Patent Application
20240266808
The invention relates to a device and to a method, and to the use thereof, for the ionization of gaseous media.
In industrial processes for producing a wide variety of products, the electrostatic charge of surfaces and therefore often the undesired adhesion of dust particles to the given workpieces constitutes a general problem. In order to remove these charges, or even avoid them in the first place, both systems without and with air support are known. For the latter, inter alia the following concepts of very different ionisers are mentioned in the prior art.
DE 10 2005 056 595 A1 discloses an ionizer with a hollow housing which, among other things, accommodates a high-voltage unit and a control unit. A plurality of electrode units in the form of needle electrodes and an air outlet for blowing an air flow around the needle electrodes, are also arranged in a row along the longitudinal direction of the housing. A part of the hollow housing consists of plastic in the longitudinal direction and is formed in a channel of an air passage such that a portion of the inner wall of the plastic housing serves as a wall of this channel. The air passage is in connection with the air outlet.
KR 10 0 2008 035 228A describes a rod-shaped ionizer. This ionizer has a rod, discharging electrodes, grounding electrodes, high voltage generation units and controls, and nozzles. The nozzles are arranged parallel to the rod in order to eject air at a predetermined pressure at a defined ejection angle in the direction of an object to be discharged. The nozzles can be electrically charged by the discharging electrode. The nozzles and electrodes are thus used such that each nozzle has its own control and blows out the air ionized by the electrode in the nozzle in order to enable stabilization of the ion equilibrium.
WO 2006 0167 38 A1 describes an arrangement for eliminating static electricity. For this purpose, pulsed AC high voltage is used which has a rectangular pulse-type voltage curve. The disclosed electrostatic eliminator comprises a discharge electrode that generates a corona discharge, a grounding electrode, a high-voltage unit that generates an AC pulse high voltage, and a controller which controls the frequency and duty factor of the AC pulse high voltage. Each electrode is integrated into one nozzle which blows the ions out of the nozzle by compressed air. The frequency range of the applied high voltage is limited from 1 Hz to up to 10 KHz. The set duty factor is set to a range of 40% to 60%. The described electrostatic eliminator can adapt the magnitude of the discharge effect via the free control of a frequency and duty factor of the applied voltage.
DE 103 20 805 A1 discloses a device for processing cylindrical substrates having at least one electrically conductive core such as wires, cables or the like, having a process space which has an inlet opening and an outlet opening for the substrate, which is moved in particular continuously relative to the device, wherein by applying a voltage to at least one electrode which is associated with the process space and is fixedly arranged on the device, and a counter electrode in the process space, a plasma can be ignited, and wherein the applied voltage is an AC voltage, characterized in that the at least one electrically conductive wire itself forms the counter electrode, in that a dielectric barrier is formed between the electrode and the at least one electrically conductive wire, which barrier is formed by the substrate itself, and in that the ignitable plasma is an atmospheric pressure low-temperature plasma.
DE 10 2014 117 746 A1 describes a compressed air preparation chamber for improving the flow properties of compressed air or compressed gas mixtures in a painting process, comprising a housing for forming a cavity, at least one air inlet opening and at least one air outlet opening, wherein the air inlet opening and the air outlet opening are arranged in such a way that the compressed air or the compressed gas mixture can flow through the cavity, preferably can flow through in a longitudinal direction, at least one electrode arranged within the cavity, at least one high voltage source for supplying the electrode with high voltage, wherein at least one insulation layer within the cavity is arranged on an inner surface of an outer shell of the housing, and in the interior of the cavity between the electrode and a counter electrode an electromagnetic field, preferably an inhomogeneous electromagnetic field or a partially inhomogeneous electromagnetic field can be generated with an active zone for the flow of compressed air to be prepared.
Furthermore, DE 10 2012 004 270 A1 discloses a device for treating a gas flow, in particular an exhaust gas flow of an internal combustion engine, having at least one radial space through which the gas flow can flow radially and which extends substantially radially from a central region to an outer collecting space, wherein the radial space is delimited by a first and a second approximately disk-shaped wall, and wherein a plurality of electrodes directed into the radial space protrude from the first wall. The first and second disk-shaped walls preferably run substantially parallel. The first disk-shaped wall is preferably made of an electrically insulating material with electrically conductive electrodes fastened therein, which are electrically connected to one another by electrical conductors running in or on the electrically insulating material. Two or more parallel radial chambers can be arranged around the central region, axially following one another.
U.S. Pat. No. 6,744,617 B2 discloses a discharge electrode bar in a housing. An air unit and discharge electrode assemblies are arranged in this housing in its lower region, as are a high-voltage unit and a control unit in its upper region. In this case, the housing consists of left- and right-split housing parts which can be divided and are detachably arranged on one another.
US 2009/0135538 A1 describes an ionizer in which high voltage is generated in a secondary portion of the transformer with a piezoelectric transformer that is formed from a ferroelectric element when an AC voltage is applied to a primary portion of this transformer. By suitably arranged ground electrodes at the upper and lower surfaces of the secondary portion of the piezoelectric transformer, a dielectric barrier discharge around the ground electrodes runs over a dielectric foil for insulation. Positive and negative ions are thereby generated in an air flow which is subsequently blown out of an air nozzle toward an object to be neutralized.
JP 2001085190 A describes an ionizer which generates a stable corona discharge. For this purpose, this ionizer amplifies a control signal with the aid of a piezoelectric transformer. The control signal to be amplified corresponds to the natural oscillation frequency of the piezoelectric transformer.
EP 1 241 755 A2 discloses an ion generating device. An electric field for generating ions between an electrode needle and a counter electrode plate is established and maintained therein. A surface discharge path A which runs through an air discharge opening and has the shortest distance between the electrode needle and the counter electrode plate is thereby generated, as is a surface discharge path B which does not run through the air discharge opening. The distances of the surface discharge paths A and B are varied by structural measures.
Previous systems have disadvantageous designs with respect to the generated ion equilibrium and the spatially homogeneous provision of ions with respect to the component to be discharged. Systems having an ion equilibrium which is suitable for reducing electrostatic voltages to the range well below +/−50 V relative to ground potential are much too big. Such systems often have individual electrode units combined with one blowing nozzle each. The resulting different geometries are thus not sufficiently compact. The relatively large distance of these electrode/blow nozzle units also leads to a spatially inhomogeneous output of the ions, which often leads to strip-like discharges on the components. In contrast, smaller systems without air support for blowing out the ions do not reach the required ion equilibrium since the physically caused imbalance between positive and negative corona discharge combined with the unavoidable partial recombination of generated charge carriers leads to an ion equilibrium that is very difficult to control, and, resulting from this, to significantly higher residual charges than the above-mentioned +/−50 V.
The object of the invention is to overcome the aforementioned disadvantages of the prior art and to propose a suitable design.
The object is achieved by the features of the main claim and by the features of the independent claims. Preferred embodiments are the subject matter of the dependent claims in each case.
According to the invention, a device for the ionization of gaseous media has a feed channel with a gas feed, a vertical channel with at least one gas outlet, and at least one ionization unit. The at least one ionization unit is provided with an electrode and is designed as a connecting channel from the feed channel to the distribution channel. The electrode is configured to ionize the gas flowing from the feed channel to the distribution channel through the ionization unit. The device is characterized in that the gas flows around the electrode, and the at least one gas outlet is designed as one or more nozzles or a plurality of openings.
For the purposes of this document, an ionization unit serves to generate ions within a gaseous medium. In particular and without being limited thereto, ionization units generate the ions by means of high electrical field densities. Other forms of ionization units may contain UV light sources, thermionic emission sources, or even radioactive sources. Ionization units which are based on the principle of field ionization and field emission naturally require at least two electrodes to form the required strong electrical fields. At least one electrode often has a filigree geometry—for example in the form of needles—in order to bring about a local bundling of the electrical field lines and the necessary high field strength of the associated strong inhomogeneity of the electric field. Associated counter electrodes are usually planar. For example, without being limited thereto, counter electrodes can be arranged cylindrically about a needle electrode and, if the spacing is small, a direct flow of current in the form of a sparkover or gap spark, which may be caused by the formed charge carriers, can be prevented by using electrically insulating materials.
In the context of the present document, nozzles and openings do not necessarily have a circular cross-section. Rather, nozzles and openings can, for example, be designed and without being limited thereto, as slots, bores or milled recesses of any geometry.
The solution to the object comprises a method for partial ionization of a gaseous medium with the device according to the invention, wherein the method comprises the following steps:
In the context of this invention, the operating pressure is the pressure which is necessary to enable a flow of the gaseous medium from the feed channel through the ionization unit until it is blown out. This is achieved by a pressure gradient, wherein the feed channel is placed under a higher pressure than the distribution channel, and the pressure conditions within the distribution channel are above the ambient pressure.
For the purposes of this document, an at least partial ionization of a gaseous medium is understood to mean that not all of the present gas particles are in the form of atoms or neutral molecules.
Complete ionization of the gaseous medium is not the issue here since a destructive current flow between the ionization unit and the corresponding counter electrode would thus occur due to the increasing electrical conductivity. Of course, complete ionization under normal atmospheric conditions—around 1013 hPa air pressure, a relative humidity of about 40%, and ambient temperature of about 20° C.—is not possible due to recombination. Something like this is only achieved in plasmas.
In this respect, partial ionization is a situation that does not change.
In embodiments of the invention, the gaseous medium is air, purified air, nitrogen, argon, carbon dioxide, oxygen, or a mixture thereof.
Advantageously, industrially and commercially available gases or prefabricated gas mixtures can therefore be used. This makes it advantageously possible to make a prediction about the degree of ionization to be expected. Furthermore, in embodiments of the invention, an additional bypass is arranged in such a way that the gaseous medium can be guided partially past the ionization unit. The possibility is thus advantageously created to add portions of the gaseous medium without ions to the ion-containing medium after it flows around the electrode, and thus to achieve an elevated blowing effect. This advantageously makes it possible to individually adapt the intended charge-reducing and cleaning effect.
In embodiments of the invention, the openings or nozzles are arranged in a defined manner on the surface of the distribution channel. The definition of the arrangement is preferably specified by the parameterization of at least one one-dimensional curve in three-dimensional space in which the center points of the openings or nozzles are arranged.
Based on a pressure gradient from the inlet into the distribution channel and up to the gas outlet, a preferred direction can be defined. Along a preferred direction defined in this way, the parameterization of the opening or nozzle points has portions different than zero. This advantageously makes it possible to select positions of the openings or nozzles which are calculated in a manner optimized for flow. Such parameters or parameterizations can be implemented more easily in manufacturing plants, and the manufacturing process can run automatically at this point. Thus, economically efficient production is made possible simultaneously with a maximum degree of individualization. Examples of the one-dimensional curve are straight lines or arcs in the simplest case.
In embodiments of the invention, the electrically insulating material of the ionization unit is made of plastic, glass, ceramic or synthetic resin. This advantageously allows the unavoidable erosion process caused by the impacting ions to be influenced. Since ozone unavoidably arises with corona discharges which can change the materials by its oxidative effect, materials which are resistant to this oxidative effect can advantageously be selected. If there is an economic interest, either a material with high wear can thus be used—which is significantly cheaper for the initial purchase, or suitable ceramics can preferably be installed in systems which are designed for maintenance-free continuous operation. In general, a broad selection of possible electrically insulating materials offers an advantage in production, since a wide variety of geometries can thus also be used.
In embodiments of the invention, the feed channel runs in a feed plane; the distribution channel runs in a distribution plane. These two planes are substantially parallel to one another. In this way, feed channels of any shape and analogously shaped distribution channels are taken into account, wherein the feed and distribution channels formed in this way run parallel to one another. By way of example, without being limited thereto, two identical tube pieces are used in the simplest case. The length of the employed tube pieces exceeds their own diameter multiple times, and both tube pieces run as parallel as possible in their arrangement and orientation. In a further example without restriction, the feed channel and distribution channel are designed annular. In this case, the embodiment can be such that the feed plane and the distribution plane are concentric (using a more abstract plane definition). The planes are understood to be the lateral surfaces of concentric cylinders. This is advantageous since the device can thus be adapted to the geometry of the objects to be cleaned or discharged. An advantageous flow around the objects is achieved in this way, and the surface effect of the cleaning medium is optimized. In embodiments of the invention, the high voltage is designed as an alternating high voltage. In this case, peak values of the voltages from 1 kV up to 50 KV are achieved. Preferably, peak values of the voltages of 1.5 kV to 40 kV are set here, particular preferably of 2 kV to 35 kV. This is advantageous because it can reinforce the good compromise between the design and the degree of ionization.
In embodiments of the invention, the required high voltage to form the required electrical fields is realized by high-voltage sources integrated in the device, which are operated by a low voltage fed in from the outside. This has an advantageous effect on the compactness of the device.
It has proven to be advantageous for a very good ion equilibrium and thus a minimization of the residual charge on the object to be discharged if the distribution channel is at least partially surrounded by a grounded, parallel electrical conductor. This electrical conductor is designed, for example, and without being limited thereto, as a metallic film web or metal sheet.
In embodiments of the invention, measures are applied for controlling and/or regulating the high voltage for the ionization unit within the device. These also include, without being limited thereto, monitoring devices for monitoring the high voltage and the degree of ionization of the gaseous medium.
In embodiments of the invention, the operating pressure of the gaseous medium is set between 50 mbar/50 hPa and 20 bar/2 MPa. This is advantageous since the required flow conditions can be achieved with this pressure range. In gaseous media with pressures below 50 mbar/50 hPa, statistical impact processes increasingly take place as transport phenomena. With decreasing pressure, these processes are increasingly less suitable for forming a continuous flow and a resulting ion transport. In the pressure range above 20 bar or 2 MPa, gas particles, in particular the generated ions, have a significantly reduced average clear travel path, which leads to increased recombination. Furthermore, the advantageous pressure range can be achieved with commercially available measures, which entails economic advantages in construction and supply.
Another aspect of the invention relates to the use of the device according to the invention for at least partial ionization of a gaseous medium. A cascaded device made of a feed channel and a plurality of distribution channels with at least one ionization unit is also conceivable. This is advantageous in order to allow an optimal discharge effect even for the most complex objects of larger dimensions, while maintaining the optimized design of a single ionizer according to the invention.
In order to realize the invention, it is also expedient to combine the above-described embodiments and the features of the claims.
The object of the invention is described in more detail in the following by non-restrictive figures and exemplary embodiments.
In one embodiment, the feed channel (101) and the distribution channel (104) are arranged analogously to the device described in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 117 682.4 | Jul 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/064842 | 6/1/2022 | WO |
