EP1245724B1 - Pressure screen for cleaning paper pulp containing impurities and its use - Google Patents

Abstract

The pressure sorting assembly, to separate impurities from a paper fiber suspension (S), has a housing (6) with at least two sieves (1, 2). The sieves are arranged in succession, in the flow path of the suspension from the inlet (3). Both sieves have slits of the same dimensions, for the separation of fine impurities from the suspension.

Description

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

Such a pressure sorter is for example from the US 4,913,806 A known.

Pressure sorters are used in the processing of paper fiber suspensions, namely to process the pulp suspension in a wet sieving. Includes Such a pressure sorter at least one screen, with a plurality of openings is provided. The fibers contained in the suspension should pass through the openings while rejecting the undesired solid constituents and out of the sorter again. Pressure graders can also be used for Fiber fractionation can be used in the overflow the long fibers and in the Pass the short fibers are enriched. As sorting openings are in the Usually round holes are used or slots. In most cases, there are pressure sorters of the type considered here, equipped with sieve scrapers close to the sieve be moved past. As a result, in a conventional manner clogging the Prevents sieve openings.

It is known that the pressure sorters in principle for both the sorting of relatively coarse, as well as very fine impurities can be used. On the respective purpose in use, such pressure sorters are not only matched by choosing the sieves themselves, especially their sorting openings, but also by constructive design of the machine and choice of operating parameters. It has meanwhile succeeded in producing sieves at a reasonable cost, which are very fine Openings, e.g. Have slots in the range of tenths of a millimeter. This succeeds to separate even very small impurities from the fibers. This in itself positive However, development has led to the fact that the sieves and thus the Sorting machines were getting bigger. Also, the number of stages, i. the number of successively to be passed by the paper fiber suspension pressure sorter was greater.

From DE 197 02 044 C1 is a vertical sifter for a pulp suspension known, which has two sieve elements in a single machine. In this Classifier, the material flow to be sorted first reaches the area of a plane Pre-screen, which is kept free on the inlet side with a reamer. Of the Pass through this level preliminary sieve is then in the interior of a guided rotationally symmetrical screen basket, through whose openings the accept passes so that the suspended paper fibers pass through this sieve basket can get into the Gutstoffauslauf. Such a sorter should in particular then be used when the supplied pulp suspension with a larger amount of coarse impurities is mixed. This comes as is known in the Waste paper preparation there before, where the material directly from the pulper or after passage a cleaning device removing only the very largest contaminants comes. This known sorter is optimized for the excretion of coarse Impurities. The free screen area is relatively small.

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

In another pressure sorter according to EP 0 955 406 A2 two cylindrical Sieve baskets arranged one above the other. The suspension to be sorted is within the Housing so led that first a rotating coarse sieve ("knotter") from the outside to inside and then a fixed primary screen is flowed through from inside to outside. The pass of the primary screen is clearly as the accept of this sorter view, while the overflow of the primary sieve a so-called secondary sieve is supplied. This machine is relatively expensive. To achieve a high Purity at high throughput, it is unfavorable.

From US 5,622,267 is also a pressure sorter with two or three screen baskets known. In cases where the baskets are switched so that the passage of the Upstream sieve is fed into the inlet of the downstream sieve is the flow in the upstream screen from radially outside to radially inside (centripetal) led. Here, a relatively high construction cost is operated, probably is justified if this machine for a pulp suspension with high Grobstanteil should be used.

Also in the case of the machine shown in EP 0 795 641 A1, the fiber suspension becomes first passed in a centripetal flowed sieve, which is then another centripetal Sieve connects. Also, this machine should be thought more for grocery sorting. It is laborious and apparently only with intermediate dilution to operate satisfactorily.

The invention is based on the object to build a pressure sorter so that he is compact and has a good release effect even with fine impurities and at the same time a relatively high throughput allowed.

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

With the invention, the number of Reduce pressure sorters decisively even with high quality requirements. Particular advantages are offered by a pressure sorter according to the invention in fine sorting. Especially at the points of pulp processing, which involves the removal of especially fine impurities goes (usually there is the slot sorting carried out), the pressure sorter used for it must be relatively large. Only like that With the fineness of the sorting openings, sufficient throughputs can be reliably ensured be encouraged.

The invention develops its advantages especially where the series connected Sieves are fine sieves and have about the same screen characteristics, ie in the same Sort size range. This is especially the case when the strainers with similar ones 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 sorting a single stage for the required quality is often not sufficient, especially if the impurities in the same order of magnitude how the fibers are present, and therefore the sieve with a certain probability can happen. This also applies to the highly effective pressure sorters Schlitzsiebkörben. Critical impurities are mainly adhesive particles (stickies). With narrower sorting openings can not solve this problem. That's why one has to another identical sorting step with the already cleaned substance thereby making the probability of elimination of difficult to increase sortable substances.

In addition to the procedural aspects under which such a pressure sorter but there are also other requirements, such as the easy opening Such machines and the easy accessibility of the sieves. That's important because These must occasionally be removed or cleaned. Constructive solutions that the arrangement and freedom of the sieves and the guidance of the material flows concretely will be described below.

When using the Drucksortierers invention, it may be of special Be beneficial if the Rejektrate on the upstream sieve significantly higher is set as at the downstream. The Rejektrate is the volumetric Amount ratio of the overflow, based on the inlet to the corresponding sieve. Because of the higher content of contaminants in the inlet to the upstream sieve can there an approximately twice the Rejektrate be set as the downstream sieve.

Fig. 1

Ein Beispiel für einen erfindungsgemäßen Drucksortierer;

Fig. 2

eine Möglichkeit zur getrennten Rejektableitung bei einem Drucksortierer, ähnlich wie in Fig. 1 beschrieben;

Fig. 3

ein Beispiel mit exzentrisch im Gehäuse angeordneten Siebkörben.

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

Fig. 1

An example of a pressure sorter according to the invention;

Fig. 2

a possibility for separate rejection in a pressure sorter, similar to that described in FIG. 1;

Fig. 3

an example with eccentrically arranged in the housing screen baskets.

The pressure sorter shown in Fig. 1 has two wires 1 and 2, which are axially are offset to each other so far that they are in different rooms. The pulp suspension S is introduced into the housing 6 'via a downflow inlet 3. That's why it lies first through sieve 1 below and the second sieve 2 above. The accept A1, that is the Passage of the first screen 1, is from the first accepts space 13 via an external - Here pump-free - pipe 17 returned to the pressure sorter, by enters an intermediate inlet 16, which is located at the upper part of the housing 6 '. The suction effect at the central intermediate inlet 16, the transport of the Support suspension. In any case, the operation of the sorter is in between Inlet 3 and Gutstoffauslaufstutzen 4 an applied from the outside pressure gradient at. If this overpressure compensates the pressure loss of both screens, the in special cases greatly increase the pressure in the inlet chamber of the first sieve. To this To be able to keep pressure lower, then would be a booster pump in the Pipe 17 conceivable. Or the Siebräumer rotor receives at its upper Stimulation surface pumping blades 23 (dashed lines), which causes a pressure increase cause.

The accepts A1 passes from the intermediate inlet 16 into the inlet space of the second sieve 2. If he has passed this and has entered the second accepts room 14, he can as accepts A2 through the accepts outlet 4 out of the housing become. To simplify the drawing of the Gutstoffauslaufstutzen 4 is in the upper Part of the housing 6 ', ie above the housing division 20, shown. With advantage (easy opening of the housing) it is in the lower part. Then there is one Provide accepts collection chamber 28, as shown in Fig. 2. The special one Construction of this pressure sorter allows - if desired - the two rejects R1 and R2 in a common Rejektauslauf 11 out of the housing. A unwanted mixing of the rejects with the accepts is thereby by this Art avoided the construction. To control the Rejektfluß is an aperture provided, e.g. as part of the Siebräumers 5, so mitdrehend. Advantageously, the Aperture 12 be adjustable. The Siebräumer 5 is here drum-shaped with mounted clearing elements. Variations of different clearing elements are always possible and correct depending on the circumstances and requirements.

In cases where the rejects are to be discharged separately, one is in the housing fixed cutting disc 26 of use, as indicated in Fig. 2. She forms with one on the - not cut here drawn - rotor encircling ring 12 ' a sealing gap 27, e.g. about 1 to 3 mm wide. The resulting very slight mixing of the two rejects R1 and R2 can be accepted. This Fig. 2 also shows the already mentioned variant: The Gutstoffauslaufstutzen 4 is located below the housing division 20, which facilitates its opening. The second Acceptance A2 For this purpose, from the second Acceptance space 14 into an accepts collection chamber 28th derived, which extends only over a small part of the housing circumference. To this then the Gutstoffauslaufstutzen 4 is connected.

In terms of flow technology, the pressure sorter according to FIG. 3 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 Gutstoffanschlusstutzen 4 and 15 increased. That leads with simple means larger flow cross sections at the areas of larger accepts volume flows. This eccentricity 32 may be approximately between 40 and 200 mm, depending on Housing size and is advantageously determined so that the flow rate of Gutstoffströme anywhere unfavorable values can take.

LIST OF REFERENCE NUMBERS

1-

first sieve

2

second sieve

3

flowguide

4

Gutstoffauslaufstutzen

5

rotor

6 ', 6' ''

casing

7-

clearing element

8th-

clearing element

11

Rejektauslauf

12-

cover

12'-

ring

13-

accepts space

14-

accepts space

15

Gutstoffauslaufstutzen

16-

between the inlet

17-

pipeline

20

housing division

23-

pump blades

26-

cutting wheel

27-

sealing gap

28-

The accept plenum

30

center line

31-

center line

32

eccentricity

S =

Paper fiber suspension

A1 =

accepted stock

A2 =

accepted stock

R1 =

reject

R2 =

reject

Claims (15)

1. Pressure sorter for removing impurities from a paper fibre suspension (S) which contains impurities, having a housing (6', 6''') which contains at least two cylindrical wires (1, 2),
   the first wire (1) being situated axially outwith the space in which the second wire (2) is situated,
   the supplied paper fibre suspension (S) in the housing (6', 6''') being guided radially from the interior to the exterior through two cylindrical wires (1, 2),
   the housing having at least one inlet pipe connection (3), at least one accepted stock outlet pipe connection (4) and at least one reject outlet (9, 10),
   the wires (1, 2) being disposed such that they can be flowed through in succession by the paper fibre suspension (S) which is introduced into the housing through the inlet pipe connection (3), in that the part of the paper fibre suspension (S) which has passed through the first wire (1) as first accepted stock (A1) can flow to the second wire (2),
   the accepted stock outlet pipe connection (15) for the first accepted stock (A1) of the upstream wire (1) being connected externally to an intermediate inlet (16) on the housing (6'), which intermediate inlet leads to the incoming side of the downstream wire (2), and
   the part of the paper fibre suspension (S) which has also passed through the second wire (2) being guided again out of the housing through the accepted stock outlet (4) as second accepted stock (A2),
   characterised in that
   the wire (1) which is flowed through first by the paper fibre suspension (S) is disposed at the bottom in the housing (6', 6''') and the second wire (2) is disposed at the top, and
   in that the paper fibre suspension (S) is introduced into the housing (6', 6''') via an inlet pipe connection (3) which is situated at the bottom.
2. Pressure sorter according to claim 1,
   characterised in that
   exactly two cylindrical wire baskets are present.
3. Pressure sorter according to claim 1 or 2,
   characterised in that
   both wires (1, 2) have slot-shaped sorting openings.
4. Pressure sorter according to claim 3,
   characterised in that
   the slot width is at most 0.8 mm.
5. Pressure sorter according to claim 4,
   characterised in that
   the slot width is at most 0.3 mm.
6. Pressure sorter according to one of the preceding claims,
   characterised in that
   the sorting effect is approximately the same in the case of both wires (1, 2).
7. Pressure sorter according to one of the preceding claims,
   characterised in that
   at least two wires (1, 2) are disposed coaxially.
8. Pressure sorter according to claim 7,
   characterised in that
   at least two wires (1, 2) are kept free of blockages by a single rotating wire cleaner (5), the cleaning elements (7, 8) thereof being guided past the faces of the wires (1, 2) at a small spacing.
9. Pressure sorter according to claim 8,
   characterised in that
   the wire (1) which is situated nearer to the drive of the wire cleaner (5) has a larger diameter than that of the more remotely situated wire (2).
10. Pressure sorter according to one of the preceding claims,
    characterised in that
    the housing (6', 6''') has no internal connection between the accepted stock chamber (13) of the upstream wire (1) and the incoming chamber of the downstream wire (2).
11. Pressure sorter according to one of the preceding claims,
    characterised in that
    the accepted stock outlet (15) of the upstream wire (1) is disposed radially outwardly and
    in that the intermediate inlet (16) is disposed centrally.
12. Pressure sorter according to one of the preceding claims,
    characterised in that
    the external connection is effected via a pump-free pipeline (17).
13. Pressure sorter according to one of the claims 8 to 12,
    characterised in that
    the rotor which serves as wire cleaner (5) has pump blades (23) on its upper end face.
14. Use of the pressure sorter according to one of the preceding claims, the consistency of the supplied paper fibre suspension (S) being between 1 to 3% and the paper fibre suspension (S) being free of hard impurities with a dimension of over 3 mm.
15. Use according to claim 14,
    characterised in that
    the reject rate of the first wire (1) is adjusted to at least 1.5 times, preferably twice the reject rate of the second wire (2).

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