EP1679403A1 - Pulper for comminuting and suspending papermaking material - Google Patents

Abstract

The sieve screen (3) has openings (5) with shapes other than circular. The openings are: oval, especially elliptical. They are alternatively slots and/or wavy. The sieve is rotationally-symmetrical. The length (L) of each sieve opening relative to the radius (6) running through the sieve center includes an angle between -80[deg] and +80[deg], preferably between -45[deg] and +45[deg]. The leading edge (10) of the rotor blade runs at an acute angle relative to the length of the sieve openings. This angle is preferably between -45[deg] and +45[deg]. The sieve opening length-to-width ratio is preferably at least 3. Maximum opening width (B) is 4-20 mm. Maximum length (L) is 10-100 mm. The openings are milled, stamped, produced by laser, or by steel-casting. The sieve is a combination of a sieve plate (11) with openings, and a support plate (12). The support plate is a frame- or coarse sieve construction. Its outer contours correspond with those of the plate; its openings are larger than those of the sieve.

Description

The invention relates to a pulper for comminution and suspension of pulp according to the preamble of claim 1.

Pulpers of this type are mainly used to suspend dried pulp or waste paper of various composition. They consist essentially of a container for the suspension and at least one rotor. The registered material is intensively mixed in large pieces, webs or pressed bales with water, whereby a hydraulic material drive is generated by the rotor. Understandably, such devices are optimized, aiming essentially for a fast and efficient dissolution. In many cases, the rotor is placed in close proximity to a flat screen that keeps it free of blockages. Through the openings of the screen, the dissolved substance is sorted by coarse impurities and withdrawn as a suspension.

The standard type for a pulper is a vertical cylindrical container with a rotor in the bottom area. In this container, water and the material to be dissolved is added from the top and with the help of the rotor creates a Trombenströmung in the suspension, ie in the inner region of the fabric is pulled down from the rotor and pressed radially outward in the bottom region, resulting in a Umtriebsströmung results. Another typical design is the open top pulper container with laterally inserted rotor. Then the suspension is conveyed approximately horizontally to the rotor and deflected on the side wall of the container carrying the rotor.

This hydraulically often less favorable form has the advantage of finding space under the paper machine as broke dissolver.

The previously mentioned sieve initially serves to carry out a separation in which the already sufficiently dissolved fractions of the pulp are drawn off through the openings of the sieve and not yet retained sufficiently dissolved. As a result, the dissolution process becomes more economical in a manner known per se; in particular, the pulper can, if desired, be operated continuously. Contaminants, ie essentially non-paper components, are retained or sorted out.

In many cases, this sieve also helps to enhance the dissolution process. The side of the rotor facing the screen plate interacts with the inlet edges of the screen openings. Although a certain distance between rotor and screen plate is always respected, the shear forces that occur are sufficient to further separate the pulp particles. Larger pieces can also bridge the distance between screen plate and rotor, so that a direct cutting effect occurs. The form and intensity of these processes depends on the requirements and the design of the pulper.

It is also known to further enhance the above-described dissolving effect by providing the screen plates with ledges on the inlet side, as e.g. from DE 101 16 367 is known.

From WO 03/033152 A1 a screen plate is known whose openings have been introduced by laser or water jet. These openings are not round, but provided with corners and preferably distributed like a mosaic on the screen plate. This should increase the dissolution effect.

The known sieves for such pulpers are usually provided with circular holes, a compromise must be found between the demand for optimum classification, ie the smallest possible Sortieröffenungen, and the demand for the highest possible throughput, so the largest possible open area.

The invention is based on the object to improve the known pulpers for the resolution of pulp so that with them the highest possible throughput of dissolved pulp can be achieved without the cost, especially for equipment and operation, rise. In special embodiments, it should also be possible to reduce the equipment costs or the operating costs.

This object is achieved on a pulper according to claim 1 with the features mentioned in the characterizing part of this claim.

Characterized in that the screen plate in the pulper especially with elongated round openings, e.g. Long holes or oval openings is provided, the dissolving power of the pulper, which results from the interaction of rotor and screen plate, can be increased. Due to the curves, the risk of attaching fiber fins or impurities prone to spinning (plastic films) is very low. The elongated shape also means that a larger free screen surface can be produced at approximately the same screen fineness.

It is also possible, by appropriate arrangement of the screen openings, which will be discussed in more detail, to optimize the edges, which form at the inlet into the screen opening, with respect to the dissolution effect. These edges can be arranged at a defined angle (cutting angle) to the sweeping past rotor blade edges.

In many cases, it is possible to ensure a good operation of the pulper even if the sieve is without attached strips, ie that then can be dispensed with the installation of additional strips.

Figur 1:

Den Siebbereich eines erfindungsgemäßen Stofflösers;

Figur 2:

Erfindungsgemäß ausgestaltete Sieböffnungen im Detail;

Figur 3:

Vorteilhafte Anordnung von langlochförmigen Sieböffnungen;

Figur 4 + 5:

Je eine weitere mögliche Anordnung von langlochförmigen Sieböffnungen;

Figur 6:

Sieb, das eine Stützplatte aufweist;

Figur 7:

einen Stofflöser in Seitenansicht;

Figur 8:

einen anderen Stofflöser in Ansicht von oben.

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

FIG. 1:

The sieving area of a pulper according to the invention;

FIG. 2:

In accordance with the invention configured screen openings in detail;

FIG. 3:

Advantageous arrangement of slot-shaped screen openings;

Figure 4 + 5:

Depending on another possible arrangement of slot-shaped sieve openings;

FIG. 6:

Sieve having a support plate;

FIG. 7:

a pulper in side view;

FIG. 8:

another pulper in top view.

FIG. 1 shows the screening area of a pulper according to the invention. It can be seen a rotor 2, which is arranged concentrically with an annular flat screen plate 1 in the pulper, not otherwise shown. The rotor 2 is provided with wings 4 and dimensioned so that it completely or at least for the most part sweeps over the screen surface of the screen 3 during rotation (arrow 7). According to the invention, the screen openings 5 of this screen 3 are not circular as usual but elongated. The graphic representation of the screen openings 5 is not to scale here, but should only identify the screen surface. More details about these screen openings is shown in further figures. For larger sieves, it is customary to first produce these as ring segments, which are then assembled in the pulper to form an entire sieve. In the example shown here, the whole sieve consists of a total of eight segments, four of which are drawn. The sieve segments are e.g. bolted to an underlying support frame 8. This can - unlike drawn here - be constructed so that it supports the screen even where there are no Siebsegmentgrenzen. Then it is possible to reduce the screen plate thickness and save costs, especially in the production of the screen openings. 5

FIG. 2 shows a possible embodiment of the screen plate in somewhat more detail. In this case 5 slots are selected for the screen openings with the length L and the width B, wherein the curves are semicircular. The length / width ratio UB here is about 4. In other cases, a length / width ratio of less than 2, for example, 1.7 conceivable. Compared to conventional circular screen openings in pulpers, it may be appropriate to dimension the slot so that its free area corresponds to a circular screen opening. When applying the invention to an open primary pulper (bale or machine broke entry), screen openings having a width B between 10 and 20 mm and length L between 20 and 60 mm are to be regarded as a typical embodiment. In a Sekundärstofflöser, that already works in a closed system, much smaller screen openings, eg with a width B of about 4 mm are provided.

At the opening edges 9, in cooperation with the rotor blades 4 moving close to them, releasing forces are transferred to the suspension, in particular the pulp. Unlike circular screen openings have elongated screen openings in this interaction with the rotor blade 4 a stronger dissolution effect. In addition, they offer an important opportunity to influence the dissolution effect. In particular, the orientation of the elongated screen opening 5 plays an essential role relative to the running through the center of the screen radius 6. In the example shown here, this angle α assumes a value of -5 °. If it is chosen to be relatively small, a stronger dissolution effect is to be expected, since the edge 9 is steep (perpendicular or almost vertical) is flown. With regard to this feature, other forms may also be useful, e.g. As Figure 3 shows, in which the longitudinal side of the slots are aligned exactly in the direction of the radius 6. In the left part of FIG. 3, screen openings 5 'with a length / width ratio of 2 are shown by way of example.

Another object of the invention is the adjustment of the optimum cutting angle β, the between the leading edge 10 of the Rotorflüsgels 4 and the opening edge. 9 the screen openings is formed. This cutting angle β is relatively small in FIG. 2 at 8 °, which leads to a strong dissolving effect.

According to FIGS. 4 and 5, the angle α = 45 °, or α = -45 °, wherein the version according to FIG. 4 promotes the radial transport of the substance, while FIG. 5 at least tends to prolong the residence time of the substance in the sieve region, since in the deflection at the opening edge 9 forms a radially inwardly directed flow direction. The angles may also be different, e.g. vary depending on the distance to the center of the screen.

Although the previously discussed slot shapes and their arrangement are typical examples of practicing the invention, they are not the only ones. Thus, e.g. also other oval / oblong shapes are chosen.

In order to reduce the production costs for the screen openings, the screen (according to FIG. 6) can consist of two layers, namely a screen plate 11 with the screen openings 5 and a support plate 12 connected thereto. In general, then the support plate 12 has the same outer contour as the one Screen plate 11. The passage openings 13 of the support plate 12 may be non-uniform and substantially larger than the screen openings 5, since they have no screening effect. Because of the support plate 12, the screen plate 11 can be kept relatively thin, which greatly simplifies the introduction of openings.

The most common form of pulper to which the invention can be applied is the upright cylindrical open top pulper according to FIG. 7, in which screen 3 and rotor 2 are located in the bottom region. During operation, stock S and water W are introduced into the container 1. The finished pumpable suspension is withdrawn through the sieve 3 as accept A. Such pulpers have long been known. The same applies to pulpers with laterally mounted rotors according to Figure 8. As already mentioned, such a lying container 1 'particularly advantageous under a Paper machine to be used for the dissolution of production committee. Another application is the Sekundärstofflöser, for example, according to DE-A-23 45 735, the screen plate is provided with modified according to the invention screen openings.

Claims (14)

Pulper for comminution and suspension of pulp (S) with an open-topped container (1, 1 ') and with at least one drivable rotor (2) arranged in the container (1, 1'), comprising means for circulating a suspension contained in the container in order to comminute the incorporated paper stock and to suspend it in the water, and with at least one sieve (3) whose screen surface provided with screen openings is largely or completely swept by the moving rotor (2),
characterized,
that the sieve (3) is provided with elongated round sieve openings (5, 5 ', 5 ") whose shape deviates from that of a circle. Pulper according to claim 1,
characterized,
that the screen openings (5) are oval, in particular elliptical. Pulper according to claim 1,
characterized,
are that the screen openings (5 ') long holes. Pulper according to one of the preceding claims,
characterized,
that the sieve is rotationally symmetrical and that the length (L) of the sieve openings (5, 5 ', 5 ") makes an angle (α) between -80 ° and + 80 relative to the radius (6) passing through the center of the sieve °, preferably between -45 ° and + 45 °. Pulper according to one of the preceding claims,
characterized,
in that the leading edge (10) of the rotor blades (4) relative to the length (L) of the screen openings (5, 5 ', 5 ") at an angle of intersection (β) between - 80 ° and + 80 °, preferably - 45 ° and + 45 ° runs. Pulper according to one of the preceding claims,
characterized,
in that the screen openings (5, 5 ', 5 ") have a length to width ratio of at least 1.5, preferably at least 3. Pulper according to one of the preceding claims,
characterized,
that the maximum width (B) is between 4 and 20 mm of the screen openings (5, 5 '). Pulper according to one of the preceding claims,
characterized,
that the length (L) of the screen openings (5, 5 ', 5 ") is between 10 and 100 mm. Pulper according to one of the preceding claims,
characterized,
that the pulper is equipped for dissolving paper machine broke. Pulper according to one of the preceding claims,
characterized,
that the screen openings (5, 5 ', 5 ") are produced by milling. Pulper according to one of claims 1 to 9,
characterized,
that the screen openings (5, 5 ', 5 ") are produced by punching. Pulper according to one of claims 1 to 9,
characterized,
that the screen openings (5, 5 ', 5 ") are produced by laser beam. Pulper according to one of claims 1 to 9,
characterized,
in that the sieve (3) is produced together with the sieve openings (5, 5 ', 5 ") in the cast steel process. Pulper according to one of the preceding claims,
characterized,
in that the sieve consists of a sieve plate (11) containing the sieve openings (5, 5 ', 5 ") and a support plate (12), wherein the support plate (12) is a frame or coarse sieve construction whose outer contour is substantially that of the sieve plate (11). 11) and which is provided with passage openings (13) which are larger than the screen openings (5, 5 ', 5 ").

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