WO2010124911A2

WO2010124911A2 - Method for treating a fiber suspension and screening devices for carrying out the same

Info

Publication number: WO2010124911A2
Application number: PCT/EP2010/053759
Authority: WO
Inventors: Günter FRIEDHELM; Paul-Wilhelm Sepke
Original assignee: Voith Patent Gmbh
Priority date: 2009-04-30
Filing date: 2010-03-23
Publication date: 2010-11-04
Also published as: EP2425052A2; WO2010124911A3; DE102009019664A1; CN102459755A

Abstract

The invention relates to a method for treating fiber suspensions (S) in a screening device having a closed housing (2) that comprises a screen (3), where a part of the substances supplied with the fiber suspension (S) is rejected and evacuated from the screening device as an overflow (R) while another part passes the screen (3) and is evacuated as a throughflow (A). A rotor (4), whose rotational axis (33) has a radial distance (V) to the center line (32) of the housing (2), produces a rotating whirl (5) in the housing (2). The dissolving effect of the screening device is thereby increased and/or the sorting effect improved.

Description

Process for treating a pulp suspension and screening devices for its implementation

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

An effect of such a method is to clean the supplied pulp suspension of contaminants, in particular plastic films and heavy parts, and thereby preferably further dissolve, so to disassemble or shred at least part of the fiber webs and pieces of paper in individual fibers. The process may also serve to prepare from an aqueous pulp suspension, e.g. may be recovered from waste paper to get out unwanted contaminants. As is known, the waste paper contains, in addition to the desired pulps, a more or less large amount of impurities which are not intended to get into the paper. Typically, multiple separations are required to remove the various contaminants at various stages of the conditioning process. Suitable for the method screening devices have a housing with an interior in which the pulp suspension, driven by the rotor, can form a Umtriebswirbel. With advantage they are with a flat annular

Equipped sieve, near which there is a rotor. They are often called secondary pulpers, fiberizers, fiber sorters or turbo-separators. Other suitable sieving devices have a conical sieve or a cylindrical sieve. Still others have two sieves, z. B. a flat and another cylindrical sieve, wherein z. B. the cylindrical sieve of the overflow of the plane

Sieves is fed (so-called Combisorter or Kombisorter).

From WO 2008/061582 A1 a sifter for processing a soiled pulp suspension is known in which the center line of the main part of the housing is oblique to the axis of the rotor. It cuts the

Axis of the rotor, the center of the cross-sectional area of said housing main body.

Usually, the raw materials are mixed at the beginning of stock preparation in a pulper with water and so far crushed that they can be pumped as a suspension from the pulper. Even if in many cases a pre-cleaning already takes place in the pulper, a considerable amount remains of impurities in the pumped suspension and enters the equipment used for the treatment. The sieve device on which this invention is based can be used, for example, to process the soiled suspension coming from the pulper. In this case, such a screening device (unlike the preceding pulper) can be operated closed. In this screening device so no direct solids entry takes place, but the pulp to be treated is supplied in already suspended form. In particular, the screening device is also suitable for a pulp suspension originating from a pulper without having passed through a sieve.

It is an object of the invention to provide a method with which it is possible to reduce the power consumption required for driving the rotor. In favorable embodiments, the dissolution of the pulp is to be reinforced and / or the rejection of impurities with the lowest possible fiber losses are carried out. In particular, the method should offer the possibility of further dissolving specks and pieces of paper in a waste paper suspension.

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

The subclaims 17 to 20 describe advantageous screening devices for carrying out the method.

In methods of this type, a rotor flow with a circumferential component is generated by the rotor movement, which has an axis of rotation substantially concentric with the rotor axis. This Umtriebsströmung is inventively not fitted concentrically in the housing but with offset in the radial direction of rotation axis. Due to this eccentricity of the Umtriebswirbel is no longer rotationally symmetric, which leads to larger

Particles are transported quickly to the sieve. This improves the separation of the contaminants from the fibers as well as the faster dissolution of fiber fins. The ineffective and unnecessarily energy-consuming symmetrical rotation of the pulp suspension is avoided and instead improves the sorting and / or dissolution performance. In favorable cases, the rotors can at the same

Effectiveness be smaller. These benefits can be through one or more Flow barriers are further enhanced, the eccentricity of Umtriebswirbels offers particularly good conditions.

Since the screening devices used are usually operated with positive pressure, have rotationally symmetric, ie cylindrical or conical housing with respect

Strength and manufacturing costs considerable advantages. Then the centroids of the cross-sectional areas mentioned in claim 1 are exactly in the middle. Especially with cylindrical or conical housings, the measures required for the process are very easy to perform. For deviating shapes such. B. oval or partially overlapping circular surfaces, the centroids can be determined by known mathematical methods.

The method is used to advantage when the supplied pulp suspension is a waste paper suspension, e.g. With a consistency between 1% and 8%, preferably between 3% and 6%.

The screening device according to the invention is able to retain contaminants in the housing with the aid of the sieve and to remove them from the pulp suspension. Compared with the prior art, it also has the advantage that

Resolution of specks and pieces of paper, possibly also to improve the detachment of coatings and printing inks.

The invention and its advantages will be explained with reference to drawings. Showing:

Fig.1 +2: a schematically illustrated in two views for explaining the method screening device;

3 shows a sieve device according to the invention with a conical housing; 4 shows a variant with Rejekttauchrohr;

Fig.5-7: each a schematically illustrated system example;

8 shows a sieve device according to the invention with a conical sieve;

9 shows a screening device according to the invention with a cylindrical sieve;

10 shows a screening device according to the invention with two sieves connected in series;

Fig.11 +12: each a special embodiment of flow barriers; - A -

13 shows a special embodiment for the favorable interaction of flow barrier and heavy particle separation;

FIG. 14 shows a special screening device with an axis of the rotor arranged obliquely with respect to the housing center line; FIG. Fig.15: a special apparatus set-up with vertical in operation

Rotation axis of the screening device.

The screening device shown very schematically in FIG. 1 has a closed essentially cylindrical housing 2, which is closed at the end faces. Connected tangentially via one here

Inlet neck 10, the pulp suspension S is fed into this housing 2. A flat sieve 3 separates the interior of the housing 2 from an accepts chamber 9 attached to it, into which the part of the pulp suspension S which has passed the sieve passes. He is then discharged as a pass A through an accepts outlet 7 from the accept chamber 9. The on the sieve 3

Refused, so the overflow R is led out of the housing 2 through a drain line 6. Near the screen 3 rotates at the inlet side of the screen 3, a rotor 4, whereby a Umtriebswirbel 5 is generated, which is indicated in Fig. 1 and Fig. 2 each by a hollow-headed arrow. It has a peripheral component (see Fig. 2), whose center of rotation extends substantially through the center line of the rotor 4, wherein in the technical reality certain deviations are possible. It is important that the axis of rotation 33 of the rotor 4 with respect to the center line 32 of the housing 2 has a distance V in the radial direction, which is advantageously at least 10%, preferably at least 20% of the inner diameter D2 of the housing 2. The centerlines of

Housing 2 and rotor 4 are preferably parallel, but it is also an inclination with an acute angle, z. B. possible with a maximum of 10 degrees.

The center of the drain line 6 is here on the axis of rotation 33 of the rotor 4. Another possible arrangement would be in the center line 32 of the

Housing 2, a position between these two center lines or below the center line 32 (eg, with the distance V).

Advantageously, the rotor 4 is moved close to the screen 3, to keep it free of blockages. For this he can with a minimum distance from

Screen 3 may be arranged, the maximum of 30 mm, preferably a maximum of 10 mm is. These values also apply to the embodiments shown in further figures. The sieves can be provided on the rotor side with screwed or welded strips, which significantly improves the Siebfreihaltung and Entstippung.

A measure for further improving the dissolution performance can be seen in FIG. 2 in the form of a flow barrier 11, which decelerates the buoyancy vortex and deflects the suspension S in the direction of the rotor 4. In addition, further shear forces can be generated in the pulp suspension. The flow barrier 1 1 is located at a point on the inside of the housing 2, which is offset here by 180 ° relative to the center of the rotor 4, so it has the largest distance from this. In this area, the peripheral speed of the Umlenkswirbels is less than on the opposite side of the housing. In general, a single larger flow barrier at this point is preferable to a plurality of smaller ones arranged in a distributed manner. The flow barrier 1 1 may be connected to the inner wall, z. B. be welded steel profile, which is tapered so that no solids can begin. Advantageously, the flow barrier 11 is equipped particularly wear-resistant, which also applies to the immediate environment on the housing. A height H of at least 5%, better at least 15%, even better at least 20% of the maximum diameter D2 of the housing 2, is favorable.

Fig. 3 shows a screening device in more detail, but without structural details. The housing 2 ^' here has a conical shape, which tapers towards the rotor 4. This brings especially with heavy parts in the pulp suspension S.

Advantages, as these can then be easily eliminated with a Schwerteilausgabe 12 (see Fig. 4). In the housing 2 ^' , a rotor 4 is arranged, which can be rotated by a drive in rotation. This rotor 4 serves both to generate the Umtriebsströmung and to keep the concentric with the rotor 4 arranged sieve 3 of blockages free. The axis of rotation 33 of the rotor 4 and the center of the screen 3 have a radial distance V to the center line 32 of the housing 2 ^' . The sieve 3 divides the interior of the housing 1 from the adjoining accept chamber 9, from which the passage A accumulated therein can be discharged through the accepts outlet 7. In the lower part of the housing 1 is a downward leading

Outlet opening 12 for the heavy parts. This embodiment also has a Flow barrier 11, which is positioned on the inside of the housing 2 ^' at a location which is offset by 180 ° relative to the center of the rotor 4. Depending on the raw material, other positions may be useful. The drain line 6 for the overflow R, as shown in FIG. 4, be extended in the interior of the housing 2 ^' in the direction of the rotor 4, so there have a dip tube 17. Such

Dip tube 17 stabilizes the Umtriebswirbel 5 and can increase the selectivity of the screening device.

Sieve devices for carrying out the method can be installed upright (FIGS. 10 and 15), horizontally (for example, FIGS. 1 to 9) or at an angle. As a rule, they will be operated with overpressure, so that the contaminants escape by themselves. The overpressure can regulate the amount of contaminants removed. But it is also possible to provide the Störstoffaustritt with a shut-off device, not shown here, and, for. to open and close intermittently. Another possibility would be a metering device, which conveys a certain amount continuously out of the interior without blockage

As already mentioned, it is possible to both purify the fed pulp suspension in the same apparatus, as well as further dissolve. So it is e.g. makes sense in a screening device of the type described here a

Further comminution of the pulp contained in the suspension, e.g. to improve the low-loss sortability of the substance. It should be weighed between the damage caused by comminution of contaminants and the benefits that can be achieved from the higher separation of impurities and fibrous webs. It should also be considered in this consideration how large the sieve openings in the sieve 3 are chosen, e.g. with a diameter of between 1, 5 mm and 10 mm. In cases where even greater comminution or defibration of the substances in the suspension is desired, there is an easy way to realize this. It will then namely 4 baffles 16 attached to the periphery of a rotor provided with wings 15, which can cause a gentle crushing in cooperation with the wing tips.

The uses of the screening device according to the invention are intended to

Hand of two plant examples, as shown in Figures 5 and 6, be explained. It is assumed that a pulper 18, in which the pulp, eg waste paper, mixed with water and transferred into a suspension. The pulper 18 is equipped in its bottom portion with a sieve, not shown, passes through the part of the suspension in the annular space 21 and is continued as Pulpergutstoff 22 according to Figure 5 in a separate settling tank 20, the coarse parts, in particular heavy parts 24 separates. The fibrous suspension S thus freed of coarse particles is pumped into a screening device 1 operated according to the invention, which essentially has the task already described of further dissolving the substance and separating off an overflow R (contaminant stream), whereby a purified flow A

(Acid stream) is formed. Such operated devices are also called Pulper Ableervorrichtungen. The overflow R of the sifter 1 enters a post-sorter, e.g. a sorting drum 23, in which a separation between impurities 26 and pulp suspension 25 takes place. This fibrous suspension 25 can be recycled to the pulper 18.

Fig. 6 shows in a similar system, the discharge of a withdrawn before the sieve of the pulper 18, so not passed through the sieve polluted fiber suspension 27. It then passes through a settling tank 20 passes into an inventively operated screening device 1. Der

Pulpergutstoff 22 can be further treated either in a further conventional sorting or in a sorting according to the invention.

The plant schemes in Figures 5 and 6 show only the most important process steps, the apparatus used for this purpose only hinted and

Conveyor and control devices are not shown.

7 shows a further example of the embodiment of the invention in which the pulp suspension S is cleaned in several, here three screening devices 38, 39 and 40. One or more of these screening apparatus may be used in accordance with

Claims are operated or configured. In this example, the overflow of the screening device 38 and 39 enters the inlet to the next screening device 39 or 40. The passage of the last stage (screening device 40) is returned to the previous stage (screening device 39) and the overflow of the last stage is the reject. The runs of the first two

Steps (screening devices 38 and 39) can be further processed as acceptances become.

FIG. 8 shows a sieve device for carrying out the method, in which instead of a flat sieve a conical sieve 3 ^' , cleared by a likewise conical rotor 4 ^' , is used. In addition to the larger screen area, this shape also has the advantage of better flow guidance and reduction of the risk of heavy parts in the rotor / screen area. Heavy parts are removed from this area faster by centrifugal forces. The flow barrier 1 1 extends here in the axial direction beyond the outlet opening 12 for the heavy parts, whereby the vortex 37 (see Figure 13) for better

Deposition can be used. This measure is not limited to the screening device described in FIG. 8.

A cylindrical sieve 3 ^" , as shown in FIG. 9, can also make enlargement of the sieve surface possible, and it is advantageous for it to flow in the centripetal direction, that is to say from radially outside to radially inward, as may be combined here with a flat sieve 3. It does not have to be used to create even more screen area, the screens are connected in parallel and the rotor 4 ^" has to be designed accordingly to keep the sieve or sieves free and to provide the required buoyancy in the housing.

The method according to the invention can also be carried out with a screening device which is provided with a plurality of screens, for which purpose FIG. 10 shows an advantageous example. Generically, such sorting devices are known from DE 37 01 400. They are also called Combisorter, Kombisorter or Endortierer. The screening device 1 ^' in Fig. 10 has a flat horizontally arranged screen 3, which is provided with a rotor 4, whose function has already been described. The part of the housing 2 ^" in which the buoyancy vortex is generated by the rotor 4 is essentially cylindrical and has a center line 32 which runs parallel to the axis of rotation 33 of the rotor 4 and has a radial distance V opposite the latter rejected substances are not discharged directly from the housing 2 ^" , but initially passed through an opening 28 to an overflow sieve 29, which is a cylindrical screen basket here. In this case, the center of the rotor 4 and the middle of serving as overflow sieve 29 can Sieve basket as here on the same line or be offset against each other. The screen basket is kept free of blockages by a clearing rotor 30. The overflow R ^' formed on the overflow sieve 29 is largely freed of fibers on the way up on the sieve surface and dewatered so that it emerges from the overhead reject chamber 31 as a reject suitable for disposal. Because of the requirement that this reject material R ^'contains as few fibers as possible, the preceding defibration (speckle dissolution) improved with the aid of the invention is of particular advantage. This screening device 1 ^'also has a flow barrier 11 which brakes the rotation of the suspension S in the housing 2 ^" and reduces wear.

In cooperation with the spinning vortex 5, not shown here also the defibration is improved, which further reduces the fiber losses on the overflow sieve 29. The proportion that has passed the overflow sieve 29, passes into another accept chamber 34, can be discharged and used in accordance with its purity.

In the plant example according to FIG. 7, the screening device 1 ^' shown in FIG. 10 is particularly well suited as the last sorting stage, that is to say as screening device 40.

The flow barrier 1 1 can be varied in shape and arrangement, to which the figures 11 and 12 show examples. Thus, a flow barrier 1 1 (FIG. 1 1) is also conceivable with a convexly curved slope 35 on the discharge side in order to prevent or weaken the formation of local, possibly wear-increasing, eddies. A similar effect can be there with a

Achieve flow barrier 1 1 ^" (Figure 12), the drain side has a more easily produced flat surface 36.

FIG. 13 shows a favorable possibility of utilizing the vortex 37 generated by the flow barrier 11 in order to more easily guide the heavy parts into the outlet opening 12 provided for this purpose.

In general, it is expedient for the center line 32 of the housing 2, 2 ^' or 2 ^{"to be selected} parallel to the axis of rotation 33. In special cases between these, however, a small oblique angle β, for example from 0 to 8, may also be used

Degree be set up, but this requires a higher construction cost. there are the perpendicular to the axis of rotation 33 of the rotor 4 cross-sectional areas of the housing 2 ^' of the rotation axis 33 ^{' cut} only in the point s, which have to the centroid of the cross-sectional area in each case a distance.

Since in this method the screening device is preferably operated in a closed system, it does not contain an open entry opening (for the pulp). Therefore, a horizontal, vertical or inclined installation of this machine is possible in principle. For practical reasons, in particular because of the better heavy part rejection from the screen area and the better

Accessibility from the side, in many cases, a horizontal center line installation 32 of the housing (see eg Fig. 3) is selected. Alternatively, Fig. 15 shows an installation example with a vertical center line 32 ^' and a vertical axis of rotation 33 ^"of the rotor 4. Such a measure may be expedient, for example because of special space conditions

Heavy parts (here with a heavy-duty sluice attached to it) is then also attached to a lowest possible point of the housing 2 ^' .

Claims

claims

1. A method for the treatment of pulp suspensions (S) in one

Sieve device (1, 1 ^' ) with a housing (2, 2 ^' , 2 ^" ), which has at least one sieve (3) on which a part of the pulp suspension (S) supplied substances rejected and as an overflow (R, R ^' ) is discharged from the screening device (1, 1 ^' ), while another part passes through the sieve (3, 3 ^' , 3 ^" ) and is discharged as a passage (A), as well as a

Rotor (4) which in the housing (2) generates a rotating Umtriebswirbel (5), characterized in that the rotation axis (33, 33 ^' ) of the Umtriebswirbel (5) generating rotor (4, 4 ^' , 4 ^" ) perpendicular Cross-sectional areas of the housing

(2, 2 ^' , 2 ^" ) are cut from the axis of rotation (33, 33 ^' ) at a point which is at a distance (V) from the centroid of the cross-sectional area.

2. The method according to claim 1, characterized in that the axis of rotation (33, 33 ^' ) of the rotor (4, 4 ^' , 4 ^" ) perpendicular cross-sectional surfaces of the housing (2, 2 ^' , 2 ^" , 2 ^'" ) of the rotation axis (33,33 ^' ) are cut only in such points that have the center of area of the cross-sectional area in each case a distance (V).

3. The method according to claim 1 or 2, characterized in that the distance (V) at least 5%, preferably at least 20% of the largest inner width, in particular of the largest inner diameter (D2) of the housing (2, 2 ^' ).

4. The method according to claim 1, 2 or 3, characterized in that the axis of rotation (33) of the rotor (4, 4 ^' , 4 ^" ) to the center line (32, 32 ^' ) of the housing (2, 2 ^' , 2 ^" ) is arranged in parallel.

5. The method according to claim 4, characterized in that the housing (2, 2 ^' , 2 ^" ) perpendicular to the center line (32, 32 ^' ) in

Has substantially circular cross-sections, and that the axis of rotation (33, 33 ^" ) of the Umtriebswirbel (5) generating rotor (4,4 ^' , 4 ^" ) to the center line (32) of the housing (2, 2 ^' , 2 ^" ) has a radial Distance (V) has.

6. The method according to claim 1, 2 or 3, characterized in that the axis of rotation (33 ^' ) of the rotor (4, 4 ^' , 4 ^" ) to the center line (32, 32 ^' ) of the housing (2, 2 ^' , 2 ^" , 2 ^'" ) is arranged at an acute angle of at most 10 degrees.

7. The method according to any one of the preceding claims, characterized in that it is carried out in a closed housing (2, 2 ^' , 2 ^" ).

8. The method according to any one of the preceding claims, characterized in that the pulp is the housing (2, 2 ^' , 2 ^" ) completely supplied as pulp suspension (S).

9. The method according to any one of the preceding claims, characterized in that in the housing (2, 2 ^' , 2 ^" ) located pulp suspension (S) with the rotor (4) is further resolved.

10. The method according to any one of the preceding claims, characterized in that in the screening device (1, 1 ^' ) at least one flat sieve (3), conical sieve (3 ^' ) or cylindrical sieve (3 ^" ) is used.

1 1. A method according to any one of the preceding claims, characterized in that the overflow of a screen (3, 3 ^' , 3 ^" ) to another in the same screening device (1 ^' ) used overflow strainer (29) is fed, whereby on this overflow strainer (29) rejected overflow (R ^' ) is formed and is discharged as a reject.

12. The method according to any one of the preceding claims, characterized in that the circumferential movement of Umtriebswirbels (5) by at least one, in particular exactly one flow barrier (1 1, 11 ^' , 11 ^" ) is braked.

13. The method according to any one of the preceding claims, characterized in that heavy parts from the screening device (1, 1 ^' ) by a separate

Outlet opening (12) are removed.

14. The method according to any one of the preceding claims, characterized in that impurities, in particular plastics with the overflow (R, R ^' ) from the

Sieve device (1, 1 ^' ) are discharged.

15. The method according to any one of the preceding claims, characterized in that the screening device (1, 1 ^' ) with a maximum of 60 degrees relative to the

Horizontal inclined centerline, preferably operated with horizontal centerline (32).

16. The method according to any one of claims 1 to 14, characterized in that the screening device (1, 1 ^' ) with a maximum of 30 degrees with respect to the vertical hired center line, preferably with a vertical center line (32 ^' ) is operated.

17. Sieving device for carrying out the method according to one of the preceding claims with a substantially circular Having cross-sections housing (2, 2 ^' , 2 ^" ), at least one inlet connection (10) for the pulp suspension (S), which leads into this housing (2, 2 ^' , 2 ^" ), at least one sieve (3, 3 ^' , 3 ^" ), at least one drivable rotor (4, 4 ^' ) which is movable near the screen (3, 3 ^' , 3 ^" ) relative thereto, an accept chamber (9) extending from the housing

(2, 2 ^' , 2 ^" ) through the sieve (3, 3 ^' , 3 ^" ), is divided, and with an accepts outlet (7) is provided and at least one of the housing (2, 2 ^' , 2 ^" ) connected to the screen (3, 3 ^' , 3 ^" ) rejected substances, characterized in that the axis of rotation (33, 33 ^' , 33 ^" ) of the rotor (4, 4 ^' , 4 ^" ) to the center line ( 33) of the housing (2, 2 ^' , 2 ^" ) has a distance (V) which is at least 10%, preferably at least 20% of the maximum inner diameter (D2) of the housing (2, 2 ^' , 2 ^" ).

18. A screening device according to claim 17, characterized in that the axis of rotation (33, 33 ^" ) of the rotor (4, 4 ^' 4 ^" ) to the center line (32, 32 ^' ) of the housing (2, 2 ^' , 2 ^" ) substantially is parallel.

19. A screening device according to claim 17 or 18, characterized in that in the housing (2, 2 ^' , 2 ^" ) at least one, preferably exactly one flow barrier (1 1, 11 ^' , 1 1 ^" ) is located with a substantially axial extent, in particular at least over half of the

Length (L2) of the interior of the housing (2, 2 ^' , 2 ^" ) extends.

20. A screening device according to claim 19, characterized in that at least one flow barrier (11, 1 1 ^' , 1 1 ^" ) has a radial height

(H) of at least 5%, preferably at least 10% of the maximum diameter (D2) of the housing (2, 2 ^' , 2 ^" ).