Filter system for a fluid

Abstract

Filter system (100, 200, 300, 400, 500) for one fluid, comprising: - a filter element with a surface (106, 202) forming a first electrode, wherein the surface (106, 202) is provided with an electrostatically chargeable coating, and wherein the filter system (100, 200, 300, 400, 500) is arranged such that the coating is in contact with the fluid during operation of the filter system (100, 200, 300, 400, 500), - a second electrode (110, 204) arranged on the side of the coating facing away from the electrically conductive surface (106, 202), - a voltage source (112), wherein the voltage source (112) is connected to the first and second electrodes (110, 204) in such a way that a voltage is generated between the electrodes which electrostatically charges the coating.

Description

[0001] The invention relates to a filter system for a fluid.

[0002] In numerous technical applications, fluids—liquids or gases—contaminated with particles exist, and these particles must be removed. Examples include exhaust gases from stationary or mobile combustion engines in motor vehicles or industrial plants, or exhaust air in industrial facilities such as paint shops, or in homes such as kitchens (range hoods) or heating systems.

[0003] Filters that function according to the sieve effect are frequently used for this purpose. A fine-pored filter material is used through which the fluid must pass. Particles larger than the pores are prevented from penetrating the filter medium and are thus removed from the fluid. For example, ceramic is used for this purpose in particulate filters in motor vehicles.

[0004] The problem here is that the filter's permeability decreases after a certain time, as the trapped particles accumulate in the filter material. Either the filter then needs cleaning, or the filter material needs to be replaced.

[0005] Starting from this, the object of the invention is to provide an alternative filter system for fluids which has a long service life.

[0006] This problem is solved according to the invention by a filter system for a fluid, comprising: a filter element with a surface forming a first electrode, wherein the surface is provided with an electrostatically chargeable coating, and wherein the filter system is arranged such that the coating is in contact with the fluid during operation of the filter system; a second electrode arranged on the side of the coating facing away from the electrically conductive surface; a voltage source, wherein the voltage source is connected to the first and the second electrode in such a way that a voltage is generated between the electrodes that electrostatically charges the coating.

[0007] The invention is based on the idea of ​​providing a filter based on the principle of electrostatic attraction, departing from the known sieving effect. The filter system should include a contact surface that is electrostatically charged and in contact with the fluid. This contact surface must be made of an electrostatically chargeable material. For this purpose, a first electrode is designed as a flat surface and provided with an electrostatically chargeable coating. The second electrode should then be arranged on the opposite side of the coating, either in contact with the coating or at a distance above it.

[0008] The coating is thus positioned between the first and second electrodes. Furthermore, a voltage source is provided that generates a voltage between the first and second electrodes, causing the coating to become electrostatically charged in the electric field between the electrodes. Particles flowing past the coating in the fluid are electrostatically attracted and adhere to the coating. This removes them from the fluid, thereby cleaning it.

[0009] In an advantageous embodiment, the coating comprises a plastic, preferably a semiconductor, most preferably selenium. Semiconductors, especially selenium, are particularly suitable for electrostatic charging because they can maintain their charge state for a comparatively long time after exposure to an electric field. This allows the particles to be removed from the fluid particularly effectively.

[0010] In a further advantageous embodiment, the surface on which the coating is arranged, i.e., the first electrode, is cylindrical. In principle, any shape of base surface is possible; the essential requirement is that it be tube-like. A circular or hexagonal base surface is particularly advantageous. The coating is advantageously applied along the entire circumference, ideally even across the entire surface. It can be applied to the inside or the outside, depending on which side is in contact with the fluid. A coating on both sides is also conceivable.

[0011] A circular or hexagonal base is particularly advantageous when multiple identical filter elements are used. These can then be arranged side by side with their axes parallel to the cylindrical shell 5, allowing for a larger cross-sectional area to flow through. This can be beneficial for applications with a large volume of fluid to be filtered. Either the coating surface is located on the inside of each filter element, and the elements are packed closely together (this is particularly advantageous with a hexagonal base), or the coating surface is located on the outside of each filter element, and the elements are spaced apart.

[0012] Depending on the geometry of the filter system, especially with a large surface area, it can be difficult to maintain the entire surface in a state of electrostatic charge 20, as the coating discharges again due to the fluid flow. The second electrode must therefore either be kept permanently near the coating or regularly brought close to it to recharge it. For this purpose, the second electrode is advantageously arranged to be movable relative to the coating and preferably cyclically sweeps over the coating. The geometry and movement should be coordinated so that the entire surface of the coating is swept over. Both the first electrode with the coating and the second electrode can move within the filter system. One of the two electrodes can be fixed at any given time.

[0013] If the first electrode is cylindrical, as described above, a particularly advantageous design results from the second electrode being linear and arranged parallel to the axis of the cylinder, while the first electrode is designed to rotate around the axis of the cylinder. Thus, the first electrode rotates around its own axis, and the second electrode is located on the inside if the coating is internal, and on the outside if the coating is external. It is designed as a simple wire and arranged parallel to the axis of the cylinder, so that the cylindrical surface rotates along the second electrode. This design is particularly advantageous when the cylinder has a circular base.

[0014] In cases where no movement of the second electrode relative to the coating is intended, an alternative advantageous embodiment allows the second electrode to be arranged on the coating in the form of a braid. The term "braid" here means that the electrode is integrated onto the coating in the form of a network of wires arranged side by side in a grid-like manner or interwoven with one another. The braid should extend over the entire effective area, i.e., the entire surface of the coating, leaving a sufficiently large area uncovered to remain in contact with the fluid.

[0015] The filter system is preferably arranged in a fluid channel through which the fluid to be filtered flows. Either the fluid can flow through the fluid channel, or the fluid channel can be agitated by the stationary fluid. In the first case, the filter system advantageously includes a conveying device for the fluid, which is arranged in the fluid channel.

[0016] High voltages are advantageous for the electrostatic charging of the coating. Therefore, the voltage source advantageously includes an ignition coil. This makes it possible to generate high voltages between the two electrodes while still using only comparatively low voltages on the primary side. This reduces the energy consumption of the filter system.

[0017] In a further advantageous embodiment, the filter system comprises a control system designed to intermittently reverse the voltage polarity. By reversing the voltage polarity, the accumulated particles can be easily removed from the coating. This can be done as needed or at predetermined intervals.

[0018] Alternatively or additionally, the filter system includes a mechanical cleaning device assigned to the respective surface. This can, for example, use brushes or scrapers to remove accumulated particles from the coating, again as needed or at predetermined intervals.

[0019] The advantages achieved with the invention lie particularly in the fact that, by using the principle of electrostatic attraction in a filter system, particles can be filtered out of a fluid stream especially easily and efficiently. The removal of the separated particles is simple, and the system can also be easily adapted to a wide variety of fluid flow rates and fluid types, making it suitable for use in a multitude of specific applications.

[0020] Exemplary embodiments of the invention are explained in more detail with reference to the drawings. These show: Fig. 1. A schematic diagram of a filter system; Fig. 2 a schematic representation of a more detailed embodiment of the filter system for use as an exhaust gas filter in a motor vehicle; Fig. 3 a schematic representation of an alternative embodiment with a hexagon as the base of the cylindrical coated surface and a second electrode integrated on the coating; Fig. 4 a schematic representation of a close packing of several cylinders with hexagonal bases to form a filter system; Fig. 5 a schematic representation of a dense packing of several cylinders with circular bases to form a filter system; and Fig. 6 a schematic representation of a spaced arrangement of several cylinders with circular bases to form a filter system.

[0021] Identical parts are marked with the same reference symbols in all drawings.

[0022] The Fig. Figure 1 shows a schematic diagram of a filter system 100, which illustrates the basic function and possible designs for all conceivable embodiments. The filter system functions based on electrostatic attraction. An electrostatically chargeable material is charged accordingly and thus attracts particles from a fluid flowing past it, thereby filtering the fluid. The schematic diagram of the filter system 100 shows a cylindrical surface 106 with an electrostatic surface 202, which, depending on the application and the fluid flow, can be located on the outside or inside of the cylinder. The electrostatic charging is achieved via a corona wire connected to a voltage source 112, thus forming an electrode 110. The wire can be spaced away from the surface 202 or arranged on or within its surface. A wire mesh can also be provided, or several, e.g.,Parallel wires are present. The wire can also be ring-shaped or spiral-shaped. The essential point is that it ensures a suitable electrostatic charge on surface 202.

[0023] The Fig. Figure 2 shows a more specifically designed filter system 100, which is suitable for exhaust gas purification in a motor vehicle (not shown in detail). It shows a fluid channel 102 through which the exhaust gas of the motor vehicle is routed. The fluid channel 102 has an inspection hatch 104. A cylindrical surface 106, i.e., in the form of a roller, is arranged in the fluid channel 102. This surface is made of a metal, e.g., aluminum, and is provided on its outer surface with a semiconductor coating (not shown in detail).

[0024] The roller shown is rotatably mounted on its axis 108 and can be rotated by a drive mechanism not shown in detail. The axis 108 is aligned in the direction of the exhaust gas flow.

[0025] To filter particles from the exhaust gas, the coating is electrostatically charged. For this purpose, the surface 106 itself forms a first electrode. The second electrode 110 is formed by a wire spaced apart on the outside of the coating. The wire runs parallel to the axis 108 and extends along the entire height of the cylinder. A voltage source 112, comprising an ignition coil, is also provided to generate a sufficiently high voltage across the coating between the wire and surface 106 to electrostatically charge the coating. Due to the asymmetrical arrangement of the wire, the coating is initially electrostatically charged only in the area of ​​the wire.

[0026] Through a uniform rotation of the cylinder, the wire sweeps across its entire circumference, electrostatically charging the entire coating and filtering particles from the exhaust stream. An advantageous side effect is that the electrostatic charge is not maintained for a full rotation, so that before the end of a complete revolution, the filtered particles detach from the coating and fall to the bottom. This process cleans the Filter System 100 automatically.

[0027] In a specific test, the filter performance of filter system 100 was tested. For this purpose, a total of four [unclear] were used. Fig. Two filter elements in the form of cylinders are shown, arranged in the exhaust system of an older diesel vehicle. Each cylinder had a diameter of approximately 4 cm and rotated continuously at about one revolution per second. The wire serving as the second electrode (110) was approximately 0.5 mm thick and positioned 4 mm from the coating. The coating consisted of selenium. A 6 V battery was used as the primary voltage source upstream of the ignition coil, resulting in a secondary voltage of approximately 1000 V between the electrodes.

[0028] The measurements were taken with and without the described filter system using a standard, approved exhaust gas analyzer, the kind used in regular emissions tests. The K-value, a measure of exhaust opacity caused by soot particles, and N2 (nitrogen) were measured. At 770 engine revolutions per minute, the K-value was reduced from 5.4 to 5.0 (-7.4%) with the filter system. N2 was reduced from 0.14 to 0.12 (-14.3%). At 2090 engine revolutions per minute, the K-value was reduced from 22 to 16 (-27.3%) with the filter system. N2 was reduced from 0.57 to 0.40 (-29.8%). At 2500 revolutions per minute of the vehicle's engine, the K-value was reduced from 35 to 22 (-37.1%) through the use of the filter system. N2 was reduced from 1.00 to 0.55 (-45%).

[0029] Despite a relatively simple design, significant filtration rates were achieved.

[0030] In an alternative embodiment, not shown in the illustration, the Fig. The cylinder shown may also be coated on the inside.

[0031] Accordingly, the wire is also arranged as a second electrode inside the hollow cylinder - again parallel to the axis - and the fluid flows through the inside of the cylinder.

[0032] Fig. Figure 3 shows an alternative embodiment of the filter system 200. The base of the cylinder is a hexagon, so that the coated surface 202 represents a hexagonal cylinder. The coating is arranged on the inner side of the cylinder.

[0033] In the exemplary embodiment of the Fig. Figure 3 shows the second electrode 204 as a mesh of wires (not shown) distributed across the entire surface of the coating, for example in a net-like or grid-like arrangement. In this way, the entire coating can be continuously electrostatically charged without requiring any movement of an electrode. Of course, the design of the second electrode as a mesh placed directly on the coating is also possible with other surface shapes.

[0034] The in Fig. The embodiment shown in Figure 3, with a hexagonal base and an internal second electrode, also allows for a dense packing of several cylinders in a filter system 300, as shown schematically in Figure 3. Fig. Figure 4 illustrates this. The cylinders are arranged parallel to the axis, and the fluid flow direction is also parallel to the axis, so that the fluid flows through the cylinders longitudinally. Alternatively, such an axially parallel arrangement is also possible with cylinders with a circular base, as in the filter system 400 of the Fig. 5 shows. However, unlike the hexagonal version, gaps remain here.

[0035] Alternatively, it is also possible to arrange several cylinders as filter elements spaced apart from each other, as in the filter system 500 of the Fig. Figure 6 shows this. This is particularly advantageous for externally coated cylinders. The cylinders in the Filter System 500 can be arranged as desired and subjected to flow from any direction, making the Filter System 500 particularly flexible and adaptable to a wide variety of fluid types and quantities, as well as diverse applications.

[0036] The described filter system 100, 200, 300, 400, 500 can be used for a wide variety of applications. In addition to the Fig. In addition to the application described in section 2 for filtering exhaust gases from motor vehicle combustion engines, the filter system 100, 200, 300, 400, 500 can also be used, for example, in heating stoves, especially those that burn wood. Here, the exhaust gases and particulate matter produced during wood combustion can be cleaned using a filter system 100, 200, 300, 400, 500 in the flue pipe. For this purpose, the filter system 100, 200, 300, 400, 500 is integrated into the existing flue pipe on the exterior of the building.

[0037] Another application is water purification through the integration of a 100, 200, 300, 400, or 500 mm filter system into a home's water circulation system. This allows for the filtering of particles such as microplastics or pharmaceutical residues from the water. Furthermore, air purification is conceivable in households by installing a 100, 200, 300, 400, or 500 mm filter system in a freestanding unit or one integrated into a ventilation system, and then drawing or blowing air through the filter system.

[0038] Suitable freestanding or ventilation-integrated filter systems (100, 200, 300, 400, 500) can also be used outdoors, provided they have a correspondingly larger filter area. These filter systems can be used to remove particles from busy streets in cities. They can also be mounted on existing poles such as traffic lights or streetlights. Furthermore, these filter systems can be integrated into tunnel ventilation systems to purify the air in tunnels as well.

[0039] Furthermore, the use of filter systems 100, 200, 300, 400, and 500 according to the above principle is possible on all types of moving vehicles, railways, ships, or aircraft. In this process, the surrounding medium (air or water) is conveyed through the filter by the movement of the vehicle or vehicle. The filter system 100, 200, 300, 400, and 500 is designed so that the direction of movement is parallel to the flow direction. Reference symbol list 100 filter system 102 Fluid channel 104 Inspection hatch 106 area 108 Axis 110 second electrode 112 Voltage source 200 filter system 202 area 204 second electrode 300 filter system 400 filter system 500 filter system

Claims

[1] Filter system (100, 200, 300, 400, 500) for a fluid, comprising: - a filter element with a surface (106, 202) forming a first electrode, wherein the surface (106, 202) is provided with an electrostatically chargeable coating, and wherein the filter system (100, 200, 300, 400, 500) is arranged such that the coating is in contact with the fluid during operation of the filter system (100, 200, 300, 400, 500), - a second electrode (110, 204) arranged on the side of the coating facing away from the electrically conductive surface (106, 202), - a voltage source (112), wherein the voltage source (112) is connected to the first and second electrodes (110, 204) in such a way that a voltage is generated between the electrodes which electrostatically charges the coating. [2] Filter system (100, 200, 300, 400, 500) according to the preceding claim, wherein the coating comprises a plastic, preferably a semiconductor, particularly preferably selenium. [3] Filter system (100, 200, 300, 400, 500) according to one of the preceding claims, wherein the surface is cylindrical and in particular has a circular or hexagonal base. [4] Filter system (100, 200, 300, 400, 500) according to the preceding claim, in which a plurality of similar filter elements are provided and the respective surface (106, 202) is arranged on the inside of the filter elements and the filter elements are packed tightly, or in which the respective surface (106, 202) is arranged on the outside of the filter elements and the filter elements are spaced apart from each other. [5] Filter system (100, 200, 300, 400, 500) according to one of the preceding claims, wherein the second electrode (110, 204) is movably arranged relative to the coating and preferably cyclically sweeps over the coating. [6] Filter system (100, 200, 300, 400, 500) according to claims 3 and 5, wherein the second electrode (110, 204) is linear and arranged parallel to the axis of the cylinder shell, and the first electrode is designed to rotate about the axis of the cylinder shell. [7] Filter system (100, 200, 300, 400, 500) according to one of the preceding claims, wherein the second electrode (110, 204) is arranged in the form of a mesh on the coating. [8] Filter system (100, 200, 300, 400, 500) according to one of the preceding claims, arranged in a fluid channel, preferably comprising a conveying device for the fluid which is arranged in the fluid channel. [9] Filter system (100, 200, 300, 400, 500) according to any of the preceding claims, wherein the voltage source (112) comprises an ignition coil. [10] Filter system (100, 200, 300, 400, 500) according to any of the preceding claims, comprising a control system configured to intermittently reverse the polarity of the voltage. [11] Filter system (100, 200, 300, 400, 500) according to any of the preceding claims, comprising a mechanical cleaning device assigned to the respective area.

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