JPH0357801B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating filter assembly, and more particularly to a rotary filter assembly having a plurality of annular filter discs formed by filter members, the filter members being axially spaced apart and substantially parallel. is mounted on a horizontal drum, which horizontal drum is driven by a motor and rotates in bearings within the container of the fiber suspension to be separated, and each said filter element has a wall made of taut cloth. formed by a hollow body having a cylindrical drum, the hollow body being connected via a filtrate outlet at the radially inner end to an axial outlet tube in the drum, the drum being formed as a cylindrical drum; a lattice-shaped mantle wall having an axial tube forming a discharge tube in communication with the filter member, and a collection hopper extending through the open end of the drum and into the drum, the opening being open by the drum. upwardly along all supported filter discs, the interior of each filter member being separately held at a pressure lower than the pressure on its exterior for at least one revolution of said drum. The present invention relates to a rotating filter assembly whose primary purpose is to separate fibers from suspensions.

Filter assemblies of this type are known from Swedish Patent Application No. 7406315-7 and Swedish Patent Application No.
No. 8301082-7, the latter being a further development of the filter assembly and disclosed therein. In the case of both filter assemblies, a low pressure must be created in the filter element during a certain rotation time of the filter assembly, which low pressure must be maintained for the rest of the rotation time, i.e. during the so-called removal zone. Stop.
Usually, the low pressure is provided by an external vacuum source, such as a vacuum pump, or by a valve or stop device connection between the exhaust pipe and the vacuum source, ie a so-called pneumatic leg. Vacuum pumps are expensive to install and operate, so pneumatic legs are commonly used. In order to provide a sufficiently low pressure, the pneumatic legs must be 6 to 9 meters long from the center of the filter, and they must also be straight for operation. Furthermore, they operate optimally only at certain flow ratios. If the production ratio changes from the calculated ratio, the low pressure will be reduced or not obtained at all. Another disadvantage of pneumatic legs is that when they are used, a large amount of air mixes into the filtrate, which is undesirable in the production process. This drawback is alleviated by the present invention.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rotary filter assembly as described above which has a simple filtrate drainage system and does not require conventional length vacuum pumps or pneumatic legs. The filter assembly also allows for high speed rotation and also allows for high capacity.

According to the invention, such a rotary filter assembly is provided in which each said axial tube is itself permanently connected to a filtrate storage chamber, said storage chamber being connected during a first rotation period of said drum. is adapted to maintain within itself a pressure, preferably atmospheric pressure, which causes the filtrate to collect in its accumulation chamber, and during a second rotation period of said rotating drum,
The storage chamber communicates with a filtrate discharge device, which is dimensioned to discharge filtrate from the tube and the storage chamber during this second rotation period.

Completely remove the storage chamber before the corresponding filter element comes to a position such that the storage chamber is in communication with a filtrate evacuation device arranged and dimensioned for rapid drainage of the filtrate. Fill with filtrate.

According to the invention, the rotating filter assembly operates at high rotation rates and provides a correspondingly high capacity.
Since the filtrate discharge device does not have to have a discharge pipe as long as the length of the pneumatic legs conventionally used, the pumping effort is significantly reduced, which means a reduction in operating costs. The largest field of use for the rotary filter assembly according to the invention is in the cellulose and paper industry.

The reason for the rapid draining is that a portion of the filtrate accumulates in the storage chamber, so that there is no need to transfer this amount axially at the drain. This amount of liquid, which has to be drained later, in turn absorbs the filtrate in the axial tube and filter element.

Without pneumatic legs, the total internal volume of the filter member and axial tube must be many times larger than the total volume of a corresponding conventional filter. That is, in the prior art, the filtrate has to be accumulated in said section and then passed to the filtrate discharge device and then stagnated there under waterlock conditions, thus creating a low internal pressure. For several reasons it is not appropriate to increase the volume of the filter element, so the volume of the axial channel has to be increased. Substantially increasing the volume of these axial channels would make the openings through which the removed solids must pass on their way from the filter member to the discharge conveyor too small, and solids would become trapped in these openings. The problem arises that it gets stuck.

(This problem also concerns filter assemblies with tubes arranged in groups).

The design according to the present invention has solved this problem.

Practical tests carried out with a fiber suspension of ground pulp, a common pulp, have shown that it is desirable for the storage chamber to have a volume of about 40% of the volume of the tube connected to it. The term "volume" here means the maximum volume available for the suspension. Of course, the tube body is made taking into consideration the actual flow of the filtrate. The storage chamber is the volume of the tube body.
It has become clear that an optimum low pressure can be obtained for the filter member when the volume is 40%. These tests showed that even at 15% volume, the effect of the storage chamber can already be measured.

In other tests with fiber suspensions of other grades (long-fiber kraft pulp), optimal results were obtained when the volume of the storage chamber was 5 to 10 times the volume of the axial channel (some In one case, a larger volume of the storage chamber gave adequate results).

Systems with storage chambers also have the greatest economic effect when the disks and axial tubes are standardized, e.g. 3-4 sizes, and the difference in volume of filtrate is stored by storage chambers. I understood. The change in filtrate flow occurred by a factor of about 1:20 (comparing a suspension that is difficult to dewater to a suspension that is very easy to dewater) for a given filter assembly size. If disks and filter members are standardized during manufacturing, special tools can be prepared, which reduces costs. The discs and axial tubes are mass-produced and the storage chamber can be manufactured to order for the application.

The storage chamber is suitably connected to the tube axially externally of the tube. Also, the storage room is
The tube may be connected to the tube radially outside or inside the tube, or the tube may be attached partially outside and partially inside the tube.

In a suitable embodiment of the invention, the filtrate drain device is arranged radially inwardly from the storage chamber.
It consists of two chambers, the storage chamber communicating with it via a sliding coupling. The sliding coupling is preferably arranged axially at the same level as the radially inner part of the storage chamber. In another example,
The sliding coupling is arranged radially outward from the storage chamber. The filtrate discharge device includes at least one discharge tube opening into the filtrate container. The distance from the center of the filter drum to the level of the filtrate container is typically about 2.5 to 3.5 meters. The drain tube must not be dimensioned to a certain flow rate, but must take into account the maximum filtrate flow rate. Such pipes do not need to be straightened, so they can be routed freely.

In some cases it may be effective to construct the filtrate drain into two chambers, one of which is normally a circulating flow, in order to divide the filtrate into two separate streams. It is also preferable that when viewed in the rotational direction of the drum, they are arranged one behind the other and provided with separate discharge pipes.

In one special embodiment, the storage chamber communicates with a suction channel arranged to open in one revolution of the drum, the free end of which
Beneath the liquid level created by the flowing filtrate, a low pressure is therefore created in the corresponding storage chamber, tube and filter element during the period of rotation of the drum.

In one suitable embodiment, the storage chamber is of elongated design and its outlet is located in the rear part when viewed in the direction of rotation of the drum. Thus, this rotary filter assembly is self-picking.
That is, solids are drawn into the filter element even when the level of the suspension in the filter container is low.

In certain applications, during a third period of rotation of the drum, filter solids are removed from the filter element if the storage chamber is arranged to connect with a connection to a pressure above atmospheric pressure. It is effective to make it possible.

In one particularly advantageous embodiment of the filter assembly, they are arranged in groups, as shown in Swedish Patent Application No. 8301082-7. Thus, the rotation rate of the filter assembly can be greatly increased. Two different variations of this embodiment are possible. That is, when looking at the rotation direction of the drum, there are two cases in which the periphery of each second tube is moved backward, and a case in which it is placed in the front. In these two cases as well, grouping into two groups can be considered. In embodiments in which each second tube is retracted, the filtered solids are optimally dewatered, in which case the total volume of each circumferentially displaced tube, its communicating filter element and the accumulation chamber is equal to that of the displaced tube. It is smaller than the total volume of the group of non-moving tubes, the filter elements communicating with the non-moving tubes, and the storage chamber.

Other devices are also contemplated to facilitate the removal of filter solids from the filter element. One suitable device consists of two nozzles using high pressure water or pressurized air, arranged one behind the other in the circumferential direction, on each side of each disk in the removal zone. The rear nozzle, viewed in the direction of rotation, operates intermittently, preferably with a frequency corresponding to the frequency of passage through the tube or group of tubes, and the other nozzle operates continuously. . but,
It may be preferable to operate both nozzles intermittently, preferably simultaneously. The rear nozzle should be properly oriented in the direction of rotation. The invention will now be described in more detail with reference to the accompanying drawings, in which: FIG.

In FIG. 1, a container for the fiber suspension is indicated at 1, and a rotatable horizontal filter rotor 2 is partially inserted into the container. The filter rotor 2 is formed by a plurality of annular filter disks 3, which are mounted substantially parallel to the drum 4 in a horizontal direction driven by a motor. The filter disc 3 is composed of a number of separate filter elements 5, each of which is formed as a hollow body with walls made of tension fabric, the hollow body radially extending from the inner end of the filter element 5. It is connected to an axial discharge pipe 6 via an outlet.

The drum 4 is thus formed by an axial tube 6 and gable sections 7,8. The axial tube 6 is 1
It is permanently connected to two separate storage chambers 9 ¹ which in turn ^are connected via a slip coupling 10 ¹ to a textile discharge device 11 ¹ . In Figure 1,
Although the sliding coupling 10 ¹ is shown with cylindrical rotational symmetry, it can also be designed as a planar sliding coupling 10 ² connecting the storage chamber 9 ² to the fiber discharge device 11 ² , as shown in FIG. can.

The filter rotor is rotated in a known manner by a motor, not shown. Collection hopper 1
2 extends from the open end of the drum 4 into the drum 4 and along all filter discs 3 supported by the drum 4, with the opening of the hopper facing upward. The collection hopper 12 is equipped with a conveyor screw 13. The filter rotor rotates in the direction indicated by arrow 14 in FIGS. 3 and 4, and the level of the fiber suspension in container 1 is indicated by reference numeral 15. Filter solids removal nozzles are indicated at 30,31.

For optimal functioning of a rotatable filter assembly of the type shown, the pressure acting on the inside of the filter member 5 must be such that, at certain parts of the rotary turn,
The water pressure acting on the filter element 5 below the liquid level 15 must be exceeded.

As is clear from FIG. 4, the filtrate discharge device 1
1 ¹ is divided into four areas 16, 17, 18, and 19. Zone 16 is connected to the atmosphere via tube 20 (FIG. 5), zone 17 is a first low pressure zone, and
The pressure is applied to the discharge pipe 2 which opens into the filtrate container 22.
It is given by concatenating with 1. The filtrate from this area is normally recycled. Zone 18 is a second low pressure zone whose pressure is lower than that of filtrate container 24.
It is provided by connecting with the discharge pipe 23 which opens to. The filtrate in this container is purer than the filtrate in filtrate container 22 and is commonly referred to as "clear filtrate." Zone 19 is connected via a connection 25 to a source of overpressure and has the purpose of applying overpressure to the filter element in order to rapidly remove solids from the filter element. Only one zone of low pressure may be necessary, and sometimes even the zone of overpressure may be omitted.

FIG. 6 shows an embodiment of an accumulation chamber 9 ³ which, viewed in the radial direction, is located outside the axial tube. This embodiment provides the highest capacity when used to dehydrate the filter.

Another embodiment is shown in FIG.
In this case, the storage chamber ⁹⁴ is effectively located inside the axial tube in the radial direction. In this example,
When the filter is used for maintenance recovery, the amount of fiber loss is minimal. Figure 8 shows one more
Two embodiments are shown, in which the storage chambers ⁹⁵ are located radially outside and inside the tube. This embodiment is used in special cases.

In the embodiment shown in FIGS. 9 and 10, the tubes in the second axial direction are all retracted. That is, this axial tube is 2
placed in groups. The filter member is 5 ² ,
5 ³ and the axial tubes are designated 6 ² , 6 ³ ,
The storage chambers connected to the axial tubes are designated 9 ⁶ , 9 ⁷ .

Movement of the axial tubes means that the pressure difference downstream of the filter elements is somewhat less than the pressure on the taut fabrics of these filter elements connecting to this displaced axial tube, so the filter elements and the total volume of the axial tube and storage chamber V5 ² ×V6 ² +
This drawback can be reduced by making ^V96 somewhat smaller.

Another embodiment of arranging the tubes in groups is shown in FIG. 11, in which any of the tubes in the second axis is moving forward when viewed in the direction of rotation. In this case, the first filter member ⁵⁴ is
When viewed in the direction of rotation of the drum 4, it communicates with a first axial tube ⁶⁴ located behind this first filter element, i.e. in its rear part, and a second filter element ⁵⁵ communicates with a first filter element 55. It communicates with a second axial tube ⁶⁵ arranged in group with the first tube.

Embodiments with such an axial tube and storage chamber arrangement are suitable for driving such rotary filter assemblies at very high rotation rates, resulting in a very dry density of the effluent fiber mass. Particularly effective.

In FIG. 12, an embodiment of a rotary filter assembly according to the invention is shown with a modified filtrate drain. The storage chamber ⁹⁸ is suitably formed according to FIG. 6, but in such a way that it communicates with its discharge pipe, i.e. with one suction pipe 26 bent backwards in the direction of rotation. So that there will be low pressure. The opening 27 of this suction channel is in a water lock state (the liquid level is indicated by 28) in several positions during rotation;
This creates a low pressure in the storage chamber, the axial tube and the filter element communicating with the axial tube.
The volume of the storage chamber ⁹⁸ has the size described above. The suction channel 26 can be designed in several embodiments. In all these cases, the opening of the suction channel at a certain location is in a waterlock condition.

The filter assembly according to Figures 1-5 operates as follows. That is, when rotating, the filter member 5
As it rotates into the suspension, its interior gradually fills with suspension, and a solid mass forms on the outside of the filter element. The filtrate also fills the space within the axial tubes and the storage chamber 9 before they connect with the first low pressure area 17 of the filtrate discharge device. Once such communication has taken place, the filtrate is discharged from the filter element 5 through the tube 6, through the storage chamber 9, through the area 17 and through the discharge tube 21 into the filtrate container 22. The same effect occurs when contacting area 18. Then, upon communication with the overpressure connection 25, the filter element 5 is overpressurized from within and the solid mass loosens and quickly falls through the opening 33 into the outlet hopper 12 and is then discharged by the conveyor screw 13.

The function of the embodiment shown in FIGS. 9 and 10 is the same as that of the previous embodiment, but in this case the opening between the axial tubes is larger, allowing faster rotation of the filter rotor. , the storage device can optimally take advantage of this situation in order to significantly shorten the filtrate draining time.

The embodiment shown in FIGS. 11 and 12 is generally similar to the previously described embodiment, except that the suction leg 26 begins to fill with filtrate after the storage chamber ⁹⁸ has been filled with filtrate. The suction leg is then gradually and completely filled with filtrate, its opening 27 being below the liquid level 28 and upstream of the filter, into the storage chamber, into the axial tube and into the axial tube. A low pressure is created in the communicating filter element.

During rotation, when the suction leg opening 28 is in the waterlock condition, air flows back through the suction leg and the low pressure in the filter member ceases.

Of course, other embodiments are possible within the scope of the invention. In some cases, storage chambers can also be provided at both ends of the filter rotor. The length of the discharge pipe can of course also vary, and in certain special cases pneumatic leg discharge pipes are also conceivable.

In all the illustrated embodiments, the storage chamber makes the rotation chamber higher and thus also allows the capacity to be higher. To take full advantage of this effect,
New removal spray equipment must be provided.

In the filter according to Swedish Patent Application No. 7406315-7, the removal zone is equipped with one spray nozzle that sprays continuously on each side of the filter disc. This conventional device
It has been found that there are certain problems at high rotation rates, as the axial tubes are often loaded with either large or small amounts of pulp. Such interference is
As is clear from FIGS. 3 and 9, each side of the filter member is provided with two spray nozzles 30, 31 that are continuous with each other in the circumferential direction, and when viewed from the direction of rotation, the rear nozzle 30 is operated intermittently. i.e., by allowing the axial tube, or group of tubes, to operate as it passes through the nozzle, with the second nozzle continuously operating. I can do it. An even better effect can be obtained if the rear nozzle is directed forward in the direction of rotation (angle α is greater than 0°).

(The nozzle is shown in longitudinal section in FIG. 6).

Another embodiment, the operation of which has also been proven, means that both nozzles 30, 31 spray intermittently and virtually simultaneously. A portion of the filtered solids is released each time the nozzle is actuated.

The aforementioned nozzles typically operate with high pressure water. In these cases, pressurized air is used instead of high pressure water when a high concentration of effluent pulp is required.

[Brief explanation of drawings]

1 is a longitudinal sectional view of the rotary filter assembly, FIG. 2 is a partially detailed view of FIG. 1 as a modified embodiment, and FIG. 3 is a view in the direction of the - line in FIG. FIG. 4 is a view in the direction of the - line in FIG. 1, FIG. 5 is a view of the filtrate discharge device, and FIGS. FIG. 9 is a longitudinal sectional view of the embodiment, showing the embodiment with two groups of axial tubes and shown in an enlarged view compared to FIG. 1, viewed in the direction of the - line in FIG. Fig. 10 is a view of the same embodiment as Fig. 6 when viewed in the − direction of Fig. 1, Fig. 11 is a modification of the embodiment of Fig. 9, and Fig. 12 is a view of the same embodiment as Fig. 6. 13 is a longitudinal sectional view of an embodiment with a discharge device for the filtrate consisting of a suction channel; FIG. 13 is a view in the - direction of FIG. 12; Explanation of symbols, 1... Fiber suspension container, 3... Annular filter disk, 4... Horizontal drum, 5...
... Filter member, 6 ... Discharge shaft pipe, 9 ¹ to 9 ⁸ ...
...filtrate accumulation chamber, 10 ¹ to 10 ² ... sliding coupling, 11 ¹ to 11 ² ... filtrate discharge device, 16...
First rotating portion of the drum, 17, 18... Second rotating portion of the drum, 21, 23... Discharge pipe, 22, 2
4...filtrate container, 26...suction channel,
30... Rear nozzle, 31... Second nozzle.

Claims (1)

Claims: 1 A plurality of annular filter disks 3 formed by a plurality of filter members 5, mounted to be driven about an axis, the filter disks being axially spaced from each other and substantially parallel to each other; a horizontal drum 4 loaded with a container 1 containing a fiber suspension, in which said drum can rotate;
Each filter member is formed by a hollow body having walls of taut fabric and having radially inner and outer ends, each said hollow body having a filtrate outlet at a radially inner end; is generally cylindrical and has an axial series of tubes forming a lattice-like mantle wall, the hollow body communicating with a corresponding axial tube forming a discharge tube 6 through the filtrate outlet. , a collection hopper 12 extending through an open end and into the drum therefrom is surrounded by said filter disc and extends along all of said filter discs facing upwardly towards the inlet opening; In three dimensions, a plurality of storage chambers 9 ¹ to 9 ⁸ each permanently connected to a corresponding one of said axial tubes 6 and a filling area through which the storage chambers pass in sequence as the drum rotates; a discharge zone which passes successively from the zone and includes a filtrate discharge device 11 ¹ , 11 ² , 26, each said accumulation chamber being under pressure to collect filtrate from the corresponding tube and hollow body into the accumulation chamber in the filling zone. each said accumulation chamber is capable of retaining the filtrate collected in the filling zone and the filtrate from the tube corresponding to each said accumulation chamber while in communication with said discharge device when in the discharge zone. A rotary filter assembly characterized in that it is sized to discharge substances. 2. Rotary filter assembly according to claim 1, in which the storage chambers ⁹¹ to ⁹⁸ are located axially beyond the tube. 3. Rotary filter assembly according to claim 2, in which the storage chambers 9 ¹ , 9 ² , 9 ³ are located substantially radially outside the tubes 6 . 4. A rotary filter assembly according to claim 2, wherein the storage chamber ⁹⁴ is located substantially radially inside the tube 6. 5 The storage chamber 9 ⁵ is located radially and partly inside the tube 6 and partly outside the tube 6
Rotating filter assembly as described in section. 6 Filtrate discharge device 11 ¹ radially extends into storage chamber 9 ¹
A rotating device according to claim 1, comprising at least one discharge chamber located inside the drum and a sliding coupling ¹⁰¹ for communicating the discharge chamber alternately with the storage chamber as the drum rotates. filter assembly. 7. Rotary filter assembly according to claim 6, wherein the sliding coupling 10 ¹ is axially located radially on the same level as the inner part of the storage chamber 9 ¹ . 8. Rotating filter assembly according to claim 6, in which the sliding coupling 10 ² is located axially outside the storage chamber 9 ² . 9. The filtrate discharge device 11 ¹ , 11 ² comprises a filtrate container 22 , 24 and a discharge pipe 21 , 23 leading from the discharge chamber 11 ¹ , 11 ² to the container. Rotating filter assembly. 10 Filtrate discharge device 11 ² , 11 ³ is drum 4
are placed alternately in the rotational direction of the storage chambers 9 in the radial direction.
Two discharge chambers 17 and 18 placed inside ¹ to 9 ⁸
and a sliding coupling 10 ¹ communicating with the storage chamber alternately back and forth with said discharge as the drum rotates.
10 ² and discharge pipes 21 and 23 led from each of the discharge chambers.
The rotating filter assembly according to any one of items 1 to 3. 11. A rotary filter assembly comprising means for forming a plurality of suction channels, each in communication with a corresponding one of the accumulation chambers, comprising a discharge chamber through which the filtrate passes while said filtrate discharge device forms a liquid surface. three-dimensional and having each suction channel with a free end positioned to open below the liquid surface during the rotation time of the drum, thereby creating a correspondingly low pressure in the storage chamber, tube and hollow body; A rotary filter assembly according to any one of claims 1 to 3. 12. The storage chambers 9 ⁶ , 9 ⁷ are of an elongated type and have a front end and a rear end when viewed in the direction of rotation of the drum, and each of said chambers has an outlet at said rear end.
The rotating filter assembly according to any one of items 1 to 3. 13. A rotary filter assembly according to any one of claims 1 to 3, wherein the storage chambers ⁹¹ to ⁹⁸ are in sequential communication with a source of superatmospheric pressure after the discharge zone has left. 14. A rotary filter assembly according to claim 1, wherein the axial tubes 6 are arranged in groups of at least two tubes so that the axial tubes 6 are viewed in cross section perpendicular to the drum axis. 15. A rotary filter assembly according to claim 14, wherein each second tube ⁶² is circumferentially retracted so that the tubes form two groups when viewed in the direction of rotation of the drum 4. . 16. A rotary filter set according to claim 14, wherein each second tube ⁶⁵ is moved forward with respect to the other tubes in the periphery such that the tubes form two groups when viewed in the direction of rotation of the drum. Three-dimensional. 17 The total volume of each retracted tube 6 ² , its corresponding hollow body and the storage chamber 9 ⁶ is the same as that of the retracted tube 6 ² , the non-retracted tube 6 ³ grouped with it, the hollow body and the storage chamber 9 6 . 16. A rotary filter assembly according to claim 15, which is smaller than the total volume of the chamber ⁹⁷ . 18. Two nozzles 30, 31 are placed on each side of each filter disc, said two nozzles being placed between each other around the periphery of the drum to inject high pressure fluid to facilitate the removal of fibers from the disc in the removal zone. The rotary filter assembly according to any one of claims 1 to 3, wherein 19. The rotary filter assembly according to claim 18, wherein one of the two rear nozzles 30 operates intermittently when the other nozzle 31 operates continuously when viewed in the direction of rotation of the drum 4. Three-dimensional. 20. The rotary filter assembly according to claim 18, wherein both the nozzles 30, 31 operate intermittently. 21. Rotating filter assembly according to claim 18, in which, when viewed in the direction of rotation of the drum 4, the rear one 30 of the two nozzles faces forward in said direction.