FILTER SYSTEM FOR VISCOUS OR HIGHLY VISCOUS LIQUIDS, IN PARTICULAR PLASTIC MELTS AND METHOD FOR FILTERING VISCOUS OR HIGHLY VISCOUS LIQUIDS

Abstract

A device and a method for filtering viscous or highly viscous liquids, in particular plastics melts, includes use of an oscillating filter plate.

Claims

1. A filter system comprising: a filter chamber which defines an active filter area in a filter zone; at least one cleaning chamber connected to the filter chamber; a filter plate arranged in the filter chamber, the filter plate being at least twice as wide as the active filter area; and a filter support plate arranged in the filter chamber, the filter plate being supported by the filter support plate, wherein the filter plate is movable to the at least one cleaning chamber to clean the filter plate, wherein either (i) the filter plate is guided on the filter support plate, by sliding elements in grooves, in an oscillating motion relative to the filter support plate to clean the filter plate, or (ii) the filter support plate is guided in the filter chamber by sliding elements such that the filter plate together with the filter support plate is guided in an oscillating motion to clean the filter plate.

2. (canceled)

3. The filter system according to claim 1, wherein the at least one cleaning chamber is sealed relative to the filter chamber by one or more blocking elements.

4. The filter system according to claim 1, further comprising a cleaning apparatus in the form of a scraper unit.

5. The filter system according to claim 1, wherein the filter plate takes the form of a plate, sheet or mat.

6. The filter system according to claim 1, wherein a conveying screw is provided in the at least one cleaning chamber for discharging a filter cake.

7. A method for filtering viscous or highly viscous liquids, comprising: supplying the viscous or highly viscous liquid to a filter chamber which defines an active filter area in a filter zone, the filter chamber having a filter plate supported by a filter support plate, the filter plate being at least twice as wide as the active filter area, wherein either (i) the filter plate is guided on the filter support plate, by sliding elements in grooves, in an oscillating motion relative to the filter support plate, or (ii) the filter support plate is guided in the filter chamber at the bottom and/or sides by sliding elements such that the filter plate together with the filter support plate is guided in an oscillating motion; supplying the viscous or highly viscous liquid to the filter chamber through an inlet opening; carrying away the liquid passing through the filter plate; moving the filter plate to a cleaning chamber; and carrying away contaminants present on the filter plate by way of the cleaning chamber.

8. The method according to claim 7, wherein the carrying away of the contaminants present on the filter plate is performed by a back-flushing process initiated by a pressure difference up- and downstream of the filter plate.

9. The method according to claim 7, wherein the carrying away of the contaminants present on the filter plate is performed by a back-flushing process initiated by sealing a back-flushing zone.

10. The method according to claim 7, wherein the carrying away of the contaminants present on the filter plate is performed by using conveying devices.

11. The method according to claim 7, wherein during cleaning of the filter plate, the viscous or highly viscous liquid continues to flow through the filter plate in the filter zone.

12. The filter system according to claim 3, wherein the one or more blocking elements may be moved mechanically, under the control of levers or links, by a reciprocating motion, by springs, by melt pressure, or independently electrically, mechano-pneumatically or hydraulically.

13. The filter system according to claim 3, wherein the one or more blocking elements are formed with an integral valve, by which a filter cake is removable from the cleaning chamber.

14. The filter system according to claim 1, further comprising first and second cleaning chambers arranged on opposite sides of the filter zone, respectively.

15. The filter system according to claim 1, further comprising first and second blocking sliders arranged on opposite sides of the filter zone, respectively.

16. The filter system according to claim 1, further comprising first and second slider elements arranged on opposite sides of the filter support plate, respectively.

17. The filter system according to claim 14, wherein the filter plate and the filter support plate are arranged such that, due to either the oscillating motion of the filter plate relative to the filter support plate or the oscillating motion of the filter plate together with the filter support plate, one portion of the filter plate can be filtering by flowing unfiltered liquid from an unfiltered chamber through the active filter area to a filtered chamber, while another portion of the filter plate is being cleaned in one of the first and second cleaning chambers.

18. The filtration system according to claim 1, wherein the filter plate is selected from the group consisting of a belt, a sheet, a plate or a mat.

19. The filtration system according to claim 15, wherein each of the blocking sliders includes an integral valve.

20. The filtration system according to claim 19, further comprising first and second cleaning chambers arranged on opposite sides of the filter zone, respectively, each cleaning chamber having a discharge duct, wherein each of the blocking sliders defines a fluid passage capable of permitting any back-flushed liquid to flow to the discharge duct of one of the cleaning chambers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIGS. 1 to 9 show embodiments according to the invention. In particular:

[0073] FIGS. 1a-1c show a method for cleaning the filter;

[0074] FIGS. 2a-2c show a method for cleaning the filter with free back-flushing;

[0075] FIGS. 3a-3c show a filtration method with forced back-flushing;

[0076] FIG. 4 shows an embodiment of the filter;

[0077] FIG. 5 shows an embodiment of the filter in which only the filter plate is oscillated;

[0078] FIG. 6 shows an embodiment for conveying away the filter cake;

[0079] FIG. 7 shows an embodiment in which the filter cake is conveyed away in a controlled manner by a conveying screw;

[0080] FIG. 8 shows cooling ducts in the cleaning chamber for conveying away the filter cake; and

[0081] FIG. 9 shows an embodiment according to FIG. 7, in which the pressure is reduced by active cooling by cooling ducts.

DETAILED DESCRIPTION OF THE INVENTION

[0082] In the description below, the following reference numbers are used: [0083] 1 the filter chamber [0084] 2 the filter plate [0085] 3 the filter support plate [0086] 4 the contaminants (filter cake) [0087] 5, 5a a cleaning chamber [0088] 6, 6a a blocking slider with integral valve [0089] 7 the discharge duct in the cleaning chamber [0090] 8 plain bearings [0091] 9 a conveying screw for conveying away the filter cake [0092] 10 the viscous or highly viscous liquid to be filtered, for example the plastics melt to be filtered [0093] 11 the filtrate of the viscous or highly viscous liquid [0094] 12 a blocking element [0095] 13 an insulating layer [0096] 14 heating or cooling ducts [0097] 15 the melt chamber for back-flushing [0098] 15a the back-flushed melt [0099] 16 the slider for moving the filter or the filter support plate [0100] 17 the melt inlet [0101] 18 the melt outlet [0102] 19 a shut-off element for forced back-flushing [0103] 20 solidified contaminant material [0104] 21 the cleaning zone [0105] 22 the filter zone.

[0106] FIGS. 1a-1c show a method for cleaning the filter in which the filter is cleaned without back-flushing.

[0107] The device consists in this respect of a filter chamber 1 and a filter plate 2, which is supported by a filter support plate 3.

[0108] As shown in FIG. 1a, the contaminants settle on the filter plate 2 as filter cake 4 during the course of the process of filtering a viscous or highly viscous liquid 10.

[0109] To clean the filter plate 2 of the filter cake 4, the valve 6, which in this case takes the form of a piston, is actuated and the filter cake 4 is passed into the cleaning chamber 5 and removed from the cleaning chamber through the duct 7. Removal of the filter cake 4 proceeds by displacing the filter plate 2 optionally together with the filter support plate 3 in the direction of the arrows, wherein the filter plate 2 is transported to a second cleaning chamber 5a and the process for complete cleaning of the filter plate is carried out.

[0110] FIGS. 2a-2c show a method for cleaning the filter with free back-flushing.

[0111] Here, the pressure difference up- and downstream of the filter plate 2 which arises during cleaning of the filter ensures that some of the filtrate 11 from the melt chamber is forced back for back-flushing 15 through the filter support plate 3 and the filter plate 2 in the back-flushing zone 21 below the filter cake 4 (FIG. 2b). The filter cake 4 is lifted up by the back-flushed melt 15a and in this way forced more readily into the duct 7 of the cleaning chamber 5.

[0112] Removal of the filter cake 4 proceeds by displacing the filter plate 2 optionally together with the filter support plate 3 in the direction of the arrows, wherein the filter plate 2 is transported to a second cleaning chamber 5a and the process for further cleaning of the filter plate is carried out.

[0113] FIGS. 3a-3c show a filtration method with forced back-flushing. Here the back-flushing process is initiated by sealing the back-flushing zone 15 by the slider motion. The filter system here comprises an additional shut-off element 19. The material is forced through the filter from below with elevated pressure and the filter plate cleaning process is carried out as in the procedure shown in FIG. 2.

[0114] FIG. 4 shows an embodiment of the filter, in which filter plate 2 and filter support plate 3 oscillate together, i.e. are pushed to and fro. The filter support plate 3 is here mounted in the filter chamber 1 on plain bearings 8.

[0115] FIG. 5 shows an embodiment of the filter in which only the filter plate 2 is oscillated. In this case, the filter plate 2 is mounted on plain bearings 8 which are situated on the filter support plate 3.

[0116] FIG. 6 shows an embodiment for conveying away the filter cake 4 out of the cleaning chamber. In this case, in duct 7 modification of the cross-section reduces the pressure from a pressure level P1 to a pressure level P0, the filter cake 4 thereby being conveyed out of the duct

[0117] In FIG. 7, filter cake 4 is conveyed away in a controlled manner by means of a conveying screw 9.

[0118] In FIG. 8, cooling ducts 14 are provided in the cleaning chamber for conveying away the filter cake 4, such that the pressure in the cleaning chamber is reduced by cooling. The insulating layer 13 serves to decouple the temperature of the discharge duct 7, and thus the temperature of the material to be discharged may be reduced and the viscosity increased by a lower temperature than in the filter.

[0119] FIG. 9 shows an embodiment according to FIG. 7, in which the pressure is however reduced by active cooling by cooling ducts 14. Solidified material thereby exits from the end of the discharge duct 2.