JPH0533280A - Method for separating undigested substance - Google Patents

Abstract

PURPOSE: To keep a cylindrical screen clean in an apparatus for separating knots by specifying respective directions of feed of fiber suspension and discharge of reject while giving a pressure pulse 2 from inner side of the cylindrical screen rotating. CONSTITUTION: A cylindrical screen 5 is rotated in a direction parallel to the direction of feed of a fiber suspension and reject is discharged from outside in a tangential direction relative to the direction of rotation of the cylindrical screen. A positive and/or negative pressure pulse is given to the cylindrical screen from inner side by a blade 6, or the like.

Description

Detailed Description of the Invention

The present invention relates to a method and apparatus for separating undigested material. The method and apparatus are particularly suitable for separating undigested material from highly concentrated pulp.

Several different undigested matter separators are already known. One device is U.S. Pat. No. 3,947,
No. 314, a cylindrical outer casing and inner casing screen, a rotating screw conveyor inside the casing screen, an inlet adjacent the lower end of the casing screen, and a lower end of the outer casing. It is composed of an accept (raw material pulp from which foreign substances have been removed) outlet adjacent to the section and a reject (waste such as undigested material) outlet adjacent to the upper end of the casing screen. The entire device is preferably slightly tilted with respect to the vertical. The device feeds pulp containing undigested material and other large pieces of wood to the lower end of the casing screen and then lifts it on a screw conveyor. As the screw conveyor lifts the pulp, fine fibers pass through the holes or slots in the porous screen and are discharged through the accept outlet at the lower end of the outer casing. Coarse material, which is not filtered through the holes in the casing screen, is carried to the upper end of the casing screen and dropped from there to a reject chute.

One of the other prior art devices is disclosed in Swedish Patent No. 316363, in which the inside of a cylindrical casing has a slight conical shape and extends downwards. A cylindrical screen is described. Inside the cylindrical screen, a stationary pulsating device is provided to keep the opening of the cylindrical screen open. The pulp is tangentially fed to an annular groove provided at the upper end of the outer casing. In the groove the pulp flows along a horizontal plate arranged on the outer casing, which is spirally oriented on the shaft of the cylindrical screen. There is a hole in the center of the plate described above, through which the pulp falls onto the end cover of the rotating cylindrical screen. The end cover has radial ribs that impart initial rolling motion to the pulp. From this cover, the pulp is centrifugally thrown into a narrow space facing downward between the cylindrical screen and the outer casing. The fine fibers pass through the cylindrical screen to the accept side. The material remaining between the outer casing and the cylindrical screen, namely the reject, is finally discharged into an annular groove at the lower end of the outer casing, from which the reject is discharged towards the tangential outlet.

Third, but US Pat. No. 4,44
The device disclosed in 1,999 comprises a cylindrical outer casing and a rotating cylindrical screen. Inside the cylindrical screen are one or more stationary non-rotating blades. The pulp is fed tangentially between the cylindrical screen and the outer casing, but opposite to the direction of rotation of the cylinder. The accepts are ejected from the inside of the cylinder screen at the ends of the cylinder, and the rejects are tangential, but opposite to the direction of rotation of the cylinder. The device according to the invention comprises a radial arm in which the cylindrical screen consists of an opening which opens towards the inside of the cylinder and a connecting piece which in principle bends in the direction of pulp flow towards the cylinder. And the radial arm and the component generate a pressure pulse on the pulp, leaving the cylindrical screen perforated. The device according to the invention works particularly well in short circulations of a papermaking machine,
It enables the damping of pressure waves that are harmful to the next process.

The latter two devices reach densities in the range of 4 to 6%, and the device of the first example only works at densities up to 1.5 to 2%, all the clogging of the holes of the cylindrical screen. The operation of the device is restricted. However, the aim in the stock process is to steadily move towards higher consistency, since there is always a tendency to prepare pulp in different processes at the same consistency without thickening or diluting. Is preferable. If it is possible to increase the pulp concentration in the process, savings can be obtained from both the equipment and transportation burden,
In addition, energy savings can be obtained.

The present method and apparatus for separating undigested material have evolved from the above-mentioned basis, since they reach a low range of so-called MC concentrations (6-8%), which considerably reduces energy consumption. is there. The rise of the appropriate range of consistency is achieved by correct measurement and placement of the screen profile and optimization of the cylinder rotation speed with respect to the pulp feed rate. In addition to that, US Pat. No. 4,441,9
Compared to the device of No. 99, the energy consumption of the undigested matter separator itself can be reduced. This is mainly due to changing the direction of rotation of the cylindrical screen parallel to the pulp feed direction. Depending on the tests performed,
The energy consumption of the undigested matter separator of the present invention itself is at most 0.
It was determined to be 6 Kwh / mass. Furthermore, changing the direction of rotation also reduces wear on the cylindrical screen.

A further advantage of the device according to the invention is that it is easier to eject rejects compared to the device according to US Pat. No. 4,441,999. In the device according to the invention, the rejects are ejected in the direction of rotation of the cylindrical screen. This pumping effect together with the dilution water supplied to the rejects during the discharge phase makes it much easier to regulate large quantities of rejects.
Thus, even at high densities, the rejection rate can be kept between 2 and 10% by using the screen according to the invention.

The method according to the invention is characterized in that the fiber suspension is guided tangentially in the direction of rotation of the cylindrical screen and the rejects are discharged tangentially in the direction of rotation of the cylindrical screen. Is inside.

In the apparatus according to the present invention, the rotation direction of the cylinder is the same as the pulp supply direction from the inlet connection body, and the discharge direction of the reject from the outlet connection body is the same as the rotation direction of the cylinder. It is characterized in that the outer surface of the cylinder is formed so that ridges are provided between the openings.

[0010]

The method and device according to the invention will be further explained with reference to the accompanying drawings. The undigested matter separator (hereinafter referred to as knotter) in FIGS. 1 and 2 is described as a preferred embodiment of the present invention, and this knotter has an inlet connector 2 for pulp provided therein. It is composed of a cylindrical outer housing 1, an outlet coupling body 3 for accepting, an outlet coupling body 4 for rejecting, a cylindrical screen 5 and one or more fixed non-rotating blades 6. The rotating blade 6 extends inside the cylindrical screen 5 and near the surface of the cylindrical screen 5. The cylindrical screen 5 is mounted by means of a member 12, for example on a shaft 7 functioning by a belt drive (not shown). The space 8 between the cylindrical screen 5 and the outer housing 1 is annular and is sealed at both ends with radial plates 9, 10 projecting from the outer housing 1 towards the shaft. The above-mentioned connecting bodies 2, 4 are mounted tangentially to the outer housing 1 of the annular space 8.

Further, the dilution water supply pipe 11 is attached to the connector 4 of the reject, and if necessary, it is used to reduce the concentration of the reject to facilitate the next screen operation. The blade 6 is mounted on the fixed frame 15 on the arms 13, 14
The fixed frame also forms a column for the shaft 7 via the bearing 16.
Since the blade 6 is in the cylinder 5, the blades arranged near the reject coupling body are ± 10-45 ° except for the reject coupling body. Correspondingly, the inlet connector 2
Other blades are at 10-45 °.
The blades thus described generate appropriate positive and / or negative pressure pulses on the cylinder 5.

In FIGS. 3 and 4, an open screen according to a preferred embodiment is described. The contour plate 20 is composed of openings 21 and lands 22 between the openings 21. The plate 20 is flat on the inner surface 23 that does not include any openings. The outer surface of the plate 20 is a front surface 25 that rises at a predetermined angle from the flat surface 24 of the plate 20, a surface 26 that is substantially parallel to the flat surface 24 of the plate 20, and a flat surface 2 of the plate 20.
4 and a portion 28 of the plane 24 between the openings 21. On the other hand, the plate screen is raised 2
It can be considered that it consists of a plate with 9 and the ridge 29 consists of the above-mentioned parts 25, 26, 27 and the planar part 28 between them, the opening 21 being machined.

As can be seen in FIG. 4, the opening 21 is preferably a hole (or slot), the diameter of which in the present embodiment lies in the range between at least 5 and 15 mm. Further, as can be seen from FIG. 4, the ridge 29 may be slightly inclined from the axial direction of the plate. Inclination angle of ridge, direction of inclination with respect to rotation direction, rotation speed, and ridge portion 25
With the increase of, the knotta pulp circulation rate can be optimized with respect to the separation result. The peripheral speed of the cylinders used in the tests carried out was 4 to 10 m / s, at which time the pulp feed rate was 2 m / s. In this case, the speed difference between the cylinder and the pulp is 2 to 8 m / s. The swash plate 25 of the ridge 29 of the plate screen 20 receives the pulp that enters the cylinder and accelerates it. The direction of the ridge 29 is the cylindrical screen 5
If the upper ridge 29 is tilted rearward, the ridge has the effect of raising the pulp upwards in the cylinder, thereby increasing the circulation time of the pulp in the knotter and producing a more accurate separation. In other words, the reject amount is reduced and the accept amount is increased.

If the ridge is tilted forward, the circulation time will be short and the separation will no longer be accurate. In addition to the factors mentioned above, the height of the cylindrical screen depends on the speed used,
Affects the tilt angle. The method and device according to the invention function as follows. The pulp is tangential to the pressure,
It is supplied to the space between the cylindrical screen and the outer housing of the knotter, the supply then being in the same direction as the rotary movement of the screen. The ridges of the cylindrical screen are subjected to a circumferential force by the feed pulp to increase the operating speed.
This is due to the shape of the ridges and also to the shear forces that open the bonds between the pulp particles or fibers.
The ridge creates a low pressure area at the exit end in front of surface 27,
The low-pressure region attracts loose fibers through the openings 21 with the aid of the pressure difference between the inlet connector 2 and the acceptor connector 3. When the heavier particles carried by the pulp hit the bump, they are thrown towards the surface of the housing 1 and are also subject to centrifugal forces. The lighter particles of pulp then thicken near the cylindrical screen and are separated from the pulp by the method described above. Due to the contour of the surface of the cylinder, a slight fluidization occurs near the cylindrical screen,
Helps separation, while reducing energy consumption during separation,
It also reduces wear on the cylindrical screen. The heavier particles separated on the surface of the outer housing of the knotter circulate along the spiral passage below the surface of the housing and are tangentially ejected from the knotter via the connector 4. If necessary, the discharge is further activated by supplying dilution water from the pipe 11 to the reject.

As already mentioned, the device according to the invention described can reduce the energy consumption by more than 30% with respect to the prior art, while at the same time increasing the pulp concentration to the low range of MC concentration. As a by-product, a reduction in the wear of the cylindrical screen was achieved and a more adjustable device in function and in the end result was also achieved. For example,
By simply changing the rotational speed of the cylinder, the device can be adjusted to accommodate different concentrations and different types of pulp. If this method adds the possibility of creating a cylindrical screen with ridges with varying tilt angles and resizable openings, the ultimate optimized knotter can be discussed.

The apparatus described above represents one embodiment of the apparatus according to the invention, and there are many apparatus and methods according to the invention which are practically different from the embodiments, and which are attached. This is the same as the invention described in the claims. In some cases it is also possible to utilize the tilt angle of one or more ridges and the pulp suspension velocity and the cylinder velocity may differ from the examples given above. The speed difference specified in 2 is 2
~ 8 m / s.

[Brief description of drawings]

1 is a partial cross-sectional side view of a device according to the present invention.

2 is a partial cross-sectional top view of the device of FIG.

FIG. 3 is a cross-sectional side view with a straightened screen profile of the preferred embodiment.

4 is a schematic view of the screen of FIG.

[Explanation of symbols]

1 Outer housing 5 Cylindrical screen 6 Fixed non-rotating blade 29 Uplift

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[Procedure amendment]

[Submission date] August 27, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

If the ridge is tilted forward, the circulation time will be short and the separation will no longer be accurate. In addition to the factors mentioned above, the height of the cylindrical screen depends on the speed used,
Affects the tilt angle. The method and device according to the invention function as follows. The pulp is tangential to the pressure,
It is supplied to the space between the cylindrical screen and the outer housing of the knotter, the supply then being in the same direction as the rotary movement of the screen. The ridges of the cylindrical screen are subjected to a circumferential force by the feed pulp to increase the operating speed.
This is due to the shape of the ridges and also to the shear forces that open the bonds between the pulp particles or fibers.
The ridge creates a low pressure area at the exit end in front of surface 27,
The low-pressure region attracts loose fibers through the openings 21 with the aid of the pressure difference between the inlet connector 2 and the acceptor connector 3. When the heavier particles carried by the pulp hit the bump, they are thrown towards the surface of the housing 1 and are also subject to centrifugal forces. The lighter particles of pulp then thicken near the cylindrical screen and are separated from the pulp by the method described above. Due to the contour of the surface of the cylinder, a slight fluidization occurs near the cylindrical screen,
Helps separation, while reducing energy consumption during separation,
It also reduces wear on the cylindrical screen. The heavier particles separated on the surface of the outer housing of the knotter circulate along the spiral passage below the surface of the housing and are tangentially ejected from the knotter via the connector 4. If necessary, the discharge is further activated by supplying dilution water from the pipe 11 to the reject. Furthermore, since the pulp is supplied in the rotating direction of the cylindrical screen, the speed difference between the pulp and the cylindrical screen is reduced, facilitating passage of fibers and particles through the openings of the cylindrical screen, and effective separation is achieved. To be done.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location // B03B 5/00 Z 8925-4D (72) Inventor Hannu Lonecornhayu Finland Country. SF-48700 Kimin Lina, Remin Kaisenkatsu 20

Claims (2)

[Claims] 1. A rotating cylindrical screen directs the fiber suspension to be conditioned on the outer surface of the cylindrical screen to separate undigested and other solids from the fiber suspension. From the outside and rejects from the outside, in which the fiber suspension is fed tangentially to the direction of rotation of the cylindrical screen, the reject being directed to the direction of rotation of the cylindrical screen. Method for separating undigested material, characterized in that it is tangentially discharged and the rotating cylindrical screen is kept clean by receiving positive and / or negative pressure pulses from the inside. 2. The method according to claim 1, wherein discharge of the reject is facilitated by spraying water on the reject discharge duct, and the concentration of the reject is simultaneously diluted by the water.