Back-wash filtering device for filtering high viscosity liquids.

(42) Date of commencement of the patent: 15.12.1993 (45) Date of issue: 25. 8.1994 (56) Documentation:

EP-A2 164932 US-PS4973406 (73) Patent owner:

LENZING AKTIEMIESELLSCHAFT A-4860 LENZING, UPPER AUSTRIA (AT).

(54) BACKWASHING FILTRATION DEVICE FOR FILTRATION OF HIGH VISCOUS LIQUIDS (57) Backwashable filter device for filtering a high viscosity liquid comprising a housing (1) having a liquid inlet port (2), a filter (3) and an outlet port (4) Having filtrate, characterized in that

- The filter (3) with its side facing the liquid to be filtered on a separating body (5) with recesses (Reject spaces) (6),

- The separating body (5) has inlet channels (7) for the liquid to be filtered, wherein the inlet channels open into the recesses (6),

- The separating body (5) one of the inlet channels (7) spatially separate drain device (8, 8 ', 8 ") for the backwashed liquid,

- The housing has a discharge (9) for the backwashed liquid and that

- The inlet opening (2) and the discharge (9) are executed closed.

The filter device according to the invention has no moving internal parts and is fully backwashable.

<img file="AT397927B_D0001.tif" />

© neeera

AT 397 927 Β

The invention relates to a backwashable filter device for the filtration of a highly viscous liquid with a housing having an inlet opening for the liquid to be filtered, a filter and a

Has outlet opening for filtrate.

A number of backwash filter devices are known in the literature. U.S. Patent 3,574,509 discloses a controllable filter for filtering a liquid. The filter element consists of two concentrically perforated cylinders which hold a very fine wire mesh between them, this structure being supported in a hollow body. A backwash arm rotates about an axis in the middle of the filter element. The backwash arm has a slot defined by mold parts which sealingly stroke the inner periphery of the filter element. The residue collected during filtration is backwashed through the slot in the arm.

From EP-A - 0 305 606 a backwashable filter system is known, wherein in the Überstauraum a filter tank a wave-like arrangement is installed so that it with a partially opened sludge water valve direct outflow of the fluidized granular filter material in the Schlammwasserabiauf - and thus the loss of Filter material - prevents.

The backwash filter according to DE-A 37 05 803 has a filter chamber into which a cylindrical filter element through which the medium to be filtered flows from the inside to the outside is inserted. This filter element has an inner cage, the cylindrical wall has substantially horizontally erstrekkende, slot-like window, which are separated by webs, and in the interior of which a filter residues discharging axially movable slide is arranged.

EP-A-0 411 163 describes a filter device with continuous cleaning of the filter surface. The device includes a cylindrical housing with an inlet opening and an outlet opening. As a filter element is a sleeve with a filtering side surface and an inner cavity. A scraper element is connected to a drive and mounted in an annulus formed between the inner surface of the housing and the filtering outer surface of the sleeve. The scraper element is designed in the form of at least one spiral belt, which comprises the sleeve and cooperates with the filter surface thereof.

Also from EP-A - 0 305 575 a backwashable filter apparatus with mechanical clearing of the filter cake is known.

The invention has as its object to provide a filter device is available, which is fully backwash without mechanical backwash, that is, without moving parts, such as scraper or backwash, the filter residue can be practically completely lifted off the filter. The said mechanical backwash aids are subject to wear, making replacement of the parts in question is necessary. In addition, mechanical, moving parts are susceptible to repair. Both leads to the fact that filter devices disassembled, or that at least must be handled in its interior. These operations are particularly expensive when a highly viscous liquid is filtered. If this medium is harmful to health, special safety precautions are necessary, making the repair even more expensive.

The inventive backwashable Fiitervorrichtung for the filtration of a highly viscous liquid has a housing which has an inlet opening for the liquid to be filtered, a filter and a discharge opening for filtrate and is characterized in that

the filter, with its side facing the liquid to be filtered, bears against a separating body with recesses,

the separating body has inlet channels for the liquid to be filtered, the inlet channels opening into the recesses,

- The separating body has a spatially separate from the inlet channels drainage device for the backwashed liquid,

- The housing has a derivative for the backwashed liquid and that

- The inlet and the discharge are designed to be closed.

The separator serves to largely separate the liquid to be filtered from the backwashed liquid. During backwashing, the residue removed from the filter (Fteject) firstly reaches the recesses, which are referred to below as reject chambers due to their function, and via the drainage device, which is spatially separate from the inflow channels, to a drain which is best attached to the filter housing. Channels can also be provided as drainage device, which lead from the reject spaces through the separating body for discharge. As drainage device but also a system of grooves is conceivable, which extend along the filter-facing surface of the separating body and thus discharge the backwashed liquid laterally to the outside.

It has been shown that Fiitervorrichtung invention is fully backwash, that is, that by rewinding of filtrate deposited in the filter residues almost completely back from the filter

AT 397 927 Β can be lifted off and rinsed out if the backwash liquid has a viscosity of at least

Has 0.4 Pa.s. The Fiitervorrichtung invention works due to the separating body without moving internal parts. The filtration and backwashing processes are controlled only by means of pumping and shut-off devices. Furthermore, no filter drive is required.

The filter device according to the invention is particularly suitable for the filtration of highly viscous cellulose solutions, Polyacryilösungen, polyester solutions and - since it is completely closed and can be used as a so-called in-line filter device - for the filtration of highly viscous aggressive, abrasive and harmful solutions. The device according to the invention does not require a dynamic seal to the outside.

The filter device according to the invention also allows internal flushing with chemical solvents.

The effect of the invention is independent of the filter material used, whereby the appropriate filter can be used for the respective liquid to be filtered. A restriction to certain filter materials is therefore not required. Common filter materials include metal fiber webs, sintered webs, combinations of metal fiber webs with webs, and plastic mesh webs.

The geometric shape of the Rejecträume is largely irrelevant for the achievement of the effect. However, it is obvious that the reject spaces should be shaped in shape so as to avoid low flow velocity locations. At these locations, the residues of the backwashing liquid lifted off the filter during the backwashing process are only made more difficult or only partially taken. In contrast, hemispherical, dome-shaped or groove-shaped reject chambers are well suited, the inlet channels advantageously opening at the lowest point of the reject chambers. The radius of the reject chambers must of course be adapted to the filter material and the pressures occurring during backwashing at the filter in order to mechanically support the filter so that it does not break. Of course, a mechanical support is also provided on the side of the filter facing the outlet opening, in order to avoid tearing or deformation of the filter due to the high pressures required for the filtration. Such a support offers, for example, the filtrate plate described below, which has continuous channels for the passage of the filtrate.

For economic reasons, the Rejecträume should be made small, so that the residues can be flushed out with as little liquid. The precisely defined reject spaces also allow a precisely adjustable reject quantity without changing the quantity.

A preferred embodiment of the filter device according to the invention is that the drainage device is designed as a channel-like system with drainage channels and collecting channels.

In this embodiment, an efficient discharge of the backwashed liquid from the reject chambers is realized. The drainage channels are short channels that connect the reject chambers to the longer collection channels. The drainage channels expediently have a smaller diameter than the collecting channels. The small diameter prevents, together with the high viscosity of the liquid, that after a backwashing approximately in the drain or Collective channels located, lifted from the filter residue during the subsequent filtration back into the reject chambers and so again on the filter. It is further expedient to make the inlet channels tapered at their mouth in the recesses.

The invention also relates to a separating body for use in the filter device according to the invention, which is designed as a plate (partition plate) and further characterized in that

the axes of the inlet channels and the collecting channels are substantially normal to each other,

- The recesses are hemispherical, dome-shaped or configured as grooves,

- The junctions of the inlet channels are provided at the lowest point of the recesses, and

- Lead from each recess at least two drainage channels to collecting channels.

The partition plate allows the execution of all necessary for the loading and backwashing of the filter material functions. It has been shown that the pressure loss in the separating plate is negligible compared to the pressure loss of the filter material.

A preferred embodiment of this Trennpiatte is that the Zutaufkanäte are tapered at the junctions and that the Ablaufkanäfe have a smaller diameter than the collecting channels.

If the reject spaces of the separating mat according to the invention are provided in a rippled fashion, then it has proven to be favorable to make the grooves between 1 and 5 mm wide and to arrange them in parallel.

The separation board is best equipped with 15,000 to 25,000 inflow channels per square meter and with 3Q.00Q to 40,000 drainage channels

The design of the separator as a plate opens up the possibility of arranging several filters one above the other in one housing and thus to increase the filter area.

AT 397 927 Β

Such a variant of the filter device according to the invention consists in that

two separating plates each having an adjacent filter are provided, the separating plates facing the filter-carrying sides facing each other,

- And that between the partition plates, a filtrate plate is provided for supporting the filter and for discharging the filtrate.

As a filtrate plate is generally suitable any plate-shaped body which has a sufficient bending strength to support the filter during the filtration process and which has channels for the removal of the filtrate. Since in the embodiment described filtrate penetrates both through the top and through the bottom through channels in the filtrate, are advantageously in the interior of the filtrate longitudinal channels (eg in the form of holes), which run parallel to the top and bottom of the filtrate plate and are connected to the channels opening from the top and bottom, receive from this filtrate and dissipate laterally. The dimensioning of the filtrate plate, ie their strength, the number of channels, etc. can be adapted to the respective purpose.

Of course, in order to avoid unwanted mixing of the individual liquid media, the feed of liquid to be filtered, the outflow of filtrate and the outflow of backwashed liquid must be spatially separated from each other, which however can be provided by a person skilled in the art in a simple manner.

The separating plates can be covered to the outside by inlet plates, which likewise have channels through which the liquid to be filtered is distributed or introduced into the inlet channels of the separating plates.

A further advantageous embodiment of the filter device according to the invention is sandwiched by a plurality of filter units, wherein a filter unit consists of a feed plate and two separator plates, each with a filter, which are separated by a filtrate plate consists.

It has proved to be easier to clean individual filter devices as appropriate, not to filter with a single device, but with a filter system consisting of several filter devices, which are connected in parallel.

The invention will be explained in more detail with reference to the drawing, which in FIG. 1 shows a plate-like configuration of the separating body 5 and in FIG. 2 a simple embodiment of the filtering device. In Figure 3, the operation of a filter system is shown, which consists of two parallel filter devices.

FIG. 1a is a perspective, schematic representation of the separator body 5 designed as a plate. Reference numeral 7 stands for the inlet channels through which the liquid to be filtered is pressed to the recesses (reject spaces) 6 and subsequently through the filter (not shown). With 5a that side of the partition plate 5 is designated, which faces the liquid to be filtered. The reject spaces 6 are located on the underside 5b of the partition plate 5. The collecting channels 8 'extend through the entire partition plate 5 parallel to each other and parallel to the top and bottom 5a and 5b. The two collecting channels 8, which collect the backwashing liquid emerging from the collecting channels 8 'during backwashing, need not necessarily extend over the entire width of the separating plate. The bottom 5b - and thus the recesses 6 - are covered by the filter (not shown). The partition plate 5 according to the invention may have further collecting channels (not shown) in its interior, which backwashed liquid from the drainage channels 8 in a direction other than in FIG. 1b, discharge to the outside.

FIG. FIG. 1b shows, for a better understanding of the channel-like system in the interior of the separating plate, again the separating plate according to FIG. 1a, which, however, a part was cut out. You can see the Reject spaces 6, which are executed dome-shaped. The inlet channels 7 are formed tapered at the mouth into the reject chambers 6. The diameter of the inlet channels is preferably between 1 and 6 mm. The diameters of the drainage channels 8 and the collecting channels 8 'are preferably between 1 and 5 or between 4 and 10 mm. The liquid backwashed through the filter into the reject chambers 6 flows from the reject chambers 6 through the drain channels 8 into the collecting channels 8 'and 8. The partition plate 5 shown has two collecting channels 8, which are located on two opposite sides of the partition plate 5.

FIG. 1c shows a section of the separating plate 5 along the line cc of FIG. ta. In this illustration, only the collecting channels 8 can be seen from the drainage device for the backwashed liquid. The collecting channels 8 'were indicated by dashed lines; the Abtaufkanäle 8 are not visible after this illustration. The axes of the Zuiaufkanäle 7 and the collecting channels 8 'are indicated by x and y in the illustrated embodiment of the partition plate are the axes x and y normal to each other.

The size of the partition plate depends on the amount of pressure applied to the inside of the hipper. In the case of a groove-like execution of Rejecträume results in a groove width of 4 mm (at

AT 397 927 Β a distance of adjacent grooves of 1 mm) and with a separator plate size of about 250 x 1000 mm (the area available for the filter) a free filter surface of about 0.2 m², The partition plate can be additionally supported by a web or support points in the middle of the plate.

In the following, some typical data are given for the embodiment of the separating plate shown in FIG. 1a, which is particularly suitable in a filter device for the filtration of highly viscous, spinnable cellulose solutions (eg NMMO solutions):

<td>Length:</td><td>1,000 mm</td>

<td>Width:</td><td>350 mm</td>

<td>Thickness:</td><td>10 - 20 mm</td>

<td>Material (exemplary):</td><td>Steel, plastic, aluminum</td>

<td>Number of inlet channels (7):</td><td>4100</td>

<td>Diameter top / bottom:</td><td>2-5 mm / 1 - 3 mm</td>

<td>Number of exit channels (8):</td><td>8,000 - 9,000</td>

<td>Diameter:</td><td>1 - 3 mm</td>

<td>Number of collection channels (8 '):</td><td>80-90</td>

<td>Diameter:</td><td>4 - 6 mm</td>

<td>Number of collection channels (8):</td><td>2</td>

<td>Diameter:</td><td>6-10 mm</td>

<td>Diameter of dome-shaped reject spaces:</td><td>2 - 4 mm</td>

Fig. 2 shows a section through a filter device according to the invention in a simple embodiment, wherein as a partition plate 5 that is provided in Fig. 1 described. 1, the housing of the device is designated, 2 and 4 stand for the inlet and outlet opening. The filter 3 is applied to the partition plate 5 and that on the side which has the reject spaces 6.

The function of the filter device shown in Fig. 2 is as follows:

The highly viscous liquid to be filtered is conveyed by means of a booster pump 10 with the valve 11 open and with a closed discharge 9 (closure not shown) through the inlet opening 2 under pressure on the separator plate 5. The partition plate 5 is shown in section 2 in section along the line cc of FIG. 1a. The liquid penetrates through the Zulaufkanäie 7 in the reject chambers 6 and is pressed by depositing the substances to be filtered (residue) through the filter 3. The filtrate passes through a filtrate plate 12, which has filtrate channels 13 and supports the filter 3, to the outlet opening 4 and can be recovered there.

For backwashing the valve 11 is first closed, the discharge line 9 is opened and filtrate under pressure (pressure generation not shown) through the outlet opening 4 and the filtrate plate 12 is pressed through the filter 3, wherein the filtered residue is lifted. The residue which collects in the reject spaces 6 is subsequently fed through the (in FIG. 2 not visible, in Fig. 1 b) flushed out into the collecting channels 8 'and 8 and can be removed via the outlet 9 of the filter device.

In Figure 2, only the design features of the filter device necessary for understanding the invention have been shown. It goes without saying that provided for example in the housing suitable brackets for the individual plates and that the plates must be sealed against each other to avoid unwanted mixing of the individual liquids.

Fig. 3 shows a variant of the filter system according to the invention consisting of two parallel filter devices A and B according to the invention with filters of the same size 3. The filter devices are shown only schematically, since their operation has already been explained with reference to Figures 1 and 2. Reference numerals A and B stand for each of the described embodiments.

Both filter units are initially charged with open valves 11 and 11 'with liquid to be filtered by means of the booster pump 10. For filtration the Verrtil 11 is opened, the discharge valves 11 'and 11 are closed. During the Fittraöan between 2 and 4, a pressure difference is established between the inlet and outlet.

In order to rewind the filter device B, the valves 11 'and Tt "are closed and the discharge valve 11' is opened. As a result, filtrate from the filter device A flows in the opposite direction through the device B, thereby purging the filter 3 located in B. The loaded with residue filtrate is forced through the opened discharge 9 from the Fiitervorrichtung B.

In order to rewind the filter device A, the valves 11 and 11 are closed and the discharge valve 1Γ 'is opened. As a result, filtrate from the filter device B flows in the reverse direction

AT 397 927 Β through filter device A and thereby flushes the filter 3 located in A free. The loaded with residue

Filtrate is forced through the opened outlet 9 'from the filter device A.

The filtrate delivery rate required for backwashing can be conveniently set via the booster pump 10 and thus adapted to the respective conditions exactly. By increasing the speed of the pump 10, a higher backwashing performance can be set, thereby achieving better cleaning of the filter.

According to the invention, more filter devices can be connected in parallel to form a filter system, whereby even higher backwashing performance can be achieved.