Apparatus for the pyrolysis of saturated hydrocarbons using an electron beam plasma and method for generating hydrogen

Abstract

A device (10) for the pyrolysis of gaseous saturated hydrocarbons by means of an electron beam plasma for hydrogen production comprises a feed line (30) for supplying a reactant gas mixture, a reaction device (12) fluidically connected to the feed line (30), and a filter device (32) arranged downstream of the reaction device (12) and fluidically connected to the reaction device (12). The reactant gas mixture comprises a gaseous saturated hydrocarbon. The reaction device (12) has a reaction chamber (14) and is configured to at least partially convert the reactant gas mixture in the reaction chamber (14) in an electron beam plasma generated by an electron beam to a reaction mixture containing hydrogen and carbon dispersed in the reaction mixture.The filter assembly (32) includes a cyclone separator (34) for separating the dispersed carbon while obtaining a hydrogen-containing product stream. Furthermore, a method for generating hydrogen is described.

Description

[0001] The invention relates to a device for the pyrolysis of gaseous saturated hydrocarbons by means of an electron beam plasma and to a method for producing hydrogen using such a device.

[0002] Hydrogen as an energy carrier is a promising alternative to energy sources from fossil fuels, particularly for avoiding climate-damaging gases such as carbon dioxide (CO2). Hydrogen has the advantage in this regard that it can be used as an energy storage medium to offset fluctuating solar and / or wind-based energy generation, as well as in mobile applications, and that hydrogen combustion can be carried out without producing greenhouse gases.

[0003] However, the method of hydrogen production, which should also be carried out with as little emissions as possible, is crucial for the overall climate impact of hydrogen as an energy carrier. Key processes considered for hydrogen production in the context of future energy systems include water electrolysis, reforming processes with subsequent CO2 capture, and methane pyrolysis.

[0004] In water electrolysis, water is split into hydrogen and oxygen in an electrolyzer by applying an electrical voltage. The advantage of water electrolysis is that no carbon dioxide is produced. However, splitting the water requires a large amount of electrical energy, which in industrial implementation can be even greater than what can be recovered from the conversion of the produced hydrogen. Thus, water electrolysis is primarily advantageous when excess energy is available from renewable energy sources.

[0005] Steam reforming refers to the conversion of fossil fuels such as natural gas, coal or oil into methane by adding steam at temperatures of approximately 450 to 500 °C and a pressure of approximately 25 to 30 bar.

[0006] The methane is then reacted with water at constant pressure and a temperature of approximately 800 to 900 °C to form hydrogen and carbon monoxide. The carbon monoxide is ultimately converted to carbon dioxide, which must then be released into the atmosphere or captured and stored in additional process steps, for example, using CCS (carbon capture and storage) technology. Although the process requires less energy than water electrolysis, it is either not climate-neutral or only possible with considerable effort due to the carbon dioxide formation and the subsequent required carbon dioxide storage.

[0007] In methane pyrolysis, methane is thermally split into carbon and hydrogen at very high temperatures of approximately 900 to 1400 °C. Methane pyrolysis can be carried out non-catalytically, catalytically, or thermally. All of these variants have in common that the processes are highly complex due to carbon deposits, very high process temperatures, or a lack of modulation, and are difficult to integrate into an energy system.

[0008] In Kerscher F. et al., "Low-carbon hydrogen production via electron beam plasma methane pyrolysis: Techno-economic analysis and carbon footprint assessment" (International Journal of Hydrogen Energy, doi: 10.1016 / j.ijhydene.2021.03.114), an alternative process is proposed in which methane is split at high temperatures in a non-thermal plasma generated by an electron beam instead of thermally. The energy of the electron beam is used to excite a plasma in which the splitting occurs, primarily the kinetic energy of the electron beam. Due to the low binding forces of the methane molecule, a high hydrogen yield per unit of electrical energy is achieved with less energy input compared to water-based methods, without producing carbon dioxide as a byproduct.However, it has been shown that despite the fundamentally more efficient process, the resulting reaction mixture of hydrogen and carbon does not produce hydrogen that is sufficiently pure for technical applications.

[0009] The object of the invention is to provide a device and a method for hydrogen production which makes it possible to produce hydrogen in a way that is as climate-neutral as possible, with low energy consumption and at a reasonable cost.

[0010] The object of the invention is achieved by a device for the pyrolysis of gaseous saturated hydrocarbons by means of an electron beam plasma to generate hydrogen, wherein the device comprises a supply line for supplying a reactant gas mixture, a reaction device fluidically connected to the supply line, and a filter device arranged downstream of the reaction device and fluidically connected to the reaction device. The reactant gas mixture comprises a gaseous saturated hydrocarbon. The reaction device has a reaction chamber and is designed to at least partially convert the reactant gas mixture in the reaction chamber in an electron beam plasma generated by an electron beam to form a reaction mixture containing hydrogen and carbon dispersed in the reaction mixture.The filter device comprises a cyclone separator for separating the dispersed carbon to obtain a hydrogen-containing product stream.

[0011] The invention is based on the fundamental idea of ​​reacting gaseous saturated hydrocarbons in an electron beam plasma in a particularly energy-efficient manner to generate the desired hydrogen. A purely thermally induced bond rupture within the gaseous saturated hydrocarbon is not necessary for this. The carbon present in the reaction mixture alongside the hydrogen is separated from the hydrogen by a cyclone separator in a particularly simple, reliable manner and without additional energy expenditure. This results in a hydrogen-containing product stream that is already essentially purified from other reaction products arising during production.

[0012] Furthermore, it was discovered that the carbon produced in the electron beam plasma is carbon species, which in turn represent a valuable reaction product and can be used in an economically viable form, for example, as industrial carbon black. This makes the device according to the invention particularly cost-effective, since not only the resulting hydrogen but also the carbon byproduct can be economically utilized. Purification using the cyclone separator also makes this product available in a simple and cost-effective manner.

[0013] The carbon obtainable by means of the device comprises in particular carbon black, also known as industrial soot, or consists of carbon black.

[0014] Furthermore, no carbon dioxide, or at least no significant amounts of carbon dioxide, are produced during operation of the device, which enables hydrogen production that is as climate-friendly as possible.

[0015] Preferably, the reactant gas mixture is converted into the reaction mixture in the reaction chamber as completely as possible, excluding unavoidable reaction losses or unavoidable reaction losses due to unavoidable reaction equilibria. The most complete conversion possible here is understood to mean the maximum expected yield. The maximum expected yield for a single pass of the reactant gas mixture through the reaction chamber is in particular up to 70%, for example up to 65%.

[0016] The cyclone separator is preferably a high-performance cyclone separator. Compared to conventional cyclone separators, high-performance cyclone separators are characterized in particular by improved separation efficiency of gases and particles contained in the reaction mixture. This can be achieved by various modifications of the high-performance cyclone separator compared to conventional cyclone separators. These modifications can be realized by an extended separation chamber, a conically shaped separation chamber, a geometric constriction at the inlet of the high-performance cyclone separator, and / or by flow-guiding elements arranged in the flow path of the high-performance cyclone separator, such as vortex breakers, vortex amplifiers, and tangentially arranged inlet nozzles.

[0017] The cyclone separator can be configured to separate carbon species down to a minimum particle size, in particular a minimum particle size of 2.0 µm. In other words, particles in the reaction mixture, in particular carbon particles, with a particle size of less than 2.0 µm remain in the hydrogen-containing product stream, while particles in the reaction mixture with a particle size of 2.0 µm or more can be collected in the cyclone separator and removed therefrom continuously or batchwise.

[0018] The particle size is particularly defined as the mean particle size d 50 defined and can be determined according to ISO 13320-1.

[0019] The gaseous saturated hydrocarbon can be selected from hydrocarbons with a maximum of four carbon atoms and combinations thereof. Saturated hydrocarbons with more than four carbon atoms typically have boiling points that would require excessively energy-intensive heating to obtain a gaseous reactant mixture. Furthermore, with increasing carbon number, the amount of incompletely converted reaction products in the reaction chamber increases, assuming a constant design of the reaction chamber. This can have a detrimental effect on the purity of the product stream—both the purity of the hydrogen-containing product stream and the resulting carbon stream—process control, and the hydrogen and carbon yield.

[0020] The term “gaseous saturated hydrocarbon” here and in the following refers to gaseous alkanes at normal temperature and pressure.

[0021] When reference is made here and below to a plurality of gaseous saturated hydrocarbons, this also includes embodiments in which the reactant gas mixture contains only a single gaseous saturated hydrocarbon, unless otherwise stated.

[0022] The reactant gas mixture can be natural gas, especially natural gas of a commercially available specification. In this case, although the reactant gas mixture originates from a fossil source, the carbon dioxide-free or at least carbon dioxide-reduced conversion to hydrogen minimizes the release of carbon dioxide during operation of the device compared to alternative hydrogen production processes.

[0023] It is also possible for the reactant gas mixture to contain methane from a biogenic source, for example, from the conversion of biomass or agricultural residues. This can further improve the overall carbon dioxide balance during operation of the device.

[0024] In particular, the gaseous saturated hydrocarbon is methane, for example, methane from a biogenic source. In other words, the reactant gas mixture comprises exclusively methane as a gaseous saturated hydrocarbon.

[0025] The reaction device may have an electron beam source separated from the reaction chamber by a separation window that is at least partially transparent to electrons. The separation window is, for example, in the form of a foil or plate.

[0026] To achieve a particularly high electron yield, the separation window is made of a polyaryletherketone, preferably polyetheretherketone (PEEK). Polyaryletherketones, especially PEEK, are thermoplastic, semi-crystalline high-performance plastics with high melting points of more than 300 °C, are resistant to high temperatures, and are flame-retardant. This allows separation windows made of such materials to be exposed to the conditions in the reaction chamber over long operating times of the device without damage. Furthermore, polyaryletherketones are resistant to gamma and beta radiation and exhibit high electron transmittance, particularly compared to conventional separation windows made of titanium foil with a copper grid as a support structure. At the same time, molecules such as carbon dioxide and methane cannot penetrate films and plates made of polyaryletherketones, especially PEEK.This makes it possible to use pressures of atmospheric pressure and above in the reaction chamber without adversely affecting a vacuum surrounding the electron beam source.

[0027] In particular, in the case where a plate or film made of polyaryletherketone, especially PEEK, is used as a separation window, the separation window also has a high resistance to particles present in the reaction chamber.

[0028] Any deposits that form on the separation window during the conversion of the reactant gas mixture to the reaction mixture, for example, in the form of carbon, can be removed by the reactant gas mixture or reaction mixture flowing past the separation window. In this way, the reactant gas mixture also serves as a purge gas. This can increase the service life of the separation window and extend the service life of the device.

[0029] To more precisely influence which parts of the reaction chamber are exposed to the electron beam generated by the electron beam source, the reaction device can have a beam-shaping device for adjusting the electron beam generated by the electron beam source. For example, the beam-shaping device is configured to influence the electron beam via electromagnetic fields, for example, by adjusting the beam shape of the electron beam.

[0030] Since the non-thermal plasma generated in the reaction chamber is generated via the electron beam, the plasma itself can also be influenced in this way, for example, the plasma density in selected areas of the reaction chamber as well as the overall plasma coverage of the reaction chamber. In this way, areas in the reaction chamber where no or only a less efficient conversion of the gaseous saturated hydrocarbons can take place can be minimized or completely avoided.

[0031] A further influence on the plasma can be achieved by modulating the radiation intensity, for example by using a clocked or pulsed beam to advantageously influence the reaction time and thus the reaction temperatures.

[0032] Modulating the radiation intensity can also be used to quench the reaction taking place in the reaction chamber. This allows for particularly precise control of the reaction duration of the reactant gas mixture, as the ongoing reaction can be stopped as quickly as possible. This allows for particularly precise control over the composition of the resulting product stream, especially the available carbon species.

[0033] The reaction chamber can be curved or straight along the flow path of the reactant gas mixture. This allows the arrangement of the electron beam source and the reaction chamber to be particularly well coordinated, thus further improving the conversion yield of the gaseous saturated hydrocarbons.

[0034] The flow pattern describes the course of the reactant gas mixture in the reaction chamber during the conversion to the reaction mixture.

[0035] It is understood that as the reactant gas mixture flows through the reaction chamber, it progressively transforms into a reaction mixture along the flow path due to the progressive conversion of saturated hydrocarbons into the reaction mixture. The flow path of the reactant gas mixture thus corresponds to the path of the reactant gas mixture in the reaction chamber, which is progressively transformed into a reaction mixture. In this sense, the reaction mixture refers to the mixture of compounds obtained at the end of the reaction chamber.

[0036] The electron beam generated by the electron beam source can be tangential, concentric, counter-rotating or perpendicular to the flow path of the reactant gas mixture.

[0037] The electron beam source can be designed to generate axial or band-shaped beams. Depending on the beam shape, the reaction chamber can be designed point-symmetrically around the center of the axial electron beam or axially symmetrically around the central axis of a band-shaped electron beam. The cross-section of the reaction chamber is preferably circular or elliptical for an axial beam shape, and preferably rectangular for a band-shaped electron beam.

[0038] Furthermore, the electron beam can cut the reactant gas mixture once or multiple times.

[0039] The plasma generated in the reaction chamber and thus the conversion rate and yield can be optimized by the orientation of the electron beam relative to the flow path and the frequency with which the electron beam intersects the reactant gas mixture.

[0040] In order to further adapt the flow behavior within the reaction chamber, the reaction chamber can have more than one reaction chamber inlet through which the reactant gas mixture from the supply line can be fed into the reaction chamber.

[0041] For example, the supply line can run via several supply branches, each leading to an associated reaction chamber inlet.

[0042] The supply branches can also run along or in an outer wall of the reaction chamber to heat the reactant gas mixture and to cool the reaction chamber. This provides a heat exchange function, whereby the conversion of the reactant gas mixture is promoted by preheating, while at the same time, the type of carbon species obtained can be influenced by limiting the temperature in the reaction chamber.

[0043] The reaction chamber inlets and / or the feed branches can be rotationally symmetrical or arranged rotationally symmetrically. This allows for a compact design and optimized flow behavior of the reactant gas mixture.

[0044] It is also possible that the reaction chamber inlet(s) are designed as radially circumferential annular slots.

[0045] To regulate the flow rate of the gas stream within the reaction chamber, the reaction chamber can have a varying cross-section along the flow path of the reactant gas mixture. For example, the cross-section of the reaction chamber can increase or decrease along the flow path. The cross-section can increase or decrease stepwise or continuously.

[0046] The change in the cross-section can be adapted, in particular, to the expected conversion rate of the reactant gas mixture within the reaction chamber to the reaction mixture. In this way, a change in the pressure within the reaction chamber can be taken into account in generating the desired flow behavior due to changes in the molar fractions of gaseous components in the reactant gas mixture or the reaction mixture.

[0047] Furthermore, a flow guide element can be arranged in the reaction chamber to influence the flow velocity and / or the flow path of the reactant gas mixture. For example, the flow guide element is a cylinder that extends axially along the reaction chamber.

[0048] It is possible for the flow guide element, in particular the cylinder, to be arranged in the reaction chamber in a non-destructively replaceable manner. In this way, the flow behavior can be exchanged between multiple operating phases of the device, and the flow behavior within the reaction chamber can be adapted by selecting a different flow guide element for the subsequent operating phase.

[0049] The cyclone separator may have an inlet pipe through which the reaction mixture can be transferred into a separation chamber of the cyclone separator. The inlet pipe has a varying cross-section in its axial direction. The varying cross-section of the inlet pipe can increase or decrease, in particular continuously or in stages. The design of the inlet pipe allows the flow velocity of the gas stream into the cyclone separator to be regulated, i.e., the flow velocity at which the reaction mixture generated in the reaction chamber flows into the cyclone separator.

[0050] To further improve the purity of the hydrogen produced in the device, the filter device can comprise at least one filter element arranged downstream of the cyclone separator for separating carbon and / or hydrocarbons contained in the hydrogen-containing product stream. In this sense, the filter device is thus a multi-stage filter device.

[0051] For example, the filter device has a first filter element for separating carbon. Since the hydrogen-containing product stream obtained from the cyclone separator can only contain carbon species with a particle size below a minimum particle size of the cyclone separator, the first filter element is preferably matched to the minimum particle size of the cyclone separator. Thus, the first filter element can be configured to remove particles with a particle size of less than 2.0 µm from the hydrogen-containing product stream.

[0052] In particular, the first filter element is a fine dust filter, for example an electrostatic or cartridge filter.

[0053] The filter device can further comprise a second filter element for separating hydrocarbons from the hydrogen-containing product stream. Such hydrocarbons are generated in particular when the gaseous saturated hydrocarbons used in the reactant gas mixture are not fully converted in the reaction chamber.

[0054] In particular, the second filter element is a gas filter, for example made of ceramic hollow fiber membranes.

[0055] The cyclone separator, in particular, features a rotary valve for collecting the separated carbon. This allows for particularly good control of the cyclone separator's operation. In particular, the carbon collected in the cyclone separator can be further processed in batches.

[0056] The rotary valve is particularly gas-tight to prevent gaseous components in the reaction mixture from leaving the cyclone separator via the rotary valve. This also increases the hydrogen yield of the device, as a larger proportion of the hydrogen produced remains in the hydrogen-containing product stream.

[0057] To further optimize the overall yield of the device, the device can be equipped with a recycle line through which the hydrogen-containing product stream can be at least partially recycled to the reaction chamber. In this way, equilibrium reactions occurring in the reaction chamber can be shifted toward the desired product, hydrogen. Furthermore, the recycled product stream can be used to specifically quench the reaction taking place in the reaction chamber.

[0058] In particular, one or more partial streams of the hydrogen-containing product stream obtained by treatment with the filter element can be recirculated to the reaction chamber via the return line. Thus, any components that may adversely affect the further reaction in the reaction chamber can be removed from the partial stream(s).

[0059] To optimize the energy balance of the device and further increase the reaction rate of the reactant gas mixture in the reaction chamber, the supply line for heating the reactant gas mixture can be in contact with a first heat exchanger device arranged in or on an outer wall of the cyclone separator, or can be part of a first heat exchanger device arranged in or on the outer wall of the cyclone separator. This achieves a particularly compact design, which also minimizes the space required for the device.

[0060] Furthermore, the reaction device can have a second heat exchanger device, which is formed by the supply line and is in heat-transfer communication with an outer wall of the reaction chamber. This also allows for a particularly compact design that both effectively preheats the reactant gas mixture and prevents the temperature within the reaction chamber from rising excessively.

[0061] Furthermore, the filter device can have a third heat exchanger device configured to remove heat from the hydrogen-containing product stream and supply it to the reactant gas mixture. This allows, on the one hand, the hydrogen-containing product stream to be cooled, thereby simplifying downstream processing steps, such as pressure liquefaction, and, on the other hand, the reactant gas mixture to be preheated, which contributes to further improved conversion in the reaction chamber.

[0062] The second heat exchanger device can be in heat-transfer contact with a dip tube of the cyclone separator, one or more of the filter elements, and / or with one or more pipes connecting these components. This provides flexible design options for the device, enabling precise control of the desired temperature profile of the hydrogen-containing product stream within the filter device.

[0063] It is also possible for the second heat exchanger device and / or the third heat exchanger device to be coupled to the first heat exchanger device. In other words, a heat exchanger system can be provided that is configured to distribute the amount of heat handled by the heat exchanger devices within the hydrogen generation device.

[0064] The object of the invention is further achieved by a method for generating hydrogen using a device as described above. In the method, a reactant gas mixture comprising at least one gaseous saturated hydrocarbon is converted by means of an electron beam plasma into a reaction mixture containing hydrogen and carbon dispersed in the reaction mixture. The carbon dispersed in the reaction mixture is separated from the reaction mixture in a cyclone separator of a filter device, and a hydrogen-containing product stream is obtained.

[0065] The features and properties of the device described above apply accordingly to the method according to the invention for producing hydrogen and vice versa.

[0066] The gaseous saturated hydrocarbon can be selected from hydrocarbons with four or fewer carbon atoms and combinations thereof. For example, the gaseous saturated hydrocarbon is methane.

[0067] In one variant, natural gas is used as the reactant gas mixture, in particular natural gas of a commercially available specification.

[0068] According to the invention, the reactant gas mixture is converted into the reaction mixture in the reaction chamber of the reaction device.

[0069] The residence time of the reactant gas mixture in the reaction chamber is preferably 1.0 to 5.0 ms, preferably 2.5 to 3.0 ms. A residence time of less than 1.0 ms can lead to incomplete decomposition of the gaseous saturated hydrocarbons contained in the reactant gas mixture. A residence time of more than 5.0 ms can excessively decrease the energy efficiency of hydrogen production and significantly increase the thermal load on the device.

[0070] Furthermore, it was found that the type of carbon obtained can be influenced by selecting the residence time of the reactant gas mixture in the reaction chamber. In particular, a residence time of the reactant gas mixture in the reaction chamber of 1.0 to 5.0 ms, preferably 2.5 to 3.0 ms, results in carbon species suitable for technical applications, such as carbon black.

[0071] The residence time of the reactant gas mixture in the reaction chamber can be adjusted by adjusting the flow rate of the reactant gas mixture, the flow path of the reactant gas mixture in the reaction chamber, and / or modulating the electron beam plasma. The reaction time can also be limited by a suitable supply of the reactant gas mixture and / or a recirculated product stream.

[0072] The reactant gas mixture can be guided through the reaction chamber in a curved or straight line. In other words, the flow path of the reactant gas mixture within the reaction chamber can be selected so that it is curved or straight.

[0073] The flow behavior within the reaction chamber can be further adjusted by feeding the reactant gas mixture from the feed line into the reaction chamber via more than one reaction chamber inlet, for example by feeding the reactant gas mixture via several feed branches to a reaction chamber inlet each assigned to the respective feed branch.

[0074] The reactant gas mixture can also be preheated, for example, by providing supply branches that run along or in an outer wall of the reaction chamber. This provides an additional heat exchanger function, allowing preheating of the reactant gas mixture and simultaneously being used for targeted cooling of the reaction chamber.

[0075] The hydrogen-containing product stream obtained from the cyclone separator of the filter device can be purified by means of the first filter element to separate carbon, in particular by means of a fine dust filter.

[0076] Additionally or alternatively, the hydrogen-containing product stream can be purified by means of the second filter element to separate hydrocarbons, in particular to remove gaseous saturated hydrocarbons used in the reactant gas mixture from the hydrogen-containing product stream by incomplete conversion.

[0077] To further optimize the overall yield of the process, the hydrogen-containing product stream can be at least partially recirculated to the reaction chamber via the device's return line. In particular, one or more partial streams of the hydrogen-containing product stream are recirculated to the reaction chamber via the return line.

[0078] The carbon collected in the cyclone separator can be collected in a rotary valve of the cyclone separator and removed from the cyclone separator by opening the rotary valve. In particular, the carbon collected in the cyclone separator is removed in batches.

[0079] The reactant gas mixture can be heated by means of the first heat exchanger device, the second heat exchanger device and / or the third heat exchanger device before the reactant gas mixture is transferred into the reaction chamber.

[0080] Further features and characteristics will become apparent from the following description of exemplary embodiments, which are not intended to be limiting, and from the drawings, which show: - Fig. 1 is a schematic representation of a first embodiment of a device for hydrogen production according to the invention, - Fig. 2 to 8 different embodiments of a reaction chamber of the device from Fig. 1, and - Fig. 9 a schematic representation of a second embodiment of the device according to the invention.

[0081] Fig. 1 shows schematically the structure of a device 10 according to the invention for pyrolysis of gaseous saturated hydrocarbons by means of an electron beam plasma.

[0082] The device 10 has a reaction device 12 with a reaction chamber 14 in which a non-thermal plasma can be generated by means of an electron beam source 16, which is also referred to below simply as “electron beam plasma”.

[0083] A non-thermal plasma is understood to be a plasma in which the molecules generating the plasma are not ionized purely thermally, but primarily with the help of the kinetic energy of the electrons generated by the electron beam source 16 and released into the reaction chamber 14.

[0084] The electron beam source 16 is supplied with energy via an energy source 18 in order to provide the power required to produce and maintain the electron beam plasma.

[0085] Suitable electron beam sources 16 are generally known. For example, the electron beam source 16 is a so-called electron beam gun, which comprises a hot cathode or a ribbon emitter as the cathode 20 in a vacuum chamber 22. The cathode 20 is configured to release electrons during operation of the device 10, which are accelerated in an electric field via an anode 24, for example a ring anode. A voltage is applied between the cathode 20 and the anode 24, which voltage is in particular in the range of 10 to 300 kV.

[0086] The accelerated electrons are released into the reaction chamber 14 in the form of an electron beam via a separation window 26 which is at least partially transparent to electrons and there generate a diffuse plasma cloud 28 which generates and maintains the electron beam plasma in the reaction chamber 14.

[0087] The separation window 26 is made in particular of a polyaryletherketone, preferably of polyetheretherketone (PEEK).

[0088] The electrons emitted by the cathode 20 are accelerated via the anode 24 toward the separation window 26. Additionally, a beam-shaping device 25 is provided, which directs the electron beam through electromagnetic fields, in particular focusing it onto the electron beam. It is also possible to realize pulsed operation of the electron beam source 16 using the beam-shaping device 25. This enables particularly precise control of the plasma cloud 28 generated in the reaction chamber 14. In particular, the reaction taking place in the reaction chamber 14 can be terminated very quickly by quenching the plasma cloud 28 in order to prevent the formation of undesirable reaction products.

[0089] The reaction device 12 is supplied with a reactant gas mixture from a storage device (not shown) via a supply line 30.

[0090] The reactant gas mixture contains one or more gaseous saturated hydrocarbons which are Fig. 1 with the general formula C x H 2+2x are shown. Preferably, 1 ≤ x ≤ 4, so that the reactant gas mixture contains saturated hydrocarbons having four or fewer carbon atoms. For example, the reactant gas mixture is a natural gas or a gas mixture obtainable from a biogenic source that includes methane. Of course, it is also possible for the reactant gas mixture to comprise only a single saturated hydrocarbon, in particular methane.

[0091] Downstream of the reaction device 12, the device 10 for hydrogen production has a filter device 32 which comprises a cyclone separator 34.

[0092] The cyclone separator 34 is fluidically connected to the reaction device 12, wherein the reaction mixture produced in the reaction chamber 14 of the reaction device 12 flows via an inlet pipe 36 into a separation chamber 38 of the cyclone separator 34.

[0093] Attached to a lower end 40 of the separation chamber 38 is a gas-tight rotary valve 42 that can be switched between an open position and a closed position. In the closed position, particles collected in the cyclone separator 34, which have an average particle size above a minimum particle size of the cyclone separator 34, accumulate on the rotary valve 42 under the influence of gravity. If the rotary valve 42 is moved to the open position, the collected particles can be removed from the separation chamber 38, thus obtaining a carbon product stream.

[0094] The cyclone separator 34 further comprises a dip tube 46 at an upper end 44 opposite the lower end 40. Gaseous components of the reaction mixture as well as particles of the reaction mixture with an average particle size below the minimum particle size of the cyclone separator 34 can be removed from the separation chamber 38 via the dip tube 46.

[0095] The cyclone separator 34 is in particular a high-performance cyclone separator with a minimum particle size of 2.0 µm.

[0096] In addition to the cyclone separator 34, the filter device 32 in the embodiment shown has further filter elements fluidically connected to the dip tube 46, namely a first filter element 48 for separating particles and a second filter element 50 for separating hydrocarbons, the function of which will be discussed in more detail later.

[0097] The first filter element 48 is, for example, a fine dust filter and the second filter element 50 is a gas filter.

[0098] Downstream of the multi-stage filter device 32, a pump device 52 is arranged, with which a purified hydrogen-containing product stream obtained from the filter device 32 can be discharged from the device 10.

[0099] Furthermore, a first return line 56 and a second return line 58 are provided, with which partial flows from the filter device 32 can be returned to the reaction device 12, specifically the reaction chamber 14.

[0100] The first return line 56 is connected to the second filter element 50 and is configured to return those gaseous components that cannot pass through the second filter element 50 in the direction of the pump device 52 to the reaction device 12.

[0101] The second return line 58 is connected to a valve 60, which is arranged in the flow path between the first filter element 48 and the second filter element 50. The valve 60 can thus be used to control the gas flow within the multi-stage filter device 32 such that the second filter element 50 and / or the second return line 58 is supplied.

[0102] In addition, a further valve 61 is provided, via which the gas flow of the gas mixture fed into the reaction chamber 14 can be controlled. The further valve 61 is fluidly connected to the supply line 30 on the one hand, and to the first return line 56 and the second return line 58 on the other. Accordingly, the valve 61 can be used to control whether only the reactant gas mixture from the supply line 30, only gaseous components returned via the first return line 56 and / or the second return line 58, or a mixture thereof is fed into the reaction chamber 14.

[0103] It is understood that it is also conceivable to dispense with the additional valve 61 and to determine the inflow into the reaction chamber 14 solely via the inflow of reactant gas mixture via the supply line 30. By mixing the streams originating from the different lines, a heat exchange also takes place between the reactant gas mixture and the recirculated gaseous components.

[0104] Furthermore, the device 10 has a first heat exchanger device 62, which is assigned to the cyclone separator 34 and in Fig. 1 is shown only schematically. In the embodiment shown, the first heat exchanger device 62 is formed by the supply line 30, which runs in an outer wall 64 of the cyclone separator 34 to preheat the gas flowing through the supply line 30 using heat released by the reaction mixture present in the separation chamber 38.

[0105] Additionally, a second heat exchanger device 66 is provided, which in the embodiment shown is associated with the reaction device 12. The second heat exchanger device 66 is formed by the supply line 30, which is in heat-transfer communication with an outer wall of the reaction chamber 14, so that the gas flowing through the supply line 30 is further preheated by heat removed from the reaction chamber 14. Furthermore, this ensures that the temperature within the reaction chamber 14 does not rise above a desired maximum temperature.

[0106] In other words, the reaction device 12 itself has an integrated heat exchange function, as in Fig. 1 is indicated.

[0107] The operation of the device 10 for generating hydrogen in an electron beam plasma is described in more detail below.

[0108] First, the supply line 30 is supplied with the reactant gas mixture containing the saturated gaseous hydrocarbon, for example methane.

[0109] When flowing through the supply line 30 in the direction of the reaction device 12, the reactant gas mixture is preheated via the first heat exchanger device 62 and / or the second heat exchanger device 66 and fed to a reaction chamber inlet 68 of the reaction device 12, more precisely the reaction chamber 14.

[0110] In the reaction chamber 14, the reactant gas mixture is ionized into a non-thermal electron beam plasma by the electron beam generated by the electron beam source 16, starting from the diffuse plasma cloud 28. The carbon-hydrogen and, if applicable, carbon-carbon bonds within the saturated hydrocarbon are broken primarily by transferring the kinetic energy of the electron beam to the saturated hydrocarbon. Preheating the reactant gas mixture merely assists this process; a purely thermal breaking of the bonds in the saturated hydrocarbon is not necessary.

[0111] When passing through the reaction chamber 14, the reactant gas mixture is thus converted into a reaction mixture comprising hydrogen (H2) and carbon (C) dispersed in the hydrogen, the carbon being obtained in the form of industrial carbon black.

[0112] The term "dispersed" in this context means that the carbon particles formed are distributed throughout the reaction mixture and entrained by the flow movement. This prevents the carbon from settling within the reaction chamber 14, apart from minor unavoidable impurities.

[0113] The residence time of the reactant gas mixture within the reaction chamber 14 is in particular in the range from 1.0 to 5.0 ms, preferably from 2.5 to 3.0 ms.

[0114] The reaction mixture formed is discharged from the reaction chamber 14 via a reaction chamber outlet 70 and may, in addition to the desired products hydrogen and carbon, also contain hydrocarbons which are Fig. 1 generally with the formula C x H y are specified.

[0115] These hydrocarbons can be formed if the saturated hydrocarbon has not been fully converted in the reaction chamber 14 and are not limited to saturated hydrocarbons. However, the resulting hydrocarbons are also primarily gaseous, as they are the decomposition product of the gaseous hydrocarbons from the reactant gas mixture.

[0116] The reaction mixture is then transferred via the inlet pipe 36 into the cyclone separator 34, more precisely into the separation chamber 38 of the cyclone separator 34.

[0117] The cyclone separator 34, also referred to as a centrifugal force separator, serves as a mass force separator in which the reaction mixture introduced into the separation chamber 38 via the inlet pipe 36 is swirled by its flow velocity and by the limitation via the inner walls of the separation chamber 38.

[0118] Due to the conical shape of the separation chamber 38, whose diameter tapers from the upper end 44 to the lower end 40, the rotational speed of the reaction mixture steadily increases. This causes the particulate carbon from the reaction mixture to be thrown against the inner wall of the separation chamber 38 under the influence of centrifugal forces and trickle down to the closed rotary valve 42.

[0119] The carbon collected on the rotary valve 42 can then be removed from the separation chamber 38 by moving the rotary valve 42 to its open position. Specifically, the carbon is removed from the separation chamber 38 in batches, thus obtaining carbon product batches.

[0120] Gaseous components of the reaction mixture, i.e. essentially hydrogen, as well as carbon with a particle size below the minimum particle size of the cyclone separator 34 are discharged from the separation chamber 38 in the form of a hydrogen-containing product stream via the dip tube 46.

[0121] Any incompletely converted hydrocarbons are also removed as part of the hydrogen-containing product stream from the separation chamber 38 via the dip tube 46.

[0122] The reaction mixture present in the separation chamber 38 can release heat via the first heat exchanger device 62, which is then fed to the reactant gas mixture in the feed line 30. In this way, both the reaction mixture and thus the product streams obtained in the cyclone separator 34 are cooled, and at the same time, the reaction rate in the reaction chamber 14 is increased by the preheated reactant gas mixture.

[0123] It is understood that the cyclone separator 34 can also be designed differently than in Fig. 1, for example as an axial separator instead of the one shown in Fig. 1. It is also possible to use a multicyclone with several separation chambers 38 connected in series.

[0124] The hydrogen-containing product stream then encounters the first filter element 48, which serves to remove any carbon still present in the hydrogen-containing product stream. Thus, a secondary carbon product stream and a carbon-purified hydrogen-containing product stream are obtained via the first filter element 48.

[0125] The carbon-purified hydrogen-containing product stream can then be transferred through the valve 60 to the second filter element 50, which serves to separate any hydrocarbons contained in the hydrogen-containing product stream.

[0126] Thus, a purified hydrogen-containing product stream is obtained, which can be discharged via the pump device 52, for example to a storage and / or liquefaction device (not shown).

[0127] The hydrogen-containing product stream purified from carbon can be at least partially recycled to the reaction device 12 via the valve 60 and the second return line 58.

[0128] Furthermore, hydrocarbons separated in the second filter element 50 can be fed back to the reaction device 12 in order to convert them into hydrogen and carbon.

[0129] In the Fig. 2 to 8, various embodiments of the reaction device 12, in particular of the reaction chamber 14, are shown schematically, as they are in the device 10 according to Fig. 1 can be used.

[0130] Fig. 2 shows a first embodiment of the reaction chamber 14, in which the reaction chamber 14 is shaped such that it is curved or arcuate along the flow path of the reactant gas mixture (indicated by arrows).

[0131] The reaction chamber inlet 68 is accordingly arranged at an angle to the reaction chamber outlet 70, in the embodiment shown perpendicular to each other.

[0132] The electron beam source 16 is arranged in a curved region of the reaction chamber 14, so that the electron beam emitted by the electron beam source 16 is aligned tangentially to the flow path of the reactant gas mixture and in the direction of the flow path of the reactant gas mixture.

[0133] It can also be seen that the reaction chamber 14 has a cross-section that changes from the reaction chamber inlet 68 to the reaction chamber outlet 70, increasing in the direction of the reaction chamber outlet 70. In this way, the flow behavior of the reactant gas mixture within the reaction chamber 14 can be adapted. In particular, the relative increase in the cross-section is matched to the proportion of gases formed by the conversion of the reaction mixture and the associated increase in volume of the reactant gas mixture. It is also possible for the cross-section to decrease along the flow path instead of increasing.

[0134] It is also fundamentally possible that the reaction chamber 14, instead of the continuous curved course, consists of Fig. 2 has a rectangular design.

[0135] Fig. 3 shows a second embodiment of the reaction chamber 14, which is essentially analogous to the first embodiment.

[0136] In the second embodiment, however, the electron beam source 16 is arranged such that the electron beam 28 emitted by the electron beam source 16 is tangential to the flow path of the reactant gas mixture (analogous to Fig. 2), but is oriented opposite to the flow direction of the reactant gas mixture.

[0137] Fig. Figure 4 shows a third embodiment of the reaction chamber 14, in which the reaction chamber 14 extends in a straight line with the flow path of the reactant gas mixture. Thus, the reaction chamber inlet 68 and the reaction chamber outlet 70 are opposite each other.

[0138] The electron beam source 16 is arranged such that the electron beam emitted by the electron beam source 16 is aligned perpendicular to the flow path of the reactant gas mixture into the reaction chamber 14.

[0139] In the third embodiment of the reaction chamber 14, the cross-section of the reaction chamber 14 also increases along the flow path of the reactant gas mixture, with the cross-section increasing from a first chamber section 72 with a substantially constant first diameter through a transition region 74 to a second chamber section 76 with a substantially constant second diameter. In other words, the second diameter is larger than the first diameter. It is also possible for the cross-section to decrease along the flow path instead of increasing.

[0140] Fig. 5 illustrates a fourth embodiment of the reaction chamber 14 in which the reaction chamber inlet 68 is located on the same side of the reaction chamber 14 as the reaction chamber outlet 70.

[0141] The flow path of the reactant gas mixture is accordingly designed such that, starting from a first reaction chamber branch 78, it is deflected in a turning region 80 to a second reaction chamber branch 82, wherein the flow path undergoes a bend of 180° in the turning region 80.

[0142] The electron beam source 16 is arranged such that the electron beam 28 emitted by the electron beam source 16 passes through the reactant gas mixture in the turning area 80 multiple times, namely at least twice. In this way, the complete conversion of the gaseous saturated hydrocarbon can be promoted.

[0143] As in Fig. 5, the first reaction chamber branch 78 also has a smaller diameter than the second reaction chamber branch 82, so that in this embodiment, too, the diameter of the reaction chamber 14 increases along the flow path of the reactant gas mixture. In this embodiment, too, it is of course possible for the cross-section to decrease along the flow path instead of increasing.

[0144] Fig. 6 shows a fifth embodiment of the reaction chamber 14, in which the reaction chamber 14 runs in a straight line to the flow path of the reactant gas mixture, similar to the third embodiment.

[0145] However, the electron beam source 16 is not arranged perpendicular to the flow path of the reactant gas mixture, but coaxially to it.

[0146] The reaction mixture is introduced into the reaction chamber 14 via a plurality of reaction chamber inlets 68, each of the reaction chamber inlets 68 being assigned a supply branch 78, which are jointly supplied with the reactant gas mixture via the supply line 30.

[0147] The feed branches 78 together with the associated reaction chamber inlet 68 are arranged concentrically around the electron beam source 16.

[0148] It is also possible that, instead of several separate feed branches 78, a single feed branch 78 with a rotationally symmetrical cross section is present, which runs around the electron beam source 16, for example a feed branch 78 with an annular cross section.

[0149] In this case, it is also possible for several reaction chamber inlets 68 to be present despite a single supply branch 78 by inserting a diaphragm element (not shown) with openings at the end of the supply branch 78, the reaction chamber inlets 68 being formed by the openings in the diaphragm element.

[0150] Likewise, it can be provided that a plurality of supply branches 78 are present which are band-shaped in cross section and run in sections around the electron beam source 16, for example are supply branches 78 which are ring-shaped in cross section.

[0151] In Fig. 6 also shows that a chamber beam shaping device 79 is arranged in the reaction chamber 14. The chamber beam shaping device 79 can be configured analogously to the beam shaping device 25 used in the electron beam source 16 (cf. Fig. 1) and serves to direct the electron beam 28 through electromagnetic fields. This allows for even more precise control of the plasma within the reaction chamber 14.

[0152] Fig. 7 shows a sixth embodiment of the reaction chamber 14, in which two supply branches 78 are also present, each leading to an associated reaction chamber inlet 68.

[0153] In the sixth embodiment, the supply branches 78 are curved so that the flow direction of the reactant gas mixture at the reaction chamber inlets 68 is substantially perpendicular to the flow direction at the reaction chamber outlet 70.

[0154] The electron beam source 16 is arranged such that the feed branches 78 feed the reactant gas mixture into the reaction chamber 14, distributed concentrically around the electron beam source 16. The feed branches 78 are arranged, in particular, rotationally symmetrically around the axis of the electron beam generated by the electron beam source 16.

[0155] It is also possible that only one supply branch 78 with a ring-shaped cross section is present, which runs symmetrically around the electron beam source 16.

[0156] In addition, Fig. 7 that the reaction chamber 14 has a substantially constant diameter.

[0157] Fig. 8 shows a seventh embodiment of the reaction chamber 14, which can be regarded in particular as an extension of the sixth embodiment.

[0158] In the seventh embodiment, the supply branches 78 are designed such that the supply branches 78 run along a reaction chamber outer wall 80 of the reaction chamber 14, so that the reactant gas mixture can be preheated as it flows through the respective supply branch 78 through the reaction chamber outer wall 80, which in turn is heated by the electron beam plasma inside the reaction chamber 14. Thus, the reaction chamber 14 is simultaneously cooled. In this way, a heat exchange function is created immediately before the reactant gas mixture enters the electron beam plasma, as described for the reaction device 12 in Fig. 1 in the form of the second heat exchanger device 66 is indicated schematically.

[0159] It is understood that individual features of the previously described embodiments of the reaction chamber 14 can be combined with one another, as long as this is technically feasible. For example, a reaction chamber 14 with a variable cross-section can also be used in the sixth and seventh embodiments.

[0160] In the representations of the Fig. 2 to 8, only a single electron beam source 16 is present. However, it is also possible to use more than one electron beam source 16. In this way, it can be particularly well ensured that as large a portion of the reaction chamber 14 as possible is filled with the electron beam plasma, thus achieving the most complete conversion of the reactant gas mixture into hydrogen and carbon.

[0161] As in the previously described embodiments according to Fig. As indicated in Figures 2 to 8, the electron beam source 16 can generate an axial beam or a linear beam from a point-like starting point. Of course, other configurations for the electron beam source 16 and the electron beam generated thereby are also conceivable. For example, the electron beam source 16 can have an elongated starting point for the electron beam, which generates a linear ribbon beam or a flat beam.

[0162] In other words, the figures presented in the Fig. The electron beam sources 16 shown in Figures 2 to 8 can be designed either to generate an axial or a band-shaped beam.

[0163] In Fig. 9 a second embodiment of the device 10 according to the invention is shown schematically.

[0164] The second embodiment is essentially the same as the first embodiment, so only the differences will be discussed in more detail below. Identical or functionally equivalent components are provided with the same reference numerals, and reference is made to the above explanations.

[0165] In the second embodiment, a third heat exchanger device 84 is additionally provided, which is assigned to the return line 58 and removes heat from the gas flowing through the return line 58 and supplies it to the reactant gas mixture in order to preheat it.

[0166] This makes it possible to distribute the heat generated in the device 10. For example, in a case where the additional valve 61 prevents gaseous components recirculated via the first return line 56 and the second return line 58 from entering the reaction chamber 14, but a flow of reactant gas mixture from the supply line 30 into the reaction chamber 14 is maintained, the reactant gas mixture can still be preheated using heat extracted from the gaseous components contained in the second return line 58.

[0167] It is understood that the third heat exchanger device 84 cannot be assigned solely to the return line 58. It is also possible for the third heat exchanger device 84 to be additionally or alternatively arranged between the cyclone separator 34 and the first filter element 48, between the first filter element 48 and the second filter element 50, and / or to be assigned to the first return line 56.

[0168] The other components of the device 10 can be designed analogously to the first embodiment, for example the reaction chamber 14 can be designed according to one of the embodiments previously described in connection with the first embodiment.

[0169] Overall, the device 10 for hydrogen production according to the invention is characterized by a compact design and a targeted reaction control that provides both hydrogen as the desired energy carrier and economically valuable carbon species. Furthermore, a particularly energy-saving and efficient process for producing hydrogen is enabled, allowing hydrogen to be produced in a particularly climate-friendly manner. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Kerscher F. et al.: „Low-carbon hydrogen production via electron beam plasma methane pyrolysis: Techno-economic analysis and carbon footprint assessment“ (International Journal of Hydrogen Energy, doi: 10.1016 / j.ijhydene.2021.03.114

[0008]

Claims

[1] Device (10) for the pyrolysis of gaseous saturated hydrocarbons by means of an electron beam plasma to produce hydrogen, wherein the device (10) comprises a supply line (30) for supplying a reactant gas mixture, a reaction device (12) fluidically connected to the supply line (30) and a filter device (32) arranged downstream of the reaction device (12) and fluidically connected to the reaction device (12), wherein the reactant gas mixture comprises a gaseous saturated hydrocarbon, wherein the reaction device (12) has a reaction chamber (14) and is designed to at least partially convert the reactant gas mixture in the reaction chamber (14) in an electron beam plasma generated by an electron beam into a reaction mixture containing hydrogen and carbon dispersed in the reaction mixture, and wherein the filter device (32) comprises a cyclone separator (34) for separating the dispersed carbon to obtain a hydrogen-containing product stream. [2] The device (10) of claim 1, wherein the gaseous saturated hydrocarbon is selected from the group consisting of hydrocarbons having at most four carbon atoms and combinations thereof, preferably wherein the gaseous saturated hydrocarbon is methane. [3] Device (10) according to claim 1 or 2, wherein the reaction device (12) has an electron beam source (16) which is separated from the reaction chamber (14) by a separation window (26) which is at least partially transparent to electrons, wherein the separation window (26) consists in particular of a polyaryletherketone, preferably of polyetheretherketone. [4] Device (10) according to one of the preceding claims, wherein the reaction chamber (14) is curved or straight along the flow path of the reactant gas mixture in the reaction chamber (14). [5] Device (10) according to one of the preceding claims, wherein the reaction chamber (14) has more than one reaction chamber inlet (68) through which the reactant gas mixture from the supply line (30) can be fed into the reaction chamber (14). [6] Device (10) according to one of the preceding claims, wherein the reaction chamber (14) has a changing cross-section along the flow path of the reactant gas mixture. [7] Device (10) according to one of the preceding claims, wherein a flow guide element is arranged in the reaction chamber (14) for influencing the flow velocity and / or the flow pattern of the reactant gas mixture. [8] Device (10) according to one of the preceding claims, wherein the cyclone separator (34) has an inlet pipe (36) by means of which the reaction mixture can be transferred into a separation chamber (38) of the cyclone separator (34), wherein the inlet pipe (36) has a changing cross-section in its axial direction. [9] Device (10) according to one of the preceding claims, wherein the filter device (32) has at least one filter element (48, 50) arranged downstream of the cyclone separator (34) for separating carbon contained in the hydrogen-containing product stream and / or hydrocarbons contained in the hydrogen-containing product stream. [10] Device (10) according to one of the preceding claims, wherein the cyclone separator has a rotary valve (42) for collecting the separated carbon. [11] Device (10) according to one of the preceding claims, wherein the device (10) has a return line (56, 58) via which the hydrogen-containing product stream can be at least partially returned to the reaction chamber (14). [12] Device (10) according to one of the preceding claims, wherein the supply line (30) for heating the reactant gas mixture is in contact with a first heat exchanger device (62) which is arranged in or on an outer wall (64) of the cyclone separator (34), or is part of a first heat exchanger device (62) which is arranged in or on an outer wall (64) of the cyclone separator (34). [13] A method for producing hydrogen using a device (10) according to any one of the preceding claims, wherein in the method a reactant gas mixture comprising at least one gaseous saturated hydrocarbon is converted by means of an electron beam plasma to a reaction mixture containing hydrogen and carbon dispersed in the reaction mixture, wherein the carbon dispersed in the reaction mixture is separated from the reaction mixture in a cyclone separator (34) of a filter device (32) and a hydrogen-containing product stream is obtained. [14] Method (10) according to claim 13, wherein the residence time of the reactant gas mixture in the reaction chamber is 1.0 to 5.0 ms, preferably 2.5 to 3.0 ms.

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