JPH0327192A - Screen, filtering method and filter - Google Patents

Abstract

PURPOSE: To prevent a fiber bundle, a slub, a node or the like from entering into a light reject-discharging pipe by introducing a diluting liquid at the neighbor of a top cover of a rotor to decrease the concentration of the rejected material. CONSTITUTION: An accepting chamber 17 is installed in the exterior of a screen drum 2, and the upper end of a discharging pipe 19 is disposed adjacent to the inner surface 21 of a rotor top cover 12. A light rejected material flows through a rotor bottom part 23 into a space 22 in the inside of the rotor, and is gathered in a space at the under part of the top cover 12. When a valve 32 is closed and a valve 31 is opened, the diluting liquid flows in the pipe 19 in the rotor 3. When the valve 31 is closed and the valve 32 is opened, the diluted and washed light reject flows out from the interior of the rotor. The remaining rejected material flows into a reject chamber 15, and is discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filtration method and apparatus for separating solid particles, such as fiber bundles and lightweight particles, from a fibrous slurry used in a papermaking process. The apparatus has a substantially vertical cylindrical screen and a substantially cylindrical rotor concentrically disposed therein, the rotor and screen defining a filtration area for the pulp. . The apparatus further includes an acceptance chamber surrounding the outer surface of the screen and an inlet for supplying pulp to be filtered into the upper end of the filtration area.
It has a reject chamber connected to the lower end of said filtration region and device means for separating heavy and light impurities from each other within said rotor. The method includes introducing a diluent liquid inside the rotor near the top cover of the rotor to separate and wash lighter rejects from heavier rejects, fiber bundles, and knots.

For example, when filtering paper pulp containing various impurities in the screen described in U.S. Pat. I'm here. The particles separated in this way, whose specific gravity is lower than the average particle, ie, the specific gravity of the lightweight rejected material, include, for example, various plastics. The remaining reject material includes, for example, fiber bundles and knot pieces. One object of the present invention is to provide a filtration device that separates light impurities from reductate in a simple manner. The reason for removing lightweight reject materials, such as plastics, from the redirect stream is that plastics and the like are extremely harmful in the paper manufacturing process. Rejects from the filtration device are returned to the filtration device, usually via a grinding device, so that lighter weight rejects, such as plastics, are also ground to recover all fibers from the fiber bundle. The lightweight rejects are thus small enough to be accepted by the screen and sent to the paper machine, reducing the quality of the end product.

The filtration device of which the present invention is a significant improvement was developed from the known screen disclosed in, for example, U.S. Pat. No. 3,363,759.

An improved version of the filtration device of the above-mentioned patent is modified to remove plastic, and the improved device is disclosed in U.S. Pat.
, 912,622. In this refinement, the separation of light particles from the redirected pulp is carried out by means of a pipe, one end of which is fixed to the inlet end of the screen, and the other end of which extends through an opening in the cover of the casing. Delivered into pipes. A conical extension is provided in the other end of the pipe extending to the open upper end of the rotor. Due to the vortex motion of the rejected bulb, the lighter rejects concentrated in the inner part of the vortex flow out into the discharge pipe, while the heavier rejects collected in the outer part are recycled into the filtration area. . In order to achieve efficient separation work, there must be plenty of reduct flow;
This reduces the machine's capacity.

The filtration device on which the invention is based comprises a substantially vertical cylindrical screen and a cylindrical rotor disposed concentrically inside the screen, the substantially closed outer surface of which is located inside the screen. a cylindrical rotor defining with its surface a filtration area for pulp; an acceptance chamber surrounding the outer surface of said screen; and a cylindrical rotor for feeding pulp to be filtered into an upper end of said filtration area. It has an inlet, a reject chamber connected to the lower end of the filtration region, and means for separating heavy and light impurities from each other inside the rotor.

The means for separating the heavy and light impurities or reject components is a conduit extending from the outside of the device through the inner pivot portion of the rotor to the cover of the rotor. The filtration device is more fully described in US Pat. No. 4,634,521, which is incorporated herein by reference.

One object of the present invention is the above-mentioned U.S. Pat.
In connection with the apparatus of No. 1, it is an object of the present invention to further improve the process of separating the lightweight material to be rejected from the reject material.

It has been found that it is important to reduce the amount of lightweight reject material as much as possible since it is normally discharged from the filtration device into a tank for further processing. Said further processing is necessary in order to recover the fibrous material which is discharged together with said lightweight reject material. This is because the lighter material that is rejected typically has about 90% of the fibrous material that can be recycled back into the system.
This is because it contains 0%. The term further processing usually means separation sorting structures by filtration devices and perhaps even cyclones to separate the lightweight reject material, often plastic, from the acceptable fibrous material. By using the improvement according to the invention, it is possible, under the most favorable circumstances, to discharge lightweight reject materials, mainly plastics, without recycling them to any further filtration step. It is. This improves the ability of the device to separate lightweight reject material from fiber bundles, slives, knots, etc., so that said fiber bundles, knots, etc. do not enter the discharge conduit for lightweight reject material. be achieved. It has been found that the lightweight reject material, which is primarily plastic, can spontaneously separate from the cellulosic material if the concentration of the suspension is low. Now, by introducing the diluent inside the rotor near the top cover of the rotor, the concentration of the suspension is reduced where necessary.

As the concentration decreases, the plastics and similar reductants float on the liquid/suspension and fill the space below the top cover of the rotor.

The simplest way to do this is to direct the diluent upwardly through the same conduit used to remove the lightweight reductant. This is made possible by arranging a branch pipe with a valve connected to a conduit leading into the interior of the rotor for removing the lightweight rejects. Preferably, the branch pipe is disposed outside the filter housing adjacent to a valve provided in the conduit for discharging lightweight rejects between the valve and the filter housing. The present invention provides a reliable method for removing lightweight rejects in a situationally appropriate manner.

(Example) The main parts of the screen illustrated in FIG. 1 are a multi-compartment housing 1 and a substantially cylindrical screen drum 2.
, a substantially cylindrical rotor 3, and a shaft 4.

The shaft is rotatably mounted inside the rotor by a bearing on a cylindrical support member 5, and the support member is fixed to the housing by a sealing joint. The rotor is mounted on a belt pulley 6 provided on the upper end of the shaft as well as on the lower end of the shaft for rotating the rotor. A disk 7 is fixed to the upper end of the support member, through which the shaft extends.

In a preferred embodiment, the rotor outer surface 9, provided for example with hemispherical projections 8, as well as the inner surface of the concentric screen drum define a ring-shaped filter area 11, into which the pulp to be filtered is fed. The upper end of the rotor is closed by a top cover 12 in which the shaft is fixed.

The upper part of the housing consists of a feed chamber 13, which is provided with an inlet connection 14 for the valve to be filtered.

In the lower part of the housing there is a reject chamber 15 with an evacuation connection 16.

An upper end of the filtration region is connected to the feed chamber and a lower end is connected to the reject chamber. There is an acceptance chamber 1 outside the screen drum.
7 is provided.

An inlet 18 for diluent liquid can be arranged in the reject chamber.

A discharge conduit 19 is disposed within the support member and extends through the disc 7 in the upper end of the support member, the upper end of the conduit being close to the inner surface 21 of the rotor top cover 12. It is arranged as follows.

The pulp to be filtered is fed into the device via the inlet connection 14, initially the pulp circulates tangentially in the pre-distribution feed chamber. The pre-distribution feed chamber simultaneously acts as a scrap catcher, where stones and other heavy particles are removed.

From the feed chamber the pulp flows into a ring-shaped groove 11 provided between the rotor 3 and the filtration drum 2, which acts as a filtration area. The accept matter passes from the filtration area 11 through the filtration surface 10 to the accept chamber 1.
Flows to 7. The pulp is discharged from the acceptance chamber via a discharge connection 20.

The rejects, ie, the portion of the valve flow that does not pass through the screen surface, terminates in the reject chamber 15. In the reject chamber, the reject material can be diluted by a diluent supplied through the opening 18 and is discharged through the evacuation connection.

Test results at several operational scales have shown that typical components in the lightweight rejects, such as plastics, remain on the reject side. For example, by employing a 0.45 mm slotted screen as the filtration surface, 85-95% of the plastic in a typical sulfate cellulose pulp can be removed. In this way, an accept product is produced in which the plastic content of the feed pulp stream is only 5-15%. U.S. Patent Nos. 4 and 6
The problem that led to No. 34,521 was how to separate plastics and other lightweight particles from the rejects to be recycled, as discussed above.

The solution is simple and effective. The lightweight rejects flow through the rotor bottom end 23 into the space 22 inside the rotor. Due to the high rotational speeds typical of the rotor, the pulp in the filtration space, the reject chamber, and the rotor interior space 22 is subjected to rotational motion, inducing the centrifugal force necessary to separate the lightweight rejects. A diluent liquid can be supplied into the reject chamber to regulate the concentration.

In the device according to the US patent, the lightweight rejects are collected in the rotor 3 in a space below the top cover 12, from where they are removed continuously or intermittently via a conduit 19. Two problems with the lightweight reject material collected when using the device according to the above-mentioned US patent are that the lightweight reject material that is separated contains a large amount of fibrous material that can be used well, and that the concentration of the reject material is high. If it is too long, the conduit 19 will easily become clogged.

The solution to the first problem is to dilute the reject material inside the rotor so that it has enough space for the lighter reject material to rise upward and separate from the fibrous particles. . The most effective method for dilution is to transfer the dilution liquid to the top cover 1 of the rotor 3.
2, so that the lightweight reject material continues to float on the liquid, and the coarser reject material, fiber bundles, etc. are washed out from the lightweight reject material, and the liquid flowing slowly downward removes the fiber bundles and nodular particles. This is done in such a way as to remove it. A solution to the second problem is to allow the diluent to flow slowly through the conduit 19 to the top of the rotor compartment which keeps the conduit clean. be. In order to regulate the flow of the diluent and the lightweight reject, the branch pipe 30 is provided with a valve device [31] and a discharge conduit 19 with a valve device 32. The use of the valve arrangement is such that the valve 32 is closed most of the time, and when the valve 31 is opened the diluent flows in the conduit 19 inside the rotor 3. After, for example, four hours, the valve 31 in the branch pipe 30 is closed and the valve 32 in the conduit 19 is opened, allowing the plastic etc. to flow away from inside the rotor 3.

After a few minutes, valve 32 is closed and valve 31 is opened so that the dilution process is resumed. In the operational scale test, branch pipe structure 3
The reductate discharged in conduit 19 without 0.31 contained 300-500 kg of fiber per day. Valve 3
According to the branch pipe 30 with structure No. 1 attached, the amount of fiber in the redirect material is 30 to 50 kg per day.
It declined to .

Of course, the pulp can also be partially diluted at the bottom end of the filtration zone by liquid fed in a dilution water ring. Openings can be provided in the rotor to feed the main part of the reject flow into the space inside the rotor where the lightweight rejects are separated by centrifugal force. The lightweight rejects flow into the space below the rotor top cover where they are diluted/washed and removed from there from time to time via a discharge conduit. The remaining rejiku small items will flow into the rejiku chamber,
From there the rejects are discharged through the opening.

The invention is not limited to the embodiments described above, as they are proposed and described by way of example only;
Several modifications may be made within the scope of protection defined by the claims. Thus,
It is possible to arrange a separate pipe in the bearing support member to introduce the diluent liquid inside the rotor compartment. The pipe may be disposed to extend into the vicinity of the rotor top cover, the pipe extending through the cylindrical wall of the bearing support member and between the bearing support member and the cylindrical inner surface of the rotor. It is also possible to arrange for the dilution liquid to be introduced into the ring-shaped compartment provided.

[Brief explanation of drawings]

FIG. 1 is a vertical step view of one embodiment of the invention. 2... Screen, 3... Rotor, 9... Outer surface of screen, 10... Inner surface of screen, 1
1... Filtration area, 17... Acceptance chamber, 1
4... Inlet opening, 15... Reject chamber, 1
9... Conduit, 12... Top cover, 21... Inner surface of said cover.

Claims (6)

[Claims] (1) A filtration device comprising a substantially vertical cylindrical screen and a closed outer surface thereof (9)
a rotor disposed coaxially inside the screen, the rotor and the inner surface (10) of the screen being bounded by the rotor and the outer surface of the screen defining a filtration area for the pulp; Surrounded Acceptance Chamber (17)
an inlet opening (14) for supplying the pulp to be filtered into the upper end of the filtration region; a redirect chamber (15) connected to the lower end of the filtration region; and a means for separating impurities from each other, wherein a conduit (19) for removing lightweight rejects is disposed inside the rotor (3), and an upper end of the conduit (19) is disposed inside the rotor (3). is the top cover of the rotor (1
2) in a filtration device located close to the inner surface (21) of the rotor, said reject being sufficiently low relative to said upper end space of the rotor to allow effective separation of lightweight reject material from fibrous material; A filtration device, characterized in that it is further provided with means for providing a diluent liquid in order to maintain the concentration of the substance. (2) In the screen according to claim 1, the means device is arranged in a bearing support member (5) disposed inside the rotor (3) near the top cover (12) of the rotor (3). A screen characterized in that it is a conduit arranged to extend. (3) In the screen according to claim 1, the means device is a conduit (19) that is also used for removing the lightweight rejects, and the conduit (19) is
19) is equipped with a valve device (32) for regulating the flow of lightweight rejects. (4) The screen according to claim 3, characterized in that the conduit (19) is provided with a branch pipe (30) for introducing a diluent into the conduit (19). Screen to do. (5) The screen according to claim 4, wherein the branch pipe (30) is provided with a valve device (31) for regulating the flow of the diluent liquid. . (6) A method for separating lightweight rejects from a redirect stream of a filtration device in the pulp and paper industry, the method comprising the steps of introducing the reject stream into the inside of a rotor of the filtration device; is circulated on the inner wall of the rotor, thus allowing light weight rejects to collect near the axis of the rotor, and introducing a diluent liquid near the top cover of the rotor to reduce the concentration of the rejects. and make a lightweight rigid material into a fiber bundle,
A method comprising the steps of cleaning out the slabs, knots, etc., and discharging the lightweight rejects from the vicinity of the rotor top cover.