CZ20003031A3 - Rotary filter - Google Patents

Abstract

The rotary filter comprises at least two adjacent annular filter plates each having a plurality of filter elements (12a / 12b, 12b / l2c) and supported each time by a rotating shaft (8) with it around the axis (C) perpendicular to the respective central plane (DC) filter plates, the filter plates being partially immersed in a container (1) adapted to contain a particular the level (L) of the liquid to be filtered and further comprises a discharge hopper (17, 52, 57) extending into the space between adjacent filter plates for discharging solids deposited on and removed from the front filter media (13) said filter elements, the discharge element being disposed the hopper has upper edges (34, 35, 56, 57, 61, 62). Axial the distance between the beer portion (34, 35, 56, 57, 61, 62) shown upper edges located radially inside the radially inner the edge portions (12 ') of the front filter means adjacent filter plates is not less than axial the distance between said inner edge portions (12 '), and an axial distance between the second portion (42, 43) shown upper edges located radially outwardly radially the inner edge portions (12 ') is not larger than said axial ones the distance between said inner edge portions front filter media.

Description

Technical field

The present invention relates to a rotary filter comprising at least two annular filter plates each having a plurality of filter elements and each supported by a shaft for rotation therewith about an axis perpendicular to the respective central plane of the filter plates, the filter plates being partially submerged in the container adapted to contain a certain level of liquid to be filtered, the filter further comprising a discharge hopper extending into the space between adjacent filter plates for discharging solids deposited on and removed from the front filter means of said filter elements.

BACKGROUND OF THE INVENTION

WO 94/24140 (US-A-5 656 162) discloses a filter in which the filter elements are arranged at a relatively large distance from the shaft and have a relatively small radial dimension, giving the filter plates an annular appearance. A filter of this type is therefore referred to as an annular filter. In this prior art ring filter, the filter means of the two adjacent filter rings have a common scraper disposed radially outside the filter rings. The scraper end of the scraper, inserted between the 25 filter rings, is guided axially and radially by sliding in a U-shaped ring formed between the filter rings and rotating therewith. The scraper also has a substantially U-shaped cross-section, thereby also serving as a hopper for the filter cake removed from the filter means.

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This prior art filter works extremely well in the light of experience. In some cases, however, it has been found that as the radial height of the filter elements increases, the amount or volume of filter cake material deposited on the filter elements becomes so large that once removed from these elements the material cannot be correctly discharged by a dump scraper passing through the rotating a channel-shaped guide ring between two adjacent filter rings. Thus, it may happen that a portion of the filter cake begins to rotate and twist between the scraper and the filter means (usually a filter cloth) of the filter element and increase its volume so that it eventually damages the filter cloth.

The present invention has as its primary object to provide

Ί E) a rotary filter of the type mentioned at the outset, which allows a substantially increased radial height of the filter sectors compared to the prior art filter.

However, large radial heights of filter elements are well known in the art, see for example US-A-3,331,512. This patent describes sector-shaped filter elements having a considerable radial size from a shaft having axially extending filtrate discharge channels therein. To receive a filter cake removed from two adjacent filter plates, a hopper is introduced into the space between the plates. The hopper extends from a position substantially above and close to the shaft to a position outside the filter plates. In a zone relatively close to the shaft, the hopper is defined by low side walls that increase significantly in height as the bottom of the hopper tilts sharply towards the outside of the plates while the upper edges of the side walls extend substantially

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0. This filter is obviously intended for processing considerable filter cake sizes. But undoubtedly, this filter concerns the same problem as above, given the apparent risk that parts of the removed filter cake may penetrate between the hopper edge and the surface of the filter sector and start to rotate and grow to a considerable thickness, resulting in damage to the filter cloth , filter sectors and / or hoppers and thereby stop filtering.

Ί Ω

Accordingly, it is also an object of the present invention to provide a rotary filter of the type mentioned at the outset which allows the removal of significant amounts of filter cake without any risk of its portions becoming trapped between the discharge means (hopper) and filter means 15 of the filter sector.

SUMMARY OF THE INVENTION

According to the present invention, said objects are achieved in that the axial distance between the radially outer edge portions of the discharge hopper located radially within the radially inner edge portions of the front filtering means of adjacent filter plates is not less than the axial distance between said radially inner edge portions and ²⁵ the radially outer edge portions of the discharge hopper located outside said radially inner edge portions is not greater than said axial spacing between said inner edge portions.

Axial and radial terms as well as derived. . ",".

shapes used in this description to indicate the direction a ·· 0 0 0 · 0 · 0 ·

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Similarly, the rotating axis of the filter shaft relates to directions perpendicular or substantially perpendicular to these axial directions.

Preferably, each filter element is radially spaced from said shaft by a spacer means such that said radially inner edge portions of the front filter means of adjacent filter elements are radially spaced from the shaft, said spacing means having a smaller axial size than said radially inner edge portions, thereby providing a space for said radially outer edge portions of said discharge hopper to be located at a greater axial distance from each other than said axial distance between said radially inner edge portions.

Preferably, the spacer means comprises guide means for discharging the filtrate from the filter element to said shaft.

In the following description, preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a top view of a typical filter according to the present invention with the top cover removed;

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Giant. 2 is a partial cross-sectional view taken along II-II in FIG. 1;

Giant. 3 shows a sectional side view taken along a plane

III-III in FIG. 1;

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0 0 ·· 0 · · ·· 0 0 0 0 0 00 0 · 00 000 0 ·

Giant. 4 is a cross-sectional view taken along the line IV-IV in FIG. 2;

Giant. 5 is an enlarged portion of FIG. 4, partially illustrating a cross section of a shaft;

Giant. 6 is a perspective view of two diametrically opposed axial channels and a portion of the shaft core;

Giant. 7 is an axial view only of the hopper of FIG. 4, illustrating in greater detail the various features of the preferred embodiment;

Giant. 8 shows a view of the hopper of FIG. 7 as seen from the left side of FIG. 7;

Giant. 9 is an enlarged top view of the hopper of FIG. 7; ·

Fig. 10 is an enlarged cross-sectional view through a preferred embodiment of a hopper illustrating its relationship to adjacent filter plates;

Fig. 11 is a view corresponding to Fig. 10 of a practical embodiment of the hopper of Fig. 10;

Fig. 12 shows a view corresponding to Fig. 10 of a second embodiment of a hopper; and

Fig. 13 is a view corresponding to Fig. 10 of a third embodiment of the hopper.

DETAILED DESCRIPTION OF THE INVENTION

The overall design of the filter will be briefly described with reference to Figs. 1 to 4. Container 1 adapted to 9 9.

To contain a certain level of liquid to be filtered (herein referred to as a suspension) has longitudinal walls 2 and 3 and end walls 4 and 5. Outside the end walls 45, bearings 6 and 7 are provided, carrying the opposite ends of the shaft 8. A shaft 8 which can be driven to rotate in the direction indicated by the arrow

A, it carries a plurality of axially extending circumferentially spaced filtrate channels 9 leading to a filtrate valve 10 at the left end of the filter, as shown in Fig. 3. Each filtrate channel 9 is connected to a plurality of axially spaced tubular tubes 11. filtrate. Each filtrate tube 11 extends in a radial direction from the respective filtrate channel 9. At its radially outer end, each filtrate tube 11 carries a filter sector 12 such that a plurality of filter sectors located in a common radial plane form a filter plate. Thus, in one filter plate, each filter sector is connected via its own filtrate tube 11 to one of the axial channels 9 for the filtrate, which is common to all filter sectors having the same angular position with respect to the shaft 8.

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Each filter sector has axially opposite surfaces in the form of a filter medium, such as a filter cloth 13, to allow the filtrate to enter the interior of the filter sector while solids, such as slurry fibers, are deposited on the surface to form a filter cake. The filtrate α is withdrawn from inside the filter sector through the filtrate radial tube 11 to the filtrate axial channel 9 and through the filtrate valve 10, which is connected to the barometric arm 14 (only the upper end of which is shown in Figs. 2 and 3). generating the vacuum required to collect the filtrate.

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To promote the initial removal of the filter cake by directing a stream of liquid, usually filtrate, towards the radially outer portions of the filter plates 12 at the rotational positions of the filter sectors near the top of each revolution, spray nozzles 15 are provided. after removing the filter cake. The hopper 17 is sandwiched between an adjacent filter plate to receive a filter cake removed from opposite surfaces 13 of the adjacent plates. The hoppers feed the filter cake material to the discharge screw 18.

Typically, the filter sectors taper toward their outer periphery symmetrically about the radial plane DC of each plate.

The arrangement of the filtrate tubes 11 as radially extending expander means for the filter sectors results in an open design allowing the suspension to flow in the axial direction along the shaft and between the spoke filtrate tubes 11 from the centrally located inlet 19 in the end wall 1 of the container 1. firstly, the suspension is centrally guided and axially distributed through the vessel 1 and secondly, it is allowed to flow radially outwardly between the filter plates, the rotating filtrate tubes 11 for each plate providing constant mixing of the suspension, resulting in uniform and optimal distribution to all filter sectors immersed in suspension. In this way, the concentration and concentration of solids in the vessel and on the outer periphery of the filter plates are eliminated. The central and axial delivery of the suspension results in an excess custom made inlet box on the longitudinal side of the container, which is

advantageous, since such an inlet box is expensive to manufacture and demanding on operation and handling, especially in relation to controlling the flow distribution along the slurry container.

In particular, as can be clearly seen from FIG. 4, the filtrate tubes connected to the filter sectors 12 are in positions close to the trailing radial edges of the sectors. Furthermore, it can be seen that the filtrate tubes 11 have a direction that is not exactly radial but substantially tangential to the periphery of the shaft 8. giving the tubes a downwardly inclined direction as the filter sectors rise above the level L of the liquid contained in the container This ensures that the filtration sectors are quickly drained of liquid and the filtrate is led to the axial channels 9.

for the filtrate at a high flow rate. It can also be seen that the filtrate tubes 11 are tilted upwardly toward the shaft in rotational positions in which the filtration sectors are just immersed in the suspension. As a result, the filtrate entering the filtration sectors effectively expels air from inside the sectors through the upwardly inclined filtrate tubes 11 and into the axial channels 9, for the filtrate.

As also shown in FIG. 4 (in combination with FIGS. 10 to 13), the filtrate tubes have a considerable length relative to their cross-section. This entails the advantage that the filtrate tube acts as a barometric arm 25 for its associated filter sector, even before the filtrate valve has connected the associated axial filtrate channel to the barometric arm 14, i.e. while the cloudy filtrate is still drained through the filtrate channel. In the upper position of the filter sector, the entire length of the filtrate tube will be added to the height of the barometric arm 14 and thereby further contribute to the suction effect.

The shape of the axial channels 9 for the filtrate is particularly evident from Figures 3, 5 and 6. In Figures 5 and 6 it is apparent that the cross-section of the channels is polygonal and extends from the distal end (which is on the right 3) towards the proximal end which is the outlet end connected to the filtrate valve 10. More specifically, the shape shown is a quadrilateral and includes a first substantially radial channel side wall 20 which is supported by and secured to the tubular shaft core 20, a lower channel wall 22, a radially outer channel wall 23 and a second substantially radial channel wall 24. The first channel side wall 20 is formed by a rectangular plate 25 whose outer edge 26 defines the outer radius of the combined shaft 8, i.e. the shaft core 21 and the axial channels 9. The lower wall 22 forms an angle with the C axis such that diametrically opposite lower walls converge towards the outlet end of the channels (see Fig. 3).

The outer wall 23 of the channel is formed by a rectangular plate 27 having one edge 28 fixed to the radially outer edge 26 of the first side wall 20. A plurality of mounting holes 29 for the filtrate tubes 11 are formed in each axial row 23 of the channel in one axial row of these tubes. The radially outer edge 30 of the second channel side wall 24 is connected to the rectangular plate 27 such that the actual outer wall 23 extends towards the outlet end of the channel. Thereby, the second side walls are inclined with respect to planes passing through the C axis, such as the horizontal plane HP in Figure 5, with the second side wall 24, which in this position is the lowest part of the channel, tilting down towards the outlet end. Since the first side wall 20 as well as the second side wall 24 are connected to the inclined bottom wall 22, it is clear that both extend towards the outlet end (see Fig. 3).

It will be appreciated that the axial channels extend not only in their cross-sections towards the outlet end, but also that the lowest portions or bottoms of the channels are inclined toward the outlet end at pivot positions in which the filtrate passes therethrough. See, for example, a channel at a position of about 3 hours where the bottom is the second side wall 24, at a position of about 1 and 2 hours where the second side wall 24 and the bottom wall 22 form the bottom, and at about 12 hours where the bottom is the bottom wall itself 22. This feature of tilting the axial channels for the filtrate contributes advantageously to the discharge of the filtrate from the filter sectors, inter alia by contributing to the vacuum generated by the barometric arm 14 and the filtrate tubes 11.

Similarly, in opposite, approximately 180 ° rotated, rotational positions where the filter sectors are submerged in suspension, the second side wall 24 and the bottom wall 22 are inclined upwardly towards the outlet end and the filtrate valve, thereby contributing to smooth air displacement.

In order to avoid the problem of catching portions of the filter cake between the upper edge of the hopper and the surface of the filter sector, it is proposed according to the present invention to arrange the hoppers so that their upper edges positioned vertically below the filter sector positions such that there is no vertical slit between these edges and the surface of the filter sector. In other words, the hopper edges and filter sector surfaces are at least located in the same vertical plane and preferably the hopper edges are offset in the axial direction of the C axis so that the hopper edge is located in a radial plane closer to the median DC radial plane. of the filter sector than to a radial plane through the radially inner portion of the filter sector.

A preferred embodiment of the hopper 17 of the present invention is shown in Figure 4, and the individual features of the hopper are shown in more detail in Figures 7 to 10. The hopper has a flat bottom 31 inclined by approximately 45 ° relative to θ horizontal plane and extending radially from the position. outside the filter sectors above the discharge screw 18 to a position above the shaft, i.e. preferably somewhat beyond the vertical plane VP (see FIG. 4), passing through the shaft axis C. In the embodiment shown, the bottom 31 is rectangular. The axially spaced, substantially vertical side walls 32, 33 extend perpendicularly from the bottom.

Starting from the upper end of the bottom 31, the side walls 32, 33 have upper, radially outer edges 34, 3.5 which are curved and have their centers in the axis C of the shaft. As can be seen in particular from FIG. 4, the radius of curved outer edges 34, 35 θ is smaller than the radially inner edges 12 'of the filter sectors 12.

7 to FIG.

10, the radially outer portions 36, 37 of side walls 32, 33 comprising a curved outer edge 34, 35 slanting outwardly along the curved lines 34 / _R 35 'aligned with the edges 34, so that the expanded open area of the hopper. This is best seen in Fig. 10, which shows the radially inner portions of three filter plates 12a, 12b and 12c, and in particular one complete hopper 17a located between adjacent plates 12a and 12b, and one complete hopper 17b located between adjacent plates 12a and 12a. 12c.

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The radially inner edges of the plates are formed by arcuate U-shaped sections 38 having rib portions 39 and spaced flanges 40, 41. In practice, each filter plate has a circularly curved U-shaped section as a common holder for all its filter sectors, the tubes 11 for the filtrate are fixed to the fin portion 39 of the U-shaped section as shown in FIG. 10. From the flanges 40, 41, each filter sector tapers radially outwardly, as is particularly evident in FIGS. 1 to 3.

The flanges therefore form the widest part of each filter sector.

To provide space for the outwardly inclined side wall portions 36, 37 and their outer edges 34, 35 radially within the filter plates, the filtrate tubes 11 extending radially in a plane perpendicular to the C axis have a smaller dimension in the axial direction of the axis than radially the inner edges 12 'of the filter plates, i.e. the rib portions 39, in which the filtrate tubes 11 are fixed. The filtrate tubes are fixed to the U-shaped sections 38 symmetrically about the central radial plane DC of each plate. Preferably, the filtrate tubes have a rectangular cross section as shown in FIG. 10.

Obviously, due to the fact that the side walls 34, 35 of the hopper side walls are located below the U-shaped section 38, i.e. the widest part of the filter sector, the filter cake material falling down along the filter sector surface will be securely trapped inside the hopper without any risk of entering a substantially axially extending, relatively small radial space remaining between the edges 34, 35 and the rib portion 39.

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Obviously, it is not possible to have the top edges of the hopper shaped as discussed above along their entire dimension towards the outside of the plates because the filter sectors must pass the hopper during their rotation. The curved edges 34, 35 are thus transformed into substantially horizontally extending edges 42, 43 which terminate at the top towards the outwardly bent portion 44, 45 of the side walls 32, 33. As shown in FIGS. the outwardly bent portions 44, 45 are bent along straight lines 44 'and 45, which gradually widens the top edges 42, 43 of the hopper to adjust the hopper to the tapered shape of the filter plates.

A practical embodiment of the hopper of FIG. 10 is shown in FIG. 11. To facilitate the installation of the hopper between adjacent filter plates, the inclined, diverging portions of the side walls 32, 33 are made as separately mountable and removable elements 46, 47 having mounting portions 4. 8, 9, which are shown fixed to the side walls 32, 33 by means of screws and nuts 50, 51.

An alternative embodiment of the hopper 52 is shown in FIG. 12. The hopper has a wider bottom 53 and straight side walls 54, 55 that are perpendicular to the bottom. The bottom width is such that the upper edges 56, 57 of the side walls are located with a margin behind the radial planes defined by the flanges 40, 41 of the U-shaped sections 38 of the adjacent filter sectors 12a, 12b and 12b, 12c.

Another embodiment of the hopper 58 is shown in FIG. 13. Here, the bottom 59 has substantially the same width as the bottom 31 of FIG. 10, i.e. less than the axial distance between the flange portions 40, 41 of the U-shaped sections 38 of the adjacent filter sectors. . The straight side walls 60, 61 of the hopper are • fl ·· flfl fl flfl flflfl · flfl flfl flflfl

• flflfl ·· · flfl • fl fl * flflfl flfl * perpendicular to the bottom. Thus, the upper edges 62, 63 of the side walls are not located below the respective inner edge of the filter sector. In order to guide the filter cake material falling from the sector to the hopper, the radially inner edges of the filter sectors are formed with protective means guiding the filter cake material to the hoppers. In practice, the flange portions 40, 41 of the U-shaped sections 38 are formed with diverging plates 64, 65 that extend over the upper edges 62, 63 of adjacent hoppers 58.

Claims (12)

PATENT CLAIMS A rotary filter comprising at least two adjacent annular filter plates each having a plurality of filter elements (12a / 12b, 12b / 12c) each supported by a shaft (8) for rotation therewith about an axis (C) perpendicular to the respective a central plane (DC) of the filter plates, wherein the filter plates are partially submerged in a container (1) adapted to contain a certain level (L) of the liquid to be filtered, and wherein the filter further comprises a discharge hopper (17; 52; 57) in the space between adjacent filter plates for discharging solids deposited on and removed from the front filter means (13) of said filter elements, the discharge hopper having upper edges (34, 35; 56, 57; 61, 62), wherein the axial distance between the first-part (34, 35; 56, 57, 61, 62) of said upper edges, located radially inside radially in the inner edge portions (12) of the front filtering means of said adjacent filter pads is not less than an axial distance between said inner edge portions (12 ') and that an axial distance between the second portion (42, 43) of said upper edges located radially outwardly of said radially the inner edge portions (12 ') is not greater than said axial distance between said inner edge portions of the front filtering means. Filter according to claim 1, characterized in that each filter element (12) is spaced from said shaft by means of a spacer (11) having a smaller dimension in the axial direction to the adjacent filter plate than the radially inner end (12 ') of said filter. filter element. • * • · Φ · * Filter according to claim 2, characterized in that the spacer means is a filtrate tube (11) connecting the filter element to the shaft filtrate channel (9). Filter according to claim 2 or 3, characterized in that said first portion of said upper edges defines an arc about said axis (C) having a first radius, and that said radially inner end (12 ') of all filter elements (12) defines a circle having its center on said axis and a second radius greater than said first radius. Filter according to any one of the preceding claims, characterized in that said upper edges (34, 35) of said first portion terminate the diverging portions (36, 37; 46, 47) of opposite side walls (32, 33) of said hopper (17). ). Filter according to claim 5, characterized in that said diverging parts (46, 47) are separately mountable and removable side wall elements. A rotary filter comprising at least two annular filter plates each having a plurality of filter elements (12) and each supported by a shaft (12). 8) to rotate it about an axis (C) perpendicular to the respective central plane (DC). filter pads, wherein the filter pads are partially submerged in a vessel (1) adapted to contain a certain level (L) of the liquid to be filtered, and wherein the filter further comprises an outlet means (17) extending into the space between adjacent filter pads for receiving; discharging solids deposited on and removed from the front filter means of said adjacent filter elements, characterized in that it comprises a combination of the following features: 98 «9 · 99 9 99 999 9 • 99 9 · 9 · 9 9 9 9 9 · 999 9 ·· · · 99 99999 ·· · a) each filter element (12) being held at a radial distance from the shaft (8) by means of a filtrate discharge tube (11), said tube having a smaller dimension in the axial direction to said adjacent filter element than 5 to the radially inner end (12 ') of said filter element; b) each solid discharge means comprising a hopper (1,7) having a lower portion (31) inclined downwardly from a position on said shaft (8) to a position radially outwardly of said filter plates, and having side 10 of a wall (32, 33) extending from said lower portion, said side walls having upper edges (34, 35) axially defining an effective axial width of said hopper relative to the solids being removed from said face filter surfaces, the axial width being not less 15 than the axial distance between radially inner ends (12 ') of adjacent filter sectors along a portion (34, 35) of said hopper disposed radially within said radially inner ends (12') of filter sectors of said at least two filter plates, and wherein said axial width is 20 less than said axial distance between radially inner ends (12 ') of adjacent filter sectors along the portion (42), 43) said hoppers located radially outside said inner ends of the filter sectors of said at least two filter plates.