Candle filter components

Abstract

The present invention relates to a candle filter component for installation in a pressure vessel or for implementation in a tank or aquarium open to the atmosphere, the main parts of which are a fastening device for connection to a housing, a joint connecting the support and the fastening device, a support for a filter material with an integrated immersion channel, and a base.

Description

[Technical field]

[0001] The present invention relates to a candle filter component for installation in a pressure vessel or for implementation in a tank or aquarium open to the atmosphere, the main parts of which are a fastening device for connection to a housing, a joint connecting the support and the fastening device, a support for a filter material with an integrated immersion channel, and a base. [Background technology]

[0002] The present invention is used in the field of solid-liquid separation, more specifically in cake filtration. Cake filtration is characterized in that particles from a suspension are deposited on the surface of a filter material, such as a filter cloth, to form a filter cake. Generally, filter cloths are made of non-woven or woven fabrics, or permeable membranes, all of which are referred to as filter cloths for the purposes of the present invention.

[0003] The support, which serves as the main component of the candle filter component and supports the filter fabric, is already known from German patent specification 3249756, C2. In this prior art, the support is a perforated cylindrical body, which is mounted vertically inside the feed chamber of the pressure vessel. The filter fabric, which has the shape of a hose, is mounted on the outside of the cylindrical body and fastened to its lower and upper ends. The filter candle is closed at its lower end and open at its upper end. The open upper end of the filter candle is attached to a perforated plate body which separates the chamber receiving the filtrate, called the filter chamber, from the (suspension) feed chamber, and thus has an open connection to the filter chamber. This connection allows the filtered fluid to flow from the candle interior into the filter chamber after passing through the filter cake and the filter fabric. During the backwash procedure, the flow is reversed, whereby the filtered fluid flows from the filtrate chamber into the candle and passes through the filter fabric in the reverse / opposite direction. This process of reversing the flow is intended to remove the filter cake from the filter fabric and to remove particles from within the pores in the porous filter fabric, which then leads to clogging of the fabric, thereby preventing flow over an extended period of time. In some process designs, backwashing is supported by the use of pressurized gas to drive an increasing amount of the filtered fluid or fluid-gas mixture through the filter fabric.

[0004] An important design parameter of such filtration systems is the filter area that can be accommodated in the filtration system. By decreasing the diameter of the filter candles as well as increasing the length of the filter candles, the filter area that can be accommodated in a given diameter filter vessel is increased, thereby reducing the cost per filter area and, therefore, the cost per fluid flow filtered. Filter candle lengths of 1-2.5 m and filter candle diameters of 25-120 mm are state of the art.

[0005] One of the most important performance parameters is the backwash efficiency, which means the ability to completely remove the filter cake from the filter fabric and the particles trapped inside the pores of the filter fabric. The backwash efficiency increases in proportion to the fluid flow through the entire surface of the filter candle during backwashing.

[0006] In prior art filter candles, the fluid flow during backwashing is limited by the length to diameter ratio and by the pressure loss that occurs from the top of the filter candle to the bottom of the filter candle, where the filtered fluid enters the filter candle. Tests have demonstrated that for a filter candle with a diameter of 80 mm, only the top 300 mm of the filter candle provides a reasonable fluid flow for cleaning the filter candle with an aqueous solution. The remaining length of the filter candle will not get a reasonably sufficient flow of filtrate to permanently clean the filter fabric. This requires frequent changes of the filter fabric, which leads to high operational costs for the filter fabric and the labor time required to replace the filter fabric.

[0007] A means for improving this insufficient backwashing is described in US Pat. No. 4,604,201. It consists in introducing a dip tube inside the filter candle, which reaches its open bottom and is thereby connected to the inner chamber of the filter candle. The upper side of this dip tube is connected to a filter header which forms the outlet for the filtered fluid from the filter candle. During backwashing, the filtered fluid inside the filter header is inverted by applying pressurized gas to the filter header. This pressurized gas forces the fluid down the dip tube and up through the free space of the candle surrounding the dip tube, passing through the filter fabric from inside to outside. When the fluid level reaches the lowest point of the dip tube, a very high flow rate is achieved due to the low pressure resistance of the gas in the dip tube. This high flow rate, together with the high turbulence achieved by the pressurized gas introduced at the bottom of the filter candle component, leads to a more successful backwashing compared to the prior art.

[0008] The support shown in this patent is made of long bars of individual profile, reinforced by cross bars that attach it to the dip tube. A drawback of this design is that the support structure is limited by the number of long bars and the complexity of its manufacture (e.g., fixing each single bar on the dip tube by welding, etc.). However, sufficient support structure for the filter fabric is important for the life of the filter fabric, which would break if the spacing between two long bars were too wide.

[0009] An improvement to the above system is described in U.S. Pat. No. 4,473,472. A bundle of perforated tubes is used as a support for the filter fabric. However, this design, which is driven by a pressure drop through the perforated tubes during backwash, still has a limited backwash efficiency. At this stage, the filtrate flows in the opposite direction again, through the perforated tubes and then through the filter fabric. The pressure drop through the perforated tubes reduces the flow rate of the filtrate and, therefore, the velocity through the filter fabric. However, to obtain the best backwash effect, a high flow rate is required, as mentioned above.

[0010] Another parameter to ensure efficient backwashing is to provide a sufficient filtrate volume during backwashing. In the prior art, backwashing is a combination of a filtrate flow followed by a gas flow. Some areas of the fabric are washed with filtrate, while the remaining parts are washed with a gas flow. This leads to different backwashing efficiencies over the length of the fabric. To prevent this, the present invention proposes to have a volume inside the dip tube large enough to compensate for the volume that occurs between the fully expanded fabric and its support during backwashing. In other words, the volume inside the dip tube must compensate for the above-mentioned increase in space caused by backwashing.

[0011] Prior art designs are unable to buffer the amount of filtrate required for efficient backwashing in the filter candles.

[0012] Another step in the procedure for removing solids from the filter fabric includes a dry cake discharge and fabric washing step, in which pressurized gas is introduced from the suspension side to discharge the dry cake, to drive the remaining fluid out of the filter vessel and the filter candle, and to further dry the filter cake on the filter candle. Then, pressurized gas is applied from the filtrate side in a counterflow direction to the filter candle components. This leads to a sudden movement of the filter fabric in the form of an increase in the diameter of the filter fabric. This movement causes the filter cake to detach from the filter fabric, allowing it to descend and be discharged from the filter vessel through the bottom gate valve. The support that is out of round shape promotes the detachment of the filter cake from the filter fabric. This is due to the movement of the filter fabric during expansion.

[0013] One embodiment taking this into account is shown in U.S. Pat. No. 4,473,472, in which the shape of the filter fabric changes during filtration from a star-like shape provided by the support of six perforated tubes to a round shape by the application of pressurized gas from within.

[0014] A second embodiment is described in U.S. Pat. No. 4,968,424, in which the filter candle has a cricket bat shaped cross section which also determines the shape of the filter fabric during filtration and the starting point of the movement of the filter fabric before it is forced into a round shape by the application of pressurized gas from within.

[0015] According to the prior art, all systems have complex designs of supports to form pressure-stable structures, which require a lot of labor and material, and in some cases very valuable and high-grade materials for their excellent corrosion resistance, which today are of paramount importance to conserve precious resources. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] German Patent Specification No. 3249756, C2 [Patent Document 2] United States Patent No. 4,604,201 [Patent Document 3] United States Patent No. 4,473,472 [Patent Document 4] United States Patent No. 4,968,424 Summary of the Invention [Problem to be solved by the invention]

[0017] The problem to be solved by the present invention is to provide a candle filter component which overcomes the above-mentioned drawbacks, simplifies the design of such components, reduces manufacturing costs, and improves the efficiency of cake discharge and backwashing of particles from the filter fabric. [Means for solving the problem]

[0018] It is an object of the present invention to provide a filter component comprising a support and a filter fabric disposed around the support, the support having a centrally located submerged channel and outer longitudinal channels.

[0019] Preferably, the support of the filter component according to the invention is formed of a continuous profile, more preferably a continuous extruded profile, preferably comprising a thermoplastic material. Alternatively, the extruded profile may be made of another extruded material, for example metal (aluminium, steel, etc.) or glass. In principle, ceramic materials are also suitable.

[0020] Preferably, the outer contour of the support of the filter component according to the invention may be circular, star-shaped, cricket bat-shaped or elliptical.

[0021] Preferably, in the filter component according to claim 1, the central tube forms an immersion tube, and the long rod-shaped member is attached to the central tube.

[0022] In a preferred embodiment of the invention, the outer longitudinal channels are formed by longitudinal walls in a support material having rounded outer edges and are covered by a filter fabric.

[0023] Preferably, the submerged channel volume is at least 1% greater than the total differential volume of all outer longitudinal channels of the same filter component, preferably between 1% and 5% greater.

[0024] In a preferred embodiment of the present invention, the filter fabric is a hose-shaped filter fabric. It is preferably fixed to the filter component by fabric fastening elements, in particular one fabric fastening element at the lower end of the longitudinal flow area of ​​the candle filter component and one fabric fastening element at the upper end of the longitudinal flow area. In this embodiment of the present invention, the fabric fastening elements also seal the filter chamber against the feed chamber.

[0025] Preferably, the filter component further comprises a connection between the support and the fixing device and a pin for optimal positioning of the filter component within the filter device.

[0026] Preferably, the filter fabric is secured above the joint and covers the pin and the bottom of the joint.

[0027] The thermoplastic material of the filter component according to the invention may be a composite material containing additives to improve its stability, such as carbon or glass fibres.

[0028] Another object of the invention is the use of a filter component according to the invention in a filter device, said filter device being a vessel, the unfiltered fluid being separated from the filtered fluid by a head plate.

[0029] In a preferred embodiment of the invention, the filter components of the filter apparatus are mounted in one or more common filter headers as collector tubes.

[0030] In another preferred embodiment of the present invention, the filter component is preferably used in a system in which the filter component is attached to a pipework header (i.e., not in a closed filter vessel) and instead is immersed in a feed contained in an open vessel, and the pressure differential required to effect filtration is created by suction in such pipework header. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 shows a longitudinal section of a candle filter component according to the present invention. [Diagram 2] FIG. 2 shows a detail of the extrusion support with the filter cake, which contains particles filtered from the feed suspension, and the filter cloth. [Diagram 3] FIG. 3 shows a preferred design of a wet cake discharge filter candle component according to the present invention. [Figure 4] FIG. 4 shows a cross section of another embodiment in which the continuously extruded profile resembles a star. [Diagram 5] FIG. 5 shows a cross section of another embodiment in which the continuously extruded profile resembles a cricket bat. [Figure 6] FIG. 6 shows a cross section of another embodiment in which a long bar is attached to a body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The object of the present invention is to provide a filter component comprising a support and a filter fabric laid around the support, the support comprising a centrally located submerged channel and an outer longitudinal channel. The filter fabric may be wound around the support. During operation of the filter component, the filter fabric supports the filter cake when it is flowed from outside to inside by the suspension. The submerged channels may have a circular or non-circular cross section, for example square, hexagonal, etc. By "channels" in the context of the present invention is meant the free longitudinal spaces formed by the material of the support, with the express exclusion of cylindrical tubes, for example as in US Pat. No. 4,473,472. The simplest embodiment of the submerged channels may be a free longitudinal space of circular cross section in the middle of the profile. The outer longitudinal channels are not only perforated to some extent as in US Pat. No. 4,473,472, but are essentially completely open radially towards the outside of the filter component, as shown in Figures 2, 3, 4, 5 and 6. This feature of the flow path provides lower resistance to the flow of the fluid or respective gas during filtration and backwashing, thereby achieving a more efficient backwashing.

[0033] Preferably, the support of the filter component according to the invention is formed of a continuous profile, more preferably a continuous extruded profile, preferably comprising a thermoplastic material. Alternatively, the extruded profile may be made of another extruded material, for example metal (aluminium, steel, etc.) or glass. In principle, ceramic materials are also suitable.

[0034] "Continuous" in the context of the present invention means that the cross section of the body is the same over the entire length of the support. "Extruded" in the context of the present invention means that the support is formed continuously over its entire length, as well as the full length bar, in an extrusion process.

[0035] A continuous extrusion profile generally has the advantage that it typically does not leave dead spots, such as edges, corners, etc., where filter fluids or particles may reside for long periods of time and undergo changes that can have negative effects such as degradation, aging, bacterial growth, etc.

[0036] However, for some applications where blind spots are less of a danger, a continuous profile is also suitable, comprising a central tube forming the submerged passage and long bars attached to the central tube by known methods (such as welding, screwing, riveting, etc.) Such a body can be, for example, a cylindrical tube with longitudinal fins, as used in liquid-to-air heat exchangers.

[0037] Preferably, the outer contour of the support of the filter component according to the invention may be circular, star-shaped, cricket bat-shaped or elliptical. By "elliptical" is meant a rounded, edgeless, non-circular outer contour, the two symmetry axes showing the symmetrical relationship between the major and minor axes of the cross section of the support being between 1.1:1 and 20:1. For the purposes of the present invention, a cricket bat shape is also considered. Some suitable outer contour shapes, i.e. profile shapes, can be derived from Figure 3 (circular), Figure 4 (star-shaped) and Figure 5 (cricket bat shape).

[0038] In a preferred embodiment of the invention, the outer longitudinal channels are formed by longitudinal walls in the material of the support having rounded outer edges and are covered by a filter fabric, which during filtration rests on these rounded outer edges and is therefore essentially supported by the longitudinal walls.

[0039] Preferably, the immersed channel volume is at least 1% greater, preferably between 1% and 5% greater, than the total differential volume of all the outer longitudinal channels of the same filter component, where total differential volume is taken to mean the total volume (accessible to filtrate) in the filter fabric in the backwash position minus the volume (accessible to filtrate) of the channels covered by the filter fabric in the filtration position.

[0040] In a preferred embodiment of the present invention, the filter fabric is a substantially cylindrical filter fabric. It is preferably fixed to the filter component by fabric fastening elements, in particular one fabric fastening element at the lower end of the longitudinal flow area of ​​the candle filter component and one fabric fastening element at the upper end of the longitudinal flow area. In this embodiment of the present invention, the fabric fastening elements also seal the filter chamber against the feed chamber. The fabric fastening elements may be, for example, clamps, tension rings, or other suitable devices known to those skilled in the art.

[0041] Preferably, the filter component further comprises a connection between the support and the fixing device and a pin for optimal positioning of the filter component within the filter device.

[0042] Preferably, the filter fabric is secured above the joint, covering the pin and the bottom of the joint, as shown in FIG.

[0043] The thermoplastic material of the filter component according to the invention may be a composite material containing additives to improve its stability, such as carbon or glass fibers. Such materials, as well as methods for forming them in an appropriate manner, are known to those skilled in the art.

[0044] Another object of the invention is the use of a filter component according to the invention in a filter device, said filter device being a vessel, the unfiltered fluid being separated from the filtered fluid by a head plate.

[0045] In a preferred embodiment of the invention, the filter components of the filter apparatus are attached to one or more common filter headers, also referred to as collector tubes, such as those described in U.S. Patent No. 4,604,201 as "outlet channels."

[0046] In another preferred embodiment of the present invention, the filter component is preferably used in a system configuration in which the filter component is attached to a pipework header (i.e., not in a closed filter vessel) and instead is immersed in a feed contained in an open vessel, and the pressure differential required to effect filtration is created by suction within such pipework header.

[0047] Figure 1 shows the main parts of a candle filter component 100. The support 1 comprises an extruded profile with an integrated dip tube 2, a bottom part 3 for collecting the filtrate and redirecting the flow, a support area 4 for clamps 5 to clamp a filter fabric 6, and a coupling part 7 for fixing the filter component to a fixing device 9 via pins 8. On the fixing device 9 there is another support area 4 for clamps 5 to fasten the filter fabric. One clamp is on the bottom side of the filter component and one on the upper side of the filter component. On the upper side the filter component is provided with means for connecting the filter component to the filtrate chamber.

[0048] According to the invention, the unfiltered fluid passes through the candle filter component from the external inlet. It passes through the filter cloth, which creates a constant pressure difference from the outside to the inside. When pumped by this pressure difference, the filter cloth 6 sticks to the surface of the support 1. This happens evenly and evenly around the circumference. Particles of the unfiltered fluid that separate on the surface of the filter cloth accumulate particle bridges, which form a filter cake 11 (see FIG. 2). The clean filtered fluid passes through the filter cloth and is collected in the outer longitudinal channels 10 of the support. These channels 10 are closed at the top of the support 1, so that the filtered fluid is forced to flow downwards towards the bottom 3, where it is redirected to flow upwards through the dip tube 2 of the support 1 and exit the candle filter component at the top. Once the accumulation of the filter cake 11 is complete, the filter candle is washed and then filtration is resumed. Washing can be carried out in two different ways. It depends on whether it is desired for the process that the filter cake be discharged dry or whether it is desired that the filter cake be discharged as a slurry.

[0049] Backwashing and cake drainage is triggered by reversing the fluid flow with a pump or by introducing gas from the filtrate side. Cake drainage can be done dry by first removing all liquid from the system and allowing the filter cake to fall through the bottom valve, or in slurry form by backwashing into a filled feed chamber and then draining the slurry through the bottom valve.

[0050] Figure 3 shows a preferred design of the wet cake discharge filter candle component according to the invention. The support 1, including the outer flow paths for the filter cake, for the filtrate and the dip tube, is all made in one continuous extrusion profile. The component is therefore only completed by the top and bottom, and is preferably made of simple machined or injection molded parts, thus minimizing the material used and the time required to manufacture the component. The diameter of the dip tube is designed so that it can accommodate enough fluid to compensate for the volume change due to the movement of the filter fabric during backwashing.

[0051] FIG. 4 shows a cross section of another embodiment in which the continuously extruded profile resembles a star, allowing for greater movement of the filter fabric as it expands during application of compressed gas from the inside, improving release of the filter cake.

[0052] 5 shows a cross section of another embodiment in which the continuously extruded profile resembles a cricket bat, again allowing for greater movement of the filter fabric as it expands during application of compressed gas from the inside. This embodiment has the added advantage of allowing a larger total volume of filter cake to be accommodated for a given vessel size.

[0053] FIG. 6 shows a cross section of an alternative embodiment in which the elongated bar is attached to the body by welding (eg resistance welding) a U-shaped metal profile 13 to the central tube 12 .

Claims

1. A filter component comprising a support and a filter fabric disposed around the support, the support having a centrally located submerged channel and outer longitudinal channels.

2. The filter component of claim 1 , wherein the support is formed of a continuous profile.

3. A filter component as described in claim 2, wherein the support is formed from a continuous extrusion profile.

4. A filter component as described in claim 2 or 3, wherein the support comprises a thermoplastic material, a ceramic material, or a metal.

5. 10. The filter component of claim 1, wherein the outer contour of the support is circular, star-shaped, cricket bat-shaped, or oval.

6. 2. The filter component of claim 1, wherein a central tube defines the submerged channel, and wherein elongated rods are attached to the central tube.

7. 2. The filter component of claim 1, wherein the outer longitudinal channels are formed by longitudinal walls in the support material having rounded outer edges and covered by a filter fabric.

8. 10. The filter component of claim 1, wherein the immersed channel volume is at least 1% greater than the total differential volume of all outer longitudinal channels.

9. 2. The filter component according to claim 1, wherein the filter fabric is fixed to the filter component by fabric fastening elements, in particular by one fabric fastening element at the lower end of the filter component in the region of the outer longitudinal channels and one fabric fastening element at the upper end of the filter component in the region of the outer longitudinal channels, the fabric fastening elements sealing the filter chamber from the feed chamber.

10. 2. The filter component of claim 1, further comprising a coupling between the support and a fixing device and a pin for optimal positioning of the filter component within the filter device.

11. The filter component of claim 10 , wherein the filter fabric is secured above the joint to cover the pin and the joint.

12. 5. A filter component according to claim 4, wherein the thermoplastic material is a composite material containing additives to improve stability, such as carbon or glass fibers.

13. 10. Use of the filter component of claim 1 in a filter device, wherein the filter device is a vessel and the unfiltered fluid is separated from the filtered fluid by a head plate.

14. 10. Use of the filter component of claim 1 in a filter device, wherein the filter component is attached to one or more common filter headers as collector tubes.

15. 10. The use of the filter component of claim 1, wherein the filter component is used in a system configuration in which the filter component is attached to a tube header and immersed in a feed contained in an open container, and the pressure differential required to perform filtration is created by suction within such tube header.

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