EP2145988B1 - Axial fractioner - Google Patents

Description

The present invention relates to an axial fractionator and a method for the fractionated separation of shives and short fibers from fiber flakes and their use.

There are already efficient technologies for growing and harvesting natural fibers. However, the processing of straw and the processing of the resulting products still need to be improved in order to provide sufficient quantities and consistent qualities for the processing industry (vehicle, construction industry, etc.), thus ensuring successful plant operation and economic production of natural fibers To enable shunting.

For the classification and fractionation of short-fiber shives mixtures in fiber production plants, the typical machines known from the classifying technique are used in a wide variety of combinations, although machines have also been used which are normally used in the cotton industry.

The DE 199 18 166 B4 describes a device for obtaining short fibers, in which an axial fractionator for fractionally separating shives and short fibers of fiber flakes is used.

In the DE 198 35 771 A1 For example, a method and an apparatus for obtaining a fiber material suitable as a raw material for insulating purposes or for nonwoven production or as a filler or upholstery fabric and use of the fiber material are described.

The DE 196 26 557 A1 discloses a process for obtaining wool-like fine fiber pulps from vegetable raw materials using a knife mill with a rapidly rotating roller. This leads to a wool-like consistency of the fiber bundle. A fractional separation of shives and fibers is not described.

Known machines that are used in the natural fiber industry for the preparation of short fiber shives mixture, mainly used for the classification of the shives. However, there is still no satisfactory solution for additional purification or recovery of the short fibers that are in the mixture.

The typical classifying machines for shives in dry fiber production include on the one hand, the screening drum, with which the shives can be classified into different fractions, and a variety of vibrating screens. However, it is not possible to recover short fibers with residual shives content below 6% by mass with the help of these machines. Another widespread machine is the so-called Duvex by van Dommele (http://www.vandommele.be/htmlENG/shivecleaning.html). This machine comes from the cotton industry, but is very cost-intensive for the natural fiber products produced from domestic plants and especially for the task of separating shives, fibers and dust and classifying the shives in a machine not suitable. This is due to the fact that with the Duvex, depending on the design of the machine, either only clean fibers or fractionate shives only. Both tasks can not be realized with a single machine. This would only be possible in a machine group consisting of two machines connected in series. The Duvex works roughly like a classic screen drum. In addition, however, the Duvex still has rotating fingers that actively intervene in the material to be cleaned while destroying the shives (grind). The fine particles can then pass unhindered through the sieve bottom. By grinding the shives, no fractionation is possible because all shives have the same particle size.

The object of the present invention is the fractionated separation of fibers and shives from fiber flakes and dust removal and fractionation of the shives.

The object of the invention is achieved by an axial fractionator with the features of the main claim. Advantageous embodiments of the invention Axialfraktionierers are characterized in the dependent claims.

The object of the invention is thus achieved by an axial fractionator, comprising at least one elongated housing, wherein at a first lateral end of the housing a filling opening and at a second lateral end of the housing is arranged an outlet, at least one discharge at the bottom of the housing and at least one auger arranged in the housing, which causes a transport of the fiber flakes on the discharges.

The screw conveyor in the sense of the invention consists of a shaft on which devices, such as paddles, are arranged for transporting fiber flakes over the discharges.

The housing of the Axialfraktionierers invention consists of two parts, a lower part, where there is at least one discharge, and an upper part, which is removable for cleaning purposes.

The upper part of the housing may be made of a transparent material, such as glass or plastic or have flaps or (visual) window, which allow observation of the processes inside the Axialfraktionierers.

In addition, the Axialfraktionierer contain an exhaust gas, with which one can make dedusting.

With the axial fractionator according to the invention a fiber cleaning is possible in which both shives and short fibers can be obtained. Short fibers (short fibers) according to the invention are fibers with a length of about 5 to 70 mm.

The recovery of short fibers from the mixture with a residual shives content in the fiber of ≤ 6% and residual fiber content in the shives of ≤ 1% can be achieved with the axial fractionator according to the invention.

The fractionation of fibers and shives is only possible by the special choice of paddle tools (tool shape) and tool speed.

So that the fibers can be recovered from the mixture, it is necessary to classify the shives, which are not bound to the fiber flakes, and to fractionate them into different particle sizes.

For this purpose, perforated screens with different hole sizes are preferably arranged above the discharges.

So that the shives and short fibers can be classified, ie separated and sorted according to their size, the perforated sieves have a different hole size. The perforated screens are arranged such that the loaded with shives and short fibers fiber flakes are first passed through perforated screens with a small hole size and then on perforated screens whose hole size is getting bigger.

The perforated sieves form the bottom or at least part of the bottom of the housing and at the same time cover the discharges.

The auger is driven by a motor, wherein the speed of rotation of the auger is adjustable.

In a preferred embodiment of the invention, the screw conveyor is a paddle screw in which paddles are mounted on a shaft. The shaft is driven by a motor.

The paddle screw preferably has crescent-shaped paddles. By means of this paddle screw, the fiber flakes loaded with shives and short fibers are guided axially along the housing wall.

In a preferred embodiment of the invention, a plurality of axial fractionators can be coupled to one another. For this purpose, a housing of a first Axialfraktionierers is coupled to the housing of a second Axialfraktionierers to an existing Axialfraktionierer consisting of two housings.

In the coupling, the outlet of the first axial fractionator is preferably coupled in each case to the filling opening of the second axial fractionator.

Coupling has not only the advantage that the whole machine is easier to transport, since it consists of several parts, it is also possible by such a construction to perform the separation and classification of the shives and short fibers in two stages. Here, the paddle screw in the two Axialfraktionierern with a different speed can be operated and different paddle shapes can be used.

The screw conveyor in the first axial fractionator preferably has sickle paddles or double-needle paddles and full paddles in the second axial fractionator.

In order for the fibers to be recovered from the mixture, it is necessary to classify the shives which are not bound to the fiber flakes and to fractionate them into two particle sizes. This makes up about 60% by mass of the starting mixture. This is done in the first stage in the first Axialfaktionsierer. The material is guided axially by a kind of paddle screw, wherein the bottom of the vessel (trough bottom) is provided with two different perforated sieves. By the paddle or also the shape of the paddles, which are similar to a sickle, for example, the material is guided up to a certain point on the paddle along the curved screen wall up to a _critical angle φ crit. In this point it comes to the flow of the bulk material on the paddle. This means that the bulk material, which does not yet flow over the paddles, moves laterally in the axial direction and then rolls down on the sieve bottom. Material which can not roll over the paddles in the short time is moved over the paddle screw, tangentially falls back onto the curved sieve bottom and rolls over it again. The grains can align and have time to move through the sieve opening. The material that is still on the sieve bottom is caught by the next paddle and the procedure is repeated, so that each time the shaft rotates, four paddles loosen up the material and clear the sieve surface.

Further, the material is axially displaced with the shaft revolution. This is adjustable by the pitch of the paddles, with the individual paddles not overlapping. They have a negative degree of coverage.

The shaft angular velocity ω is preferably 3 to 10.5 s ^-1 in the first axial fractionator (first stage) and 10 to 26.2 s ^-1 in the second axial fractionator (second stage).

mit f = AntriebsfrequenzThe shaft angular velocity ω can be calculated according to the following formula (formula I): $$\omega =2\cdot \pi \cdot f$$

with f = drive frequency

The circular path velocity v in the first axial fractionator (first stage) is preferably at most 2.7 m / s and in the second axial fractionator (second stage) at most 6.5 m / s.

mit

f

= Antriebsfrequenz

r

= Paddelaußenradius

The orbit velocity v can be calculated according to the following formula (formula II): $$v=2\cdot \pi \cdot r\cdot f$$

With

f

= Drive frequency

r

= Paddle outer radius

At the speeds in the first axial fractionator (first stage), the flocs with the bound shives are not dissolved. This is then done in the second Axialfraktionierer (second stage).

The fiber flakes are accelerated by the paddle screw and it comes to a throwing motion. Upon reentry into the wave circle, the flakes are accelerated. Due to the mass inertia of the flakes and their air resistance, the flakes are partially torn apart. By additional friction on the sieve bottom, the flakes are then finally pulled apart and the shives are separated from the fibers.

In addition, the paddle on the shaft of the paddle screw in the first stage to an axial movement depending on the slope of the paddle.

The pitch angle α of the paddles according to the invention is in a range of 60 ° to 85 °. The pitch angle α results from the selected pitch G and the rotor diameter r according to the formula III. $$\mathit{tg\alpha }=\frac{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="imgf0006.png"\; state="\{\{state\}\}">G</figure-callout>}}{2\cdot \pi \cdot r}$$

Furthermore, an embodiment of the Axialfraktionierers according to the invention, in which two augers are mounted one behind the other in a housing, which can be operated by at different shaft speeds and are equipped with different paddles.

Furthermore, the object of the present invention is achieved by a method using at least one Axialfraktionierers invention, in which separating shives and / or short fibers from the fiber flakes and classified the shives and / or short fibers.

Shives and short fibers are light. They are firmly interlocked because of their surface.

Preferably, the shives and / or short fibers are separated from the fiber flakes with a paddle screw with sickle paddles or double-needle paddles, so that the shives and / or short fibers can pass through the perforated sieves. Through the paddles of the paddle screw, the fiber flakes are pulled apart, so that the shives fall out of the fiber flakes.

The separated shives and short fibers are preferably classified by perforated sieves with different hole sizes located above the discharges.

The underside of the Axialfraktionierers is V-shaped in cross section; only the sieve bottom is U-shaped, so that the paddle screw leads the fiber flakes directly over the underside. On the bottom of the Axialfraktionierers are the discharges, which are covered with perforated sieves. The hole size of the perforated sieves is chosen so that the shives fall into the first discharges and the short fibers in the last discharges, which for this purpose have perforated sieves with larger holes. The shives and short fibers obtained in this way can be used for a wide variety of applications.

Mixtures of short fibers and shives are suitable, for example, as litter for horse keeping and for the production of furniture panels. The fibers obtained in the last discharge are suitable, for example, for the production of fiber composites.

In order to obtain the desired classification results, the number of discharges and the perforated sieves used can be varied accordingly.

The process is preferably carried out in several stages, the fiber flakes passing through several axial fractionators. By using multiple axial fractionators coupled together, the separation process can be performed in multiple stages. In the individual stages / Axialfraktionierern different screw conveyors and / or different paddles can be used. The speed at which the screw conveyor rotates in the axial fractionator can also vary.

The screw conveyors are preferably operated at different speeds in the respective axial fractionators. The different speeds in the respective Axialfraktionierern lead to different results in the dissolution of the fiber flakes.

The shaft angular velocity ω is preferably set to 3 to 10.5 s ^-1 in the first axial fractionator and 10 to 26.2 s ^-1 in the second axial fractionator.

The circular path velocity v is preferably set to a maximum of 2.7 m / s in the first axial fractionator and to a maximum of 6.5 m / s in the second axial fractionator.

The pitch angle α of the paddle is set according to the invention to 60 ° to 85 °.

The Axialfraktionierer is filled to 10-40% with Good (shives-fiber mixture). In a preferred embodiment of the invention to fill the Axialfraktionierer to 10-25% with Good. If the axial fractionator is too full, The loosened shives are picked up again by the fiber flakes and do not fall on the perforated sieves above the discharges on the underside of the housing.

Furthermore, the object of the present invention is achieved by the use of at least one Axialfraktionierer invention for the production of shives and short fibers. By using the Axialfraktionierers invention, it is also possible to utilize the by-products of fiber pulping plants. One of these byproducts is a shives-fiber mixture, which is obtained in fiber-cleaning plants.

The shives and short fibers obtained with the axial fractionator according to the invention can be used as litter in animal husbandry, for the production of furniture panels and as composite materials.

Figur 1

eine dreidimensionale Ansicht von zwei gekoppelten Axialfraktionierern,

Figur 2

eine zweidimensionale Ansicht von zwei gekoppelten Axialfraktionierern,

Figur 3

eine Skizze der ersten Stufe mit Sichelpaddeln und Gutbelegung,

Figur 4

eine Skizze der Gutbewegung über ein Paddel in der ersten Stufe,

Figur 5

eine Skizze der Wurfbewegung und Verteilung der Absiebung über das Sieb,

Figur 6

eine dreidimensionale Darstellung der Welle mit Sichelpaddeln,

Figur 7

eine dreidimensionale Darstellung der Welle mit Vollpaddeln,

Figur 8

ein Diagramm der Trennerfolge der ersten Stufe und

Figur 9

ein Diagramm mit einem Vergleich zweier Klassiertechnologien.

In the following the invention will be described in more detail by means of examples and figures. In detail shows

FIG. 1

a three-dimensional view of two coupled axial fractionators,

FIG. 2

a two-dimensional view of two coupled axial fractionators,

FIG. 3

a sketch of the first stage with sickle paddling and occupancy,

FIG. 4

a sketch of the good movement over a paddle in the first stage,

FIG. 5

a sketch of the throwing motion and distribution of the sieving over the sieve,

FIG. 6

a three-dimensional representation of the wave with sickle paddles,

FIG. 7

a three-dimensional representation of the wave with full paddling,

FIG. 8

a diagram of the separation sequence of the first stage and

FIG. 9

a diagram comparing two classification technologies.

The FIG. 1 shows two coupled Axialfraktionierer 1. The Axialfraktionierer 1 consist of a housing 2 with a filling opening 3 and an outlet. 4

Through the filling opening 3-1 of the first Axialfraktionierers 1-1 the Good 5 (shives-fiber mixture) is introduced into the Axialfraktionierer 1. In the first axial fractionator 1-1 (first stage), the material 5 is guided by a paddle screw 6 via the discharges 7 located at the bottom of the axial fractionator 1. From there, the material 5 can be led out through the outlet 4-1 of the first axial fractionator 1-1 or transferred through the filling opening 3-2 into a further axial fractionator 1-2. In the second axial fractionator 1-2, the material 5 is also conveyed by a paddle screw 6 via the discharges 7. Finally, the cleaned fibers are conveyed out of the axial fractionator 1 through the outlet 4-2.

For process monitoring are located on the top of Axialfraktionierers 1 flaps 8 or window 13, through which the material movement in Axialfraktionierer 1 can be observed.

The in the FIG. 1 shown Axialfraktionierer 1-1 and 1-2 have a suction nozzle 14 on the upper housing part, which serves for dedusting.

The FIG. 2 shows the material flow of the shives-fiber mixture by two coupled together Axialfraktionierer 1. Each of the illustrated Axialfraktionierer 1-1 and 1-2 has two discharges 7 for the separate removal of various shives and short fiber fractions (A - D). However, embodiments are also conceivable in which an axial fractionator 1 has only one or more than two discharges 7.

The in the FIGS. 1 and 2 illustrated cascade of two Axialfraktionierern 1 operates in two stages. In the first stage, the loose shives are separated and separated into two fractions. At the same time, the fiber flakes are indeed loosened, but not destroyed. In the loosening first shives, which are included in the flake, moved out and can be classified. In the second stage, the positive connection of the fibers by working tools, such as full paddle 10-2, which are also responsible for the material movement in the axial direction, dissolved.

The separation and classification of the shives is done by perforated sieves 9, which are located at the bottom of the housing 2 of the Axialfraktionierer 1. The perforated sieves 9 have different hole sizes, so that in the position A shives with a grain size of 0-3 mm in diameter, in the position B shives with a grain size of 3 to 8 mm in diameter and at the positions C and D shives and short fibers the fiber cleaning can be won. The cleaned fibers are then passed through the outlet 4-2 (position E) conveyed out of the Axialfraktionierer 1 and fed to a further utilization.

The paddle screws 6 in the Axialfraktionierern 1 are driven by a motor 12.

In the FIG. 3 the movement of the shives over a perforated screen 9 is shown. The amplitude of the shifter movement changes as a function of the shaft angular velocity ω and the pitch angle α (see FIG. 6 ) of the paddle 10. The sinusoidal function of the shifter movement S over the perforated screen 9 is represented by a trend line and its direction by an arrow.

The FIG. 4 shows a sketch of the material movement on the sickle paddle 10-1 the first stage or in a first Axialfraktionierer 1. By the sickle paddle 10-1 of the sieve bottom is cleared, but a part of the material 5 flows over the paddle 10 and falls back onto the sieve bottom , Here, the shives pass through the perforated sieve 9.

1. 1. Bewegung: Die Paddel 10 räumen das Material vom Siebboden. Dabei wandert ein Anteil des Schüttgutes über die Paddel 10 und kann sich somit auf dem frei geräumten Siebboden wieder ausrichten und die Lochsiebe 9 passieren.
2. 2. Bewegung: Die Paddel nehmen das Schüttgut bis zu einem Grenzwinkel φ mit. Dabei bewegt sich das Material über den Siebboden und passiert dabei teilweise die Lochsiebe 9. Ab dem Grenzwinkel φ fängt das Material seitlich entlang des Paddels 10 an zu fließen. Es führt eine axiale Bewegung aus. Anschließend fließt das Material auf dem Siebboden nach unten. Dabei haben die Partikel wieder genügend Zeit, sich auszurichten und somit die Lochsiebe 9 zu passieren.
3. 3. Bewegung: Die Paddel 10 nehmen das übrige Material, das weder über die Paddel (Bewegung 1) noch seitlich (Bewegung 2) entlang der Paddel 10 bewegt wurde, weiter mit und es kommt zu einem schrägen Wurf. Das Material fliegt über die Welle 11, fällt tangential gegen das Lochsieb 9 und rollt dann wieder auf dem Siebboden entlang. Dabei hat es Zeit, sich auszurichten und kann durch die Lochsiebe 9 fallen.

In summary one can say that in the first stage three movements take place:

1. 1st movement: The paddles 10 clear the material from the sieve bottom. In this case, a proportion of the bulk material migrates over the paddle 10 and can thus align again on the cleared screen bottom and pass through the perforated sieves 9.
2. 2. Movement: The paddles take the bulk material up to a limit angle φ. In this case, the material moves over the sieve bottom and thereby partially passes through the perforated sieves 9. From the limit angle φ, the material begins to flow laterally along the paddle 10. It leads one axial movement. Then the material flows down on the sieve bottom. The particles have enough time again to align themselves and thus pass through the perforated sieves 9.
3. 3. Movement: The paddles 10 continue to pick up the remaining material, which has not been moved along the paddle 10 via the paddles (movement 1) or laterally (movement 2), and an oblique throw occurs. The material flies over the shaft 11, falls tangentially against the perforated screen 9 and then rolls back along the sieve bottom. It has time to align and can fall through the perforated sieves 9.

The FIG. 5 shows a sketch of the throwing motion and the distribution of the screening of the Guts 5 on the perforated screens 9 in the second stage, or in one, to the first coupled second Axialfraktionierer 1-2.

First, only the not hooked to fibers or incorporated in fiber flakes formed by short fibers shovels are sieved and fractionated. For this purpose, sickle paddle 10-1 or double-needle paddle 10-3 are necessary. Only with this paddle form and with correspondingly low circular path velocities (maximum 2.7 m / s) is it possible to cut off the shives without the fiber flakes being dissolved and also fibers being screened off. The shives are selectively loosened by these paddles 10 gently. By sliding along the shives on the sickle edge and the overflow of the sickle flank from a certain critical angle φ only the shives are loosened and can thereby pass through the sieve openings ( FIG. 4 ).

The fiber flakes remain when using sickle paddles 10-1 and the selected low orbit speeds receive. In addition, the formation of fiber flakes under these process conditions is even deliberately and intentionally promoted to prevent premature deposition of the fibers.

If a single-stage axial fractionator 1 is used, it can only be divided into three fractions: 1. fine shives, 2. rough shives and 3. shives and short fibers.

If a two-stage axial fractionator 1 is used, in the second stage full paddles 10-2 are used as separation and transport tools at higher circular path speeds (10 to 26.2 m / s). Due to these paddles 10 and under these process conditions, there is no longer a sliding of the material flow over the screen surfaces, but the material is thrown deliberately, circulated and the floc structure is destroyed by the full paddles 10-2 (FIG. FIG. 5 ). In accordance with the selected screen perforation in this second stage, two different mixtures of shives with short fibers and short fibers purified via the outlet 4 can now be obtained at two discharges 7.

FIG. 6 shows a three-dimensional view of the paddle screw 6 of the Axialfraktionierers 1 with sickle paddles 10-1. The arrangement of the sickle paddle 10-1 is characterized by the distance F between two successive paddles 10, the pitch angle α, around which the paddles 10 are inclined, and the pitch G, the distance to the paddle 10 which repeatedly occurs in a row the paddle 10 offset by 90 °. Thus, a Paddelgang of four consecutive paddles 10 is formed. However, versions with only two or up to eight paddles 10 per gear can also be selected.

FIG. 7 shows three suitable paddles 10. These are a sickle paddle 10-1, a full paddle 10-2 and a double-needle paddle 10-3. Sickle paddle 10-1 and double-needle paddle 10-3 are used in a two-stage axial fractionator 1 in the first stage, full paddle 10-2 in the second stage.

FIG. 8 shows a diagram of the separation sequence of a (experimental) Axialfraktionierers 1 (or first stage). In the diagram, the separation function T _i between the fine and coarse shives (grain size d _i ) taking into account the mass flow m shown.

In detail, T (d) (V2) shows the separation function for roasted raw materials at a mass flow of 1200 kg / h; T (d) (V1a) the separation function for unroasted raw materials at a mass flow of 1200 kg / h and T (d) (V1b) the separation function for unroasted raw materials at a mass flow of 700 kg / h.

With this (experimental) Axialfraktionierer 1 an optimum mass flow of 700 kg / h shives-fiber mixture was achieved. This corresponds to a total mass flow of about 1500 kg / h starting material.

When cleaning the fibers in a coupled second axial fractionator 1 (second stage), it is necessary to operate at a higher angular velocity ω of the shaft 11. At an angular velocity .omega. Of 26 s.sup.- ¹ , optimum destruction of the flakes with the smallest fiber losses via the perforated sieves 9 has been determined. The required degree of purity of the short fibers of at least 6% by weight residual shives content is ensured up to a straw mass flow of approximately 2500 kg / h in unroasted or roasted hemp.

P1

Produkte ohne Nutzung einer Sieb- oder Fraktioniereinrichtung

P2

Produkte mit Axialfraktionierer

P3

Produkte mit Siebtrommel

Produkte aus Faser-Schäbengemisch (X1):

S1

Schäben fein

S2

Schäben grob

S+F

Schäben mit Faseranteil

F

Kurzfasern

Verteilung der Produkte (X2):

MP

Mischprodukt aus Fasern und Schäben

RP

Reinprodukt

In the in FIG. 9 The diagram shown shows how the yield of pure material (Y: percentage of the input material in percent) and thus of usable material can be increased by the use of an axial fractionator 1. The values resulting from the diagram are summarized in Table 1. Thus, the yield of pure material is increased by about 15% compared to the use of a sieve drum. Table 1 - yield of pure material: P1 in% P2 in% P3 in% S1 0 15.8 9.3 S2 0 17.8 13.3 S + F 40.4 4.4 17.8 F 0 2.4 0 MP 40.4 4.4 17.8 RP 0 36 22.6

P1

Products without the use of a sieving or fractionating device

P2

Products with axial fractionator

P3

Products with sieve drum

Products made of fiber-sheath mixture (X1):

S1

Shakers fine

S2

Shanks rough

S + F

Shives with fiber content

F

short fibers

Distribution of products (X2):

MP

Mixed product of fibers and shives

RP

pure product

LIST OF REFERENCE NUMBERS

1

Axialfraktionierer

1-1

first axial fractionator

1-2

second axial fractionator

2

casing

3

fill opening

3-1

Filling opening of the first Axialfraktionierers

3-2

Filling opening of the second Axialfraktionierers

4

outlet

4-1

Outlet of the first axial fractionator

4-2

Outlet of the second Axialfraktionierers

5

Well

6

paddle screw

7

host

8th

flap

9

strainer

10

paddle

10-1

sickle paddle

10-2

full paddle

10-3

Double sickle paddle

11

wave

12

engine

13

window

14

suction

Claims (15)

1. Axial fractionator (1) for the fractionated separation of shives and short fibres from fibre flocks, consisting of
   at least one elongate housing (2), wherein a filling opening (3) is arranged at a first lateral end of the housing (2) and an outlet (4) is arranged at a second lateral end of the housing (2),
   at least one discharge (7) on the underside of the housing (2), and
   at least one conveyor screw which is arranged in the housing (2) and which transports the fibre flocks over the discharge (7), wherein the conveyor screw is a paddle screw (6).
2. Axial fractionator (1) according to claim 1, characterised in that the paddle screw (6) comprises sickle-shaped paddles (10-1), full paddles (10-2) or double-sickle-shaped paddles (10-3) or combinations of said paddles.
3. Axial fractionator (1) according to one of claims 1 or 2, characterised in that the angle of inclination α of the paddles (10) lies in a range from 60° to 85°.
4. Axial fractionator (1) according to claim 1, characterised in that perforated screens (9) having different hole sizes are arranged over the discharges (7).
5. Axial fractionator (1) according to one of claims 1 to 4, characterised in that a plurality of axial fractionators (1) can be coupled to one another.
6. Axial fractionator (1) according to claim 5, characterised in that in each case the outlet (4-1) of the first axial fractionator (1-1) can be coupled to the filling opening (3) of the following axial fractionator (1).
7. Axial fractionator (1) according to claim 5 or 6, characterised in that the conveyor screw in the first axial fractionator (1-1) comprises sickle-shaped paddles (10-1) or double-sickle-shaped paddles (10-3) and in the second axial fractionator (1-2) comprises full paddles (10-2).
8. Axial fractionator (1) according to one of claims 5 to 7, characterised in that the shaft angular speed ω in the first axial fractionator (1-1) is 3 to 10.5 s^-1 and in the second axial fractionator (1-2) is 10 to 26.2 s^-1, and in that the orbital speed in the first axial fractionator (1-1) is at most 2.7 m/s and in the second axial fractionator (1-2) is at most 6.5 m/s.
9. Method for the fractionated separation of shives and short fibres from fibre flocks using at least one axial fractionator (1) according to one of the preceding claims, characterised in that
   shives and/or short fibres are separated from the fibre flocks, and
   the shives and/or short fibres are classified.
10. Method according to claim 9, characterised in that the shives and/or short fibres are unmixed from the fibre flocks by a paddle screw (6) comprising sickle-shaped paddles (10-1) or double-sickle-shaped paddles (10-3).
11. Method according to claim 10, characterised in that the angle of inclination α of the paddles is set to 60° to 85°.
12. Method according to claim 9 or 10, characterised in that the separated shives and short fibres are classified by perforated screens (9) having different hole sizes which are located over the discharges (7).
13. Method according to one of claims 9 to 12, characterised in that the method is carried out in a plurality of stages, wherein the fibre flocks pass through a plurality of axial fractionators (1).
14. Method according to one of claims 9 to 13, characterised in that the shaft angular speed ω in the first axial fractionator (1-1) is set to 3 to 10.5 s^-1 and in the second axial fractionator (1-2) is set to 10 to 26.2 s^-1, and in that the orbital speed v in the first axial fractionator (1-1) is set to at most 2.7 m/s and in the second axial fractionator (1-2) is set to at most 6.5 m/s.
15. Use of at least one axial fractionator (1) according to one of claims 1 to 8 to obtain shives and short fibres.

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