JPH0418076B2 - - Google Patents

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 includes a primarily vertical cylindrical screen and a substantially cylindrical rotor concentrically disposed therein, the rotor and screen defining a filtration area for the pulp. . The device further includes an acceptance chamber surrounding the outer surface of the screen, an inlet for supplying pulp to be filtered into the upper end of the filtration region, and connected to the lower end of the filtration region. a redirect chamber and apparatus 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 a screen as described in US Pat. No. 3,363,759, the reject product also contains particles that can be separated by employing centrifugal force. The particles thus separated, whose specific gravity is lower than the average particle, ie, the specific gravity of the lightweight reject, 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 rejects in a simple manner. The reason for removing lightweight rejects, such as plastics, from the reject stream is that plastics and the like are extremely hazardous in the papermaking process. Rejects from the filtration system are returned to the filtration system, usually via a grinding system, 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, US Pat. No. 3,363,759. An improved version of the filtration device of the aforementioned patent has been modified to remove plastic and is disclosed in U.S. Pat. No. 3,912,622. In this improved version, the separation of light particles from the redirected pulp is carried out by making the pulp into a pulp, one end of which is fixed at the inlet end of the screen and the other end extending 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 movement of the rejected pulp, 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. Ru. To achieve efficient separation operations, the reduct flow must be abundant, but this reduces the capacity of the machine.

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 for feeding the pulp to be filtered into the upper end of said filtration area; , a redirect chamber connected to the lower end of said filtration zone, 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 described in U.S. Pat.
It is explained in more detail in No. 4634521.

One object of the present invention is the above-mentioned U.S. Pat. No. 4,634,521
Another object of the present invention is to improve the process for separating the lighter weight material from the reject material.

It has been found that it is important to reduce the amount of the 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% fibrous material that can be recycled back into the system.
This is because it contains %. The term further processing usually means separation sorting arrangements by filtration equipment and perhaps even cyclones to separate the lightweight reject material, often plastic, from the acceptable fibrous material. By using the improvements according to the invention, it is possible, under the most favorable circumstances, to discharge lightweight reject materials, which are primarily plastics, without recycling them to any further filtration step. is possible. 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. 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 rejected materials 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 providing 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.

Embodiment The main parts of the screen illustrated in FIG. 1 are a multi-compartment housing 1, a substantially cylindrical screen drum 2, and a substantially cylindrical rotor 3.
and shaft 4. The shaft is rotatably mounted inside the rotor by bearings 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. Disk 7
is secured to the upper end of the support member, and the shaft extends through the support member.

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 filtration area 11 into which the pulp to be filtered is fed. The upper end of the rotor is covered by a top cover 1
2, and the shaft is fixed within the cover.

The upper part of the housing consists of a feed chamber 13, which is provided with an inlet connection 14 for the pulp to be filtered.
Exhaust connection 16 in the lower part of the housing.
There is a redirect chamber 15 provided with. An upper end of the filtration region is connected to the feed chamber and a lower end is connected to the redirect chamber. An acceptance chamber 17 is provided outside the screen drum.

An inlet 18 for diluent liquid can be arranged in the redirect 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 at the inlet connection 14
The pulp is initially circulated tangentially within said feed chamber. The feed chamber simultaneously acts as a scoop catcher, in which stones and other heavy particles are removed.
From the feed chamber the pulp is transferred to the rotor 3
and into a ring-shaped groove 11 provided between the filtration drum 2, which acts as a filtration area. The accept matter flows from the filtration region 11 through the filtration surface 10 into the acceptance chamber 17 . Pulp is discharged from the acceptance chamber through connection 2.
It is discharged after passing through 0.

The rejected material, or the portion of the pulp stream that does not pass through the screen surface, terminates in the redirect 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.

According to test results at several operational scales,
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. An accept product is thus produced in which the plastic content of the feed pulp stream is only 5-15%. The problem that arose in U.S. Pat. No. 4,634,521 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 redirect chamber to regulate the concentration.

In the device according to the above-mentioned US patent, the above-mentioned light-weight reject object is attached to the top cover 1 within the rotor 3.
2 is collected in the space below, from which the conduit 1
9 continuously or intermittently. 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 direct the diluting liquid near the top cover 12 of the rotor 3 so that the lighter rejects remain suspended above the liquid and the coarser rejects, fiber bundles, etc. are washed away from the lighter rejects. The solution is to allow the liquid to slowly flow downward and remove the fiber bundles and nodular particles. 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. It is. In order to regulate the flow of the diluent as well as the light reject, the branch pipe 30 is provided with a discharge conduit 19 having a valve device 31 and 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 plastics 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 restarted. In operational scale tests, the rejected material discharged in conduit 19 without branch pipe structures 30, 31 contained 300-500 kg of fiber per day. According to the branch pipe 30 with the structure of the valve 31 installed, the amount of fiber in the rejected material was reduced to 30-50 kg per day.

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. Note that the remaining reject material flows into the redirect chamber, from where it is discharged through the opening.

The invention is not limited to the embodiments described above, which are proposed and described by way of example only, and therefore may be subject to certain modifications within the scope of protection defined by the claims. It is possible to make an example. It is thus 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 a ring-shaped compartment provided in the tube.

[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, 11... Filtration area, 17... Accept chamber, 14... Inlet opening, 15... Reject Chamber, 19... Conduit, 12... Top cover, 2
1...Inner surface of the same cover.

Claims (1)

Claims: 1. A filtration device comprising a substantially vertical cylindrical screen and a rotor coaxially disposed inside the screen and its closed outer surface 9, the rotor and the screen comprising: The inner surface 10 of the rotor defines a filtration area for the pulp, and the acceptance chamber 17 is surrounded by the outer surface of said screen and the pulp to be filtered is placed above said filtration area. A filtration device comprising an inlet opening 14 for feeding into the end, a redirect chamber 15 connected to the lower end of the filtration region, and means for separating heavy and light impurities from each other. , a conduit 19 for removing lightweight rejects is disposed inside the rotor 3, the upper end of the conduit being provided with a filtration device located near the inner surface 21 of the top cover 12 of the rotor. , means for providing a diluent liquid to the upper end space of the rotor to maintain the concentration of the lightweight reject material low enough to effectively separate it from the fibrous material; A filtration device further comprising: 2. In the filtration device according to claim 1, the means device is a conduit arranged to extend inside the bearing support member 5 arranged near the top cover 12 of the rotor 3 inside the rotor 3. A filtration device characterized by: 3. In the filtration device according to claim 1, the means device is a conduit 19 which is also used to remove the lightweight rejects,
A filtration device characterized in that the conduit 19 is provided with a valve device 32 for regulating the flow of the lightweight reject material. 4. The filtration device according to claim 3, wherein the conduit 19 is provided with a branch pipe 30 for introducing a diluent into the conduit 19. 5. The filtration device 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 the rotor of the filtration device, and the steps of introducing the reject stream into the rotor of the filtration device. circulating 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; A step of cleaning out the lightweight rigid material from fiber bundles, slives, knots, etc.
ejecting the lightweight reject material from the vicinity of the rotor top cover.