EP1215335A1 - Pressure screen for cleaning paper pulp containing impurities - Google Patents

Abstract

The pressure sorter is used to remove contaminants from a paper fiber suspension (S) containing contaminants, especially if it has been obtained from waste paper. It contains two screen elements through which the first screen element (1) has a conical shape and can be rotated. An overflow (R1, R2) is formed and removed on each of the two screen elements. The paper fiber suspension (A2), which leaves the pressure sorter through the waste outlet (4), has already been largely cleaned by two sorting stages. The pressure sorter can be constructed as a vertical or horizontal sorter. Due to its design, it is also suitable for cleaning paper fiber suspensions with relatively coarse contaminants. <IMAGE>

Description

The invention relates to a pressure sorter according to the preamble of claim 1 or claim 2.

Pressure sorters are used in the processing of paper fiber suspensions, to process the fiber suspension in a wet sieving. To do this contains a Such a sorter has at least one sieve element with a large number of Openings are provided. The fibers contained in the suspension should pass through the Open openings while holding the unwanted solid components on it rejected and routed out of the sorter. As sorting openings round holes or slits are usually used. In most cases Provide pressure sorters of the type considered here with screen clearers, which are on the screen have clearing surfaces moved past. As a result, in a manner known per se Clogging of the sieve openings prevented.

Because both the state of dissolution of the paper pulp as well as the quantity and structure the dirt load constantly change in the course of the stock preparation process, it is in many cases necessary, pressure sorters in several stages with different To operate openings. In this way, a good separation of the achieve most of the resulting contaminants. There are such interfering substances differ significantly from the other contaminants by their sinking behavior, too separable by hydrocyclones. This technique is also known, so in general a series of hydrocyclones and pressure sorters are used to clean the fabric.

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 preparation very often before, especially with the substance that is directly from the pulper or after passage only one of the coarsest impurities removing cleaning device. This well-known sorter has in certain cases the disadvantage that in particular in the area of the flat pre-screen high wear occurs and the coarse impurities lead to malfunctions can.

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 axial pushed together, which enables a compact design. Other versions with two successively flowed through sieves are from EP 0 955 408 A2 and DE 21 40 904 known. The first sieve is cylindrical and is set in rotation. This However, apparatuses are disadvantageous in many applications. This is especially true with the Processing of coarse materials. A cylindrical sieve has in particular Disadvantage that the elongated ones, which tend to spin or wrap Impurities can easily put on such a sieve and then as a result of Rotation lashed down. You are then only manual after switching off removable.

A flat disc-shaped sieve, e.g. is known from WO 00/52260 a simple structure and takes up little space. However, it has only a small one Screen area, which is disadvantageous.

The invention has for its object to build a pressure sorter so that it is insensitive to clogging contaminants and at the same time good Sorting quality delivers. In particular, it should be usable for dissolved waste paper, that still a large part of the originally contained, little comminuted impurities contains.

This object is achieved in the characterizing part of claim 1 and claim 2 characteristics mentioned.

A pressure sorter of the type according to the invention is particularly suitable at the beginning of the To be used, where - still - a relatively large one Proportion of coarser contaminants in the suspension is carried. E.g. Waste paper is often suspended in the pulper or in a pulping drum an impurity content of over 2% of the solid. Part of this contaminant is relative coarse, so it is also rejected to a large extent in a 4mm perforation.

After entering the pressure sorter according to the invention, the suspension meets the Inlet side of the first screen element. Its rotation creates a centrifugal force, with which the impurities are thrown off the surface of this sieve element, provided that they are specifically heavier than the suspension surrounding them. To the Solid particles that are close to the sieve inlet do not just grip the towing forces created on the basis of the applied pressure difference, but also centrifugal forces. The more the longitudinal direction of the sieve opening is radial (instead of axial) is aligned, the stronger the free spinning effect and the lower the Danger of particles getting stuck in the openings. Heavy parts that on Screen elements are rejected as intended, leave its inlet area relatively quickly and are removed from the housing by the coarse project outlet. she Light impurities, rejected due to their size, especially plastic films. The sieve is not just less risk of wear, but it is also not so easy due to pieces of wire, Glass fragments and small stones clogged.

The spin effect depends of course on the speeds and the Radius at the point under consideration. The particular advantage of the invention is that that the first screen element is at least partially conical. A conical one Form combines the advantages of a large screen area with sufficient Spin effect from the sieve area.

The combination of the two working differently according to the invention Sieve elements in a housing creates a compact machine that also works with heavily contaminated liquids work reliably. That is also advantageous Possibility of using the first screen element and the reamer for the second screen element to be able to provide a common drive.

The pressure sorter according to the invention is light with an effective one Equip light dirt discharge. Styrofoam and film pieces can be made using the Centrifugal forces are already concentrated and removed before they are the first Sieve element have passed. The same applies to air. This accumulation and derivation of Easy parts are favored by a flat or conical first screen element.

Fig. 1

schematisch: Den funktionalen Aufbau eines erfindungsgemäßen Drucksortierers;

Fig. 2

Kraftverhältnisse am konischen Siebelement;

Fig. 3, 4, 5 + 6

jeweils eine Variante des Erfindungsgegenstandes;

Fig. 7

detaillierter den in Fig. 1 gezeigten Drucksortierer in geschnittener Seitenansicht.

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

Fig. 1

schematically: the functional structure of a pressure sorter according to the invention;

Fig. 2

Force relationships on the conical sieve element;

3, 4, 5 + 6

each a variant of the subject matter of the invention;

Fig. 7

in more detail the pressure sorter shown in Fig. 1 in a sectional side view.

Fig. 1 shows, even if only schematically, the most important functional parts to belong to the pressure sorter according to the invention. In operation, this is in the housing Device introduced the paper fiber suspension S through the inlet nozzle 3 and first arrives in the inlet space 10. This contains the conical first Sieve element 1. Its opening angle α is adapted to the requirements and lies in usually between 60 and 120 °. An important feature of the invention is that the first screen element 1 is set in rotation in such a machine can. The rotor 24 is used for this purpose. In order to clog the screen openings in the first To prevent sieve element 1, fixed sieve clearers 8 are indicated, which refer to the accept side of this sieve element, that is, on the outflow side and Generate pressure pulses. The effect of such screen clearers is known and does not need to to be explained in more detail. The arrangement on the accept side leads to a considerable wear reduction and prevents pinching of the sieve rejected substances. Interfering substances due to their size or shape Siebelement are rejected, so they can not pass, flow together with a small part of the suspension as overflow R1 through the coarse project outlet 5 from the housing. The same applies to such contaminants that are already on the basis of described centrifugal effect have not passed through the screen element 1.

The housing of the pressure sorter is built so that the pass A1 of the first Sieve element 1 can go directly to the inlet side of the second sieve element 2. The this sieve element 2 passing pass A2 is through the accept outlet 4 and rejected overflow R2 discharged through the fine reject outlet 6. To keep the The second screen element 2 provides moving scrapers 9, which here are connected to the rotor 24 are connected, that is, driven at the same speed as the screen element 1. However, it is quite conceivable that different speeds are advantageous. Then the first screen element 1 is to be driven by a further shaft (24 'in FIG. 3) which e.g. would be guided within a rotor 26.

A cylindrical sieve is particularly advantageous as the second sieve element 2, too Sieve basket called, chosen. Such sieve baskets offer both a large sieve area and also high stability and easy clearability. In the inventive At this point, pressure sorters are no longer a problem due to coarse contaminants expected. A small screen hole can therefore be selected.

In Fig. 2, the forces that act on a solid particle 14 are shown qualitatively, which is located near the screen opening 12. The centrifugal force 15 acts radially outwards and the drag force 16 in the direction of the sieve opening. at The centrifugal force 15 is heavy enough to make a resultant 17 too heavy generate that removes the solid particle 14 from the screen element 1. Important for that Sorting effect is the smallest diameter 13 of the sorting opening 12. In typical Applications of the subject of the invention, this diameter is at least 4 mm, because there is a relatively coarse material here. A phase in the entry area of the Sorting openings 12 can block the behavior of the rotating sieve element 1 improve. Under certain circumstances it makes sense to have different sizes of the sorting openings close. Because of the shape of the first screen element 1 are namely depending radial distance from the center different sorting conditions (inflow angle at the inlet into the sorting opening and centrifugal forces), which is often undesirable is. Such disadvantages can be compensated for by the measure mentioned.

Basically, as shown by way of example in FIG. 3, the pressure sorter according to the invention also be a horizontal sorter, that is to say a have horizontal axis. This sometimes brings space advantages and can Improve the discharge of heavy parts through the coarse project outlet 5, since here the Gravity becomes supportive.

The shape of the first screen element, in particular the opening angle α, plays how has already played an important role in determining the properties of the Pressure screen. In addition, as FIGS. 4 and 5 show, the first screen element 1 ' have several sections whose opening angles α are different.

There are also a number of known ones with regard to the second screen element Design options. The cylindrical shape should be optimal. As a scraper for Wings, foils (Fig. 1, 3, 5) or projections are kept free of sieves Drum rotors (see Fig. 4 and 7) can be used.

It may also be expedient to approximate the contour of the inlet space 10 to the contour of the first sieve element 1 to adapt. 6 shows an example of the type that to the conical first screen element 1 also selected a conical upper part of the housing has been.

The pressure sorter according to the invention already indicated in FIG. 1 is in FIG. 7 drawn a little more detailed without this figure being a construction drawing would be understood. The first screen element 1, designed in a conical shape, divides the upper one Part of the housing in an inlet space 10, which with the inlet nozzle 3 for the Suspension communicates. Only a part of the screen openings 12 is shown. A number of is located centrally within the first screen element 1 fixed screen clearers 8. These are on their underside with the housing connected. The two sieve elements are arranged so that the first sieve element 1 divides the upper part of the housing into the inlet space 10 and the first accept substance space 11. This first accepting material space 11, which is located centrally within the first screening element 1 is connected to the inlet area to the second screen element 2. The second Sieve element 2 in turn divides the accepted material space 20 from the lower part of the housing, which is connected to the outlet 4. The inlet area of the second Screen element 2 merges at its lower end into reject space 22, which in turn is connected to the fine reject outlet 6. The second screen element 2 is thereby by Blockages kept clear that on the rotor 24, which also drives the serves first sieve element 1, a drum 19 with clearers 9 placed thereon are located. The rotor 24 is expediently overhung, i.e. a vigorous, out Bearing 23 consisting of several parts holds the rotor from below. That way the upper part of the rotor remain free of storage, so that those in the upper Do not create spinning contaminants that are part of the sorter, but instead can slide in the middle. The is in the upper part of the sorter Light reject outlet 7, which is opened and closed here in cycles by a valve 18 can be.

In the inlet area to the first screen element 1 is an example Flow guide element 25 indicated. Such guidance elements are used by the To keep inlet spout 3 flowing in suspension in rotation and / or radially lead inside to the screen plate. Since the first screen element 1 in the operation of the Rotating pressure sorter, it is necessary to also rotate the suspension move so that they flow through the sieve openings 12 of the sieve element can.

Claims (25)

Pressure sorter for removing contaminants from a paper fiber suspension (S) containing contaminants with a vertical housing which contains at least two essentially rotationally symmetrical sieve elements which are arranged in such a way that the fibrous suspension introduced into the housing through at least one inlet connector (3) can flow through them in succession .
the upstream first sieve element (1, 1 ') being rotatable and
is arranged axially outside and above the space in which the second screen element (2) is located,
the part of the paper fiber suspension (A2) which has also passed through the second screen element (2) is led out of the housing through at least one accept material outlet (4) and
The housing has at least one coarse reject outlet (5) for the overflow (R1) accumulating on the first screen element (1,1 ') and at least one fine reject outlet (6) for the overflow (R2) accruing on the second screen element (2),
characterized in that the first screen element (1) has a conical shape with an opening angle (α) which is between 10 and 170 °. Pressure sorter for removing interfering substances from a paper fiber suspension (S) containing interfering substances with a horizontal housing which contains at least two essentially rotationally symmetrical sieve elements which are arranged in such a way that the fibrous material suspension introduced into the housing through at least one inlet connection (3) can flow through one after the other .
the upstream first screen element (1, 1 ') being rotatable,
the part of the paper fiber suspension (A2) which has also passed the second screen element (2) is led out of the housing through at least one accept material outlet (4) and
The housing has at least one coarse reject outlet (5) for the overflow (R1) accumulating on the first screen element (1,1 ') and at least one fine reject outlet (6) for the overflow (R2) accruing on the second screen element (2),
characterized in that the first sieve element (1, 1 ') has a conical shape with an opening angle (α) which is between 10 and 170 ° and is arranged axially outside and to the side of the space in which the second sieve element ( 2) is located. Pressure sorter according to claim 1 or 2,
characterized in that the opening angle (α) is between 60 and 120 °. Pressure sorter according to claim 1, 2 or 3,
characterized in that the downstream second screen element (2) is fixed in the housing, Pressure sorter according to claim 1, 2, 3 or 4,
characterized in that a centrally arranged light reject outlet (7) is located in the inlet space (10) assigned to the first screen element (1, 1 '). Pressure sorter according to claim 5,
characterized in that the light reject outlet (7) is closed by a valve (18) that opens automatically briefly at intervals. Pressure sorter according to claim 5 or 6,
characterized in that the rotor (24) driving the first screen element (1, 1 ') has no bearing at the axial end facing the light reject outlet (7). Pressure sorter according to one of the preceding claims,
characterized in that the first screen element (1) has a double-conical shape, the larger diameters being at the axially outer ends. Pressure sorter according to one of the preceding claims,
characterized in that the side of the cone with the larger diameter is directed towards the second sieve element (2). Pressure sorter according to one of the preceding claims,
characterized in that there are stationary screen clearers (8) on the flow side of the first screen element (1, 1 '). Pressure sorter according to one of claims 1 to 9,
characterized in that there are fixed clearers on the inlet side of the first screen element (1,1 '). Pressure sorter according to one of the preceding claims,
characterized in that the inlet side of the first screen element (1, 1 ') has a profiled surface. Pressure sorter according to one of the preceding claims,
characterized in that the inlet side of the first screen element (1,1 ') is provided with strips. Pressure sorter according to one of the preceding claims,
characterized in that the first screen element (1,1 ') is provided with round holes, the diameter of which is at least two millimeters. Pressure sorter according to claim 14,
characterized in that the round holes have a diameter of at least four millimeters. Pressure sorter according to one of the preceding claims,
characterized in that the first screen element (1, 1 ', 1 ") is provided with sorting openings which are different in size depending on the radial position on the screen element. Pressure sorter according to claim 16,
characterized in that the sorting openings lying radially further outside are larger than those located further inside. Pressure sorter according to one of the preceding claims,
characterized in that there are flow guide elements (25) in the inlet space (10) assigned to the first sieve element (1, 1 ') which influence the peripheral movement of the suspenison located therein. Pressure sorter according to claim 20,
characterized in that the flow guide elements (25) have curved surfaces on which the circumferential flow is deflected radially to the center. Pressure sorter according to one of the preceding claims,
characterized in that the second screen element (2) is a cylindrical screen basket. Pressure sorter according to one of the preceding claims,
characterized in that the second screen element (2) is provided with round sorting openings, the diameter of which is at most two millimeters. Pressure sorter according to one of the preceding claims,
characterized in that the second screen element (2) is kept free by moving scrapers (9) belonging to the rotor (24) which also drives the first screen element (1, 1 '). Pressure sorter according to one of claims 1 to 21,
characterized in that the second screen element (2) is kept clear by scrapers (9) moved by a rotor (26) and in that the first screen element (1, 1 ') is driven at a speed different from that of this rotor (26 ) differs. Pressure sorter according to one of the preceding claims,
characterized in that the inlet connection (3) opens tangentially into the housing. Pressure sorter according to one of the preceding claims,
characterized in that the largest inner diameter of the first screen element (1,1 ') is larger than that of the second screen element (2).

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