Process for catalytic cracking of ammonia

Abstract

The present invention relates to the field of hydrogen production from catalytic cracking of ammonia. The present invention comprises a primary cracking path comprising one or more catalyst-containing reaction tubes disposed within a roasting-type ammonia cracking reactor; and a parallel cleavage path comprising one or more secondary ammonia cleavage reactors arranged in succession and fluidly connected to each other. The invention can be used for producing hydrogen from ammonia.

Description

Technical Field

[0001] The present invention relates to a method for producing hydrogen. More specifically, the present invention relates to a method for producing hydrogen by catalytic cracking of ammonia. Background Art

[0002] There has been a renewed interest in using hydrogen as a green, carbon-free fuel in various industrial settings. Hydrogen can be combusted to produce heat energy or electricity. Alternatively, hydrogen can be used to produce electrochemical energy in, for example, fuel cells.

[0003] Ammonia has received attention as a possible compound for storing and transporting hydrogen. Liquid ammonia has a higher hydrogen density than liquid hydrogen and can be transported using existing infrastructure already used for this purpose, such as the infrastructure used to transport ammonia in the agrochemical fertilizer industry.

[0004] Once the liquid ammonia is transported, it can be burned directly or converted to hydrogen through a cracking process.

[0005] The catalytic cracking of ammonia to hydrogen and nitrogen has been known for many years. The reaction can be depicted as follows:

[0006]

[0007] The ammonia cracking reaction is endothermic and can be effectively achieved by passing ammonia over a suitable catalyst in an externally heated catalyst-containing reaction tube disposed in a heating furnace. Such heating furnaces are known, for example, for steam reforming of natural gas or naphtha feedstocks.

[0008] In industrial processes for the catalytic cracking of ammonia, the gas produced by the ammonia cracking reaction is purified to produce a purified hydrogen stream and a waste stream. The waste gas contains residual hydrogen, residual ammonia, and nitrogen. The waste gas can be burned with an oxygen-containing gas to produce heat energy, which can be used to support the endothermic cracking reaction in the heating furnace.

[0009] However, when burned, the waste gas does not generate sufficient heat energy to sustain the ammonia cracking reaction in the heating furnace. This requires burning one or more supplementary fuel sources, such as ammonia, cracked ammonia gas, or an input fuel (e.g., a hydrocarbon, such as methane). Using supplementary fuels that contain process gases (e.g., pure ammonia and / or pure hydrogen) is not desirable and can affect the overall conversion rate of the process. Using an input hydrocarbon fuel (such as methane) produces undesirable carbon dioxide emissions.

[0010] There is still a need for an improved process for the catalytic cracking of ammonia. In particular, there is still a need for an improved process for the catalytic cracking of ammonia that maximizes the conversion rate of ammonia to produce hydrogen. Summary of the Invention

[0011] Accordingly, the present invention provides a method for catalytic cracking of ammonia, the method comprising providing:

[0012] A primary cracking path including one or more catalyst-containing reaction tubes disposed within a calcined ammonia cracking reactor; and

[0013] A parallel cracking path including one or more secondary ammonia cracking reactors arranged in series and fluidly connected to each other,

[0014] The method comprising the steps of:

[0015] Supplying a first ammonia stream to the primary cracking path;

[0016] Cracking ammonia in the first ammonia stream in the one or more catalyst-containing reaction tubes of the calcined ammonia cracking reactor to produce a first hydrogen-containing stream;

[0017] Supplying a second ammonia stream to the parallel cracking path;

[0018] Cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that further contains unreacted ammonia;

[0019] Withdrawing a second hydrogen-containing stream from the parallel cracking path;

[0020] Feeding the second hydrogen-containing stream to one or more purification units and increasing the hydrogen content of the second hydrogen-containing stream to produce a hydrogen-rich stream and a tail gas stream; and

[0021] Burning the tail gas stream with oxygen in the fuel combustion zone of the calcined ammonia cracking reactor to provide heat energy to support the cracking of ammonia in the one or more catalyst-containing reaction tubes, wherein the second hydrogen-containing stream contains 40 mol% to 75 mol% of H2.

[0022] It has been unexpectedly found that the method of the present invention has excellent hydrogen recovery and power efficiency. In particular, it has been unexpectedly found that providing a parallel cracking path according to the present invention, separating the tail gas from the resulting hydrogen-containing stream, and burning the tail gas in the fuel combustion zone can provide sufficient heat energy to support the endothermic ammonia cracking reaction in the calcined ammonia cracking reactor of the primary cracking path. In addition, it has been unexpectedly found that the method of the present invention can reduce or eliminate the need to use supplementary fuel to support the endothermic ammonia cracking reaction in the calcined ammonia cracking reactor.

[0023] Furthermore, the parallel cracking path of the present invention allows the use of a smaller calcined ammonia cracking reactor, thereby reducing the capital and operating costs of the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1A block flow diagram of a method according to the present invention is shown.

[0025] Figure 2 A schematic diagram of a compact reformer available from Johnson Matthey Davy Technologies Limited is shown. Detailed Description

[0026] Preferred and / or optional features of the present invention will now be described. Unless the context requires otherwise, any aspect of the present invention may be combined with any other aspect of the present invention. Unless the context requires otherwise, any preferred and / or optional feature of any aspect may be combined, individually or in combination, with any aspect of the present invention.

[0027] The method of the present invention includes providing a primary cracking path that includes one or more catalyst-containing reaction tubes disposed within a calcined ammonia cracking reactor.

[0028] Suitable calcined ammonia cracking reactors are known and may include a fuel combustion zone having a radiant section that includes one or more burners into which one or more fuel streams and an oxygen feed gas (such as air, oxygen-enriched air, or oxygen) are fed. The radiant section may include one or more catalyst-containing reaction tubes through which an ammonia stream passes. Combustion of one or more fuel streams in one or more burners in the fuel combustion zone generates thermal energy (such as radiant heat) for heating the one or more catalyst-containing reaction tubes. There may be dozens or hundreds of catalyst-containing reaction tubes in the radiant section. If desired, flue gas from the combustion of one or more fuel streams may be used downstream of the radiant section to preheat one or more feed streams in the convection section. Reactors including a radiant section (containing catalyst) with reaction tubes and a convection section for preheating the feed are known in steam methane reforming and may be applied to the present invention.

[0029] Alternatively, a calcined ammonia cracking reactor may be used in which the combustion of the one or more fuel streams in the fuel combustion zone is separated from the reactor including the catalyst-containing reaction tubes. Such a reactor is the compact reformer available from Johnson Matthey Davy Technologies Limited, the schematic diagram of which is shown in Figure 2 which.

[0030] The catalyst in the reaction tube containing the catalyst can be any ammonia cracking catalyst. For example, nickel catalysts and / or ruthenium catalysts can be used. The preferred catalyst is a nickel catalyst. The catalyst may comprise 3 wt% to 30 wt% nickel, preferably 8 wt% to 20 wt% nickel expressed as NiO, on a suitable refractory support such as alumina or metal aluminate. The catalyst can be in the form of granular units, which may include one or more through-holes, or can be a washcoat on a structured metal or ceramic catalyst. A particularly preferred catalyst is KATALCO RTM 27-2, which comprises 12% nickel expressed as NiO on cylindrical particles formed from a high surface area calcium aluminate support.

[0031] One or more reaction tubes containing the catalyst can suitably be formed from an iron-based alloy, a nickel-based alloy or a cobalt-based alloy. The iron-based alloy can be an iron-chromium-based alloy such as stainless steel, preferably 316 stainless steel, or a high-nickel steel such as those described in WO03 / 051771A1. Preferably, one or more reaction tubes containing the catalyst are formed from a nickel-based alloy or a cobalt-based alloy. More preferably, one or more reaction tubes containing the catalyst are formed from a cobalt-based alloy.

[0032] The method of the present invention comprises providing a parallel cracking path, which comprises one or more secondary ammonia cracking reactors arranged successively and fluidly connected to each other.

[0033] The one or more secondary ammonia cracking reactors can be fluidly connected to each other directly or indirectly.

[0034] The parallel cracking path of the present invention operates in parallel with the primary cracking path of the present invention. The parallel cracking path and the primary cracking path are not successive to each other; in other words, the cracked gas from the parallel cracking path or the primary cracking path cannot be fed as the gas to be cracked into the primary cracking path or the parallel cracking path respectively.

[0035] The type of reactor that can be used as the one or more secondary ammonia cracking reactors is not particularly limited. The one or more secondary ammonia cracking reactors can be adiabatic reactors, packed bed reactors, electrically heated reactors and / or gas calcined reactors. Preferably, the one or more secondary ammonia reactors are adiabatic reactors such as adiabatic packed bed reactors.

[0036] An adiabatic reactor includes a reactor in which no heat is transferred from the reactor to the second ammonia stream being fed into it. For example, an adiabatic reactor does not include a reactor that provides heat energy to the second ammonia stream.

[0037] The thermal energy required to support the cracking reaction in the one or more secondary ammonia cracking reactors can be provided by heating a second ammonia stream and / or by providing a secondary ammonia cracking reactor that provides thermal energy. Preferably, the thermal energy can be provided from a source external to the process (e.g., an input gas or input electricity).

[0038] For the avoidance of doubt, the secondary ammonia cracking reactor is used to crack ammonia to produce hydrogen and nitrogen.

[0039] The one or more secondary ammonia cracking reactors contain a catalyst. The catalyst can be any catalyst for the cracking of ammonia. The catalyst can suitably be any of the above-mentioned ones suitable for use with a calcined ammonia cracking reactor.

[0040] The advantage of providing a parallel cracking path is that additional ammonia can be cracked in the process without imposing a load on the calcined ammonia cracking reactor of the primary cracking path. In particular, providing a parallel cracking path including one or more secondary ammonia cracking reactors allows ammonia to be cracked under kinetically favorable conditions (e.g., where the ammonia stream has a high ammonia partial pressure but a low nitrogen and hydrogen partial pressure) without the need for a complex and expensive calcined ammonia cracking reactor. In addition, the tail gas produced by the purification of the hydrogen-containing stream withdrawn from the parallel cracking path provides additional thermal energy to support the cracking of ammonia in the calcined ammonia cracking reactor.

[0041] The method of the present invention includes the step of supplying a first ammonia stream to a primary cracking path.

[0042] The first ammonia stream can be sourced from any source. In a preferred method of the present invention, the first ammonia stream is produced by the catalytic combination of hydrogen and nitrogen. For example, the ammonia stream can be produced by the Haber-Bosch ammonia synthesis method. In a preferred method of the present invention, the first ammonia stream can be produced in an ammonia production facility located upstream of the ammonia cracking reactor. Alternatively, the first ammonia stream can be provided from an ammonia storage facility, an ammonia storage unit, an ammonia storage tank, or an ammonia pipeline.

[0043] The first ammonia stream can contain 90 mol% of ammonia or more, 95 mol% of ammonia or more, 97 mol% of ammonia or more, or 99 mol% of ammonia or more. The first ammonia stream can be substantially 100 mol% of ammonia. "Substantially 100 mol% of ammonia" means any other components that may be present as incidental impurities and may be present in an amount less than 1 mol%, less than 0.5 mol%, or less than 0.1 mol% of the first ammonia stream.

[0044] Before or after being fed to the primary cracking path, the first ammonia stream can be mixed with another ammonia-containing stream. For example, the first ammonia stream can be mixed with any process stream containing ammonia (such as a partially cracked ammonia stream and / or a tail gas stream).

[0045] In a preferred method of the present invention, the first ammonia stream can be heated before being supplied to the primary cracking path. In this case, the first ammonia stream is a heated first ammonia stream. Thus, the method of the present invention can include the step of heating the first ammonia stream. The first ammonia stream can be heated to a temperature greater than 350°C, greater than 400°C, greater than 450°C, greater than 500°C or greater than 550°C. The first ammonia stream can be heated to a temperature less than 1000°C, less than 950°C, less than 850°C, less than 750°C or less than 700°C. The first ammonia stream can be heated to a temperature in the range of 350°C to 1000°C, 400°C to 950°C, 450°C to 850°C or 500°C to 750°C (such as 550°C to 700°C).

[0046] The method of the present invention includes the step of cracking ammonia in the first ammonia stream in the one or more catalyst-containing reaction tubes of the calcined ammonia cracking reactor to produce a first hydrogen-containing stream.

[0047] The temperature of the first ammonia stream at the inlet of the one or more catalyst-containing reaction tubes can be in the range of 350°C to 1000°C, 400°C to 950°C, 450°C to 850°C or 500°C to 750°C (such as 550°C to 700°C). The temperature of the first hydrogen-containing stream leaving the one or more catalyst-containing reaction tubes will affect the equilibrium position of the cracking reaction and can be in the range of 500°C to 950°C. In the case of using a nickel catalyst in the one or more catalyst-containing reaction tubes, the temperature of the first hydrogen-containing stream leaving the one or more catalyst-containing reaction tubes can preferably be greater than about 700°C.

[0048] The inlet pressure of the one or more catalyst-containing reaction tubes will be set by the process flow design and can be in the range of 1 bar to 100 bar absolute pressure, preferably 10 bar to 90 bar absolute pressure (such as 31 bar to 51 bar absolute pressure).

[0049] The first hydrogen-containing stream contains H2. The first hydrogen-containing stream also contains nitrogen (N2) and may also contain residual ammonia (e.g., unreacted ammonia).

[0050] The first hydrogen-containing stream can contain 60 mol% or more of H2, 65 mol% or more of H2, 70 mol% or more of H2, 72 mol% or more of H2 or 73 mol% or more of H2. The first hydrogen-containing stream can contain up to 75 mol% or less of H2. For example, the first hydrogen-containing stream can contain 60 mol% to 75 mol% of H2. Preferably, the first hydrogen-containing stream contains 70 mol% to 75 mol% of H2, such as 72 mol% to 75 mol% of H2.

[0051] The first hydrogen-containing stream may comprise 20 mol% or more of N2, 21 mol% or more of N2, 22 mol% or more of N2, or 23 mol% or more of N2. The first hydrogen-containing stream may comprise up to 25 mol% or less of N2. For example, the first hydrogen-containing stream may comprise 20 mol% to 25 mol% of N2. Preferably, the first hydrogen-containing stream comprises 22 mol% to 25 mol% of N2, such as 23 mol% to 25 mol% of N2.

[0052] The first hydrogen-containing stream may comprise less than 20 mol% of NH3, less than 15 mol% of NH3, less than 10 mol% of NH3, less than 5 mol% of NH3, less than 1 mol% of NH3, or less than 0.1 mol% of NH3. Preferably, the first hydrogen-containing stream comprises less than 4 mol% of NH3, less than 2 mol% of NH3, less than 1 mol% of NH3, or less than 0.1 mol% of NH3.

[0053] Preferably, the first hydrogen-containing stream may comprise a balanced mixture of ammonia, hydrogen, and nitrogen. In other words, the first hydrogen-containing stream may comprise a mixture of ammonia, hydrogen, and nitrogen at partial pressures such that no additional hydrogen and nitrogen are produced from further cracking reactions. The balanced mixture may comprise 72 mol% to 75 mol% of H2, 23 mol% to 25 mol% of N2, and less than 4 mol% of NH3 (e.g., less than 1 mol% or less than 0.1 mol% of NH3).

[0054] The method of the present invention includes the step of supplying a second ammonia stream to a parallel cracking path.

[0055] The second ammonia stream may be obtained from any source. For example, the second ammonia stream may be obtained from the same or a different source as the first ammonia stream.

[0056] The second ammonia stream may comprise 90 mol% of ammonia or more, 95 mol% of ammonia or more, 97 mol% of ammonia or more, or 99 mol% of ammonia or more. The second ammonia stream may be substantially 100 mol% of ammonia. "Substantially 100 mol% of ammonia" means any other components that may be present as incidental impurities and may be present in an amount less than 1 mol%, less than 0.5 mol%, or less than 0.1 mol% of the second ammonia stream.

[0057] It may be preferred that the second ammonia stream is heated before or after being fed to the parallel cracking path. The second ammonia stream may be heated using an electric heater or by using waste heat or recovered heat from elsewhere in the process. Alternatively or in addition, the second ammonia stream may be heated by the one or more secondary ammonia cracking reactors (e.g., an electrically heated ammonia cracking reactor).

[0058] In a preferred method of the present invention, the second ammonia stream and the first ammonia stream can be heated together to produce a heated first ammonia stream and a heated second ammonia stream from the same process equipment. The heated first ammonia stream can be fed to a primary cracking path including a calcined ammonia cracking reactor, and the heated second ammonia stream can be fed to a parallel cracking path. For example, it may be preferred that the second ammonia stream is a portion of the first ammonia stream that has been heated to the temperature as described above. Thus, the method of the present invention can include the step of heating the first ammonia stream and the second ammonia stream in the same process equipment.

[0059] The temperature to which the second ammonia stream is heated can depend on the choice of catalyst in the subsequent first secondary ammonia cracking reactor and / or additional secondary cracking reactors. For example, when the first secondary ammonia cracking reactor uses a nickel-containing catalyst such as Katalco 27-2, the second ammonia stream is preferably heated to a temperature of 700 °C to 1000 °C, 750 °C to 900 °C, 800 °C to 850 °C. For example, when the first secondary ammonia cracking reactor uses a noble metal catalyst (e.g., ruthenium-based catalyst) such as Katalco 27-612, the second ammonia stream can be heated to a temperature of 450 °C to 650 °C, 500 °C to 600 °C or 525 °C to 575 °C (e.g., about 550 °C). Generally, the second ammonia stream can be heated to a temperature of 700 °C to 1000 °C.

[0060] The method of the present invention includes the step of cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that may also contain unreacted ammonia.

[0061] The inlet pressure of the one or more secondary ammonia cracking reactors can generally be in the range of 1 bar to 100 bar absolute pressure, preferably 10 bar to 90 bar absolute pressure, such as 31 bar to 51 bar absolute pressure. Before supplying the ammonia stream to the secondary ammonia cracking reactor, the pressure can be set (e.g., increased) by a pump or a compressor.

[0062] Typically, the cracked second ammonia stream exiting the first secondary ammonia cracking reactor of the one or more secondary ammonia cracking reactors will contain ammonia in an amount of 65 mol% to 85 mol%, such as 70 mol% to 80 mol%. Typically, the cracked second ammonia stream exiting the first secondary ammonia cracking reactor of the one or more secondary ammonia cracking reactors will contain hydrogen in an amount of 10 mol% to 20 mol%, such as 12.5 mol% to 17.5 mol%. Typically, the cracked second ammonia stream exiting the first secondary ammonia cracking reactor of the one or more secondary ammonia cracking reactors will contain nitrogen in an amount of 1 mol% to 10 mol%, such as 3 mol% to 8 mol%. As will be appreciated, in the case where more than one secondary ammonia cracking reactor is provided in parallel cracking paths, for each successive secondary ammonia cracking reactor through which the stream passes, the amounts of hydrogen and nitrogen in the cracked second ammonia stream will increase, while the amount of ammonia will decrease. As will also be appreciated, the amount of ammonia cracked will depend on the configuration of the secondary ammonia cracking reactor.

[0063] As will be appreciated, due to the endothermic nature of the ammonia cracking reaction, the temperature of the ammonia stream entering the secondary ammonia cracking reactor will be higher than the temperature of the cracked ammonia stream exiting the secondary ammonia cracking reactor.

[0064] The temperature of the cracked second ammonia stream after cracking ammonia in the secondary ammonia cracking reactor will depend on the choice of catalyst used in the secondary ammonia cracking reactor. Typically, when the secondary ammonia cracking reactor uses a nickel catalyst such as Katalco 27-2, after cracking in the secondary ammonia cracking reactor, the cracked second ammonia stream can have a temperature of 450 °C to 600 °C, such as 500 °C to 550 °C. Typically, when the secondary ammonia cracking reactor uses a noble metal catalyst (e.g., a ruthenium-based catalyst) such as Katalco 27-612, after cracking in the secondary ammonia cracking reactor, the cracked second ammonia stream can have a temperature of 350 °C to 500 °C, such as 400 °C to 450 °C.

[0065] The method of the present invention includes the step of withdrawing a second hydrogen-containing stream from the parallel cracking paths.

[0066] A second hydrogen-containing stream is produced after the ammonia cracking reaction in the one or more secondary ammonia cracking reactors of the parallel cracking paths. The second hydrogen-containing stream is withdrawn from the parallel cracking paths. For the avoidance of doubt, the second hydrogen-containing stream withdrawn from the parallel cracking paths can be the cracked second ammonia stream after it has undergone cracking in all of the secondary ammonia cracking reactors of the one or more secondary ammonia cracking reactors.

[0067] The second hydrogen-containing stream contains 40 mol% to 75 mol% of H₂. The second hydrogen-containing stream may contain 50 mol% or more of H₂ or 60 mol% or more of H₂. The second hydrogen-containing stream contains up to 75 mol% or less of H₂. For example, the second hydrogen-containing stream may contain 50 mol% to 75 mol% of H₂ or 60 mol% to 75 mol% of H₂.

[0068] The second hydrogen-containing stream may contain 20 mol% or more of N₂, 21 mol% or more of N₂, 22 mol% or more of N₂, or 23 mol% or more of N₂. The second hydrogen-containing stream may contain up to 25 mol% or less of N₂. For example, the second hydrogen-containing stream may contain 20 mol% to 25 mol% of N₂. Preferably, the second hydrogen-containing stream contains 22 mol% to 25 mo1% of N₂, such as 23 mol% to 25 mol% of N₂.

[0069] The second hydrogen-containing stream may contain less than 20 mol% of NH₃, less than 15 mol% of NH₃, less than 10 mol% of NH₃, less than 5 mol% of NH₃, less than 1 mol% of NH₃, or less than 0.1 mol% of NH₃. Preferably, the second hydrogen-containing stream contains less than 4 mol% of NH₃, less than 2 mol% of NH₃, less than 1 mol% of NH₃, or less than 0.1 mol% of NH₃.

[0070] Preferably, the second hydrogen-containing stream may contain a balanced mixture of ammonia, hydrogen, and nitrogen. In other words, the second hydrogen-containing stream may contain a mixture of ammonia, hydrogen, and nitrogen at partial pressures such that no additional hydrogen and nitrogen are produced from further cracking reactions. The balanced mixture may contain 72 mol% to 75 mol% of H₂, 23 mol% to 25 mol% of N₂, and less than 4 mol% of NH₃ (e.g., less than 1 mol% or less than 0.1 mol% of NH₃).

[0071] The method of the present invention includes the steps of feeding the second hydrogen-containing stream to one or more purification units and increasing the hydrogen content of the second hydrogen-containing stream to produce a hydrogen-rich stream and a tail gas stream.

[0072] The second hydrogen-containing stream is fed to one or more purification units, such as pressure swing adsorption units, to increase the H₂ content by separating H₂ from other components. In a preferred method of the present invention, the first hydrogen-containing stream from the primary cracking path and the second hydrogen-containing stream from the parallel cracking path may be fed to the one or more purification units to produce one or more enriched hydrogen-containing streams and one or more tail gas streams. In a preferred method of the present invention, the first hydrogen-containing stream and the second hydrogen-containing stream may be fed to the same purification unit or may each be fed to different purification units.

[0073] In cases where a first hydrogen-containing stream and a second hydrogen-containing stream are fed to the same purification unit, it should be understood that the hydrogen-rich stream can be recovered as a single hydrogen-rich stream from the purification unit. In cases where the first hydrogen-containing stream and the second hydrogen-containing stream are fed to different purification units, the hydrogen-rich streams can be obtained as multiple hydrogen-rich streams, which can optionally be mixed to form a single hydrogen-rich stream.

[0074] It may be preferred that, before feeding the first hydrogen-containing stream and / or the second hydrogen-containing stream to the one or more purification units, the first hydrogen-containing stream and / or the second hydrogen-containing stream are fed to a steam generation unit and / or a heat recovery zone. As will be understood by those skilled in the art, the steam generation unit and / or the heat recovery zone can be used to recover low or medium grade heat.

[0075] It may be preferred that both the first hydrogen-containing stream and the second hydrogen-containing stream comprise a balanced mixture of hydrogen, nitrogen and ammonia, as described above.

[0076] In the process of the present invention, the tail gas generated from the first hydrogen-containing stream and the second hydrogen-containing stream is combusted with oxygen to provide heat energy, thereby supporting the cracking of ammonia in the one or more catalyst-containing reaction tubes. The higher the hydrogen content of the first hydrogen-containing stream and / or the second hydrogen-containing stream, the higher the amount of hydrogen in the tail gas. Thus, unexpectedly, when both the first hydrogen-containing stream and / or the second hydrogen-containing stream comprise a relatively high hydrogen content (e.g., 40 mol% or higher, preferably a balanced mixture of hydrogen, nitrogen and ammonia), the overall hydrogen recovery rate of the process can be maximized with a relatively high power efficiency. Thus, it may be preferred that both the first hydrogen-containing stream and the second hydrogen-containing stream comprise a high hydrogen content (e.g., 40 mol% or higher, preferably a balanced mixture of hydrogen, nitrogen and ammonia), and the tail gas can comprise a composition as defined below.

[0077] The hydrogen-rich stream can comprise 70 mol% or more of H2, 75 mol% or more of H2, 80 mol% or more of H2, 85 mol% or more of H2 or 90 mol% or more of H2. The hydrogen-rich stream can comprise up to 100 mol% or less of H2. For example, the hydrogen-rich stream can comprise 70 mol% to 100 mol% of H2, 75 mol% to 100 mol% of H2, 80 mol% to 100 mol% of H2, 85 mol% to 100 mol% of H2 or 90 mol% to 100 mol% of H2. Preferably, the hydrogen-rich stream can comprise more than 90 mol% of H2, more than 95 mol% of H2, more than 98 mol% of H2 or more than 99 mol% of H2. More preferably, the hydrogen-rich stream can comprise more than 99.9 mol% of H2, more than 99.95 mol% of H2 or about 100 mol% of H2. Most preferably, the enriched hydrogen-containing stream can comprise more than 99.95 mol% of H2 or about 100 mol% of H2.

[0078] The hydrogen-rich stream can be further purified to produce a purified hydrogen product. The hydrogen-rich stream can have a purity high enough to serve as the purified hydrogen product.

[0079] In cases where the first hydrogen-containing stream and the second hydrogen-containing stream are fed to the same purification unit, it should be understood that the tail gas stream can be recovered as a single tail gas stream. In cases where the first hydrogen-containing stream and the second hydrogen-containing stream are fed to different purification units, the tail gas stream can be obtained as multiple tail gas streams, which can optionally be mixed to form a single tail gas stream.

[0080] The tail gas stream can contain nitrogen (N2), ammonia, and hydrogen (H2). The composition of the tail gas stream will depend on the configuration of the primary cracking path and the parallel cracking path and the composition of the hydrogen-containing stream from which it is being withdrawn.

[0081] Typically, the tail gas stream can contain 20 mol% to 95 mol% of N2, 45 mol% to 85 mol% of N2, or 65 mol% to 80 mol% of N2.

[0082] Typically, the tail gas stream can contain 3 mol% to 10 mol% of ammonia, 3.2 mol% to 7 mol% of ammonia, or 3.3 mol% to 5 mol% of ammonia.

[0083] Typically, the tail gas stream can contain 10 mol% to 70 mol% of H2, such as 20 mol% to 50 mol% of H2. It can be preferred that the tail gas stream contains 15 mol% to 40 mol% of H2, 20 mol% of H2 to 35 mol% of H2, or 22 mol% of H2 to 30 mol% of H2.

[0084] The method of the present invention includes the steps of combusting the tail gas stream with oxygen in the fuel combustion zone of a calcined ammonia cracking reactor to provide heat energy to support the cracking of ammonia in the one or more catalyst-containing reaction tubes.

[0085] The oxygen for combusting the one or more tail gas streams can suitably be or include air, compressed air, oxygen-enriched air, oxygen, oxygen and an inert gas such as nitrogen.

[0086] As described above, the fuel combustion zone can be within the calcined ammonia cracking reactor or can be within a separate vessel for combustion that is in fluid connection with the calcined ammonia cracking reactor.

[0087] In a preferred method of the present invention, the parallel cracking path can include providing two or more, three or more, four or more, or five or more secondary ammonia cracking reactors arranged in succession.

[0088] In the case where two or more secondary ammonia cracking reactors are provided, a second ammonia stream is supplied to each successively arranged secondary ammonia cracking reactor to produce a cracked second ammonia stream in each case. As the cracked second ammonia stream passes through each successive secondary ammonia cracking reactor, additional ammonia is cracked and the composition of the second ammonia stream is changed. The term "cracked second ammonia stream" is used to refer to a second ammonia stream that has passed through at least one secondary ammonia cracking reactor and the ammonia in the stream has been cracked.

[0089] The total number of secondary ammonia cracking reactors that can be present in parallel cracking paths is not particularly limited and will depend on the desired composition of the second hydrogen-containing stream withdrawn from the parallel cracking paths, the catalyst used, and the temperature of the second ammonia stream and / or the cracked second ammonia stream. Preferably, a sufficient number of secondary ammonia cracking reactors are provided such that the second hydrogen-containing stream is withdrawn from the parallel cracking paths as a balanced mixture, as described above.

[0090] Thus, the parallel cracking paths preferably include two or more, three or more, four or more, or five or more secondary ammonia cracking reactors arranged successively and in fluid communication with each other. Thus, the method of the present invention can include the steps of supplying the cracked second ammonia stream to the second, third, fourth, and / or fifth secondary ammonia cracking reactors of the parallel cracking paths.

[0091] The catalysts used in each of the one or more secondary ammonia cracking reactors can be the same as or different from each other.

[0092] In a preferred method of the present invention, the temperature of the cracked second ammonia stream leaving any one secondary ammonia cracking reactor is high enough such that the cracking of ammonia occurs in a subsequent secondary ammonia cracking reactor without the need for an intermediate reheating step.

[0093] Thus, the method of the present invention can include the step of directly transferring the cracked second ammonia stream to one or more subsequent secondary ammonia crackings without an intermediate reheating step.

[0094] In a preferred method of the present invention, the parallel cracking paths include two or more secondary ammonia cracking reactors arranged successively and in fluid connection with each other.

[0095] In a preferred embodiment of the present invention, the first secondary ammonia cracking reactor of the two or more secondary ammonia cracking reactors can contain a catalyst that functions at a high temperature (e.g., a catalyst that catalyzes the cracking of ammonia at a temperature of 700 °C to 1000 °C), and the second secondary ammonia cracking reactor of the secondary ammonia cracking reactors can contain a catalyst that functions at a lower temperature (e.g., a catalyst that catalyzes the cracking of ammonia at a temperature of 450 °C to 650 °C).

[0096] In a more preferred embodiment of the present invention, the first secondary ammonia cracking reactor among the two or more secondary ammonia cracking reactors may comprise a nickel-containing catalyst, and the second secondary ammonia cracking reactor among the secondary ammonia cracking reactors may comprise a noble metal-containing catalyst (e.g., a ruthenium-based catalyst). Preferably, in this configuration, the cracked second ammonia stream is transferred from the first secondary ammonia cracking reactor among the two or more secondary ammonia cracking reactors to the second secondary ammonia cracking reactor among the two or more secondary ammonia cracking reactors without an intermediate heating step.

[0097] The advantages of the present invention are that two secondary ammonia cracking reactors arranged successively and containing different catalysts can be provided, and ammonia cracking can be carried out over a wide temperature range by utilizing the different activities of the catalysts.

[0098] The parallel cracking paths may include one or more heaters.

[0099] Heaters can be provided to increase the temperature of the cracked second ammonia stream and provide sufficient thermal energy for the ammonia in the cracked second ammonia stream to undergo cracking.

[0100] The one or more heaters can be powered or fueled by a hot gas (such as a hydrocarbon gas, hydrogen or ammonia) or by electricity. Preferably, the one or more heaters are powered or fueled from a source external to the process (e.g., an input gas or input electricity).

[0101] The one or more heaters are preferably electric heaters. Preferably, the one or more heaters are electric heaters that draw electricity generated outside the process. Even more preferably, the one or more heaters are electric heaters that draw electricity generated from renewable sources (e.g., from wind, solar, hydroelectric or tidal sources).

[0102] The one or more heaters can be part of the one or more secondary ammonia cracking reactors. For example, the one or more heaters can form part of an electrically heated packed bed reactor.

[0103] In a preferred method of the present invention, the one or more secondary ammonia cracking reactors can be adiabatic reactors, and thermal energy for supporting the cracking reaction in the one or more secondary ammonia cracking reactors can be provided by heating the second ammonia stream using one or more heaters.

[0104] The method of the present invention may include the step of reheating the cracked second ammonia stream using a heater (e.g., an electric heater) to produce a reheated cracked second ammonia stream.

[0105] The method of the present invention may include reheating the cracked second ammonia stream and feeding it to one or more subsequent secondary ammonia cracking reactors. The step of reheating the cracked second ammonia stream has the advantage that it can provide subsequent secondary ammonia cracking reactors to convert the unreacted ammonia in the cracked second ammonia stream. The method of the present invention may include providing a heater (e.g., an electric heater) disposed upstream of the secondary ammonia cracking reactor.

[0106] Thus, the method may include the steps of reheating the cracked second ammonia stream using a heater (e.g., an electric heater) to produce a reheated cracked second ammonia stream, and supplying the reheated cracked second ammonia stream to one or more subsequent secondary ammonia cracking reactors.

[0107] The temperature to which the cracked second ammonia stream is reheated will depend on the nature of the catalyst used in the one or more secondary ammonia cracking reactors. For example, when the secondary ammonia cracking reactor uses a nickel-containing catalyst such as Katalco 27-2, the cracked second ammonia stream can be reheated to a temperature of 700°C to 1000°C, 750°C to 900°C, or 800°C to 850°C. For example, when the one or more secondary ammonia cracking reactors use a noble metal catalyst (e.g., a ruthenium-based catalyst) such as Katalco 27-612, the cracked second ammonia stream can be reheated to a temperature of 450°C to 650°C, 500°C to 600°C, or 525°C to 575°C (e.g., about 550°C). Generally, the cracked second ammonia stream can be reheated to a temperature of 700°C to 1000°C.

[0108] The advantage of using a heater powered or fueled from a source external to the process in reheating the second ammonia stream is that it reduces or eliminates the consumption of raw materials (e.g., pure ammonia) or product materials (e.g., pure hydrogen) that provide heat energy for the ammonia cracking reaction. Particularly advantageously, one or more heaters are electric heaters. Although electric heaters require the use of electrical energy, it has surprisingly been found that the overall power efficiency of the method of the present invention is higher than the overall power efficiency when no electric heater and secondary ammonia cracking reactor are employed.

[0109] The need to provide a heater (e.g., an electric heater) at any point in the method of the present invention will depend on the number of secondary ammonia cracking reactors used, the nature of the catalyst in each secondary ammonia cracking reactor disposed in the secondary ammonia cracking reactor, the temperature of the second ammonia stream and / or the cracked second ammonia stream in each secondary ammonia cracking reactor in the secondary ammonia cracking reactor after the cracking reaction, and the desired composition of the second hydrogen-containing stream withdrawn from the parallel ammonia cracking paths.

[0110] In a preferred method of the present invention, the parallel cracking path includes three or more secondary ammonia cracking reactors, and the method comprises the following steps:

[0111] Supplying a second ammonia stream to the parallel cracking path;

[0112] Cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that still contains unreacted ammonia; and

[0113] Reheating the cracked second ammonia stream to a temperature of 700 °C to 1000 °C using a heater (e.g., an electric heater) to produce a reheated cracked second ammonia stream;

[0114] Supplying the reheated cracked second ammonia stream to a secondary ammonia cracking reactor containing a nickel-containing catalyst (e.g., Katalco 27-2); and

[0115] Optionally, reheating the cracked second ammonia stream to a temperature of 700 °C to 1000 °C using a heater (e.g., an electric heater) to produce a reheated cracked second ammonia stream; and

[0116] Supplying the reheated cracked second ammonia stream to a secondary ammonia cracking reactor containing a nickel-containing catalyst (e.g., Katalco 27-2).

[0117] In a preferred method of the present invention, the parallel cracking path includes three or more secondary ammonia cracking reactors, and the method comprises the following steps:

[0118] Supplying a second ammonia stream to the parallel cracking path;

[0119] Cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that still contains unreacted ammonia;

[0120] Reheating the cracked second ammonia stream to a temperature of 700 °C to 1000 °C using a heater (e.g., an electric heater) to produce a reheated cracked second ammonia stream;

[0121] Supplying the reheated cracked second ammonia stream to a secondary ammonia cracking reactor containing a nickel-containing catalyst (e.g., Katalco 27-2);

[0122] Supplying the cracked second ammonia stream directly (i.e., without an intermediate reheating step) to a secondary ammonia cracking reactor containing a noble metal-containing catalyst (e.g., Katalco 27-612);

[0123] Reheat the cracked second ammonia stream to a temperature of 700 °C to 1000 °C using a heater (e.g., an electric heater); and

[0124] Supply the cracked second ammonia stream to a secondary ammonia cracking reactor containing a nickel-containing catalyst (e.g., Katalco 27-2).

[0125] In certain methods of the present invention, in addition to the tail gas stream, one or more fuel streams may be combusted with oxygen in a fuel combustion zone such that the combustion provides the thermal energy to support the endothermic ammonia cracking reaction in the ammonia cracking reactor. Thus, the methods of the present invention may include the step of combusting one or more fuel streams with oxygen in a fuel combustion zone to provide thermal energy to a calcining ammonia cracking reactor.

[0126] Preferably, one or more fuel sources may include carbon-free fuel sources (e.g., hydrogen or ammonia). It may be preferred that one or more fuel sources do not include carbon-containing fuel sources.

[0127] The one or more fuel streams may include one or more of the following: hydrogen, natural gas, methane, refinery off-gas, biogas, tail gas from a hydrogen purification unit, the fuel portion of a first hydrogen-containing stream or a second hydrogen-containing stream, or the fuel portion of an enriched hydrogen-containing stream from the one or more purification units.

[0128] As used herein, the term "fuel portion" is used to refer to a portion of a stream (e.g., a hydrogen-containing stream, an enriched hydrogen-containing stream, or a first ammonia stream or a second ammonia stream) that is used as a fuel source. It is not used to refer to a portion of a stream used for the ammonia cracking reaction.

[0129] In certain methods of the present invention, the one or more fuel streams may include a hydrogen-containing fuel stream. The hydrogen-containing fuel stream may be the fuel portion of a hydrogen-containing stream produced from an ammonia cracking reactor. The hydrogen-containing fuel stream may be the fuel portion of an enriched hydrogen-containing stream from a purification unit. Thus, the methods of the present invention may include the steps of withdrawing the fuel portion of a hydrogen-containing stream or the fuel portion of a hydrogen-rich stream and combusting the fuel portion of the hydrogen-containing stream or the fuel portion of the enriched hydrogen-containing stream with oxygen in a fuel combustion zone to provide the thermal energy to support the endothermic ammonia cracking reaction in the ammonia cracking reactor.

[0130] For the avoidance of doubt, the one or more fuel streams may be mixed with each other and / or with the tail gas stream prior to combustion, or each stream may be mixed at a single combustion point.

[0131] Combustion of the exhaust gas stream and optionally the one or more fuel streams in the fuel combustion zone generates flue gas, which can be recovered from the calcined ammonia cracking reactor. The flue gas can be cooled in one or more cooling stages and can undergo one or more purification stages before being discharged to the atmosphere. The one or more cooling stages can include recovering thermal energy from the flue gas. For example, the one or more cooling stages can include a preheating stage for one or more of the reactants used in the calcined and / or secondary ammonia cracking reactor and / or for generating steam. The one or more purification stages can include a selective catalytic reduction or SCR stage, in which nitrogen oxides react with ammonia to form nitrogen and water vapor. Any flue gas selective catalytic reduction technology can be used.

[0132] In a preferred method of the present invention, the method includes providing:

[0133] A primary cracking path that includes one or more catalyst-containing reaction tubes disposed within a calcined ammonia cracking reactor; and

[0134] A parallel cracking path that includes one or more secondary ammonia cracking reactors arranged in series and fluidly connected to each other,

[0135] The method includes the following steps:

[0136] Supplying a first ammonia stream to the primary cracking path;

[0137] Cracking ammonia in the first ammonia stream in the one or more catalyst-containing reaction tubes of the calcined ammonia cracking reactor to produce a first hydrogen-containing stream;

[0138] Supplying a second ammonia stream to the parallel cracking path;

[0139] Cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that also contains unreacted ammonia;

[0140] Removing a second hydrogen-containing stream from the parallel cracking path;

[0141] Feeding the second hydrogen-containing stream and optionally the first hydrogen-containing stream to one or more purification units and increasing the hydrogen content of the second hydrogen-containing stream and optionally the first hydrogen-containing stream to produce a hydrogen-rich stream and an exhaust gas stream; and

[0142] Burning the exhaust gas stream with oxygen in the fuel combustion zone of the calcined ammonia cracking reactor to provide thermal energy to support the cracking of ammonia in the one or more catalyst-containing reaction tubes.

[0143] In a preferred method of the present invention, the method includes providing:

[0144] A primary cracking path, which includes one or more catalyst-containing reaction tubes disposed within a calcined ammonia cracking reactor; and

[0145] A parallel cracking path, which includes one or more secondary ammonia cracking reactors arranged in series and fluidly connected to each other,

[0146] The method further includes the following steps:

[0147] Supplying a first ammonia stream to the primary cracking path;

[0148] Cracking ammonia in the first ammonia stream in the one or more catalyst-containing reaction tubes of the calcined ammonia cracking reactor to produce a first hydrogen-containing stream;

[0149] Supplying a second ammonia stream to the parallel cracking path;

[0150] Cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that also contains unreacted ammonia;

[0151] Reheating the cracked second ammonia stream using a heater (e.g., an electric heater) to produce a reheated cracked second ammonia stream;

[0152] Supplying the reheated cracked second ammonia stream to one or more subsequent secondary ammonia cracking reactors;

[0153] Cracking ammonia in the reheated cracked second ammonia stream in the one or more subsequent secondary ammonia cracking reactors;

[0154] Withdrawing a second hydrogen-containing stream from the parallel cracking path;

[0155] Feeding the second hydrogen-containing stream and optionally the first hydrogen-containing stream to one or more purification units and increasing the hydrogen content of the second hydrogen-containing stream and optionally the first hydrogen-containing stream to produce a hydrogen-rich stream and a tail gas stream; and

[0156] Burning the tail gas stream with oxygen in the fuel combustion zone of the calcined ammonia cracking reactor to provide heat energy to support the cracking of ammonia in the one or more catalyst-containing reaction tubes,

[0157] The present invention will now be described in further detail in the following non-limiting embodiments and with reference to the accompanying drawings.

[0158] Figure 1 A block flow diagram illustrating the method according to the present invention. Figure 1An ammonia stream (1) being fed into a heating unit (2) is shown, and the heating unit heats the ammonia stream to produce a first ammonia stream (101) and a second ammonia stream (102a). The first ammonia stream (101) is supplied to a primary cracking path (14). The primary cracking path (14) includes one or more catalyst-containing reaction tubes disposed within a calcined ammonia cracking reactor (3). Ammonia in the first ammonia stream is cracked in the one or more catalyst-containing reaction tubes of the calcined ammonia cracking reactor (3) to produce a first hydrogen-containing stream (103). The second ammonia stream (102a) is supplied to a parallel ammonia cracking path (13). The parallel ammonia cracking path includes one or more secondary ammonia cracking reactors (4, 6, 8) arranged successively and fluidly connected to each other, and electric heaters (5, 7). The second ammonia stream (102a) is supplied to a first secondary ammonia cracking reactor (4). Ammonia in the second ammonia stream (102a) is cracked in the first secondary ammonia cracking reactor (4) to produce a cracked second ammonia stream (104a) that also contains unreacted ammonia. At this stage, the temperature of the cracked second ammonia stream (104a) will be lower than the temperature of the ammonia stream (102a) entering the first secondary ammonia cracking reactor (4). The second ammonia stream (104a) is fed into an electric heater (5), where the second ammonia stream is reheated. The reheated cracked second ammonia stream (102b) is supplied to a second secondary ammonia cracking reactor (6), where the unreacted ammonia is cracked and a cracked second ammonia stream (104b) is obtained. The cracked second ammonia stream (104b) is fed into a further electric heater (7), where the cracked second ammonia stream is reheated. The reheated cracked second ammonia stream (102c) is supplied to a third secondary ammonia cracking reactor (8), where the unreacted ammonia is cracked, and a second hydrogen-containing stream (108) is obtained and withdrawn from the parallel ammonia cracking path (13). The second hydrogen-containing stream can be a cracked ammonia gas stream at or near equilibrium. The first hydrogen-containing stream (103) and the second hydrogen-containing stream (108) are fed into a heat recovery unit (9), where heat is recovered. The first hydrogen-containing stream (103) and the second hydrogen-containing stream (103) are mixed and fed as a single stream (109) into a purification unit (10). The purification unit (10) increases the hydrogen content of the hydrogen-containing stream (109) and produces a hydrogen-rich stream (111) and a tail gas stream (110). The hydrogen-rich stream (111) can be recovered as a purified hydrogen product (11). The tail gas (110) is supplied to the calcined ammonia cracking reactor (3) and burned with oxygen from an oxygen-containing feed (112) in the fuel combustion zone of the calcined ammonia cracking reactor (3) to provide heat energy, thereby supporting the cracking of ammonia in the one or more catalyst-containing reaction tubes.

[0159] Embodiment

[0160] The ammonia cracking method as described above and Figure 1 shown is compared with a method using only a calcination reactor. The respective hydrogen recovery rates and power efficiencies are compared. Both methods are based on the cracking of an ammonia stream containing 50 tons per hour of ammonia.

[0161] Multi-bed cracker (according to the present invention)

[0162] 58.3% of the ammonia is directed to the secondary bed stream, 40.0% is directed to the calcination cracker, and 1.5% is directed to fuel. 28.8 MW of electrical energy is input. For NO x removal, 0.2% to SCR

[0163] Calcination-only cracker (comparison)

[0164] 85% of the ammonia is directed to the calcination cracker, and 14.6% is directed to fuel. 1.7 MW of electrical energy is generated via a steam turbine for output.

[0165] The overall recovery rates are shown in Table 1.

[0166] Electric and calcination (according to the present invention) Calcination-only (comparison) Hydrogen recovery rate * 86.69％ 74.8％ Power efficiency ** 89.42％ 86.4％

[0167] Table 1

[0168] * The hydrogen recovery rate is defined as:

[0169]

[0170] ** The power efficiency is defined as:

[0171]

[0172] The method of the present invention using a secondary ammonia cracking reactor arranged in series recovers significantly more hydrogen than a method including only a calcination ammonia cracking reactor. In addition, the increased hydrogen recovery rate of the method of the present invention is achieved with a higher power efficiency.

Claims

1. A method for the catalytic cracking of ammonia, the method comprising providing: Primary cracking path, the primary cracking path includes one or more catalyst-containing reaction tubes disposed within a calcined ammonia cracking reactor; And Parallel cracking paths, the parallel cracking paths comprising one or more secondary ammonia cracking reactors arranged successively and fluidly connected to each other, The method comprising the steps of: Supplying a first ammonia stream to the primary cracking path; Cracking ammonia in the first ammonia stream in the one or more catalyst-containing reaction tubes of the calcined ammonia cracking reactor to produce a first hydrogen-containing stream; Supplying a second ammonia stream to the parallel cracking paths; Cracking ammonia in the second ammonia stream in the one or more secondary ammonia cracking reactors to produce a cracked second ammonia stream that also contains unreacted ammonia; Removing a second hydrogen-containing stream from the parallel cracking paths; Feeding the second hydrogen-containing stream to one or more purification units and increasing the hydrogen content of the second hydrogen-containing stream to produce a hydrogen-rich stream and a tail gas stream; and Burning the tail gas stream with oxygen in the fuel combustion zone of the calcined ammonia cracking reactor to provide heat energy to support the cracking of ammonia in the one or more catalyst-containing reaction tubes, Wherein the second hydrogen-containing stream contains 40 mol% to 75 mol% of H2.

2. The method according to claim 1, wherein the first ammonia stream contains 90 mol% or more of ammonia, 95 mol% or more of ammonia, 97 mol% or more of ammonia, 99 mol% or more of ammonia or substantially 100 mol% of ammonia.

3. The method according to claim 1 or claim 2, wherein the second ammonia stream can contain 90 mol% or more of ammonia, 95 mol% or more of ammonia, 97 mol% or more of ammonia, 99 mol% or more of ammonia or substantially 100 mol% of ammonia.

4. The method according to any one of the preceding claims, the method comprising the following steps: Heating the first ammonia stream to a temperature of 350 °C to 1000 °C, 400 °C to 950 °C, 450 °C to 850 °C or 500 °C to 750 °C.

5. The method according to any one of the preceding claims, wherein the inlet pressure of the one or more catalyst-containing reaction tubes is in the range of 1 bar to 100 bar absolute pressure, preferably 10 bar to 90 bar absolute pressure, more preferably 31 bar to 51 bar absolute pressure.

6. The method according to any one of the preceding claims, wherein the second ammonia stream and the first ammonia stream are the same, and the second ammonia stream and the first ammonia stream are heated together, wherein the heated first ammonia stream and the heated second ammonia stream are obtained from the same process equipment.

7. The method according to any one of the preceding claims, wherein the first hydrogen-containing stream contains 60 mol% to 75 mol% of H2, 70 mol% to 75 mol% of H2 or 72 mol% to 75 mol% of H2.

8. The method according to any one of the preceding claims, wherein the second ammonia stream is heated to a temperature of 700 °C to 1000 °C, 750 °C to 900 °C or 800 °C to 850 °C before or after being fed to the parallel cracking paths.

9. The method according to any one of claims 1 to 7, wherein the second ammonia stream is heated to a temperature of 450 °C to 650 °C, 500 °C to 600 °C or 525 °C to 575 °C before or after being fed to the parallel cracking path.

10. The method according to any one of the preceding claims, wherein the second hydrogen-containing stream comprises 50 mol% to 75 mol% of H2 or 60 mol% to 75 mol% of H2.

11. The method according to any one of the preceding claims, wherein the hydrogen-rich stream comprises 70 mol% to 100 mol% of H2, 75 mol% to 100 mol% of H2, 80 mol% to 100 mol% of H2, 85 mol% to 100 mol% of H2 or 90 mol% to 100 mol% of H2.

12. The method according to any one of the preceding claims, wherein the tail gas stream comprises 3 mol% to 10 mol% of ammonia, 3.2 mol% to 7 mol% of ammonia or 3.3 mol% to 5 mol% of ammonia.

13. The method according to any one of the preceding claims, wherein the tail gas stream comprises 10 mol% to 70 mol% of H2 or 20 mol% to 50 mol% of H2.

14. The method according to any one of the preceding claims, wherein the first hydrogen-containing stream comprises 72 mol% to 75 mol% of H2, 23 mol% to 25 mol% of N2 and less than 4 mol% of NH3.

15. The method according to any one of the preceding claims, wherein the second hydrogen-containing stream comprises 72 mol% to 75 mol% of H2, 23 mol% to 25 mol% of N2 and less than 4 mol% of NH3.

16. The method according to any one of the preceding claims, wherein the parallel cracking path comprises two or more, three or more, four or more or five or more secondary ammonia cracking reactors arranged successively and in fluid communication with each other.

17. The method according to claim 16, wherein the first secondary ammonia cracking reactor among the two or more secondary ammonia cracking reactors comprises a nickel-containing catalyst, and the second secondary ammonia cracking reactor among the secondary ammonia cracking reactors comprises a noble metal-containing catalyst.

18. The method according to claim 17, wherein the cracked second ammonia stream is transferred from the first secondary ammonia cracking reactor among the two or more secondary ammonia cracking reactors to the second secondary ammonia cracking reactor among the two or more secondary ammonia cracking reactors without an intermediate heating step.

19. The method according to any one of the preceding claims, wherein the parallel cracking path comprises one or more heaters, preferably one or more electric heaters.

20. The method according to claim 19, wherein the method comprises the following steps: Reheating the cracked second ammonia stream using a heater to produce a reheated cracked second ammonia stream.

21. The method according to claim 20, wherein the method comprises the following steps: Feeding the reheated cracked second ammonia stream to one or more subsequent secondary ammonia cracking reactors.

22. The method according to claim 21, wherein the cracked second ammonia stream is reheated to a temperature of from 700 °C to 1000 °C, from 750 °C to 900 °C or from 800 °C to 850 °C.

23. The method according to claim 21, wherein the second ammonia stream is reheated to a temperature of from 450 °C to 650 °C, from 500 °C to 600 °C or from 525 °C to 575 °C.

24. The method according to any one of the preceding claims, wherein the first hydrogen-containing stream and / or the second hydrogen-containing stream comprises a balanced mixture of hydrogen, nitrogen and ammonia.

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