Ammonia dissociation method and system

Abstract

A process for dissociating ammonia into a dissociated hydrogen / nitrogen stream in a catalyst tube within a radiant tube furnace and an adiabatic or isothermal unit containing a catalyst, and a downstream purification process unit for purifying the dissociated hydrogen / nitrogen stream into a high purity hydrogen product.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 353,402, filed on June 17, 2022, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates to systems and methods for dissociating ammonia into nitrogen and hydrogen. In embodiments, the systems and methods may be configured to dissociate ammonia into nitrogen and hydrogen in one or more reactors.

[0004] background

[0005] The world is moving towards decarbonization of energy processes, i.e. clean energy. Ammonia has been identified as the most promising carbon-free long-distance energy carrier when understood as a carrier of hydrogen. Storing gaseous hydrogen and transporting it to end users is costly. The high storage and transportation costs of hydrogen are mainly attributed to the expense of using high-pressure tanks and pipelines used to contain the gas.

[0006] There are increasing opportunities and demands to dissociate ammonia back into a mixture of hydrogen and nitrogen and then use the resulting hydrogen as a clean product or fuel. Therefore, ammonia can serve as an important energy carrier and be used to make hydrogen. For example, ammonia can be used as a fuel carrier for generating electricity in areas where there are few or no fuel sources. Additionally and alternatively, hydrogen can also be transported in pipelines and supplied to various industries as a clean product and / or fuel. In addition, as an energy carrier, ammonia can also serve as an energy source to balance the fluctuating power generation of renewable energy technologies such as wind, solar, and hydropower. The advantage of ammonia as an energy carrier is that liquid ammonia is easier to transport and store than natural gas or hydrogen gas.

[0007] Green and blue ammonia can be produced in remote areas where raw material costs are low or abundant. Green ammonia and blue ammonia are produced in remote areas where raw material costs are low (such as natural gas for blue ammonia) or resources are abundant (such as wind, solar, and hydropower for green ammonia). "Green ammonia" is defined herein as ammonia produced by a 100% renewable and carbon-free method. "Blue ammonia" is defined herein as ammonia produced by a low-carbon method, for example, ammonia produced by reforming a natural gas stream with carbon capture and underground storage.

[0008] It would be desirable to find efficient methods for dissociating ammonia (NH 3 ) into relatively high purity hydrogen (H 2 ) and nitrogen (N 2 ), particularly to make the hydrogen useful as a clean product and / or fuel source.

[0009] Overview

[0010] Embodiments of ammonia dissociation methods and systems are described herein that may substantially obviate one or more problems due to limitations and disadvantages of the related art.

[0011] Additional features and advantages of the embodiments will be described in the following description, and some will be apparent from the description or can be learned through the practice of the method and / or system. The objectives and other advantages will be realized and achieved by the method and / or system particularly pointed out in its written description and claims and the accompanying drawings.

[0012] In an embodiment, a method for dissociating ammonia into hydrogen and nitrogen is provided, which may include preheating a liquid ammonia feed in a first preheater to produce a preheated liquid ammonia stream while recovering heat from the dissociated hydrogen / nitrogen stream; vaporizing the preheated liquid ammonia feed to produce a vaporized ammonia stream; dissociating at least a portion of the vaporized ammonia stream to produce a dissociated hydrogen / nitrogen stream by: feeding the vaporized ammonia stream to a first reactor to produce a reactor effluent, and feeding the reactor effluent to a radiant tube reactor provided in an ammonia dissociation furnace; and feeding a low-carbon fuel of tail gas from a pressure swing adsorption, an unpurified mixture product from an ammonia scrubber, the vaporized ammonia stream, or a combination thereof to the ammonia dissociation furnace.

[0013] In an embodiment, dissociating the vaporized ammonia stream may include contacting the vaporized ammonia stream with one or more catalysts, the one or more catalysts including an alkali metal catalyst, a noble metal-based catalyst, or a combination thereof. In an embodiment, the alkali metal catalyst may include a nickel-based catalyst. In an embodiment, the noble metal-based catalyst may include ruthenium.

[0014] In an embodiment, feeding the vaporized ammonia stream to the first reactor may include feeding the vaporized ammonia stream to an adiabatic reactor or to an isothermal unit.

[0015] In an embodiment, feeding the vaporized ammonia stream to the first reactor may include sending the vaporized ammonia stream to an isothermal unit configured to recover heat from the dissociated hydrogen / nitrogen stream.

[0016] In an embodiment, the method may include recovering heat from a convection portion of the ammonia dissociation furnace to heat a boiler feed water stream.

[0017] In an embodiment, the method may include recovering heat from a convection portion of the ammonia dissociation furnace to produce steam, where the steam may be directed to a steam drum. In an embodiment, the steam may be used to heat an ammonia distillation unit downstream of the ammonia dissociation furnace, or alternatively exported from the unit. In an embodiment, the method may include using the steam to supply heat for vaporization of a preheated liquid ammonia feed.

[0018] In an embodiment, the method may include recovering heat from a convection portion of the ammonia dissociator furnace to heat an ammonia distillation unit downstream of the ammonia dissociator furnace.

[0019] In an embodiment, the method may include preheating at least a portion of the fuel via one or more coils located in a convection portion of the ammonia dissociation furnace.

[0020] In an embodiment, the method may include feeding a gas turbine exhaust gas to an ammonia dissociator furnace to supply combustion air to one or more burners of the ammonia dissociator furnace.

[0021] In an embodiment, vaporizing the preheated liquid ammonia feed may include recovering heat from the dissociated hydrogen / nitrogen stream prior to a preheater recovering heat from the dissociated hydrogen / nitrogen stream.

[0022] In an embodiment, the process may include feeding the dissociated hydrogen / nitrogen stream to a purification process after the preheater has recovered heat from the dissociated hydrogen / nitrogen stream to produce a hydrogen product stream having a hydrogen concentration ranging from 75 mol % to about 99.99999 mol %.

[0023] In an embodiment, a method for dissociating ammonia into hydrogen and nitrogen is disclosed, which may include feeding a vaporized ammonia stream into an adiabatic reactor comprising one or more catalysts to dissociate the ammonia; feeding an effluent reactor stream of the adiabatic reactor to one or more radiant tubes located in a radiant reactor portion of an ammonia dissociation furnace to produce a dissociated hydrogen / nitrogen stream, wherein the ammonia dissociation furnace includes a convection portion; and transferring heat from the convection portion of the ammonia dissociation furnace to an ammonia distillation unit.

[0024] In an embodiment, the method may include generating steam by recovering heat from the dissociated hydrogen / nitrogen stream.

[0025] In an embodiment, the method may include feeding the dissociated hydrogen / nitrogen stream to an ammonia scrubber, which is configured to remove unreacted ammonia from the dissociated hydrogen / nitrogen stream with wash water to produce a hydrogen-nitrogen gas mixture and an ammonia aqueous solution; and feeding the ammonia aqueous solution to an ammonia distillation unit for recovering unreacted ammonia and wash water.

[0026] In an embodiment, a method for dissociating ammonia into hydrogen and nitrogen is disclosed, which may include dissociating ammonia from a vaporized ammonia stream under isothermal conditions to produce a reactor effluent while the temperature of the entire reactor is constant, while recovering heat from the dissociated hydrogen / nitrogen stream, and feeding the reactor effluent to a radiant tube reactor to dissociate the ammonia present in the reactor effluent, thereby outputting a dissociated hydrogen / nitrogen stream.

[0027] In an embodiment, a system for dissociating ammonia into hydrogen and nitrogen is disclosed, the system may include an ammonia dissociation furnace, the ammonia dissociation furnace may include a convection section and a radiation section. The system may include a preheater heat exchanger arranged to receive a liquid ammonia feed and a dissociated hydrogen / nitrogen stream, the preheater heat exchanger being configured to transfer heat from the dissociated hydrogen / nitrogen stream to the liquid ammonia feed and produce a preheated ammonia stream. The system may include a vaporizer downstream of the preheater, which is configured to vaporize the preheated ammonia stream to produce a vaporized ammonia stream. The system may include a first reactor configured to receive a vaporized ammonia stream, the first reactor including an adiabatic reactor or an isothermal unit. The system may include a radiant tube reactor, the radiant tube reactor being located in the radiation section, downstream of the first reactor, and being configured to receive a reactor effluent from the first reactor and output a dissociated hydrogen / nitrogen stream. The system may include a low-carbon fuel fed to the ammonia dissociation furnace from a pressure swing adsorption, an ammonia scrubber, a vaporizer, or a combination thereof.

[0028] In an embodiment, the first reactor may include an adiabatic reactor including an inlet condition temperature ranging from about 500°C to about 750°C and an outlet condition temperature ranging from about 300°C to about 550°C; or an isothermal unit including an inlet condition temperature ranging from about 300°C to about 650°C and an outlet condition temperature ranging from about 300°C to about 600°C.

[0029] The system may include a steam generation portion that may include one or more coils in a convection portion of an ammonia dissociation furnace configured to recover heat from the ammonia dissociation furnace and utilize heat in the steam in a process.

[0030] In an embodiment, a system for dissociating ammonia into hydrogen and nitrogen is disclosed, the system may include an ammonia dissociation furnace, the ammonia dissociation furnace may include a convection portion and a radiant reactor portion. In an embodiment, the system may include an ammonia distillation reboiler portion located in the convection portion of the ammonia dissociation furnace, the ammonia distillation reboiler portion is thermally coupled to the ammonia distillation unit and includes one or more coils, the one or more coils being configured to recover heat from the convection portion of the ammonia dissociation furnace. The system may include an adiabatic reactor comprising one or more catalysts for dissociating ammonia and a reactor effluent. The system may include one or more radiant tubes located in the radiant reactor portion of the ammonia dissociation furnace, which are configured to receive the reactor effluent from the adiabatic reactor and output a dissociated hydrogen / nitrogen stream.

[0031] In an embodiment, the system may include a heat exchanger functionally connected to the steam drum and arranged to generate steam by recovering heat from the dissociated hydrogen / nitrogen stream.

[0032] In an embodiment, the system may include gas turbine exhaust fed to one or more combustors located in an ammonia dissociation furnace.

[0033] In an embodiment, the system may include an ammonia scrubber connected to the ammonia distillation reboiler section, the ammonia scrubber being arranged to receive a dissociated hydrogen / nitrogen stream and being configured to remove unreacted ammonia from the dissociated hydrogen / nitrogen stream with scrubbing water to produce a hydrogen-nitrogen gas mixture and an ammonia aqueous solution, wherein the ammonia aqueous solution is directed to an ammonia distillation unit for recovering unreacted ammonia and scrubbing water.

[0034] In an embodiment, a system for dissociating ammonia into hydrogen and nitrogen is disclosed, which may include an isothermal unit configured to receive a vaporized ammonia stream and recover heat from a dissociated hydrogen / nitrogen stream, and a radiant tube reactor downstream of the isothermal unit configured to receive a reactor effluent from the isothermal unit and output a dissociated hydrogen / nitrogen stream.

[0035] In an embodiment, the isothermal unit may include a reactor and heat exchanger, and the ammonia-containing stream has an inlet condition temperature ranging from about 300°C to about 650°C and an outlet condition temperature ranging from about 300°C to about 600°C.

[0036] In an embodiment, a radiant tube reactor may include one or more radiant tubes located in a radiant reactor portion of an ammonia dissociation furnace including a convection portion.

[0037] In an embodiment, one or more of the systems discussed above may include an ammonia scrubber for receiving the dissociated hydrogen / nitrogen stream, the ammonia scrubber being configured to remove unreacted ammonia from the dissociated hydrogen / nitrogen stream with scrubbing water to produce a hydrogen-nitrogen gas mixture.

[0038] In an embodiment, one or more of the systems discussed above may include a pressure swing adsorption unit configured to receive a hydrogen-nitrogen gas mixture from an ammonia scrubber, the pressure swing adsorption unit configured to purify the hydrogen-nitrogen gas mixture to obtain a hydrogen product stream having a hydrogen concentration of 75 mol % to 99.99999 mol %.

[0039] In an embodiment, a pressure swing adsorption unit may include a flue gas effluent directed to an ammonia dissociator furnace for use as fuel.

[0040] As further illustrated by the embodiments described below, any two or more of the method steps and / or system features described above may be combined. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic block flow diagram of one embodiment of a system and method for dissociating ammonia using an adiabatic first stage dissociation process as described herein.

[0043] Figure 2 is a schematic block flow diagram of another embodiment of a system and method for dissociating ammonia using an adiabatic first stage dissociation process as described herein.

[0044] Figure 3 is a schematic block flow diagram of one embodiment of a system and method for dissociating ammonia implementing an isothermal first stage dissociation process as described herein.

[0045] It will be understood that the drawings are schematic illustrations only and that the present invention is not limited to the arrangements, proportions or specific devices shown in the drawings.

[0046] Details

[0047] In embodiments, the present disclosure describes a system and method for dissociating ammonia in one or more reactors. In embodiments, the system and method can dissociate ammonia into hydrogen and nitrogen. In embodiments, the system and method can produce a hydrogen product stream. In embodiments, the system and method can produce a high purity hydrogen product stream.

[0048] In embodiments, the hydrogen product stream can have various uses. In embodiments, the high purity hydrogen product stream can be used in fuel cells. Fuel cells can be used as generators. In embodiments, fuel cells can be used to power vehicles. In embodiments, fuel cells can be used in power plants. In embodiments, the hydrogen product stream can also be used in pipelines. In embodiments, the hydrogen product stream can be used in the steel and cement industries. In embodiments, the hydrogen product stream can be used in industrial facilities. In embodiments, the hydrogen product stream can be used as a clean burning fuel for power plants and / or other occasions. Therefore, the methods and systems described herein can help provide hydrogen product streams for these and other uses.

[0049] In an embodiment, the dissociation may be performed in one or more reactors. In an embodiment, the dissociation of ammonia may be performed in the presence of one or more catalysts. In an embodiment, one or more catalysts may be provided in one or more reactors. In an embodiment, the one or more reactors may include a first reactor and a second reactor. In an embodiment, the second reactor may be located downstream of the first reactor.

[0050] In an embodiment, the first reactor may include an adiabatic reactor or an isothermal unit. In an embodiment, the second reactor may include a radiant tube reactor. In an embodiment, the second reactor may include a down-fired furnace.

[0051] In an embodiment, the second reactor may be a radiant portion of an ammonia dissociation furnace. In an embodiment, one or more reactors may include an adiabatic reactor and a top-fired furnace and / or a radiant tube reactor. In an embodiment, one or more reactors may include an isothermal unit and a top-fired furnace and / or a radiant tube reactor.

[0052] In embodiments, systems and methods may include generating steam for use as a heat source in one or more portions of the process and / or other applications. In embodiments, the steam may be generated by recovering heat from a convection portion of an ammonia dissociation furnace. In embodiments, the steam may be generated by recovering heat from a dissociated hydrogen / nitrogen stream generated by a second reactor, such as a radiant tube reactor.

[0053] In embodiments, the systems and methods herein provide heat recovery to preheat and / or vaporize the ammonia feed. In embodiments, energy or heat recovery may be from a dissociated hydrogen / nitrogen stream produced by a second reactor, such as a radiant tube reactor.

[0054] In embodiments, the systems and methods may optionally include a downstream purification process system. In embodiments, the purification process system may include one or more units to purify the dissociated hydrogen / nitrogen stream into a high purity hydrogen product stream. In embodiments, the purification process system may be after cooling the dissociated hydrogen / nitrogen stream resulting from heat recovery for preheating and / or vaporizing ammonia feed. In embodiments, the purification process may include the use of an ammonia distillation unit. In embodiments, the methods and systems may provide heat recovery from an ammonia dissociation furnace to provide heat for the ammonia distillation unit.

[0055] In embodiments, the system or method may achieve zero direct carbon emissions and be self-sufficient in terms of fuel required for ammonia dissociation. In embodiments, the system or method may use any number of streams within the process as fuel, either alone or in combination. For example, a clean fuel source from within the process may be vaporized ammonia, an unpurified hydrogen-nitrogen mixture downstream of an ammonia scrubber, waste or tail gas from a PSA, or a combination thereof. In embodiments, the system or method may not require the input of natural gas for ammonia dissociation.

[0056] In an embodiment, the system or method can be self-sufficient in terms of the hot utility required within the method, thereby minimizing the integration with external units and reducing the costs associated with external support units. In an embodiment, the heat required for the tower reboiler of the ammonia distillation unit can be supplied by steam generated in the method or system through the available heat in the convection section of the ammonia dissociation furnace. In an embodiment, the method or system can utilize the available heat in the system and transport the heat to where it is needed by using steam as a medium. In an embodiment, the heat required for the ammonia distillation unit and / or its reboiler can be directly supplied by heat exchange using coils in the convection section of the ammonia dissociation furnace, and the coil gas from the ammonia distillation unit can pass through the coils, directly utilizing the available heat in the system.

[0057] Reference will now be made in detail to the embodiments of the present invention illustrated in the accompanying drawings.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the invention belongs. Unless otherwise indicated, all patents, patent applications, published applications and publications, websites and other public materials mentioned in the entire disclosure of this article are incorporated herein by reference in their entirety. If there are multiple definitions of terms in this article, the definitions in this section shall prevail. When referring to URLs or other such identifiers or addresses, it should be understood that such identifiers may change, and information on the Internet may come and go, but equivalent information can be found by searching the Internet. Mentioning this information proves the availability and public dissemination of such information.

[0059] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0060] As used herein, ranges and quantities may be expressed as "about" a particular value or range. "About" also includes the exact amount. Thus, "about 5%" means not only 5%, but also about 5%. The term "about" means within the normal experimental error range for the application or intended purpose.

[0061] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0062] As used herein, "combination" refers to any association between two items or more than two items. The association may be spatial or may refer to two or more items being used for a common purpose.

[0063] The words "comprising" and "comprises" as used in the claims should be interpreted to mean "including but not limited to" and "including but not limited to", respectively.

[0064] As used herein, "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and the description includes instances where the event or circumstance occurs and instances where it does not occur. For example, an optional component in a system means that the component may or may not be present in the system.

[0065] The word "substantially" as used herein means "generally but not entirely what is specified."

[0066] The term first, second, third etc. used herein can describe various elements, components, regions, layers and / or parts, and these elements, components, regions, layers and / or parts should not be limited by these terms. These terms may only be used to distinguish an element, component, region, layer or part from another region, layer or part. Unless the context is clearly stated, otherwise the terms used herein such as "first", "second" and other numerical terms do not mean order or sequence. Therefore, the first element, component, region, layer or part discussed below can be referred to as the second element, component, region, layer or part, without departing from the teaching of the embodiment.

[0067] Figure 1 An embodiment of a system 10 for ammonia dissociation is described. In an embodiment, a liquid ammonia feed 12 may be supplied. In an embodiment, the liquid ammonia feed 12 may come from a battery limit (e.g., from an atmospheric storage tank). Other sources may also be used. In an embodiment, the liquid ammonia feed may include a high ammonia concentration. In an embodiment, the ammonia concentration in the liquid ammonia feed 12 may range from about 99.5 wt % to about 99.8 wt %. In an embodiment, the balance of the liquid ammonia feed 12 may be water. In an embodiment, the liquid ammonia feed 12 may include a composition comprising about 99.8 wt % ammonia and 0.2 wt % water.

[0068] In an embodiment, the system may include a preheater 14 configured in stage (A) to preheat the liquid ammonia feed 12 to a near boiling temperature. In an embodiment, the liquid ammonia feed 12 may be preheated to about 30°C to about 100°C to form a preheated liquid ammonia stream 16. In an embodiment, the preheater 14 may be any type of heater. In an embodiment, the preheater 14 may include a process exchanger heat exchanger. In an embodiment, preheating the liquid ammonia feed 12 in the first preheater 14 to produce a preheated liquid ammonia stream 16 may be performed while recovering heat from the dissociated hydrogen / nitrogen stream 20. In an embodiment, the preheating of stage (A) may be performed using waste heat from the dissociated hydrogen / nitrogen stream 20, as described in more detail below. In an embodiment, the preheater 14 may be configured to recover heat from the dissociated hydrogen / nitrogen stream 20. In an embodiment, the preheater 14 may be configured to transfer heat from the dissociated hydrogen / nitrogen stream 20 to the liquid ammonia feed 12 to produce a preheated liquid ammonia stream 16. In an embodiment, the implementation of the preheater 14 may utilize the waste heat from the dissociated hydrogen / nitrogen stream 20 for stage (A) preheating, which may improve the heat integration of the system and thus provide higher energy efficiency.

[0069] In an embodiment, the system may include a vaporizer 18 located downstream of the preheater 14. In an embodiment, in stage (B), the preheated liquid ammonia stream 16 from stage (A) may be vaporized in the vaporizer 18 to produce a vaporized ammonia stream 24. In an embodiment, the vaporizer 18 may be any type of vaporizer. In an embodiment, the vaporizer 18 may include heat transfer from the process. In an embodiment, the vaporizer 18 may be configured to recover heat from the dissociated hydrogen / nitrogen stream 20. In an embodiment, the vaporizer 18 may vaporize the preheated liquid ammonia stream 16 by transferring heat from the dissociated hydrogen / nitrogen stream 20 and / or cooling the dissociated hydrogen / nitrogen stream 20 and condensing the remaining low-pressure vapor. In an embodiment, the low-pressure vapor may be supplied by the output of the superheated vapor section 62 stage (M), the steam drum 64, the output vapor from the ammonia distillation unit 46, and / or from an external stream source 22.

[0070] In an embodiment, the system may include one or more heating devices to further heat the vaporized ammonia stream 24, thereby producing a heated ammonia vapor stream 32. In an embodiment, the vaporized ammonia stream 24 may be further heated. In an embodiment, in stage (C), the vaporized ammonia stream 24 may be further heated using a feed / effluent exchanger 26. In an embodiment, the feed / effluent exchanger 26 may be configured to heat the vaporized ammonia stream 24 to a range of about 90°C to about 500°C. In an embodiment, the feed / effluent exchanger 26 may include a heat exchanger. In an embodiment, the feed / effluent exchanger 26 may be configured to recover heat from the dissociated hydrogen / nitrogen stream 20. In an embodiment, the feed / effluent exchanger 26 may be configured to transfer heat from the dissociated hydrogen / nitrogen stream 20 to the vaporized ammonia stream 24.

[0071] In an embodiment, the system may include an ammonia dissociation furnace 30. In an embodiment, the ammonia dissociation furnace 30 may be configured with a radiant section 40 and a convection section 28 for second stage ammonia dissociation in catalytic dissociation.

[0072] In an embodiment, in stage (D), the vaporized ammonia stream 24 may be heated in the convection portion 28 of the ammonia dissociation furnace 30 .

[0073] In an embodiment, the convection portion 28 of the ammonia dissociation furnace 30 may include one or more optional components.

[0074] In an embodiment, the convection section 28 of the ammonia dissociation furnace 30 may optionally include a high pressure (up to about 120 bar), medium pressure (up to about 60 bar), or low pressure (e.g., up to about 10 bar) steam generation section 60 (also identified as stage L). In an embodiment, the steam generation section 60 may include one or more coils located in the convection section 28 of the ammonia dissociation furnace 30. In an embodiment, the steam generation section 60 may be configured to recover heat from the convection section 28. In an embodiment, the steam generation section 60 may be functionally coupled to a steam drum 64 and used to generate steam at a pressure of about 3 bar to about 120 bar. In an embodiment, using the generated steam as a medium, available heat in the system can be utilized and transported to where it may be desired. In an embodiment, the effluent from the steam generation section 60 and / or the effluent from the steam drum 64 can be used to provide heat to an ammonia distillation unit 46, which can be used as part of a hydrogen purification method, as described in more detail below. In an embodiment, the same steam can also be used to provide steam and / or heat to the vaporizer 18 to vaporize the preheated liquid ammonia stream 16. For example, after providing heat to the ammonia distillation unit 46, the same steam can also be used to provide steam and / or heat to the vaporizer 18 to vaporize the preheated liquid ammonia stream 16.

[0075] In an embodiment, the convection portion 28 of the ammonia dissociation furnace 30 may optionally include a superheated steam portion 62 (also identified as stage M). In an embodiment, the superheated steam portion 62 may be functionally coupled to a steam drum 64. For clarity, Figure 1 The steam lines in are depicted with dashed lines. In an embodiment, the superheated steam portion 62 may include one or more coils in the convection portion of the ammonia dissociation furnace 30. In an embodiment, the superheated steam portion 62 may be configured to recover heat from the convection portion 28. In an embodiment, the superheated steam portion 62 may be configured to superheat the steam from 140°C to about 550°C. In an embodiment, the superheated steam from the superheated steam portion 62 may be used as a heat source for one or more other components. In an embodiment, the effluent of the superheated steam portion 62 may be used to provide heat for the ammonia distillation unit 46, which may be part of the hydrogen purification method, as described in more detail below. In addition, in an embodiment, after the ammonia distillation unit 46, the effluent of the superheated steam portion 62 may be used to provide heat to vaporize the preheated liquid ammonia stream 16 in the vaporizer 18. In an embodiment, this can utilize the heat available in the system and transport the heat to where it may be desired by using steam as a medium.

[0076] In an embodiment, the method and system can be self-sufficient in terms of heat utility requirements. In an embodiment, using steam from the steam drum 64, the effluent of the steam generation section 60, and / or the superheated steam from the superheated steam section 62 as a medium for transporting heat to one or more other components can make the method and system self-sufficient in terms of heat utility requirements.

[0077] In an embodiment, the convection section 28 of the ammonia dissociation furnace 30 may optionally include a boiler feed water stream (BFW) preheating section 66 (also identified as stage N). In an embodiment, the BFW preheating section 66 may include one or more coils in the convection section 28 of the ammonia dissociation furnace 30. In an embodiment, the BFW preheating section 66 may be configured to recover heat from the convection section 28. In an embodiment, the BFW preheating section 66 may be configured to heat the BFW in a range of about 130° C. to about 350° C. In an embodiment, the heated BFW may be fed to the steam drum 64.

[0078] In an embodiment, the convection section 28 of the ammonia dissociation furnace 30 may optionally include a selective catalytic NOx reduction (SCR) section 68 (also referred to as stage O). In an embodiment, the SCR section 68 may be configured to inject an ammonia solution atomized by air into the NOx-containing flue gas produced by the ammonia dissociation furnace 30, and contact the mixture with a catalyst bed configured to react ammonia with NOx to generate nitrogen and water vapor and / or expose the mixture to a catalyst bed that reacts ammonia with NOx to generate nitrogen and water vapor. In this way, the emission of NOx to the atmosphere can be reduced and / or eliminated. In an embodiment, the SCR section 68 may be configured to recover heat from the convection section 28. In an embodiment, the ammonia solution injected into the SCR section 68 may come from a portion of the vaporized ammonia stream 24 and / or ammonia vapor 76, such as shown in the figure.

[0079] In an embodiment, the convection section 28 of the ammonia dissociation furnace 30 may optionally include a combustion air preheating section 70 (also identified as stage P). In an embodiment, the combustion air preheating section 70 may include one or more coils for recovering heat to the combustion air preheating section 70. In an embodiment, the combustion air 70 may be heated at any temperature from about 100 to about 600° C. In an embodiment, the heated combustion air may be provided to the radiant section 40 of the ammonia dissociation furnace 30 as a source of oxygen for burning the fuel.

[0080] In an embodiment, the gas turbine exhaust gas 92 may optionally be input into the system and method 10. In an embodiment, the gas turbine exhaust gas 92 may be enriched with oxygen. In an embodiment, the gas turbine exhaust gas 92 may therefore also optionally be used as combustion air for use in the burners of the radiant section 40 of the ammonia dissociation furnace 30 to combust fuel. In an embodiment, the gas turbine exhaust gas 92 may be fed to the burners of the radiant section 40 either alone or as a mixed flow with the heated combustion air from the combustion air preheating section 70.

[0081] In an embodiment, the convection section 28 of the ammonia dissociation furnace 30 may optionally include a fuel preheating section 84 (also identified as stage Q). In an embodiment, the fuel preheating section 84 may be used to preheat one or more fuels used in the radiant section 40 of the ammonia dissociation furnace 30. In an embodiment, as shown, the fuel preheating section 84 may be used to preheat at least a portion of the fuel from the exhaust or tail gas 54, and a portion 74 of the hydrogen-nitrogen gas mixture 72 when mixed with the exhaust or tail gas 54. In an embodiment, the fuel preheating section 84 may include one or more coils for recovering heat into preheating one or more fuels. In an embodiment, the fuel may be heated in the range of about 100 to about 250°C.

[0082] In an embodiment, the convection section 28 of the ammonia dissociation furnace 30 may optionally include a water preheating section 86 (also identified as stage R). In an embodiment, the water preheating section 86 may be used to preheat water for use as a heat source (heat facility) outside the facility. In an embodiment, the water preheating section 86 may include one or more coils for recovering heat into the preheated water.

[0083] In an embodiment, the convection section 28 of the ammonia dissociator 30 may optionally include an ammonia distillation reboiler section 88 (also identified as stage S). In an embodiment, the ammonia distillation reboiler section 88 may be configured to provide heat to the ammonia distillation unit 46 by recovering heat directly from the convection section of the ammonia dissociator, making the process self-sufficient in terms of thermal utility requirements. In an embodiment, the ammonia distillation reboiler section 88 may include one or more coils for recovering heat for regeneration of ammonia distillation (step I) in the ammonia distillation unit 46. In an embodiment, the gas forming the ammonia distillation unit 46 may be circulated through one or more coils in the ammonia distillation reboiler section 88 of the convection section 28 of the ammonia dissociator 30 through one or more conduits as shown to recover heat from the convection section 28.

[0084] In an embodiment, the convection portion 28 of the ammonia dissociation furnace 30 may include any combination of one or more of the above-described optional components. In an embodiment, the convection portion 28 of the ammonia dissociation furnace 30 may include one or more optional components in addition to at least stages (D) and (F) described herein. In an embodiment, the convection portion 28 of the ammonia dissociation furnace 30 may include, in addition to, for example, Figure 1-3 In addition to the illustrated stages (D) and (F), combinations of all the above components may also be included. Figure 1-3 All are shown as existing in the reference Figure 1-3 In any of the embodiments described, any combination or subcombination of any one or more of the optional components in the convection section 28 may be present in addition to stages (D) and (F).

[0085] In an embodiment, the convection portion 28 of the ammonia dissociation furnace 30 may be configured to increase the temperature of the vaporized ammonia stream 24 by about 300° C. to about 600° C. In an embodiment, the vaporized ammonia stream 24 may be further heated first by passing through the feed / effluent exchanger 26 at stage (C) and secondly in the convection portion 28 of the ammonia dissociation furnace 30 at stage (D) to produce a heated ammonia vapor stream 32. In an embodiment, the heated ammonia vapor stream 32 may have a temperature ranging from about 500° C. to about 750° C.

[0086] In an embodiment, the system may include a first reactor. In an embodiment, the system may include an adiabatic reactor 34 as a first reactor. In an embodiment, in stage (E), the system and method may include an adiabatic first stage dissociation. In an embodiment, in stage (E), a heated ammonia vapor stream 32 may be fed to an adiabatic reactor 34. In an embodiment, the adiabatic reactor 34 may include a reactor. In an embodiment, the reactor may include a catalyst bed. In an embodiment, the adiabatic reactor 34 for the first stage dissociation may be loaded with one or more suitable catalysts for the dissociation of ammonia. In an embodiment, in the adiabatic reactor 34, the heated ammonia vapor may be exposed to one or more catalysts and / or contacted with one or more catalysts. In an embodiment, the one or more catalysts may be alkali metals (e.g., Ni, Co, Fe), noble metals (e.g., Ru), or any combination thereof. In an embodiment, the adiabatic reactor 34 may be loaded with a nickel-based catalyst, a ruthenium-based catalyst, or a combination thereof and / or in combination with any other suitable catalyst. In an embodiment, a nickel-based catalyst may provide enhanced activity. In an embodiment, a ruthenium-based catalyst may provide better conversion and relatively better balance.

[0087] In an embodiment, the reactor 34 may be configured such that at least a portion of the ammonia in the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 dissociates into hydrogen and nitrogen following reaction (Z):

[0088]

[0089] catalyst

[0090] In embodiments, not all of the ammonia from the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 is dissociated in the adiabatic reactor 34. Thus, in embodiments, the first reactor effluent 36 may contain hydrogen, nitrogen, water, unreacted ammonia vapor, or any combination thereof.

[0091] The dissociation reaction (Z) is an endothermic reaction. Therefore, the reaction requires cracking heat. In an embodiment, the required cracking heat may be about 0.65Gcal / MT, 12% of the ammonia energy. For the purpose of this description, it is assumed that ΔH298 is 46kJmol-1NH3. In addition, in an embodiment, due to the endothermic nature of the dissociation reaction, the first reactor effluent 36 of the adiabatic reactor 34 may have a lower temperature than the heated ammonia vapor stream 32 fed to the adiabatic reactor 34.

[0092] In an embodiment, the inlet conditions of the adiabatic reactor 34 may be about 20 bar to about 50 bar, such as 25 bar to about 40 bar. In an embodiment, the inlet pressure may be in any sub-range of those recorded. In an embodiment, the inlet conditions of the adiabatic reactor 34 may have a temperature range of about 500°C to about 750°C, such as about 550°C to about 675°C. In an embodiment, the inlet temperature may be in any sub-range of those recorded. In an embodiment, the outlet temperature of the reactor 34 may have a temperature range of about 300°C to about 550°C, such as about 300°C to about 500°C. In an embodiment, the outlet temperature may be in any sub-range of those recorded.

[0093] In embodiments, the methods and systems may include a second stage dissociation in order to convert at least a portion of the ammonia from the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 remaining in the first reactor effluent 36. In embodiments, the second stage dissociation may include the use of a second reactor, such as described below with reference to the radiant portion 40 of the ammonia dissociation furnace 30.

[0094] In an embodiment, the method herein may include a stage (F) of heating the first reactor effluent 36. In an embodiment, the system may include one or more coils in the first reactor effluent heating section 38 of the convection section 28, which are configured to direct the first reactor effluent 36 through the convection section 28 of the ammonia dissociation furnace 30 for heating before reaching the radiation section 40.

[0095] In an embodiment, the first reactor effluent 36 may be fed to the second reactor in stage (G) after being heated in the first reactor effluent heating section 38 of the ammonia dissociation furnace 30. In an embodiment, the second reactor may include the radiant section 40 of the ammonia dissociation furnace 30 for the second stage dissociation process.

[0096] In an embodiment, the radiant portion 40 of the ammonia dissociation furnace 30 may include one or more catalyst filled tubes 80. In an embodiment, the catalyst filled tubes 80 may be arranged in one or more rows 82. In an embodiment, as shown, the rows 82 may be vertical rows. In an embodiment, each row 82 may include one or more tubes 80. In an embodiment, the arrangement may resemble a harp (not shown).

[0097] In embodiments, at least some of the ammonia remaining in the first reactor effluent 36 in the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 may be dissociated into hydrogen and nitrogen within the one or more catalyst-filled tubes 80 by a reaction mechanism similar to reaction (Z). In embodiments, the second stage dissociation process in the radiant section 40 may include "near isothermal dissociation," in which heat is supplied by combustion of one or more fuels; "heat input dissociation," in which heat is supplied by a hot stream; and / or "energy input dissociation," in which heat is provided by electrical energy input.

[0098] In an embodiment, the radiation section 40 may include a variety of possible designs. In an embodiment, the radiation section 40 may include a radiation tube reactor, an electrochemical reactor, or a combination thereof. Other designs may also be implemented alone or in combination. In an embodiment, the radiation section 40 may include one or more burners (not shown). In an embodiment, heat may be provided for the dissociation of ammonia by burning fuel. In an embodiment, the radiation section 40 may include a top-fired furnace, a side-fired furnace, a bottom-fired furnace, and / or a combination thereof. For example, in a top-fired furnace, the flame direction is from the top of the furnace to the bottom.

[0099] In an embodiment, heat for the ammonia dissociation furnace 30 and / or convection section 28 may be provided by the radiant section 40. In an embodiment, heat for the ammonia dissociation furnace 30 and / or convection section 28 may be provided by burning fuel, electrical energy input, or a combination thereof.

[0100] In an embodiment, the tubes 80 of the second stage dissociation in the radiant section 40 may be loaded with one or more catalysts, as described with respect to the adiabatic reactor 34. In an embodiment, the same or different catalysts may be used for the radiant section 40 and the adiabatic reactor 34. In an embodiment, the tubes 80 of the second stage dissociation in the radiant section 40 may be loaded with nickel-based and / or ruthenium-based catalysts. Other catalysts may also be used alone or in combination. In an embodiment, ammonia that may still be present in the first reactor effluent 36 may be exposed to and / or contacted with one or more catalysts in the tubes 80 and / or the radiant section 40.

[0101] In an embodiment, the inlet pressure condition of the tube 80 may be about 20 bar to about 50 bar, such as about 25 bar to about 40 bar. In an embodiment, the inlet pressure may be in any sub-range of those noted. In an embodiment, the inlet temperature of the radiant tube 80 may be about 450° C. to about 700° C., such as about 525° C. to about 675° C. In an embodiment, the inlet temperature may be in any sub-range of those noted. In an embodiment, the outlet temperature of the tube 80 may range from about 500° C. to about 750° C., such as about 550° C. to about 700° C. In an embodiment, the outlet temperature may be in any sub-range of those noted.

[0102] In an embodiment, the effluent of the radiant section 40 is a dissociated hydrogen / nitrogen stream 20. In an embodiment, the dissociated hydrogen / nitrogen stream 20 exiting the catalyst tubes 80 of the radiant section 40 may comprise hydrogen, nitrogen, water, and a few percent of unreacted ammonia vapor.

[0103] In embodiments, heat may be recovered from the dissociated hydrogen / nitrogen stream 20 of the radiant section 40. In embodiments, the dissociated hydrogen / nitrogen stream 20 may be cooled by one or more of the feed / effluent exchanger 26 (stage C), the vaporizer 18 (stage B), and the preheater 14 (stage A), as previously discussed.

[0104] In embodiments, the dissociated hydrogen / nitrogen stream 20 may optionally undergo one or more purification and / or processes, as described with reference to stages H through K. In embodiments, one or more purification processes may be used to produce a high purity hydrogen product stream. In embodiments, the dissociated hydrogen / nitrogen stream 20 may have been cooled prior to entering the purification process. In embodiments, Figure 1-3 As illustrated, the dissociated hydrogen / nitrogen stream 20 may be fed to a purification process after heat has been recovered to preheat and / or vaporize the ammonia feed.

[0105] In an embodiment, in stage H, the dissociated hydrogen / nitrogen stream 20 may be fed to an ammonia scrubber 42. In an embodiment, the dissociated hydrogen / nitrogen stream 20 may be fed to the ammonia scrubber 42 after it has been cooled. In an embodiment, the dissociated hydrogen / nitrogen stream 20 may be fed to the ammonia scrubber 42 after the preheater 14 and / or the vaporizer 18 have recovered heat from the dissociated hydrogen / nitrogen stream 20. In an embodiment, in the ammonia scrubber 42, most of the unreacted ammonia in the dissociated hydrogen / nitrogen stream 20 may be removed by the scrubbing water 44. In an embodiment, the ammonia scrubber 42 may include one or more effluents. In an embodiment, the effluent of the ammonia scrubber 42 may include an aqueous ammonia solution 78. In an embodiment, the effluent of the ammonia scrubber 42 may include a hydrogen-nitrogen gas mixture 72. In an embodiment, the ammonia scrubber 42 may include a first effluent of the aqueous ammonia solution 78 and a second effluent of the hydrogen-nitrogen gas mixture 72.

[0106] In an embodiment, in stage I, the aqueous ammonia solution 78 from the ammonia scrubber 42 may be sent to the ammonia distillation unit 46. In an embodiment, the ammonia distillation unit 46 may include a distillation column. In an embodiment, the heat to the ammonia distillation unit 46 may be provided by steam and / or superheated steam from the steam drum 64, the steam generation section 60 and / or the superheated steam section 62, as discussed previously. As discussed previously, the available heat in the system can be utilized and the heat can be transported to where it may be desired by using steam as a medium. In an embodiment, the heat to the ammonia distillation unit 46 may be provided directly from the ammonia distillation reboiler section 88 (also referred to as stage S), directly utilizing the available heat in the system. In an embodiment, in the ammonia distillation unit 46, any unreacted ammonia 48 in the aqueous ammonia solution 78 may be separated from the wash water 44 and recycled to the inlet of the vaporizer 18 of stage B. In an embodiment, the unreacted ammonia 48 may be combined with the preheated liquid ammonia stream 16 before entering the vaporizer 18. The wash water 44 may be sent back to the ammonia scrubber 42 of stage H.

[0107] In an embodiment, the hydrogen-nitrogen gas mixture 72 exiting the ammonia scrubber 42 may include hydrogen, nitrogen, water, and less than 200 ppm of ammonia. In an embodiment, the hydrogen-nitrogen gas mixture 72 may include an ammonia concentration ranging from about 10 to about 200 ppm. In an embodiment, in stage J, the hydrogen-nitrogen gas mixture 72 may be sent to one or more pressure swing adsorption systems, units 50. In an embodiment, in the pressure swing adsorption unit 50, the hydrogen-nitrogen gas mixture 72 may be purified into a hydrogen product 52. In an embodiment, the hydrogen product 52 may have a hydrogen concentration ranging from 75 mol% to about 99.99999 mol%. In an embodiment, the hydrogen concentration of the hydrogen product 52 may be at least about 98 mol%. In an embodiment, the hydrogen concentration of the hydrogen product 52 may range from about 98 mol% to about 99.99999 mol%.

[0108] In an embodiment, the waste gas or tail gas 54 as a byproduct of the pressure swing adsorption unit 50 can be sent to the ammonia dissociation furnace 30. In an embodiment, the waste gas or tail gas 54 can be used as a low-carbon fuel for the ammonia dissociation furnace 30 and the radiant section 40. In an embodiment, the waste gas or tail gas 54 can be directed to the radiant section 40 of the ammonia dissociation furnace 30. In an embodiment, the waste gas or tail gas 54 can be used as a fuel for the radiant section 40 of the ammonia dissociation furnace 30.

[0109] In an embodiment, heat in the ammonia dissociation furnace 30 and the radiant section 40 may be provided by fuel and / or electricity. In an embodiment, heat is provided at least in part by electricity. In an embodiment, any fuel may be used to provide heat.

[0110] In an embodiment, the method or system described herein may exhibit zero direct carbon emissions and be self-sufficient in terms of fuel for ammonia dissociation. In an embodiment, the low-carbon fuel produced within the method or system can be used to power the ammonia dissociation furnace 30 and the radiant section 40. In an embodiment, the ammonia dissociation furnace 30 and the radiant section 40 can use the tail gas 54 from the pressure swing adsorption 50 as the main fuel, making it possible for the method or system to have zero direct carbon emissions and be self-sufficient in terms of fuel for dissociation. In an embodiment, the ammonia dissociation furnace 30 and the radiant section 40 can use at least a portion 74 of the hydrogen-nitrogen gas mixture 72 from the ammonia scrubber 42 as a low-carbon fuel. In an embodiment, a portion 74 of the hydrogen-nitrogen gas mixture 72 can be used as the main fuel or for supplemental fuel, making it possible for the method or system to have zero direct carbon emissions and be self-sufficient in terms of fuel for dissociation. In embodiments, the ammonia dissociation furnace 30 and the radiant section 40 may optionally use ammonia vapor 76 from the vaporizer 18 and / or a portion of the vaporized ammonia stream 24 as a low-carbon fuel, for example as a primary fuel or for supplemental fuel, making it possible for the method or system to have zero direct carbon emissions and be self-sufficient in terms of fuel for dissociation. In embodiments, any combination of two or more of the tail gas 54, the hydrogen-nitrogen gas mixture 72, and the ammonia vapor 76 may be used as fuel for the ammonia dissociation furnace 30 and the radiant section 40. In this way, in embodiments, a method or system as described herein may exhibit zero direct carbon emissions and be self-sufficient in terms of fuel for ammonia dissociation. Figure 1 In FIG. 1 , a portion 74 of the hydrogen-nitrogen gas mixture 72 and ammonia vapor 76 from the vaporizer 18 and / or as part of the vaporized ammonia stream 24 are indicated by dashed lines.

[0111] In embodiments not shown, natural gas may further be input into the process or system 10 for use as a fuel. In embodiments, the system and process may require and / or be free of natural gas feed since it may be self-sufficient in terms of fuel for dissociation as described above.

[0112] In an embodiment, in stage K, the hydrogen product 52 may be compressed in a compressor 56 to a pressure required by the region of interest to obtain a compressed hydrogen product 58 .

[0113] It will be understood that this document refers to Figure 1 The described method and system 10 includes at least one adiabatic reactor 34 as a first reactor and / or at least one radiation section 40 as a second reactor, but does not necessarily include both. In an embodiment, if there are both at least one first reactor or adiabatic reactor 34 and at least one second reactor or radiation section 40, the first reactor, such as the adiabatic reactor 34, is sequentially arranged before the second reactor or radiation section 40 of the ammonia dissociation furnace 30, such as Figure 1The schematic diagram is shown in the figure.

[0114] Figure 2 The diagram illustrates an embodiment of the system 10'. In the embodiment, the system 10' and Figure 1 The system 10 is similar to that of FIG. 1, but the steam generation system is modified. Figure 1 In comparison, Figure 2 In the embodiment, the steam generating portion 60 (stage L) is removed. For ease of reference, the modified and / or substituted elements are indicated by a prime symbol ('). Other corresponding elements have the same reference numerals. In the embodiment, Figure 2 The diagram illustrates a system in which the BFW may be optionally preheated in coils N of the BFW preheat section 66 before being fed to the steam drum 64'. In embodiments, heat may be recovered from the dissociated hydrogen / nitrogen stream 20 by a steam heat exchanger 94 to further generate and / or heat steam. In embodiments, water and / or steam may be circulated through the steam heat exchanger 94 to recover heat from the dissociated hydrogen / nitrogen stream 20 and then returned to the steam drum 64'. In embodiments, steam may optionally be generated from the superheat section 62 in stage M. In embodiments, steam may also be generated by a combination of both the superheat section 62 and the steam heat exchanger 94. In embodiments, the steam may then be used to vaporize ammonia in the vaporizer 18, as discussed previously. In embodiments, in this flow scheme, more heat may be obtained in the convection section 28 for preheating the vaporized ammonia stream 24 into a heated ammonia vapor stream 32. In embodiments, in this flow scheme, the feed / effluent exchanger 26 may be omitted. In an embodiment, the feed / effluent exchanger 26 may be replaced by a vapor heat exchanger 94 .

[0115] In an embodiment, the additional available heat may be used to provide heat to the ammonia distillation unit 46 in stage (I). In an embodiment, the additional available heat may be recovered in the convection portion 28 of the ammonia dissociation furnace 30 by including an ammonia distillation reboiler section 88 (also identified as stage S). In an embodiment, the ammonia distillation reboiler section 88 may be configured to provide heat to the ammonia distillation unit 46 as previously described. In an embodiment, the ammonia distillation reboiler section 88 may include one or more coils for recovering heat by circulating gas from the ammonia distillation unit 46 through the one or more coils for ammonia distillation regeneration (step I) in the ammonia distillation unit 46.

[0116] In embodiments, an isothermal process may be used instead of an adiabatic process, in which the ammonia dissociation reaction occurs with the support of heat input with little or no temperature change. In embodiments, ammonia from a vaporized ammonia stream may be dissociated under isothermal conditions while recovering heat from the dissociated hydrogen / nitrogen stream. Figure 3 The diagram illustrates an embodiment of a system 10". In the embodiment, the system 10" is similar to Figure 1 System 10 and Figure 2 The system 10 ′ has a modification involving the first reactor. In an embodiment, the modification involves the adiabatic reactor 34.

[0117] As explained above, the cracking of ammonia into hydrogen and nitrogen is an endothermic process based on equilibrium. In embodiments, reaction (Z) may be favored at high temperatures. In embodiments, also as discussed above, the outlet temperature of the tubes 80 of the radiant portion 40 of the ammonia dissociation furnace 30 may have a high temperature, which may range from about 500° C. to about 750° C., such as from about 550° C. to about 700° C. In embodiments, this heat may be used for isothermal ammonia dissociation or cracking reactions.

[0118] In an embodiment, the isothermal ammonia dissociation or cracking of ammonia contained in the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 may be performed in the isothermal unit 90 as a first reactor. In an embodiment, the isothermal unit 90 may include a reactor-cum-heat exchanger. In an embodiment, the reactor-cum-heat exchanger may include a catalyst bed with one or more catalysts for ammonia dissociation. In an embodiment, in the isothermal unit 90, the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 may be exposed to and / or contacted with one or more catalysts. In an embodiment, one or more catalysts as previously described with respect to the adiabatic reactor 34 may be used in the isothermal unit 90.

[0119] In an embodiment, not all of the ammonia from the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32 is dissociated in the isothermal unit 90. In an embodiment, similar to the adiabatic reactor 34, the isothermal unit 90 is preferably arranged in sequence before the second reactor, i.e., the radiation section 40, such as Figure 3 In an embodiment, as schematically illustrated, the first reactor effluent 36' of the isothermal unit 90 may be fed to the radiant section 40 for the second stage dissociation, as illustrated. In an embodiment, as previously described, the first reactor effluent 36' may be heated in the first reactor effluent heating section 38 of the convection section 28. In an embodiment, to convert at least a portion of the ammonia remaining in the first reactor effluent 36' from the vaporized ammonia stream 24 and / or the heated ammonia vapor stream 32, the method and system may include the use of a second reactor, such as described herein with respect to the radiant section 40 of the ammonia dissociation furnace 30.

[0120] In an embodiment, the inlet conditions of the isothermal unit 90 may be about 20 bar to about 50 bar. In an embodiment, the inlet pressure may be in any sub-range of 20 bar to 20 bar. In an embodiment, the inlet conditions of the isothermal unit 90 may have a temperature range of about 300°C to about 600°C. In an embodiment, the inlet temperature may be in any sub-range of 300°C to 600°C. In an embodiment, the outlet temperature of the isothermal unit 90 may have a temperature range of about 300°C to about 600°C. In an embodiment, the outlet temperature may be in any sub-range of 300°C to 600°C. In an embodiment, the inlet temperature may be 300°C and the outlet temperature may be 600°C. In an embodiment, the inlet temperature may be 500°C and the outlet temperature may be 500°C.

[0121] In an embodiment, the temperature of the ammonia feed to the isothermal unit 90 can be kept nearly constant across the catalyst bed, since heat can be continuously provided by the other side of the reactor-exchanger. In an embodiment, the heat can be provided by the dissociated hydrogen / nitrogen stream 20 exiting the radiant section 40 of the ammonia dissociation furnace 30.

[0122] In an embodiment, by implementing an isothermal method, the utilization of the heat of ammonia cracking can be improved and / or the method of utilizing the heat of ammonia cracking can be simplified. In an embodiment, the implementation of the isothermal method as described can improve the utilization of high-level heat (i.e., high temperature and high flux heat), for example, the utilization of heat generated by the fuel from the ammonia dissociation furnace 30. In an embodiment, the isothermal method can increase the conversion rate of ammonia to hydrogen compared to the adiabatic method described above. In an embodiment, due to the constant high temperature, which does not decrease across the catalyst bed as in an adiabatic reactor, the formation of hydrogen in the isothermal unit-exchanger can achieve a higher conversion rate. In an embodiment, the isothermal method can have a lower but constant operating temperature than the adiabatic method, thereby potentially reducing operating costs and improving equipment reliability.

[0123] In an embodiment, the systems and methods described herein may provide one or more advantages. In an embodiment, the system and method may provide a method for extracting hydrogen from ammonia. In an embodiment, the system and method may provide a simplified and / or low-cost flowsheet design. In an embodiment, the system and method may provide high product yield and high overall energy efficiency. In an embodiment, the system and method may utilize mature method system and equipment design. In an embodiment, compared with the prior art that is often limited to a relatively small scale (≤5 metric tons / day), the system and method described herein may be large-scale (≥300-8500MTPD ammonia production). In an embodiment, the system and method may be self-sufficient in terms of energy for ammonia dissociation. In an embodiment, the system and method may be powered by electricity and / or fuel. In an embodiment, the system and method may be at least partially self-sufficient in terms of energy for ammonia dissociation. In an embodiment, the operating pressure may be higher and the operating temperature may be lower than the prior art. In an embodiment, better utilization of high-level heat in the method and system may lead to higher energy efficiency compared to the prior art.

[0124] In the foregoing description, the present invention has been described with reference to its embodiments. However, this description should be regarded as illustrative rather than restrictive. For example, equipment, reactors, exchangers, furnaces, parts, process streams, methods, reactants, catalysts, products and operating conditions that fall within the claimed or disclosed parameters but are not specifically indicated or attempted in the specific examples are also expected to be within the scope of the present invention.

[0125] The present invention can be implemented in the absence of undisclosed elements. In addition, the present invention can suitably include, consist of, or consist essentially of the disclosed elements. For example, a method for dissociating ammonia into hydrogen and nitrogen can be provided, wherein the method includes, consists essentially of, or consists of feeding ammonia vapor to a reactor sequence, wherein the reactor sequence is selected from adiabatic dissociation in a reactor containing a catalyst, dissociation in a radiant tube reactor including radiant tubes containing a catalyst, and a combination of both, and the method further includes, consists essentially of, or consists of producing a hydrogen product stream.

[0126] A system for dissociating ammonia into hydrogen and nitrogen may further be provided, wherein the system comprises, consists essentially of, or consists of: a preheater receiving liquid ammonia and configured to heat the liquid ammonia to produce a heated ammonia stream, a vaporizer receiving the heated ammonia stream and configured to vaporize the ammonia, a feed / effluent exchanger receiving the vaporized ammonia and configured to heat the vaporized ammonia, a reactor receiving the heated, vaporized ammonia, wherein the reactor is selected from an adiabatic dissociation reactor comprising a catalyst, a dissociation reactor comprising radiant tubes comprising a catalyst, and combinations thereof, wherein the system further comprises, consists essentially of, or consists of a hydrogen product stream extracted from the reactor.

Claims

1. A method for dissociating ammonia into hydrogen and nitrogen, comprising: preheating a liquid ammonia feed in a first preheater to produce a preheated liquid ammonia stream while recovering heat from a dissociated hydrogen / nitrogen stream; vaporizing a preheated liquid ammonia feed to produce a vaporized ammonia stream; dissociating at least a portion of the vaporized ammonia stream to produce a dissociated hydrogen / nitrogen stream by: feeding a vaporized ammonia stream to a first reactor to produce a reactor effluent; as well as feeding the reactor effluent to a radiant tube reactor provided in an ammonia dissociation furnace; and feeding a low carbon fuel of tail gas from a pressure swing adsorption, an unpurified mixture product from an ammonia scrubber, a vaporized ammonia stream, or a combination thereof to the ammonia dissociation furnace.

2. The method of claim 1, wherein: Dissociating the vaporized ammonia stream further includes contacting the vaporized ammonia stream with one or more catalysts, the one or more catalysts comprising a nickel-based catalyst, a ruthenium-based catalyst, or a combination thereof.

3. The method of claim 1, wherein: Feeding the vaporized ammonia stream to the first reactor also includes feeding the vaporized ammonia stream to an adiabatic reactor or an isothermal unit.

4. The method of claim 1, wherein: Feeding the vaporized ammonia stream to the first reactor further comprises feeding the vaporized ammonia stream to an isothermal unit configured to recover heat from the dissociated hydrogen / nitrogen stream.

5. The method of claim 1 further comprising recovering heat from the convection section of the ammonia dissociation furnace to heat the boiler feed water stream.

6. The method of claim 8 further comprising generating steam by recovering heat from a convection portion of the ammonia dissociation furnace.

7. The method of claim 6, further comprising using the steam to supply heat for vaporization of a preheated liquid ammonia feed.

8. The method of claim 1 further comprising recovering heat from a convection portion of the ammonia dissociator furnace to heat an ammonia distillation unit downstream of the ammonia dissociator furnace.

9. The method of claim 1 further comprising providing heat to the ammonia dissociation furnace by burning a fuel.

10. The method of claim 9 further comprising preheating at least a portion of the fuel via one or more coils located in a convection section of the ammonia dissociation furnace.

11. The method of claim 1 further comprising feeding the gas turbine exhaust gas to the ammonia dissociator furnace to supply combustion air to one or more burners of the ammonia dissociator furnace.

12. The method of claim 1, wherein: Vaporizing the preheated liquid ammonia feed includes recovering heat from the dissociated hydrogen / nitrogen stream prior to recovering heat from the dissociated hydrogen / nitrogen stream in a preheater.

13. The method of claim 1 further comprising feeding the dissociated hydrogen / nitrogen stream to a purification process after the preheater has recovered heat from the dissociated hydrogen / nitrogen stream to produce a hydrogen product stream having a hydrogen concentration in the range of 75 mol % to about 99.99999 mol %.

14. A system for dissociating ammonia into hydrogen and nitrogen, comprising: an ammonia dissociation furnace including a convection section and a radiant section; a preheater heat exchanger arranged to receive a liquid ammonia feed and a dissociated hydrogen / nitrogen stream, the preheater heat exchanger being configured to transfer heat from the dissociated hydrogen / nitrogen stream to the liquid ammonia feed and produce a preheated ammonia stream; a vaporizer located downstream of the preheater and configured to vaporize the preheated ammonia stream to produce a vaporized ammonia stream; a first reactor configured to receive a vaporized ammonia stream, the first reactor comprising an adiabatic reactor or an isothermal unit; a radiant tube reactor located within the radiant section, downstream of the first reactor, and configured to receive a reactor effluent from the first reactor and output a dissociated hydrogen / nitrogen stream; as well as A low carbon fuel is fed to the ammonia dissociator from a pressure swing adsorption, an ammonia scrubber, a vaporizer, or a combination thereof.

15. The system of claim 14, wherein the first reactor comprises: an adiabatic reactor comprising an inlet condition temperature ranging from about 500°C to about 750°C and an outlet condition temperature ranging from about 300°C to about 550°C; or An isothermal unit comprising an inlet condition temperature ranging from about 300°C to about 600°C and an outlet condition temperature ranging from about 300°C to about 600°C.

16. The system of claim 14, wherein the first reactor comprises: A steam generation section includes one or more coils in a convection section of the ammonia dissociation furnace, the one or more coils being configured to recover heat from the ammonia dissociation furnace.

17. A system for dissociating ammonia into hydrogen and nitrogen, comprising: an ammonia dissociation furnace comprising a convection section and a radiant reactor section; an ammonia distillation reboiler section located in the convection section of the ammonia dissociator furnace, the ammonia distillation reboiler section being thermally coupled to the ammonia distillation unit and comprising one or more coils configured to recover heat from the convection section of the ammonia dissociator furnace; an adiabatic reactor comprising one or more catalysts for dissociating ammonia and a reactor effluent; One or more radiant tubes, located in the radiant reactor portion of the ammonia dissociation furnace, are configured to receive the reactor effluent from the adiabatic reactor and output a dissociated hydrogen / nitrogen stream.

18. The system of claim 17, further comprising a heat exchanger functionally connected to the steam drum and arranged to generate steam by recovering heat from the dissociated hydrogen / nitrogen stream.

19. The system of claim 17, further comprising gas turbine exhaust gas fed to one or more burners located in the ammonia dissociation furnace.

20. The system of claim 17, further comprising an ammonia scrubber coupled to the ammonia distillation reboiler section, the ammonia scrubber being arranged to receive the dissociated hydrogen / nitrogen stream and configured to remove unreacted ammonia from the dissociated hydrogen / nitrogen stream with scrubbing water to produce a hydrogen-nitrogen gas mixture and an ammonia aqueous solution, wherein The aqueous ammonia solution is directed to an ammonia distillation unit for recovering unreacted ammonia and wash water.

21. A system for dissociating ammonia into hydrogen and nitrogen, comprising: an isothermal unit configured to receive the vaporized ammonia stream and recover heat from the dissociated hydrogen / nitrogen stream; as well as A radiant tube reactor is located downstream of the isothermal unit and is configured to receive the reactor effluent from the isothermal unit and output a dissociated hydrogen / nitrogen stream.

22. The system of claim 21, wherein: The isothermal unit comprises a reactor-cum-heat exchanger having an inlet condition temperature ranging from about 300°C to about 600°C and an outlet condition temperature ranging from about 300°C to about 600°C.

23. The system of claim 21, wherein: The radiant tube reactor includes one or more radiant tubes located in a radiant reactor portion of an ammonia dissociation furnace including a convection portion.

24. The system of any one of claims 14, 17 or 21, further comprising an ammonia scrubber for receiving the dissociated hydrogen / nitrogen stream, the ammonia scrubber being configured to remove unreacted ammonia from the dissociated hydrogen / nitrogen stream with scrubbing water to produce a hydrogen-nitrogen gas mixture.

25. The system of claim 24, further comprising a pressure swing adsorption unit configured to receive the hydrogen-nitrogen gas mixture from the ammonia scrubber, the pressure swing adsorption unit configured to purify the hydrogen-nitrogen gas mixture to obtain a hydrogen product stream comprising a hydrogen concentration ranging from 75 mol % to 99.99999 mol %.

26. The system of claim 25, wherein: The pressure swing adsorption unit includes a flue gas effluent that is directed to an ammonia dissociator furnace for use as fuel.

27. A method for dissociating ammonia into hydrogen and nitrogen, comprising: feeding a vaporized ammonia stream to an adiabatic reactor containing one or more catalysts for dissociating ammonia; feeding an effluent reactor stream from the adiabatic reactor to one or more radiant tubes located in a radiant reactor section of an ammonia dissociation furnace to produce a dissociated hydrogen / nitrogen stream, wherein the ammonia dissociation furnace includes a convection section; and Heat from the convection section of the ammonia dissociation furnace is transferred to the ammonia distillation unit.

28. The method of claim 27, further comprising generating steam by recovering heat from the dissociated hydrogen / nitrogen stream.

29. The method of claim 27, further comprising: feeding the dissociated hydrogen / nitrogen stream to an ammonia scrubber configured to remove unreacted ammonia from the dissociated hydrogen / nitrogen stream with scrubbing water to produce a hydrogen-nitrogen gas mixture and an aqueous ammonia solution; and The aqueous ammonia solution is fed to an ammonia distillation unit for recovering unreacted ammonia and wash water.

30. A method for dissociating ammonia into hydrogen and nitrogen, comprising: isothermally dissociating ammonia from a vaporized ammonia stream to produce a reactor effluent while recovering heat from a dissociated hydrogen / nitrogen stream; as well as The reactor effluent is fed to a radiant tube reactor to dissociate ammonia present in the reactor effluent to output a dissociated hydrogen / nitrogen stream.

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