles vGT and air L sucked in via the secondary air nozzle 67 is sucked into the suction unit 65 during and after the cylinder 66 is moved back into the opening position 66o.

[0058] According to one embodiment, it can be provided that the side surface 50 of the rounding tools 5, which faces the rotational axis D of the disk 7, is each provided with a radius R. This rounded side surface 50 forms a further impact surface 51, which further supports the rounding of the graphite material GM.

[0059] Furthermore, it can be provided that all side surfaces of the rounding tools 5 standing on the disk 7 each have an identical height and that the upper side of the rounding tools 5 is arranged in a plane parallel to the plane of the rotating disk 7

[0060] The device 1 further comprises a separating wheel 11 as a separating device 10, via which the abrasion in the form of fine material and / or ultrafine material FM produced during the rounding of the graphite material GM is separated and removed from the device 1 via the suction nozzle 16. The separating wheel 11 is arranged above the disk 7 with the rounding tools 5. In the present embodiment, the separating wheel 11 is arranged on a shaft coaxial with the drive shaft 8 of the disk 7, so that the separating wheel 11 and the disk 7 can be rotated independently of one another.

[0061] Process air PL is supplied via a supply nozzle 14 in the lower area of the device, which flows upwards to the rounding area and through the guide elements 25, and is thereby partially and mainly directed to the separating device 10. The main flow of process air PL entrains the fine material and / or ultrafine material FM and removes it from the device 1 via the suction nozzle 16.

[0062] The rounding tools 5 are, for example, placed on the disk 7 and fixed thereto via suitable fastening means 30, for example by means of a screw connection 31, a welded connection, an adhesive bond, or the like. Alternatively, the disk 7 can also be formed integrally with the rounding tools. The guide elements 25 are arranged above the rounding tools 5 in such a way that they partially cover the rounding tools 5 from above. In particular, it is provided that adjacent rounding tools 5 are covered differently from above by guide elements 25. Preferably, in a regular arrangement, some rounding tools 5* are also not covered by guide elements 25. In particular, it can be provided that the number of guide elements 25 is fewer than the number of rounding tools 5.Since the guide elements 25 are arranged statically within the device, the relative arrangement of rounding tools 5 and guide elements 25 changes permanently during operation of the device.

[0063] In this exemplary embodiment, the guide elements 25 are designed in particular as guide plates 26 which are arranged substantially vertically and extend radially to the axis of rotation D and which can be bent in the lower region opposite to the direction of rotation DR, so that an obtuse angle is formed between the bent region 27 and the vertical guide plate 26 (see also Figures 4A and 4B). The bent area 27 is bent in particular opposite to the direction of rotation DR and ensures an optimized, shock-free entry of the graphite particles into the vertical part of the guide apparatus 60 comprising the guide elements 25. In particular, the bent area 27 of the guide element 25 supports the prescribed redirection of the swirling fine material and / or ultra-fine material FM as well as the graphite material GM in a direction perpendicular to the rotating disk 7. The supplied graphite material is first guided past the classifier wheel 11 within the air flow, strikes the disk 7 and is guided to the rounding tools 5 and the impact surface 6.

[0064] The guide elements 25 can be connected to one another, in particular on their side facing the rotation axis D, via a so-called air guide ring 15. In particular, the guide elements 25 together with the air guide ring 15 form the so-called guide device 60. The at least one guide device 60 redirects the graphite material GM, which is subject to swirl after contact with the rounding tools 5 and / or the impact surface 6, in a largely vertically upward direction and is fed to the separating device 10 largely without swirl. This ensures optimal flow to the separating device 10, resulting in high separation accuracy. Part of the process air PL can be separated as a secondary flow and circulate within the rounding area between the impact surface 6 and the rounding tool 5.This secondary air assists in ensuring that the graphite material GM comes into contact with the rounding tools 5 multiple times and at different angles, thereby improving the folding and / or agglomeration of the graphite material GM into rounded graphite particles vGT.

[0065] In the Figures 3A and 3B Furthermore, a cover ring 18 can be seen above the rounding tools 5, which also serves to retain the graphite material GM in the rounding area and thereby increase the number of contacts between the graphite material GM and the impact surface and / or the rounding tools 5. In particular, the cover ring 18 improves the circulation of the graphite material GM within the device 1 due to optimized flow guidance.

[0066] According to one embodiment, a distance A between adjacent rounding tools 5 is between 0.5 times a width B5 of the rounding tools 5 to five times the width B5 of the rounding tools 5. The width B5 of the rounding tools 5 is determined orthogonally to the radial r(D) starting from the rotational axis D of the disk 7. Preferably, the distance A is less than three times the width B5 of the rounding tools 5, particularly preferably less than 1.5 times the width B5 of the rounding tools 5. In the example shown according to Figure 3C the distance A is approximately a width B5 of the rounding tools 5.

[0067] The number of rounding tools 5 is preferably between 15 and 35 rounding tools per m circumference of the rotating disk 7 on which the rounding tools 5 are arranged.

[0068] The removal of the end product, in particular the rounded graphite particles vGT, takes place via a product outlet 17, preferably after the graphite material GM has been treated for a defined time within the device 1. A suction unit 65 is preferably assigned to the product outlet 17. The suction unit 65 generates a negative pressure, for example by retracting a movable cylinder 66 assigned to the product outlet 17, and also opens the product outlet 17 by retracting the movable cylinder 66. Now, the graphite material GM located within the device 1, which preferably only consists of rounded graphite particles, is sucked out together with the air located within the device 1, wherein the sucked-out air with the graphite particles is first guided into a separation device (not shown), for example into a cyclone with a filter.In the separator, the product, including the rounded graphite particles, is separated from the air.

[0069] According to one embodiment of the invention, the method is not a continuous method in which graphite material GM is continuously supplied and end product in the form of rounded graphite particles vGT is permanently removed, but rather a batch method in which the device 1 is filled with a defined amount of graphite material GM and is operated for a defined time at a defined rotational value before the end product in the form of rounded graphite particles vGT is removed.

[0070] In the device 1, the graphite material GM is preferably only fed to the classifier wheel 11 after rounding has taken place, while the abrasion in the form of fine material and / or ultrafine material FM can already be fed to the classifier wheel 11 during the rounding process and removed from the device 1 via a suction nozzle 16. In particular, the product is removed via the product outlet 17 only after the classifying process, so that the removed end product essentially only contains rounded graphite particles vGT and in particular no fine material and / or ultrafine material FM.

[0071] The number and shape of the rounding tools 5 are optimized and adapted to the process. The impact surface 6 is also optimized to ensure gentle stress on the graphite material GM during rounding and to avoid fine and / or ultrafine material FM.

[0072] Figures 4A and 4Bshow different views of a part of the device 1 in perspective. For an explanation of the individual components, particular reference is made to the description of Figure 3B referred to. The Figures 4A and 4B correspond essentially to each other, whereby in the representation of the Figure 4B the cover ring 18 above the rounding tools 5 has been omitted so that the rounding tools 5 can be seen more clearly.

[0073] Figures 4C and 4D show different designs of the impact surface 6 and a rounding tool 5 arranged on the rotating disk 7. The rounding tool 5 has a longitudinal axis L5, which coincides with a radial r(D) emanating from the rotational axis of the disk 7. The side surface 50 of the rounding tool 5 facing the rotational axis of the disk 7 has a radius R or is designed as a polygon. Preferably, the side surface 50 is subdivided mirror-symmetrically by the radial r(D).

[0074] The design of the side surface 50 facing the rotational axis of the disk 7 as a radius R or as a polygon with a plurality of partial areas arranged at an angle to one another results in gentle stress on the graphite material GM. This causes it to fold and, in particular, not shred, since there is always a central impact between the surface of the rounding tools 5 and the graphite material GM.

[0075] The side surface 55 opposite the side surface 50 facing the axis of rotation of the disk 7 is also referred to in particular as the side surface 55 facing away from the axis of rotation. This side surface 55 facing away from the axis of rotation is preferably not divided mirror-symmetrically by the radial r(D), since the side surface 55 consists of two partial regions 56 and 57 that are at an obtuse angle ε to one another. In particular, the partial region 57 leading in the direction of rotation DR is arranged orthogonally or essentially orthogonally to the radial r(D), while an acute angle α is formed between the partial region 56 trailing in the direction of rotation DR and an extension of the leading partial region 56. The sum of the acute angle α and the obtuse angle ε preferably amounts to 180 degrees.

[0076] Furthermore, it is preferably provided that the length L57 of the partial region 57 leading in the direction of rotation DR is significantly shorter than the length L56 of the partial region 56 trailing in the direction of rotation DR. In particular, the length L57 is between 5% and 30% of the length L56, particularly preferably between 13% and 20%.

[0077] The above-described arrangement of the partial areas 56, 57 of the side surface 55 results, in particular, in the partial area 57 leading in the direction of rotation DR being arranged closer to the impact surface 6. The above-described angle α is also referred to as the clearance angle. This clearance angle α results, in particular, in the gap 45 formed between the impact surface 6 and the rounding tool 5 tapering in the direction of rotation DR, which additionally supports the gentle rounding of the graphite material GM. In particular, this counteracts undesirable thermal stress on the graphite material GM due to crushing and / or friction.

[0078] Furthermore, an angle β is formed between the profile of the impact surface 6 and the partial area 57 arranged closer to the impact surface 6, which angle is between 50 degrees and 90 degrees depending on the design variant. Particularly preferably, the angle β is always greater than 55 degrees and also always less than 90 degrees.

[0079] According to the Figures 1 , 3 and 4 The impact surface is formed in particular by the inner surface of a cylindrical component. Figure 4C The impact surface 6 is designed as a cylinder with a serrated inner surface 70. This profiling of the impact surface 6 enlarges the surface area onto which the graphite material GM impacts. In addition, the corners of the serrated inner surface 70 represent additional impact elements 72, which further support the rounding of the graphite material GM. Figure 4D The impact surface 6 is designed as a cylinder with a corrugated inner surface 71, which also increases the surface area onto which the graphite material GM impacts. With the corrugated inner surface 71, sharp edges on the impact surface 6 are eliminated, allowing the graphite material GM to be treated even more gently, thus further optimizing the rounding.

[0080] With the device 1 according to the invention and the method according to the invention, the yield of rounded graphite particles vGT based on the feed quantity of graphite material GM is significantly increased compared to the devices and methods known from the prior art.

[0081] The device and method are particularly suitable for rounding multilayer materials that allow folding and / or agglomeration of the material. Furthermore, the materials to be processed must exhibit a certain degree of flexibility to prevent them from breaking during rounding.

[0082] The embodiments, examples, and variants of the preceding paragraphs, the claims or the following description and figures, including their various views or respective individual features, may be used independently of one another or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless the features are incompatible.

[0083] Although the figures generally refer to "schematic" representations and views, this by no means implies that the figures and their descriptions are of secondary importance with regard to the disclosure of the invention. A person skilled in the art will be perfectly capable of deriving sufficient information from the schematic and abstractly drawn representations to facilitate their understanding of the invention, without their understanding being in any way impaired by the drawn, possibly not exactly scaled, proportions of parts of the device or other drawn elements.The figures thus enable the skilled reader to derive a better understanding of the inventive concept formulated in a more general and / or abstract manner in the claims and in the general part of the description on the basis of the more concretely explained implementations of the method according to the invention and the more concretely explained functioning of the device according to the invention.

[0084] The invention has been described with reference to a preferred embodiment. However, it is conceivable to a person skilled in the art that modifications or variations of the invention can be made without departing from the scope of the following claims. List of reference symbols

[0085] 1Device 2Housing 3Feeding device 4Downpipe 5,5*Rounding tool 6,6-5,6-19Baffle 7Disk 8First drive shaft 9First drive 10Separating device 11Classifying wheel 12Second drive shaft 13Second drive 14Feed nozzle 15Air guide ring 16Extraction nozzle 17Product outlet 18,18-5,18-19Cover ring 19Second rounding tools 20Control device 21Inner surface 25Guide elements 26Guide plates 27Knocked-off area 30Fasteners 31Screw connection 40Process chamber 41Guide ring 45Gap 50Side surface facing the rotation axis 51Baffle 55, 55-5,55-19Side surface facing away from the rotation axis 56Sub-area 57Sub-area 60Control unit 65Extraction unit / extraction device 66Movable cylinder 66cMovable cylinder in closed position 66oMovable cylinder in open position 67Secondary air nozzle 70Serrated inner surface 71Corrugated inner surface 72Additional impact element ADistance APExtraction position B5Width of the rounding tools d5,d19,Distance from the rotational axis d6-1,d6-2Distance from the rotational axis DRotational axis DRDirection of rotation EPEnd product FMFine material and / or ultrafine material GFGraphite flakes GMGraphite material gGFLarge graphite flakes kGFSmall graphite flakes LAir L5Longitudinal axis L56Length of the trailing section in the direction of rotation L57Length of the leading section in the direction of rotation RRadius PLProcess air vGTRounded graphite particles

Claims

1. An apparatus (1) for rounding a graphite material (GM), the apparatus (1) comprising an inlet (3) for feeding the graphite material (GM) to the apparatus (1); a plurality of rounding tools (5) designed to rotate in a circulating manner, which rounding tools (5) are arranged on the outer circumference of a disc (7) rotating about an axis of rotation (D) and in a direction of rotation (DR); at least one guide apparatus (60), which comprises a plurality of guide elements (25) and an inner guide ring (15); a separating device (10) for separating fine material and ultrafine material (FM); a product outlet (17); wherein a cover ring (18) is arranged above the rounding tools (5), characterised in that the apparatus (1) furthermore comprises a suction device (65) for product material assigned to the product outlet (17), wherein a suction position of the suction device (65) is formed directly on the inner guide ring (15), and wherein the suction device (65) extends radially to the inner guide ring (15).

2. The apparatus (1) according to claim 1, wherein the cover ring (18) extends over all rounding tools (5) arranged on the outer circumference of the disc (7).

3. The apparatus (1) according to claim 1 or 2, wherein the graphite material (GM) has an angular momentum after single or multiple active contact with at least one rounding tool (5), and wherein the graphite material (GM) is redirectable into a substantially perpendicular direction by the at least one guide apparatus (60) and is feedable to the separating device (10) largely without angular momentum.

4. The apparatus (1) according to one of the previous claims, wherein the rounding tools (5) each comprise a side surface (50) facing toward the axis of rotation (D), wherein this side surface (50) is designed to be convex or has a radius (R) toward the axis of rotation (D), or wherein the side surface (50) facing toward the axis of rotation (D) is formed by a plurality of polygons.

5. The apparatus (1) according to one of the previous claims, wherein the number of guide elements (25) is less than the number of rounding tools (5).

6. The apparatus (1) according to one of the previous claims, wherein the apparatus (1) comprises at least one device to supply air for an airflow directed upward from below, wherein the graphite material (GM) is feedable several times to the rounding tools (5) by means of the supplied air, and wherein the air supply is furthermore designed to separate the fine material and ultrafine material (FM) from the rounded graphite material (GM).

7. The apparatus (1) according to one of the previous claims, wherein the separating device is an air classifier with classifier wheel (11), wherein the classifier wheel is arranged coaxially above the rotating disc (7) with the rounding tools (5).

8. The apparatus (1) according to one of the claims 5 to 7, wherein the guide elements (25) are designed as guide plates which are arranged on the guide ring, and wherein the guide ring (15) is arranged statically above the rotating disc (7) with the rounding tools (5), wherein the guide plates are formed above the rounding tools (5), each in some areas in a plane perpendicular to the rotating disc (7) and to a tangent of the rotating disc (7), and wherein the guide plates are designed to be bent in a lower area away from the perpendicular plane in the direction opposite to the direction of rotation (DR).

9. The apparatus (1) according to one of the previous claims, furthermore comprising a control device (20), wherein the feed of graphite material (GM) via the inlet (3) is controllable by means of the control device (20).

10. The apparatus (1) according to one of the previous claims, wherein the suction device (65) comprises a movable cylinder (66) or wherein the suction device (65) is assigned a movable cylinder (66), wherein the movable cylinder (66) in a first working position closes the product outlet (17).

11. A method for rounding a graphite material (GM) in an apparatus (1), wherein the graphite material (GM) comes into active contact with at least one rounding tool (5) of a plurality of rounding tools (5) of the apparatus (1), which rounding tools (5) are designed to rotate in a circulating manner, and wherein a cover ring (18) is arranged above the rounding tools (5), wherein the cover ring (18) limits the movement space for a process air flow carrying graphite material (GM) and increases a number of contacts between the graphite material (GM) and the at least one rounding tool (5), wherein product material is sucked off directly at an inner guide ring (15) of the apparatus (1), wherein a suction device (65) of the apparatus (1) extends radially to the inner guide ring (15).

12. The method according to claim 11, which is carried out in an apparatus (1) according to one of the claims 1 to 10, wherein the rounded graphite material (GM) is guided angular momentum-free to a separating device (10) of the apparatus (1).

13. The method according to claim 11 or 12, wherein a control device (20) of the apparatus (1) contains information on a switch-off value, wherein the feed of further graphite material (GM) is stopped when the defined switch-off value has been reached, in particular, wherein the switch-off value is calculated from a value of the current consumption of the drives.