Candle filter device

Abstract

The present invention relates to a candle filter apparatus, including one or more candle filter components, primarily for filtering solids from liquids, and a process for operating the same.

Description

[Technical field]

[0001] The present invention relates to a candle filter apparatus, including one or more candle filter components, primarily for filtering solids from liquids, and a process for operating the same.

[0002] The essential parts of the filter apparatus are a pressure vessel having a head plate separating a feed chamber containing the unfiltered fluid suspension from a filtration chamber containing the filtered fluid, and a candle filter component attached to the head plate. [Background technology]

[0003] 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.

[0004] The support, which serves as the main component of the candle filter component and supports the filter cloth, is already known from German patent specification 3249756, C2. In this prior art, the support is a perforated cylinder, which is mounted vertically inside the feed chamber of the pressure vessel. The filter cloth has the shape of a hose, which is wound around the outside of the cylinder and fixed 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 head plate which separates the feed chamber from a chamber receiving the filtrate, called the filtration chamber, and thus has an open connection to the filtration chamber. This connection allows the filtered fluid to flow from the candle interior into the filtration chamber after passing through the filter cake and the filter cloth. 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 cloth in the reverse / opposite direction. The purpose of this flow reversal process is to remove the filter cake from the filter fabric and to remove particles from inside the pores of the porous filter fabric, which can then lead to clogging of the fabric, thereby preventing flow over an extended period of time. Some process designs support backwashing by using pressurized gas to drive an increased amount of the filtered fluid or fluid-gas mixture through the filter fabric.

[0005] An important design parameter of such filtration systems is the filter area that can be accommodated in the filtration system. Reducing the diameter of the filter candle and increasing the length of the filter candle both increase the filter area that can be accommodated in a filtration vessel of a given diameter, thereby reducing the cost per filter area and, therefore, the cost per flow rate of the fluid being filtered. Filter candle lengths of 1 m to 2.5 m and filter candle diameters of 25 mm to 120 mm are state of the art.

[0006] One of the most important performance parameters is backwash efficiency, which means the ability to completely remove the filter cake from the filter fabric and remove particles trapped inside the pores of the filter fabric. Backwash efficiency increases in proportion to the fluid flow across the entire surface of the filter candle during backwashing.

[0007] 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, where the filtered fluid enters the filter candle, to the bottom of the filter candle. Tests have demonstrated that with a filter candle with a diameter of 80 mm, a reasonable fluid flow occurs only in the top 300 mm of the filter candle when using an aqueous solution to clean the filter candle. The remaining length of the filter candle does not receive a reasonably high filtrate flow, sufficient to permanently clean the filter fabric. This results in the need for frequent replacement of the filter fabric, which leads to high operational costs for the filter fabric and the time required to replace the filter fabric.

[0008] A means of improving this insufficient backwashing is described in U.S. Pat. No. 4,604,201. It involves the introduction of a dip tube inside the filter candle component, which reaches an open bottom and is thereby connected to the chamber between the dip tube and the filter fabric. 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 in the filter header is inverted by applying compressed air or other gas to the filter header. This compressed air or other gas forces the fluid down the dip tube, up through the free space in the candle surrounding the dip tube, and through the filter fabric from inside to outside. When the fluid level reaches the lowest point in 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 compressed air or compressed gas introduced at the bottom of the filter candle, results in a better backwashing compared to the prior art.

[0009] The filter device according to US Pat. No. 4,604,201 can accommodate large filter areas. For effective backwashing, a high flow rate through each filter area segment is required. To achieve this, it is necessary to divide the entire filter area into small segments that are backwashed at one time. This results in a technically feasible small flow rate of gas to pump the filtrate through the filter fabric and a technically feasible small nozzle to eject the backwashed fluid from the vessel, resulting in a high pressure resistance that restricts the flow. Typically, up to 12 candle filter components are clustered in such a segment. [Prior art documents] [Patent documents]

[0010] [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]

[0011] The problem solved by the present invention is that in filtration systems with filter candle components without a dip tube structure, backwashing of most of the filter surface is insufficient, and in filtration systems with a dip tube structure, implementation and operation are complicated. This is solved by introducing a method for fully backwashing filter candle components with a dip tube without dividing the filter area into increments. [Means for solving the problem]

[0012] The object of the present invention is to provide a filter device comprising a pressure vessel having a feed chamber and a filtration chamber separated by a head plate, a) one or more filter components are mounted vertically to the head plate; b) The supply port reaches the supply chamber; The present invention provides a filter device.

[0013] The filter device a) at least one ventilation opening; b) at least one gas supply nozzle and at least one exhaust nozzle are attached to the supply chamber; The filter component has a submerged passage therein.

[0014] Preferably, said vent has a vertical height greater than the lowest exit level of said exhaust nozzle. The distance between the vent and the lowest exit level of the exhaust nozzle is referred to as "distance h".

[0015] Even more preferably, the distance h between said vent and the lowest outlet level of said discharge nozzle is designed to ensure a buffer gas volume equal to the internal volume of the submerged passages of all installed filter components during backwashing.

[0016] In a preferred embodiment of the invention, the filter component comprises a support and a filter fabric laid around the support, the support having a centrally located submerged channel and outer longitudinal channels.

[0017] Preferably, the support for the filter component in the filter device according to the invention is formed from a continuous profile, preferably a continuous extruded profile, and more preferably comprises a thermoplastic material.

[0018] Preferably, the outer contour of the support of the filter component in the filter device according to the invention may be circular, star-shaped, cricket bat-shaped or elliptical.

[0019] However, in some applications an embodiment in which a central tube forms the submerged channel and the elongated rods are mounted on said central tube may be appropriate.

[0020] In a preferred embodiment of the invention, the outer longitudinal channels of the filter component are formed by longitudinal walls in the material of the support having rounded outer edges and are covered by the filter fabric.

[0021] Preferably, the immersed channel volume of the filter component is at least 1% greater than the total differential volume of all the outer longitudinal channels of the filter component, preferably 1% to 5% greater.

[0022] In a preferred embodiment of the invention, the filter fabric is fixed to the filter component by fabric fastening elements, in particular one fabric fastening element at the lower end of the longitudinal flow region and one fabric fastening element at the upper end of the longitudinal flow region of the candle filter component, which in this embodiment of the invention seal the filtration chamber from the dispensing chamber.

[0023] 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.

[0024] Preferably, the filter fabric is fixed above the joint of the filter component and covers the pin and the bottom of the joint.

[0025] The thermoplastic material of the filter component according to the invention may be a composite material containing stability enhancing additives such as carbon or glass fibres.

[0026] Another object of the invention is to provide a method for backwashing a filter device as described above, comprising the steps of: a) depressurizing the filter device; b) Discharge all possible suspension from the feed chamber by means of a discharge nozzle; c) pressurizing the filter device with pressurized gas from a gas supply nozzle; d) Filter components i) rapidly releasing the pressure in the feed chamber, thereby inducing a gas impulse of compressed gas from the filtration chamber to rapidly and rapidly pump the filtrate downward in the submerged flow channel; ii) expanding the filter fabric until it reaches its maximum cross-section, thereby removing the filter cake from said filter fabric; This backwashes the e) optionally allowing the filter cake slurry to settle; f) discharging the filter cake slurry from the bottom of the feed chamber through another discharge nozzle; A backwash method is provided. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 shows a filter device according to the present invention. [Diagram 2] FIG. 2 shows a detail of the filter device according to the invention. [Diagram 3] FIG. 3 shows a longitudinal section of a candle filter component according to the present invention. [Figure 4] FIG. 4 shows a filter cake containing particles filtered from the feed suspension, and a detail of the extrusion support equipped with a filter cloth. [Diagram 5] FIG. 5 shows a preferred design of a filter candle component for wet cake discharge according to the present invention. [Figure 6] FIG. 6 shows a cross section of another embodiment in which the continuously extruded profile resembles a star. [Figure 7] FIG. 7 shows a cross section of another embodiment in which the continuously extruded profile resembles a cricket bat. [Figure 8] FIG. 8 shows a cross section of another embodiment of a filter candle in which an elongated rod is attached to the body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The object of the present invention is to provide a filter device comprising a pressure vessel having a feed chamber and a filtration chamber separated by a head plate, a) one or more filter components are mounted vertically to the head plate; b) The supply port reaches the supply chamber; The present invention provides a filter device.

[0029] The filter device c) at least one ventilation opening; d) at least one gas supply nozzle and at least one exhaust nozzle are attached to the supply chamber; The filter component is provided with a submerged channel inside. The feed inlet may consist of a standpipe with a standpipe outlet, as shown in FIG. 2. Alternatively, the feed inlet may be one or more nozzles attached to the side wall of the feed chamber. The vent must be attached to the feed chamber at the highest position technically possible. The vent may be A) the same as the feed inlet, e.g. a standpipe outlet (alternative A), b) a separate nozzle in the side wall of the feed chamber (alternative B), or c) a nozzle in a head plate connected to the outside of the filter device (not the filtration chamber) (alternative C). Alternative A with a standpipe and standpipe outlet is shown in FIG. 2.

[0030] Preferably, the vent has a vertical height greater than the lowest exit level of the exhaust nozzle. The distance between the vent and the lowest exit level of the exhaust nozzle is referred to as "distance h".

[0031] Even more preferably, the distance h between the vent and the lowest outlet level of the discharge nozzle is designed to ensure a buffer gas volume equal to the internal volume of the submerged passages of all installed filter components during backwashing.

[0032] The filter components installed in the filter device may be of various types already generally known in the prior art. They may be, for example, of the type disclosed in German Patent Specification No. 3249756, C2, US Pat. No. 4,473,472 or US Pat. No. 4,968,424, each of which is incorporated herein by reference. However, in a preferred embodiment of the invention, the filter component comprises a support and a filter fabric laid around the support, the support comprising a centrally located submerged channel and outer longitudinal channels. 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 the outside to the 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 longitudinal free spaces formed by the material of the support, but explicitly excluding cylindrical tubes, for example as in US Pat. No. 4,473,472. The simplest embodiment of the submerged channels may be a longitudinal free space of circular cross section in the center of the profile. The outer longitudinal channels are not only perforated to some extent as in U.S. Pat. No. 4,473,472, but are essentially completely open radially towards the outside of the filter component, as shown in Figures 3, 4, 5, 6, 7 and 8. This feature of the channels provides lower resistance to the flow of liquid or respectively gas during filtration and backwashing, thereby resulting in more efficient backwashing.

[0033] Preferably, the support for the filter components in the filter device according to the invention is formed of a continuous profile, preferably a continuous extruded profile, more preferably comprising a thermoplastic material. Alternatively, the extruded profile may be made of another extruded material, for example metal (such as aluminum) 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 in the filter device 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 symmetrical axes of which, showing the symmetrical relationship between the major and minor axes of the cross section of the support, are 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 5 (circular), Figure 6 (star-shaped) and Figure 7 (cricket bat shape).

[0038] In a preferred embodiment of the invention, the outer longitudinal channels of the filter component are formed by longitudinal walls in a support material 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 of the filter component is at least 1% greater, preferably 1% to 5% greater, than the total differential volume of all the outer longitudinal channels of the filter component, where total differential volume means 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 by one fabric fastening element at the lower end of the longitudinal flow area and one fabric fastening element at the upper end of the longitudinal flow area of ​​the candle filter component. In this embodiment of the present invention, the fabric fastening elements seal the filtration chamber to 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 stability enhancing additives such as carbon or glass fibers. Such materials, as well as methods for molding them in an appropriate manner, are known to those skilled in the art.

[0044] Another object of the invention is to provide a method for backwashing a filter device as described above, comprising the steps of: a) depressurizing the filter device; b) Discharge all possible suspension from the feed chamber by means of a discharge nozzle; c) pressurizing the filter device with pressurized gas from a gas supply nozzle; d) Filter components i) rapidly releasing the pressure in the feed chamber, thereby inducing a gas impulse of compressed gas from the filtration chamber to rapidly and rapidly pump the filtrate downward in the submerged flow channel; ii) expanding the filter fabric until it reaches its maximum cross-section, thereby removing the filter cake from the filter fabric; This backwashes the e) optionally allowing the filter cake slurry to settle; f) discharging the filter cake slurry from the bottom of the feed chamber through another discharge nozzle; A backwash method is provided.

[0045] If the filter cake slurry has settled, only a portion of the contents of the feed chamber can be drained, or if the filter cake slurry has not settled, the entire contents of the feed chamber can be drained.

[0046] FIG. 1 shows a filtration vessel 100 having several filter candles 4 according to the invention mounted on a head plate 3 separating a feed chamber 1 from a filtration chamber 2 .

[0047] The filter candles 4 are connected to the filtration chamber through holes 5 in the head plate, as shown in FIG.

[0048] The filtration vessel 100 further comprises a feed nozzle 6 connected to a standpipe 7 , a gas feed nozzle 8 , a discharge nozzle 9 , a filtrate nozzle 10 , a discharge nozzle 11 and also an outlet 12 .

[0049] Filtration is performed by introducing unfiltered fluid containing particles into the feed chamber 1 through the feed nozzle 6 and forming a suspension. The particles remain on the outer surface of the filter candles 4 and the filtered fluid flows through the filter candles 4 into the filtration chamber 2 and then exits the filtration vessel through the filtrate nozzle 10.

[0050] To discharge the solids, usually in the form of a slurry, the feed chamber 1 remains filled and is depressurized through the outlet 12 after the end of the filtration cycle, indicated by a defined thickness of the filter cake or by reaching a certain pressure difference. The discharge nozzle 9 opens and the drainage in the device takes place. The level of fluid in the filter candles 4 automatically reaches the same height as the level in the feed chamber 1 and is equal to the level of the lowest outlet of the discharge nozzle 9. The filter candles 4 in this step are filled with the filtrate inside, while the feed chamber 1 is filled with unfiltered fluid. The volume in the feed chamber 1, defined by the level of the lowest outlet of the discharge nozzle 9 and (according to alternative A) the outlet 12 must receive the filtrate volume from the filter candles 4 after backwashing, determines the distance h between the level of the lowest outlet of the nozzle 9 and the outlet 12 (see FIG. 2). By designing this volume large enough to receive the entire amount of backwashing fluid, it is ensured that nowhere in the system is there a high resistance to the flow of the backwashing fluid, even if the entire filter area is backwashed at once.

[0051] In the next step, pressurized gas is supplied via the gas supply nozzle 8. The vessel 100 is first pressurized inside the supply chamber 1, and then via the filter candles 4 inside the filtration chamber 2. This means that finally all chambers of the vessel 100 operate with substantially the same gas pressure. In the next step, the valve of the outlet 12 is opened as quickly as technically possible, preferably in less than one second, whereby the pressure in the supply chamber 1 is rapidly reduced and a gas impulse is applied with the help of compressed gas in the filtration chamber 2, which rapidly and intensively pumps the filtrate downwards in the dip tube. Furthermore, it pumps the filtrate between the dip tube and the filter fabric upwards along the outer flow path of the support structure, making it flow in a countercurrent direction from inside to outside through the filter fabric.

[0052] This occurs over the entire filter area in a very short time (<1 second) and is ensured by the high volume of pressurized gas provided in the filtration chamber 2 and the gas volume in the supply chamber 1 which is sufficient to backwash all the fluid.

[0053] As a result, the filter fabric expands until it reaches a complete circular cross section that is larger than the cross section of the diameter of each of the supports (including the elongated rods). As the filtrate flows through the fabric from the inside to the outside in the opposite direction to the filtration flow, it removes the filter cake from the fabric. At the same time, it also removes the particles trapped inside the pores of the fabric.

[0054] The filter cake is resuspended in the unfiltered fluid chamber and, after settling, accumulates as a slurry at the bottom of the filter vessel 100 from where it is discharged through the discharge nozzle 11 .

[0055] The essential parts of the candle filter 4 are shown in Fig. 3. The support 13 comprises an extruded profile with an integrated dip tube 14, a bottom part 15 for collecting the filtrate and redirecting the flow, a support area 16 for clamps 17 to clamp the filter fabric 18 and a connection part 19 for fixing the filter component to a fixing device 21 via pins 20. The fixing device 21 has another support area 16 for clamps 17 to fasten the filter fabric. One clamp is on the bottom side and one clamp is on the upper side of the filter fabric. On the upper side, the filter component 4 is provided with means (not shown) for connecting the filter component 4 to the filtration chamber 2.

[0056] According to the invention, the unfiltered fluid passes through the candle filter component from outside to inside. It passes through the filter cloth, which creates a constant pressure difference from outside to inside. Driven by this pressure difference, the filter cloth 18 sticks onto the surface of the support 13 (see FIG. 4). This happens very evenly around the circumference. Particles of the unfiltered fluid that separate on the surface of the filter cloth 18 accumulate particle bridges, which form a filter cake 23. The clean filtered fluid passes through the filter cloth 18 and is collected in the outer longitudinal channels 22 of the support 13. These channels 22 are closed at the top of the support, so that the filtered fluid flows downwards towards the bottom 15, where it is redirected to flow upwards through the dip tube 14 of the support 13 and out of the candle filter component 4 at the top. Once the accumulation of the filter cake 23 is complete, the filter candle 4 is washed and then filtration is resumed. Washing can be carried out in two different ways. It depends on whether it is desired to discharge the filter cake 23 dry or whether it is desired to discharge the filter cake as a slurry.

[0057] Backwashing and cake discharge is triggered by reversing the fluid flow by pumps or by introducing gas from the filtrate side. Cake discharge 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 1 and then discharging the slurry through the bottom valve.

[0058] Figure 5 shows a preferred design of the filter candle component 4 for wet cake discharge according to the invention. The support 13 for the filter cake, including the outer channels for the filtrate and the dip tube are all made in one continuous extrusion profile. The component therefore only needs to be 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 channels is designed so that it can accommodate enough fluid to compensate for the volume changes caused by the movement of the filter fabric during backwashing.

[0059] FIG. 6 shows a cross-section of another embodiment in which the continuously extruded profile resembles a star, which allows for greater movement of the filter fabric 18 as it expands during application of compressed gas from the inside, improving release of the filter cake.

[0060] 7 shows a cross section of another embodiment in which the continuously extruded profile 13 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.

[0061] In FIG. 8, the elongated bar is attached to the body by welding (eg, resistance welding) a U-shaped metal profile 26 onto a central tube 25 .

Claims

1. 1. A filter apparatus comprising a pressure vessel having a feed chamber and a filtration chamber separated by a head plate, a) one or more filter components are mounted vertically to said head plate; b) the supply port reaches the supply chamber; c) at least one vent attached to said dispensing chamber; d) at least one gas supply nozzle and at least one exhaust nozzle are attached to the supply chamber; The filter device is characterized in that the filter component has an immersion flow path therein.

2. 2. The filter device of claim 1, wherein the vent has a vertical height greater than a lowest outlet level of the discharge nozzle.

3. 2. The filter device of claim 1, wherein the distance h between the vent and the lowest outlet level of the discharge nozzle is designed to ensure a buffer gas volume equal to the internal volume of the immersion passages of all installed filter components during backwashing.

4. Each of the filter components includes a support and a filter cloth laid around the support, 10. The filter device of claim 1, wherein the support includes a centrally located submerged channel and outer longitudinal channels.

5. 5. A filter device according to claim 4, wherein the support for the filter component is formed from a continuous profile, preferably a continuous extruded profile, and more preferably comprises a thermoplastic material.

6. 5. The filter device of claim 4, wherein the outer contour of the support of the filter component is circular, star-shaped, cricket bat-shaped, or oval.

7. 5. The filter device of claim 4, wherein a central tube defines a submerged channel, and the elongated rod is mounted on said central tube.

8. 5. The filter device of claim 4, wherein the outer longitudinal channels of the filter component are formed by longitudinal walls in the support material having rounded outer edges and covered by the filter fabric.

9. 5. The filter device of claim 4, wherein the immersed flow channel volume of the filter component is at least 1% greater than the total differential volume of all outer longitudinal channels of the filter component.

10. the filter fabric is fixed to the filter component by fabric fastening elements, in particular one fabric fastening element at the lower end of the longitudinal flow region of the candle filter component and one fabric fastening element at the upper end of the longitudinal flow region of the candle filter component, 5. The filter device of claim 4, wherein the fabric securing element seals the filtration chamber from the dispensing chamber.

11. 5. The filter device of claim 4, wherein the filter component further comprises a coupling between the support and a fixing device and a pin for optimal positioning of the filter component within the filter device.

12. The filter device according to claim 11, wherein the filter cloth is fixed above the joint of the filter component and covers the pin and the joint.

13. 6. The filter device of claim 5, wherein the thermoplastic material of the filter component is a composite material containing a stability enhancing additive such as carbon fiber or glass fiber.

14. A method for backwashing a filter device according to any one of claims 4 to 13, comprising the steps of: a) depressurizing the filter device; b) discharging all possible suspension from the supply chamber by means of a discharge nozzle; c) pressurizing the filter device with pressurized gas from a gas supply nozzle; d) Filter components i) rapidly releasing the pressure in the supply chamber, thereby inducing a gas impulse of compressed gas from the filtration chamber to rapidly and intensely pump the filtrate downward in the submerged channel; ii) expanding the filter fabric until it reaches its maximum cross section, thereby removing the filter cake from said filter fabric; This backwashes the e) discharging the filter cake slurry from the bottom of the feed chamber through another discharge nozzle; Backwash method.

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