JPS647808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for treating flowing suspensions, and in particular to an apparatus for continuously withdrawing liquid from flowing suspensions. , consisting of any solid material suspended in a liquid, especially fiber-containing cellulose suspended in water or other suitable liquid for the treatment of the material.

The invention particularly provides for concentrating suspensions.
Relating to a device for continuously and evenly withdrawing a liquid, or by replacing the liquid of a suspension with it by simultaneous addition of a replacement liquid to achieve a more or less exchange of the suspension. Relating to a device for

The most significant problem with the withdrawal of liquid, particularly from fiber suspensions, is that the screen bodies have a tendency to become clogged, thus reducing the withdrawal capacity and eventually stopping the operation altogether. Therefore, cleaning of many through holes in some types of screen bodies is necessary. This problem is covered by the Swedish patent no.
7504309-1 and corresponding U.S. patent no.
4041560, according to which a movable screen body is supported on a central stationary support and the suspension is passed through a number of through holes in the screen body. A backflow of liquid to the screen body is obtained by a periodic reduction of the volume inside the screen body due to the movement of the screen body.

The main object of this invention is the evenly distributed and effective backflow of liquid for the cleaning of the many through holes of the screen body and the improvement of the movement of the suspension past the many through holes of the screen body. It consists in improving the design of already known devices in order to achieve this.

Another object of the invention is that it is not only suitable for the withdrawal of liquids and thereby the concentration of suspensions;
The object is to obtain a device which is also well suited for liquid exchange treatment of suspensions with one or several different liquids.

A third object of the present invention is to provide an apparatus that can perform a multi-stage exchange process in which the liquid extracted from each stage is collected individually using simple means.

The invention will now be described in detail with reference to FIGS. 1-8.

In FIG. 1, reference numeral 1 designates a primarily cylindrical shell or housing, which is fitted with sealing lids 301 and 302 at each end. Housing 1
has at one end an inlet 20 for the suspension to be treated;
and has a suspension outlet 311 at the other end. Inside the housing 1, a screen body 304 with a sieving surface with many through holes is arranged concentrically, which has a screen body cavity 330 inside. The screen body 304 contracts conically in the direction of the flow of the suspension. This screen body 304 is
At its upper end it is supported via a circular sealing member 306 by a concentric support 305 with a support cavity 331 inside and has a closure lid 307 at its other end. The support body 305 is a sealing lid 30
1 and the inside of the support 305 communicates with a liquid outlet 308 . The interior of the screen body 304 is partially filled with a baffle plate constituting a baffle body 309, which is conically shaped or preferably parabolically shaped as shown. This baffle 309 is connected with its narrow end 310 closest to the suspension inlet 20 and with its thick end to the closure lid 307 near the suspension outlet 311 or Form. The baffle body 309 has a thin end portion 310
and is connected to a shaft 312, which can be moved by a drive device 314 while penetrating the sealing lid 301 via a sealing member 313. This drive device 314 can be constituted by a hydraulic or pneumatic cylinder and moves the baffle body 309 and the screen body 304 forward and backward, viewed in the main direction of movement of the suspension. The screen body 304 is porous with suitable through holes throughout most of its length. The baffle 309 extends at least over the porous portion of the screen body. In some uses,
The screen body 304 may consist of a coarse, porous skirt coated against the suspension with a woven fabric of steel, nylon, or other suitable material.

In the direction of flow of the suspension, i.e. the suspension inlet 20
Housing 1, looking towards exit 311 from
At the head end, inside the suspension outlet 311 , a scraper device 315 is arranged concentrically with respect to the housing 1 . This scraper device 31
5 rotates in the suspension by means of a drive 316 and a shaft 317 passing through a sealing member 318 to direct this suspension towards its outlet 311.

The same reference numerals as in FIG. 1 are used in FIG. 2, but this FIG. 2 differs from FIG. 1 in that there are two drive devices 314 instead of one drive device 314. Each of these drives 314 has its own sealing member 313 and a shaft 312 passing through the housing 1, with both shafts 31
2 is attached to the screen body 304. The suspension inlet 20 is located at the rising portion 319 of the housing.
will be placed in A shaft 320 is arranged in the center of the rising portion 319, and this shaft 320 is connected to the sealing member 3.
21 and can be rotated by a drive device 322. This shaft 320 mounts a scraper device 323 inside the housing 1 . By means of this scraper device 323 the suspension is distributed around this scraper device 323 . This scraper device 323 may be of the same type as the scraper device 315 of FIG. 1 near the suspension outlet 311.

FIG. 3 shows a modification of the upper part of the device of FIG. 1 with the same reference numerals. The baffle body 309 shown in FIG. 3 is modified so that it opens at a rear portion 324. The baffle 309 is attached to the shaft 312 in this rear portion 324 by ribs 325 . Because the baffle 309 is open, it is filled with liquid, so rather than being considered a baffle, the baffle 309 can be considered a liquid distribution baffle that narrows toward the rear. Back and forth movement of the screen body 304 and the obstruction body 3 caused by this
09 moves back and forth, the liquid contained inside the baffle body 309 also moves. The total mass that is accelerated and moved together with the screen body is therefore large. However, on the other hand, the design of the baffle 309 is simplified to a certain extent, especially if the treatment of high-pressure suspensions is a problem.

Any device of the design described above can be equipped with a device for adding liquid. In FIG. 1, inlets 326 and 327 in housing 1 are
Indicates the point of addition of a liquid, which can consist of a chemical treatment liquid or water. The liquid flows through baffles 328 and 3
29, the baffle plate 32 is distributed inside the housing around the inside circumference of the housing.
At the lower edge of 8,329 it drains into suspension. Although only two inlets 326 and 327 are shown in the figure, the number of addition inlets can, of course, be
It can be varied as required and depending on the length of the screen body 304. The added liquid is, for example, a chemical treatment liquid, which is distributed in suspension along the inner wall surface of the housing 1 and continuously drawn out through a number of through holes in the screen body. Replaces the liquid present in the suspension. The distance between addition inlets 326 and 327 is such that when the suspension reaches inlet 327, the liquid added at inlet 326 replaces the original liquid in the suspension. Can be adjusted. The liquid added at inlet 327 can then replace the liquid added at first addition inlet 216 before the suspension leaves the device through outlet 311.
Same below.

In FIG. 4, reference numeral 1 designates a substantially cylindrical shell or housing, which is open at its lower end 2 and is fitted with a flange 3 for connection to a conduit or another device. A flange 4 is provided at the top end of the housing, and this flange 4 has a
The sealing lid 5 is tightened. The housing 1 has a cylindrical support 6 therein.
along the screen body 3 formed as a cone
0 can be moved up and down by means of a cylindrical sliding seal 8.

The top part of the screen body 30 has a cylindrical part, to which the sliding seal 8 is fixed.
The support 6 with the support cavity 16 is also cylindrical, but transitions downward into a conically shaped baffle 31 . This baffle body 31 has approximately the same conicity as the screen body 30. At the bottom end of the baffle body 31,
terminating in a sealing member 32, which is connected to the shaft 1
Penetrate so that 0 can move up and down. The conical baffle 31 forms a baffle cavity 33 which, at the top, connects to the support cavity 16.
This support cavity 16 in turn communicates with a liquid outlet 17 . A row of apertures 34 is disposed approximately at the top end, that is, approximately the rear end, of the baffle body 31;
Communication between the screen body cavity 35, the baffle body cavity 33 and the support body cavity 16 is thus achieved.

The vertical movement of the screen body 30 is carried out by a drive device 9, which is connected to the lower part of the screen body 30 by a shaft 10.
The shaft 10 passes through the closure lid 5 at the closure member 11 . The housing 1 further includes an inlet 20 for the suspension to be treated and an inlet 21, 2 for the treatment liquid.
It has 2,23. The processing liquid is applied to the baffle plates 24 and 25.
and 26 in suspension along the walls of the housing 1.

The apparatus illustrated in FIG. 5 is principally similar to the apparatus of FIG. 4, but differs from the apparatus of FIG. 4 in certain respects, as discussed below. housing 40
has rounded end walls at the top and bottom and is provided with an inlet 20 and an outlet 41 for the suspension. Instead of having only one drive 9 as described above,
The device comprises two such drives 9, each drive 9 having a shaft 10 passing through the top wall of the housing 40 by means of a sealing member 11. In the center of the device,
A drive device 42 for rotating a shaft 43 is arranged, which shaft 43 passes through the end wall of the housing at a sealing member 44 and a scraper device 45
Attach it to the bottom end. This scraper device 45 is
This serves to distribute the suspension entering the space around the screen body 46 through the inlet 20. The screen body 46 is supported at its top end on the support 6 by means of a sliding seal 8, as described above. The screen body 46 tapers downward into a conical shape to a cylindrical lower portion 47.
7 has an internal sliding sealing member 48 movable along the cylindrical lower part 49 of the baffle 50.
The baffle body 50 has the same conicity as the screen body 46 along the corresponding length of the screen body 46 . The cylindrical lower part 49 of the baffle 50 ends in a closure lid 51 .

The conical baffle 50 is connected at its top end to the cylindrical support 6 in a similar manner as in FIG. In this case, the support 6 comprises a top lid 52 to which a liquid outlet 53 is connected. Furthermore, the support body 6 is fixed to the housing 40 by ribs 54. The ribs 54 may consist of plates that extend radially outward and are distributed around the circumference of the top lid 52 in order to provide as little resistance to the movement of the suspension as possible, as will be explained below. , it can also consist of a hollow element for conducting away the liquid. The screen body cavity is indicated by the reference numeral 55, and this screen body cavity 55
communicates with the baffle cavity 33 and the support cavity 16 by an aperture 34, which in turn communicates with the outlet 53. A scraper device 56 is arranged near the suspension outlet 41, which scraper device 56 has a shaft 57 and a drive device 5.
8 to ensure uniform delivery of the treated suspension through the outlet 41. The shaft 57 passes through the sealing member 59 in a sealed manner.

Approximately halfway down the conical baffle 50 there is a partition wall 60 and a small aperture 61 shown in dotted lines. With such a partition wall 60,
The baffle cavity 33 can be divided into two chambers, so that the liquid discharged into the screen body cavity 55 through the many through holes of the screen body 46 can be separated into an upper half and a lower half, respectively. In this way, liquid passing through the top aperture 34 is led out through the outlet 53, and liquid passing through the lower aperture 61 is directed from the chamber below the partition wall 60 into the baffle cavity. A conduit (not shown) passing through the upper part and the support cavity 16 allows access into and exit from the hollow rib 54 . This hollow rib 5
4 can be connected to a special outlet. In such a case with the partition wall 60, the liquid from the upper inlet 21 (which may itself be a chemical treatment liquid, for example a chemical treatment liquid for bleaching suspensions) is
The liquid from the lower inlet 22 (which may be another process liquid) can replace the liquid of the suspension above the partition wall 60 and the liquid from the suspension below the partition wall 60. Can be replaced.
For example, if washing the suspension is a problem, the liquid extracted from below the partition wall 60 may be removed from the inlet 2.
1 and discharge the liquid to the outside of the device from above the partition wall 60 through the outlet 53, thereby performing cleaning by flowing the liquid in the opposite direction to the flow direction of the suspension. is extremely easy to accomplish. In a similar manner, the baffle cavity 33
can be divided into more stages than the two stages described above by a number of partition walls 60. For example, the obstruction cavity 33
can be divided into four chambers by three partition walls 60. Below each partition wall 60 is provided a row of apertures, such as apertures 61, and conduits rising through the upper cavity, these conduits being connected to the respective ribs 54. Reach another exit. Furthermore, two additional inlets similar to inlets 21, 22 should be added, so that four inlets can be used for liquid exchange. In order to carry out the counterflow principle in which the liquid flows in the direction opposite to the flow direction of the suspension, the liquid from the lowest chamber can be directed to the third inlet counted from the top for liquid exchange. The liquid from the second chamber from the bottom can be directed to the inlet 22, the liquid from the second chamber from the top can be directed to the inlet 21, and the liquid in the uppermost chamber can be It can be discharged through outlet 53. For example, if washing is a problem, fresh water can be added to the suspension through the bottom inlet.

In FIG. 5, the screen body 46 is supported by the central support 6. In FIG. As another design,
The screen body is mounted in a conical housing 40 with short cylindrical support surfaces of different diameters at the top and bottom.
It is also conceivable to support it by The device can thus be arranged such that the suspension flows through the screen body and the liquid is drawn off radially outward rather than inward. The housing is
It has approximately the same degree of conicity as the screen body, and serves as a conical obstruction behind the plate-shaped screen body.
If desired, the displacement liquid can be added to the center of the device by means of a suitable nozzle arrangement, so that this liquid spreads in all directions towards the surrounding screen body.

FIG. 6 shows a rectangular container or housing 100 viewed from above. This housing 100 has three equal supports 101 each having a screen body 104. The housing 100 further includes three outlets 107, one for each support 101, for the liquid to be drawn off.
has. The housing 100 further includes four inlets 110 for displacement liquid, and three drives 1, one for each screen body 104.
It has 14.

FIG. 7 shows the part behind the line AA in FIG. 6, and it can be seen from this FIG. 7 how the movable parts and the stationary parts are arranged. In FIG. 7, the symbols corresponding to those in FIG. 6 are used. Since all screen bodies 104 are equivalent to each other, only the left screen body will be described. Screen body 104 can be moved up and down along support 101 by means of sealing members 117 and 118. The support 101 has a support cavity 16
has. The lower part of the support 101 is configured as a baffle 128, as in FIG. It has a surface. In the figure, the suspension moves from top to bottom. In the illustrated design, drive unit 114
The shaft 10 is fixed to the screen body 104 by a rib 126. The rib 126 is the baffle body 12
8 and extends from the shaft 10 to the screen body 104. Obstruction body 12
8 has a baffle cavity 33, as described above with respect to FIG. 4, and has the same angle as the wedge-shaped, porous lower portion of the screen body 104. The apertures 127 are made large enough to simultaneously serve as through-holes for the liquid to be withdrawn, so that the liquid can flow into the baffle cavity 33 and the support cavity 16 and further into the housing 100. can flow to the outer edge of and outlet 107. If it is desired not only to concentrate the suspension, but also to exchange the liquid, the exchange liquid can in principle be added at the wall of the housing by means of tubes 131 and 132, as shown. , and can be added into the space between the screen bodies 104 by means of corresponding pipes. The paired tubes used to fill the space between the screen body 104 are connected to vertical plates 135 and 136.
are interconnected by. These plates act as dividing plates and thus pass through the inlet 110 to the tube 131,
The liquid added through the tube corresponding to 132 is
On both sides of the dividing plates 135 and 136, the tubes are equally divided into right and left screen bodies 104 by a number of apertures provided in these tubes.
In the figure, arranged in the flow direction of the suspension,
Although only two sets of tubes 131 and corresponding tubes and tubes 132 and corresponding tubes are shown, the same or several different displacement liquids can be supplied to the suspension if desired. for,
Many sets can be placed one after the other. It may also be noted that although the displacement liquid supply devices are illustrated as tubes extending laterally into the suspension, these tubes should in principle be designed to provide as little resistance to the flow of the suspension as possible. , should be arranged so as to minimize sticking of particles of the suspension as much as possible. This also holds true in principle for other types of feeding devices, such as those designated by 328 and 329 in FIGS. 1 and 3.

FIG. 8 shows a circular container or housing 2.
00, the housing 200 has an inlet 201 and an outlet 202 for the suspension liquid, an outlet 203 for the liquid to be withdrawn and an inlet 204 and 205 for the replacement liquid. This device can be comparable to the device of FIG.
and drive devices 208 and 209 for rotationally moving the distribution scraper devices 210 and 211 located at the outlet 202, respectively. In this case, the screen body 215 is formed as a double-walled annular body with a cross-section approximately as shown and described in FIG. Cylindrical support 21
6 and a conical baffle 217 are also annular and extend inside the screen body 215, and these supports 216 and baffles 217 form a variable screen body cavity 2 inside the screen body 215.
14 is formed. If desired, displacement liquid can be added through inlets 204 and 205;
Liquid from these inlets 204, 205 is distributed into the suspension by baffles 218 and 219. These baffles 218, 219 distribute the liquid in the suspension flowing along the circumference of the housing, but for the suspension flowing in the central space 220, the liquid is centrally It is distributed as follows. This device 221 consists of a rotating part having a hollow shaft and configured to introduce liquid through an inlet 222, which rotating part is driven by the drive device 209 for the lower scraper device 211. . The liquid flows upwardly in the hollow shaft and is distributed outwardly from the aperture 223 towards the inner cavity of the cap 224 and finally at the lower edge 225 of the baffle constituted by the cap 224. flows outward. In this way, the displacement liquid can be distributed into a peripheral suspension stream and a central suspension stream. Although only one screen body 215 is shown in FIG.
If large installations are a problem, several screen bodies of different diameters can be distributed over the cross section of the housing. In order to obtain the best possible conditions for replacement, in the distribution of screen bodies the distance between the device for liquid supply and the nearest screen body should be approximately 0.1 to 0.5 meters. Approximately similar conditions hold regarding the thickness of the suspension layer in the case where no liquid is added and only concentration is a concern.

The device as described above works as follows.
As can be seen from the above and detailed description of the respective drawings, all device designs provide suction and It is based on the main principle that pressure is generated respectively. As the volume of the screen body cavity increases, a low pressure is created in the screen body cavity, whereby liquid is sucked out of the suspension through the many through holes of the screen body. A portion of this liquid is led out of the screen body cavity through the support cavity and discharged through a suitable outlet.

During the return movement of the conical screen body against the suspension, which should be faster than the forward movement, the volume of the screen body cavity is reduced so that part of the liquid in the screen body cavity is , through the through-holes of the screen body, and are pushed out to the outside of the screen body to form a liquid layer between the screen body and the suspension. This liquid layer reduces the friction between the screen body and the suspension, so that the flow of the suspension is
Continue unhindered by the return movement of the screen body.

When the screen body moves cocurrently with the flow of the suspension, the friction between the suspension and the screen body is extremely high due to the pressure of the pulp in the suspension against the screen body. On the other hand, due to the fact that the displacement liquid creates a liquid layer, the friction between the suspension and the housing becomes very small. Thereby, the suspension is distributed evenly across the entire cross section without significantly changing the relative positions of the suspended particles. An even feeding of the suspension in the direction of movement is further facilitated by the fact that the space between the housing and the screen body increases in the direction of movement of the suspension. These considerations will help you obtain the best possible replacement conditions.

In particular, devices of circular design are suitable for processing suspensions at some pressure above atmospheric pressure, in which case a suitable pressure drop across the suspension and the through holes of the screen body is obtained. As such, it is particularly important to control the flow of liquid by a suitable adjustable control device associated with the liquid outlet. Furthermore, the pressure conditions can be adjusted by adjusting the number and dimensions of the apertures (34 in FIGS. 4 and 5 and 127 in FIG. 7) in the baffle body to suit the dewatering capacity. , controlled. The pressure drop should not be too large, since if the pressure drop is too large, the suspended particles will quickly clog the through holes of the screen body. The volume of the screen body cavity decreases when the screen body moves counter to the flow direction of the suspension, regardless of the pressure at which the device is applied. The pressure inside increases. This pressure increase forces the liquid back through the through holes in the screen body, whereby particles that were possibly stuck in the through holes in the screen body are loosened and at the same time pass through the through holes in the screen body. The continuous movement of the suspension is improved. Liquid withdrawal is accomplished in a hydraulically filled system. Movement of the screen body therefore moves liquid from the suspension through the screen body cavity, baffle cavity, support cavity and out of the device. Outflow from the device is continuous. However, a small portion of the separated liquid will intermittently flow back through the through holes in the screen body. If the liquid outlet from the device is closed, the liquid will only flow through the through holes in the screen body and back again. If the exit is open,
Continuous withdrawal of liquid from the device takes place.

With already known device designs, problems arise, as has been demonstrated, in obtaining an evenly distributed backflow of liquid in the length of the device and thus cleaning of the through holes. As shown, upon movement and acceleration of the screen body opposite to the main direction of movement of the suspension, liquid tends to collect in the rear part of the screen body, thereby causing The through holes of the screen body are cleaned larger than the through holes of the screen body in the front part. This problem can be solved by making the screen body conical and installing a conical baffle behind the screen body. Figure 1,
In the designs shown in FIGS. 2 and 3, a conical or parabolic baffle with a conicity opposite to that of the screen body is provided, and the baffle is moved together with the screen body. Then the problem is solved. In all the remaining designs according to FIGS. 4 to 8, the problem is solved by providing a stationary baffle with substantially the same conicity as the screen body.

As the suspension moves through the device, the conical shape of the screen body ensures that it obtains a cross section that constantly increases with the movement; this arrangement, of course, Helps facilitate movement through the device. When the screen body moves in the direction of the flow of the suspension, the conical screen body pushes the suspension in the direction of movement. The range of motion of the screen body is often between 0 and 100 cm. When the screen body then moves relatively quickly back to its starting position, a cone-shaped liquid-filled cavity remains behind the screen body, assuming the suspension is considered a solid substance. In other words, this means that
When the screen body moves rapidly back, it means that in a certain cross-section the suspension suddenly acquires a large through-flow cross-section, which reduces the possibility of a forward movement of the suspension. Improved. However, the device is designed in such a way that during a rapid return movement of the screen body, a reduction in the volume of the screen body cavity occurs at the same time. Therefore, high pressure is applied to the liquid-filled cavity of the screen body. This high pressure forces the liquid to flow out through the holes in the screen body, and this flowing liquid causes
Effective cleaning of possible fibers and other particles is achieved through the holes in the screen body. This return flow of liquid furthermore causes the screen body, on the suspension side, to leave behind a cavity as described above during a rapid return movement, which cavity is then absorbed by the liquid coming from the screen body cavity. This is achieved even more effectively by the fact that it is fulfilled. clearly,
Due to the conical shape of the screen body, the cleaning of the through holes of the screen body by the liquid coming from the inside can be effectively achieved, and at the same time the movement of the suspension passing outside the screen body can be partially prevented. will be improved.

The above description of operation essentially refers to the device according to FIGS. 1 to 3, i.e. using a conical baffle with a conicity "parallel" to the conicity of the screen body. Relates to devices that do not have one inside. However, in the devices according to FIGS. 4 to 8, inside the screen body,
Such obstacles exist. For example, in Figure 4,
The screen body 30 is illustrated as being in its lower position, so that the inner baffle body 31 has a maximum distance relative to the screen body. The space between the surface of the screen body and the baffle body is filled with liquid during operation, and this liquid moves to a certain location because its permissible volume is reduced during the upward movement of the screen body. Must. A portion of the liquid will thus migrate through the apertures 34 in the support, the number and dimensions of which are selected to provide resistance to flow through, so that during the upward movement of the screen body, the liquid The other part is the screen body 30
is pushed out through the through hole. Since the baffle body 31 and the screen body 30 have approximately the same degree of conicity according to the "cone-to-cone" principle, in practical terms, the screen body has a porous surface that is similar to the baffle body 3.
It can move upward until it touches 1.
Since the planes of the screen body approach the baffle body in a parallel manner, an even reduction in the volume along the length of the device is obtained, so that the liquid forced into the screen body cavity flows through the through holes of the screen body. towards and then pushed through. According to this method, even cleaning by backflow in the through holes of the screen body can be achieved over the entire length. The liquid that has passed through the apertures 34 in the support then leaves the device through the outlet 17.

Since liquid withdrawal from the suspension flowing through the device is first achieved in the rear part of the screen body, the apertures 34 and 127 in the baffle body
It should be placed in the rear part of the baffle as shown. If it is a question of using the device for example for backwashing, the liquid drawn off in front of the screen body will be cleaner than the first liquid mentioned above and will therefore It is desirable to obtain a flow of liquid moving backwards, so that first of all the dirtiest liquid is removed through the apertures 34 and 127. According to this method, the suspension after treatment will contain the cleanest replacement liquid to the greatest extent possible. If desired, the above-mentioned flow of liquid moving backwards can be further facilitated by making the cone or wedge angle of the baffle body somewhat smaller than that of the screen body; , the free space between the baffle body and the screen body increases in the backward direction.

As mentioned above, the pressure of the suspension should be balanced by a suitable control device with the counterpressure at the outlet of the liquid, so that dewatering can be suppressed and the pressure inside the device The pressure drop will not become too large. If the withdrawn liquid is to be replaced by another suspension liquid, this is added through inlets such as 21, 22 and 23 in FIG. If three different liquids are used in the exchange process, the original liquid of the suspension is replaced by the liquid from inlet 21, and then the liquid from inlet 21 is replaced by the liquid from inlet 22. , and finally the liquid added through inlet 22 is replaced by the liquid added through inlet 23, which, after flowing through the device, becomes the final liquid of the suspension.

The description of the operation with respect to the device according to FIG. 4 is similar to that of FIGS.
This also applies validly to the device according to FIGS. The device according to FIGS. 6 and 7 does not have a circular screen body, but instead has an elongated, straight screen body, but has the same cross section as the device of FIG. 4, so that FIG. The device differs only in its external shape. The cleaning action and uniformity due to backflow is the same. From a manufacturing point of view, straight screen bodies are easier to make, but of course there are practical constraints when the equipment is intended to operate at pressures above atmospheric pressure.
Circular devices are easier to make and are therefore preferred.

The device according to FIG. 8 also acts in the same way as the device according to FIG. has an annular screen body with narrowing surfaces on both sides, and corresponding annular baffles and supports.

Even the device according to FIG. 5 works according to the same principles as described above for the device according to FIG.
The main difference is that the screen body additionally comprises a lower sealing member 48. The design of FIG. 5 results in a reduction and an increase, respectively, of the screen body cavity upon movement of the screen body as a result of the difference existing between the cross-sections of the upper support and the lower support. This is different from the above-mentioned design.
This can be easily understood by imagining a case where both sealing members have the same cross section; in this case, the volume of the screen body cavity between the screen body and the baffle body remains constant. and no effective backflow of liquid through the screen holes occurs. On the other hand, FIGS. 1 to 4 and 6
In the above-described design according to FIGS. can be considered to be caused by a piston having a surface of the same size as the upper sliding seal.

The device according to FIG. 5 with two sliding seals 8 and 28 can therefore be made in principle of any size, since the desired backflow effect can be balanced with the difference in the cross-sectional area of the two sliding seals. be able to. Another essential advantage of the design according to FIG. Neglecting the top part and the possible short cylindrical bottom part, this means that the entire conical part can be provided with many through-holes of the screen body. The screen body is therefore relatively lightweight and the forces required to drive and accelerate the screen body are as small as possible.

A further advantage of the design according to FIG. 5 is that if the sliding sealing members 8 and 48 are made to have a diameter as small as possible relative to the diameter of the inner support, the movement of the screen body will reduce the suspension. The reason is that there is very little turbulence inside.

For all designs, the numerous through holes in the screen body extend, in practical terms, over the entire conical section and are spaced at suitable distances from each other to obtain the desired total aperture area depending on the field of application. It can consist of arranged, round apertures. For certain applications,
It is also suitable to use fabrics of steel, nylon or other materials as the surface of the moving screen body. The woven fabric can be supported by a coarsely porous skirt.

Regarding the back and forth movement of the screen body, when many screen bodies are used, it is also possible to give them movement patterns that are not synchronized. For example, it is also possible to arrange several screen bodies of the type according to FIG. 4, distributed over the cross-section of the housing, each of which can be moved independently of the others.

The results obtained during experiments using the apparatus according to the present invention are described below.

Example: Effective screen area is ^6m2 , diameter is approximately 700mm,
Attempts were made to clean sulfuric acid pulp taken directly from the steamer outlet with a device having a screen body with a pore length of approximately 2.750 mm.

Inlet and outlet pressure, approximately 5 atmospheres.

Inlet and outlet pulp concentration, approximately 9.5%.

Pulp temperature at inlet, 60-70℃.

Cleaning water temperature, 50-60℃.

Cone angle, 2°.

Pulp layer thickness, approximately 140mm.

Compared to known devices, a sieving capacity many times higher was obtained, with cleaning results comparable to other devices, while maintaining extremely safe operation.

In the above description it was pointed out that it is important that the screen body and the baffle body are made conical or wedge-shaped. It is to be understood in this context that a cone-shaped or wedge-shaped section can conceivably be made more or less step-shaped, so that, for example, a cone-shaped section can be made up of a number of backbones of progressively smaller diameter. It can consist of a low cylinder. The cylinders are fixed together and provided with holes in the screen body in a practical manner.
The cylinder can also be arranged such that the through hole in the screen body is formed at the seam between the large cylinder and the small cylinder, in which case the through hole in the screen body is formed in the step part of the cylindrical shape. , located in the "shadow" of the movement of the suspension.

In all illustrative figures, the apparatus is illustrated as having a vertical centerline and the suspension flowing downwards, although reverse, horizontal or oblique flow directions are also possible. However, the illustrated downward flow is desirable. Firstly, vertical flow provides the best conditions for uniform suspension flow in all parts of the practical cross section. Secondly, the screen body performs an actual movement that can be explained as follows. That is, when the screen body slowly moves downward at approximately the speed of the suspension, both the frictional force due to contact with the suspension and the weight of the moving part act in the direction of gravity, The required forces and power are therefore extremely small. During the opposite upward movement, a relatively large force is required to initiate the movement, but after a short distance the backflow through the through holes in the screen body overcomes the friction between the screen body and the suspension. Therefore, moving parts can move easily. And it has been found during trials that gravity can be advantageously used to bring the moving part to a stop, in order to obtain a smooth deceleration and stop without any significant shock.

The device according to the invention can be used in many industrial fields. For example, this device can be used in the pulp industry for the recovery of fibers from liquids, for the concentration of receivers in filtration units and hydrocyclones, for the concentration of suspensions upstream of other processing units, e.g. As a concentration control device, it can be used to replace liquid-containing particles with dissolved or bubbly reaction products by means of a replacement liquid added at the same time as the liquid is withdrawn. Several devices can be combined in series or in parallel as required to obtain the desired high capacity.

The invention is not limited to the preferred embodiments described above, but may vary within the scope of the invention as defined in the claims.

[Brief explanation of the drawing]

Figure 1 shows that the backflow for cleaning the many through holes in the screen body is
1 and corresponding U.S. Pat. No. 4,041,560, and also incorporating features of the present invention, is a longitudinal sectional view of a device for withdrawing liquid; . FIG. 2 shows a diagram in principle of a large device with two drives. Figure 3 is similar to Figures 1 and 2.
FIG. 6 shows a device with an open internal baffle as opposed to the closed baffle of the figure; FIG. 4 is a longitudinal sectional view of a device comprising a screen body with substantially equal conicity and a baffle inside the screen body.
FIG. 5 shows a screen with a sleeve-shaped screen body.
1 is a longitudinal section of the device for large capacity; FIG. FIG. 6 is a top view of a rectangular container containing several straight arrays of screen bodies.
FIG. 7 is a perspective view of a portion rearward from line AA in FIG. 6. FIG. 8 is a partially removed view showing a round housing having an annular conical screen body and an annular conical baffle body. In the drawings, 1, 40, 100 and 200
is the housing, 20 and 201 are suspension inlets, 2, 41, 202 and 301 are suspension outlets, 21, 22, 23, 131, 132, 20
4,205,222,326 and 327 are inlets for exchange liquid, 7,30,46,10
4, 215 and 304 are screen bodies, 10 and 312 are shafts, 35, 55, 214 and 30
3 is a cavity, 17, 53, 107, 203 and 3
08 is an outlet for the extracted liquid, 31,5
0, 128, 217 and 309 indicate baffles.

Claims (1)

Claims: 1. A housing 1, 40, 100, 200 through which the suspension flows in the axial direction, the housing having an inlet 20, 201 and an outlet 31 for the suspension.
1, 2, 41, 202, at least one screen body 304, 30, 46, 104, 215 having a sieving surface for the suspension is disposed in the housing, and the screen body supported by a support, moved back and forth in the direction of flow of the suspension by shafts 312, 10, and provided with an internal cavity 33;
0,35,55,214, and the internal cavity is
Outlet 308, 17, 5 for the withdrawn liquid
3,107,203, and the volume of the cavity is
In a device for continuous withdrawal of liquid from a flowing suspension, which can be varied by the movement of a screen body, the screen body reduces in a conical or wedge-like manner in the main flow direction of the suspension, Inside, baffle plates 309, 31, 5 are placed along the sieving surface.
0,128,217 is arranged. 2 Simultaneously with the withdrawal of liquid, the addition of replacement liquid takes place, and the housing
31,132,204,205,222. 3 The baffle plate 309 is formed as a paraboloid of revolution constituting a baffle with an internal cavity, and the thickest part of the baffle is fixed at the head end 307 of the screen body when viewed in the flow direction of the suspension. An apparatus according to claim 1 or 2, which comprises: 4. The device according to claim 3, wherein the internal cavity of the baffle is closed so as not to communicate with the surrounding liquid. 5. The device according to claim 3, wherein the internal cavity of the baffle has an aperture 324 in its rear part for communication with the surrounding liquid. 6. The device according to claim 1 or 2, wherein the baffle plate 31, 50, 128, 217 is reduced in a conical or wedge shape in the same direction as the screen body and is fixed relative to the housing. . 7. The device according to claim 6, wherein the baffle plate has substantially the same or slightly smaller cone angle or wedge angle than the screen body. 8. The device according to claim 6, wherein the baffle plate forms a baffle having an internal cavity 33 with apertures 34, 61, 127 for communication with the surrounding liquid. 9. Device according to claim 8, in which the apertures 34, 127 are arranged at the rear end of the baffle. 10 The housing 100 has a rectangular cross section, in which at least one straight screen body 104 extending perpendicularly to the flow direction of the suspension is disposed, each screen body having a corresponding 9. The device according to claim 8, having an internal baffle 128. 11 the housing 200 has a circular cross section;
9. The device according to claim 8, wherein at least one concentric annular screen body 215 is arranged in the housing, each screen body having a corresponding internal annular baffle 217. . 12. The device according to claim 11, wherein the two or more annular screen bodies are arranged concentrically and are located at virtually equal radial distances from each other within the wall of the housing. 13 Device for adding liquid 328, 32
9, 24, 25, 26, 131, 132, 21
8,219,224,225 are spaced apart from each screen body to obtain a lateral flow of liquid through substantially all of the suspension flowing through the housing during withdrawal of liquid. Apparatus according to any one of ranges 2 to 12. 14. Apparatus according to claim 13, in which many of the devices for adding liquid are arranged one behind the other in the flow direction of the suspension. 15. at least one partition wall 60 dividing the baffle cavity into separate liquid collection chambers, each liquid collection chamber having an aperture 61, 34 communicating with the surrounding liquid;
15. A device according to claim 14, comprising a separate tube for conducting liquid from the device. 16. Apparatus according to any one of claims 1 to 15, wherein the movement of the screen body is carried out in the vertical direction with a slow downward movement and a rapid upward movement.