Device and method for generating dielectric barrier discharges, method for setting operating parameters of a control device, computer program and computer-readable storage medium

Abstract

The invention relates to a device for generating a dielectric barrier discharge, the device comprising a discharge reactor and a control device (13). The discharge reactor comprises a thermoelectric component (1) and an electrode (2). The control device (13) comprises a high-voltage source (12) that is designed to apply a high-voltage potential to the electrode (2) sufficient to ignite the dielectric barrier discharge, wherein the dielectric barrier discharge results in a gas being enriched with reactive species. The control device (13) is designed to set operating parameters of the high-voltage source (12) and of the discharge reactor appropriately for a desired composition of the enriched gas. A further aspect relates to a method for generating dielectric barrier discharges. Further aspects relate to a method for setting operating parameters of a control device, to a computer program and to a computer-readable storage medium.

Description

[0001] Description

[0002] Device and method for generating dielectric barrier discharges, method for setting operating parameters of a control device, computer program and computer-readable storage medium

[0003] The subject matter of the present application is a device and a method for generating dielectric barrier discharges, a method for setting operating parameters of a control device, a computer program and a computer-readable storage medium.

[0004] From WO 2022 / 058 333 A1 a plasma reactor is known which is designed to cool a process gas by means of a Peltier element.

[0005] The object of the present invention is to provide an improved device for generating dielectric barrier discharges, as well as improved methods for operating the device and for adjusting the operating parameters. Further objects include providing a computer program for implementing the method and a computer-readable storage medium for executing the computer program.

[0006] These problems are solved by the subject-matter of the independent claims.

[0007] A device for generating a dielectric barrier discharge is proposed, which device has a discharge reactor and a control device. The discharge reactor has a thermoelectric component and an electrode. The control device has a high-voltage source and a low-voltage source. The high-voltage source is designed to apply a high-voltage potential to the electrode which is sufficient to ignite the dielectric barrier discharge, wherein a gas is enriched with reactive species by the dielectric barrier discharge. The low-voltage source is designed to adjust a current through the thermoelectric component. The control device is designed to suitably adjust operating parameters of the high-voltage source and the low-voltage source for a desired composition of the enriched gas.

[0008] The control device can thus be designed to always select the optimal operating point for the device. The control device can take into account the influence of the individual operating parameters on the generated reactive species and also the interactions between the individual operating parameters.

[0009] The operating point of the device is characterized by the setting of the device's operating parameters. These operating parameters determine which reactive species are generated in which quantities during the dielectric barrier discharge. Several operating parameters of the device can now be specifically adjusted to achieve a desired composition of the enriched gas with the reactive species.

[0010] The high-voltage source can be an alternating voltage source. Accordingly, the high-voltage potential applied to the electrode can vary with the frequency of the alternating voltage generated by the high-voltage source. High voltage here can be defined as an alternating voltage with an amplitude of 1 kV or more.

[0011] The low-voltage source can be a direct current source. Accordingly, a direct current can flow through the thermoelectric component. Depending on the direction of the direct current, the thermoelectric component can cool or heat / warm a gas in the discharge reactor.

[0012] The control device can determine the operating parameters by input signals applied to the low voltage source and to the high voltage source.

[0013] In a first embodiment, a thermoelectric barrier discharge can be ignited in the discharge reactor, in which the thermoelectric component acts as a counter electrode. The dielectric barrier discharge can be ignited between the electrode and the thermoelectric component acting as a counter electrode.

[0014] The thermoelectric component can be arranged in the reactor such that a temperature of the gas can be changed by the thermoelectric component. The thermoelectric component can either cool or heat the gas before and / or during the dielectric barrier discharge.

[0015] The thermoelectric component can in particular be a Peltier element or a component that has a thermoelectric ceramic material. Since the device can be designed to select the operating parameters so that the desired gas composition for the activated gas is always produced, errors when using the device, for example for disinfection, can be ruled out. Additional system components for supplying chemical substances can therefore be dispensed with and consumables can be saved. If the reactive species are semi-stable chemical agents with short half-lives for which storage and external provision is not possible, the device offers the option of generating them in situ so that they can be used directly.

[0016] The device can be designed to adjust each operating parameter independently of the other operating parameters. The operating parameters can be adjusted dynamically, i.e., the settings can be continually adjusted during ongoing operation. Various processes with different active substances to be generated in situ can be simulated in a single device.

[0017] The operating parameters of the high-voltage source can comprise at least one selected from an amplitude of the high-voltage potential, a frequency of the high-voltage potential and a pulse-width modulation of the high-voltage potential, wherein a duty cycle and / or a modulation frequency are set during the pulse-width modulation.

[0018] The amplitude of the high-voltage potential of an alternating voltage signal generated by the high-voltage source can be used to adjust the number of reactive species generated during the dielectric barrier discharge and the ratio of the reactive species to each other. Overall, the number of reactive species generated increases with increasing amplitude. However, the proportion of each reactive species in the enriched gas composition differs depending on the selected high-voltage alternating voltage amplitude.

[0019] The amplitude of the high voltage can be up to 8 kV. The high-voltage alternating current can have a frequency between 15 kHz and 100 kHz, preferably 20 to 40 kHz.

[0020] The duty cycle can be adjusted via pulse width modulation of the high-voltage potential. The duty cycle specifies the ratio of a time period in which a signal is applied to the electrode, resulting in dielectric barrier discharges, to a time period in which no signal is applied to the electrode and no dielectric barrier discharges are ignited. In this way, pulse width modulation makes it possible to regulate the power of the dielectric barrier discharge. Pulse width modulation of the high-voltage alternating current thus changes the power density in the reactor, which has a direct influence on which reactive species are generated during the dielectric barrier discharge. Furthermore, with pulse width modulation, a modulation frequency can be set by the control device.

[0021] The operating parameters of the low-voltage source, which are adjusted by the control device, can include the current flowing through the thermoelectric component. By changing the current, the intensity and direction of the heat transferred through the module can be adjusted, thus controlling the temperature of one side of the thermoelectric component.

[0022] The thermoelectric component can be used for both cooling and heating the gas in the discharge reactor. Cooling the gas, in particular, can increase the ozone concentration in the enriched gas. However, heating the gas increases the production of nitrogen oxides as reactive species, which degrade the ozone and thus lead to a reduced ozone concentration in the enriched gas.

[0023] The operating parameters mentioned here are not considered in isolation from one another. Rather, the control device can be designed to always take into account the influence of each of the operating parameters mentioned on the composition of the enriched gas.

[0024] The control device can further be configured to control a chemical composition of the reactive species generated during the dielectric barrier discharge by performing pulse width modulation of the high-voltage potential and / or adjusting a current intensity of the current flowing through the thermoelectric component and / or adjusting an amplitude of the high-voltage potential and / or adjusting a frequency of the high-voltage potential. Preferably, all four of the operating parameters mentioned here are always adapted to the desired chemical composition. Furthermore, the control device can be configured to take into account environmental parameters that likewise have a significant influence on the composition of the reactive species generated during the dielectric barrier discharge.

[0025] In particular, the control device can be designed to take into account at least one or more of the following environmental parameters when setting the operating parameters: a flow rate of the gas through the discharge reactor, a composition of the gas and / or a temperature of the gas before and / or upon entry into the discharge reactor. Alternatively or additionally, an ambient temperature can be taken into account by the control device when setting the operating parameters. Taking these environmental parameters into account can make it possible to model the mapping function of the plasma chemistry even more precisely and to adapt the composition of the enriched gas even more precisely to a desired composition.

[0026] Gases that can be introduced into the discharge reactor include, for example, air, pure oxygen, synthetic air or compressed dry air (CDA). These gases differ in their behavior during dielectric barrier discharge, so that the type of gas used influences the type and amount of reactive species produced. For example, the humidity of the gas used plays a role in the type and amount of species produced during dielectric barrier discharge. The device can have sensors that measure the environmental parameters. Alternatively, the influence of the environmental parameters can be taken into account indirectly by recording and evaluating current pulses generated in the discharge reactor.Alternatively, the influence of environmental parameters can be taken into account indirectly by comparing the composition of the produced species with the desired composition and adjusting the operating parameters taking into account the comparison result.

[0027] A surface of the electrode facing the thermoelectric component may have protrusions. A dielectric barrier discharge (SDBD) may occur at the protrusions, while volume dielectric barrier discharges (VDBD) may be triggered in the spaces between two protrusions where the electrode is spaced from the thermoelectric component. Accordingly, the device may enable a hybrid mode of operation in which both surface and volume discharges are present.

[0028] The projections of the electrode can bear against the thermoelectric component. The projections can serve both as a discharge point for surface discharges and as spacers to define a distance between the thermoelectric component and the regions of the electrode which do not have projections. In this way, a volume for the volume discharges can be defined by a length of the projections. The thermoelectric component can have a plurality of thermoelectric elements and metal bridges, wherein each metal bridge connects two adjacent thermoelectric elements to one another. In particular, the metal bridges can connect the thermoelectric elements to one another in a meandering shape, wherein the metal bridges are arranged alternately on an upper side of the thermoelectric component, which faces the electrode, and on an underside of the thermoelectric component, which faces away from the electrode.The projections of the electrode can be arranged such that each projection is exactly opposite a metal bridge on the top side of the thermoelectric component. The projection can be arranged centrally on the metal bridge. The metal bridges can be covered by a dielectric barrier layer, for example a ceramic layer. The projections can be adjacent to the dielectric barrier layer.

[0029] Heat generated on the electrode surface during the dielectric barrier discharge can be dissipated via the electrode's protrusions. The central arrangement of the protrusions relative to the metal bridges allows for particularly effective heat transfer and prevents unwanted parasitic discharges inside the thermoelectric component.

[0030] The high-voltage source can be autoresonant. A high-voltage source is described as autoresonant if it is designed to continuously adjust the frequency of the high-voltage signal it generates so that the discharge reactor it powers is operated in a resonant mode. In an alternative embodiment, the discharge reactor can be operated at a frequency that does not correspond to the resonant frequency of the discharge reactor.

[0031] The control device can have a computing unit designed to determine the appropriate operating parameters for a desired composition of the enriched gas. The control device can then adjust the operating parameters according to the specifications of the computing unit.

[0032] The computing unit can be designed to determine the operating parameters in an analytical method, in a regression method, in a numerical method, in a computer-implemented method or by means of a self-learning algorithm.

[0033] The device can have sensors designed to determine the composition of the enriched gas, wherein the control device is designed to compare the composition determined by the sensors with the desired composition and to adapt the operating parameters depending on the result of the comparison. Accordingly, the sensors can enable feedback, in which a generated signal describing the gas composition in the enriched gas is compared with the desired gas composition. The feedback can be used to iteratively adjust the operating parameters to achieve the desired gas composition. During the dielectric barrier discharge, current pulses can be generated in the discharge reactor.The device can be designed to measure the current pulses and to determine the reactive species generated from the frequency and / or the magnitude of the measured current pulses. The control device can be designed to regulate the operating parameters as a function of the measured current pulses. The control device can be designed to regulate the operating parameters as a function of the measured current pulses, wherein the control device can additionally take into account one or more of the following parameters: a flow rate of the gas through the discharge reactor, a composition and / or a temperature of the gas upon entry into the discharge reactor and / or an ambient temperature.

[0034] By using sensors or evaluating current pulses generated in the discharge reactor, it is possible to take into account the influence of environmental parameters on the composition of the enriched gas without having to measure every environmental parameter.

[0035] A further aspect concerns a method for generating a dielectric barrier discharge. In this method, the device described above can be used, in particular.

[0036] The method uses a device comprising a discharge reactor and a high-voltage source, wherein the discharge reactor comprises a thermoelectric component and an electrode, and wherein the control device comprises a high-voltage source and a low-voltage source. The high-voltage source is designed to generate a high-voltage potential between the electrode and the high-voltage source. The method comprises the steps of:

[0037] - Setting a current through the thermoelectric component, wherein the current is set by the low voltage source,

[0038] - applying a high-voltage potential to the electrode so that a dielectric barrier discharge is ignited, wherein the dielectric barrier discharge enriches a gas with reactive species, wherein the high-voltage potential is applied by the high-voltage source, and

[0039] - Adjusting operating parameters of the high voltage source and the low voltage source to produce a desired composition of the enriched gas, wherein the control device adjusts the operating parameters.

[0040] The operating parameters of the high-voltage source can comprise at least one selected from an amplitude of the high-voltage potential, a frequency of the high-voltage potential and a pulse-width modulation of the high-voltage potential, wherein a duty cycle and / or a modulation frequency are set during the pulse-width modulation, and wherein the operating parameters of the low-voltage source comprise a current intensity of the current flowing through the thermoelectric component.

[0041] The setting of the operating parameters carried out by the control device to produce the desired composition of the enriched gas can be determined using a modeling function which determines from input variables describing a gas entering the discharge reactor and from the operating parameters output variables which describe the gas leaving the discharge reactor.

[0042] The input variables may comprise at least one selected from the chemical composition of the gas entering the discharge reactor , the temperature of the gas entering the discharge reactor , and the flow rate of the gas entering the discharge reactor .

[0043] The input variables may comprise at least one selected from an ambient temperature and current pulses generated in the discharge reactor.

[0044] The output variables may comprise at least one selected from a temperature of the gas exiting the discharge reactor, a flow rate of the gas exiting the discharge reactor, and a composition of the gas exiting the discharge reactor.

[0045] A further aspect relates to a method for adjusting operating parameters of a control device that controls a discharge reactor. This can be the control device described above, which has a high-voltage source and a low-voltage source, and the discharge reactor described above, which has an electrode and a thermoelectric component. The method for adjusting operating parameters of the control device can be part of the method described above for generating a dielectric barrier discharge.

[0046] The method for setting operating parameters of the control device comprises the following steps: - Determination of operating parameters of the high-voltage source and the low-voltage source so that a dielectric barrier discharge is generated at the electrode, in which a desired composition of the enriched gas is generated,

[0047] - Adjustment of the operating parameters to the values ​​determined in the previous step.

[0048] The operating parameters of the high-voltage source can comprise at least one selected from an amplitude of the high-voltage potential, a frequency of the high-voltage potential and a pulse-width modulation of the high-voltage potential, wherein a duty cycle and / or a modulation frequency are set during the pulse-width modulation, and wherein the operating parameters of the low-voltage source comprise a current intensity of the current flowing through the thermoelectric component.

[0049] The setting of the operating parameters carried out by the control device to produce the desired composition of the enriched gas can be determined using a modeling function which determines from input variables describing a gas entering the discharge reactor and from the operating parameters output variables which describe the gas leaving the discharge reactor.

[0050] The input variables may include at least one selected from the chemical composition of the gas entering the discharge reactor, the temperature of the gas entering the discharge reactor, and the flow rate of the gas entering the discharge reactor. The input variables may include at least one selected from an ambient temperature and current pulses generated in the discharge reactor.

[0051] The output variables may comprise at least one selected from a temperature of the gas exiting the discharge reactor, a flow rate of the gas exiting the discharge reactor, and a composition of the gas exiting the discharge reactor.

[0052] A further aspect relates to a computer program that carries out the method described above for determining the operating parameters. The computer program comprises: a first step in which the desired composition of the enriched gas is entered, and a second step in which the method is carried out. The desired gas composition can be entered by a user or by a higher-level system to which the device is connected. Alternatively, the first step can be carried out by a permanently programmed input of a desired gas composition.

[0053] The determination of the operating parameters can be carried out by means of an analytical method, a regression method, a numerical method, a computer-implemented method or a self-learning algorithm.

[0054] A further aspect relates to a computer-readable storage medium comprising the computer program described above, wherein the computer program comprises . Preferred embodiments are described below with reference to the figures.

[0055] Figure 1 shows a discharge reactor.

[0056] Figure 2 shows the discharge reactor and a control device.

[0057] Figure 3 shows schematic diagrams showing the influence of operating parameters on the reactive species produced .

[0058] Figure 4 shows schematically a method for generating a dielectric barrier discharge.

[0059] Figure 5 shows schematically which variables are influenced by the operating parameters adjustable by the control device.

[0060] Figure 6 shows a discharge reactor according to an alternative embodiment.

[0061] Figure 1 shows a discharge reactor of a device for generating a dielectric barrier discharge, which comprises a thermoelectric component 1 and an electrode 2. The thermoelectric component 1 is a Peltier element.

[0062] The thermoelectric component 1 is an electrothermal converter. It is designed to change the temperature of a gas that is introduced into the discharge reactor as process gas and exits the discharge reactor as enriched gas. If a direct voltage is applied to the thermoelectric component 1 and a direct current flows through the thermoelectric component 1, a temperature difference is generated based on the Peltier effect, the Seebeck effect, or the Thomson effect. The Peltier element 1 can be used both for cooling and—if the current direction is reversed—for heating the process gas.

[0063] The thermoelectric component 1 has thermoelectric elements 3 which are connected to one another by metal bridges 4 to form a meander-shaped structure.

[0064] If the thermoelectric component 1 is a Peltier element, semiconductor elements are used as thermoelectric elements. The semiconductor elements are connected in series with each other via metal bridges 4, with p-doped semiconductor elements and n-doped semiconductor elements alternating. The semiconductor elements can be made of, for example, bismuth telluride or silicon germanium.

[0065] If a direct current is passed through the thermoelectric component 1, a temperature difference is created at the metal bridges 4 due to the thermoelectric effect, for example the Peltier effect, and thus a warm and a cold side of the component.

[0066] The thermoelectric component 1 has a first ceramic plate 5a and a second ceramic plate 5b. The first ceramic plate 5a is arranged on a top side facing the electrode. The second ceramic plate 5b is arranged on a bottom side facing away from the electrode. The ceramic plates 5a, 5b can comprise aluminum oxide or consist of aluminum oxide. Alternatively or additionally, the ceramic plates 5a, 5b can comprise aluminum nitride or consist of aluminum nitride.

[0067] The ceramic plates 5a, 5b cover the metal bridges 4. In the embodiment shown in Figure 1, the ceramic plates 5a, 5b are arranged directly on the metal bridges 4. The metal bridges 4 form a thermal contact surface, via which heat or cold is transferred to the ceramic plates 5a, 5b. The ceramic plates 5a, 5b act as heat-conducting plates. The ceramic plates 5a, 5b extract heat from the process gas or transfer heat to the process gas.

[0068] The electrode 2 is arranged parallel to one of the first ceramic plates 5a. The electrode 2 lies opposite the thermoelectric component 1 and, in the embodiment shown in Figure 1, is spatially separated from the thermoelectric component 1. Between the electrode 2 and the thermoelectric component 1 there is a gap 6. The gap 6 between the thermoelectric component 1 and the electrode 2 can have a width between 0.01 mm and 1.0 mm, preferably between 0.05 mm and 0.5 mm.

[0069] The device is designed to trigger a dielectric barrier discharge between the electrode 2 and the thermoelectric component 1. The dielectric barrier discharge involves the ignition of a non-thermal atmospheric pressure plasma. During the dielectric barrier discharge, the process gas is enriched with reactive species. An alternating voltage potential with a high amplitude is applied to the electrode 2 with reference to an electrical potential of the thermoelectric component 1. A high-voltage alternating voltage is thus created between the thermoelectric component 1 and the electrode 2. A dielectric barrier discharge DBD is ignited between the thermoelectric component 1 and the electrode 2, with the ceramic plate 5a facing the electrode 1 acting as a dielectric barrier.

[0070] Alternatively or additionally, a layer acting as a dielectric barrier can be attached to the side of the electrode 2 facing the thermoelectric component 1.

[0071] A direct current flows through the thermoelectric component 1. A direct voltage potential difference through the low-resistance thermoelectric elements 3 of the thermoelectric component 1 is negligible compared to the high voltage required for the dielectric barrier discharge. Conversely, the current density typically occurring during the dielectric barrier discharge is small compared to the direct current flowing through the thermoelectric elements 3. Accordingly, the cooling function of the thermoelectric component 1 and the discharge function of the device do not negatively influence each other.

[0072] In an alternative embodiment, the thermoelectric component is not arranged opposite the electrode. In the alternative embodiment, the device can be configured to ignite the dielectric barrier discharge between the electrode and a surface to which a ground potential is applied.

[0073] The thermoelectric element 1 is used in the device both in its function as a cooling or heating element that sets the temperature of the process gas, and as a counter electrode that, together with the electrode 2, triggers the dielectric barrier discharge. By combining the thermoelectric element 1 with the dielectric barrier discharge, the dielectric barrier discharge can be operated at a precisely set temperature and humidity, and the concentration and composition of active species produced during the dielectric barrier discharge can be adjusted and kept stable.

[0074] The thermoelectric element 1 makes it possible to regulate the temperature of the process gas located in the gap 6 between the electrode 2 and the thermoelectric element 1. If a thermoelectric element 1 is used for dielectric barrier discharge, it is possible to precisely adjust the temperature of the process gas during the discharge. The gas composition of the gases generated during the dielectric barrier discharge depends, among other things, strongly on the temperature of the process gas. In particular, the proportions of ozone (O3) and nitrous gases (NO, NO2, N0) generated x) are determined by the temperature. As the temperature increases, the production of nitrous gases is favored and the decomposition mechanisms of ozone in favor of nitrous gases are accelerated. The device further comprises a heat sink 9, which is attached to the ceramic plate 5b of the thermoelectric element 1, which faces away from the electrode 2. The heat sink 9 contributes, in addition to the thermoelectric element 1, to cooling the process gas.

[0075] The discharge reactor has a gas inlet 7 and a gas outlet 8. The process gas is admitted into the discharge reactor via the gas inlet 7. In the discharge reactor, the process gas is enriched with reactive species. The gas enriched in the discharge reactor is discharged from the discharge reactor via the gas outlet 8.

[0076] Furthermore, the device may alternatively or additionally comprise a fan 10 which is designed to conduct heat away from the heat sink and which thereby contributes to cooling.

[0077] Figure 2 shows the discharge reactor illustrated in Figure 1 and a control device 13 which is connected to the discharge reactor. The control device 13 has a low-voltage source 11 and a high-voltage source 12. The low-voltage source 11 applies a direct voltage in the low-voltage range to the thermoelectric component 1. A direct current therefore flows through the thermoelectric component 1. The thermoelectric component 1 is at a low-voltage electrical potential. The high-voltage source 12 applies a high alternating voltage potential to the electrode 2. Accordingly, a high potential difference arises between the thermoelectric component 1 and the electrode 2 and a dielectric barrier discharge occurs in the gap 6 between the electrode 2 and the thermoelectric component 1. The dielectric barrier discharge is a volume discharge.

[0078] The control device 13 is designed to control operating parameters of the low-voltage source 11 and operating parameters of the high-voltage source 12. For this purpose, the control device 13 can have a computing unit 14, for example a microcontroller, which is designed to issue control commands to the high-voltage source 12 and the low-voltage source 11.

[0079] The control device 13 is designed to adjust the operating parameters such that a desired composition of the enriched gas is achieved. The control device 13 can take into account that the type and quantity of the reactive species generated are influenced by both the temperature of the thermoelectric component 1 and the amplitude and pulse width modulation of the high-voltage alternating potential applied by the high-voltage source 12 to the electrode 2.

[0080] The control device 13 accordingly makes it possible to specifically produce the active substances or active substance combinations produced in the gas in the desired concentrations and ratios by adjusting the operating parameters accordingly. For the respective desired product gas composition, the control device 13 selects an optimally efficient operating point as the operating point of the device. The operating or operating point of the device is characterized by the respective settings of the operating parameters of the high-voltage source 12 and the low-voltage source 11.Since the reactive species generated in the process gas also depend on ambient conditions, for example on the type of process gas, on the temperature of the process gas when entering the discharge reactor and on the flow rate of the process gas through the discharge reactor, these ambient conditions can be taken into account by the control device 13 when setting the operating parameters.

[0081] The control device is designed to produce the desired composition of the activated gas by a targeted combination of the operating parameters, taking into account their mutual dependencies and the ambient conditions.

[0082] Figure 3 shows schematically the influence of the operating parameters on the generation of reactive species, using the device shown in Figure 2 with the process gas air.

[0083] In the curves plotted in the first line , the amplitude of the high voltage potential applied to the electrode is varied , while the temperature of the thermoelectric component is kept constant and no pulse width modulation of the high voltage signal is carried out .

[0084] In the four figures shown, from left to right, the concentrations of ozone, nitrogen oxides, peroxides and acids in the activated gas are plotted for different amplitudes of the high voltage signal. The first curve, which shows the ozone concentration, shows that with increasing amplitude the ozone concentration initially increases until a maximum is reached. If the amplitude is increased further beyond this maximum, the ozone concentration in the excited gas decreases. The reason for the decrease in ozone concentration in the enriched gas at high amplitudes is that mechanisms for the decomposition of ozone are stimulated if the high voltage signal has sufficiently high energy. In particular, nitrogen oxides are then produced during the dielectric barrier discharge, which cause ozone decomposition.

[0085] The second curve shows the concentration of nitrogen oxides in the enriched gas for various amplitudes of the high-voltage signal. The curve shows that at comparatively small amplitudes, almost no nitrogen oxides are produced. Only when the amplitude is sufficiently large does the concentration of nitrogen oxides in the enriched gas rise steadily with increasing amplitude.

[0086] The third curve shows the concentration of peroxides in the enriched gas for different amplitudes of the high-voltage signal. This concentration exhibits a maximum for medium amplitudes.

[0087] The fourth curve shows the concentration of acids in the enriched gas for different amplitudes of the high voltage signal.

[0088] In the second line it is assumed that pulse width modulation is used for the high-voltage signal. Pulse width modulation allows the power of the high-voltage signal to be controlled by setting a duty cycle of times when a signal is applied and times when no signal is applied. The horizontal axis of the curves shown in the second line shows the power, which is directly proportional to the duty cycle of the pulse width modulation. The vertical axis shows the concentrations of the reactive species in arbitrary units. The temperature during the gas discharge and the amplitude of the high-voltage signal remain constant.

[0089] The curves in the second row show that the concentration of all reactive species increases with increasing power. It should be noted, however, that the curves shown here are purely schematic and arbitrary units are used. In particular, the ratio of the proportions of the reactive species to one another changes with increasing power.

[0090] The third row shows four curves in which the temperature of the thermoelectric component is varied and the power and amplitude of the high-voltage signal remain constant. The first curve from the left shows the ozone concentration. It can be seen that the ozone concentration decreases with increasing temperature. To achieve a high ozone concentration, the thermoelectric component should therefore cool the process gas. The second curve shows that the concentration of nitrogen oxides increases with increasing temperature. The third curve shows that the concentration of peroxides decreases with increasing temperature. The fourth curve shows that the concentration of acids increases with increasing temperature. The curves shown in Figure 3 are purely schematic and do not take into account the interaction of the operating parameters with one another with regard to the reactive species produced.To select the optimal operating point, i.e. to optimally adjust the operating parameters, a precisely modeled mapping function of the plasma chemistry is required.

[0091] Figure 4 shows schematically a method for generating a dielectric barrier discharge with the device shown in Figure 2.

[0092] A gas flowing into the discharge reactor is described by input variables that are summarized in an input vector U . These input variables include an ambient temperature Tu of the device, a temperature T in , which the gas has upon entering the gas inlet 7 and which may deviate from the ambient temperature Tu under certain circumstances, a flow rate of the gas, which is referred to here as the mass flow of all gaseous components, and the concentrations ci, c i 2...c i mthe individual chemical components that make up the gas flowing into the discharge reactor.

[0093] A gas leaving the discharge reactor is described by output variables that are summarized in an output vector W . The output variables include a temperature T ou t of the gas leaving the discharge reactor , a flow rate of the gas leaving the discharge reactor and the concentrations c a i , c a 2...c a nof the individual chemical components making up the gas exiting the discharge reactor. The gas exiting the discharge reactor contains all the chemical components of the gas entering the discharge reactor and may also contain additional chemical components generated during the dielectric barrier discharge. These may include, for example, ozone, nitrogen oxides, or peroxides. Therefore, the number n of chemical components in the exiting gas is greater than or equal to the number m of chemical components in the gas entering the discharge reactor.

[0094] The control unit is now designed to influence the dielectric barrier discharge and the reactive species generated thereby. For this purpose, the control unit can regulate the operating parameters of the high-voltage source 12 and the low-voltage source 11. The operating parameters are summarized in Figure 4 as manipulated variables in the vector V. The manipulated variables include an amplitude U D of the high-voltage potential applied by the high-voltage source 12 to the electrode 2, a frequency f of the high-voltage potential applied by the high-voltage source 12 to the electrode 2, a pulse width modulation PWM of the high-voltage potential, in which the duty cycle and a modulation frequency f can be adjusted, and a current intensity I te c a current which is set by the low voltage source 11 through the thermoelectric component 1 and via which the temperature of the thermoelectric component 1 is regulated.

[0095] During the dielectric barrier discharge, short current pulses are generated in the discharge reactor; their frequency can be between 10 MHz and 50 MHz or their frequency can be greater than 50 MHz. The current pulses are generated by an electric current flowing between the electrode 2 and the respective counter electrode, with the thermoelectric component 1 forming the counter electrode in the embodiment shown in Figure 2. The magnitude of the current pulses is, to a first approximation, proportional to the discharge intensity and, to a large extent, also proportional to the concentration of the newly generated chemical species. If pure oxygen is used as the process gas, the magnitude of the current pulses is proportional to the amount of ozone generated. Conclusions can be drawn about the reactive species generated from the frequency of the current pulses.

[0096] The current pulses generated in the discharge reactor can be detected and evaluated by the control device 13. In this way, the control device 13 can measure the type and quantity of the reactive species generated.

[0097] In Figure 4, the current pulses are denoted by S. The current pulses are coupled out of the discharge reactor and are captured in the input vector U. The input vector U thus contains the input variables describing the ambient conditions and the gas entering the discharge reactor, as well as information obtained from the current pulses.

[0098] In the control device, the output variables are now pre-calculated using a modeling function f(U,V), wherein the input vector U and the vector V, in which the manipulated variables are combined, are taken into account as parameters in the modeling function f(U,V). The modeling function f(U,V) is a multi-dimensional function with a large number of variables. The modeling function f(U,V) can be a purely analytical function that is calculated using an analytical method. The modeling function f(U,V) can be calculated using a regression method. The modeling function f(U,V) can be calculated using a numerical method. The modeling function f(U,V) can be a computer-implemented method, wherein the modeling function f(U,V) is carried out, for example, by a self-learning algorithm.The modeling function f (U, V) can be a combination of the methods mentioned here.

[0099] In the modeling function f (U, V) the output variables are represented in the form of an output vector W r calculated. The calculated output vector W r includes a calculated temperature T r ou t of the gas at the outlet from the discharge reactor, a calculated flow rate and calculated concentrations c r i , c r 2...c r n of the chemical components of the gas at the outlet from the discharge reactor. The calculated output vector W r The summarized quantities represent approximate values ​​of the actual output quantities. The more accurately the plasma chemistry during the dielectric barrier discharge is represented by the modeling function f (U, V), the smaller the deviation between the calculated output quantities and the actual output quantities.

[0100] A desired chemical composition of the enriched gas is transmitted to the control device by a user or by a higher-level system connected to the device. The computing unit 14 then determines the optimal operating point of the discharge reactor for generating the desired chemical composition. To do this, the computing unit 14 determines the values ​​to which the operating parameters of the low-voltage source 11 and the high-voltage source 12 should be set based on the modeling function f(U,V). The computing unit 14 can determine the operating parameters using an analytical method, a regression method, a numerical method, a computer-implemented method or a self-learning algorithm.

[0101] The computing unit 14 then transmits the operating parameters to the high-voltage source 12 and to the low-voltage source 11, which can be arranged in a common driver module.

[0102] The control unit 13 is further designed to generate the input vector U, the vector V describing the manipulated variables, and the calculated output vector W r to the higher-level system. These values ​​can then be displayed on a screen by the higher-level system.

[0103] Figure 5 shows how the operating parameters which can be changed by the control device 13 influence the reactive species produced .

[0104] On the left-hand side of Figure 5, the operating parameters that can be changed by the control device 13 as well as further parameters that describe the gas flowing into the discharge reactor are plotted. On the right-hand side, process parameters that describe the dielectric barrier discharge are plotted. Arrows show which operating parameters or parameters describing the gas influence which process parameter. The operating parameters that can be changed by the control device 13 include the amplitude of the high-voltage potential applied to the electrode 2, a pulse-width modulation of the high-voltage potential applied to the electrode 2 and a current strength through the thermoelectric component 1. Furthermore, the type of gas used and the flow rate of the gas are plotted on the left-hand side.

[0105] The type of gas used essentially determines which molecules are available as reactants in the dielectric barrier discharge.

[0106] The amplitude of the high-voltage potential applied to electrode 2 influences the energy and power density of the dielectric barrier discharge. Furthermore, the amplitude of the high-voltage potential applied to electrode 2 also influences the process temperature. A higher amplitude, compared to a lower amplitude, results in higher energies and a higher power density in the dielectric barrier discharge. This also generates more heat, which increases the process temperature.

[0107] The duty cycle of the pulse width modulation influences the power density of the dielectric barrier discharge and the process temperature. If the proportion of time periods during which no high-voltage potential is applied to electrode 2 is increased, the power density decreases and less heat is generated.

[0108] The current through the thermoelectric component 1 influences the process temperature. The thermoelectric component 1 can cool or heat the gas in the discharge reactor.

[0109] The flow rate of the gas through the discharge reactor influences the power density of the dielectric barrier discharge and the process temperature.

[0110] Both the ozone concentration and the ozone production rate increase with increasing amplitude of the high voltage signal, whereby saturation occurs at a sufficiently large amplitude and the ozone concentration and the ozone production rate do not increase further with an increasing amplitude of the high voltage signal.

[0111] If the gas flow rate is increased, the reactive species produced, for example ozone, are transported away from the discharge reactor more quickly. Accordingly, the concentration of the reactive species in the escaping gas decreases with increasing flow rate. At the same time, new process gas is fed to the discharge reactor more quickly, so that the production rate of the reactive species increases with increasing flow rate. As the flow rate increases, a thermal separation layer between the electrode 2 and the dielectric barrier of the discharge reactor becomes smaller, so that heat dissipation is improved and the temperature of the process gas is reduced. A reduced temperature leads to an increased production rate of certain reactive species, for example ozone.Furthermore, the reduction in the thickness of the thermal barrier layer with increasing flow rate leads to better diffusion of reaction products of the dielectric barrier discharge, which likewise increases the production rate of reactive species. The ozone concentration in the escaping gas increases with increasing duty cycle, whereby the duty cycle is controlled by pulse width modulation of the high voltage signal. With increasing duty cycle, the ozone concentration initially increases almost linearly until a plateau in the ozone concentration is reached. Both an increasing amplitude and an increasing duty cycle can trigger ozone depletion mechanisms that explain plateaus in the ozone concentration with increasing duty cycle. The higher the amplitude of the high voltage signal, the lower the duty cycle at which the corresponding plateau is reached.During the transition from a pulse-width-modulated signal to a continuous signal, accumulated charge at the dielectric barrier can lead to an increase in the voltage of the microdischarges. Accordingly, a sharp increase in ozone concentration occurs when the duty cycle exceeds 90% and the signal is nearly continuous.

[0112] Cooling the thermoelectric component influences the ozone concentration, with the ozone concentration decreasing with increasing temperature. There is a nearly linear relationship between the temperature in the discharge reactor and the ozone concentration in the exiting process gas.

[0113] Overall, each of the operating parameters—temperature of the thermoelectric component, amplitude of the applied high voltage, and pulse-width modulation of the applied high voltage—influences the generation of reactive species in the discharge reactor. There are significant interactions between the influences of the operating parameters, and the ambient conditions, particularly temperature, composition, and flow rate of the incoming gas, must also be taken into account. Taking all of these parameters into account results in a well-modeled mapping function of the plasma chemistry during the dielectric barrier discharge, which is taken into account by the control device 13 of the present device.

[0114] Figure 6 shows a further embodiment of the discharge reactor. The electrode 6 has projections 15. The projections 15 are arranged on an upper side of the electrode 2, which faces the thermoelectric component 1. The projections 15 are arranged such that each projection 15 is centrally located opposite a metal bridge 4, which is arranged on the upper side of the thermoelectric component and connects two adjacent thermoelectric elements 3 to one another. The projections 15 bear against the ceramic layer 15a of the thermoelectric component 1.

[0115] The projections 15 fulfill various functions in the component. Surface discharges occur in the region of the projections. Accordingly, dielectric barrier discharges in the form of volume discharges and surface discharges occur in the discharge reactor. The ignition voltage for surface discharges is lower than for volume discharges.

[0116] The projections 15 also act as spacers between the electrode 2 and the thermoelectric component 1 and thus determine the volume of the volume discharges. Furthermore, the projections 15 can dissipate heat generated at the electrode 2 via direct contact to the thermoelectric component 1, thus reducing the temperature in the discharge space. This effect is particularly enhanced by the fact that each projection is centrally located opposite a metal bridge 4, since the metal bridges 4 have particularly high thermal conductivity.

[0117] In addition, the projections 15 hinder a gas flow through the discharge reactor and thereby enable a better mixing of the process gas, which leads to improved cooling and thus an increased ozone production rate in the discharge reactor.

[0118] Reference symbol list

[0119] 1 thermoelectric component

[0120] 2 electrodes

[0121] 3 thermoelectric element

[0122] 4 metal bridge

[0123] 5a first ceramic plate

[0124] 5b second ceramic plate

[0125] 6 gap

[0126] 7 Gas inlet

[0127] 8 Gas outlet

[0128] 9 heat sinks

[0129] 10 fans

[0130] 11 Low voltage source

[0131] 12 High voltage source

[0132] 13 Control device

[0133] 14 Computing unit

[0134] 15 lead

Claims

Patent claims 1. A device for generating a dielectric barrier discharge, comprising: - a discharge reactor comprising a thermoelectric component (1) and an electrode (2), and - a control device (13) having a high-voltage source (12) and a low-voltage source (11), wherein the high-voltage source (12) is designed to apply a high-voltage potential to the electrode (2) which is sufficient to ignite the dielectric barrier discharge, wherein a gas is enriched with reactive species by the dielectric barrier discharge, wherein the low-voltage source (11) is designed to adjust a current through the thermoelectric component (1), wherein the control device (13) is designed to suitably adjust operating parameters of the high-voltage source (12) and the low-voltage source (11) for a desired composition of the enriched gas.

2. Device according to claim 1, wherein the operating parameters of the high-voltage source (12) comprise at least one selected from an amplitude of the high-voltage potential, a frequency of the high-voltage potential and a pulse-width modulation of the high-voltage potential, wherein a duty cycle and / or a modulation frequency are set during the pulse-width modulation.

3. Device according to one of the preceding claims, wherein the operating parameters of the low-voltage source (11) comprise a current intensity of a current flowing through the thermoelectric component (1).

4. Device according to one of the preceding claims, wherein the control device (13) is designed to control a chemical composition of the reactive species generated during the dielectric barrier discharge by the control device (13) performing a pulse width modulation of the high-voltage potential and / or adjusting a current intensity through the thermoelectric component (1) and / or adjusting an amplitude of the high-voltage potential and / or adjusting a frequency of the high-voltage potential.

5. Device according to one of the preceding claims, wherein the control device (13) is designed to take into account a flow rate of the gas through the discharge reactor when setting the operating parameters.

6. Device according to one of the preceding claims, wherein the control device (13) is designed to take into account a composition and / or a temperature of the gas at the entry into the discharge reactor and / or an ambient temperature when setting the operating parameters.

7. Device according to one of the preceding claims, wherein the thermoelectric component (1) is a Peltier element.

8. Device according to one of the preceding claims, wherein a surface of the electrode (2) has projections (15).

9. Device according to claim 8, wherein the electrode (2) is opposite the thermoelectric component (1), and wherein the projections (15) bear against the thermoelectric component (1).

10. Device according to claim 9, wherein the thermoelectric component (1) has a plurality of thermoelectric elements (3), wherein the thermoelectric component (1) has metal bridges (4), wherein each metal bridge (4) connects two adjacent thermoelectric elements (3) to one another, wherein the projections (15) are arranged such that each projection (15) is located exactly opposite one metal bridge (4) on the upper side of the thermoelectric component (1), wherein the upper side of the thermoelectric component (1) faces the electrode (2).

11. Device according to one of the preceding claims, wherein the high voltage source (12) is autoresonant.

12. Device according to one of the preceding claims, wherein the control device (13) has a computing unit (14) which is designed to determine the suitable operating parameters for a desired composition of the enriched gas.

13. Device according to the preceding claim, wherein the computing unit ( 14 ) is designed to determine the operating parameters in an analytical method, in a regression method, in a numerical method, in a computer-implemented method or by means of a self-learning algorithm.

14. Device according to one of the preceding claims, wherein the device comprises sensors which are designed to determine the composition of the enriched gas, wherein the control device (13) is designed to compare the composition determined by the sensors with the desired composition and to adapt the operating parameters depending on the result of the comparison.

15. Device according to one of the preceding claims, wherein the thermoelectric component (1) is opposite the electrode (2) and is designed to act as a counter electrode to the electrode (2) during the dielectric barrier discharge, or wherein the electrode (2) is designed and arranged to ignite the dielectric barrier discharge against a surface at a ground potential. 16 . Device according to one of the preceding claims, wherein during the dielectric barrier discharge current pulses are generated in the discharge reactor, wherein the device is designed to measure the current pulses and to determine from the frequency and / or the Height of the measured current pulses to determine the generated reactive species, wherein the control device is designed to regulate the operating parameters depending on the measured current pulses.

17. Method for generating a dielectric barrier discharge with a device comprising a discharge reactor containing a thermoelectric component (I) and an electrode (2), and a control device (13) comprising a high voltage source (12) and a low voltage source (II), comprising the steps: - applying a current to the thermoelectric component, the current being adjusted by the low-voltage source (11), - applying a high-voltage potential to the electrode (2) so that a dielectric barrier discharge is ignited, wherein the dielectric barrier discharge enriches a gas with reactive species, wherein the high-voltage potential is applied by the high-voltage source (12), and - Adjusting operating parameters of the high-voltage source (12) and the low-voltage source (11) to produce a desired composition of the enriched gas, wherein the control device (12) adjusts the operating parameters.

18. Method according to claim 17, wherein the operating parameters of the high-voltage source (12) comprise at least one selected from an amplitude of the high-voltage potential, a frequency of the high-voltage potential and a pulse-width modulation of the high-voltage potential, wherein a duty cycle and / or a modulation frequency are set during the pulse-width modulation, and wherein the operating parameters of the low-voltage source (11) comprise a current intensity of the current flowing through the thermoelectric component (1).

19. Method according to claim 17 or claim 18, wherein the setting of the operating parameters, which is carried out by the control device (13) for generating the desired composition of the enriched gas, is determined using a modeling function (f (U, V)) which is derived from input variables (U) describing a gas entering the discharge reactor and from the operating parameters (V) output variables (W r ) which describe the gas escaping from the discharge reactor .

20. Method according to claim 19, wherein the input variables (U) comprise at least one selected from the chemical composition of the gas entering the discharge reactor, the temperature of the gas entering the discharge reactor and the flow rate of the gas entering the discharge reactor.

21. Method according to claim 19 or claim 20, wherein the input variables (U) comprise at least one selected from an ambient temperature and current pulses generated in the discharge reactor.

22. Method according to one of claims 19 to 21, wherein the output variables (W r ) at least one selected from a temperature of the gas exiting the discharge reactor, a flow rate of the gas exiting the discharge reactor and a composition of the gas exiting the discharge reactor.

23. Method for setting operating parameters of a control device (13) which controls a discharge reactor, wherein the control device (13) has a high-voltage source (12) and a low-voltage source (11), wherein the discharge reactor has an electrode (2) and a thermoelectric component (1), wherein the high-voltage source (12) is designed to apply a high-voltage potential to the electrode (2) which is sufficient to ignite the dielectric barrier discharge, wherein a gas is enriched with reactive species by the dielectric barrier discharge, wherein the low-voltage source (11) is designed to set a current to the thermoelectric component (1), wherein the method comprises the steps of: - determining operating parameters of the high-voltage source (12) and the low-voltage source (11), so that at the electrode ( 2 ) a dielectric barrier discharge is generated in which a desired composition of the enriched gas is produced, - Adjustment of the operating parameters to the values ​​determined in the previous step.

24. Method according to claim 23, wherein the operating parameters of the high-voltage source (12) comprise at least one selected from an amplitude of the high-voltage potential, a frequency of the high-voltage potential and a pulse-width modulation of the high-voltage potential, wherein a duty cycle and / or a modulation frequency are set during the pulse-width modulation, and wherein the operating parameters of the low-voltage source (11) comprise a current intensity of the current flowing through the thermoelectric component (1).

25. Method according to claim 23 or claim 24, wherein the setting of the operating parameters, which is carried out by the control device (13) for generating the desired composition of the enriched gas, is determined using a modeling function (f (U, V)) which is derived from input variables (U) describing a gas entering the discharge reactor and from the operating parameters (V) output variables (W r ) which describe the gas escaping from the discharge reactor . 26 . Method according to claim 25 , wherein the input variables (U) are at least one selected from the chemical composition of the discharge reactor , the temperature of the gas entering the discharge reactor and the flow rate of the gas entering the discharge reactor .

27. Method according to claim 25 or claim 26, wherein the input variables (U) comprise at least one selected from an ambient temperature and current pulses generated in the discharge reactor. 28 . Method according to one of claims 25 to 27 , wherein the output variables (W r ) at least one selected from a temperature of the gas exiting the discharge reactor , a flow rate of the gas exiting the discharge reactor and a composition of the gas exiting the discharge reactor .

29. A computer program that carries out a method according to any one of claims 23 to 28, the computer program comprising: a first step in which the desired composition of the enriched gas is input, and a second step in which the method according to any one of claims 23 to 28 is carried out.

30. Computer program according to claim 29, wherein the determination of the operating parameters is carried out by means of an analytical method, a regression method, a numerical method, a computer-implemented method or a self-learning algorithm.

31. A computer-readable storage medium comprising a computer program for carrying out the method of any one of claims 23 to 28, the computer program comprising: a first step in which the desired composition of the enriched gas is input, and a second step in which the method according to any one of claims 23 to 28 is carried out.

32. Computer-readable storage medium according to claim 31, wherein the determination of the operating parameters is carried out by means of an analytical method, a regression method, a numerical method, a computer-implemented method or a self-learning algorithm.

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