EP3253493B1 - Comminuting apparatus for recycling of secondary raw materials from disposed stuff and method of control therefor - Google Patents

Description

The present invention relates to a crushing apparatus for recovering secondary raw materials from discarded material, and to a method of controlling such a crushing apparatus.

Secondary raw materials are usually understood to mean raw materials that are obtained by processing (recycling) waste material. They serve as starting materials for new products and thus differ from the primary (natural) raw material. In the context of the present invention, therefore, these are, in particular, those substances which are used for the second or repeated time in a cascade or multiple use within the framework of the raw material economy. The use of secondary raw materials saves natural resources and contributes to sustainable development.

In the context of the present invention, material disposed of may, in particular, be material composites, as occur, for example, in the recycling treatment of electrical and electronic devices or assemblies, or non-recycled mono- or mixed materials of ferrous metals Iron metals, fiber composite or other plastics and / or wood and / or Halmfraktionen such as old or recycled wood, debarked logs, Kappholzstücke- or other wood residues such as chips in particular to waste paper or straw, as well as material fractions from upstream other Coarse shredding processes in the recycling industry or slag from incineration processes.

For the industrial recovery of secondary raw materials from discarded material, a variety of crushing devices have become known.

For example, be on here in the EP 1 536 892 B1 , the EP 1 721 674 B1 or the WO 2010/057604 A1 each comprising a first crushing stage with a rotating in a cylindrical housing impact tool to the central portion of a feed channel for the discarded material is guided, wherein the impact tool rotates at high speeds and thereby generates a radial air vortex high speed, which in the first crushing stage impact-crushed material fractions along in the cylindrical housing formed openings to the outlet of sufficiently crushed material fractions leads into a plenum.

A disadvantage of the known from the prior art crushing devices is limited by the outlet openings in the housing material throughput.

Proceeding from this, the object of the present invention is to provide a comminution device which is improved, in particular with regard to the material throughput, for the recovery of secondary raw materials from disposed material and a method for the control thereof. In an extension of the object, the device and the method should serve in particular the dust production from the disposed material.

According to the invention, this object is achieved by a comminuting device with the features of patent claim 1 and by a method for controlling with the features of patent claim 10.

The solution for the shredder for recovering secondary raw materials from discarded material, essentially comprises a first crushing stage with a feed channel for supplying the discarded material to a first housing with a rotating impact tool for crushing the discarded material into a blow-crushed material fraction and for producing a Air vortex, which from the first crushing stage the impact-comminuted material fractions between the walls of a double-walled second housing of a downstream of the first crushing stage, second crushing stage spends, wherein the double-walled housing of the second crushing stage 20 is provided on the outer wall with a first sieve and on the inner wall with a second sieve, which pass through these sieves friction-comminuted material fractions in a downstream of the respective sieve collecting space.

Preferably, on the double-walled housing of the second crushing stage on the inside of the outer wall, a first Reibsieb and arranged on the outside of the inner wall, a second Reibsieb.

By the second crushing stage according to the invention is designed as a double-walled housing whose walls are each provided with sieves for the passage of Reibfein-comminuted material fractions, a crushing device can be provided with an advantageously significantly improved material throughput for recovered secondary raw materials from discarded material.

Particularly preferably, the air vortex can be exploited in order to rub the material to be comminuted on itself and / or on the friction elements or friction screens for comminution.

Advantageous embodiments and developments, which can be used individually or in combination with each other, are the subject of the dependent claims.

Thus, in one embodiment, the comminution device is preferred if the inside of the first wall of the first comminution stage is provided with splitting edges, which further promote the impact comminution of disposed material when it is thrown by the impact tool onto the splitting edges.

If mono-materials are used as disposed material and / or secondary raw materials with uniformly distributed particle sizes are to be obtained, the use of friction sieves with hole diameters of equal size in both sieves has proven successful in one embodiment of the comminution device.

Insofar as disposed material, on the other hand, mixed materials are used and / or secondary raw materials (whether obtained from mono- or mixed materials) to be obtained with differently distributed particle sizes, in an alternative embodiment of the crushing device, the use of Reibsieben with different sizes Proved hole diameters, the hole diameter of a Reibsiebes are preferably selected to be larger than in the other Reibsieb.

In both cases, in particular rubbing fabrics have proven successful, which are preferably designed as so-called. Conidur® screens, as these are offered by the German company HEIN, LEHMANN GmbH. As is known, Conidur® sieves are manufactured according to a special process, which makes it possible to produce very fine holes in sheet thicknesses, which can amount to a multiple of the hole diameter. Advantageously, Conidur® screens have, in particular, conical holes, wherein the passage direction is inclined, so that a scale-like, rough surface defining the particle size assists the comminution process.

As far as the particle size - depending on the supplied disposed material - has a significant influence on the technical properties of the secondary raw material and therefore require the Reibsiebe rubbed-crushed material fractions require a more differentiated particle size distribution, in an advantageous embodiment of the invention the shredding device according to the invention further defined particle sizes tuned sieves, be downstream.

In order to be able to recover frictionally comminuted fiber material fractions with a defined fiber length, hole spacings in the friction sieves are preferred which are smaller in the circumferential direction of the double-walled housing than in its longitudinal extent. In other words: as far as the longitudinal direction and thus typical direction of impact-crushed material fractions they encounter larger hole distances than in transverse extension, this has to Advantage that the holes in the Reibsieben unfold by sufficient distance from each other a longitudinal fibers abreibende effect.

In a further embodiment of the comminuting device, it is preferred if the cover of the double-walled housing of the second comminution stage is provided with friction strips which further promote the friction comminution of impact-comminuted material fractions as they pass through the reis.

In a further embodiment of the comminution device, it is preferable to support the throughput of the, in particular friction-comminuted, material fractions through the device by a suction air flow.

It has proven particularly useful to assign at least the second plenum a material throughput promoting suction.

The present invention also relates to a method for controlling a comminuting device as described above, which is characterized by adjusting means by which the ratio of the volume flows in the collecting chambers is adjustable so that the volume flow of friction-comminuted material fractions in the collecting space behind the inner wall of the housing of the second Crushing stage is greater than the volume flow of friction-cut material fractions in the collecting space behind the outer wall of the housing of the second crushing stage.

A first development of the method is preferably characterized in that the speed of at least one suction means can be varied as an adjusting device for the volume flow ratio.

A second development of the method is preferably characterized in that a control flap which throttles the volume flow is arranged as the adjusting device for the volume flow ratio in at least one collecting space.

A third development of the method is preferably characterized in that the motor current of an electric motor driving the impact tool is adaptable, in particular in the event of changes or fluctuations in the material input and / or imminent blockage in the first housing of the first crushing stage.

In the case of comminution devices according to the invention, in particular volumetric flow ratios have proven successful in which the ratio of the volume flows from the outer collecting space to the inner collecting space is less than 1, preferably in particular 2: 3.

Finally, a development of the method is characterized in that the volume flow ratio is indirectly monitored by measuring the back pressure in the collecting chambers, a correctly adjusted volume flow ratio is characterized in that the back pressure in the inner plenum behind the inner wall of the housing of the second crushing stage is smaller than the back pressure in the outer collecting chamber behind the outer wall of the housing of the second crushing stage.

• Materialverbunden, wie sie beispielsweise bei der recycling-Aufbereitung von Elektro- und Elektronik-Geräten bzw. -baugruppen auftreten; und/oder
• Recycling-Mono- oder Mischmaterialien aus Eisen-Metallen, Nicht-Eisen-Metallen, Faserverbund- oder anderen Kunststoffen; und/oder
• Holz- und/oder Halmfraktionen wie Alt- oder Recyclingholz, entrindetes Stammholz, Kappholzstücke oder andere Holzreste wie insbesondere Späne, Altpapier oder Stroh; und/oder
• Materialfraktionen aus vorgeschalteten anderen Grob-Zerkleinerungs-prozessen in der Recycling-Industrie oder Schlacken aus Verbrennungsprozessen.

The present invention is suitable for the industrial recovery of secondary raw materials, in particular from

• Material composites such as occur in the recycling of electrical and electronic equipment or assemblies; and or
• Recycled mono- or mixed materials of iron metals, non-ferrous metals, fiber composite or other plastics; and or
• Wood and / or Halmfraktionen such as old or recycled wood, debarked logs, Cape wood pieces or other wood residues such as in particular shavings, waste paper or straw; and or
• Material fractions from upstream other coarse shredding processes in the recycling industry or slags from combustion processes.

However, the present invention can serve in particular for the production or preparation of substitute fuels, which can preferably be burned in dust burners after classification or screening. The use as additional fuel in firing is conceivable.

These and other features and advantages of the invention will be further elucidated with reference to two exemplary shredders shown in the drawings for recovering secondary raw materials from discarded material, to which the present invention is not limited.

• Fig. 1 ein erstes Ausführungsbeispiel einer Zerkleinerungsvorrichtung zur Rückgewinnung von Sekundärrohstoffen, insbesondere Partikelgrößen gleicher Korngrößenverteilung, beispielsweise aus entsorgten Faserverbund-Materialen; und
• Fig. 2 ein zweites Ausführungsbeispiel einer Zerkleinerungsvorrichtung zur Rückgewinnung von Sekundärrohstoffen, insbesondere Partikelgrößen unterschiedlicher Korngrößenverteilung, beispielsweise aus entsorgten Holz- und/oder Halmmaterialien.

They show schematically:

• Fig. 1 a first embodiment of a crushing device for the recovery of secondary raw materials, in particular particle sizes of the same particle size distribution, for example, from disposed fiber composite materials; and
• Fig. 2 a second embodiment of a crushing device for the recovery of secondary raw materials, in particular particle sizes of different particle size distribution, for example, from disposed wood and / or Halmmaterialien.

In the following description of preferred embodiments, like reference numerals designate like components.

In the FIGS. 1 and 2 In each case, a comminuting device 1 for the recovery of secondary raw materials 99 from disposed material 90 is shown.

It can be seen how in a lower region of the comminution device 1 a first comminution stage 10 is realized. The this disintegration stage 10 supplied by a feed channel 50 disposed material 90 is thereby smashed by a, trained in a known manner, for example, as a blade rotor, impact tool 12. The impact tool 12 rotating in a first, for example cylindrical or hexagonal, octagonal or other polygonal shaped housing 11 is preferably dimensioned such that a radial air vortex and thus a sifter action for impact-comminuted material fractions 91 are created, depending on the density of the supplied material 90 in which blow-crushed material fractions 91 are spun at high speed into a second comminution stage 20 arranged above the first comminution stage 10, which have undergone sufficient impact comminution.

The impact tool 12 may be equipped with blades (not shown), which promote the previously described sifter effect.

If - as shown - the inside of the housing 11 of the first crushing stage 10 is provided with splitting edges 61, the impact crushing of the discarded material 90 can be further promoted when this discarded material 90 by the rotating in the first crushing stage 10 impact tool 12 on the Split edges 61 is thrown and split.

The housing 21 of the second crushing stage 20 is formed according to the invention as a double-walled housing 21, between the outer wall 22 and inner wall 23, the impact-comminuted material fractions 91 are thrown, and which are each provided with Reibsieben 32, 33 for the passage of reibfein-comminuted material fractions 92nd 93 in a respective rubbing screen 32, 33 downstream collecting space 42, 43. The second crushing stage 20 is thus by triturating previously impact-crushed material fractions 91 not only on a rough inside of the outer wall 22 of the double-walled housing 21 but also on a rough outside the inner wall 23 of the double-walled housing 21 is achieved. The provision of two Reibsiebe 32, 33 increases the material throughput for recovered secondary raw materials 99 from disposed material 90 advantageously significantly. The double-walled housing 21 may be cylindrical or six-, eight- or other polygonal shaped analog or different from the first housing 11.

So that not above the outer and inner walls 22, 23 emerge impact-crushed material fractions 91, these are preferably covered with a cover 24, whereby by the outer and inner walls 22, 23 and the cover 24, a space 25 for in the second crushing stage 20 aufzibenden impact-crushed material fractions 91 is limited. If - as also shown - the lid 24 of the double-walled housing 21 of the second crushing stage 20 is provided with friction strips 62, also the friction-crushing impact-crushed material fractions 91 on be promoted when these material fractions 91 pass the friction 62.

In particular, the transport of the material fractions 91, 92, 93 in the purely mechanically generated air vortices and / or additionally assisted with suction by the comminution device 1 can take place.

In the case of the last-mentioned embodiment, it has proved particularly useful to associate with both collecting spaces 42, 43 or at least one collecting space 42 or 43 an extraction means 52, 53 which promotes material throughput.

This is preferably designed such that via the feed channel 50 also fresh or - as far as the discarded material requires drying - also dry or warm air is sucked. Of course, this air in the feed channel 50 may also be provided by alternative or cumulative means. In any case, it has proven useful to form the housing 11 preferably closed in the region of the first comminution stage 10 so that no air can escape and weaken a suction air flow in the direction of the second comminution stage 20.

As a result of the air vortices always generated at least mechanically by means of the percussion tool 12, impact-comminuted material fractions 91 from the first comminuting stage 10 are not only thrown upwards into the second comminution stage 20 but are additionally rotated in the air vortex.

The necessary air flow through the friction screens 32, 33 is preferably realized by means of a control method, which is characterized by adjusting means, by means of which the volume flows v̇ 42, v 43 are adjustable. In particular, it is preferred that the ratio of the volume flows v̇ 42: v̇ 43 is adjustable so that the volume flow v̇ 43 reibfein-minced material fractions 93 in the collecting space 43 in the flow direction behind the inner wall 23 of the housing 21 of the second crushing stage 20 is greater than the volume flow v̇ 42 Reibfein-crushed material fractions 92 in the collecting space 42 behind the outer wall 22 of the housing 21st

The pressures P42 >> P43 will be set, which consequently serve as indicators for the ratio of the volume flows v̇ 42: v̇ 43 can. Since pressures P are easier to measure than volumetric flow rates v. 42 << 43 is indirectly monitored by measuring the pressures P42, P43 in the collecting chambers 42, 43, wherein a correctly set volumetric flow ratio v̇ 42 << V 43 thereby characterized that the pressure P43 in the internal collection chamber 43 in the flow direction behind the inner wall 23 of the housing 21 of the second comminution stage 20 is smaller than the pressure P42 in the outer plenum 42 in flow direction behind the outer wall 22 of the housing 21 of the second Comminution stage 20. These are essentially dynamic pressure ratios.

A further development of the method is preferably characterized in that the speed D52 and / or D53 of at least one suction means 52, 53 can be varied as an adjusting device for the volume flows v̇ 42, v̇ 43 or the volume flow ratio v̇ 42 << v̇ .

A second development of the method is preferably characterized in that as actuating device for the volumetric flow V 42, V 43 or the volume flow ratio V 42 << V 43 in at least one collecting space 42, 43 is a the flow rate V 42, V 42 throttling control flap 72, 73 is arranged.

A third development of the method is preferably characterized by the fact that the motor current of an electric motor 13 driving the impact tool 12 can be adapted, in particular in the case of changes or fluctuations in the material input and / or imminent blockage in the first housing 11 of the first comminution stage 10.

Volumetric flow ratios in which the ratio of the volume flows v̇ 42: v̇ 43 from the outer collecting space 42 to the inner collecting space 43 is less than 1, preferably in particular 2: 3, have proved particularly useful in the size reduction apparatuses according to the invention .

Fig. 1 shows a first embodiment of a crushing device 1 for the recovery of secondary raw materials 99, for example, from disposed fiber composite materials, with a particle size or a particle size distribution.

In particular, from the increasing proportion of carbon fiber reinforced plastics in different industries inevitably arises that more and more discarded CFRP products are produced as waste, which must then be recycled in terms of product responsibility. The utilization of CFRP materials is becoming increasingly important due to its extensive use in the aerospace industry, the automotive industry, the wind energy industry and many other areas. Here, the value of the carbon fibers is particularly important, for whose production a very high energy expenditure has already been invested. With high-quality recycling, this energy can at least be preserved to a high degree if it is possible to develop and establish processes that involve only the lowest possible degradation of the fibers. This is namely a prerequisite for the fact that the properties of the fibers can also be used in a second-generation component and remain usable. In addition, the carbon fibers (just because of the very complex production) are a relatively high-priced raw material. Thus, not only ecological reasons for the recycling of fiber composites are available, but it is also an economically interesting starting point to use the recovered fibers.

As in Fig. 1 illustrated, the holes are preferably used for use Reibsiebe coming 32, 33 in both Reibsieben 32, 33 preferably uniformly designed so that these broken-crushed fiber composite material fractions 91 are rubbed so that arise as uniform as possible fibers of a defined length, which is sufficient to be able to transfer after further processing of the recovered fibers, eg preparation in a yarn or a flat semi-finished, again acting in a component forces between the fibers and the surrounding matrix.

In particular, in this context, the training of Hole distances in the Reibsieben 32, 33 proven, which in typical direction of impact-crushed material fractions 91, ie the flowing air vortex, greater distances than in the transverse extent thereto, so that the holes in the Reibsieben 32, 33 by sufficient distance from each other a longitudinal fibers abreibende effect unfold, so let shredded-fiber material fractions 92 with defined fiber length enter the plenum 42.

The fibers of uniform length which have passed through the rubbing sieves 32, 33 into the collection space 42 arranged downstream in the direction of flow can be supplied as secondary raw material 99 with or without suction means 52 to a central collecting space.

Fig. 2 shows a second embodiment of a crushing device 1 for the recovery of secondary raw materials 99, for example, from discarded wood materials with two different particle size distributions.

Even in the industrial wood-based material sector, such as the production of chipboard, pellets or briquettes, the treatment of disposed wood and / or Halmmaterialien is inevitable before they can be supplied to the above-mentioned processing or recycling. For this purpose, for example, as old or recycled wood, debarked logs, Cape wood pieces or other wood residues such as shavings, waste paper or straw as disposed of discarded wood and / or Halmmaterialien must be crushed to definable final grain sizes, which usually from dust to coarse chips rich. In particular, in the production of particle board two known shape different chips are known, namely a fine chip, which brings a uniform as possible dense surface and on the other a coarser chip for the middle layer of the chipboard.

As in Fig. 2 illustrated, the holes are preferably used for use Reibsiebe coming 32, 33 in both Reibsieben 32, 33 are preferably designed differently so that these passed break-crushed wood and / or Halmmmaterialfraktionen 91 so be wiped that arise from the shape of two different chips. In particular, has proven in this context when the hole diameter of a Reibsiebes 32 are preferably selected to be greater than in the other Reibsieb 33, so that the slower larger chips through the Reibsieb 32 in the outer wall 22 and the finer chips - preferably supported by a suction flow - Pass through the rubbing screen 33 in the inner wall 23 in the respective Reibsieb 32, 33 downstream storage space 42, 43.

The chips of the length of length passed through the rubbing sieves 32, 33 into downstream collecting chambers 42, 43 can be removed separately from the collecting chambers 42, 43 as secondary raw material 99 without or preferably with suction means 52, 53.

As far as the particle size - depending on the supplied disposed material 90 - has a significant influence on the technical properties of the secondary raw material 99 and therefore require the, in particular different, rubbing sieves 32, 33 reached feinf-crushed material fractions 92, 93 require a more differentiated particle size distribution, can an advantageous development of the crushing device 1 according to the invention the Reibsieben 32, 33 corresponding further, matched to defined particle sizes sieves, be downstream (not shown).

By the second crushing stage 20 according to the invention is designed as a double-walled housing 21, the outer and inner walls 22, 23 are each provided with Reibsieben 32, 33 for the passage of reibfein-comminuted material fractions 92, 93, a crushing device 1 with an advantageously significantly improved Material throughput for recovered secondary raw materials 99 are provided from disposed material 90.

A comminution device 1 designed for a preferably optimized material throughput was operated, for example, under the following conditions:

The electric motor 13 driving the impact tool 12 was operated in constant mode during normal operation. The one everyone Suction chambers 52 and 53 associated with plenum 42 and 43 were operated at a rated speed D52 and D53 of about 70%. The control flaps 72 and 73 arranged in each collecting space 42 and 43 have been adjusted such that the ratio of the volume flows v.sub.42 : v.sub.43 from the outer collecting space 42 to the inner collecting space 43 is less than 1, preferably approximately 2: 3.

In the event of changes or fluctuations in the entry of the material 90, the speed D52 and D53 of the suction means 52 and 53 was adapted to the fluctuation and / or emergency control in accordance with the desired volumetric flow ratio v̇ 42 << v̇ 43. Likewise, in the event of imminent blockage of the interior of the first housing 11 of the first crushing stage 10, the motor current of the electric motor 13 could be adjusted accordingly within the scope of an emergency control.

$$\underset{{\dot{V}}_{43}}{\overset{{\dot{V}}_{42}}{------}}=\underset{3}{\overset{2}{-----}}$$

Tests with two differently sized crushers A and B gave after FIG. 2 : <b> Table 1 </ b> Crushing device A Crushing device B Total volume flow: V̇ = 25,000 m ³ / h V̇ = 18,000 m ³ / h In space 42 before suction means 52: V̇ 42 = 10,400 m ³ / h V̇ 42 = 7,200 m ³ / h In the room 43 before suction means 53: V̇ 43 = 15,600 m ³ / h V̇ 43 = 10,800 m ³ / h Volume flow ratio: $$\underset{{\dot{V}}_{43}}{\overset{{\dot{V}}_{42}}{------}}=\underset{3}{\overset{2}{-----}}$$

$$\underset{{\dot{V}}_{43}}{\overset{{\dot{V}}_{42}}{------}}=\underset{3}{\overset{2}{-----}}$$

Depending on the application, different, esp. Changeable trained, rubbing sieves 32, 33 are used. In particular, preferably have proven that are designed as so-called. Conidur® screens, as these are offered by the German company HEIN, LEHMANN GmbH and which in particular have conical holes, wherein the passage direction is tilted, so that a scale-defining scale-like , rough surface supports the rubbing process.

In particular in the case of the friction sieve 32 on the inside of the outer wall 22 of the double-walled housing 21, an oblique position of the passage direction of the holes aligned against the typical direction of movement of impact-fractured material fractions 91 has proven successful, so that from the first comminution stage 10 towards the cover 24 of the second comminution stage 20 in FIG Air swirling circular impact-crushed material fractions 91 at the scale-like, rough surfaces of the Reibsiebe 32, 33 are crushed.

In contrast, the rubbing strainer 33 on the outside of the inner wall 23 of the double-walled housing 21, a direction of gravity directed alignment of the oblique position of the passage direction of the holes has proven.

Thus, in the ideal case, the impact-comminuted material fractions 91 are first propelled by the high-speed rotating impact tool 12 in one direction cover 24 rising air vortex on the first Reibsieb 32 on the inside of the outer wall 22 of the double-walled housing 21, then on the friction strips 62 on the lid 24th guided inward until they fall back into the first stage 10 in contact with the inner wall 23 of the double-walled housing 21 in the center due to gravity along the second Reibsiebes 33 - of course only as far as not worn down and through the Reibsiebe passed through as material fraction 92nd , 93.

List of Reference P1481:

• 1 crushing device
• 10 first crushing stage
• 11 housing
• 12 impact tool
• 13 electric motor
• 20 second crushing stage
• 21 housing (double-walled)
• 22 outer wall
• 23 inner wall
• 24 lids
• 25 room
• 32 rubbing screen
• 33 rubbing screen
• 42 collection room
• 43 collection room
• 50 feed channel
• 52 suction means
• 53 suction means
• 61 gap edges
• 62 reissists
• 72 control flap
• 73 control flap
• 90 material
• 91 material fraction
• 92 material fraction
• 93 material fraction
• 99 secondary raw material
• v̇ total volume flow
• v̇ 42 volumetric flow
• v̇ 43 volumetric flow
• P42 dynamic pressure
• P43 dynamic pressure
• D52 speed
• D53 speed

State of the art:

• EP 1 536 892 B1
• EP 1 721 674 B1
• WO 2010/057604 A1

Claims (16)

1. A grinding device (1) for recovering secondary raw materials (99) from disposed material (90), comprising a first grinding stage (10) having a feed channel (50) for feeding the disposed material (90) to a first housing (11) with a rotating impact tool (12) for grinding the disposed material (90) into an impact-shredded material fraction (91) and for generating an air vortex, which displaces the impact-shredded material fractions (91) from the first grinding stage (10) between the walls of a double-walled second housing (21) of a second grinding stage (20) which is provided downstream of the first grinding stage (10), wherein the double-walled housing (21) of the second grinding stage (20) is provided on the outer wall (22) with a first screen and on the inner wall (23) with a second screen, wherein material fractions (92, 93) frictionally comminuted in a corresponding manner pass through these screens into a collecting space (42, 43) downstream of the respective screen.
2. Grinding device (1) according to claim 1, characterized in that a first friction screen (32) is arranged on the double-walled housing (21) of the second grinding stage (20) on the inside of the outer wall (22) and a second friction screen (33) is arranged on the outside of the inner wall (23).
3. Grinding device (1) according to claim 1, characterized in that the inside of the first wall (11) of the first grinding stage (10) is provided with gap edges (61).
4. Grinding device (1) according to claim 1 or 2, characterized in that the screens of the inner wall (23) and the outer wall (22) have hole diameters of the same or different sizes.
5. Grinding device (1) according to one of the previous claims, characterized in that further screens are arranged downstream of the screens or the friction screens (32, 33) respectively.
6. Grinding device (1) according to one of claims 2, 4, 5, characterized in that the hole spacings in the friction screens (32, 33) are selected smaller in the circumferential direction of the double-walled housing (21) than in its longitudinal extension.
7. Grinding device (1) according to one of the previous claims, characterized in that friction strips (62) are arranged in the double-walled housing (21) of the second grinding stage (20), preferably on the cover (24) of the housing (21).
8. Grinding device (1) according to one of the previous claims, characterized in that a control flap (72, 73) throttling the volume flow (v42, v43) is arranged as adjusting device for the volume flow through the grinding device (1).
9. Grinding device (1) according to one of the previous claims, characterized in that the transport of the material fractions (91, 92, 93) through the grinding device (1) is assisted by a suction airflow.
10. Grinding device (1) according to one of the previous claims, characterized in that at least the second collecting space (43) is assigned a suction means (53) which promotes the material throughput.
11. Method for controlling a grinding device (1) according to one of the previous claims, characterized by the use of adjusting devices, by means of which the ratio of the volume flows (v42, v43) in the collecting spaces (42, 43) can be adjusted such that the volume flow (v43) of frictionally comminuted material fractions (93) in the collecting space (43) behind the inner wall (23) of the housing (21) of the second grinding stage (20) is greater than the volume flow (v42) of frictionally comminuted material fractions (92) in the collecting space (42) behind the outer wall (22) of the housing (21) of the second grinding stage (20).
12. Method according to claim 11, characterized in that the rotational speed (D52, D53) of at least one suction means (72, 73) can be varied as an adjusting device for the volume flow ratio (v42<<v43).
13. Method according to claim 11 or 12, characterized in that a control flap (72, 73) throttling the volume flow (v42, v43) is arranged as adjusting device for the volume flow ratio (v42<<v43) in at least one collecting space (42, 43).
14. Method according to one of claims 11 to 13, characterized in that the motor current of an electric motor (13) driving the impact tool (12) can be adapted, in particular in the event of changes or fluctuations in the material input and/or in the event of impending clogging in the first housing (11) of the first grinding stage (10).
15. Method according to one of the claims 11 to 13, characterized in that the ratio of the volume flows (v42:v43) from the outer collecting space (42) to the inner collecting space (43) is less than 1, in particular 2:3.
16. Method according to one of claims 11 to 14, characterized in that the volume flow ratio (v42<<v43) is indirectly monitored by measuring the dynamic pressures (P42, P43) in the collecting chambers (42, 43), wherein a correctly set volume flow ratio (v42<<v43) is characterized in that the dynamic pressure (P43) in the inner collecting space (43) behind the inner wall (23) of the housing (21) of the second grinding stage (20) is smaller than the dynamic pressure (P42) in the outer collecting space (42) behind the outer wall (22) of the housing (21) of the second grinding stage (20).

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