Process for catalytic decomposition of ammonia

Abstract

The present invention relates to the field of hydrogen production from the catalytic cracking of ammonia. The invention includes a primary cracking pathway comprising one or more catalyst-containing reactor tubes disposed within a combustion ammonia cracking reactor, and a parallel cracking pathway comprising one or more secondary ammonia cracking reactors disposed in series and fluidly connected to one another. The invention can be used to produce hydrogen from ammonia.

Description

[Technical Field]

[0001] The present invention relates to a process for producing hydrogen gas. More particularly, the present invention relates to a process for producing hydrogen gas by catalytic decomposition of ammonia. [Background technology]

[0002] There is renewed interest in using hydrogen as an environmentally friendly, carbon-free fuel in various industrial settings. Hydrogen can be burned to produce thermal energy or electricity. Alternatively, hydrogen can be used to generate electrochemical energy, for example, in fuel cells.

[0003] Ammonia has attracted interest as a potential compound for the storage and transport of hydrogen. Liquid ammonia has a higher hydrogen density than liquid hydrogen and can be transported using existing infrastructure already in use for this purpose, such as that used to transport ammonia in the pesticide and fertilizer industry.

[0004] After being transported, the liquid ammonia can be combusted directly or converted to hydrogen by a cracking process.

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

[0006]

number

[0007] The ammonia decomposition reaction is endothermic and can be effectively accomplished by passing ammonia over a suitable catalyst in externally heated catalyst-containing reactor tubes placed within a furnace. For example, such furnaces are known for steam reforming of natural gas or naphtha feedstocks.

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

[0009] However, when combusted, the waste gas does not generate enough heat energy to sustain the ammonia decomposition reaction in the furnace. This requires the combustion of one or more supplemental fuel sources, such as ammonia, cracked ammonia gas, or an externally introduced fuel (e.g., a hydrocarbon, such as methane). The use of supplemental fuels, including process gases (e.g., pure ammonia and / or pure hydrogen), is undesirable and can affect the overall conversion of the process. The use of externally introduced hydrocarbon fuels, such as methane, results in undesirable carbon dioxide emissions.

[0010] There remains a need for improved processes for the catalytic cracking of ammonia. Specifically, there remains a need for improved processes for the catalytic cracking of ammonia that maximize the conversion of ammonia to produce hydrogen. Summary of the Invention

[0011] Accordingly, the present invention provides a process for the catalytic decomposition of ammonia, comprising: a primary decomposition pathway comprising one or more catalyst-containing reactor tubes disposed within a combustion ammonia decomposition reactor; and providing a parallel decomposition pathway comprising one or more secondary ammonia decomposition reactors arranged in series and fluidly connected to one another; The process is providing a first ammonia stream to the primary decomposition pathway; decomposing ammonia in the first ammonia stream in one or more catalyst-containing reactor tubes of a combustion ammonia decomposition reactor to produce a first hydrogen-containing stream; feeding the second ammonia stream to a parallel decomposition pathway; decomposing ammonia in the second ammonia stream in one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream further comprising unreacted ammonia; removing a second hydrogen-containing stream from a parallel cracking pathway; feeding the second hydrogen-containing stream to one or more purification units to increase the hydrogen content of the second hydrogen-containing stream to produce a hydrogen-enriched stream and a tail gas stream; combusting the tail gas stream with oxygen in a fuel combustion zone of a combustion ammonia decomposition reactor to provide thermal energy to support the decomposition of ammonia in one or more catalyst-containing reactor tubes; The process provides that the second hydrogen-containing stream comprises 40 mol % to 75 mol % H2.

[0012] It has been surprisingly found that the process of the present invention has excellent hydrogen recovery and power efficiency. In particular, it has been surprisingly found that by providing a parallel cracking pathway in accordance with the present invention, separating the tail gas from the resulting hydrogen-containing stream, and combusting the tail gas in a fuel combustion zone, it is possible to provide sufficient thermal energy to support the endothermic ammonia decomposition reaction in the combustion ammonia decomposition reactor of the primary cracking pathway. Furthermore, it has been surprisingly found that the process of the present invention can reduce or eliminate the need to use top-up fuel to support the endothermic ammonia decomposition reaction in the combustion ammonia decomposition reactor.

[0013] Additionally, the parallel cracking pathways of the present invention allow for the use of smaller combustion ammonia cracking reactors, thereby reducing the capital and operating costs of the process. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a block flow diagram of a process in accordance with the present invention. [Figure 2]FIG. 1 is a schematic diagram of a mini-reformer available from Johnson Matthey Davy Technologies Limited. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred and / or optional features of the invention will now be described. Any aspect of the invention may be combined with any other aspect of the invention unless the context requires otherwise. Any preferred and / or optional feature of any aspect may be combined with any aspect of the invention, either singly or in any combination, unless the context requires otherwise.

[0016] The process of the present invention involves providing a primary decomposition pathway comprising one or more catalyst-containing reactor tubes disposed within a combustion ammonia decomposition reactor.

[0017] Suitable combustion ammonia decomposition reactors are known and may include a fuel combustion zone with a radiant section including one or more burners supplied with one or more fuel streams and an oxygen-supplying gas, e.g., air, oxygen-enriched air, or oxygen. The radiant section may include one or more catalyst-containing reactor tubes through which the ammonia stream passes. Combustion of one or more fuel streams in one or more burners in the fuel combustion zone produces thermal energy (e.g., radiant heat) for heating one or more catalyst-containing reactor tubes. There may be tens or hundreds of catalyst-containing reactor tubes in the radiant section. Optionally, downstream of the radiant section, fuel gas from the combustion of one or more fuel streams may be used to preheat one or more feed streams in the convection section. Reactors with a catalyst-containing radiant section including reactor tubes and a convection section for preheating the feed are known for steam methane reforming and may be applied to the present invention.

[0018] Alternatively, a combustion ammonia decomposition reactor can be used where the combustion of one or more fuel streams in a fuel combustion zone is split into reactors with catalyst-containing reactor tubes. Such a reactor is the mini-reformer available from Johnson Matthey Davy Technologies Limited, a schematic of which is shown in Figure 2.

[0019] The catalyst in the catalyst-containing reactor tubes can be any ammonia decomposition catalyst. For example, nickel and / or ruthenium catalysts may be used. A preferred catalyst is a nickel catalyst. The catalyst can comprise 3 to 30 wt. % nickel, expressed as NiO, preferably 8 to 20 wt. % nickel, on a suitable refractory support, such as alumina or a metal aluminate. The catalyst can be in the form of pelletized units, which may contain one or more perforations, or provided as a washcoat on a structured metal or ceramic catalyst. A particularly preferred catalyst is KATALCO® 27-2, available from Johnson Matthey PLC, which comprises 12% nickel, expressed as NiO, on cylindrical pellets formed from a high surface area calcium aluminate support.

[0020] The one or more catalyst-containing reactor tubes may suitably be formed from an iron-based alloy, a nickel-based alloy, or a cobalt-based alloy. The iron-based alloy may be a stainless steel, preferably an iron-chromium-based alloy such as 316 stainless steel, or a high-nickel steel such as that described in WO 03 / 051771 A1. Preferably, the one or more catalyst-containing reactor tubes are formed from a nickel-based alloy or a cobalt-based alloy. More preferably, the one or more catalyst-containing reactor tubes are formed from a cobalt-based alloy.

[0021] The process of the present invention involves providing parallel decomposition pathways comprising one or more secondary ammonia decomposition reactors arranged in series and fluidly connected to one another.

[0022] The one or more secondary ammonia decomposition reactors may be in direct or indirect fluid communication with each other.

[0023] The parallel decomposition pathways of the present invention operate in parallel with the primary decomposition pathway of the present invention, and the parallel decomposition pathways and the primary decomposition pathways are not continuous with each other, i.e., decomposition gases from the parallel decomposition pathways or the primary decomposition pathways do not have to be fed as gases to be decomposed into the primary decomposition pathways or the parallel decomposition pathways, respectively.

[0024] The type of reactor that may be the one or more secondary ammonia decomposition reactors is not particularly limited. The one or more secondary ammonia decomposition reactors may be an adiabatic reactor, a packed bed reactor, an electrically heated reactor, and / or a gas-fired reactor. Preferably, the one or more secondary ammonia reactors are adiabatic reactors, such as an adiabatic packed bed reactor.

[0025] An adiabatic reactor includes a reactor that does not transfer heat to the second ammonia stream being fed, e.g., an adiabatic reactor does not include a reactor that provides thermal energy to the second ammonia stream.

[0026] The thermal energy required to support the decomposition reaction in one or more secondary ammonia decomposition reactors may be provided by heating the second ammonia stream and / or by providing a secondary ammonia decomposition reactor that provides the thermal energy. Preferably, the thermal energy may be provided from a source external to the process (e.g., externally introduced gas or externally introduced electricity).

[0027] For the avoidance of doubt, the secondary ammonia decomposition reactor functions to decompose ammonia to produce hydrogen and nitrogen.

[0028] The one or more secondary ammonia decomposition reactors include a catalyst. The catalyst may be any catalyst for decomposing ammonia. The catalyst may suitably be any one of those described above as suitable for use with the combustion ammonia decomposition reactor.

[0029] An advantage of providing parallel cracking pathways is that additional ammonia can be cracked in the process without burdening the combustion ammonia cracking reactor of the primary cracking pathway. In particular, providing parallel cracking pathways that include one or more secondary ammonia cracking reactors allows ammonia to be cracked under kinetically favorable conditions (e.g., when the ammonia stream has a higher ammonia partial pressure but lower nitrogen and hydrogen partial pressures) without the need for complex and expensive combustion ammonia cracking reactors. Furthermore, tail gas produced by purifying the hydrogen-containing stream removed from the parallel cracking pathway provides additional thermal energy to support the cracking of ammonia in the combustion ammonia cracking reactor.

[0030] The process of the present invention includes feeding a first ammonia stream to a primary decomposition pathway.

[0031] The first ammonia stream can be derived from any source. In a preferred process of the present invention, the first ammonia stream is produced by catalytic combination of hydrogen and nitrogen, for example, the ammonia stream can be produced from the Haber-Bosch ammonia synthesis process. In a preferred process of the present invention, the first ammonia stream can be produced in an ammonia production facility located upstream of the ammonia decomposition reactor. Alternatively, the first ammonia stream can be provided from an ammonia gas storage facility, an ammonia storage unit, an ammonia storage tank, or an ammonia gas pipeline.

[0032] The first ammonia stream can contain 90 mol% or more ammonia, 95 mol% or more ammonia, 97 mol% or more ammonia, or 99 mol% or more ammonia. The first ammonia stream can be substantially 100 mol% ammonia. By "substantially 100 mol% ammonia," it is meant that any other components may be present as incidental impurities and may be present in amounts less than 1 mol%, less than 0.5 mol%, or less than 0.1 mol% of the first ammonia stream.

[0033] The first ammonia stream may be combined with another ammonia-containing stream before or after being fed to the primary decomposition pathway. For example, the first ammonia stream may be combined with any process stream containing ammonia, such as a partially decomposed ammonia stream and / or a tail gas stream.

[0034] In a preferred process of the present invention, the first ammonia stream may be heated before being supplied to the primary decomposition pathway. In this case, the first ammonia stream becomes a heated first ammonia stream. Thus, the process of the present invention may include a step of heating the first ammonia stream. The first ammonia stream may 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 may 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 may be heated to a temperature between 350°C and 1000°C, between 400°C and 950°C, between 450°C and 850°C, or between 500°C and 750°C, for example, between 550°C and 700°C.

[0035] The process of the present invention comprises decomposing ammonia in a first ammonia stream in one or more catalyst-containing reactor tubes of a combustion ammonia decomposition reactor to produce a first hydrogen-containing stream.

[0036] The temperature of the first ammonia stream at the inlet to the one or more catalyst-containing reactor 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, for example, 550°C to 700°C. The temperature of the first hydrogen-containing stream exiting the one or more catalyst-containing reactor tubes affects the equilibrium position of the decomposition reaction and can be in the range of 500 to 950°C. When a nickel catalyst is used in the one or more catalyst-containing reactor tubes, the temperature of the first hydrogen-containing stream exiting the one or more catalyst-containing reactor tubes can preferably be greater than about 700°C.

[0037] The inlet pressure to the one or more catalyst-containing reactor tubes is set by the flowsheet design and may range from 1 to 100 bar absolute, preferably from 10 to 90 bar absolute, for example from 31 to 51 bar absolute.

[0038] The first hydrogen-containing stream contains H. The first hydrogen-containing stream also contains nitrogen (N), and may further contain residual ammonia (e.g., unreacted ammonia).

[0039] The first hydrogen-containing stream may contain 60 mol% or more H2, 65 mol% or more H2, 70 mol% or more H2, 72 mol% or more H2, or 73 mol% or more H2. The first hydrogen-containing stream may contain up to 75 mol% H2. For example, the first hydrogen-containing stream may contain 60 mol% to 75 mol% H2. Preferably, the first hydrogen-containing stream contains 70 mol% to 75 mol% H2, for example, 72 mol% to 75 mol% H2.

[0040] The first hydrogen-containing stream may contain 20 mol% or more N2, 21 mol% or more N2, 22 mol% or more N2, or 23 mol% or more N2. The first hydrogen-containing stream may contain up to 25 mol% N2. For example, the first hydrogen-containing stream may contain 20 mol% to 25 mol% N2. Preferably, the first hydrogen-containing stream contains 22 mol% to 25 mol% N2, for example, 23 mol% to 25 mol% N2.

[0041] The first hydrogen-containing stream may contain less than 20 mol% NH3, less than 15 mol% NH3, less than 10 mol% NH3, less than 5 mol% NH3, less than 1 mol% NH3, or less than 0.1 mol% NH3. Preferably, the first hydrogen-containing stream contains less than 4 mol% NH3, less than 2 mol% NH3, less than 1 mol% NH3, or less than 0.1 mol% NH3.

[0042] Preferably, the first hydrogen-containing stream can include an equilibrium mixture of ammonia, hydrogen, and nitrogen. In other words, the first hydrogen-containing stream can include a mixture of ammonia, hydrogen, and nitrogen at partial pressures such that no more hydrogen and nitrogen can be produced from further decomposition reactions. The equilibrium mixture can include 72 mol% to 75 mol% H2, 23 mol% to 25 mol% N2, and less than 4 mol% NH3 (e.g., less than 1 mol% or less than 0.1 mol% NH3).

[0043] The process of the present invention includes feeding a second ammonia stream to a parallel decomposition pathway.

[0044] The second ammonia stream can be obtained from any source, for example, the second ammonia stream can be obtained from the same or a different source than the first ammonia stream.

[0045] The second ammonia stream can contain 90 mol% or more ammonia, 95 mol% or more ammonia, 97 mol% or more ammonia, or 99 mol% or more ammonia. The second ammonia stream can be substantially 100 mol% ammonia. By "substantially 100 mol% ammonia," it is meant that any other components may be present as incidental impurities and may be present in amounts less than 1 mol%, less than 0.5 mol%, or less than 0.1 mol% of the second ammonia stream.

[0046] It may be preferable to heat the second ammonia stream before or after it is fed to the parallel decomposition pathway. The second ammonia stream may be heated using an electric heater or by using waste or recovered heat from elsewhere in the process. Alternatively, or in addition, the second ammonia stream may be heated by one or more secondary ammonia decomposition reactors (e.g., electrically heated ammonia decomposition reactors).

[0047] In a preferred process 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 piece of process equipment. The heated first ammonia stream can be fed to a primary decomposition pathway including a combustion ammonia decomposition reactor, and the heated second ammonia stream can be fed to a parallel decomposition pathway. For example, it may be preferred that the second ammonia stream is a portion of the first ammonia stream heated to the above-mentioned temperature. Thus, the process of the present invention may include heating the first ammonia stream and the second ammonia stream in the same piece of process equipment.

[0048] The temperature to which the second ammonia stream is heated can depend on the catalyst selection in the subsequent first secondary ammonia decomposition reactor and / or further secondary decomposition reactors. For example, if the first secondary ammonia decomposition 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, or 800°C to 850°C. For example, if the first secondary ammonia decomposition reactor uses a noble metal catalyst (e.g., a 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). Typically, the second ammonia stream can be heated to a temperature of 700°C to 1000°C.

[0049] The process of the present invention includes decomposing ammonia in the second ammonia stream in one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream that may further include unreacted ammonia.

[0050] The inlet pressure to the one or more secondary ammonia decomposition reactors may typically be in the range of from 1 to 100 bar absolute, preferably from 10 to 90 bar absolute, for example from 31 to 51 bar absolute. Prior to feeding the ammonia stream to the secondary ammonia decomposition reactor, the pressure may be set (e.g., increased) by a pump or compressor.

[0051] Typically, the cracked second ammonia stream exiting the first of the one or more secondary ammonia decomposition reactors contains ammonia in an amount of 65 mol% to 85 mol%, e.g., 70 mol% to 80 mol%. Typically, the cracked second ammonia stream exiting the first of the one or more secondary ammonia decomposition reactors contains hydrogen in an amount of 10 mol% to 20 mol%, e.g., 12.5 mol% to 17.5 mol%. Typically, the cracked second ammonia stream exiting the first of the one or more secondary ammonia decomposition reactors contains nitrogen in an amount of 1 mol% to 10 mol%, e.g., 3 mol% to 8 mol%. As will be appreciated, if more than one secondary ammonia decomposition reactor is provided in a parallel decomposition pathway, the amounts of hydrogen and nitrogen in the cracked second ammonia stream will increase, but the amount of ammonia will decrease, with each successive secondary ammonia decomposition reactor the stream passes through. It will also be appreciated that the amount of ammonia cracked will depend on the configuration of the secondary ammonia decomposition reactor.

[0052] As will be appreciated, the temperature of the ammonia stream entering the secondary ammonia decomposition reactor will be higher than the decomposed ammonia stream exiting the secondary ammonia decomposition reactor due to the endothermic nature of the ammonia decomposition reaction.

[0053] The temperature of the decomposed second ammonia stream after decomposition of ammonia in the secondary ammonia decomposition reactor depends on the catalyst used in the secondary ammonia decomposition reactor. Typically, if the secondary ammonia decomposition reactor uses a nickel catalyst such as Katalco 27-2, the decomposed second ammonia stream may have a temperature of 450°C to 600°C, e.g., 500°C to 550°C, after decomposition in the secondary ammonia decomposition reactor. Typically, if the secondary ammonia decomposition reactor uses a noble metal catalyst (e.g., a ruthenium-based catalyst) such as Katalco 27-612, the decomposed second ammonia stream may have a temperature of 350°C to 500°C, e.g., 400°C to 450°C, after decomposition in the secondary ammonia decomposition reactor.

[0054] The process of the present invention includes removing a second hydrogen-containing stream from a parallel cracking pathway.

[0055] Following the ammonia decomposition reaction in one or more secondary ammonia decomposition reactors of the parallel decomposition pathway, a second hydrogen-containing stream is produced. The second hydrogen-containing stream is withdrawn from the parallel decomposition pathway. For the avoidance of doubt, the second hydrogen-containing stream withdrawn from the parallel decomposition pathway may be the decomposed second ammonia stream after undergoing decomposition in all of the one or more secondary ammonia decomposition reactors.

[0056] The second hydrogen-containing stream contains 40 mol% to 75 mol% H2. The second hydrogen-containing stream may contain 50 mol% or more H2 or 60 mol% or more H2. The second hydrogen-containing stream contains up to 75 mol% H2. For example, the second hydrogen-containing stream may contain 50 mol% to 75 mol% H2 or 60 mol% to 75 mol% H2.

[0057] The second hydrogen-containing stream may contain 20 mol% or more N2, 21 mol% or more N2, 22 mol% or more N2, or 23 mol% or more N2. The second hydrogen-containing stream may contain up to 25 mol% N2. For example, the second hydrogen-containing stream may contain 20 mol% to 25 mol% N2. Preferably, the second hydrogen-containing stream contains 22 mol% to 25 mol% N2, for example, 23 mol% to 25 mol% N2.

[0058] The second hydrogen-containing stream may contain less than 20 mol% NH3, less than 15 mol% NH3, less than 10 mol% NH3, less than 5 mol% NH3, less than 1 mol% NH3, or less than 0.1 mol% NH3. Preferably, the second hydrogen-containing stream contains less than 4 mol% NH3, less than 2 mol% NH3, less than 1 mol% NH3, or less than 0.1 mol% NH3.

[0059] Preferably, the second hydrogen-containing stream can include an equilibrium mixture of ammonia, hydrogen, and nitrogen. In other words, the second hydrogen-containing stream can include a mixture of ammonia, hydrogen, and nitrogen at partial pressures such that no more hydrogen and nitrogen can be produced from further decomposition reactions. The equilibrium mixture can include 72 mol% to 75 mol% H2, 23 mol% to 25 mol% N2, and less than 4 mol% NH3 (e.g., less than 1 mol% or less than 0.1 mol% NH3).

[0060] The process of the present invention includes feeding the second hydrogen-containing stream to one or more purification units to increase the hydrogen content of the second hydrogen-containing stream to produce a hydrogen-enriched stream and a tail gas stream.

[0061] The second hydrogen-containing stream is fed to one or more purification units, such as a pressure swing absorption unit, to increase the H content by separating H from other components. In a preferred process of the present invention, the first hydrogen-containing stream from the primary cracking pathway and the second hydrogen-containing stream from the parallel cracking pathway may be fed to one or more purification units to produce one or more hydrogen-enriched streams and one or more tail gas streams. In a preferred process of the present invention, the first hydrogen-containing stream and the second hydrogen-containing stream may be fed to the same purification unit or to different purification units.

[0062] It will be appreciated that if the first hydrogen-containing stream and the second hydrogen-containing stream are fed to the same purification unit, the hydrogen-rich stream may be recovered from the purification unit as a single hydrogen-rich stream. If the first hydrogen-containing stream and the second hydrogen-containing stream are fed to different purification units, the hydrogen-rich stream may be obtained as multiple hydrogen-rich streams that may optionally be combined to form a single hydrogen-rich stream.

[0063] It may be preferable to supply the first and / or second hydrogen-containing streams to a steam generation unit and / or heat recovery zone before supplying the first and / or second hydrogen-containing streams to one or more purification units. As will be appreciated by those skilled in the art, the steam generation unit and / or heat recovery zone may be used to recover low or moderate amounts of heat.

[0064] It may be preferred that the first hydrogen-containing stream and the second hydrogen-containing stream both comprise an equilibrium mixture of hydrogen, nitrogen, and ammonia, as described above.

[0065] In the process of the present invention, tail gas produced from the first and second hydrogen-containing streams is combusted with oxygen to provide thermal energy to support the decomposition of ammonia in one or more catalyst-containing reactor tubes. The higher the hydrogen content of the first hydrogen-containing stream and / or the second hydrogen-containing stream, the greater the amount of hydrogen in the tail gas. Therefore, it is surprising that the overall hydrogen recovery of the process can be maximized with higher power efficiency when both the first hydrogen-containing stream and / or the second hydrogen-containing stream contain a higher hydrogen content (e.g., 40 mol % or more, preferably an equilibrium mixture of hydrogen, nitrogen, and ammonia). Therefore, it may be preferred that both the first hydrogen-containing stream and the second hydrogen-containing stream contain a high hydrogen content (e.g., 40 mol % or more, preferably an equilibrium mixture of hydrogen, nitrogen, and ammonia), and the tail gas can have a composition as defined below.

[0066] The hydrogen-rich stream may contain 70 mol% or more H2, 75 mol% or more H2, 80 mol% or more H2, 85 mol% or more H2, or 90 mol% or more H2. The hydrogen-rich stream may contain 100 mol% or less H2. For example, the hydrogen-rich stream may contain 70 mol% to 100 mol% H2, 75 mol% to 100 mol% H2, 80 mol% to 100 mol% H2, 85 mol% to 100 mol% H2, or 90 mol% to 100 mol% H2. Preferably, the hydrogen-rich stream may contain greater than 90 mol% H2, greater than 95 mol% H2, greater than 98 mol% H2, or greater than 99 mol% H2. More preferably, the hydrogen-rich stream may contain greater than 99.9 mol% H2, greater than 99.95 mol% H2, or about 100 mol% H2. Most preferably, the hydrogen-rich stream may contain greater than 99.95 mole % H2 or about 100 mole % H2.

[0067] The hydrogen-rich stream may be further purified to produce a purified hydrogen product. The hydrogen-rich stream may have a sufficiently high purity to be a purified hydrogen product.

[0068] It will be understood that if the first hydrogen-containing stream and the second hydrogen-containing stream are fed to the same purification unit, the tail gas stream may be recovered as a single tail gas stream. If the first hydrogen-containing stream and the second hydrogen-containing stream are fed to different purification units, the tail gas stream may be obtained as multiple tail gas streams that may optionally be combined to form a single tail gas stream.

[0069] The tail gas stream may contain nitrogen (N), ammonia, and hydrogen (H). The composition of the tail gas stream depends on the configuration of the primary and parallel cracking pathways and the composition of the hydrogen-containing streams removed therefrom.

[0070] Typically, the tail gas stream may contain 20 mol% to 95 mol% N2, 45 mol% to 85 mol% N2, or 65 mol% to 80 mol% N2.

[0071] Typically, the tail gas stream may contain between 3 mol% and 10 mol% ammonia, between 3.2 mol% and 7 mol% ammonia, or between 3.3 mol% and 5 mol% ammonia.

[0072] Typically, the tail gas stream may contain 10 mol% to 70 mol% H2, for example, 20 mol% to 50 mol% H2. It may be preferred that the tail gas stream contain 15 mol% to 40 mol% H2, 20 mol% to 35 mol% H2, or 22 mol% to 30 mol% H2.

[0073] The process of the present invention involves combusting a tail gas stream with oxygen in a fuel combustion zone of a combustion ammonia decomposition reactor to provide thermal energy to support the decomposition of ammonia in one or more catalyst-containing reactor tubes.

[0074] The oxygen used to combust one or more tail gas streams may suitably be or include air, compressed air, oxygen-enriched air, oxygen, or an inert gas such as oxygen and nitrogen.

[0075] As noted above, the fuel combustion zone may be within the combustion ammonia decomposition reactor or may be in a separate vessel for combustion that is fluidly connected to the combustion ammonia decomposition reactor.

[0076] In a preferred process of the present invention, the parallel decomposition pathway may include providing two or more, three or more, four or more, or five or more secondary ammonia decomposition reactors arranged in series.

[0077] When two or more secondary ammonia decomposition reactors are provided, the second ammonia stream is fed to each of the successively arranged secondary ammonia decomposition reactors, in each case producing a decomposed second ammonia stream. As the decomposed second ammonia stream passes through each successive secondary ammonia decomposition reactor, additional ammonia is decomposed, changing the composition of the second ammonia stream. The term "decomposed second ammonia stream" is used to refer to a second ammonia stream that has passed through at least one secondary ammonia decomposition reactor and has had the ammonia in that stream decomposed.

[0078] The total number of secondary ammonia decomposition reactors that may be present in the parallel cracking pathway is not particularly limited and will depend on the desired composition of the second hydrogen-containing stream removed from the parallel cracking pathway, the catalyst used, and the temperature of the second ammonia stream and / or the decomposed second ammonia stream. Preferably, sufficient secondary ammonia decomposition reactors are provided so that the second hydrogen-containing stream is removed from the parallel cracking pathway as an equilibrium mixture as described above.

[0079] Thus, the parallel decomposition pathway preferably includes two or more, three or more, four or more, or five or more secondary ammonia decomposition reactors arranged in series and in fluid communication with one another. Thus, the process of the present invention may include feeding the decomposed second ammonia stream to the second, third, fourth, and / or fifth secondary ammonia decomposition reactors of the parallel decomposition pathway.

[0080] The catalysts used in each of the one or more secondary ammonia decomposition reactors may be the same or different from one another.

[0081] In a preferred process of the present invention, the temperature of the decomposed second ammonia stream exiting any one secondary ammonia decomposition reactor is high enough for decomposition of ammonia to occur in the subsequent secondary ammonia decomposition reactor without the need for an intermediate reheat step.

[0082] Thus, the process of the present invention may include passing the decomposed second ammonia stream directly to one or more subsequent secondary ammonia decompositions without an intermediate reheating step.

[0083] In a preferred process of the present invention, the parallel decomposition pathway comprises two or more secondary ammonia decomposition reactors arranged in series and fluidly connected to one another.

[0084] In a preferred embodiment of the invention, a first of the two or more secondary ammonia decomposition reactors may contain a catalyst that operates at a higher temperature (e.g., a catalyst that catalyzes the decomposition of ammonia at a temperature between 700°C and 1000°C), and a second of the secondary ammonia decomposition reactors may contain a catalyst that operates at a lower temperature (e.g., a catalyst that catalyzes the decomposition of ammonia at a temperature between 450°C and 650°C).

[0085] In a more preferred embodiment of the invention, a first of the two or more secondary ammonia decomposition reactors may contain a nickel-containing catalyst and a second of the secondary ammonia decomposition reactors may contain a precious metal-containing catalyst (e.g., a ruthenium-based catalyst). Preferably, in this configuration, the decomposed second ammonia stream is passed from the first of the two or more secondary ammonia decomposition reactors to the second of the two or more secondary ammonia decomposition reactors without an intermediate heating step.

[0086] It is an advantage of the present invention that two secondary ammonia decomposition reactors can be provided that are arranged in series and contain different catalysts, allowing ammonia to be decomposed over a wide temperature range by utilizing catalysts of different activity.

[0087] The parallel decomposition paths may include one or more heaters.

[0088] A heater may be provided to increase the temperature of the decomposed second ammonia stream and provide sufficient thermal energy for the ammonia in the decomposed second ammonia stream to be decomposed.

[0089] The one or more heaters may be powered or fueled by burning a gas such as a hydrocarbon gas, hydrogen, or ammonia, or by electricity. The one or more heaters may preferably be powered or fueled from a source external to the process (e.g., externally introduced gas or externally introduced electricity).

[0090] The one or more heaters are preferably electric heaters. Preferably, the one or more heaters are electric heaters that derive electricity generated external to the process. Even more preferably, the one or more heaters are electric heaters that derive electricity generated from renewable sources, such as wind, solar, hydroelectric, or tidal sources.

[0091] The one or more heaters may be part of one or more secondary ammonia decomposition reactors, for example, the one or more heaters may form part of an electrically heated packed bed reactor.

[0092] In a preferred process of the present invention, the one or more secondary ammonia decomposition reactors may be adiabatic reactors, and thermal energy to support the decomposition reaction in the one or more secondary ammonia decomposition reactors may be provided by heating the second ammonia stream using one or more heaters.

[0093] The process of the present invention may include reheating the decomposed second ammonia stream using a heater (e.g., an electric heater) to produce a reheated decomposed second ammonia stream.

[0094] The process of the present invention may include reheating the decomposed second ammonia stream and feeding it to one or more subsequent secondary ammonia decomposition reactors. The step of reheating the decomposed second ammonia stream has the advantage of providing a subsequent secondary ammonia decomposition reactor to convert unreacted ammonia in the decomposed second ammonia stream. The process of the present invention may include providing a heater (e.g., an electric heater) located upstream of the secondary ammonia decomposition reactor.

[0095] Thus, the process may include reheating the decomposed second ammonia stream using a heater (e.g., an electric heater) to produce a reheated decomposed second ammonia stream, and feeding the reheated decomposed second ammonia stream to one or more subsequent secondary ammonia decomposition reactors.

[0096] The temperature to which the decomposed second ammonia stream is reheated depends on the nature of the catalyst used in the one or more secondary ammonia decomposition reactors. For example, if the secondary ammonia decomposition reactor uses a nickel-containing catalyst such as Katalco 27-2, the decomposed second ammonia stream may be reheated to a temperature of 700°C to 1000°C, 750°C to 900°C, or 800°C to 850°C. For example, if the one or more secondary ammonia decomposition reactors use a noble metal catalyst (e.g., a ruthenium-based catalyst) such as Katalco 27-612, the decomposed second ammonia stream may 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). Typically, the decomposed second ammonia stream may be reheated to a temperature of 700°C to 1000°C.

[0097] An advantage of using a heater powered or fueled from a source external to the process in reheating the second ammonia stream is that the consumption of raw material (e.g., pure ammonia) or product material (e.g., pure hydrogen) to provide thermal energy for the ammonia decomposition reaction is reduced or eliminated. It is particularly advantageous for one or more heaters to be electric heaters. Although electrical energy must be used by the electric heaters, it has surprisingly been found that the overall power efficiency of the process of the present invention is higher than if the electric heater and secondary ammonia decomposition reactor were not used.

[0098] The need to provide a heater (e.g., an electric heater) at any point in the process of the present invention depends on the number of secondary ammonia decomposition reactors used, the nature of the catalyst disposed in each of the secondary ammonia decomposition reactors, the temperature of the second ammonia stream and / or the decomposed second ammonia stream after the decomposition reaction in each of the secondary ammonia decomposition reactors, and the desired composition of the second hydrogen-containing stream removed from the parallel ammonia decomposition pathway.

[0099] In a preferred process of the present invention, the parallel cracking pathway comprises three or more secondary ammonia cracking reactors, and the process comprises: feeding the second ammonia stream to a parallel decomposition pathway; decomposing ammonia in the second ammonia stream in one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream further comprising unreacted ammonia; reheating the decomposed second ammonia stream to a temperature of between 700°C and 1000°C using a heater (e.g., an electric heater) to produce a reheated decomposed second ammonia stream; feeding the reheated decomposed second ammonia stream to a secondary ammonia decomposition reactor containing a nickel-containing catalyst (e.g., Katalco 27-2); Optionally, reheating the decomposed second ammonia stream to a temperature of between 700°C and 1000°C using a heater (e.g., an electric heater) to produce a reheated decomposed second ammonia stream; feeding the reheated decomposed second ammonia stream to a secondary ammonia decomposition reactor containing a nickel-containing catalyst (e.g., Katalco 27-2); Includes.

[0100] In a preferred process of the present invention, the parallel cracking pathway comprises three or more secondary ammonia cracking reactors, and the process comprises: feeding the second ammonia stream to a parallel decomposition pathway; decomposing ammonia in the second ammonia stream in one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream further comprising unreacted ammonia; reheating the decomposed second ammonia stream to a temperature of between 700°C and 1000°C using a heater (e.g., an electric heater) to produce a reheated decomposed second ammonia stream; feeding the reheated decomposed second ammonia stream to a secondary ammonia decomposition reactor containing a nickel-containing catalyst (e.g., Katalco 27-2); feeding the decomposed second ammonia stream directly (i.e., without an intermediate reheat step) to a secondary ammonia decomposition reactor containing a precious metal-containing catalyst (e.g., Katalco 27-612); reheating the decomposed second ammonia stream to a temperature of between 700°C and 1000°C using a heater (e.g., an electric heater); feeding the decomposed second ammonia stream to a secondary ammonia decomposition reactor containing a nickel-containing catalyst (e.g., Katalco 27-2).

[0101] In certain processes of the present invention, in addition to the tail gas stream, one or more fuel streams may be combusted with oxygen in the fuel combustion zone, such that the combustion provides thermal energy used to support the endothermic ammonia decomposition reaction in the ammonia decomposition reactor. Thus, the process of the present invention may include combusting one or more fuel streams with oxygen in the fuel combustion zone to provide thermal energy to the combusted ammonia decomposition reactor.

[0102] Preferably, the one or more fuel sources may include a carbon-free fuel source (e.g., hydrogen or ammonia). It may be preferred that the one or more fuel sources do not include a carbon-containing fuel source.

[0103] The one or more fuel streams may comprise one or more of hydrogen, natural gas, methane, refinery off-gas, biogas, tail gas from a hydrogen purification unit, a fuel portion of a first or second hydrogen-containing stream, or a fuel portion of a hydrogen-rich stream from one or more purification units.

[0104] As used herein, the term "fuel portion" is used to refer to the portion of a stream (e.g., a hydrogen-containing stream, a hydrogen-rich stream, or the first or second ammonia stream) that is used as a fuel source. The term is not used to refer to the portion of a stream that is used in the ammonia decomposition reaction.

[0105] In certain processes of the invention, the one or more fuel streams can include a hydrogen-containing fuel stream. The hydrogen-containing fuel stream can be a fuel portion of a hydrogen-containing stream produced from an ammonia decomposition reactor. The hydrogen-containing fuel stream can be a fuel portion of a hydrogen-rich stream from a purification unit. Thus, the process can include removing the fuel portion of the hydrogen-containing stream or the fuel portion of a hydrogen-enriched stream and combusting the fuel portion of the hydrogen-containing stream or the fuel portion of the hydrogen-rich stream with oxygen in a fuel combustion zone to provide thermal energy to support the endothermic ammonia decomposition reaction in the ammonia decomposition reactor.

[0106] For the avoidance of doubt, one or more fuel streams may be combined with another and / or tail gas stream prior to combustion, or each stream may be combined at a single point of combustion.

[0107] Combustion of the tail gas stream and, optionally, one or more fuel streams in the fuel combustion zone generates flue gas, which can be recovered from the combustion ammonia decomposition reactor. The flue gas may be cooled in one or more cooling stages and subjected to one or more purification stages before being discharged to the atmosphere. The one or more cooling stages may include recovering thermal energy from the flue gas. For example, the one or more cooling stages may include preheating and / or generating steam for one or more of the reactants for the combustion ammonia decomposition reactor and / or the secondary ammonia decomposition reactor. The one or more purification stages may include a selective catalytic reduction (SCR) stage in which nitrogen oxides react with ammonia to form nitrogen and water vapor. Any flue gas selective catalytic reduction technology may be used.

[0108] In a preferred process of the present invention, the process comprises: a primary decomposition pathway comprising one or more catalyst-containing reactor tubes disposed within a combustion ammonia decomposition reactor; and a parallel decomposition pathway comprising one or more secondary ammonia decomposition reactors arranged in series and fluidly connected to one another; providing The process is feeding a first ammonia stream to a primary decomposition pathway; decomposing ammonia in the first ammonia stream in one or more catalyst-containing reactor tubes of a combustion ammonia decomposition reactor to produce a first hydrogen-containing stream; feeding the second ammonia stream to a parallel decomposition pathway; decomposing ammonia in the second ammonia stream in one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream further comprising unreacted ammonia; removing a second hydrogen-containing stream from a parallel cracking pathway; feeding the second hydrogen-containing stream and optionally the first hydrogen-containing stream to one or more purification units to increase the hydrogen content of the second hydrogen-containing stream and optionally the first hydrogen-containing stream to produce a hydrogen-enriched stream and a tail gas stream; and combusting the tail gas stream with oxygen in a fuel combustion zone of a combustion ammonia decomposition reactor to provide thermal energy to support the decomposition of ammonia in one or more catalyst-containing reactor tubes.

[0109] In a preferred process of the present invention, the process comprises: a primary decomposition pathway comprising one or more catalyst-containing reactor tubes disposed within a combustion ammonia decomposition reactor; and a parallel decomposition pathway comprising one or more secondary ammonia decomposition reactors arranged in series and fluidly connected to one another; providing The process is feeding a first ammonia stream to a primary decomposition pathway; decomposing ammonia in the first ammonia stream in one or more catalyst-containing reactor tubes of a combustion ammonia decomposition reactor to produce a first hydrogen-containing stream; feeding the second ammonia stream to a parallel decomposition pathway; decomposing ammonia in the second ammonia stream in one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream further comprising unreacted ammonia; reheating the decomposed second ammonia stream using a heater (e.g., an electric heater) to produce a reheated decomposed second ammonia stream; feeding the reheated decomposed second ammonia stream to one or more subsequent secondary ammonia decomposition reactors; decomposing ammonia in the reheated decomposed second ammonia stream in one or more subsequent secondary ammonia decomposition reactors; removing a second hydrogen-containing stream from a parallel cracking pathway; feeding the second hydrogen-containing stream and optionally the first hydrogen-containing stream to one or more purification units to increase the hydrogen content of the second hydrogen-containing stream and optionally the first hydrogen-containing stream to produce a hydrogen-enriched stream and a tail gas stream; and combusting the tail gas stream with oxygen in a fuel combustion zone of a combustion ammonia decomposition reactor to provide thermal energy to support the decomposition of ammonia in the one or more catalyst-containing reactor tubes.

[0110] The invention will now be described in more detail in the following non-limiting embodiments and with reference to the drawings.

[0111] Figure 1 shows a block flow diagram of a process according to the present invention. Figure 1 shows that an ammonia stream (1) is fed to a heating unit (2), which heats the ammonia stream to produce a first ammonia stream (101) and a second ammonia stream (102a). The first ammonia stream (101) is fed to a primary decomposition pathway (14). The primary decomposition pathway (14) includes one or more catalyst-containing reactor tubes disposed within a combustion ammonia decomposition reactor (3). Ammonia in the first ammonia stream is decomposed in the one or more catalyst-containing reactor tubes of the combustion ammonia decomposition reactor (3) to produce a first hydrogen-containing stream (103). The second ammonia stream (102a) is fed to a parallel ammonia decomposition pathway (13). The parallel ammonia decomposition pathway includes one or more secondary ammonia decomposition reactors (4, 6, 8) disposed in series and fluidly connected to each other, and electric heaters (5, 7). The second ammonia stream (102a) is fed to a first secondary ammonia decomposition reactor (4). The ammonia in the second ammonia stream (102a) is decomposed in the first secondary ammonia decomposition reactor (4) to produce a decomposed second ammonia stream (104a) further comprising unreacted ammonia. At this stage, the temperature of the decomposed second ammonia stream (104a) is lower than the temperature of the ammonia stream (102a) entering the first secondary ammonia decomposition reactor (4). The second ammonia stream (104a) is fed to an electric heater (5) where it is reheated. The reheated decomposed second ammonia stream (102b) is fed to a second secondary ammonia decomposition reactor (6) where the unreacted ammonia is decomposed to produce a decomposed second ammonia stream (104b). The decomposed second ammonia stream (104b) is fed to a further electric heater (7) where it is reheated. The reheated cracked second ammonia stream (102c) is fed to a third secondary ammonia decomposition reactor (8) where unreacted ammonia is decomposed to produce a second hydrogen-containing stream (108) which is removed from the parallel ammonia decomposition pathway (13). The second hydrogen-containing stream may be an equilibrium or near-equilibrium cracked ammonia gas stream. The first hydrogen-containing stream (103) and the second hydrogen-containing stream (108) are fed to a heat recovery unit (9) where heat is recovered.The first hydrogen-containing stream (103) and the second hydrogen-containing stream (103) are combined and fed as a single stream (109) to a purification unit (10). The purification unit (10) increases the hydrogen content of the hydrogen-containing stream (109) to produce a hydrogen-enriched stream (111) and a tail gas stream (110). The hydrogen-enriched stream (111) can be recovered as a purified hydrogen product (11). The tail gas (110) is fed to a combustion ammonia decomposition reactor (3) and combusted with oxygen from an oxygen-containing feed (112) in a fuel combustion zone of the combustion ammonia decomposition reactor (3) to provide thermal energy to support the decomposition of ammonia in one or more catalyst-containing reactor tubes. [Example]

[0112] The ammonia decomposition process described above and shown in Figure 1 was compared to a process utilizing only a combustion reactor. The hydrogen recovery and power efficiency of each were compared. Both processes were based on the decomposition of an ammonia stream containing 50 tons of ammonia per hour.

[0113] Multi-stage cracker (according to the present invention) 58.3% of the ammonia was sent to the secondary bed, 40.0% to the combustion cracker, and 1.5% to the fuel. 28.8 MW of electrical energy was input. NO x 0.2% for SCR reduction

[0114] Combustion decomposition equipment only (comparison) 85% of the ammonia was sent to a combustion cracker and 14.6% to fuel, and 1.7 MW of electrical energy was generated via a steam turbine for transport.

[0115] The overall recovery rates are shown in Table 1.

[0116] [Table 1] * The hydrogen recovery rate is defined as follows:

[0117]

number

[0118]

number

[0119] The process of the present invention, which utilizes a secondary ammonia decomposition reactor arranged in series, recovers significantly more hydrogen than a process including only a combustion ammonia decomposition reactor. Furthermore, the increased hydrogen recovery of the process of the present invention is achieved at a higher power efficiency.

Claims

1. 1. A process for the catalytic decomposition of ammonia, comprising: a primary decomposition pathway comprising one or more catalyst-containing reactor tubes disposed within a combustion ammonia decomposition reactor; and providing a parallel decomposition pathway comprising one or more secondary ammonia decomposition reactors arranged in series and fluidly connected to one another; The process comprises: feeding a first ammonia stream to the primary decomposition pathway; decomposing ammonia in the first ammonia stream in the one or more catalyst-containing reactor tubes of the combustion ammonia decomposition reactor to produce a first hydrogen-containing stream; feeding a second ammonia stream to said parallel decomposition pathway; decomposing ammonia in the second ammonia stream in the one or more secondary ammonia decomposition reactors to produce a decomposed second ammonia stream further comprising unreacted ammonia; removing a second hydrogen-containing stream from the parallel cracking pathway; feeding the second hydrogen-containing stream to one or more purification units to increase the hydrogen content of the second hydrogen-containing stream to produce a hydrogen-enriched stream and a tail gas stream; combusting the tail gas stream with oxygen in a fuel combustion zone of the combustion ammonia decomposition reactor to provide thermal energy to support the decomposition of ammonia in the one or more catalyst-containing reactor tubes; The second hydrogen-containing stream is 40 mol % to 75 mol % H ２ The process includes:

2. 10. The process of claim 1, wherein the first ammonia stream comprises at least 90 mol% ammonia, at least 95 mol% ammonia, at least 97 mol% ammonia, at least 99 mol% ammonia, or essentially 100 mol% ammonia.

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

4. 4. The process of any one of claims 1 to 3, comprising heating the first ammonia stream to a temperature of from 350°C to 1000°C, from 400°C to 950°C, from 450°C to 850°C, or from 500°C to 750°C.

5. 5. The process of any one of claims 1 to 4, wherein the inlet pressure to the one or more catalyst-containing reactor tubes is in the range of from 1 to 100 bar absolute, preferably from 10 to 90 bar absolute, more preferably from 31 to 51 bar absolute.

6. 6. The process of any one of claims 1 to 5, wherein the second ammonia stream and the first ammonia stream are the same, the second ammonia stream and the first ammonia stream are heated together, and the heated first ammonia stream and the heated second ammonia stream are obtained from the same piece of process equipment.

7. The first hydrogen-containing stream is 60 mol % to 75 mol % H ２ , 70 mol % to 75 mol % H ２ 7. The process of claim 1, wherein the hydroxyl group is hydroxypropyl or hydroxypropyl.

8. 8. The process of any one of claims 1 to 7, wherein the second ammonia stream is heated to a temperature of from 700°C to 1000°C, from 750°C to 900°C, or from 800°C to 850°C before or after being fed to the parallel decomposition pathway.

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

10. The second hydrogen-containing stream is 50 mol % to 75 mol % H ２ or 60 mol% to 75 mol% H ２ The process according to any one of claims 1 to 9, comprising:

11. The hydrogen-rich stream is 70 mol % to 100 mol % H ２ , 75 mol % to 100 mol % H ２ , 80 mol % to 100 mol % H ２ , 85 mol % to 100 mol % H ２ or 90 mol % to 100 mol % H ２ The process according to any one of claims 1 to 10, comprising:

12. 12. The process of any one of claims 1 to 11, wherein the tail gas comprises from 3 mol% to 10 mol% ammonia, from 3.2 mol% to 7 mol% ammonia, or from 3.3 mol% to 5 mol% ammonia.

13. the tail gas stream being 10 mol % to 70 mol % H ２ or 20 mol % to 50 mol % H ２ The process according to any one of claims 1 to 12, comprising:

14. The first hydrogen-containing stream is 72 mol % to 75 mol % H ２ , 23 mol % to 25 mol % N ２ and less than 4 mol% NH ３ The process according to any one of claims 1 to 13, comprising:

15. The second hydrogen-containing stream is 72 mol % to 75 mol % H ２ , 23 mol % to 25 mol % N ２ and less than 4 mol% NH ３ The process according to any one of claims 1 to 14, comprising:

16. 16. The process of any one of claims 1 to 15, wherein the parallel decomposition pathway comprises two or more, three or more, four or more, or five or more secondary ammonia decomposition reactors arranged in series and in fluid communication with one another.

17. 17. The process of claim 16, wherein a first of the two or more secondary ammonia decomposition reactors comprises a nickel-containing catalyst and a second of the secondary ammonia decomposition reactors comprises a precious metal-containing catalyst.

18. 18. The process of claim 17, wherein the decomposed second ammonia stream is passed from the first of the two or more secondary ammonia decomposition reactors to the second of the two or more secondary ammonia decomposition reactors without an intermediate heating step.

19. A process according to any preceding claim, wherein the parallel decomposition paths comprise one or more heaters, preferably one or more electric heaters.

20. 20. The process of claim 19, comprising reheating the decomposed second ammonia stream using a heater to produce a reheated decomposed second ammonia stream.

21. 21. The process of claim 20, comprising feeding the reheated decomposed second ammonia stream to one or more subsequent secondary ammonia decomposition reactors.

22. 22. The process of claim 21, wherein the second decomposed 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. 22. The process of 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 process of any one of claims 1 to 23, wherein the first hydrogen-containing stream and / or the second hydrogen-containing stream comprise an equilibrium mixture of hydrogen, nitrogen, and ammonia.

Images