DE102008022206A1 - Solid suspension i.e. fiber suspension, dehydrating method for closed container i.e. pressure vessel, involves applying low pressures to sectors of filter element in zones, and supplying air to water separator - Google Patents

Abstract

The method involves applying low pressures to respective sectors (6', 6'') of a filter element (5) in dehydrating zones (1, 2). One of the low pressures is utilized for dry suction of a solid layer, and air is supplied to a water separator (14). One of the low pressures is applied independent of the other low pressure. The latter pressure is produced by using a vacuum-ventilator. Separation of a solid mat is carried out with compressed air. The air in one of the dehydrating zones is utilized for dropping the solid layer in a drop zone. An independent claim is also included for a filter comprising sectors.

Description

The The subject of this invention is a process for improvement the dehydration of solid suspensions by a rotating filter, as well as a filter to carry out the Process. A rotating filter according to the invention is especially suitable for removing fibers from a pulp suspension.

To the Removal of solids, in particular fibers, from a suspension In general, rotating filters are used in operation partially immerse in the suspension to be filtered. in principle one distinguishes between disc filters and drum filters.

at Disk filters are a number of filter disks on a rotatable axle attached one behind the other. Each filter disk is in individual filter sectors subdivided, which in their interior to absorb the filtered off Liquid are hollow. Each of the sectors is by one Drain opening with the interior of the rotatable axis of the disc filter, which has its own channel per sector.

One Drum filter is as well as a filter disk in individual sectors divided by radially extending drainage channels with a control head are connected to the filter axis, the drainage takes place here over the sector surface on the drum shell.

By a control on the filter axis, the individual Channels of the filter axis or the individual drainage channels and thus also the individual sectors of a filter disk or filter drum be subjected to negative pressure independently.

in the Operation, the rotating filter dives partly into a basin, the filled with a suspension containing the solids is. If a sector in the fibrous suspension to be filtered it is submerged by the control on the filter axis with negative pressure applied, whereby the water contained in the suspension in sucked the inside of the sector and then through a channel is directed to the outside. In this process, store yourself the solid substances on the sector surface in the form of a solid layer, especially fiber mat, from. After the sector again off the pulp suspension has appeared, the solid layer sucked dry with the help of the applied negative pressure. After that will the sector concerned with normal pressure or with overpressure applied and the solid layer formed by means of water jets or scrapers detached from the sector surface and caught in a chute for further processing.

Such filters are in the DE 3542736 and the AT 232094 described. The known dewatering or filtration processes have the disadvantage that the achievable dry content of the dewatered substances is limited, since the vacuum applied to the filter and the associated suction effect must not be arbitrarily high. Too much suction would suck over the sectors that have just emerged from the suspension, too much air, which would tear off the extracted liquid flow in the channels of the filter axis and thus abruptly decrease the dewatering performance of the filter (vacuum is broken). If a dispersing system is downstream of the thickener, or if the desired exit consistency is too low to prevent carry-over in the subsequent process stages, it is necessary to add downstream dewatering units (eg screw presses or twin-wire presses), which not only results in higher investment costs connected, but can also bring technological disadvantages.

Of the Invention is therefore based on the object, an improved and gentler dewatering process with a rotating Filter, preferably disc or drum filters available that circumvents the above-mentioned disadvantages and thereby a better drainage of solids than conventional ones Procedure allows. Moreover, the invention relates a corresponding filter with which this improved drainage process is carried out.

Solved This task is assisted by a dewatering process after a first dewatering zone in which a first Vacuum is applied to a sector in a second dewatering zone a second negative pressure is applied to a sector for dry suction the solid layer serves. Sucked air becomes, after the Filter has left, fed to a water separator, in which the water contained in the sucked air separated becomes.

The drainage in two drainage zones has the advantage that an improved dehydration of solid suspensions, in particular pulp suspensions, is made possible because the negative pressure in the first dewatering zone is selected such that as much liquid as possible as little air as possible is sucked out of the suspension by the sectors, so that there is no stall in the extracted liquid flow. The second dewatering zone follows after the first dewatering zone and serves for further dewatering and dry suction, wherein air sucked through has no influence on the flow of the liquid drawn off in the first dewatering zone. Particularly well suited This method for dewatering pulp suspensions, as a gentle treatment of the fibers is possible.

In a favorable embodiment of the method, the second negative pressure is independent of the first negative pressure created, this can be the respective negative pressures independently on each optimal operating parameters regulate.

Of the second negative pressure is preferably by means of a vacuum fan generated, since thus the suction power can be controlled in a simple manner.

It is advantageous if the solid mat with compressed air instead of Water is replaced. By dropping or detaching with the help of air, a rewetting of the solid becomes Prevents substances.

A Further development is characterized in that in the second Vacuum zone extracted air for the discharge of dry sucked solid layers is used in a discharge zone. It is particularly advantageous if this extracted air again a sector located in the discharge zone supplied becomes. Respectively, this extracted air can also be in the form of a Air jet for detaching the dry-sucked solid layer be directed to the sector surface. By use the extracted air may be on a separate overpressure system be waived.

It is appropriate if this dewatering process in a closed container, preferably a pressure vessel, is carried out. This allows a closed air circulation will be realized.

Especially It is advantageous if the entire drainage in one So one-stage process carried out with a single dewatering device so that the dehydrated substances without further dewatering steps can be processed directly after the filter.

With the method of the invention can Fibers to a dry content of over 20%, preferably to be dehydrated to 25-30%, resulting in many Applications dispensed with further dewatering steps can be.

object The invention also provides a rotatable filter, wherein a filter element has multiple sectors and with a first and a second Vacuum system is connected. The second vacuum system, which Also has a water separator, it is with sectors that are at least partially above a suspension surface, connected.

With This filter, the inventive method be done very well.

In In an advantageous embodiment, the filter has an or several in a direction of the central axis in a row Filter discs on. In another advantageous embodiment the filter has a filter drum. By this known Designs, commercially available components can be used become.

Cheap this is when the two vacuum systems are independent from each other so that they are controlled separately can.

The second vacuum system may suitably have a vacuum fan, which allows easy controllability the negative pressure allows.

In a favorable embodiment of the filter one end of the second vacuum system, which is for the removal of air serves with another sector that is in the discharge zone, connected, thereby a dry-sucked solid layer of the sector surface are dropped.

In another favorable embodiment of the filter is an end of the second vacuum system, which for the removal of Air is used with an air nozzle to peel off the air Solid layer connected from the sector surface. By the detachment with the help of air becomes a rewet prevents the solid layer.

It is useful if the filter is in a closed container, preferably a pressure vessel, is arranged as a result a closed air circulation can be realized.

For a long suction zone, the chute for recording the discarded substances on the filter side, where the sectors immersed in the suspension, be arranged.

in the Following are two embodiments of the invention described with reference to drawings. Show it:

1 a schematic overall view of a filter according to the invention;

2 a schematic overall view of another variant of a filter according to the invention;

The in 1 illustrated filters 4 consists one or more filter elements 5 on a rotating central axis 8th of the filter 4 are attached. For a filter element 5 it can be a filter disk or a filter drum. A filter element 5 consists of individual sectors covered by a filter material 6 ' . 6 '' that are hollow in their interior. In the case of a filter disk, the drainage takes place via the sector surface 7 and a filter drum over the sector surface 7 ' So over the drum shell.

The interior of the central axis 8th is in a disc filter in multiple channels 22 parallel to the central axis 8th of the filter 4 run, subdivided, each of the sectors 6 ' . 6 '' through a drain opening with a channel 22 connected is. The filter 4 is in a tub 23 partially with a suspension 9 filled, so arranged that some of the sectors 6 ' . 6 '' completely in the suspension 9 dip the tub 23 forms a closed container with a cover 15 in which an overpressure can prevail for improved drainage. At the individual channels 22 the central axis 8th can via the vacuum lines 11 and 24 a negative pressure can be applied separately from each other. This is done via a control head, which is at the end of the central axis 8th is arranged.

In operation, a filter element rotates 5 in the direction of rotation A, so that on one side of the sectors 6 ' . 6 '' one after the other in the suspension 9 dip while on the other side the sectors from the suspension 9 Pop up. About the first vacuum system 17 , which can be formed by a vacuum pump, becomes in the area in the first dewatering zone 1 at the sectors in this zone 6 ' . 6 '' over the first vacuum line 11 and the channels 22 a first negative pressure applied, whereby the water from the suspension 9 through the sector surface 7 . 7 ' into the interior of the sector and then into the canals 22 and the first vacuum line 11 is sucked off. While the water is sucked into the interior of the sector, it is deposited on the sector surface 7 . 7 ' in the suspension 9 contained solid in the form of a solid layer. The first dewatering step in the first dewatering zone 1 Another dewatering step follows in the second dewatering zone 2 in which a second vacuum system 18 in this case, from a vacuum fan 13 exists, via the second vacuum line 24 a second negative pressure on the channels 22 and sectors 6 ' . 6 '' that are in the second dewatering zone 2 are being created.

The second drainage zone 2 is arranged so that the corresponding sectors 6 . 6 '' as they emerge from the suspension, are dehydrated by the applied negative pressure. This has the advantage of being on the sector surface 7 . 7 ' deposited solid layer, which is already above the suspension surface 10 be sucked dry. During the dry suction, water and air are sucked off, therefore the sucked off water-air-mixture becomes via the second vacuum line 24 a water separator 14 fed where the water is separated and through a Filtratwasserleitung 25 is passed through a water lock not shown in a Filtrattank. In the second vacuum line 24 can be used to control the negative pressure in the dewatering zone 2 also be integrated with a vacuum control.

The air freed from the water is over line 12 in the vacuum fan 13 sucked, of course, the second vacuum system 18 next to a vacuum fan 13 be formed by other devices which are adapted to generate a corresponding negative pressure. The pressure side of the vacuum fan 13 or the second vacuum system 18 is over lead 19 with a sector 6 ' . 6 '' in the discharge zone 3 in which the solid layer from the sector surface 7 . 7 ' discarded or detached. Advantageously, this connection is made via the central axis 8th of the filter 4 and the corresponding channels 22 , The sectors 6 ' . 6 '' that the drop zone 3 but can also pass at their outer edge via a valve with the air line 19 be connected, so that the air from the air line 19 enter the sector interior. The air entering the sector interior passes through the sector surface 7 . 7 ' from, whereby the dry-sucked solid layer is dropped. The discarded solids are passed through a chute 16 that are below the drop zone 3 is arranged, collected. In the illustrated 1 is the drop zone 3 and the chute 16 on the side of the filter 4 arranged at the individual sectors 6 ' . 6 '' back into the suspension 9 plunge. In another embodiment, the discharge zone 3 and the chute 16 but also on the opposite side, where the sectors 6 ' . 6 '' from the suspension 9 emerge, be arranged.

By the arrangement of the filter 4 in a closed container 15 , a closed air circulation is achieved because of the second vacuum line 24 sucked air back through the air line 19 the container 15 is supplied.

2 represents a further embodiment of the invention, wherein the reference numerals used to those in 1 correspond. In this variant, the on the pressure side of the vacuum fan 13 escaping air over the air line 19 an air nozzle 20 supplied to the air in the form of an air jet 21 exit. This jet of air 21 meets a sector surface 7 . 7 ' that are in the drop zone 3 is on, and thereby dissolves the solid layer of the sector surface 7 . 7 ' , The solids fall on a chute 16 ,

The embodiments illustrated in the drawings represent only a preferred embodiment of the invention. The invention also includes other embodiments, e.g. As filters, which are not arranged in a closed container and embodiments in which the release or the detachment of the solid layer of the sector surface 7 . 7 ' is carried out with the help of water jets and / or (compressed) air, wherein the (compressed) air can also come from a compressed air tank.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3542736 [0007]
• AT 232094 [0007]

Claims (21)

A method for dewatering solid suspensions, in particular pulp suspensions, by a rotating filter, wherein a filter element comprises a plurality of sectors to which a negative pressure is applied, wherein after a first dewatering zone, in which a first negative pressure is applied to a sector, in a second dewatering zone a second negative pressure is applied to a sector, characterized in that the second negative pressure is used to dry-suck the solid layer and thereby air sucked through a water separator ( 14 ) is supplied. Method according to claim 1, characterized in that that dehydrates with the method pulp suspensions become. Method according to claim 1 or 2, characterized that the second negative pressure independent of the first negative pressure is created. Method according to one of claims 1 to 3, characterized in that the second negative pressure by means of a vacuum fan ( 13 ) is produced. Method according to one of claims 1 to 4, characterized in that the detachment of the solid mat done with compressed air. Method according to one of claims 1 to 5, characterized in that in the second dewatering zone ( 2 ) sucked through air for the discharge of dry-sucked solid layers in a discharge zone ( 3 ) is used. A method according to claim 6, characterized in that the from a sector ( 6 ' . 6 '' ) extracted air for discharging the dry-sucked solid layer another sector ( 6 ' . 6 '' ) located in the discharge zone ( 3 ) is supplied. A method according to claim 6, characterized in that the extracted air in the form of an air jet ( 21 ) for detaching the dry-sucked solid layer onto a sector surface ( 7 . 7 ' ). Method according to one of claims 1 to 8, characterized in that the method in a closed container ( 15 ), preferably a pressure vessel. A method according to claim 9, characterized in that in the second dewatering zone ( 2 ) sucked air back to the closed container ( 15 ) is supplied. Method according to one of claims 1 to 10, characterized in that the dehydration is carried out in a one-step process, so that the dehydrated substances directly after dehydration in the filter ( 4 ). Method according to one of claims 2 to 11, characterized in that the fibrous materials to a dry content of over 20%, preferably to 25-30%, dehydrated become. Filter, which is rotatably mounted on a central axis, wherein the filter has a plurality of sectors and is connected to a first and a second vacuum system, characterized in that the second vacuum system ( 18 ) with sectors ( 6 ' . 6 '' ) at least partially above a suspension surface ( 10 ) and that the second vacuum system ( 18 ) a water separator ( 14 ) having. Filter according to claim 13, characterized in that the filter ( 4 ) one or more in a direction of the central axis ( 8th ) of the filter ( 4 ) has successively located filter discs. Filter according to claim 13, characterized in that the filter ( 4 ) has a filter drum. Filter according to one of claims 13 to 15, characterized in that the first and the second vacuum system ( 17 . 18 ) are independent of each other. Filter according to one of claims 13 to 16, characterized in that the second vacuum system ( 18 ) a vacuum fan ( 13 ) having. Filter according to one of claims 13 to 17, characterized in that one end of the second vacuum system ( 18 ), which serves to remove air, with a sector ( 6 ' . 6 '' ) located in the discharge zone ( 3 ), via an air line ( 19 ) connected is. Filter according to one of claims 13 to 17, characterized in that one end of the second vacuum system ( 18 ), which serves for the removal of air, via an air line ( 19 ) with an air nozzle ( 20 ) is connected to detach the solid layer. Filter according to one of claims 13 to 19, characterized in that the filter ( 4 ) in a closed container ( 15 ), in particular a pressure vessel, is arranged. Filter according to one of claims 13 to 20, characterized in that a chute ( 16 ), which serves to receive dehydrated solids, on the filter side where the individual sectors ( 6 ' . 6 '' ) in the suspension ( 9 ) immerse, is arranged.