Apparatus and method for efficient production of hydrogen by pyrolysis

Abstract

The invention relates to a plant for the efficient production of hydrogen by pyrolysis of an input gas mixture comprising gaseous hydrocarbons, said plant comprising: a reactor (1) for heating and pyrolyzing said input gas mixture by means of an electric arc, and thus producing a produced output mixture rich in hydrogen and containing solid fractions (carbon black and / or carbon of various shapes); a heat exchanger (4) for preheating the input gas mixture and cooling the produced output mixture; the apparatus is characterized in that the reactor (1) comprises a containment structure (100) defining a reaction chamber (101), provided with controllable openings for an input (120) of the input gas mixture, for an output (130) of the resulting mixture; the invention relates to a reaction chamber (101) comprising a containment structure (100), at least one electrode (200) passing through one or more apertures in the containment structure (100), and a sealing element (150) between the apertures and the at least one electrode (200) for preventing gas exchange between the inside and the outside, at least one electrically conductive element (300) disposed at least partially within the reaction chamber (101), the at least one electrode (200) is movable along its axis (X) with respect to the other electrode (200) or with respect to the conductive element (300) wherein the arc is formed between the one or more electrodes (200) and the conductive element (300); and wherein the heat exchanger (4) provides one or more heat exchange and storage elements (42) wherein the heat exchange and storage elements (42) store heat by cooling the resulting mixture exiting the reactor (1) and transfer heat successively or simultaneously by preheating the gas mixture entering the reactor (1). The invention also relates to a method for the efficient production of hydrogen by pyrolysis.

Description

[0001] -

[0002] The present invention relates to an apparatus for efficiently producing hydrogen by pyrolysis. The present invention further relates to a method for efficiently producing hydrogen by pyrolysis.

[0003] In more detail, the present invention relates to the production of hydrogen by pyrolysis of hydrocarbons. As is known, the solutions for producing hydrogen known in the prior art are divided into several categories according to the basic chemical reaction used to obtain the hydrogen molecules, and in particular assigned colors for "disclosure" purposes.

[0004] In particular, mention may be made of:

[0005] - "grey" hydrogen, produced by steam reforming methane, a technology that has a significant impact from a CO2 emissions perspective;

[0006] - "Blue" hydrogen, where steam reforming of methane is performed with CO2 capture;

[0007] - "green" hydrogen, where the production is carried out by electrolysis of water using electricity generated from renewable sources;

[0008] - "Teal" hydrogen, which provides for direct pyrolysis of methane (and / or other hydrocarbons).

[0009] The latter technology requires a lower amount of energy compared to the other technologies mentioned (eg, as little as one-seventh of the energy consumption of methods used to produce green hydrogen).

[0010] In particular, the production of "cyan" hydrogen has recently been developed, with three technologies in general and in particular those referred to below as technology A (based on the use of the "molten pool bubble method"), technology B (based on the use of plasma) (plasma-based) and technology C (based on the use of a granular catalytic bed).

[0011] The solution proposed according to the present invention was investigated based on technology B, which is currently used on an industrial scale for the production of C2H2 (acetylene) and carbon black (CB) at high / very high temperatures, with hydrogen as a by-product.

[0012] In particular, with plasma-based type B technology, solutions such as plasma torches are generally used, in which an arc is generated by metallic electrodes (anode and cathode) usually powered by direct current and usually cooled by a circuit in which water circulates.

[0013] The alternative, Technology B or "Plasma Technology", involves the use of electrodes made of carbon (usually graphite) that are operated by both direct and alternating current.

[0014] In both cases, to allow regulation of the electric power, the cathode and the anode are mounted along axes inclined relative to each other, making it possible, by their movement, to bring the ends closer together and further apart and thus vary the current at the same voltage.

[0015] In this technical context, the following can be distinguished:

[0016] - Direct heating solutions, where methane is typically injected via a torch or near a plasma arc;

[0017] -Indirect heating solution, in which the reactor is made by forming two (or more) zones to isolate the arc. The reaction gases are thus heated by a second carrier gas that transfers energy from the arc to the methane. This configuration is commonly used to maximize the production of CB. The stream leaving the reactor (usually consisting of a mixture of H2, C2H2, and lower amounts of other gases) contains one or more types of CB. Therefore, the stream is cooled and processed with high efficiency in a gas / solid separation system (scrubber, cyclone separator, filter). In the case of systems for the production of CB, the H2-rich gaseous stream leaving the filtration system is typically treated as effluent and rendered inert by a flare before being released into the atmosphere.

[0018] However, the known technology B or plasma technology has operational limitations when applied, and in particular:

[0019] 1. In the case of methane injection from the torch itself, the torch becomes clogged due to the formation of solid carbon near the nozzle. This defect mainly occurs when using a plasma torch or a solution based on injecting the reaction gas through a perforated electrode;

[0020] 2. A portion of the energy useful for the reaction is lost in the cooling system (e.g. for a water-cooled torch);

[0021] 3. Difficulty in moving and replacing electrodes due to their tilt, especially for AC cases;

[0022] 4. Due to the tilt of the electrodes, it is still difficult to ensure the seal between the electrodes and the electrode channel openings in the reactor structure, especially for the AC case;

[0023] 5. In the case of high AC electric powers, which can generate significant vibrations in the electrodes, the problem of mechanical resistance is further exacerbated by the tilting of the electrodes (this problem forces the choice of electrode type to be limited to those with higher mechanical resistance, i.e. electrodes made of graphite, which is known to be more expensive than electrodes made of prebaked carbon and Soderberg-type electrodes);

[0024] 6. Problems during the lengthening of the electrodes, still due to their tilting, which requires the installation of additional elements in the part outside the reactor to compensate for the consumption of the electrodes;

[0025] 7. Indirect heating solutions require the use of a carrier gas to transfer energy. In the case where this gas has a composition similar to that of the output gas, it will not be necessary to separate it from the product stream. However, this solution reduces the H2 yield of the process and requires a system for separating the carrier gas from the product.

[0026] 8. Heat recovery from the hot gases leaving the reactor is non-existent or limited, and therefore energy efficiency is low;

[0027] 9. Heat recovery from the hot solids (CB) leaving the reactor is non-existent or limited and therefore energy inefficient.

[0028] With particular reference to points 8 and 9, these limitations are of a technical / economic nature, since recovering heat from a powder stream (due to the presence of CB) at very high temperatures generally requires the removal of the solid fraction before heat exchange (to avoid clogging of the exchanger). This type of solution is very expensive and, in any case, is characterized by a maximum temperature limit (a few hundred ° C, up to 800 ° C). This results in a limited energetic efficiency of the actual process, even though, in terms of pure reaction enthalpy, the pyrolysis reaction of hydrocarbons is the most favorable of the existing technologies for producing hydrogen.

[0029] The main object of the present invention is to provide a solution for a method for the efficient production of hydrogen, in particular cyan hydrogen, as well as an apparatus for the efficient production of hydrogen, and a reactor and a heat exchanger for the efficient production of hydrogen, which are able to solve the above-mentioned problems of the prior art in a unique combination.

[0030] These results are achieved according to the invention by a device as described and claimed in independent claim 1 .

[0031] The present invention further relates to a method for the efficient production of hydrogen as claimed in claim 16.

[0032] For illustrative and non-limiting purposes, the present invention will now be described in accordance with preferred embodiments thereof, with particular reference to the figures of the accompanying drawings, in which:

[0033] Figure 1 is a schematic diagram of the gaseous flows in an apparatus according to the invention for carrying out the method according to the invention.

[0034] Figure 2 A scheme showing the temperature evolution of a gas flow in a device according to the invention;

[0035] Figures 3a-3d A further evolution of the gas flow, in particular its composition, is shown;

[0036] Figure 4 shows a cross-sectional view of a first non-limiting embodiment of a reactor according to the invention, the reactor forming part of an apparatus according to the invention for carrying out the method according to the invention;

[0037] Figures 4a-4d are schematic diagrams on orthogonal planes of different possible alternative embodiments of a reactor forming part of an apparatus according to the invention for carrying out the method according to the invention;

[0038] Figure 5 shows a sectional view of a second embodiment of a reactor according to the invention, which reactor forms part of an apparatus according to the invention for carrying out the method according to the invention;

[0039] Figure 6 shows a sectional view of a third embodiment of a reactor according to the invention, which forms part of an apparatus according to the invention for carrying out the method according to the invention;

[0040] Figure 7 shows a sectional view of a fourth embodiment of a reactor according to the invention, which forms part of an apparatus according to the invention for carrying out the method according to the invention;

[0041] Figure 8 A first embodiment of an innovative exchanger for use in a device according to the invention for carrying out the method according to the invention is schematically shown in a non-limiting manner;

[0042] Figure 9 、 10 and 11 is Figure 8 A corresponding vertical cross-sectional view of the exchanger in the embodiment of FIG.

[0043] Figure 12 schematically shows an embodiment of an apparatus according to the invention for carrying out the method according to the invention; and

[0044] Figure 13 and 14 A second embodiment of an innovative exchanger for the device according to the invention for carrying out the method according to the invention is schematically shown.

[0045] Now look at the drawings, and especially the initial Figure 1 , it should be observed that the device according to the invention mainly comprises:

[0046] Plasma Arc Reactor 1(R)

[0047] Solid-gas separator 2 (SGS) and gas-gas separator 3 (GGS)

[0048] • Heat exchanger 4 (H / E) for preheating the input flow of methane.

[0049] exist Figure 1 In FIG. 1 , as described, a conceptual diagram representing the gas flow in the apparatus according to the present invention is shown.

[0050] In particular, there is an incoming feed stream "FG" (feed gas) of a gas or gas mixture comprising hydrocarbons (e.g. methane or compound C x H y Alternatively, the incoming gas may be at least partially of non-fossil origin, but produced from renewable resources, for example it may be biogas or biomethane. In the following of this disclosure, reference will mainly be made to methane, which includes the above-mentioned alternatives.

[0051] The flow through the reactor 1 , which operates at high temperature (1200-2000° C., preferably 1200-1500° C.) and in the substantial absence of oxygen, allows the known pyrolysis reaction of the feed gas FG to proceed.

[0052] As a result of these reactions, there is an output stream of a gas mixture whose composition is rich in hydrogen H ; that is, the hydrogen concentration H in the output gas mixture is greater than the hydrogen concentration H in the incoming feed gas FG. In addition to hydrogen H , the output stream also consists of acetylene C 2 H 2 , plus a gaseous residue, the composition of which depends essentially on the composition of the incoming gas and on the course of the flow through the reactor 1 , and a solid residue, which is mainly solid carbon in various crystalline and aggregated forms (hereinafter referred to as solid carbon, abbreviated SC), including the aforementioned carbon black.

[0053] In the method according to the invention, the gas to be treated, particularly methane, is preheated in a heat exchanger 4. The preheated gas stream S1 is then fed to a plasma reactor 1, where a pyrolysis reaction occurs. A stream S2 of the resulting gases (hydrogen, a gaseous residue typically containing acetylene and methane, plus a solid fraction consisting of powdered carbon, etc.), at high temperature, is then passed through the same heat exchanger, cooling itself while also benefiting the incoming methane. Finally, the cooled gas stream S3 continues to a gas / solid separator (SGS) to remove the solid fraction (SC). The solid fraction-purified stream S4 is then fed to a gas / gas separator (GGS) to remove other gases (including methane and acetylene) originating from the pyrolysis reaction and / or residues of other gases already present in the incoming gas, resulting in a main stream S51 consisting primarily of hydrogen and a residual stream S52 containing methane, acetylene, and / or other gases (as described above). This residual stream can optionally be recycled by joining it with the gas stream FG to be treated. In summary, the method according to the present invention provides three steps (such as Figure 2 shown).

[0054] - a step of preheating the methane stream,

[0055] - a reaction step, and

[0056] - A step of cooling the produced gas (now rich in hydrogen).

[0057] Attachment Figures 3a-3d An example of the evolution of a gas flow is shown in , which shows the time trend of the mass fractions of certain components (respectively methane CH4, hydrogen H2, acetylene C2H2, solid carbon in powder or other aggregated form) per unit mass of gas subjected to the method according to the invention.

[0058] Now observe the figure in Figure 4 , shows a first embodiment of a reactor according to the invention (generally indicated by the reference numeral 1 ) which provides an outer metal structure 100 (possibly water-cooled in a known manner), and a thermally insulating inner coating 110 .

[0059] The metal structure 100 and the inner coating 110 together define a reaction chamber 101 inside the reactor 1 .

[0060] In this embodiment, at least one opening 120 is provided in the metal structure 100 of the reactor 1, which is connected to a system for supplying a gas to be treated (in this case, a gas mixture containing hydrocarbons, in particular methane gas), and which allows the gas to be treated to enter the reaction chamber 101. Figure 4a 、 4b, 4c and 4d, the at least one opening 120 can be made in various ways:

[0061] -Multiple injection points towards the electrodes, e.g. Figure 4a As shown;

[0062] -Injection points are distributed at different locations along the direction parallel to the electrode axis to better distribute the gas, e.g. Figure 4b (the inlets are distributed along a single electrode, or on a single side relative to a plane passing through the arc region and perpendicular to the electrode axis) and Figure 4c (the inlets are distributed on both sides of a plane passing through the arc region and perpendicular to the electrode axis);

[0063] - Injection in a tangential arrangement in order to create a cyclonic flow for promoting CB separation in the reactor, e.g. Figure 4d shown.

[0064] The gas flow entering through the opening 120 has the secondary effect of cooling the electrode, thereby increasing the service life and duration of the electrode. From this perspective, Figure 4c The solution shown in is particularly advantageous because it allows a cooling effect on both sides of the arc.

[0065] In this embodiment, at least one opening 130 is arranged in the lower part and faces vertically downward (alternatively, the opening 130 can be arranged in the upper part, facing laterally or upward) for leakage of reaction products, which include a mixture of gases (including hydrogen and hydrocarbons and / or acetylene and possible residues of other gases, as described above) and solids (solid carbon, SC, in the form of powder or other aggregates). The opening 130 is connected to the rest of the equipment (not shown in the figure), which includes a system for processing the reaction products (including cooling in a dedicated heat exchanger 4, separation of solid carbon in a gas / solid separator 2, and separation of residual methane and acetylene from hydrogen in a gas / gas separator 3).

[0066] Furthermore, the structure 100 provides at least one opening 135 for introducing at least one electrode 200. Furthermore, elements 140 for thermal insulation and elements 150 for pneumatic sealing are provided, which are adapted to prevent gas exchange between the interior and the exterior of the reactor at the opening 135 for introducing the electrode 200, and are particularly intended to prevent air, in particular oxygen, from entering the reactor 1 and to prevent the reaction gases (also highly flammable gases with explosive reactions) within the reactor 1 from escaping.

[0067] Furthermore, in the reactor 1 , there is a fixed electrode 300 (eg, an anode) electrically connected to the outside of the reactor.

[0068] The movable electrode 200 (in this case the cathode) is arranged vertically and there are means (not shown) for moving the electrode along its longitudinal axis. Furthermore, preferably, the movable electrode 200 has a circular and completely cylindrical cross-section (ie no longitudinal holes are present).

[0069] In the reactor 1 according to the invention, the gas stream to be treated (feed gas FG as described above) enters through the channel 120 and is heated by the electric arc between the anode 300 and the cathode 200 until the pyrolysis reaction is activated. The gas mixture originating from the pyrolysis reaction is then extracted through the opening 130 which connects the reactor 1 with the rest of the plant.

[0070] exist Figure 5 In the embodiment shown, the reactor 1 of the apparatus according to the present invention is similar to the reactor 2 of the reference Figure 4 The reactor shown and described is identical except that the at least one lower opening 130 is horizontally oriented and positioned.

[0071] In the attached figure Figure 6 , a third embodiment of a reactor 1 of a device according to the invention is shown, in which a fixed electrode 300 (anode) is placed vertically below a movable electrode 200. The gases produced by the pyrolysis reaction are thus discharged from the reactor 1 through an opening 160 arranged laterally below the structure 100, connected to the rest of the device (not shown).

[0072] The anode 300 is supported by a structure 170 made of insulating material and is connected to the power supply system via one or more connections 180 .

[0073] Another embodiment of the reactor 1 is Figure 7 Schematically represented in FIG, wherein three electrodes 200 (one of which is visible in a cross-plane, one represented in a partial view and the third not visible in the figure) are supplied by a three-phase system, wherein each electrode is connected to one of the three phases of the system.

[0074] Furthermore, there is a fixed conducting element 300 which electrically forms the star center of the three-phase system. The fixed conducting element 300 , preferably made of carbon, is supported by a support structure 310 which is electrically insulated relative to the outer metal structure 100 .

[0075] With this configuration, each electrode 200 can be moved relative to the fixed element 300 regardless of the other electrodes. This allows the arc struck between each electrode 200 and the fixed conductive element 300 to be adjusted, even when the electrodes are arranged vertically and movable in the vertical direction.

[0076] This allows at least partially solving the above-mentioned technical and maintenance problems related to configurations in which the electrodes have an inclined arrangement with respect to the vertical axis.

[0077] The reactor 1 described above with reference to the figures of the accompanying drawings forms an example of a reactor provided in an apparatus according to the invention for carrying out the method according to the invention, which reactor forms a system operating at high temperatures (1200° C.-2000° C., preferably 1200° C.-1500° C.) by direct technology (i.e. without a carrier gas for transporting thermal energy), wherein the energy is provided by a plasma arc generated by electrodes made of carbon through which a direct current (DC) or an alternating current (AC) flows.

[0078] As shown, the electrode is positioned vertically and moves along its axis and can be made of graphite, amorphous carbon or be of the Soderberg type.

[0079] However, when operating in both direct current (DC) and alternating current (AC) systems, there are fixed conductive elements made of carbon in the lower part of the reactor 1 .

[0080] In the case of a direct current (DC) system, it is a fixed electrode placed vertically below a movable electrode so that an arc strikes between the two electrodes.

[0081] In contrast, in the case of AC operation, in addition to the three phases and three electrodes, which are vertically movable and independent of one another, the fixed element is electrically configured as a fixed "star center"; this star center is located midway between the three electrodes, so that the arc strikes between each single phase (electrode) and the star center. It should be observed that, whereas in known electric arc furnaces, the arc strikes between the electrodes and the molten metal pool, which represents the "star center" of the circuit, in the reactor 1 according to the invention, the molten metal pool is replaced by a fixed conductive element.

[0082] Still according to the present invention, a system for controlling and moving electrodes is provided, which system is capable of adjusting the distance between the movable electrode and the fixed electrode (in the DC case) or between the electrode and the star center (in the AC case) according to current and voltage parameters suitable for generating an arc.

[0083] In order to ensure operational safety in connection with highly explosive / flammable atmospheres, the reactor 1 according to the invention is provided with a sealing system for preventing the ingress of air / oxygen into the reactor and at the same time preventing the escape of internal gases (methane, hydrogen, acetylene, etc.).

[0084] The above-mentioned problems 3) to 6) of the prior art are at least partially solved by means of the arrangement of the electrodes and their vertical movement. The vertical arrangement eliminates bending stresses caused by the electrodes' own weight, thereby reducing mechanical stress and enabling the use of electrode types with lower mechanical resistance and cost. Furthermore, it allows for easier electrode lengthening procedures, similar to those used in electric arc furnaces (EAFs) and submerged arc furnaces (SAFs). Finally, the pneumatic sealing between the electrodes and the channel openings in the reactor structure is simplified.

[0085] Now observe the figure in Figure 8 , schematically shows a heat exchanger generally indicated by reference numeral 4, which forms a heat recovery system for using the heat of the produced gas to preheat the gas mixture FG entering the reactor 1 (as mentioned above, the gas mixture contains gaseous hydrocarbons C x H y , especially methane).

[0086] The heat exchanger can be manufactured according to two preferred embodiments.

[0087] exist Figure 8 In a first embodiment schematically shown in FIG. 4 (where lighter grey corresponds to lower temperatures and darker grey corresponds to higher temperatures), the heat exchanger 4 is of the movable bed type of typically spherical elements, which is divided into two sections: in a first 41 ( Figure 8 In the upper part of the reactor 1 ), the hot gases S2 leaving the reactor 1 transfer heat to the spherical elements 42, thereby generating a resulting cooled gas flow S3 leaving the exchanger 4. Said spherical elements 42 are preferably made of a hard material resistant to temperatures above 1200 / 1500 / 2000° C. (depending on the process temperature, alumina may be a possible material for the elements 42).

[0088] Throughout the description, and in particular in this part relating to the description of the drawings, reference is made to spherical elements 42, but they may be replaced by other solid elements adapted to form a movable bed extending in the vertical direction, even if circular shape is preferred, which are introduced from above and fall downwards by gravity (the cooled gas is sucked in at the outlet of the exchanger 4).

[0089] In the second part 43 ( Figure 8 The spherical elements 42 are arranged in the lower part of the upper part 41, after being heated in the upper part 41, and transfer heat to the gas flow FG entering the exchanger 4 and intended to enter the reactor 1 as a preheated gas flow S1, preheating it. The passage between the two parts 41 and 43 is made to allow the passage of the spherical elements 42, while preventing (or in any case restricting) the passage of gas between the second part 43 and the first part 41.

[0090] Outside the heat exchanger 4 there is a system (not shown and optional) for recirculating the spherical elements 42 from the second portion 43 to the first portion 41 .

[0091] Besides allowing cooling of the spherical elements 42 , said system also provides a step for cleaning them, since the hot gases leaving the reactor 1 are enriched in SC in suspension partially deposited on said spherical elements 42 and therefore need to be removed therefrom at least periodically.

[0092] Now watch Figure 9 、 10 1 and 11 , show a first embodiment of an exchanger 4 (a movable bed of spherical elements or similar shapes) consisting of an external metal structure coated internally with one or more layers, some of which consist of refractory materials and others of insulating materials; these layers may also consist of materials different from one another and may have different distinguishable mechanical and thermal characteristics (insulating or refractory). In particular, the refractory material used may be based on alumina.

[0093] Internally, the exchanger 4 has at least one duct 1100 for the substantially vertical passage of the spherical elements 42 , included between an inlet 1101 and an outlet 1102 .

[0094] An upper region 1103 , an intermediate or transition region 1104 , and a lower region 1105 can be identified along the conduit 1100 .

[0095] The input of the spherical elements 42 takes place through at least one duct 1101 ′ of smaller diameter than the duct 1100 , which duct 1101 ′ extends inside the duct 1100 through the upper wall of the exchanger 4 over a section of length H1 .

[0096] In addition to the inlet 1101 of the spherical element 42, the upper region 1103 also includes at least one inlet 1110 for the gas flow (for example, a mixture of hydrogen, methane, acetylene, etc.) from the reactor 1 to enter the upper region. As is well known, the inlet 1110 can be configured, for example, as a plurality of outlets in the pipe 1100, which are evenly distributed along the cross section of the pipe itself, that is, distributed along the circumference of the pipe at the cross section; it is also possible to provide a distribution on a plurality of cross sections placed at different heights.

[0097] The upper zone 1103 further comprises at least one outlet 1120 for discharging the gas stream coming from the reactor 1 , arranged in the section (length H1 ) comprised between the bottom end portion of the duct 1101 ′ and the upper wall of the exchanger 4 .

[0098] The gas passing through the upper region 1103 transfers heat to the spherical elements 42, which are themselves cooled, and these spherical elements pass downward along the pipe 1101' under the action of gravity.

[0099] In addition to the outlet 1102 for the spherical elements 42, the lower region 1105 also includes at least one duct 1104' for allowing the spherical elements from the transition region 1104 to enter the lower region 1105. Said duct 1104' may have a smaller diameter than the duct 1100 and extend through the upper wall of the lower region 1105 over a length H2.

[0100] This lower zone 1105 further comprises at least one inlet 1130 intended for the gas to be treated of the reactor 1, which inlet may be single, as shown, or may be configured, as is known in the art, in a plurality of outlets in the duct 1130 uniformly distributed along the cross section of the duct 1100. Furthermore, it is also possible to provide a distribution over several cross sections placed at different heights.

[0101] Furthermore, the lower zone 1105 provides at least one outlet 1140 for the gas to be treated to the reactor 1 , situated in the section (length H2 ) comprised between the bottom portion of the duct 1102 ′ and the upper wall of the lower zone 1105 of the exchanger 4 .

[0102] Therefore, the gas to be treated receives heat from the spherical elements 42 previously heated in the upper region 1103 , thereby heating itself, and these spherical elements are also cooled in the lower region 1105 .

[0103] Depending on process parameters (including the temperature of spherical elements 42 entering lower region 1105 and the flow rate of the gas to be treated), the gas to be treated can reach temperatures exceeding 400°C to 600°C, thereby allowing partial cracking of hydrocarbons in the heat exchanger. This allows for reduced energy consumption in the reactor. Preferably, but not exclusively, lower region 1105 can conform to an inverted truncated cone shape in the bottom region, as shown in the figure.

[0104] The transition zone 1104 is identified between the connection at a lower height of the upper zone 1103 (in the figure, the inlet 1110 for the gases leaving the reactor 1) and the upper wall of the lower zone 1105. Preferably, but not exclusively, as shown in the figure, the transition zone 1104 has a reduced cross-section with a truncated cone-shaped convergent section, the angle between the axis of which is preferably less than 20° with the wall.

[0105] Preferably, but not exclusively, the transition region 1104 comprises a plurality of pipes 1104' connecting the upper region 1103 to the lower region 1105, such as Figure 11 Schematically represented in .

[0106] Means 1303 for regulating the flow of the spherical element 42 ( Figure 12 ) is provided at the outlet 1102 of the exchanger 4, which device may be made, for example, of a rotary valve of known type (hereinafter referred to as valve 1303).

[0107] The mode of management of the exchanger 4 provides that the entire flow of the spherical element is regulated only by the valve 1303 and there is never a free fall segment. The geometry of the internal components is shaped to maintain the mass flow in order to optimize the heat transfer between the gas and the solid.

[0108] In particular:

[0109] - the pipe 1101 ′ is continuously filled with spherical elements 42 , at least in the section between the upper wall of the exchanger 4 and the bottom end portion of the pipe itself;

[0110] - the upper region 1103 continues to be filled with the spherical elements 42 up to the lower edge of the duct 1101 ′;

[0111] - the transition zone 1104 including the duct 1104 ′ is continuously filled;

[0112] The lower region 1105 is continuously filled up to the lower edge of the duct 1104 ′.

[0113] Thus (especially observing Figure 10 ) At least two plenum regions A and B are generated: plenum A between the outer wall of pipe 1101′ and the corresponding region of the inner wall of pipe 1100; and plenum B between the outer wall of pipe 1104′ and the corresponding region of the inner wall of pipe 1100. Output gases are drawn from the two plenums A and B, and these output gases are hydrogen-rich gas from plenum A and gas to be processed from plenum B, respectively.

[0114] Now look at the attached figure Figure 12 , it should be observed that the structure of the heat exchanger 4 according to the invention allows to overcome many drawbacks.

[0115] In particular, in the upper region of the exchanger 4, it is necessary to ensure that the gas transitioning in the first chamber (the gas cooled by the flow of the descending spherical element 42) essentially all leaves the exchanger 4 through the conduit 1120 and does not leak through the inlet path 1101 of the spherical element 42 itself.

[0116] Furthermore, it is necessary to ensure that the loading of the spherical elements 42 is carried out without introducing oxygen or an oxidizing mixture of gases (for example air) into the exchanger 4 .

[0117] In the embodiment shown in the drawings, this object is achieved by a system for loading spherical elements 42, such as Figure 12 The following components are shown from top to bottom:

[0118] - a first container 1201 of a spherical element 42 , such as a silo or a hopper;

[0119] - a first sealing valve 1301 (open-closed) for allowing / blocking the spherical element 42 and the gas to pass through;

[0120] a second container 1202 of the spherical element 42 (for example a closed silo), to which is connected an internal atmosphere control system 1202 ′ connected to the silo 1202 , making it possible to create vacuum conditions and / or controlled atmosphere conditions (for example, inert or with nitrogen, etc.);

[0121] - a second sealing valve 1302 (open-closed) for allowing / blocking the spherical element 42 and the gas to pass through;

[0122] a third container 1203 (for example a closed silo) of the spherical element 42 , directly connected to the exchanger 4 via a pipe 1101 ′.

[0123] With this configuration of the exchanger 4 , it is possible to carry out a method of introducing the spherical element 42 into the exchanger 4 itself, comprising the following steps:

[0124] 1. Close valve 1301 and fill container 1201 with an amount not less than the capacity of container 1202;

[0125] 2. When container 1202 is empty, close valve 1302, open valve 1301, and fill container 1202;

[0126] 3. Valve 1301 is closed, and controlled atmosphere conditions (vacuum, inert atmosphere, etc.) are formed in container 1202 through system 1202';

[0127] 4. Open valve 1302 for unloading the contents of container 1202 into container 1203 , from which spherical elements 42 flow through pipe 1101 ′ into the exchanger, with a continuous flow regulated by valve 1303 .

[0128] Thus, in the section below the valve 1302, the presence of a controlled atmosphere and a plurality of spherical elements 42 adapted to ensure a constant flow rate is always ensured, while preventing hydrogen from leaking from the pipes for introducing the spherical elements 42 and preventing oxygen from entering the heat exchanger:

[0129] - the containers 1201 and 1203 accommodate the spherical element 42 at a variable level, and the container 1203 is never in a state without the spherical element 42;

[0130] - Container 1202 alternates between a completely filled state (when it receives a charge from container 1201 ) and a completely empty state (when a charge is poured into container 1203 ).

[0131] There are further possible variations of the above sequence and these allow achieving the same purpose.

[0132] As can be seen in the figure, in the exchanger 4 there is a transition zone 1104 where the spherical elements 42 transfer heat from the top chamber 1103 (where the spherical elements 42 receive heat from the gas flow leaving the reactor 1) to the bottom chamber 1105 (where the spherical elements 42 transfer heat by preheating the gas to be treated (typically methane) entering the reactor 1).

[0133] In this transition zone 1104 , it is necessary to limit the circulation of the gas to be treated from the bottom chamber to the top chamber, thereby maximizing its circulation toward the reactor 1 .

[0134] To this end, it is necessary to ensure that a suitable hydraulic / fluid dynamic / fluid resistance (or in other words, pressure drop) is formed for the circulation of gas in the transition area 1104. At the same time, it is necessary to ensure a suitable flow downward of the spherical element 42 to avoid blockage in the path of the spherical element 42 itself.

[0135] This result can be achieved by selecting spherical elements 42 of suitably small average size, both in absolute terms and relative to the smallest dimension of the path within the exchanger. Preferably, the average diameter of the spherical elements 42 is less than 50 mm / 25 mm / 10 mm / 5 mm / 1 mm, for example 6 mm, or for example 5 mm.

[0136] To ensure proper flow through the spherical element 42 without clogging, the minimum diameter of the channel needs to be at least 10 times the average diameter of the spherical element 42. Another key parameter for generating proper hydraulic resistance (or pressure drop) to the flow of gas is the length of the transition region 1104, which needs to be preferably at least 10 / 20 / 50 / 100 / 200 times the average diameter of the spherical element 42.

[0137] Finally, in the top chamber 1103 of the exchanger 4, the spherical elements 42, in addition to receiving heat from the gas stream leaving the reactor 1, also store on their surface at least a portion of the SC suspended in the gas stream itself. Subsequently, in the bottom chamber 1105, the spherical elements 42 transfer heat to the gas to be treated, preheating it, and the spherical elements are brought from a temperature of approximately 1200°C / 1500°C / 2000°C at the inlet of the bottom chamber to another temperature of approximately 100°C-400°C at the end of the heat exchange step with the gas to be treated entering the reactor. Thus, at the end of this path, the spherical elements 42 are covered with a layer of SC and are at a high temperature. Under these conditions, the SC would present a significant fire risk if exposed to an oxidizing agent (e.g., air).

[0138] In order to avoid this risk, means for controlled transition of the oxidizing atmosphere (e.g. air) in terms of composition and temperature are provided downstream of the valve 1303 for regulating the flow of the spherical elements 42. Such means may consist of a system conceptually similar to that described for loading the spherical elements 42 entering the exchanger and comprising:

[0139] a first container 1204 which always receives the flow from the spherical element 42 of the valve 1303 ;

[0140] - a first sealing valve 1304 (open-closed) for allowing / blocking the spherical element 42 and the gas;

[0141] a second container 1205 provided with an internal atmosphere control system 1205 ′ and receiving the load of spherical elements 42 from the first container 1204 ;

[0142] - A second sealing valve 1305 (open-closed) for passing / blocking the spherical element 42 and the gas.

[0143] With this configuration, a method for emptying the spherical elements 42 in the exchanger can be performed, comprising the following steps:

[0144] 1. Close valve 1304 and fill container 1204 with an amount not less than the capacity of container 1205;

[0145] 2. Close valve 1305, open valve 1304, and fill container 1205;

[0146] 3. Valve 1304 is closed, and controlled atmospheric conditions (vacuum, inert atmosphere, etc.) are established in container 1205 by system 1205'; Note: This step preferably includes cooling the spherical element 42 in container 1205, which can be performed, for example, by a flow of cooled inert gas;

[0147] 4. Open valve 1305 to unload the contents of container 1205;

[0148] 5. Close valve 1305 and restore the controlled atmosphere within vessel 1205.

[0149] Thus, in the section above valve 1304, the presence of a controlled atmosphere and of a usable volume adapted to receive a constant flow from valve 1303 is ensured at any moment, while preventing air from entering the exchanger. Furthermore, it should be emphasized that in this process:

[0150] - container 1204 houses the spherical element 42 of variable level;

[0151] - The container 1205 alternates between a completely filled state (when it receives a charge from the container 1204) and a completely empty state (when the charge is poured out through the valve 1305).

[0152] Thereby, the spherical elements 42 can be effectively unloaded from the exchanger 4 at a safe temperature to prevent the SC from burning in the air in an uncontrolled manner.

[0153] There are other sequences that allow the same result to be achieved. For example, one could start with valve 1304 open and valve 1305 closed. When container 1205 is filled, valve 1304 is closed, and a gas management program is started to render the material in container 1205 inert. At the end, valve 1305 is opened to unload container 1205. Then, valve 1305 is closed and container 1205 is rendered inert. At this point, the system is ready to repeat the cycle.

[0154] Downstream of the valve 1305 , after a suitable step of cleaning the SC residues, it is possible to provide for the storage of the spherical elements 42 in air for their subsequent use in the exchanger 4 .

[0155] Furthermore, means can be provided for recycling the spherical elements 42 from the outlet to the inlet of the exchanger 4 in a controlled atmosphere, which means can include cooling, SC removal and SC recovery. In its second embodiment, the exchanger 4 can have a fixed bed structure consisting of at least two units 44 and 45 working in an alternative configuration (observe Figure 13 and 14 ).

[0156] In this embodiment, the heat exchange devices within units 44 and 45 can be based on solids with different shapes and compositions, such as spheres, saddles, foams, rings, honeycombs, etc., and made of ceramic materials, metal materials, metal oxides (such as DRI).

[0157] For example, the exchange device consists of ceramic spheres based on high-temperature resistant (>1200° C.) aluminum oxide, having a diameter comprised between 1 and 100 mm.

[0158] Typically, inside the cells 44 and 45 there is a static mass which is permeable to the passage of gas and which is able to exchange heat with the gas flowing through it.

[0159] In the first step ( Figure 13 ), the gas flow S2 generated by the reactor 1 at high temperature is passed through the unit 44 (which undergoes heating) to obtain a cooled gas flow S3; at the same time, the flow FG of the gas to be treated is passed through the unit 45, which is preheated at high temperature and transfers heat to the gas flowing through, causing it to cool itself. The gas leaves as the preheated gas flow S1 to be treated and is sent to the reactor 1 for pyrolysis.

[0160] In the second step ( Figure 14 ), the gas stream S2 produced by the reactor 1 at high temperature is deflected towards the unit 45, which now undergoes heating, thereby obtaining a cooled gas stream S3; at the same time, the stream FG of gas to be treated is now passed through the unit 44, which was heated at high temperature during the first step and now transfers heat to the gas flowing through, causing it to cool itself, and this gas leaves as preheated gas stream S1 to be treated and is sent to the reactor 1 for pyrolysis.

[0161] From the above description, it will be clear and obvious to a person skilled in the art that the configuration of the exchanger 4, although particularly suitable for connection to the reactor 1 shown in its different embodiments, can also be effectively used in combination with other types of reactors for producing hydrogen by pyrolysis at high temperatures, such as, for example, plasma arc reactors with electrodes fixed and / or oriented in any manner, in particular but not exclusively including plasma torches. The present invention also relates to an apparatus for the efficient production of hydrogen by pyrolysis of an input gas mixture containing gaseous hydrocarbons, wherein the apparatus comprises:

[0162] a reactor for heating and pyrolyzing an input gas mixture by an electric arc and thereby producing a produced output mixture in which the hydrogen concentration is greater than that in the input gas mixture and which contains a solid fraction comprising carbon;

[0163] a heat exchanger 4 for preheating the input gas mixture and for cooling the resulting output mixture; wherein the heat exchanger 4 also provides one or more heat exchange and storage elements 42, 44, 45, which store heat by cooling the resulting mixture leaving the reactor 1 and transfer heat successively or simultaneously by preheating the gas mixture entering the reactor 1.

[0164] Advantageously, the heat exchange and storage element 42 is composed of a plurality of elements of similar shape to one another, and the exchanger 4 comprises:

[0165] - A first chamber 1103, which provides

[0166] at least one upper inlet 1101 placed in the top of this first chamber for the heat exchange and storage element 42 to enter the exchanger 4,

[0167] at least one inlet 1110 of the mixture produced in the reactor 1, communicating with the outlet of the reactor 1, which allows the mixture to transfer heat to the heat exchange and storage element 42, causing it to cool itself,

[0168] at least one outlet 1120 of the gas mixture to the reactor 1, the temperature of which is lower than the temperature of the inlet,

[0169] The first chamber 1103 of the exchanger 4 communicates with a second chamber 1105 placed at a lower vertical level than the first chamber 1103, which in turn comprises

[0170] at least one upper inlet for the heat exchange and storage element 42 coming from the first chamber 1103,

[0171] at least one inlet 1130 for the inlet of the gas mixture to be treated, so that the heat exchange and storage element 42 transfers heat to the input gas mixture, heating it,

[0172] at least one outlet 1140 for the input gas mixture communicating with the inlet of the reactor 1,

[0173] at least one bottom outlet 1102 of the second chamber 1105 for the heat exchange and storage element 42 to leave the exchanger 4,

[0174] Therein, the heat exchange and storage element 42 is transferred from the first chamber 1103 to the second chamber 1105 by gravity.

[0175] Advantageously, the heat exchange and storage element 42 is composed of at least a first array 44 and a second array 45, which are permeable to the passage of gases entering and leaving the reactor 1, wherein in a first step, the gases leaving the reactor 1 flow through the first array 44, heating it, and the incoming gases flow through the second array 45, heating it itself; and in a second step, the two gas flows are reversed, so that the gas flow leaving the reactor 1 flows through the second array 45, heating it, and the incoming gases flow through the first array 44, heating it itself.

[0176] As can be understood from the preceding description, the arrangement of electrodes with a substantially vertical orientation and the possibility of instant and precise power regulation of the electrodes by means of the system for moving the electrodes themselves allow a very advantageous reactor 1 to be obtained that solves the specific problems of the prior art. Furthermore, this makes it possible to replace the electrodes in the reactor 1 significantly easier and more flexible, and to simplify the sealing system of the reactor to prevent oxygen penetration.

[0177] Furthermore, by the solution according to the invention, a maximization of the hydrogen yield, the injection of gases, in particular methane, in a zone at a uniform and controlled temperature, and an easy recycling of unconverted gases are achieved.

[0178] Furthermore, according to the invention, the possibility of partially separating the solid carbon within the reactor 1 itself is achieved.

[0179] Finally, the solution according to the invention allows heat recovery from the hot gas and reduces consumption.

[0180] The solution according to the invention further allows system integration of the pyrolysis reactor by recovering heat from the exiting hot products (gases and solids) and preheating the incoming gases.

[0181] This system integration allows particularly high efficiencies to be achieved, since, through the specific construction of the reactor and the exchanger, heat can be recovered not only from the gas but also at least partially from the solid carbon and can be effectively used to preheat the incoming gas.

[0182] The present invention has been described with respect to its preferred embodiments for purposes of illustration and not limitation, but it is anticipated that changes and / or modifications may be made by those skilled in the art without departing from the relevant scope of protection as defined in the appended claims.

Claims

1. An apparatus for efficiently producing hydrogen by pyrolysis of an input gas mixture containing gaseous hydrocarbons, the apparatus comprising: - a reactor (1) for heating and pyrolyzing the input gas mixture by means of an electric arc and thereby producing a produced output mixture in which the hydrogen concentration is greater than that in the input gas mixture and which contains a solid fraction comprising carbon; - a heat exchanger (4) for preheating the input gas mixture and cooling the resulting output mixture; the device is characterized in that - The reactor (1) comprises a containment structure (100) defining a reaction chamber (101), the containment structure being provided with controllable openings for an input (120) of the input gas mixture and an output (130) of the produced mixture; at least one electrode (200) passing through one or more holes in the containing structure (100), and a sealing element (150) between the hole and the at least one electrode (200) for preventing gas exchange between the inside and the outside, at least one conductive element (300), the at least one conductive element being at least partially disposed within the reaction chamber (101), wherein the at least one electrode (200) is movable along its axis (X) relative to the other electrodes (200) or relative to the conductive element (300), wherein the electric arc is formed between the one or more electrodes (200) and the conductive element (300); And among them, The heat exchanger (4) provides one or more heat exchange and storage elements (42, 44, 45), wherein The heat exchange and storage elements (42, 44, 45) store heat by cooling the produced mixture leaving the reactor (1) and transfer heat sequentially or simultaneously by preheating the gas mixture entering the reactor (1).

2. The device according to claim 1, wherein The input gas mixture includes gas produced from a renewable source.

3. The device according to claim 1, wherein The at least one electrode (200) is arranged with a substantially vertical axis (X).

4. The device according to claim 1, wherein The conductive element (300) is fixed relative to the containing structure (100).

5. The device according to one of the preceding claims, in, The conductive element (300) is completely within the reaction chamber (101).

6. The device according to one of the preceding claims, further comprising - a solid-gas separator (2) for separating the generated output mixture from solid and powder components therein; A gas-gas separator (3) for separating the resulting output mixture free of solid components into a mixture further enriched in hydrogen and a mixture consisting predominantly of other residual gases.

7. The device according to one of the preceding claims, wherein The heat exchange and storage element (42) is composed of a plurality of elements of similar shape to each other, and wherein the exchanger (4) comprises - A first chamber (1103) which provides at least one upper inlet (1101) placed in the top of the first chamber for admitting the heat exchange and storage element (42) into the exchanger (4), at least one inlet (1110) of the mixture produced in the reactor (1) and connected to the outlet of the reactor (1), so that the mixture transfers heat to the heat exchange and storage element (42) to cool itself, at least one outlet (1120) of the gas mixture to the reactor (1) has a temperature lower than the temperature of the inlet, The first chamber (1103) of the exchanger (4) is in communication with a second chamber (1105), the second chamber being placed at a lower vertical height than the first chamber (1103), which in turn comprises at least one upper inlet for said heat exchange, and a storage element (42) of heat from said first chamber (1103), at least one inlet (1130) for the input gas mixture to be treated, so that the heat exchange and storage element (42) transfers heat to the input gas mixture, heating it, at least one outlet (1140) for the input gas mixture communicating with the inlet of the reactor (1) at least one bottom outlet (1102) of the second chamber (1105), the at least one bottom outlet being used to discharge the heat exchange and storage element (42) from the exchanger (4), wherein the heat exchange and storage element (42) is transferred from the first chamber (1103) to the second chamber (1105) by gravity.

8. The apparatus according to claim 7, wherein The exchanger (4) comprises a transition region (1104) between the first chamber (1103) and the second chamber (1105), the transition region (1104) having a channel section for the heat exchange and storage element (42), the channel section being smaller than the channel sections of the first chamber (1103) and the second chamber (1105).

9. The apparatus according to claim 8, wherein The transition zone (1104) has a calibrated section so as to have a transverse dimension at least equal to about 10 times the average dimension of the heat exchange and storage element (42) and a length along the direction of movement of the heat exchange and storage element (42) at least equal to about 20 times the average dimension of the element (42).

10. Apparatus according to one of claims 7 to 9, wherein the exchanger (4) comprises sealing means (1201, 1202, 1203, 1204, 1205, 1301, 1302, 1304, 1305) vertically positioned upstream of the upper inlet of the first chamber (1103) and downstream of the bottom outlet of the second chamber (1105), the sealing means allowing the exchange and storage element to enter the first chamber (1103) and to leave the second chamber (1105) while preventing fluids, in particular gases, from entering and leaving the exchanger (4).

11. Apparatus according to one or more of claims 7 to 10, wherein: Downstream of the bottom outlet of the second chamber (1105), the exchanger comprises a regulating device (1303), for example of the rotary type, for regulating the flow of the exchange and storage element (42) placed at the bottom outlet of the second chamber.

12. The apparatus according to claim 11, wherein The regulating device (1303) regulates the movement of the heat exchange and storage element (42) so that all the channel sections of the element (42) in the exchanger (4) are always essentially filled with the element, so that the element never travels through a free fall section within the exchanger (4).

13. The apparatus of claim 12, further comprising - a first container (1201) of said exchange and storage element, - a first sealing valve (1301) (open-close) for allowing the spherical element (42) and the gas to pass / blocking the spherical element and the gas; a second container (1202) of the exchange and storage element (42), to which is connected an internal atmosphere control system (1202'), said system being connected to the second container (1202), which allows the creation of vacuum conditions and / or controlled atmosphere conditions, - a second sealing valve (1302) (open-closed) for allowing / blocking the passage of the exchange and storage element (42) and the gas; - a third container (1203) of the exchange and storage element (42), the third container being closed and directly connected to the exchanger (4), The elements are arranged sequentially and vertically above one another, and the third container is arranged above the exchanger (4).

14. The apparatus according to claim 12 or 13, further comprising a first container ( 1204 ) receiving the flow from the exchange and storage element ( 42 ) of the regulating valve ( 1303 ); a first sealing valve (1304) (open-closed) for allowing / blocking the passage of the exchange and storage element (42) and the gas; a second container ( 1205 ) provided with an internal atmosphere control system ( 1205 ′) and receiving the load of exchange and storage elements ( 42 ) from said first container ( 1204 ); a second sealing valve (1305) (open-closed) for allowing / blocking the passage of the exchange and storage element (42) and the gas, The elements (42) are arranged sequentially and vertically above one another, and the second sealing valve is arranged below the exchanger (4).

15. Apparatus according to one or more of claims 1 to 6, wherein The heat exchange and storage element (42) is composed of at least a first array and a second array (44, 45) which are permeable to the passage of the gas entering and leaving the reactor (1), wherein in a first step, the gas leaving the reactor (1) flows through the first array (44), heating it, and the incoming gas flows through the second array (45), heating it itself; And in a second step, the gas flow is reversed so that the gas flow leaving the reactor (1) flows through the second array (45), heating the second array, and the incoming gas flows through the first array (44), heating the gas itself.

16. A method for the efficient production of hydrogen by pyrolysis of a gas mixture containing gaseous hydrocarbons, the method being carried out in an apparatus according to any one of claims 1 to 15 and comprising: - a first preheating step, in which the gas mixture receives heat by contact with one or more previously heated heat storage elements; - a second step of heating by an electric arc, during which the gas mixture undergoes a pyrolysis reaction increasing the hydrogen concentration; - a third cooling step, wherein the gas mixture transfers heat to the one or more heat storage elements by contact, thereby heating the one or more heat storage elements prior to the first step.

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