CN107396629B

CN107396629B - Crushing apparatus and method of controlling crushing apparatus

Info

Publication number: CN107396629B
Application number: CN201680018053.3A
Authority: CN
Inventors: J·卡姆; H·森克
Original assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Current assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Priority date: 2015-02-03
Filing date: 2016-02-03
Publication date: 2020-03-27
Anticipated expiration: 2036-02-03
Also published as: EP3253493A1; CN107396629A; DE102015101530A1; WO2016124618A1; EP3253493B1

Abstract

The invention relates to a comminution apparatus for recovering secondary raw material (99) from waste material, comprising: a first comminution stage having a feed channel for feeding waste material to a first housing having rotating impact means for comminuting the waste material into impact comminuted material portions and generating air vortices which carry the impact comminuted material portions from the first comminution stage (10) to between two walls of a double-walled second housing (21) of a second comminution stage, wherein the double-walled housing (21) of the second comminution stage is provided with a first screen at an outer wall (22) and a second screen at an inner wall through which the respective finely comminuted material portions pass to a collection chamber downstream of the respective screens. The throughput and the throughput through the screen arranged at the double-walled housing in the second comminution stage are advantageously increased. Example variants with different particle size distributions are obtained with different sieve arrangements.

Description

Crushing apparatus and method of controlling crushing apparatus

Technical Field

The present invention relates to a crushing plant for recovering secondary raw material from waste material and a method of controlling such a crushing plant.

Secondary raw material generally refers to raw material obtained from waste material by reprocessing (recycling). It is used as raw material for new products and is thereby distinguished from the original (obtained from nature) raw material. The invention also relates to materials which are used in a stepwise or repeated manner for a second or repeated number of times within the scope of raw material economy. The use of secondary raw materials protects beneficial natural resources and contributes to sustainable development.

Waste material can in the context of the present invention be understood in particular as composite material, such as occurs for example in the recycling-reprocessing of electrical and electronic devices or electrical and electronic components, as recycled individual material or as recycled mixed material from ferrous metals, non-ferrous metals, fibre composite materials or other synthetic materials (plastics) and/or as wood parts and/or stem parts, such as old or recycled wood, debarked logs, leftover wood pieces residues or other wood residues, such as in particular chips, waste paper or straw, and as material parts from other coarse comminution processes upstream in the recycling industry or residues from combustion processes.

Background

In order to industrially recover secondary raw materials from waste materials, various pulverizing apparatuses are known.

For example, reference is made here to comminution apparatuses described in EP 1536892B 1, EP 1721674B 1 or WO2010/057604a1, which apparatuses each comprise a first comminution stage with impact tools rotating in a cylindrical housing, the feed channel for the waste material being guided to a central region of the impact tools, wherein the impact tools rotate at a high rotational speed and thereby generate high-speed radial air vortices which impact the comminuted material fraction in the first comminution stage along openings constructed from the cylindrical housing in order to discharge the sufficiently comminuted material fraction into a collection chamber.

The comminution apparatuses known from the prior art have the disadvantage that the throughput of material is limited by the outlet opening in the housing.

Disclosure of Invention

Starting from this, the object of the present invention is to provide a comminution apparatus for recovering secondary raw materials from waste material, which is improved in particular with regard to the throughput of material, and a method for controlling the comminution apparatus. In a development of the invention, the apparatus and the method are intended in particular for generating dust from waste material.

According to the invention, this object is achieved by a comminution apparatus having the features of claim 1 and by a control method having the features of claim 10.

The solution of a comminution apparatus for recovering secondary raw material from waste material mainly comprises a first comminution stage with a feed channel for feeding the waste material to a first housing with a rotating impact tool for comminuting the waste material into impact comminuted material portions and generating air vortices which bring the impact comminuted material portions from the first comminution stage between two walls of a double-walled second housing of a second comminution stage downstream of the first comminution stage, wherein the double-walled housing of the second comminution stage 20 is provided at an outer wall with a first screen and at an inner wall with a second screen, wherein respective finely comminuted material portions pass through the screens into a collection chamber located downstream of the respective screens.

Preferably, a first friction screen is arranged on the inner side of the outer wall at the double-walled housing of the second comminution stage and a second friction screen is arranged on the outer side of the inner wall.

By the second comminution stage being configured according to the invention as a double-walled housing, the walls of which are each provided with a screen for the respective finely comminuted material portion to pass through, a comminution apparatus with an advantageously significantly increased material throughput of secondary raw material recovered from the waste material can be provided.

In particular, it is preferred here to make use of the air turbulence in order to cause the material to be comminuted to rub against itself and/or against a friction element or friction screen for the comminution.

Advantageous configurations and modifications which can be used individually or in combination with one another are the subject matter of the dependent claims.

In the setting of the comminution apparatus it is thus preferred that the inner side of the first wall of the first comminution stage is provided with a gap edge which continues to promote impact comminution of the waste material as this material is centrifugally thrown against the gap edge by the impact tool.

The use of a friction screen with the same size of the pore size in both screens has proven effective in the design of the comminution apparatus in the sense that a single material is used as waste material and/or that a secondary raw material with the same distribution of particle sizes should be obtained.

In the case of the use of the mixed material as a waste material in contrast and/or in the case of secondary raw materials which should be obtained with a different distribution of particle sizes (whether obtained from a single material or from mixed materials), it has proven effective to use friction screens with pore sizes of different sizes in alternative designs of comminution apparatuses, wherein the pore size of one friction screen is preferably selected to be larger than the pore size in the other friction screen.

In both cases, the effectiveness of the friction screen has been particularly proven, the friction screen preferably being designed as a so-called friction screen

Sieves, like those provided by HEIN, LEHMANN ltd. As is well known in the art,

the screen is manufactured according to a special method which enables the finest holes to be made in the plate thickness, which can be several times the hole diameter. Advantageously, the first and/or second electrode means,

the screen has in particular conical holes, in which the direction of passage is arranged obliquely, so that a flake-like, rough surface defining the particle size supports the rubbing process.

In an advantageous variant of the comminution apparatus according to the invention, further sieves matching the defined particle size corresponding to the friction sieve can be downstream in respect of the particle size-depending on the fed waste material-having a major influence on the technical properties of the secondary raw material and thus the particle size distribution of the finely ground material fraction reached by the friction sieve that needs to be further differentiated.

In order to also be able to recover finely comminuted fibrous material fractions having a defined fiber length, the spacing between the holes in the friction screen is preferably smaller in the circumferential direction of the double-walled housing than in its longitudinal extension. In other words: in the case of a typical direction of movement of the impact-comminuted material portion in the longitudinal direction of extension and thus in the direction of movement of the impact-comminuted material portion, which is encountered with a larger hole spacing than the hole spacing encountered in the transverse direction of extension, there is the advantage that the holes in the friction screen exert a friction effect on the longitudinal fibres with a sufficient spacing between one another.

In a further arrangement of the comminution apparatus it is preferred that when the cover of the double-walled housing of the second comminution stage is provided with a grating strip, the grating strip further promotes the frictional comminution of the comminuted material portion as it passes through the grating strip.

In a further embodiment of the comminution apparatus, it is preferred that the throughput of the material portion through the apparatus, in particular the finely comminuted material portion, is supported by the suction air flow.

In this case, it has proven particularly effective if the suction device which promotes the throughput of material belongs at least to the second collection chamber.

The invention also relates to a method of controlling a comminution apparatus as described above, characterized by an adjusting device, by means of which the proportional relationship of the volume flows in the collecting chamber can be adjusted such that the volume flow of the finely comminuted material fraction in the collecting chamber behind the inner wall of the housing of the second comminution stage is greater than the volume flow of the finely comminuted material fraction in the collecting chamber behind the outer wall of the housing of the second comminution stage.

The first modification of the method is preferably characterized in that the number of revolutions of the at least one suction device is variable as a means of regulating the volume flow ratio.

The second variant of the method is preferably characterized in that a control valve which reduces (throttles) the volume flow is arranged in the at least one collecting chamber as a means of regulating the volume flow proportional relationship.

The third variant of the invention is preferably characterized in that the motor current of the motor driving the impact tool is adaptable, in particular when the material charge changes or fluctuates and/or when there is a threat of clogging in the first housing of the first comminution stage.

In the comminution apparatus according to the invention, a volume flow ratio relationship has proven particularly effective in which the ratio of the volume flow of the outer collecting chamber to the volume flow of the inner collecting chamber is less than 1, preferably particularly 2: 3.

Finally, a variant of the method is characterized in that the volume flow ratio is monitored indirectly by measuring the stagnation pressure in the collection chambers, wherein a correctly adjusted volume flow ratio is characterized in that the stagnation pressure in the inner collection chamber behind the inner wall of the housing of the second comminution stage is smaller than the stagnation pressure in the outer collection chamber behind the outer wall of the housing of the second comminution stage.

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

Composite materials, such as, for example, those that occur when electrical and electronic equipment or electrical components are recycled for reprocessing; and/or

Recycled single materials or recycled mixed materials from ferrous metals, non-ferrous metals, fiber composites or other synthetic materials (plastics); and/or

Wood parts and/or stem parts, such as old or recycled wood, debarked logs, leftover wood pieces remains or other wood remains, such as in particular chips, waste paper or wheat straw; and/or

Material from other coarse grinding processes upstream in the recycling industry or residues from combustion processes.

The invention can likewise be used in particular for producing or preparing alternative fuels which can preferably be burnt in a dust burner after classification (device) or screening (device). The use as an additional combustion agent in a combustion appliance is also conceivable.

Drawings

These and other features and advantages of the invention will be further explained below on the basis of two comminution apparatuses for recovering secondary raw material from waste material, which are shown by way of example in the drawings, to which the invention is not, however, restricted.

The figures show schematically:

FIG. 1 is a first embodiment of a comminution apparatus for recovering secondary raw material, in particular particle sizes of the same particle size distribution, for example from waste fibre composite material; and

fig. 2 is a second embodiment of a comminution apparatus for recovering secondary raw material, in particular particle sizes of different particle size distribution, for example from waste wood and/or stem material.

In the following description of the preferred embodiments, like reference numerals refer to like parts.

Detailed Description

In fig. 1 and 2, each shows a crushing plant 1 for recovering secondary raw material 99 from waste material 90.

It can be observed that the first comminution stage 10 is effected in the lower region of the comminution apparatus 1. The waste material 90 fed to this first comminution stage 10 via the feed channel 50 is here comminuted by a percussion tool 12 which is configured in a known manner, for example as a rotor blade. The impact tool 12 rotating in the first housing 11, which is configured, for example, as a cylinder or as a hexagon, an octagon or another polygon, is preferably dimensioned such that a radial air vortex is generated depending on the density of the fed material 90 and thus a sieving effect is produced for the impact-comminuted material portion 91, the impact-comminuted material portion 91 which has already undergone sufficient impact comminution being centrifugally thrown at high speed into the second comminution stage 20 arranged above the first comminution stage 10.

For this purpose, the impact tool 12 may be equipped with a shovel (bucket) (not shown) that promotes the above-mentioned sieving action.

When the inner side of the housing 11 of the first comminution stage 10 is provided with a gap edge 61 as shown, impact comminution of the waste material 90 can be further promoted when the waste material 90 is centrifugally thrown against the gap (slit) edge 61 and is cleaved (cracked) by the impact tool 12 rotating in the first comminution stage 10.

The housing 21 of the second comminution stage 20 is constructed according to the invention as a double-walled housing 21, the impact comminuted material fraction 91 being thrown centrifugally between the outer wall 22 and the inner wall 23 of which housing and which outer and inner walls are provided with a

friction screen

32, 33, respectively, for passing the respective finely comminuted

material fraction

92, 93 into a collection chamber 42, 43 located downstream of the

respective friction screen

32, 33. The second comminution stage 20 is thus effected by grinding the previously impact-comminuted material fraction 91 not only at the roughened inner side of the outer wall 22 of the double-walled housing 21 but also at the roughened outer side of the inner wall 23 of the double-walled housing 21. The holding of the two

friction screens

32, 33 advantageously significantly improves the material throughput of the secondary raw material 99 recovered from the waste material 90. The double-walled housing 21 can be of cylindrical or hexagonal, octagonal or other polygonal configuration similar to or different from the first housing 11.

In order that the impact crushed material portions 91 do not leave above the outer and

inner walls

22, 23, they are preferably covered with a cover 24, whereby a chamber 25 for the impact crushed material portions 91 to be abraded in the second crushing stage 20 is delimited by the outer and

inner walls

22, 23 and the cover 24. When-as also indicated-the cover 24 of the double-walled housing 21 of the second comminution stage 20 is provided with a grating 62, the frictional comminution of the impact-comminuted material portions 91 is further promoted when these material portions 91 pass the grating.

In particular, the transport of the

material portions

91, 92, 93 can take place in purely mechanically generated air vortices and/or with the aid of suction technology additionally supported by the comminution apparatus 1.

In the last-mentioned arrangement, it has proven particularly effective to distribute the suction devices 53, which promote the throughput of material, to both collection chambers 42, 43 or to at least one collection chamber 42 or 43.

This is preferably designed such that fresh air-or (as long as the waste material needs to be dried) dry air or hot air-is also sucked in via the feed channel 50. Of course, the air in the feed channel 50 may also be provided by alternative or additional means. In any case, however, it has proven to be effective for the housing 11 to be preferably constructed closed in the region of the first comminution stage (first comminution stage) 10, so that no air can escape and the suction air flow is reduced in the direction of the second comminution stage (second comminution stage) 20.

By means of the air vortex which is always generated at least mechanically by means of the impact tool 12, the impact-comminuted material fraction 91 from the first comminution stage 10 is not only centrifugally thrown upwards into the second comminution stage 20, but additionally rotates in a circular manner in the air vortex.

The required air flow through the friction screens 32, 33 is preferably achieved by means of a control method which is characterized by a regulating device, by means of which the volume flow is achieved

Is adjustable. Particularly preferably, the volume flow rate proportional relationship

Can be adjusted such that the volume flow of the finely comminuted material fraction 93 in the collecting chamber 43 after the inner wall 23 of the housing 21 of the second comminution stage 20 in the flow direction

Greater than the volume flow of the finely divided material portion 92 in the collecting chamber 42 behind the outer wall 22 of the housing 21

Here, the pressure is adjusted to P₄₂>>P₄₃Which can thus be used as a volumetric flow rate proportional relationship

Is indicated. Because of the pressure P to the volume flow

Can be measured more easily, in a modification of the comminution apparatus it is preferred that the volume flow ratio is proportional

Indirectly by measuring the pressure P42, P43 in the collection chamber 42, 43, wherein the volume flow proportional relationship is correctly adjusted

Is characterized in that the pressure P43 in the inner collecting chamber 43 behind the inner wall 23 of the housing 21 of the second comminution stage 20 in the flow direction is smaller than the pressure P42 in the outer collecting chamber 42 behind the outer wall 22 of the housing 21 of the second comminution stage 20 in the flow direction. Here primarily with regard to stagnation pressure conditions.

A further variant of the method is preferably characterized in that the volume flow is

Or volume flow rate proportional relation

The number of revolutions D52 and/or D53 of the at least one

suction device

52, 53 is variable.

The second variant of the method is preferably characterized in that the volume flow is

Or volume flow rate proportional relation

In at least one collecting chamber 42, 43, a reducing (throttling) volume flow is arranged

And control

valves

72, 73.

The third variant of the invention is preferably characterized in that the motor current of the electric motor 13 driving the impact tool 12 is adaptable, in particular when the material charge changes or fluctuates and/or when there is a threat of blockage in the first housing 11 of the first comminution stage 10.

In the comminution apparatus according to the invention, a particular volume flow ratio relationship has proven effective in which the volume flow is determinedIn the case of the proportional relationship, the proportional relationship between the volume flow rate of the outer collection chamber 42 and the volume flow rate of the inner collection chamber 43

Less than 1, preferably in particular 2: 3.

Fig. 1 shows a first embodiment of a comminution apparatus 1 for recovering secondary raw material 99 having a particle size or a particle size distribution from, for example, waste fibre composite material.

In particular, as a result of the increasing share of carbon fiber reinforced plastics in different branches of industry, more and more CFK products that are no longer useful are inevitably accumulated as waste, which must then also be recycled in the sense of product liability. The value of CFK materials is becoming increasingly important due to their widespread use in the aerospace industry, the automotive industry, the wind energy industry, and many other industries. Of particular importance here is the value of the carbon fibers, which have already been subjected to high energy consumption in order to produce them. When the development is carried out and a process is established which involves only as little fibre degradation as possible, this energy is retained at least in high proportions by means of high-value recycling. This is also a prerequisite for the properties of the fibres to be able to be used in second generation components and remain available. Furthermore, carbon fibers (again due to the very high cost of manufacture) are a relatively high-priced raw material. Thus, not only is there an ecological reason for recycling the fibre composite material, but it also relates to the reason that the use of recycled fibres is economically advantageous.

As shown in fig. 1, the holes of the friction screens 32, 33 preferably used are preferably configured in both friction screens 32, 33 in such a way that the broken-up fibre composite portions 91 passing at these holes are rubbed in such a way that as uniform as possible fibres of a defined length are produced, which is sufficient to enable the forces acting in the component to be transmitted again between the fibres and the matrix of envelopes after the recovered fibres have been further processed, for example into yarn or flat semifinished products.

In this case in particular, it has proven effective to design the hole spacing in the friction screens 32, 33 such that it has a greater spacing in the typical direction of movement of the impact-comminuted material portion 91, i.e. in the direction of the swirling flow of the flowing air, than in the direction extending transversely, so that the holes in the friction screens 32, 33 exert the effect of rubbing against the longitudinal fibers with sufficient spacing from one another, i.e. so that the comminuted fibrous material portion 92 with a defined fiber length enters the collection chamber 42.

The fibers of uniform length which pass through the friction screens 32, 33 to the collection chamber 42 arranged downstream in the flow direction can be fed as secondary raw material 99 with or without the suction device 52 to the central collection chamber.

Fig. 2 shows a second embodiment of a comminution apparatus 1 for recovering secondary raw material 99 with two different particle size distributions, for example from waste wood.

In industrial wood products industry, such as for example the manufacture of chipboards, granules or briquettes, it is inevitable to dispose of waste wood and/or stem material before it can be fed to so-called processing or use. For this purpose, the wood and/or stem material, which is accumulated as old or recycled wood, debarked logs, leftover wood pieces or other wood residues, in particular chips, as waste paper or straw, must be comminuted to a definable final particle size, which generally ranges from dust particles to coarse chips. In particular in the manufacture of particle board, it is known that two types of chips are required which differ in form and are a relatively fine chip which brings about a surface which is as uniform and compact as possible and a relatively coarse chip which is used in an intermediate position in the particle board.

As shown in fig. 2, the holes of the friction screens 32, 33 preferably used in the two

friction screens

32, 33 are preferably configured differently such that the wood and/or stem parts 91 breaking up the comminution passing at these holes are rubbed in such a way that two types of chips of different form are produced. In particular in this case it has proven effective when the pore size of one friction screen 32 is preferably selected to be larger than the pore size in the other friction screen 33, so that the slower coarser chips pass through the friction screen 32 in the outer wall 22, while the finer chips-preferably supported by the suction air flow-pass through the friction screen 33 in the inner wall 23 to the collection chamber 42, 43 downstream of the

respective friction screen

32, 33.

The chips of different lengths which pass through the friction screens 32, 33 to the collecting chambers 42, 43 arranged downstream can be discharged as secondary raw material 99 separately from the collecting chambers 42, 43, respectively, without or preferably by means of the

suction devices

52, 53.

In the case of a particle size distribution, which has a major influence on the technical properties of the secondary raw material 99, depending on the fed waste material 90, and therefore requires further differentiation of the finely divided

material fractions

92, 93 reached through in particular the different friction screens 32, 33, in an advantageous modification of the comminution apparatus 1 according to the invention, a respective further screen matching the defined particle size can be downstream (not shown) of the friction screens 32, 33.

By the second comminution stage 20 being configured according to the invention as a double-walled housing 21, the outer and

inner walls

22, 23 of which are provided with a

sieve

32, 33, respectively, for the passage of the respective finely

comminuted material fraction

92, 93, a comminution apparatus 1 can be provided which advantageously has a significantly increased throughput of secondary raw material 99 recovered from the waste material 90.

The comminution apparatus 1 designed for a preferred optimized throughput is operated, for example, under the following conditions:

the motor 13 that drives the impact tool 12 is operated in a rated operation state in the constant mode. The

suction devices

52 and 53 belonging to the respective collection chambers 42 and 43 are operated at a nominal speed of rotation D52 and D53 of about 70%. The

control valves

72 and 73 arranged in the respective collection chambers 42 and 43 are adjusted in such a way that the volume flow of the outer collection chamber 42 is proportional to the volume flow of the inner collection chamber 43

Less than 1, preferably about 2: 3.

In the event of a change or fluctuation in the charge of material 90, the rotational speeds D52 and D53 of

suction devices

52 and 53 are proportional to the volume flow rate which is to be achieved in an effort to achieve

Is adjusted forSurge regulation and/or emergency regulation. In the event of a risk of clogging of the inner chamber of the first housing 11 of the first comminution stage 10, the motor current of the electric motor 13 can likewise be adapted accordingly within the scope of emergency regulation.

The test results for two comminution apparatuses a and B of different size design are obtained from fig. 2:

TABLE 1

Depending on the application, different friction screens 32, 33, which are in particular designed to be replaceable, can be used. In particular, it has preferably proved that these configurations are so-called

The friction screen of the screen is effective, as is provided by HEIN, levhann limited, germany, and in particular a screen with conical holes, wherein the passage direction is obliquely arranged so that a flake-like (flake-like) rough surface of defined particle size supports the friction process.

In particular, at the friction screen 32 on the inside of the outer wall 22 of the double-walled housing 21, an inclined arrangement of the passage direction of the holes oriented opposite to the typical direction of movement of the impact-comminuted material portion 91 has proven effective, so that the impact-comminuted material portion 91 spiraling in the air vortex from the first comminution stage 10 towards the cover 24 of the second comminution stage 20 is ground at the scale-like, rough surface of the

friction screen

32, 33.

In contrast, an oblique orientation of the passage direction of the holes against gravity has proven effective at the friction screen 33 on the outside of the inner wall 23 of the double-walled housing 21.

Thereby, in the ideal case, the impact-comminuted material portion 91 is thrown by the impact tool 12 rotating at a high number of revolutions first along the first friction screen 32 on the inner side of the outer wall 22 of the double-walled housing 21 in an air vortex rising towards the cover 24 and then fed inwards at the friction strip 62 at the cover 24 until it falls again into the first stage 10 again, determined by gravity, along the second friction screen 33 upon contact with the inner wall of the double-walled housing 21 in the center, without doubt only if it has not been rubbed and passes through the friction screen as

material portions

92, 93.

List of reference numerals:

1 crushing plant

10 first comminution stage

11 casing

12 impact tool

13 electric motor

20 second comminution stage

21 casing (double-layer wall)

22 outer wall

23 inner wall

24 cover

25 chamber

32 friction screen

33 Friction sieve

42 collection chamber

43 collecting chamber

50 feed channel

52 suction device

53 suction device

61 gap edge

62 rubbing strip

72 control valve

73 control valve

90 material

91 material part

92 material part

93 material part

99 secondary raw material

Total volume flow

42 volume flow

43 volume flow rate

P42 stagnation pressure

P43 stagnation pressure

Number of revolutions of D52

D53 revolutions.

The prior art is as follows:

EP 1 536 892 B1

EP 1 721 674 B1

WO 2010/057604 A1。

Claims

1. comminution apparatus (1) for recovering secondary raw material (99) from waste material (90), comprising a first comminution stage (10) having a feed channel (50) for feeding waste material (90) to a first housing (11) having a rotating impact tool (12) for comminuting the waste material (90) into impact comminuted material portions (91) and generating air vortices that bring the impact comminuted material portions (91) from the first comminution stage (10) between two walls of a double-walled second housing (21) of a second comminution stage (20) downstream of the first comminution stage (10), wherein the double-walled second housing (21) of the second comminution stage (20) is provided with a first screen at an outer wall (22), and a second screen is arranged on the inner wall (23), wherein the respective finely divided material portions (92, 93) pass through the screens to a collection chamber (42, 43) downstream of the respective screen.

2. Comminution plant (1) according to claim 1, characterized in that at the double-walled second housing (21) of the second comminution stage (20) a first friction screen (32) is arranged on the inner side of the outer wall (22) and a second friction screen (33) is arranged on the outer side of the inner wall (23).

3. Comminution plant (1) according to claim 1, characterized in that the inner side of the first wall of the first comminution stage (10) is provided with a clearance edge (61).

4. Comminution plant (1) according to claim 1 or 2, characterized in that the sieve of the inner wall (23) and the sieve of the outer wall (22) have pore sizes of the same size or pore sizes of different sizes.

5. Comminution plant (1) according to claim 2, characterized in that a further screen is arranged after the first friction screen (32) and the second friction screen (33).

6. Comminution apparatus (1) as claimed in claim 2, characterized in that the hole spacing in the first friction screen (32) and the second friction screen (33) in the circumferential direction of the double-walled second housing (21) is selected to be smaller than the hole spacing in its longitudinal extension.

7. Comminution device (1) according to claim 1 or 2, characterized in that a grating strip (62) is arranged in the double-walled second housing (21) of the second comminution stage (20).

8. Comminution device (1) according to claim 7, characterized in that the rub strip (62) is at the cover (24) of the second housing (21).

9. Comminution device (1) according to claim 1 or 2, characterized in that as adjusting means for the volume flow through the comminution device (1) there are arranged reducing the volume flow of the finely comminuted material fraction (92) in the collection chamber (42) behind the outer wall of the second housing of the second comminution stage

And reducing the volume flow of a finely comminuted material fraction (93) in a collection chamber (43) behind the inner wall of the second housing of the second comminution stage

The control valve (73).

10. A comminution plant (1) as claimed in claim 2, characterized in that the transport through the material portion (91) of the comminution plant (1), through the material portion (92) of the first friction screen and through the material portion (93) of the second friction screen is supported by the suction air flow.

11. A comminution plant (1) as claimed in claim 1 or 2, characterized in that it further comprises a second collection chamber (43), to at least which second collection chamber (43) a suction device (53) promoting the throughput of material belongs.

12. A method of controlling a comminution plant (1) as claimed in one of the preceding claims, a first friction screen (32) being arranged on the inner side of the outer wall and a second friction screen (33) being arranged on the outer side of the inner wall, characterized by an adjusting device by means of which the volume flow in a collecting chamber (42) downstream of the first friction screen is adjusted

And a volume flow in a collection chamber (43) downstream of the second friction screen

Is adjustable so that the volume flow of the finely comminuted material fraction (93) in the collecting chamber (43) behind the inner wall (23) of the second housing (21) of the second comminution stage (20)

Greater than the volume flow of the finely comminuted material fraction (92) in the collection chamber (42) after the outer wall (22) of the second housing (21) of the second comminution stage (20)

13. The method of claim 12, characterized by being proportional to volume flow

The number of revolutions of the at least one suction device is variable.

14. The method of claim 12 or 13, characterized by being said volumetric flow proportional relationship

In the at least one collecting chamber, a control valve is arranged which reduces the volume flow.

15. The method as claimed in claim 12 or 13, characterized in that the motor current of the motor (13) driving the impact tool (12) is adaptable.

16. The method according to claim 12 or 13, characterized in that the volumetric flow of a collection chamber (42) behind the outer wall (22) of the second housing (21) of the second comminution stage (20) is proportional to the volumetric flow of a collection chamber (43) behind the inner wall (23) of the second housing (21) of the second comminution stage (20)

Less than 1.

17. The method according to claim 16, characterized in that the volumetric flow of the collection chamber (42) behind the outer wall (22) of the second housing (21) of the second comminution stage (20) is proportional to the volumetric flow of the collection chamber (43) behind the inner wall (23) of the second housing (21) of the second comminution stage (20)

Is 2: 3.

18. The method of claim 12 or 13, wherein the volumetric flow proportional relationship

Indirectly by measuring the stagnation pressure (P42) in a collection chamber (42) behind the outer wall (22) of the second housing (21) of the second comminution stage (20) and the stagnation pressure (P43) in a collection chamber (43) behind the inner wall (23) of the second housing (21) of the second comminution stage (20), wherein the volume flow proportional relationship which is correctly adjusted

Is characterized in that the stagnation pressure (P43) in the collection chamber (43) behind the inner wall (23) of the second housing (21) of the second comminution stage (20) is smaller than the stagnation pressure (P42) in the collection chamber (42) behind the outer wall (22) of the second housing (21) of the second comminution stage (20).

19. A method according to claim 12 or 13, characterized in that the motor current of the motor (13) driving the impact tool (12) is adaptable in the event of a change or fluctuation in the material feed and/or in the event of a risk of clogging in the first housing (11) of the first comminution stage (10).