JP2006283209A - Screen apparatus and method for producing recycled pulp using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and continuously remove foreign matters such as plastic strings, etc., from a raw material liquid obtained by dissolving wastepaper, pulp, etc., in a liquid. <P>SOLUTION: The screen apparatus for removing foreign matters in a liquid is equipped with a cylindrical first screen 1 furnished with through holes 11 having 1-4 mm hole diameters on a peripheral surface, a rotator coaxially installed in the first screen 1 in the inside of the first screen 1 and protruding ridges 12 extended at an angle crossing the rotary direction of the rotator 2 on the inner peripheral surface of the first screen 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a screen device and a method for producing regenerated pulp using the same.

2. Description of the Related Art Conventionally, as a method for producing recycled pulp by deinking and recycling printed printing paper, a method having steps of disaggregation, dust removal, bleaching, dispersion, deinking, and washing is known.
Printing waste paper such as newspaper or magazine used as a raw material is often subjected to a disaggregation process in a state of being bound by a poly string or the like, but foreign matters such as a poly string are separated and removed in a dust removal process after disaggregation.

As a method for separating and removing the poly string and the like from the slurry after disaggregation, a method using a screen having a passage hole having a predetermined size is generally used. For example, by rotating the rotor while supplying slurry to the gap between the cylindrical screen and the rotor provided coaxially with the screen, the processed material that has passed through the passage hole of the screen cannot pass through the passage hole. There is a method of continuously separating foreign substances (for example, Patent Document 1 below).
In addition, a trap such as barbed wire, chain, or iron lattice is installed in a treatment tank in which the slurry after the used paper is disaggregated. There is also a method of removing the etc.
JP 2003-1933885 A

However, in the conventional method using a cylindrical screen and a rotor, there is a problem that poly string is easily entangled with the rotor, the screen needs to be washed frequently, and long-term continuous operation cannot be performed.
On the other hand, in the method using a trap such as a chain, a relatively long poly string is easy to remove, but there is a problem that foreign matters such as a poly string finely cut during the disaggregation process cannot be removed.
Further, in Patent Document 1, a method has been proposed in which long fiber-based foreign substances are prevented from binding in the apparatus or forming a large lump by providing protrusions on the end face of the rotor, but still insufficient. Therefore, there is a demand for a method that can remove foreign matters more efficiently and can operate continuously for a longer time.

  The present invention has been made in view of the above circumstances, and uses a screen device capable of efficiently and continuously removing foreign matter such as poly string from a raw material liquid obtained by dissolving waste paper or pulp in a liquid. An object of the present invention is to provide a method for producing regenerated pulp.

In order to solve the above-mentioned problems, a screen device of the present invention is a screen device for removing foreign substances in a liquid, and a cylindrical first screen provided with a passage hole having a hole diameter of 1 mm to 4 mm on a peripheral surface thereof. A rotating body provided coaxially with the first screen on the inner side or the outer side of the first screen, and the rotation on the circumferential surface of the first screen facing the rotating body. A ridge extending at an angle crossing the rotation direction of the body is provided.
The method for producing regenerated pulp of the present invention is a method for producing regenerated pulp through a screening step for removing foreign matter in a raw material liquid in which paper is dispersed in a liquid, wherein the screening step is performed according to the present invention. A first step of removing foreign matter using a screen device, and a second step of removing foreign matter using a second screen having a slit having a slit width of 0.08 mm to 0.25 mm after the first step. It has the process.

According to the screen device of the present invention, foreign substances in the liquid can be separated and removed more efficiently. Moreover, since the clogging of the screen passage hole due to the foreign matter and the entanglement with the rotating body can be reduced, it is possible to prevent an overload of the rotating body to the driving device. In addition, the continuous processing period can be extended.
According to the method for producing regenerated pulp of the present invention, in the screening step, foreign substances in the raw material liquid in which paper is dispersed in the liquid can be separated and removed more efficiently. Therefore, the foreign material in the raw material liquid provided for a post process can be reduced, and the quality of recycled pulp can be improved. Further, in the screen device, clogging of the screen passage hole due to foreign matter and entanglement with the rotating body are reduced, so that overloading of the rotating body to the driving device is prevented, and the continuous processing period can be prolonged. .

First, a screen device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a screen device according to the present embodiment, FIG. 2 is a perspective view illustrating an example of a first screen, and FIG. 3 is a plan view of the first screen and a rotating body.
The screen device of the present embodiment includes a cylindrical first screen 1, a substantially cylindrical rotary body 2 provided inside the first screen 1, and the first screen 1 and the rotary body 2. A cylindrical housing 3 that accommodates it is generally configured. A shaft 29 for transmitting a rotational force from a power source (such as an electric motor) is attached to one end face 21b of both end faces 21a and 21b of the rotating body 2.
In the present embodiment, the shaft 29, the rotating body 2, the first screen 1, and the housing 3 are provided coaxially (so that the central axes coincide).

  Spaces S1 and S2 in which the first screen 1 and the rotating body 2 do not exist are formed at both ends in the axial direction in the housing 3. A raw material inlet 35 is formed so as to communicate with the space S1 on the side where the shaft 29 is not disposed among the spaces S1 and S2 at both ends, and a foreign substance outlet 38 so as to communicate with the space S2 where the shaft 29 is provided. Is formed. Further, a processed product outlet 37 is provided so as to communicate with a space between the outer peripheral surface of the first screen 1 and the inner peripheral surface of the housing 3.

  Steps 25 are provided on the circumferential surface of the rotating body 2 at equal intervals in the circumferential direction, and the shape of the radius of the rotating body 2 gradually increases in the rotation direction and then decreases rapidly at the step 25. Is formed. The raw material can be moved by the step portion 25.

Of the both end faces 21a and 21b of the rotator 2, a rotator-side protrusion 22 projects from the end face 21b on the side where the shaft 29 is provided. A housing-side protrusion 32 is also provided on the inner surface of the end face 31 b facing the rotating body-side protrusion 22, of the both end faces 31 a and 31 b of the housing 3.
These rotating body side protrusions 22 and housing side protrusions 32 have sharp corners for cutting foreign matter such as poly strings that come into contact therewith.

The number of the rotor-side protrusions 22 and the housing-side protrusions 32, the angle of a sharp angle, and the like may be arbitrary. However, since the rotor 2 rotates, it is also important to consider the weight balance of the rotor-side protrusions 22. A plurality of the rotator-side protrusions 22 may be arranged, for example, adopting a method of arranging several pieces on a plurality of circles concentrically around the axis of the rotator 2 (center of the shaft 29). Can do.
The size and shape of the rotator-side protrusion 22 does not serve as a resistance to rotation of the rotator 2, and is preferably formed thin in the radial direction so that foreign matter can be easily cut, for example, about 10 mm. The circumferential dimension of the rotator-side protrusion 22 may be sufficient to prevent the rotator-side protrusion 22 from falling off the rotator 2 according to the amount of protrusion of the rotator-side protrusion 22 in the axial direction. That's fine. The amount of protrusion of the rotor-side protrusion 22 in the axial direction is preferably about 5 to 100 mm, more preferably about 20 to 50 mm, although it depends on the size of the space S2. If the protruding amount of the rotating body-side protrusion 22 is too small, the cutting effect of the foreign matter is reduced. Conversely, if the protruding amount is too large, the rotational resistance of the rotating body 2 increases, which is not preferable. In addition, since the rotor-side protrusion 22 vigorously contacts foreign matter, it is also effective to carry out a hardening build-up such as a stellite build-up or a hardening treatment on the rotating tip side to prevent wear.
On the other hand, the housing-side protrusion 32 is not particularly limited because there is no problem of weight balance, and there are few restrictions on the mounting arrangement, angle, size, shape and the like.
In the present embodiment, although not shown in the drawing, a plurality of the rotor-side protrusions 22 are provided on a plurality of concentric circles centering on the shaft 29, and the housing-side protrusion 32 is more than the rotor-side protrusion 22. It is formed slightly larger and one is provided.

As shown in FIGS. 2 and 3, the first screen 1 has a hollow cylindrical shape and is provided with a large number of passage holes 11 on the peripheral surface.
Further, on the peripheral surface facing the rotating body of the first screen 1, in this embodiment, the ridges 12 are provided on the inner peripheral surface. The screening zone 10 formed between the rotating body 2 and the first screen 1 disposed outside the rotating body 2 is partially narrowed by the ridges 12, and as a result, stays in the screening zone 10. Poly string etc. are cut or loosened.
The size of the clearance (gap) between the inner peripheral surface of the first screen 1 and the rotating body 2 at the portion where the ridges 12 are not provided is preferably about 0.1 to 40 mm at C1 at the narrowest point. About 15 to 25 mm is more preferable. C2 is preferably about 10 to 150 mm, and more preferably about 10 to 100 mm.

A fixed end surface 13 for fixing the first screen 1 to the housing 3 is provided at the end of the first screen 1.
On the outer peripheral surface of the first screen 1, a plurality of annular ribs 14 for increasing the strength of the peripheral surface are provided at equal intervals in the axial direction.

The size of the passage hole 11 is preferably a hole diameter of 1.0 to 4.0 mm, more preferably 1.0 mm to 3.0 mm, and still more preferably 1.5 mm to 2.5 mm. If the pore diameter is in the above range, the pulp fiber can easily pass through and the poly string can be separated efficiently. In the present invention, the “hole diameter of the passage hole” refers to the largest diameter passing through the center of the passage hole. When the passage hole 11 is a round hole, the hole diameter corresponds to the diameter.
The shape of the passage hole 11 is preferably a round hole in order to efficiently separate and remove the poly string.

The planar shape of the ridges 12 is not particularly limited as long as the length direction of the ridges 12 is an angle that intersects the rotation direction of the rotating body 2. In order to efficiently cut or loosen the poly string, the angle between the length direction of the ridge 12 and the rotation direction of the rotating body 2 is preferably about 30 to 90 °, more preferably about 45 to 90 °. preferable.
In the present embodiment, the linear ridges 12 are provided so as to be parallel to the rotation axis direction of the rotating body 2, that is, to be perpendicular to the rotating direction of the rotating body 2. As a modification of the shape of the ridges 12, for example, a spiral shape may be used, and a V shape (a square shape) as shown in FIG. 7 may be used.

The shape and dimensions of the cross section obtained by cutting the ridge 12 with a plane perpendicular to the length direction are not particularly limited. A cross-sectional shape and a cross-sectional dimension that provide strength sufficient to prevent the protrusion 12 from falling off the first screen 1 due to the applied pressure during processing are preferable. In this embodiment, the cross-sectional shape of the ridge 12 is a rectangle.
If the width of the ridges 12 in the circumferential direction of the first screen 1 is too small, the effect of cutting or loosening the poly string or the like cannot be obtained sufficiently, and if the width is too large, the rotational resistance of the rotating body 2 increases. This is not preferable. Therefore, the width of the ridge 12 is preferably about 2 to 20 mm, and more preferably about 3 to 15 mm.

  The height of the ridge 12 in the radial direction of the first screen 1 determines the size of the clearance (gap) C3 between the ridge 12 and the rotating body 2. If the clearance C3 between the ridges 12 and the rotator 2 is too large, the effect of cutting or loosening the poly string or the like cannot be obtained sufficiently, and if the clearance C3 is too small, the rotational resistance of the rotator 2 is increased. Absent. The clearance C3 is preferably in the range of 0.1 to 30 mm, and more preferably in the range of 0.1 to 15 mm.

In the direction of the rotation axis of the rotator 2, the ridges 12 may not be continuous and may be provided intermittently. It is preferable that it is continuous from the point of the effect of cutting or loosening the poly string or the like.
The length of the portion where the ridge 12 is provided in the rotation axis direction of the rotating body 2 (when the ridge is provided intermittently, the total length of the portions provided) is the first The length of the screen 1 may be the same as or shorter than this. If the length is too short, a sufficient effect of cutting or loosening the poly string or the like cannot be obtained. Therefore, the length of the portion of the entire length in the axial direction of the rotating body 2 where the ridges 12 are provided is 80%. The above is preferable, and 95% or more is more preferable.

The number of ridges 12 in the circumferential direction of the first screen 1 depends on the size of the diameter of the first screen 1 but is of a size that is usually used industrially (diameter is about 300 to 2000 mm). If it is a thing, 1-6 are desirable. More desirably, the number is 2 to 4. If the number of the ridges 12 is too large, the poly string becomes too fine and foreign matter passing through the screen increases, so that the removal efficiency decreases.
In the case where a plurality of ridges 12 are provided, the interval in the circumferential direction of the first screen 1 is arbitrary, but is preferably provided at equal intervals.

  In the screen apparatus having such a configuration, the raw material liquid supplied from the raw material inlet 35 enters the screening zone 10 formed between the rotating rotating body 2 and the first screen 1 arranged outside thereof, The foreign matter is sorted by The processed material that has passed through the passage hole 11 of the first screen 1 by the rotation of the rotating body 2 is taken out from the processed material outlet 37. The foreign matter that cannot pass through the passage hole 11 of the first screen 1 is separated from the processed material, reaches the end surface 21b portion of the rotating body 2 while rotating, and is discharged from the foreign matter outlet 38 through the space S2.

  According to the screen device of the present embodiment, the ridges 12 are provided on the inner peripheral surface of the first screen 1, and this has the effect of cutting or loosening foreign matters such as poly strings in the raw material liquid. can get. Thereby, the removal efficiency of a foreign material improves. Further, the clogging of the screen passage hole due to the foreign matter and the entanglement with the rotating body are reduced, and the continuous processing period can be prolonged.

Hereinafter, a second embodiment of the screen device of the present invention will be described with reference to FIGS. FIG. 4 is a schematic configuration diagram of the screen device of the present embodiment, FIG. 5 is a perspective view showing an example of the first screen, and FIG. 6 is a plan view of the first screen and the rotating body.
The screen device according to the present embodiment includes a cylindrical first screen 50, a rotating body 60 provided outside the first screen 50, and a cylindrical type that accommodates the first screen 50 and the rotating body 60. The housing 70 is generally configured. A shaft 69 that transmits rotational force from a power source (such as an electric motor) is attached to one end of the rotating body 60.
In the present embodiment, the shaft 69, the rotating body 60, the first screen 50, and the housing 70 are provided coaxially.

The rotating body 60 is provided with a plurality of thin plate-like foils 61 extending in the rotation axis direction and arranged at equal intervals in the circumferential direction, and a plurality of locations in the length direction of the foil 61 are the inner peripheral surface of the annular member 62. The peripheral surface of the rotator 60 has a lattice shape. The thickness of the foil 61 in the radial direction of the rotating body 60 gradually decreases from the front to the rear in the rotational direction.
The width of each foil 61 in the circumferential direction is not particularly limited, but is preferably about 30 to 200 mm, and more preferably about 50 to 150 mm.

  A raw material inlet (not shown) communicating with the space between the outer peripheral surface of the first screen 50 and the rotating body 60 is provided on the peripheral surface of the housing 70, and on the substantially opposite side across the raw material inlet and the rotating body 60. Is provided with a foreign matter outlet (not shown) communicating with the space between the outer peripheral surface of the first screen 50 and the rotating body 60. Further, a processed product outlet 77 is provided so as to communicate with the space inside the first screen 50.

As shown in FIGS. 5 and 6, the first screen 50 has a hollow cylindrical shape, and a large number of passage holes 11 are provided on the peripheral surface.
Further, on the peripheral surface facing the rotating body of the first screen 1, in the present embodiment, a ridge 52 is provided on the outer peripheral surface. The clearance between the foil 61 of the rotating body 60 rotating by the ridges 52 and the first screen 50 disposed inside thereof is partially narrowed, and foreign matters such as poly strings pass through the clearance. When it is cut, it will be cut or loosened.
The size of the clearance (gap) C4 between the outer peripheral surface of the first screen 50 and the foil 61 of the rotating body 60 in a portion where the ridges 52 are not provided is about 1 to 40 mm at the narrowest place. Preferably, about 1 to 25 mm is more preferable.

A fixed end surface 53 for fixing the first screen 50 to the housing 70 is provided at the end of the first screen 50.
On the inner peripheral surface of the first screen 50, a plurality of annular ribs 54 for increasing the strength of the peripheral surface are provided at equal intervals in the axial direction.

The size and shape of the passage hole 11 are the same as those in the first embodiment.
The planar shape, angle, cross-sectional shape, width, length, and number in the circumferential direction of the ridges 52 are the same as those in the first embodiment.
The height of the ridge 52 in the radial direction of the first screen 50 determines the size of the clearance (gap) C5 between the ridge 52 and the rotating body 60 (foil 61). If the clearance C5 between the ridge 52 and the foil 61 is too large, the effect of cutting or loosening the poly string or the like cannot be obtained sufficiently, and if the clearance C5 is too small, the rotational resistance of the rotating body 2 increases, which is not preferable. . The clearance C5 is preferably in the range of 0.1 to 30 mm, and more preferably in the range of 0.1 to 15 mm.

  In the screen apparatus having such a configuration, the raw material liquid supplied from the raw material inlet enters a screening zone formed between the rotating body 60 (foil 61) that rotates and the first screen 50 disposed inside thereof. Here, foreign matter is sorted out. The processed material that has passed through the passage hole 11 of the first screen 50 by the rotation of the rotating body 60 is taken out from the processed material outlet 77. The foreign matter that cannot pass through the passage hole 11 of the first screen 50 is separated from the processed material, moves with the rotation of the rotating body 60, and is discharged from the foreign matter outlet provided on the opposite side of the raw material inlet 75.

  According to the screen device of the present embodiment, the ridges 52 are provided on the outer peripheral surface of the first screen 1, thereby obtaining an effect of cutting or loosening foreign matters such as poly strings in the raw material liquid. It is done. Thereby, the removal efficiency of a foreign material improves. Further, the clogging of the screen passage hole due to the foreign matter and the entanglement with the rotating body are reduced, and the continuous processing period can be prolonged.

FIG. 7 is a perspective view showing a modification of the first screen 50 in the second embodiment.
This example is different from the second embodiment in that the protrusions 55 provided on the outer peripheral surface of the first screen 50 are provided in a substantially square shape. The rotating direction of the rotating body 60 in this example can be a direction from the substantially square top 55A to the bottom 55B as indicated by an arrow in the figure, for example, but it can also be used in the opposite direction.
90-30 degrees is preferable and, as for the angle which the ridge 55 in this example makes with the rotation direction of the rotary body 60, 90-45 degrees is more preferable.

Also in this example, the same effect as the second embodiment can be obtained.
In particular, since the ridges 53 are provided in a substantially square shape, in the case of the two inlets in which the raw material liquid is supplied from both ends in the rotation axis direction, foreign matter such as concentrated poly string is more efficiently used. Effects such as being cut or loosened can be obtained.
The ridges may be provided obliquely at a predetermined angle with respect to the rotation direction, or may be spiral, and the flow of the raw material liquid or concentrated foreign matter is changed according to the convex shape and rotation direction to improve work efficiency. Can be made.

Hereinafter, an embodiment of a method for producing recycled pulp according to the present invention will be described.
The raw material liquid in the present invention is a slurry in which paper is dispersed in a liquid, and is preferably a slurry obtained by disaggregating used printing paper.
Examples of used printed paper include (1) newspaper, (2) finely coated paper, (3) high ash coated paper, (4) non-coated paper, and other waste paper containing 7 to 35% by mass of ash. can give. Among these, the effects of the present invention remarkably appear in recovered newspaper waste paper, magazine waste paper, and the like that are bound by a poly string discharged from a general household.

-Disaggregation process (Process A)
It is preferable to perform a disaggregation step before the screening step.
A known method can be used for the disaggregation step, and for example, it can be performed as follows.
First, a pulp as a raw material, preferably used printing paper, and diluted water are added so as to have a solid content concentration of 12 to 18% by mass, and disaggregated and dispersed to obtain a pulp slurry (raw material liquid).
At the time of disaggregation, the chemical (sodium hydroxide) is added in an amount of 0 to 1.0% by mass, preferably 0 to 0% by mass with respect to the mass of the pulp (the mass of the No. 2 qualitative filter paper receiving solid content, hereinafter sometimes referred to simply as pulp). You may add 0.5 mass%. Further, 0 to 0.5 mass%, preferably 0.03 to 0.3 mass% of the deinking agent may be added to the pulp. The deinking agent is preferably one having strong permeability to pulp fibers and strong ink peelability. Specific examples of deinking agents with strong ink peeling properties include higher alcohol-based deinking agents such as DI-7020, DI-7030, DI-767 manufactured by Kao Corporation, and Nisshin Chemical Laboratory. DIA-Z-100, DIA-Z-5000 manufactured by Co., Ltd., Neoscore FW-780, Neoscore FW-790, Neoscore FW-795, Neoscore FW-795, FT-466, FT-467, FT manufactured by Toho Chemical Co., Ltd. -470, FT-487, BB agent, Daiichi Kogyo Seiyaku Co., Ltd., Daihope 940, Daihope 960, Nikka Corporation Lipobright DP-810, and the like.
The disaggregation time is preferably 10 to 30 minutes, more preferably 10 to 25 minutes, and still more preferably 10 to 18 minutes. The disaggregation temperature is preferably 10 to 50 ° C, more preferably 30 to 50 ° C.

  It is preferable that the pulp slurry obtained in the disaggregation process is diluted until the solid concentration becomes 5% by mass or less, and then the next screening process is performed. For dilution, it is a good idea to use treated water in the deinking process and cleaning process described later, since the yield is improved.

・ Screening process (process B)
In the screening step, a first step (hereinafter also referred to as B1 step) for removing foreign matters in the pulp slurry (raw material liquid) using the screen device according to the present invention, and the first step (B1 step). A second step (hereinafter also referred to as B2 step) of removing foreign matters is performed on the processed product obtained by using a second screen having a slit having a slit width of 0.08 mm to 0.25 mm.
The steps B1 and B2 do not need to be continuous unless the order is changed. Moreover, you may combine the process process by a cleaner and may combine another process process.

In the step B1, it is preferable to use the screen device of the first embodiment or the second embodiment.
The peripheral speed (circumferential speed) of the rotating body 2 (60) in step B1 is preferably 5 m / sec to 25 m / sec. More desirably, it is 10 m / second to 20 m / second.
The screen device of the present invention has a mechanism for cutting a poly string or the like inside, so that the removal efficiency is good even if the peripheral speed of the rotating body is relatively slow, and the poly string is discharged to the heel side without any problem. . When the peripheral speed of the rotating body is less than 5 m / second and 25 m / second or more, the removal efficiency is lowered.

Moreover, in the B1 step, it is desirable that the flow velocity of the pulp slurry (raw material liquid) in the passage hole 11 of the first screen 1 (50) is 0.2 m / sec to 3.0 m / sec. More desirably, it is 0.2 m / second to 2.0 m / second. Here, the passing flow velocity is the discharge amount per unit time (unit: m ³ / sec) of the processed material discharged through the first screen 1 (50). 50) divided by the opening area (total area of passage holes 11, unit; m ² ).
Since the screen device of the present invention has a mechanism for cutting the poly string inside the screen, the removal efficiency is good even if the flow velocity through the screen is relatively fast, and the poly string is discharged to the heel side without any problem. If it is less than 0.2 m / sec and 3.0 m / sec or more, the removal efficiency decreases.
The passage flow rate in the passage hole 11 can be controlled by the viscosity of the pulp slurry (raw material liquid).

B2 process can be implemented using the well-known slit screen (2nd screen) provided with the slit of a predetermined | prescribed magnitude | size.
In order to efficiently separate and remove foreign matters such as fine poly string, which are not removed in the B1 step and are discharged from the screen apparatus in the B1 step, and adhesive substances which are difficult to remove in the round hole, The slit width is desirably 0.08 mm to 0.25 mm, more desirably 0.08 mm to 0.20 mm, and still more desirably 0.10 mm to 0.15 mm. If the slit width is less than 0.08 mm, the pulp throughput will decrease, and if it exceeds 0.25 mm, the removal efficiency will decrease.
The shape of the second screen (slit screen) is not particularly limited, and a cutting type, a bar type in which bars having a fixed shape are continuously arranged, or the like can be appropriately used.

・ Bleaching process (C process)
It is preferable to provide a bleaching step for bleaching the pulp slurry that has undergone the screening step.
The bleaching process is a process of whitening pulp using chemicals. Generally, hydrogen peroxide, hydrosulfide (sodium dithionite), thiourea dioxide, hypo (sodium thiosulfate), etc. are used for bleaching waste paper. used. Hydrogen peroxide is preferably used.
When bleaching with hydrogen peroxide, hydrogen peroxide is 0.5 to 4.0% by mass with respect to the pulp, and caustic soda (sodium hydroxide) is 1.5 to 3.0% by mass with respect to the pulp. , And sodium silicate (sodium silicate) is preferably added in an amount of 0.5 to 1.0 mass% (as NaOH) with respect to the pulp. The bleaching time is preferably 1 to 4 hours. The solid content concentration of the pulp slurry subjected to the bleaching step is preferably 20 to 35% by mass. The bleaching temperature is preferably 50 to 75 ° C.

・ Dispersing process (D process)
It is preferable to carry out a dispersion step after the bleaching step. A dispersion | distribution process is a process of peeling and disperse | distributing ink from a fiber with a disperser.
The solid content concentration of the pulp slurry subjected to the disperser treatment is preferably 20 to 50% by mass. The treatment temperature is preferably 40 to 90 ° C.

・ Deinking process (E process)
It is preferable to perform a deinking process after the dispersing process.
The deinking process is a process in which the pulp slurry to which the deinking agent is added is supplied to a flowator (OK type flowtater), and the ink is adsorbed to air to remove the ink out of the system. The solid content concentration of the pulp slurry used for the floatator is preferably 0.7 to 1.5% by mass. The flotator treatment temperature is preferably 10 to 50 ° C, more preferably 30 to 45 ° C.
As a deinking agent, there is a deinking agent of fatty acid or fatty acid derivative type as a deinking agent having strong ink aggregating property. For example, in the case of fatty acid, DI-254 (oleic acid) manufactured by Kao Corporation. And K-4004-D manufactured by Daiichi Kogyo Seiyaku Co., Ltd. In the case of a fatty acid derivative, DI-1120 and DI-1050 manufactured by Kao Corporation, DIY-23543 manufactured by Nisshin Chemical Laboratory Co., Ltd., and Paper Aid manufactured by Daiichi Kogyo Seiyaku Co., Ltd. W etc.
When using a deinking agent having strong ink cohesion, it is preferably added immediately before the disperser treatment (dispersing step). In this case, the addition amount of the deinking agent is preferably 0.5% by mass or less with respect to the pulp. More preferably, it is 0.04-0.10 mass%.
If the deinking agent can be uniformly mixed in the pulp slurry, the deinking agent may be added in the bleaching step.

-Cleaning dehydration process It is preferable to perform a cleaning dehydration process after the deinking process. This step is a step of washing and dewatering fine ink that could not be removed with a floatator. A pulp slurry having a solid content concentration of 0.6 to 1.5 mass% was washed with fresh water, and a solid content concentration of 15 to 35 mass%. Dehydrate until%.
As the cleaning device, a disc thickener, a valveless filter, a DD washer, or the like can be used.

  In the middle of the screening process and the bleaching process, a washing and dehydration treatment may be provided as appropriate for the purpose of removing ash in the pulp slurry. By doing so, the addition rate of the bleaching agent and deinking agent used in the latter stage can be suppressed, which is effective. As the cleaning device, a fall washer (Eiko Machine Co., Ltd.), a DNT washer (Aikawa Tekko Co., Ltd.), an extractor, or the like can be used.

  According to the method for producing recycled pulp of the present embodiment, in the B1 step, the poly string or the like in the raw material liquid is formed by the ridges 12 (52, 55) provided on the peripheral surface of the first screen 1 (50). The foreign material is cut or loosened. Of the poly string or the like that is cut or loosened in this way, a large one is discharged from the foreign matter outlet of the screen device without being entangled with the rotating body, and a fine one passes through the passage hole 1. Fine foreign matter that has passed through the passage hole 11 of the first screen 1 (50) is efficiently separated and removed in the B2 step using a slit screen. Therefore, since the processed material from which foreign matters have been highly removed is used in a subsequent process, it is possible to produce a high-quality recycled pulp with less foreign matter such as poly string. Moreover, the continuous operation time of B1 process is prolonged and manufacturing efficiency can be improved.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
In the following Examples and Comparative Examples, unless otherwise specified, the raw material concentration is the solid content concentration including ash, and the chemical addition rate is mass%.

The quality of product pulp (regenerated pulp) obtained in the following examples and comparative examples was evaluated by the following method.
(1) Measuring method of poly string First, 100BDg of regenerated pulp was disaggregated at a solid content concentration of 1% by mass, and then the obtained pulp slurry was screened with a large Gozam screen (manufactured by Kumagaya Rikyu Kogyo Co., Ltd.). Treated with running water at a treatment speed of 30 L / m. A 50 mesh screen was used as the screen, and the treatment time was 15 minutes.
Subsequently, the bleached softwood pulp was added to the residue after the screen treatment so as to be 10 BDg / m ² , processed into a sheet shape with a square handmade sheet machine, and then dried with a rotary dryer.
The number and length of poly string having a length of 1.0 mm or more contained in the sheet thus obtained were measured while checking with a palpation needle. The unit was number: pieces / 100 BDg, and length: mm / piece (average value).

(2) Adhesive measurement method First, 100BDg of regenerated pulp was disaggregated at a solid content concentration of 1% by mass, and the obtained pulp slurry was screened at a large gozam screen (Kumaya Riki Kogyo Co., Ltd.) with a screen processing speed of 30L. / M of running water. A slit screen having a slit width of 0.15 mm was used as the screen, and the treatment time was 7 minutes.
Next, bleached softwood pulp was added to the residue after the screen treatment so as to be 10 BDg / m ² , processed into a sheet shape with a square handsheet sheet machine, and then dried with a rotary dryer.
The number and area of adhesives having a size of 0.08 mm ² or more contained in the sheet thus obtained were measured while checking with a palpation needle. The unit was number: pieces / 100 BDg, and area: mm ² / piece (average value).

(3) Continuous operation time As one of the indexes showing the effect of the present invention, the time (number of days) in which the B process can be operated continuously without washing the screen was measured.

Example 1
Devices other than the screen device according to the present invention used a deinked pulp manufacturing facility for finished pulp 120ADT / D of Oji Paper Co., Ltd. Kasugai Mill.

[Screen device]
As the screen device used in the B1 process, an apparatus having the configuration of the first embodiment shown in FIGS. Specifically, a screen basket (cylindrical first screen) of S-screen S-32A type (manufactured by Mitsubishi Heavy Industries, Ltd.) was changed to one provided with ridges 12 and used. In addition, the rotating body side protrusion 22 and the housing side protrusion 32 are not provided in this screen basket.

As for the rotary body 2 of this apparatus, the step part 25 is provided in four places of the surrounding surface.
The inner diameter of the first screen 1 was 810 mm (32 inches), and the passage hole 11 on the peripheral surface was a round hole having a diameter of 2.2 mm. On the inner peripheral surface of the first screen 1, a ridge that extends in parallel with the rotation axis direction and has the same length as the first screen 1 in the rotation axis direction, a height of 6 mm, and a width of 9 mm. Two 12 were provided at equal intervals in the circumferential direction.
In the portion of the first screen 1 where the ridges 12 are not present, the minimum clearance C1 between the first screen 1 and the rotator 2 is 13 mm, and the minimum clearance C3 between the ridges 12 and the rotator 2 is 7 mm.

[Manufacture of recycled pulp]
The raw material of waste paper (poly string and poly film content: about 2% by mass) mainly composed of newsprint including bundling string (poly string) and magazine magazines including films is charged to the pulper, and the solid content concentration is 15% by mass. Dilution water was added so that Further, 0.3% by mass of sodium hydroxide with respect to the solid content and 0.15% by mass of a higher alcohol deinking agent (manufactured by Kao Corporation, DI-7020) with respect to the solid content were added, and the disaggregation time was 15 minutes. The disaggregation temperature was 35 ° C. (step A).
The pulp slurry obtained after disaggregation was diluted to a solid content concentration of 3.6% by mass and subjected to a screen treatment step (Step B1).

The B1 step was performed under the conditions that the peripheral speed of the rotating body 2 was 16 m / sec and the flow velocity of the raw material liquid in the passage hole of the first screen was 1.5 m / sec.
The processed product obtained in the B1 step was subjected to the B2 step. B2 process was performed using the screen apparatus (Product name; GF-1000 type | mold, Aikawa Tekko Co., Ltd. product) provided with the bar-type slit screen whose screen slit width is 0.15 mm.
The processing conditions for the B2 step were a peripheral speed of 15 m / sec and a passing flow velocity of 0.5 m / sec.

  The pulp slurry obtained after the B2 step was subjected to a bleaching treatment in an existing deinked pulp manufacturing facility (C step). As for the bleaching conditions, the hydrogen peroxide addition rate was 3.0% by mass with respect to the pulp (solid content), the sodium hydroxide addition rate was 2.3% by mass with respect to the pulp, and the sodium silicate addition rate was 0 with respect to the pulp. 0.7% by mass (in terms of sodium hydroxide), pulp concentration (solid content concentration) was about 28% by mass, bleaching time 2 hours 30 minutes, and bleaching temperature 65 ° C.

Subsequently, the bleached pulp slurry was subjected to a dispersion treatment (step D). The pulp concentration in the disperser treatment was 28% by mass, and the treatment temperature was 65 ° C.
Subsequently, a deinking process (E process) was performed. The deinking conditions were as follows: the addition rate of the special fatty acid derivative (Kao Corporation, DI-1120) was 0.20% by mass with respect to the pulp (solid content), the solid content concentration was 1.2% by mass, and the The rotator treatment temperature was 42 ° C., and the treatment time was 20 minutes.
Thereafter, washing and dehydration treatment (step F) was performed with a disk thickener to obtain a regenerated pulp having a solid content concentration of 10% by mass.
The number and length of the poly string of the obtained recycled pulp, the number and area of the stickies, and the continuous operation time of the dust removal process (B process) were measured.

(Example 2)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the size of the round hole of the first screen 1 was changed to 1.6 mmφ.

(Example 3)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the size of the round hole of the first screen 1 was changed to 3.5 mmφ.

Example 4
In Example 1, the shape of the ridges on the first screen 1 was made to be a substantially square shape as shown in FIG. The angle formed by the protrusions and the rotating direction of the rotating body 2 was 45 °. Otherwise, the recycled pulp was produced and evaluated in the same manner as in Example 1.

(Example 5)
In Example 1, regenerated pulp was produced and evaluated in the same manner as in Example 1 except that the number of ridges 12 on the first screen 1 was changed to four at regular intervals in the circumferential direction.

(Example 6)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the flow velocity of the raw material liquid in the passage hole of the first screen was changed to 0.8 m / second.

(Example 7)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the flow velocity of the raw material liquid in the passage hole of the first screen was changed to 2.5 m / second.

(Example 8)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the screen slit width in the B2 step was changed to 0.175 mm.

(Comparative Example 1)
In Example 1, recycled pulp was produced and evaluated in the same manner as Example 1 except that the first screen 1 was not provided with the ridges 12.

(Comparative Example 2)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the passage hole of the first screen 1 was changed from a round hole to a slit having a width of 0.25 mm.

(Comparative Example 3)
In Example 1, the passage hole of the first screen 1 was changed from a round hole to a slit having a width of 0.25 mm, and the projection 12 was not provided on the first screen 1, and the same as in Example 1. Regenerated pulp was manufactured and evaluated.

(Comparative Example 4)
In Example 1, recycled pulp was produced and evaluated in the same manner as in Example 1 except that the screen slit width in the B2 step was changed to 0.30 mm.

The results are shown in Table 1.

From the results shown in Table 1, when Example 1 and Comparative Example 1 are compared, by performing the B1 process using the first screen having ridges, the polyresidue remaining in the regenerated pulp compared to the case without ridges. It was found that the number of strings and adhesives was greatly reduced, and the continuous operation time of the B process was increased.
From the result of Comparative Example 2, even when the first screen is provided with protrusions, if the passage hole is a slit having a width of 0.25 mm, the poly string and the adhesive remaining in the regenerated pulp compared to the case of the round hole It was found that the amount of materials increased and the continuous operation time of the B process was shortened.
When Example 1 was compared with Comparative Example 4, it was found that when the slit width of the slit screen in the B2 step was 0.3 mm, a large amount of fine poly string and adhesive remained in the recycled pulp.

It is a schematic block diagram which shows 1st Embodiment of the screen apparatus concerning this invention. It is a perspective view which shows the example of the 1st screen concerning the apparatus of FIG. It is a top view of the example of the 1st screen concerning the apparatus of FIG. It is a schematic block diagram which shows 2nd Embodiment of the screen apparatus concerning this invention. It is a perspective view which shows the example of the 1st screen concerning the apparatus of FIG. It is a top view of the example of the 1st screen concerning the apparatus of FIG. It is a perspective view which shows the modification of the 1st screen concerning the apparatus of FIG.

Explanation of symbols

1, 50 ... first screen,
2, 60 ... Rotating body,
3, 70 ... housing,
11 ... pass hole,
12, 52, 55 ... ridges.

Claims (6)

A screen device for removing foreign matter in a liquid,
A cylindrical first screen provided with a passage hole having a hole diameter of 1 mm to 4 mm on the peripheral surface, and a rotating body provided coaxially with the first screen inside or outside the first screen. The screen device is characterized in that a convex strip extending at an angle intersecting with the rotation direction of the rotating body is provided on a peripheral surface of the first screen facing the rotating body.   The screen device according to claim 1, wherein the passage hole of the first screen is a round hole.   The screen device according to claim 1 or 2, wherein a minimum value of a clearance between the ridge and the rotating body is 0.1 to 30 mm.   The screen device according to any one of claims 1 to 3, wherein the number of the ridges in the circumferential direction of the first screen is 1 to 6 per circumference. A method for producing recycled pulp through a screening process for removing foreign substances in a raw material liquid in which paper is dispersed in a liquid,
The screening step includes a first step of removing foreign matter using the screen device according to any one of claims 1 to 4,
The manufacturing method of the regenerated pulp characterized by having a 2nd process of removing a foreign material using the 2nd screen which has a slit with a slit width of 0.08 mm-0.25 mm after the said 1st process. The peripheral speed of the rotating body in the first step is 5 m / sec to 25 m / sec, and the flow velocity of the raw material liquid in the passage hole of the first screen is 0.2 m / sec to 3.0 m / sec. A method for producing a regenerated pulp according to claim 5.

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