EP1245724A2 - Pressure screen for cleaning paper pulp containing impurities and its use - Google Patents

Abstract

The pressure sorter is used to remove impurities from a paper fiber suspension (S) and has a housing (6) with at least two screens (1, 2). The screens (1, 2) are arranged in such a way that the paper fiber suspension (S) introduced into the housing through the inlet connector (3) can flow through them one after the other. In advantageous embodiments, the pressure sorter is equipped with fine slots, the size of these slots being approximately the same for both screens (1, 2). The pressure sorter is particularly suitable for the separation of fine contaminants.

Description

The invention relates to a pressure sorter according to the preamble of claim 1.

Pressure sorters are used in the processing of paper fiber suspensions, namely to process the fiber suspension in a wet sieving. To do this contains Such a pressure sorter has at least one sieve with a large number of openings is provided. The fibers contained in the suspension should pass through the openings step through it while rejecting the unwanted solid components on it and be routed out of the sorter. Pressure sorters can also be used Fiber fractionation are used in which the long fibers in the overflow and Pass the short fibers are enriched. As sorting openings are in the Usually round holes are used or slots. In most cases they are pressure sorters of the type considered here equipped with screen clearers that are close to the screen be moved past. As a result, the clogging of the Screen openings prevented.

It is known that the pressure sorters are basically both for the sorting of relatively coarse, as well as very fine contaminants. On the Such sorters are not only used for the respective purpose by choosing the sieves themselves, especially their sorting openings also by constructive design of the machine and choice of operating parameters. It has meanwhile been able to produce sieves with reasonable effort, the very fine ones Openings, e.g. Have slots in the range of tenths of a millimeter. This succeeds separating even very small impurities from the fibers. This positive in itself However, development has led to the sieves and thus also the Sorting machines were getting bigger. The number of stages, i.e. the number of pressure sorter to be passed from the paper fiber suspension in succession greater.

DE 197 02 044 C1 describes a vertical classifier for a fiber suspension known, which has two screen elements in a single machine. With this The material flow to be sorted first reaches the area of a flat one Prescreen, which is kept clear on the inlet side with a scraper. The Passing through this flat pre-screen is then inside a rotationally symmetrical screen basket passed through the openings of the accepted material passes through, so that the suspended paper fibers through this screen basket can get into the waste outlet. Such a sorter should then in particular are used when the fiber suspension supplied with a larger amount is mixed with coarse impurities. As is well known, that comes from the Waste paper reprocessing where the material comes directly from the pulper or after passage a cleaning device that removes only the coarsest contaminants comes. This well-known sorter is optimized for the separation of coarse Impurities. The free screen area is relatively small.

WO 00/58549 A1 shows a sorter with a vertical housing, in which there are two screen elements flowed through successively by the paper fiber suspension to be cleaned are located. The two screen elements are at least partially axially one inside the other pushed, which enables a compact design. This sorter is also for the Rough sorting thought. With a rotatably driven screen basket, therefore Wear can be reduced, but this makes the machine complicated and expensive.

In another pressure sorter, according to EP 0 955 406 A2, there are two cylindrical ones Sieve baskets arranged one above the other. The suspension to be sorted is within the Housing guided so that first a rotating coarse sieve ("knotter") from the outside to inside and then a fixed primary sieve is flowed through from the inside to the outside. The pass of the primary sieve is clearly the accepted substance of this sorter to look at, while the overflow of the primary sieve a so-called secondary sieve is fed. This machine is also relatively complex. To achieve a high Purity with high throughput is unfavorable.

From US 5,622,267 is also a pressure sorter with two or three screen baskets known. In cases in which the sieve baskets are switched so that the passage of the upstream sieve is fed into the inlet of the downstream sieve the flow in the upstream sieve from radially outside to radially inside (centripetal) guided. This involves a relatively high level of construction work, which is probably is justified if this machine for a fiber suspension with high Coarse material should be used.

In the machine shown in EP 0 795 641 A1, too, the fiber suspension is first passed into a sieve through which a centripetal flows, which is then followed by another centripetal Sieve connects. This machine should also be more intended for sorting coarse material. It is complex and obviously only satisfactory to operate with intermediate dilution.

The invention has for its object to build a pressure sorter so that it is compact and has a good separating effect even with fine interfering substances and thereby one relatively high throughput allowed.

This object is achieved by the features mentioned in the characterizing part of claim 1 Fulfills.

A pressure sorter designed in this way has the advantage that in one and the same Housing several, but at least two sorting operations carried out in succession can be. Optimal sorting quality is achieved with high throughput, because the flow control in the sorter was chosen so that the sieve baskets were centrifugal, that is, radially from the inside to the outside. A series connection of Highly effective sorters are otherwise only with considerable mechanical and technical control effort possible. With the invention, however, the number of Decrease pressure sorters significantly, even with high quality requirements. A pressure sorter according to the invention offers particular advantages in fine sorting. Especially in the areas of fiber processing where it is a matter of removing particularly fine impurities (usually slot sorting is there the pressure sorters used for this must be relatively large. Only like that can ensure sufficient throughputs with the fineness of the sorting openings be promoted.

The invention unfolds its advantages particularly where the series connected Sieves are fine sieves and have approximately the same sieve characteristics, i.e. in the same Sort size range. This is especially the case when the sieves with similar or the same slots are provided, with a slot width of at most 0.8 mm, preferably less than 0.3 mm. It has been shown that in technical Applications often fail to sort a single level for the required quality is sufficient, especially if the contaminants are of the same order of magnitude how the fibers are, and therefore the sieve with a certain probability can happen. This also applies to the highly effective pressure sorters Schlitzsiebkörben. Critical contaminants are primarily adhesive particles (stickies). With This problem cannot be solved by narrower sorting openings. Therefore one must Another sorting step with the same effect with the already cleaned fabric be made to reduce the likelihood of elimination from severe to increase sortable substances.

In addition to the technical aspects, such as a pressure sorter but there are also other requirements, such as the easy opening such machines and the easy accessibility of the screens. This is important because these need to be removed or cleaned occasionally. Constructive solutions that the arrangement and clearance of the sieves and the guidance of the material flows in concrete terms are described below.

When using the pressure sorter according to the invention, it can be of particular importance Be an advantage if the reject rate on the upstream sieve is significantly higher is set as the downstream. The reject rate is the volumetric Quantity ratio of the overflow, based on the feed to the corresponding sieve. Because of the higher content of impurities in the feed to the upstream sieve, there can be a reject rate that is approximately twice as high as that of the downstream sieve can be set.

Fig. 1

Ein Beispiel für einen erfindungsgemäßen Drucksortierer mit axial versetzten Siebkörben und zwei Rejektausläufen;

Fig. 2

ein ähnliches Beispiel, aber mit einer externen Gutstoffleitung und einem gemeinsamen Rejektauslauf;

Fig. 3

eine Möglichkeit zur getrennten Rejektableitung bei einem Drucksortierer, ähnlich wie in Fig. 2 beschrieben;

Fig. 4

einen erfindungsgemäßen Drucksortierer mit einem rotierenden Siebkorb;

Fig. 5

einen erfindungsgemäßen Drucksortierer mit zwei feststehenden, axial ineinander geschobenen Siebkörben;

Fig. 6

ein Beispiel mit exzentrisch im Gehäuse angeordneten Siebkörben.

The invention and its advantages are explained with reference to drawings. Show:

Fig. 1

An example of a pressure sorter according to the invention with axially offset screen baskets and two reject outlets;

Fig. 2

a similar example, but with an external accept line and a common reject outlet;

Fig. 3

a possibility for separate reject discharge in a pressure sorter, similar to that described in FIG. 2;

Fig. 4

a pressure sorter according to the invention with a rotating screen basket;

Fig. 5

a pressure sorter according to the invention with two fixed, axially pushed sieve baskets;

Fig. 6

an example with screen baskets arranged eccentrically in the housing.

The pressure sorter according to the invention shown schematically in FIG. 1 has Housing 6 in which there are two sieves, namely the first - upstream - sieve 1 and the second - downstream - sieve 2. The pressure sorter is like that built up that the inflowing through the overhead inlet 3 Paper fiber suspension S is first led to the feed side of the first screen 1. On this inlet side there are clearing elements 7 and 8, which belong to the screen clearer 5. In a manner known per se, the sieve is moved by the movement of the clearing elements 7 and 8 1 kept clear of constipation. After the paper fiber suspension S has the first sieve 1 has passed (accept substance A1), it first arrives in the first accept substance space 13 and then into the inlet area of the second sieve 2. This sieve is used for sorting again carried out so that the part of the paper fiber suspension that also contains the second sieve 2 has passed through the accept material outlet connection 4 from the housing 6 as accept material A2 is brought out again. Both screens are radial from the inside out flows through. The rejected forms a residue on the first sieve 1, which is caused by the first reject outlet 9 is discharged as the first reject R1. Something similar happens on the second sieve 2, the residue of which is the second reject R2 through the reject outlet 10 leaves the housing 6. In the event that the removal of air or If light materials are desired, a central light material connection 19 can be provided his.

Such a pressure sorter is usually constructed and assigned as a vertical sorter an underlying drive for the rotor 5, which serves to clear the screen. there allows the housing division 20 to remove the upper part of the pressure sorter. This is occasionally required to do maintenance work inside can. It is important that the rotor 5 and the sieves 1 and 2 are axial Do not hinder pulling apart. For this reason, it can be advantageous To make the inside diameter of the sieve 1 above smaller than that of the one below lying sieve 2. Another advantage of the arrangement shown here is in this, that the clearing elements 7 and 8 belong to the same rotor 5 for both screens 1 and 2 can.

The inlet spaces of the two screens are separated from one another by a plate 18 which is sealed in a contact-free manner against the rotor 5 by means of an annular gap 29. At the Annular gap occur only relatively low peripheral speeds, and the pressure is less than on the inside of the sieve. The plate 18 can be easily removed be divided so that the rotor can stop when the lower sieve is removed shall be.

The pressure sorter shown in FIG. 2 also has two screens 1 and 2, which are axial are so far apart that they are in different rooms. Unlike the sorter shown in FIG. 1, the fiber suspension S introduced into the housing 6 'via an inlet connection 3 located below. So that's why first flow through sieve 1 at the bottom and the second sieve 2 at the top. Acceptable substance A1, i.e. Passing through the first screen 1, the first accepting material space 13 becomes an external one - Here pump-free - pipeline 17 returned to the pressure sorter by enters an intermediate inlet 16, which is located on the upper part of the housing 6 '. The suction effect at the centrally located intermediate inlet 16 can transport the Support suspension. In any case, when the sorter is in operation, Inlet 3 and Gutstoffauslaufstutzen 4 a pressure drop applied from the outside on. If this overpressure is to compensate for the pressure loss in both screens, this can be done in in special cases, increase the pressure in the inlet area of the first screen very much. To this To be able to keep pressure lower would be a booster pump in the Pipeline 17 conceivable. Or the Siebräumer rotor gets on its upper one End face of pump blades 23 (shown in dashed lines), the pressure increase cause.

The accept A1 passes from the intermediate inlet 16 into the inlet area of the second screen 2. If he has passed this and has entered the second accepting material space 14, he can led out of the housing as accept material A2 through the accept material outlet connection 4 become. To simplify the drawing, the accept outlet spout 4 is in the upper Part of the housing 6 ', that is shown above the housing division 20. With advantage (easy opening of the case) it lies in the lower part. Then there is one Appropriate material collection chamber 28 to be provided, as shown in Fig. 3. The special one The construction of this pressure sorter allows - if desired - the two rejects R1 and to lead R2 out of the housing into a common reject outlet 11. A unwanted mixing of the rejects with the good substances is thereby caused by this type construction avoided. An aperture is used to control the reject flows provided, e.g. as part of the screen clearer 5, i.e. also rotating. It can be advantageous Aperture 12 to be adjustable. The screen clearer 5 is drum-shaped here attached clearing elements, which can be similar to the case shown in Fig. 1. Variations of different clearing elements are possible at any time and adjust according to the existing conditions and requirements.

In cases in which the rejects are to be discharged separately, there is one in the housing fixed cutting disc 26 useful, as indicated in Fig. 3. It forms with a ring 12 'running around the rotor (not shown here in section) a sealing gap 27 which e.g. is about 1 to 3 mm wide. The resulting very slight mixing of the two rejects R1 and R2 can be accepted. 3 also shows the variant already mentioned: the accept outlet spout 4 is located below the housing division 20, which facilitates its opening. The second accepted substance A2 For this purpose, the second accepting material space 14 becomes an accepting material collecting chamber 28 derived, which extends only over a small part of the housing circumference. To this is then the Gutstoffauslaufstutzen 4 connected.

A particularly compact and space-saving embodiment of the invention Pressure sorter results when the two sieves are pushed axially one inside the other are, i.e. are not in separate rooms. That leads to a low one Housing 6 ". Such an embodiment is shown in FIG. 4. With these pressure sorters, the introduced fiber suspension S introduced from above and radially from the inside out passed successively through the two screens 1 and 2. The Rejects R1 and R2 in the lower part of the pressure sorter and are separated dissipated from each other. The embodiment shown here has a special feature a rotatable inner strainer basket, which serves as the first strainer 1. In that the too this rotating sieve basket belonging to clearing elements 7 are fixed, the sieve is free held. The clearing elements 8, which are to act on the second sieve 2, rotate at the same peripheral speed as the rotating screen basket. The first sieve 1 and the broaching elements 8 belonging to the second sieve 2 are disc-shaped Plate 24 attached. This forms the upper part of the screen clearer 5, from which it follows opening 6 "can be removed upwards. The plate 24 contains Openings 25 for the incoming paper fiber suspension S. The second screen 2 is in the Housing fixed.

At the places where media-carrying clearers can be moved with respect to each other Partitions to be sealed against each other are usually column 22 sufficient. In special cases, contact seals must also be provided. Around Preventing short-circuit flows between good substances and rejects is one Throttle ring 21 is present, which is shown only with regard to its function.

Similar to the embodiment shown in FIG. 4, that of FIG. 5 has two axially sieves 1 and 2 pushed into each other, which are flowed through from the inside to the outside. However, both screens are fixed, while the clearing elements 7 and 8 on one common rotatable screen clearer 5 are attached. Again, the both rejects R1 and R2 are discharged separately, which has the advantage that differently designed chokes the reject currents can be easily controlled. Where that is not necessary, the two reject flows could also be through a common one Reject nozzles are derived.

In terms of flow technology, the pressure sorter according to FIG. 6 is particularly favorable the center line 30 of the housing 6 ″ ″ does not coincide with the center line 31 of the rotor 5 together, this offset being the distance of the rotor from the two Acceptance connection piece 4 or 15 enlarged. That leads to simple means larger flow cross sections in the areas of larger accept material volume flows. This eccentricity 32 can be approximately between 40 and 200 mm, depending on Housing size and is advantageously determined so that the flow rate of the Acceptable material flows cannot assume unfavorable values anywhere.

LIST OF REFERENCE NUMBERS

1-

first sieve

2

second sieve

3

flowguide

4

Gutstoffauslaufstutzen

5

rotor

6, 6 ', 6 "-

casing

7-

clearing element

8th-

clearing element

9-

Rejektauslauf

10-

Rejektauslauf

11

Rejektauslauf

12-

cover

12'-

ring

13-

accepts space

14-

accepts space

15

Gutstoffauslaufstutzen

16-

between the inlet

17-

pipeline

18-

plate

19-

Lightweight Connection

20

housing division

21-

throttle ring

22-

column

23-

pump blades

24

plate

25

opening

26-

cutting wheel

27-

sealing gap

28-

The accept plenum

29-

annular gap

30

center line

31-

center line

32

eccentricity

S =

Paper fiber suspension

A1 =

accepted stock

A2 =

accepted stock

R1 =

reject

R2 =

reject

Claims (24)

Pressure sorter for removing contaminants from a paper fiber suspension (S) containing contaminants with a housing (6, 6 ', 6 ") which contains at least two cylindrical sieves (1, 2),
the housing having at least one inlet connection (3), at least one accept material outlet connection (4) and at least one reject outlet (9, 10),
wherein the sieves (1, 2) are arranged such that the paper fiber suspension (S) introduced into the housing through the inlet connection (3) can flow through them in succession by the part of the paper fiber suspension (S) which comprises the first sieve (1) has passed as the first accept (A1), can flow to the second sieve (2) and
the part of the paper fiber suspension (S) which has also passed through the second screen (2) is led out of the housing through the accept material outlet (4) as the second accept material (A2),
characterized in that the supplied paper fiber suspension (S) in the housing (6, 6 ', 6 ") is guided radially from the inside to the outside by two cylindrical sieves (1, 2). Pressure sorter according to claim 1,
characterized in that there are exactly two cylindrical screen baskets. Pressure sorter according to claim 1 or 2,
characterized in that both screens (1, 2) have slit-shaped sorting openings. Pressure sorter according to claim 3,
characterized in that the slot width is at most 0.8 mm. Pressure sorter according to claim 4,
characterized in that the slot width is at most 0.3 mm. Pressure sorter according to one of the preceding claims,
characterized in that the sorting effect is approximately the same for both screens (1, 2). Pressure sorter according to one of the preceding claims,
characterized in that at least two screens (1, 2) are arranged coaxially. Pressure sorter according to claim 7,
characterized in that at least two sieves (1, 2) are kept free of blockages by a single rotating sieve clearer (5), the clearing elements (7, 8) of which are guided past the surfaces of the sieves (1, 2) at a short distance. Pressure sorter according to claim 8,
characterized in that the screen (2) closer to the drive of the screen clearer (5) has a larger diameter than the screen (1) further away. Pressure sorter according to one of the preceding claims,
characterized in that at least two reject outlets (9, 10) are present, one reject outlet (9, 10) each discharging the residue of a sieve (1, 2). Pressure sorter according to one of claims 1 to 9,
characterized in that there is a common reject outlet (11) which discharges the residues from at least two sieves (1, 2). Pressure sorter according to claim 11,
characterized in that a throttle element (12) is present between the reject spaces of the two screens (1, 2). Pressure sorter according to claim 12,
characterized in that the throttle element (12) is adjustable. Pressure sorter according to one of the preceding claims,
characterized in that the first sieve (1) is arranged axially outside the space in which the second sieve (2) is located. Pressure sorter according to claim 14,
characterized in that the accept material outlet connection (15) of the upstream sieve (1) is externally connected to an intermediate inlet (16) on the housing (6 ') which leads to the inlet side of the downstream sieve (2). Pressure sorter according to claim 15,
characterized in that the housing (6 ') has no internal connection between the accepted material space (13) of the upstream sieve (1) and the inlet space of the downstream sieve (2). Pressure sorter according to claim 16,
characterized in that the accept material outlet (15) of the upstream sieve (1) is arranged radially on the outside and that the intermediate inlet (16) is arranged centrally. Pressure sorter according to claim 16 or 17,
characterized in that the external connection is made via a pump-free pipeline (17). Pressure sorter according to claim 16, 17 or 18,
characterized in that the rotor serving as a screen clearer (5) has pump blades (23) on its upper end face. Pressure sorter according to one of the preceding claims,
characterized in that at least two screens (1, 2) are not rotatable. Pressure sorter according to one of claims 1 to 13,
characterized in that the first screen (1) is arranged axially within the space in which the second screen (2) is located. Pressure sorter according to claim 21,
characterized in that one of the screens (1, 2) is rotatable. Use of the pressure sorter according to one of the preceding claims,
wherein the consistency of the paper fiber suspension (S) supplied is between 1 to 3% and the paper fiber suspension (S) is free of hard contaminants with an expansion of more than 3 mm. Use according to claim 23,
characterized in that the reject rate of the first screen (1) is set to at least 1.5 times, preferably double, the reject rate of the second screen (2).

Images