FI113948B - Procedures and devices for treating backwater - Google Patents

Description

1 113948

Method and apparatus for treatment of zero water

The present invention relates to a method and apparatus for treating zero water. In particular, the invention relates to a process for recovering the fiber save-all 5 for process improvement. One application is, for example, the recovery of fibers from the paper machine's zero water.

Fiber recovery processes are used when useful fibrous material has been subjected to filtrates of fiber processing processes, such as from the wire portion of a papermaking or similar production machine or the like, which is removed during web formation. zero water. Such filtrates, which are separated from the fiber suspension by various slit or aperture sieves or predominantly liquid-permeable wires, also differ from the useful fibrous material. The said fiber material is characterized in that most of it is the finest fiber fraction of the fiber suspension.

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Fiber recovery processes are most often accomplished by a variety of filters, such as a disk filter, consisting of a plurality of wireframe disks mounted on a horizontal axis and immersed in a partially containing suspension of the suspension to be treated. By applying pressure difference to the wire surfaces, i.e. The inside of the discs 20 is depressurized or externally pressurized to remove fluid from the fiber suspension inside and out of the discs through the shaft, and to form a fiber layer on the wire surfaces of the discs. Drum filters are also used in fiber recovery processes. The drum filters are usually made up of a wire surface drum attached to a horizontal axis, with a so-called "inner surface" arranged inside the wire surface.

25 filtrate trays through which the liquid is removed from the suspension. The problem with the wire surface of both types of filters is that it should be able to allow huge amounts of liquid to pass through, but it should also prevent the fines from flowing into the filtrate water. The best way to deal with so-called. filtration of zero water »· • · has proved to be a solution in which the long-fiber pulp is known as the so-called. first, a thin layer is formed from the auxiliary mass 30 on the wire surface, through which the actual zero water * »· filtration takes place.

: According to one prior art application, the auxiliary mass is added to the volume of zero water, so that, at the very beginning of the filtration, the auxiliary mass forms a thin filter layer on the wire surface. In the very first seconds of filtration, much of the fine fiber material enters the filtrate, which is usually returned to the filter feed before the auxiliary mass has sufficient time to form an effective filtration. On the other hand, if said layer were not formed at all, all of the zero fibers to be recovered would pass through the wire surface into the filtrate water. In order to avoid such a situation, in this prior art application, the auxiliary mass is usually fed in such a way that it has a solids ratio of between (0.5-) 1-1.5 (-2) in the zero water flow.

10 It is, of course, clear that the longer the fiber is present and the less fine it is, the better it will retain the recovered fibers, ie prevent them from getting into the filtrate water. Thus, the best auxiliary pulp is long fiber pulp pulp with a low content of short fibers and fines. However, this retention is not the only criterion for the quality of the auxiliary pulp, 15 but also the importance of the thickness of the fibrous mesh formed and its precipitation properties. If the auxiliary pulp is optimal and thus the fiber mesh is of the correct type, it will adhere to zero water fines throughout the thickness of the layer, not only the auxiliary pulp layer, thereby providing better and longer flow of filter fluid through the fiber mat.

In older save-subprocesses, only the choice of auxiliary pulp has sought to influence the performance of the fiber recovery filter.

US Patent No. 5,368,693 discloses a solution which deals with the so-called auxiliary mass fed to a fiber recovery filter. with a fractionator before the auxiliary mass- '·. mooring in zero water. In other words, the auxiliary mass is taken out of the mixing tank and passed through a fractionating device to the amount of zero water fed to the filter. In the solution according to the publication, fractionation of the auxiliary pulp is removed by fractionation, it improves the quality of the auxiliary pulp and thus enhances the operation of the fiber optic filter.

: The effect of the auxiliary mass fractionation is clearly visible when the auxiliary mass • »· ...: for example, mechanical pulps, TMP, SGW or PGW have to be used, 2 • · 2 · 3 113948 where the amount of fines is high, very generally over 30% and in some cases up to 50%. This is also the case with the secondary mass, which will become more common in the future as the use of secondary mass increases.

The solution according to 5 U.S. Patent No. 5,753,080 starts from the idea that auxiliary mass can be fed into a filter basin at a point different from the actual mass to be filtered, i.e. zero water. The filter surface used in the process according to that patent is first contacted with a thicker and auxiliary pulp, i.e. longer fiber pulp, so that a filter layer, i.e. pulp layer, is formed from the auxiliary pulp of the zero fiber 10. The filter surface is then moved to a more water-free region, whereby zero water and other small particles are filtered into the fibrous tissue from the zero water passing through the longer fibrous fiber layer.

Further, in the method according to that patent, the auxiliary mass and the zero water are fed into the filter basin separately and at a distance from each other such that a consistency difference is created between the filter basin and can be adjusted by adjusting the mass flows. Hereby, the filter surface according to the invention is displaced, e.g. rotated in the pulp to be filtered, so that it moves from a thicker region, i.e. an area containing more than 20 long pulp pulps, towards an area of zero fiber content. The method preferably uses a disk filter, whereby the auxiliary mass is fed to the area where the cleaned and rotating filter surface meets the pool surface. Thus, a layer of substantially longer fibrous material is first formed on the filter surface, which subsequently serves as a filtering layer of shorter zero fiber. Thus, zero water containing the »» »'25 is preferably supplied to the opposite side of the filter surface, i.e., the area from which it rises from the basin as it rotates. In this way, a "·" "1 pulp mixture is formed in the wafer sump, in which the length distribution of the fibers is infinitely varied between the auxiliary mass * * ·! .. feed point and the offset water feed point.

30 Although the solutions described above perform better than the prior art, they also have their own weaknesses.

For example, the solution according to the first US patent requires some sort of separate sorting or fractionating device for the auxiliary feed line, which naturally increases the cost of 4,119,448. In the solution according to that patent, the coarse fraction obtained from the fractionation is controlled as auxiliary mass. There is a risk here, as the coarse fraction may in some circumstances contain particles of such a large size that they can damage the wire of the fiber recovery device. The second US patent, on the other hand, does not take a stand at all on what helps.

Thus, the prior art processes described above have their drawbacks. On the other hand, the auxiliary pulp may be removed as such from the mixing tank, whereby it contains impurities which at least impair the performance of the fiber water filter 10, or worse, the wire water surface of the filter. On the other hand, the auxiliary mass can also be led to a separate fractionator which removes fines from the auxiliary mass but which cannot remove coarse impurities and which increases the investment and operating costs of the whole system.

Among other things, the above problems, as well as many other problems referred to in connection with the advantages of the invention, are solved by a process and apparatus for treating zero water in a process for preparing a cellulosic or paper-containing filtrate containing fibrous material from a fibrous suspension. with the aid of a fibrous layer formed from the auxiliary pulp, after which said separated fibrous material is returned to the process, it is characteristic that the fraction from the pulping process which is better than the pulp from the mixing tank of the production machine is taken as auxiliary pulp.

One preferred embodiment of the invention is characterized in that an auxiliary mass, a rejection, or a combination thereof, taken from a suitable stage of sorting after the mixing tank is used as an auxiliary mass on a zero water filter.

With the method and apparatus of the present invention, e.g. The following 30 benefits.

- resolved without prior assistance with a prior art sanitation unit in relation to the prior art, | V - sorting has removed from the suspension auxiliary pulp an unfavorable fines for filter drainage, whereby the filter capacity is substantially increased, incoming fresh water eg in paper machine jets, dilutions and condensate water - reduced fresh water consumption and heat input to the process by decreasing the heat output from the process as the wastewater volume decreases, do not affect the properties of the mass flow directly to the headbox through a machine tank or the like. Such interference is directed to the zero water filter because the secondary stage accept is passed back through the zero water filter to the mixing tank. Thus, the above mentioned disturbances do not affect the stability of the process, - some prior art solutions eliminate the possibility that various particles or impurities (rocks, pieces of wood, bale yarns, organic growth promoters, etc.) are transported to the dead water filter. Thus, the process remains cleaner and the overall efficiency of the process increases, for example, as the number of breaks in the zero water filter wires substantially decreases.

• ·; A process according to a further embodiment of the invention is characterized in that:. * 25 auxiliary mass is taken from a sorting plant for a pulping process, or a suitable fraction of the acceptor or rejection, or a combination thereof, which has better drainage properties than the pulp from the mixing tank of a production machine.

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A method according to another embodiment of the invention is characterized by:. 30 that a coarse fraction separated from a pulp component entering the mixing tank is taken as auxiliary mass for the fiber recovery device.

A method according to a third further embodiment of the invention has

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a woman, to extract a fraction from a pulp stream from a mixing tank to a fiber recovery device, from which a fines or other similar substance which interferes with the operation of a zero-water filter is removed.

A method according to a preferred further embodiment of the invention is characterized in that the pulp going from the mixing tank to the headbox is sorted in a sorting plant from which an acceptance or rejection fraction or some combination thereof is fed to a fiber recovery device, i.e. a zero water filter.

In another preferred embodiment of the invention, the method is characterized in that the sorting plant comprises a plurality of sorting steps by dividing the pulp from the mixing tank in the first sorting stage into a finer acceptance fraction and a coarser rejection fraction into a second sort reject fraction, and at least a portion of the acceptance fraction of the second sorting stage is fed to a fiber recovery device.

The process 20 according to a third preferred embodiment of the invention is characterized in that the sorting plant consists of a plurality of sorting steps by dividing the pulp from the mixing tank into a finer acceptance fraction and a coarser reject fraction in the first sorting stage,

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; 25, and coarser reject fraction, and • · at least a portion of the second stage reject fraction is exported to an auxiliary mass • · to a fiber recovery device.

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The method 30 according to a fourth preferred further embodiment of the invention is characterized in that the screening station consists of a plurality of screening steps by dividing the pulp from the mixing tank into a finer accept fraction and a coarser reject fraction in the first screening step; V - conducting the reject of the first sort stage to the second sort stage, - dividing said reject in the second sort stage into a finer acceptance S »· ·» I · 7 113948 fraction and a coarser reject fraction; -5 fractions and coarser reject fractions, at least a portion of the acceptance fraction of the third sort stage is fed to a fiber recovery device.

A method 10 according to a fifth preferred embodiment of the invention is characterized in that the screening station comprises a plurality of sorting steps by dividing the pulp from the mixing tank in the first sorting stage into a finer acceptance fraction and a coarse rejecting said rejection fraction into a third sorting step, dividing said rejection in a third sorting stage into a finer acceptance fraction and a coarser rejection fraction, delivering at least a portion of the third sorting stage rejection fraction to an auxiliary pulping unit.

Other features of the method and apparatus of the invention will be apparent from the appended claims.

* ♦ *. In the following, the method and apparatus of the present invention will be explained in more detail with reference to the accompanying drawings, in which Figure 1 schematically illustrates a fiber recovery process according to a preferred embodiment of the invention, Figure 2 also schematically illustrates a fiber recovery process further schematically according to another preferred embodiment of the invention t shape of the fiber recovery process.

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Figure 1 shows a prior art save-all process for a paper machine 11 ··> · 8 113948 approach system. The paper machine approach system includes a mixing tank 10 in which various pulp fractions, such as chemical pulp and mechanical pulp, and fillers are introduced and mixed together. From the mixing tank 10, the pulp is pumped by a pump 12 to a sorting system consisting of a plurality of 5 sorting stages, each of which in most cases consists of one sorting unit. The pulp is thus pumped by a pump 12 to the first sorting step, the so-called. a screener 14 for removing particles unsuitable for papermaking. The acceptor of the screener 14 continues into the machine container 16, where the pulp is diluted to the headbox consistency and from which the pulp is further pumped by pump 18 for a short rotation of the paper-10 machine. The reject of the primary screen 14, in turn, is taken to a second sorting stage, i.e. a secondary screen 20, whose accept is traditionally returned to the suction side of the pump 12 of the mixing tank 10 and the reject is taken to 25 along the zero-water set and from there on to the save-all filter 24, which is usually a disk filter. The fiber material recovered from the filter 24 is returned along the pipeline 27 to the mixing tank 10 of the papermaking machine. Alternatively, it is of course possible to use a separate fiber recovery tank to collect the pulp from the filter before it is further pumped into the mixing tank. The problem with the process 20 described above is that the pulp in the mixing tank 10 contains not only different fiber fractions but also different fillers and fines which; * '. when in contact with auxiliary pulp impairs the drainage properties of the auxiliary pulp # · • / by blocking the spaces between the fibers of the long-fiber auxiliary pulp

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also be of such a large particle size that they impair the resilience of the save-all filter.

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Fig. 2 shows a solution according to a preferred embodiment of the invention, which is largely in accordance with Fig. 1, with the only difference being that from which the auxiliary mass to be taken is taken. In FIG. 2, for simplicity, the same reference numeral as in FIG. 1 is used. The solution of this embodiment of the invention is characterized in that the acceptance of the secondary screen sorter 20 is not returned in the prior art from mixing tank 10 to machine tank 16. pipeline 30 takes the auxiliary mass from a second stage sorter • · from an accepting mixing tank 10 to a pipeline 26 leading to a zero water filter 24 pump • 9 113948 28. This solution avoids at least as much fines and fillers in the auxiliary mass for improved drainage. This will increase the separation of the zero fiber, increasing the filtrate purity and the filter capacity. However, it should be noted that in many cases, the amount of fraction that is taken as auxiliary mass 5 is so large that some of it must be returned to the process before being delivered to the save-all filter.

Fig. 3 shows a rat-10 wheel according to another preferred embodiment of the invention, which deviates to some extent from the prior art solution shown in Fig. 1. In the embodiment of Fig. 3, the reject of the first-stage sorting screen 14 is taken as auxiliary mass for the fiber recovery device 24, from which the fines are separated into the pulp going to the paper machine. According to this embodiment of the invention, said rejection fraction is carried by pump 40, although in some situations it can be accomplished without a pump, to fiber recovery device 24 along pipeline 42. However, the pipeline 42 is provided with a volume control valve 44 to direct only the desired amount of auxiliary mass to the save-all filter 24 and to direct the remainder of the reject of the screener 14 to a fiber recovery tank 46 to which the fiber fraction recovered by the save-all filter is returned. Further, in the embodiment of Figure 20, the pulp collected in the fiber recovery container 46 is pumped by pump 48 to a screen 50, the accept of which is introduced into the mixing tank 10 and preferably through a reject tank 52 and pump 54 to the reject screen 56. Acceptance of the screen screen 56 through.

25 'In fact, only a new type of stripping concept is shown above, where' 'particularly the second-stage strainer 50 is located at a new position. Having previously been placed directly in communication with the first-stage screen 14, it is now coupled between a save-all filter and a mixing tank.

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One important advantage of this embodiment is e.g. the fact that the reject of the first screening stage in sorting is almost ideally mass for the purpose of leaching except for the aid of a save-all filter. blocked existing fines.

113948 10

Further, it is possible that the first sorting screen is a device which performs both coarse and fine sorting. In this case, for example, a fine sorting reject is derived from the first step as a help mass for the save-all filter.

According to a third preferred embodiment of the invention, the auxiliary mass is taken to be the acceptance of a sorting reject screener, which is usually a third stage screener, which is otherwise a fiber fraction that is returned to the process. Further, it is possible for the second or third stage reject to be taken as auxiliary mass from sorting, in which case it is usually advantageous to mix these with some suitable acceptance fractions. What 10 fractions may be used as auxiliary mass in each case depends essentially on the kind of mass the product is originally intended to be made from. If a very pure pulp with virtually no coarse solids is used in the manufacture of the product, up to the third stage reject can be used as such as auxiliary pulp. On the other hand, the first embodiment shows a situation where the pulp 15 is assumed to be the one with the most impurities since only the accept fraction is shown to be used as auxiliary pulp. Thus, in the first embodiment, it is purely from these two ideas that no coarse impurities should be allowed into the save-all filter and that as little fines as possible should be allowed into the save-all filter. In other words, the main concern is the durability of the wire surfaces and only the secondary concern about the fines.

For the application of the method according to the invention it is advantageous if the consistency of the auxiliary mass is as high as possible before being fed to the filter. In this case: 2 5 it is advantageous to use the so-called. sorting of fresh pulp or thick pulp, wherein: the consistency of the auxiliary pulp has a consistency of between 1 and 4%, preferably about 3%.

If necessary, the fraction fed as auxiliary mass may also be precipitated, e.g. · With the device described in patent application 982043.

30 At this point, it is worth noting that our invention is not only about, !! for situations where the auxiliary mass is taken from the outflow flow i *, i.e. the mass, which is (possibly) mixed from several different components.

A: Our invention also encompasses solutions whereby a fraction of the sorting of a pulp component entering a mixing tank is taken as auxiliary mass. Thus, for example, 11 113948 is a fraction of sorting of any pulp component entering the mixing tank. Thus, for example, a coarser reject fraction of the wreck sorting can be used as auxiliary mass, whereby the finer accept fraction obtained from the wreck is introduced into the mixing tank. It is, of course, still possible to fractionate the above reject fraction further so that the acceptances of the 5 second sort steps are used as auxiliary mass and the coarser reject is led to separate treatment. Similarly, a fraction can be taken as auxiliary pulp, for example, from a variety of mechanical, chemimechanical, chemical or recycle sorting plants. The solutions described above differ from the solution described in U.S. Patent 5,368,693 in that the solution of that U.S. Patent discloses the extract mass from each pulp component into the mixing container, while the present invention uses a coarser fracture disassembled for the final product to sort each pulp component.

In fact, our invention can be considered to encompass all such solutions and methods that utilize a fraction of a paper, board or similar production machine approach system or a prior art process for the manufacture of a pulp component which has the leaching properties without further processing (cf. U.S. Pat. 5,368,693) better than the drainage properties of the pulp from the mixing tank. These processes are referred to collectively as the "mass production process" in the attached claims.

'* * ··' As seen above, a new and • disadvantageous solution to the known problems of the prior art has been developed. zero water so that fiber recovery pulp; : the circulation and circulation of 25 filters used in the recovery industry and paper industry, and thus the investment cost. It should be noted, however, that although the two preferred embodiments of the invention have been set forth above, they are not intended to limit the invention to these exemplary embodiments, but merely to define the scope and scope of the invention: the appended claims. Thus, it is clear that e.g. The terms used in the above description · · *: the fractionator and the processor include all devices capable of performing the functions described above. It should further be noted that in the method of the present invention it is possible to export either • · «'. directly into a zero water filter or in combination with zero water.

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Claims (23)

A process for treating backwater, wherein in a pulp, paper or cardboard manufacturing process the filtrate containing fiber material separated from a fiber suspension is measured into a fiber recovery device, where the useful fiber material is separated from the filtrate mainly by means of a fiber layer formed from auxiliary pulp. the separated fiber material is returned to the process, characterized in that as auxiliary mass either a coarse fraction is taken from the screening of the pulp components preceding the mixing vessel (10) or a suitable acceptance or rejection fraction from the pulp stream which prefers from the mixing vessel (10) to the inlet tray or , whose infiltration properties are better than the mass obtained from the mixing machine of the production machine. Process according to Claim 1, characterized in that as auxiliary mass in the fiber recovery device (24), from the mass stream which likes from the mixing vessel (10) to the inlet carriage is taken a fraction from which the fine material or other material which interferes with the function of the fiber recovery device (24) has been separated. 3. A method according to claim 2, characterized in that the pulp which likes to be filtered from the mixing vessel (10) into the inlet carriage in a filter, from which an acceptance or rejection fraction from some step or a combination of these is led to the fiber recovery device, i.e. a backwater filter (24). • j Method according to Claim 3, characterized in that the silage consists of several screening steps, such that *. - the mass from the mixing vessel (10) in a first screening step (14) is divided into a finer acceptance fraction and a coarser rejection fraction, the rejection from the first screening step (14) is led to a second screening step (20), 30. The reject is divided into the second screening step. (20) in a finer! - acceptance fraction and a coarser reject fraction, and at least a portion of the acceptance fraction from the second screening step (20) in the transfer recovery device (24) as auxiliary mass. | 35 5. A method according to claim 3, characterized in that the silage consists of several. : screening step such that the mass from the mixing vessel (10) in a first screening step is divided into a finer acceptance fraction and a coarser reject fraction, the reject from the first screening step is led to a second screening step, said reject is divided into the second screening step into a finer acceptance fraction and a coarser reject fraction, and at least a portion of the reject fraction from the second screening step is led to the recovery device (24) as auxiliary mass. 6. A method according to claim 3, characterized in that the silage consists of several screening steps, such that the mass from the mixing vessel (10) in a first screening step is divided into a finer acceptance fraction and a coarser reject fraction, the rejection from the first screening step leading to a second screening step. said reject is divided into the second screening step into a finer acceptance fraction and a coarser reject fraction, said reject fraction from the second screening step is passed to a third screening step, said reject is divided into the third screening step into a finer acceptance fraction and a coarser reject fraction, and at least one part of the acceptance fraction from the third screening step is added to the recovery device (24) as auxiliary mass. Method according to claim 3, characterized in that the silage consists of several: sieving steps, such that the mass from the mixing vessel (10) in a first sieving step is divided into a finer acceptance fraction and a coarser reject fraction, - the reject from the first one. the screening step is led to a second screening step, - said reject is divided into the second screening step into a finer acceptance fraction and a coarser reject fraction, *. - said reject fraction is passed to a third screening step, - said reject is divided into the third screening step into a finer acceptance fraction and a coarser reject fraction, and at least a portion of the reject fraction from the third screening step is added to the recovery device (24). ) as an auxiliary mass. · .; 35 •. | 8. A method according to claim 3, characterized in that the sieve consists of several screening steps, such that the mass of the mixing vessel (10) in a first screening step (14) is divided into a finer acceptance fraction and a coarser reject fraction, and at least part of the coarser fraction. the reject fraction is led to the recovery device (24) as auxiliary mass. 5 Method according to claim 8, characterized in that a first part of the reject fraction from the first screening step (14) is led to the fiber recovery device (24) as auxiliary pulp and a second part of said reject fraction together with the recovered fiber pulp obtained from the recycling device 10 leads to a second screening step. (50). Method according to claim 9, characterized in that said combination of fiber pulp and reject fraction in the second screening step (50) is divided into a finer acceptance fraction and a coarser reject fraction, and the acceptance fraction of the second screening step (50) is added to the mixing vessel (10) and the reject fraction into a third screening step (56). Method according to claim 1, characterized in that, as auxiliary pulp, a suitable reject fraction is taken from a screening pulp, mechanical, chemical-mechanical or chemical pulp or recycled pulp. Method according to any of the preceding claims, characterized in that • the auxiliary mass is measured in the backwater filter (24) together with the backwater. 25 Method according to any of the preceding claims, characterized in that the auxiliary mass is measured to the backwater filter (24) separately from the backwater. :) t> · » Apparatus for treating backwater, consisting of a mixing vessel (10), a; We silage which is arranged at least in part between the mixing vessel (10) and the production machine inlet carriage, a fiber recovery device (24) and V required pumps (26) and pipelines (25, 27, 28, 42) for the transport of backwater »I. : Treated, auxiliary pulp, recycled fiber material and filtrate of the recovery device (24), characterized in that the sieve (14, 20, 22; 50, 56) is joined to the recovery device (24) by a pipeline (30, 42) or devices further comprise the screening of various pulp components in front of the mixing vessel (10), the screening of some of the various pulp components being joined for the part of its reject line with the recovery device (24) by a pipeline. Devices according to claim 14, characterized in that the sieve comprises at least a first stage sieve (14) and a second stage sieve (20, 50). Devices according to claim 15, characterized in that the reject outlet in the first stage screen (14) is connected to the recovery device (24) by means of a pipe (42). 10 Devices according to claim 16, characterized in that a valve (44) with which the mass flow to the fiber recovery device (24) is controlled is arranged in the pipe (42). Devices according to claim 15, characterized in that the second stage screen (50) is arranged in the process between the fiber recovery device (24) and the mixing vessel (10). Devices according to Claim 15, characterized in that the acceptance outlet in the second stage screen (20) is connected to the pipe (30, 25) which is suitable for the recovery device (24). Devices according to Claim 15, characterized in that the reject outlet in the second stage screen (20) is connected to the pipe (30, 25) which is suitable for the recovery device (20). t ·. Apparatus according to Claim 15, characterized in that the filtering further comprises a third screening step, which acceptance outlet of the screening step (22) is connected to the pipeline (30, 25) which likes the recovery device (24). 30 Apparatus according to Claim 15, characterized in that the sieve further 'comprises a third screening step, which is the straightening outlet of the screening step (22) connected to': the pipeline (30, 25) which is suitable for the recovery device (24). * * · • • 35 Devices according to claim 14, characterized in that the recovery device (24) consists of a disk, drum or corresponding filter.