Method and system for transforming gas mixtures using pulsed plasma

Abstract

A method for converting a gas mixture into a higher-value gas mixture, comprising the steps of injecting the gas mixture into a pulsed plasma reactor, a dissociation step using a pulsed discharge to generate shock waves between two electrodes to produce gases, and releasing the produced gases into a region where they can be cooled and / or separated and / or collected. The dissociation step is also designed to provide passive re-ignition of the plasma if it is blown away by a continuous gas flow in the reactor.

Description

Technical Field

[0001] The present invention belongs to the field of gas production devices, and particularly relates to a reforming device for producing products with higher added value.

Background Art

[0002] Plasma discharge presents an electrophysical alternative for converting a gas mixture into a gas mixture with higher added value by means of a thermal approach (thermal decomposition), a thermocatalytic approach (reforming reaction), or an electrochemical approach (electrolysis).

[0003] Document US 6,395,197 B1 discloses a method and system for producing hydrogen and elemental carbon from natural gas and other hydrocarbons. Diatomic hydrogen and unsaturated hydrocarbons are produced as reactor gases in a high-speed quenching plasma reactor. During rapid quenching, the unsaturated hydrocarbons are further decomposed by heating the reactor gas. Other gases can be added at different stages of the process to form the desired final product and prevent reverse reactions. The products are hydrogen fuel and elemental carbon in powder form that can be used as feedstock for many industrial processes.

[0004] U.S. Patent No. 5,409,784 discloses a plasmotron-fuel cell device for generating electricity, where the plasmotron receives a hydrocarbon fuel and reforms the hydrocarbon fuel to produce a hydrogen-rich gas.

[0005] The use of pulses makes it possible to generate a plasma with an equivalent density of reactive species while reducing heating compared to non-pulsed plasma. The energy efficiency of this method is improved.

[0006] When these methods use plasma discharge in a high-speed gas flow, the gas residence time can be comparable to or shorter than the characteristic ionization time. In this case, no chemical reaction may occur and the plasma may not ignite.

[0007] Active systems are already known to ignite plasma, which makes it possible to increase the electric field beyond the destructive value. These active systems can utilize increasing the voltage applied to the electrodes, decreasing the gas pressure, increasing the gas temperature, or decreasing the distance between electrodes by a movable mechanical system.

[0008] The active systems presented above have industrial limitations. They are not suitable for pulsed plasma generation, meaning that their favorable energy efficiency cannot be reap the benefits. In fact, pressure drops and temperature increases require process interruptions. Voltage increases require oversized voltage generators (additional costs). The presence of moving parts leads to additional maintenance and sealing costs. Furthermore, feedback systems require sensors, and therefore measuring systems (electrical and optical), and processing circuits for feedback.

[0009] International Publication No. 2013 / 078880 discloses a multi-stage plasma reactor system comprising: (i) a hollow cathode for decomposing carbonaceous materials, each stage comprising a hollow cathode and a hollow anode cooled by recycling a coolant or refrigerant fluid; (ii) one or more working gas inlets; (iii) one or more inlets for carbonaceous material as raw material and a carrier gas; and (iv) reaction tubes connected to the anode or cathode.

[0010] Reference CN 109663555 A discloses a system and method for synergistically converting greenhouse gases and biochar using pulsed jet plasma. A discharge arc formed between an internal electrode and an external electrode is driven by the flow of rising CO2 spiral air, which sequentially passes through a tapered nozzle and an air distribution plate to form multiple uniformly distributed plasma microjets. The microjets drive biochar particles to form gas-solid fluidization reaction regions. [Overview of the project] [Problems that the invention aims to solve]

[0011] The objective of this invention is to propose a method and system for pulsed plasma gas conversion that enables better operational continuity and lower maintenance costs than conventional methods and systems. [Means for solving the problem]

[0012] This objective is achieved by a method for producing gas from a gas mixture, which includes the following steps: The steps include injecting a gas mixture into a pulsed plasma reactor, The steps of dissociating the gas mixture using an isochronous discharge between a first long electrode of a given polarity and one or more other electrodes of opposite polarity facing the first electrode, A step of releasing the generated reactive gases from the dissociation step into an area where they can be cooled and / or separated and / or collected.

[0013] According to the present invention, a first electrode and one or more other electrodes define an inter-electrode gap formed from an ignition region and two other regions, characterized by a variable inter-electrode distance, and the dissociation step includes a step of providing passive re-ignition of the plasma when the plasma generated in the reactor is blown out by a continuous gas flow in the reactor, the passive re-ignition step is performed in an ignition region that is protected from the continuous gas flow and has an inter-electrode distance that allows for the ignition of the plasma protected from the continuous gas flow.

[0014] The reignition technique used in the system / method according to the present invention is passive and therefore reliable.

[0015] It should be noted that this configuration of the dissociation reactor can also be used in plasma-assisted combustion chambers where controlling the reaction region in a highly fluid medium can cause practical problems.

[0016] Passive re-ignition of plasma is advantageous, In the direction of plasma propagation, the distance between electrodes is increased (2), and then decreased (3), as the plasma enters the plasma propagation region at the exit of the ignition region (1). Next, the plasma enters a stable operating region (4) which is arranged to generate an electric field having an inter-electrode distance smaller than the distance within the propagation region. It can further include

[0017] Passage from region (1) to region (2) and then to region (3) is advantageously achieved by using flow induced by a discharge that generates a shock wave called an isochronous discharge. This shock wave is passively generated by the isochronous discharge.

[0018] Another problem solved by the gas conversion method according to the present invention is the need to control the gas flow in the plasma reactor.

[0019] The gas inflow (overall flow) is transformed by passing through the reaction region (the reaction converts the incoming materials into products), generating its own flow (induced flow). If the reaction products are convected upstream of the overall flow, they may be transformed again in the reaction region, reducing energy efficiency.

[0020] These isochronous discharges generated during the dissociation step between a first electrode of a given polarity and the other electrode of the opposite polarity generate asymmetric shock waves that contribute to controlling the direction of the flow of reactive gas in the plasma discharge.

[0021] In a preferred embodiment of the present invention, the shock wave is obtained by a repetitive pulsed nanosecond discharge generated between a first electrode of a given polarity and another electrode of the opposite or neutral polarity.

[0022] The directional control may favorably include increasing the reduced electric field in one of the two electrodes.

[0023] To generate a reduced electric field asymmetry, heating included in one of the electrodes may also be provided.

[0024] Shock waves and associated hydrodynamic expansions caused by pulsed discharges have been the subject of several scientific studies [1][2][3]. The novelty of the method according to the present invention lies in the stability of the resulting flow control.

[0025] Note that plasma ignition is driven by the reduced electric field E / N, where E is the electric field and N is the number of molecules per unit volume. E / N is expressed in Townsend (1 Td = 10 -17 V·cm 2 ).

[0026] The hydrodynamics generated by shock waves can take two forms: Diffusion regime Non-diffusion regime with the presence of the release of hot gas generated by the discharge.

[0027] In the present invention, the regime must be non-diffusive. The theory of Dumitrache [5] provides a criterion for achieving a non-diffusive regime that depends on the dimensionless number π:

[0028]

Equation

[0029] In the formula, E is the energy deposited in thermal form in the plasma, d is the electrode distance, R is the radius of the discharge, and P is the gas pressure.

[0030] In a non-diffusive regime, the discharge generates shock waves that can be modeled as a cylindrical shock wave centered on the inter-electrode axis and two spherical shock waves substantially centered in front of each electrode. In an axisymmetric initial state, the spherical shock waves diffuse at the same velocity, and the hot gas is emitted along the torus. In an asymmetric initial state, one of the two shock waves is faster, and the hot gas is emitted on the side of the faster shock wave.

[0031] The propagation speed of a shock wave is proportional to the pressure gradient. In isochronous discharge (energy deposition << hydrodynamic time), the pressure gradient is proportional to the temperature gradient at the end of the discharge. In isochronous discharge, the temperature rise is due to the pre-dissociation of the excited electronic state (ultrafast heating).

[0032] The excitation of electronic states increases with the decurrent field E / N. Therefore, if one of the two electrodes is initially hotter, the decurrent field becomes higher. As a result, excitation, and consequently predissociation, increases. Consequently, the temperature during discharge increases, and therefore the pressure increases, and therefore the shock wave becomes faster at this electrode. As a result, the hot gas is expelled from the side of the hot electrode. The electrode remains hot and is therefore stable.

[0033] In certain exemplary embodiments of the present invention, heating of one of the electrodes is directly generated by ion bombardment to the electrode and by reduction of thermal diffusion. Heating of one of the two electrodes can be increased by selecting a material having a low thermal diffusivity for this electrode.

[0034] To understand the mechanism that controls the flow induced by a single nanosecond discharge, which is generated between a pair of electrodes and leads to the formation of two observed hydrodynamic regimes, it may be useful to refer to reference [6].

[0035] To understand the effects of gas flow recirculation on the temporal development of species and gas temperature near the discharge region that generates shock waves, it is useful to refer to reference [7].

[0036] For numerical studies of the fluid dynamics induced by the plasma generated by two laser pulses for ignition of a flammable mixture, it may be useful to refer to reference [8].

[0037] In this method, the geometric shape and thermophysical properties of the electrodes are controlled to generate an induced flow, which is then convectively guided away from the reaction region and downstream of the overall flow.

[0038] A novel approach is also proposed for generating a voltage signal applied to the electrodes of a plasma reactor using the gas conversion method according to the present invention.

[0039] In fact, plasmas are known to be characterized by the decurrent field (E / N) (Townsends: Td) applied during discharge. Different types of plasmas (microwave, nanosecond, DBD, etc.) correspond to different ranges of decurrent fields. Each temperature range of the decurrent field corresponds to different excitation modes of molecules.

[0040] The dissociation of molecules (CO2, hydrocarbons) by plasma requires both the generation of electrons of sufficient density and the excitation of these electrons at the vibrational energy of the molecules.

[0041] Electron generation is achieved through ionization in a strong electric field (>130 Td). Molecular vibrations are obtained in an intermediate electric field (50-100 Td).

[0042] The objective is to efficiently combine different signals to obtain strong ionization and subsequent molecular vibrations by combining an electric pulse with a reduced electric field exceeding 130 Td with a subsequent electric pulse with an intermediate electric field (50-100 Td).

[0043] Furthermore, the dissociation step may further include generating a high-voltage signal to control the repetitive discharge by combining a short-duration ultra-high-voltage signal for ionizing the gas with a medium-duration high-voltage signal for exciting the molecules to excited vibrational levels.

[0044] According to another aspect of the present invention, a system for converting a gas mixture using a manufacturing method according to the present invention, A pulsed plasma reactor, Means for injecting a gas mixture into the pulsed plasma reactor, A dissociation step comprising: a pulsed plasma reactor receiving the inflow of gas at an inlet; a first long electrode of a given polarity; and one or more other electrodes of opposite polarity facing the first electrode, wherein the first electrode and the one or more other electrodes are arranged to (i) define an inter-electrode gap characterized by a variable inter-electrode distance, and (ii) provide the flow of the gas to an isochronous discharge to generate a reactive gas; An interface for releasing the reactive gas into a region where the reactive gas can be cooled and / or separated and / or collected, Includes, A system is proposed in which the pulsed plasma reactor includes a region protected from gas flow, a so-called ignition region, and when plasma is ejected by a continuous gas flow within the plasma reactor, the distance between the electrodes in the ignition region allows for passive re-ignition of the plasma.

[0045] The pulsed plasma reactor according to the present invention is advantageous in that, In the direction of plasma propagation, there is a region known as the propagation region, where the distance between electrodes is increased and then decreased. A region within the propagation region where the distance between electrodes is less than the distance, known as a stable operating region, which is arranged to generate an electric field, It is equipped with.

[0046] The isochronous discharge generated between a first electrode of a given polarity and another electrode of the opposite polarity generates a shock wave that contributes to controlling the direction of the reactive gas.

[0047] The first electrode may, advantageously, have a point effect, positioned to generate a decurrent in the stable operating region that is greater than that generated in the ignition region or propagation region.

[0048] The stable operating region may be substantially parallel to the direction of gas flow or substantially transverse to the direction of gas flow.

[0049] In this transverse configuration, if a horizontally positioned reactor is considered, the gas flow may be perpendicular to a substantially horizontal plane through the electrodes, or perpendicular to a substantially vertical plane through the electrodes.

[0050] In a preferred configuration of the present invention, the conversion system may further include means for controlling the direction of flow of reactive gas in the plasma discharge, wherein the means for controlling the direction includes means for increasing the de-energy field at one of the two electrodes.

[0051] Means for increasing the desaturation field can include a heating mechanism included in one of a point-effect electrode and / or a plurality of electrodes.

[0052] The conversion system according to the present invention may further include means for generating a high-voltage signal exceeding 10 kV to control repetitive discharge by combining a short-duration ultra-high-voltage signal exceeding 130 Td for less than 20 ns to ionize the gas and a long-duration high-voltage signal of 50-100 Td for less than 1 s to excite molecules to excited vibrational levels.

[0053] A further aspect of the present invention proposes the use of a system according to the present invention for producing a mixture of hydrocarbons and CO2 or gaseous dihydrogen from hydrocarbons, comprising: injecting the mixture of hydrocarbons and CO2 or hydrocarbons at the inlet of a pulsed plasma reactor; and collecting the gaseous dihydrogen at the outlet of the pulsed plasma reactor.

[0054] Isochronous discharges can, advantageously, include nanosecond repetitive pulse (NRP) discharges.

[0055] The interface for releasing reactive gases is, A step for rapidly cooling the reactive gas, A step for separating the gaseous dihydrogen and carbon monoxide produced after cooling the reactive gas, Includes.

[0056] A further aspect of the present invention proposes the use of a system of the apparatus according to the present invention for generating oxygen from carbon dioxide, the system comprising injecting carbon dioxide at the inlet of a pulsed plasma reactor and collecting oxygen at the outlet of the pulsed plasma reactor.

[0057] The present invention will be better understood in light of the description shown in the following drawings. [Brief explanation of the drawing]

[0058] [Figure 1] This is an overview of the dihydrogen production system according to the present invention. [Figure 2] This is a cross-sectional view of an exemplary embodiment of the dihydrogen production system according to the present invention. [Figure 3] A larger version of Figure 2, showing the main components of the system. [Figure 4] This is a partial cross-sectional view of an exemplary embodiment of the dissociation stage in the dihydrogen production system according to the present invention. [Figure 5A] This is a partial cross-sectional view of the first configuration of the dissociation stage, where the stable region traverses the gas flow. [Figure 5B] This is a partial cross-sectional view of the second configuration of the dissociation stage, where the stable region traverses the gas flow. [Figure 6] This shows the various locations of the ignition, propagation, and stabilization regions within the dissociation phase. [Figure 7] This is an enlarged cross-sectional view of the dissociation stage, representing the distance between characteristic electrodes. [Figure 8] Three examples of characteristic profiles that provide variation in the inter-electrode distance within the dissociation phase are shown. [Figure 9] This diagram schematically illustrates the phenomenon of reinjecting high-temperature gas into the plasma within the reactor. [Figure 10] This is a partial cross-sectional view of the dissociation stage, configured to avoid this reinjection phenomenon. [Figure 11] Three exemplary embodiments of axial electrodes adapted to avoid this re-injection phenomenon are shown. [Figure 12] This is an overview of an apparatus for generating a mixed signal to be supplied to the electrodes of a dihydrogen production system according to the present invention. [Figure 13] Figure 12 is an electrical diagram of a practical exemplary embodiment of the generating apparatus. [Modes for carrying out the invention]

[0059] The dihydrogen production system S according to the present invention, as shown in Figures 1 and 2, includes a dissociation step DI which receives a gas stream such as a mixture of methane CH4 and carbon dioxide CO2 at the inlet, an ultra-rapid cooling step FQ ("rapid cooling") which follows a separation step SE which separates dihydrogen gas H2 from carbon monoxide gas CO.

[0060] As a practical example, the gas flow processed by this manufacturing system is approximately 0.2 m³. 3 It can be liters / hour or approximately 3.5 liters / minute.

[0061] For gaseous input CO2:CH4, we can provide stoichiometric ratios of 50:50 to 30:70 corresponding to biogas-type mixtures, and 0:100 for pure methane.

[0062] Referring to Figure 3, a practical exemplary embodiment of the dihydrogen gas generation system according to the present invention is described below.

[0063] The dissociation stage 10 comprises a cylindrical structure 12 made of stainless steel / aluminum alloy, which defines a first chamber 20 having an inlet 21 for gas inflow (CH4, CO2) and including a first electrode 13 acting as an anode opposite a second electrode 15 which acts as a cathode located in the center of an opening 26 at the outlet of the first chamber 20. This cathode can be made from tungsten. The dissociation stage 10 also comprises a connector 11 including a supply cable for the electrode 13. The structure 12 includes an insulating block 14 configured to avoid the generation of an electric arc due to the high voltage supply to the electrode 13.

[0064] The outlet opening 26 allows the dissociated gas to enter the cooling region FQ, which is formed from a second chamber 27 defined by a structure 23 having a cylindrical outer shape and a conical inner shape that continuously increases the inner diameter of the flow from the opening 26 to the outlet of the cooling region FQ.

[0065] Referring to Figures 2 and 3, the third stage SE of the dihydrogen gas generation system 1 comprises a cylindrical structure 24 mechanically coupled to the outlet of the cooling stage FQ, and a radial discharge duct 22. A separation chamber 19 within the structure 24 is axially intersected by an electrical supply rod 25 having electrodes 15 at its end that extend into a dissociation chamber 20.

[0066] Next, an example of the dissociation stage of the dihydrogen gas production system according to the present invention will be described with reference to Figures 4 to 8.

[0067] This dissociation stage 40 comprises an anode 13 having a tapered, pointed shape at its end, and a cathode 15 facing the anode 13, having a substantially rounded end, and electrically connected to the inner wall of the dissociation chamber.

[0068] Referring to Figures 4 and 6, within the dissociation phase, three characteristic regions can be identified: the so-called ignition region 1, AMO, corresponding to the minimum inter-electrode distance; the propagation initiation region 2, immediately after plasma ignition, where the inter-electrode distance increases in the direction of plasma propagation; and the propagation region 3, PRO, where the inter-electrode distance decreases, followed by the stable region 4, STA, located between the tip of the anode 13 and the end of the cathode 15.

[0069] The insulating block 14 located upstream of the ignition region 1 has two functions: it prevents the generation of an electric arc, and it forms this region 1 protected from the continuous gas flow 5 in which ignition takes place.

[0070] As shown in Figure 7, the distance between electrodes is variable, increasing from a minimum value d1 in the ignition region 1 to a value d4 in the stable region 4 between the tip of electrode 13 and the end of electrode 15, and then decreasing.

[0071] Next, with reference to Figures 5A and 5B, two configurations of the dissociation stage of the gas conversion system according to the present invention, in which the gas flow traverses the electrode arrangement, will be described.

[0072] In a first specific configuration of the dissociation stage 50A of a horizontally arranged reactor, as shown by Figure 5A where a dashed line defines the flow region, the gas flow 55A flows perpendicular to the horizontal plane of electrode arrays 53, 57. The ignition region 1 is located outside the flow of flow 55A and is therefore protected from this gas flow. During the discharge in region 1, each spark can cause the induced flow to oscillate either left or right. Since the pulse frequency is high (approximately 1000 pulses per second), it is sufficient to wait for a spark that allows the flow to the right (towards electrode arrays 53, 57) for proper ignition to occur. A small flow bypass can also be provided to drive the plasma toward electrode arrays 53, 57. This induced flow allows the plasma to be positioned in the propagation initiation region 2 within flow 55A, and the plasma then slowly moves across the propagation region 3 to the stabilization region 4.

[0073] In a second specific configuration of the dissociation stage 50B of the horizontally arranged reactor shown in Figure 5B, the gas flow 55B flows perpendicular to the vertical plane of the electrode arrays 53, 57.

[0074] As shown in Figure 8, several profiles of the propagation region can be considered. The efficiency of the profile depends on the ratio d1 / d4, which is selected depending on the frequency and temperature, and a number π (related to the non-diffusive region).

[0075] Using Figures 9 to 11, an embodiment of the dihydrogen gas generation system according to the present invention, which can solve the problem of reinjecting the generated gas into the plasma, will be described, as schematically shown in Figure 9.

[0076] Therefore, in order to control the gas flow in the reactor, the gas generation system according to the present invention is As shown in Figure 10, there are two electrodes 13 and 15 facing each other, which define an inter-electrode region where an electric field is generated between the two electrodes in order to generate a plasma discharge that generates a shock wave (hereinafter referred to as an isochronous discharge), Using a point-effect electrode, a reaction region is created in which a high decurrent field is promoted in one of the two electrodes due to a temperature increase caused by the heating mechanism included in electrode 13 and by reducing the cooling mechanism around the electrode, Includes.

[0077] Shock waves are passively generated by isochronous discharges.

[0078] Next, possible geometric profiles for ignition, propagation, and stabilization regions within the pulsed plasma reactor of the gas mixture conversion system according to the present invention will be described.

[0079] First, it is important to note that an ideal one-dimensional (1D) propagation pattern is a linear profile that forms an angle α with respect to the propagation direction, and that the ideal angle α depends on the pulse frequency and the temperature reached. However, the ignition at the start must act as a point effect, while stabilization at the end of the process requires reducing the gap between electrodes.

[0080] Therefore, the ideal theoretical profile [ignition + propagation + stabilization] is a combination of a point and two dashed lines. Consequently, the theoretical profile is difficult to machine in practice, and profiles using the same tangents as this ideal profile have been used.

[0081] In this regard, three cathode shapes designed to provide flow control are shown in Figure 11, and are intended to satisfy the following conditions: not obstruct the direction of flow, providing replaceable cathode parts, and being easily machinable.

[0082] In the first geometric shape (11.1), the cathode 15.1 has the form of a point at the end of the rod 25. In the second geometric shape (11.2), the cathode 15.2 has the formation of a perforated disk located in the smaller diameter portion of the rapid cooling region. In the second geometric shape (11.3), the cathode 15.3 has a complex shape extending from the ignition region to the stabilization region. These cathodes 15.2 or 15.3 can be fabricated from tungsten material using an additional prototyping machine.

[0083] In a preferred operating mode, the pulsed plasma that generates the shock wave is generated by nanosecond repeating pulse (NRP) pulses having a voltage of 10 kV and a repeat frequency in the range of 5 to 500 kHz, preferably 10 to 100 kHz.

[0084] Next, with reference to Figures 12 and 13, exemplary embodiments of a system for generating a voltage signal applied to a plasma reactor electrode in a gas generation system according to the present invention will be described. The voltage signal is generated from a combination of variable-shape high-voltage signals for generating a plasma discharge to excite different energy modes of molecules in order to achieve a desired chemical effect.

[0085] The signal generation system 30 combines a short pulse, a short-duration (0-20 ns) ultra-high voltage signal (>130 Td) for ionizing the gas, and a long pulse, a long-duration (0-1 s) high voltage signal (50-100 Td) for exciting molecules to the vibrational level. The long pulse is generated by the long pulse generator module 31, and the short pulse is generated by the NRP module 32. The two signals are combined with the mixing module 33.

[0086] The generation system 30 is A DC module 31 that generates high-voltage pulses with a duration of 0 to 1 second (hereinafter referred to as long pulses) and has impedance adaptation, A high-voltage pulse with a duration of 0-20ns (hereinafter referred to as a short pulse) is generated, and an impedance-adaptive NRP module 32 is used. Module 33 for mixing short and long pulses, A voltage probe 34 provides information about the signal actually applied to the electrodes of the reactor 10, Includes.

[0087] The long pulse generator module 31 is provided with protection implemented by a first-order low-pass filter, while the short pulse generator module 32 is provided with protection implemented by a second-order high-pass filter.

[0088] The short pulse generator module 32 provides a decurrent field of >100Td and a duration of 0-20ns, while the long pulse generator module 31 provides a decurrent field of 50-100Td and a duration of 0-1s.

[0089] The signal generation system 30 is configured such that the de-energizing field for long pulses falls below the ionization threshold. The plasma is in a subcritical regime.

[0090] The dynamic calculations yield the following: Optimal E / N field: 50 Td or 4 kV / cm at 900 K, 3 kV / cm at 1200 K; Applicable range: Voltage [1-4kV] and [0.5-30A].

[0091] In the first embodiment, the long pulse generator 31 is a DC (direct current) generator with a voltage of 3kV and a maximum current of 1A, and the short pulse generator 32 is a high-voltage NRP (non-reactive pulse) generator with a voltage of 10kV. The NRP circuit is protected from DC, and the DC circuit is protected from NRP.

[0092] In another embodiment, the short pulse generator 32 is a 10 ns nanosecond pulse generator, and the long pulse generator 31 is a 1 μs pulse generator.

[0093] The present invention is not limited to the exemplary embodiments described, and many other embodiments can be considered without departing from the scope of the invention. In particular, the reignition techniques described in the present invention can also be used in plasma-assisted combustion devices or scramjets (supersonic combustion ramjets).

[0094] [Literature] [1] “Experimental study of the hydrodynamic expansion following a nanosecond repetitively pulsed discharge in air” (2011) Da A. Xu, Deanna A. Lacoste, Diane L. Rusterholtz, Paul-Quentin Elias, Gabi D. Stancu, and Christophe O. Laux. [2] ”Simulation of the hydrodynamic expansion following a nanosecond pulsed spark discharge in air at atmospheric pressure” (2013) Fabien Tholin and Anne Bourdon. [3] Hydrodynamic Regimes Induced by Nanosecond Pulsed Discharges in Air: Mechanism of Vorticity Generation, (2019) Ciprian Dumitrache 1, Arnaud Gallant, Nicolas Minesi, Sergey Stepanyan, Gabi D Stancu and Christophe O Laux. [4] Dumitrache, C.; Yalin, A.P. Numerical Modeling of the Hydrodynamics Induced by Dual-Pulse Plasma; In 2018 AIAA Aerospace Sciences Meeting; American Institute of Aeronautics and Astronautics: Reston, Virginia, 2018, 10.2514 / 6.2018-0689. [5] Dumitrache, C.; Galant, A.; Minesi, N.; Stepanyan, S.; Stancu, G.-D.; Laux, C.O. Hydrodynamic regimes in NRP discharges (in preparation). Journal of Physics D: Applied Physics 2019. [6] Two Regime Cooling in Flow Induced by a Spark Discharge. Bhavini Singh, Lalit K. Rajendran, Pavlos P. Vlachos, and Sally P. M. Bane. Phys. Rev. Fluids 5, 014501 - Published 14 January 2020. [7] A 3-D DNS and experimental study of the effect of the recirculating flow pattern inside a reactive kernel produced by nanosecond plasma discharges in a methane-air mixture Maria Castela, Sergey Stepanyan (2017). [8] Numerical Modeling of the Hydrodynamics Induced by Dual-Pulse Laser Plasma, Ciprian Dumitrache, Azer Yalin (2018). [9] Mao et al 2018, “Numerical modeling of ignition enhancement of CH4 / O2 / He mixtures using a hybrid repetitive nanosecond and DC discharge,” doi / 10.1016 / j.proci.2018.05.106.

Claims

1. A method for producing a gas from the dissociation of a gas mixture of hydrocarbons and carbon dioxide, A step of injecting the gas mixture into a pulsed plasma reactor (10) which includes a structure (12) defining a dissociation chamber (20) including a first electrode (13) and one or more other electrodes (15) of opposite polarity facing the first electrode (13), wherein the first electrode (13) and the one or more other electrodes (15) define an inter-electrode region in which an electric field is generated between the two electrodes to generate an isococcal plasma discharge; The steps include: dissociating the gas mixture using the isococcal plasma discharge inside the dissociation chamber (20); The steps include releasing the reactive gases generated from the dissociation step into a region where they can be cooled and / or separated and / or collected, Includes, The first electrode (13) has a tapered, pointed shape. The first electrode (13) and the one or more other electrodes (15) further define the inter-electrode gap formed from the ignition region (1) characterized by a variable inter-electrode distance, The dissociation step is a step of providing passive reignition of the plasma when the plasma generated in the reactor (10) is blown out by the continuous flow of the gas mixture entering the reactor (10), Includes, The passive re-ignition step is performed within the ignition region (1, AMO), which is a region protected from the continuous flow of the gas mixture (5). The method is characterized in that the protected region arises from the arrangement of insulating blocks (14) within the structure (12) and has a variable electrode distance that allows for the re-ignition of the plasma protected from the continuous flow of the gas mixture (5).

2. The one or more other electrodes include a second electrode (15), Furthermore, the passive re-ignition step of the plasma is, In the direction of plasma propagation, the distance between the second electrode (15) and the first electrode (13) connected to the structure (12) is increased (2), then decreased (3), as the plasma enters the plasma propagation region (2, 3, PRO) at the exit of the ignition region (1, AMO), Next, the inter-electrode distance (d) within the propagation region (PRO) is smaller than the distance mentioned above. ４ The plasma enters a stable operating region (4, STA) which is arranged to generate an electric field having the following characteristics: The method according to claim 1, characterized by including

3. Furthermore, the method according to claim 1, characterized in that the dissociation step includes a plasma discharge between the first electrode and the second electrode to generate an asymmetric shock wave.

4. Furthermore, the method according to claim 3, characterized in that the intensity of the de-energy field E / N is increased at one of the two electrodes (13, 15), where E is the electric field and N is the number of molecules per unit volume.

5. The method according to claim 4, further characterized by including heating one of the electrodes (13, 15).

6. The method according to any one of claims 1 to 5, further comprising the step of generating a high voltage signal exceeding 10 kV for controlling repetitive discharge by combining a short-time ultra-high voltage signal exceeding 130 Td for less than 20 ns to ionize the gas and a long-time high voltage signal of 50 to 100 Td for less than 1 s to excite the molecules to an excited vibrational level.

7. A system (S) for converting a gas mixture of hydrocarbons and carbon dioxide using a manufacturing method described in any one of claims 1 to 6, A pulsed plasma reactor (10) includes a structure (12) that defines a chamber including a first electrode (13) and one or more other electrodes (15) of opposite polarity facing the first electrode (13), Means (21) for injecting the gas mixture into the pulsed plasma reactor (10) so as to provide a continuous inflow of gas into the pulsed plasma reactor, A dissociation stage (DI) comprising: a pulsed plasma reactor receiving the inflow of gas at an inlet; a first electrode (13) of a given polarity; and one or more other electrodes (15) of opposite polarity facing the first electrode, wherein the first electrode (13) and the one or more other electrodes are arranged to (i) define an inter-electrode gap characterized by a variable inter-electrode distance, and (ii) provide the flow of the gas to an isococcal plasma discharge to generate a reactive gas; An interface for releasing the reactive gas into a region where the reactive gas can be cooled and / or separated and / or collected, Includes, Furthermore, the structure (12) includes an insulating block (14) that generates a region protected from gas flow, a so-called ignition region (1), and when the plasma is blown out by the continuous flow of the gas mixture entering the plasma reactor (10), the variable electrode distance (d) in the ignition region is controlled. １ A system characterized in that it enables passive re-ignition of the plasma.

8. The one or more other electrodes include a second electrode (15), The pulsed plasma reactor (10) further comprises: A region known as a propagation region (2,3) is formed in the direction of plasma propagation, where the distance (2) between the structure (12) connected to the first electrode (13) and the second electrode (15) is increased, and then the distance (3) is decreased. An electrode-to-electrode distance (d) less than the distance within the propagation region, known as a stable operating region (4), which is arranged to generate an electric field. ４ ) and the area of, The system (S) according to claim 7, characterized by comprising:

9. The system (S) according to any one of claims 7 to 8, further comprising means for controlling the direction of flow of the reactive gas, wherein the means for controlling the direction comprises means for increasing the de-energy field E / N at one of the two electrodes, where E is the electric field and N is the number of molecules per unit volume.

10. The system (S) according to claim 9, characterized in that the means for increasing the de-energy field uses an advanced effect electrode.

11. The system (S) according to claim 9 or 10, characterized in that the means for increasing the de-energy field is a heating mechanism included in one of the electrodes.

12. The system (S) according to any one of claims 7 to 11, further comprising means for generating a high voltage signal exceeding 10 kV for controlling repetitive discharge by combining a short-time ultra-high voltage signal exceeding 130 Td for less than 20 ns for ionizing a gas and a long-time high voltage signal of 50 to 100 Td for less than 1 s for exciting molecules to an excited vibrational level.

13. A system (S) according to any one of claims 7 to 12, used for producing a mixture of hydrocarbons and CO2 or gaseous dihydrogen from hydrocarbons, comprising: injecting the mixture of hydrocarbons and CO2 or hydrocarbons at the inlet of the pulsed plasma reactor; and collecting the gaseous dihydrogen at the outlet of the pulsed plasma reactor.

14. The system according to any one of claims 7 to 13, characterized in that the isococcal plasma discharge includes nanosecond repetitive pulse (NRP) discharge.

15. The interface for releasing the reactive gas is: A step (FQ) for rapid cooling of the reactive gas, A step (SE) for separating gaseous dihydrogen and carbon monoxide generated after cooling the reactive gas, The system (S) according to claim 13 or 14, characterized by including the following:

16. Use of the system according to any one of claims 7 to 12 for generating oxygen from carbon dioxide, characterized by comprising injecting carbon dioxide at the inlet of the pulsed plasma reactor and collecting oxygen at the outlet of the pulsed plasma reactor.

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