Apparatus and process for ammonia cracking catalyst activation

Abstract

To provide an apparatus and process for ammonia cracking catalyst activation.SOLUTION: An apparatus and process for the activation of catalyst material utilized in ammonia cracking can include an initial use of hydrogen and heat to perform an initial stage of catalyst activation and a subsequent use of ammonia and heat to perform a subsequent state of catalyst activation. The subsequent use of ammonia can be configured so that different catalytic material at different plant elements are activated in a pre-selected sequence to provide activation of the catalytic material utilized in different plant elements. Some embodiments can be configured to avoid excess temperatures that can be detrimental to equipment that can be positioned upstream of a furnace in some embodiments while also avoiding sintering of the catalytic material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - reference to related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 596,320, filed on November 6, 2023.

[0002] The present invention relates to a process and apparatus for the activation of catalyst materials utilized in ammonia decomposition plants and processes.

Background Art

[0003] Ammonia can be decomposed to produce hydrogen. Examples of processes that can be used to decompose ammonia can be understood from U.S. Patent Application Publication No. 2023 / 0242395 and International Publication Nos. 2022 / 265647, 2022 / 265648, 2022 / 265649, 2022 / 265650, 2022 / 265651, and co - pending U.S. Patent Applications Nos. 17 / 990,832, 17 / 990,823, 17 / 990,817, and 17 / 990,815.

Summary of the Invention

[0004] The ammonia decomposition process can involve the use of a catalyst material that aids in facilitating the decomposition of ammonia into hydrogen gas and nitrogen gas. The activation of the catalyst can depend on the formulation of the catalyst. Activation typically starts at a somewhat low temperature and increases towards a higher final temperature. The final temperature generally depends on the active metal species on the catalyst. For example, ruthenium (Ru) catalysts typically use a lower final activation temperature (e.g., less than 350°C), while nickel (Ni) catalysts often require a higher final activation temperature (e.g., greater than 350°C). Ru catalysts can also have more stringent requirements regarding the temperature increase and holding time for catalyst activation compared to Ni catalysts.

[0005] Andrew, S. P. (1981), Theory and practice of the formulation of heterogeneous catalysts. Chemical Engineering Science, 36(9), 1431 - 1445 discloses that the activation of catalyst materials can involve exposing the catalyst materials to a combination of a higher temperature environment (e.g., application of heat) and exposure to a reducing agent. Twigg, M. V. (1996). Catalyst Handbook (2nd ed.). London: Manson Publishing Ltd. (“Twigg”) discloses that hydrogen is a commonly used reducing agent. Twigg also discloses that the catalyst activation process is carried out to reduce the precursor metal oxide of the supported metal catalyst to microcrystals of the metal catalyst so that the catalyst can be activated and can provide a reduction in activation energy or a change in the reaction mechanism that can help promote chemical reactions.

[0006] It was specified that the catalyst used for ammonia decomposition can be shipped in an oxidized state, a semi - oxidized state, or at least a partially passivated state that may require activation before use for ammonia decomposition. As described above, the activation of catalyst materials involves a process in which the catalyst materials are exposed to a reducing environment such as a hydrogen - containing gas and heat for activating the catalyst materials (e.g., removing oxides, removing the oxide layer surrounding or covering the internal catalyst metal material, removing the passivation layer surrounding or covering the internal catalyst metal material, etc.). Conventionally, activation would be carried out using hydrogen mixed with an inert gas such as nitrogen (e.g., see Twigg, M. V. (1996). Catalyst Handbook (2nd ed.). London: Manson Publishing Ltd.).

[0007] However, we have the activation of catalyst materials that can be positioned in a furnace used for ammonia decomposition (e.g., hydrogen (H 2 ) and nitrogen (N 2) is positioned in a tube of a furnace through which ammonia can pass to be heated and decomposed in the furnace, and it has been identified that very high temperatures (e.g., temperatures above 500 °C or above 600 °C (e.g., 450 °C - 700 °C, 550 °C - 675 °C, 500 °C - 700 °C, etc.)) may be required. We have determined that due to such high temperatures in the furnace during a long catalyst activation process, some types of front-end heat exchangers disclosed in U.S. Patent Application Nos. 17 / 990,823, 17 / 990,817, and 17 / 990,815 may exceed the design temperature of these heat exchangers unless they are made of special materials that can withstand very high temperatures due to how the reducing agent and heat can recycle through the reactor and furnace for the activation of the catalyst material. However, using such special equipment can be detrimental to the procurement of such equipment and also result in increased costs, delays in production or installation, and increased special maintenance operations and / or maintenance costs.

[0008] For example, the use of more specialized equipment may increase safety risks due to an increase in the rating of dissimilar metals or equipment that may introduce an increase in items requiring maintenance supervision and maintenance monitoring. Avoiding or minimizing the use of these devices can help avoid this increase in safety risk and these additional maintenance activities utilized to account for that increased risk.

[0009] We have identified that such a high-temperature profile for catalyst activation within an ammonia decomposition apparatus configured to implement an ammonia decomposition process can be avoided such that lower-temperature rated front-end equipment can be utilized. We have identified that such a feature can serve to provide improved catalyst material activation while providing improved operating efficiency and flexibility. We believe that embodiments can also help to make ammonia decomposition more economically attractive through the use of more environmentally considered ammonia products (e.g., ammonia produced via a renewable energy source and / or produced in conjunction with the use of carbon dioxide capture technology), thereby also enabling an increase in environmentally considered ammonia production and ammonia decomposition for hydrogen generation.

[0010] In some embodiments, the process and apparatus for catalyst activation of an ammonia decomposition apparatus can include utilizing hydrogen as a reactant and heat via a furnace to effect an initial first low-temperature phase of catalyst activation over a first catalyst activation period. This initial first low-temperature activation can include periodically increasing the temperature and / or hydrogen concentration until the first catalyst activation phase is satisfied in some implementations. After it is detected that the first initial catalyst activation phase has occurred, a second high-temperature catalyst activation phase can be effected over a second catalyst activation period. This second phase can include the use of ammonia as a reagent and the use of a higher second temperature profile. This second phase can be combined with purging of the hydrogen reactant fluid before or during the use of ammonia as a reactant for the second high-temperature catalyst activation phase and / or after such purging to remove the hydrogen reactant fluid. In some embodiments, since the second phase, the high-temperature catalyst activation phase, can occur continuously after the first phase, the second phase is initiated such that it occurs immediately after the completion of the first initial low-temperature phase (e.g., the second high-temperature phase can be initiated such that it occurs immediately after it is detected that the first phase has been completed via detection of a specific temperature and / or hydrogen content associated with the completion of the process of the initial low-temperature first catalyst activation phase).

[0011] In some embodiments, the process is implemented to help control the temperature within the units of the ammonia decomposition process such that the furnace experiences the highest temperature and the upstream reactor upstream of the furnace and the heat exchanger upstream of the furnace experience lower temperatures within a preselected temperature profile, helping to avoid exposing the equipment to higher temperatures than what the equipment is being evaluated for experiencing (e.g., the temperature may not exceed 350°C, may be between 300°C and 400°C, may not exceed 550°C, etc.). For example, some heat exchangers can have different temperature ratings, and the temperature control provided by the catalyst activation process of the embodiment and the apparatus configured to utilize such a process can be configured such that different heat exchanger equipment is maintained within the temperature ratings of these heat exchanger equipment. Such temperature ratings can vary from 200°C to 690°C for different heat exchangers in some embodiments (e.g., one or more preheat heat exchangers can have a temperature rating in the range of 200°C to 325°C, while one or more other heat exchangers have a temperature rating in the range of 325°C to 690°C).

[0012] In some implementations, the provided catalyst activation can result in the catalyst material in the upstream portion of the furnace being activated first, and then the catalyst material of the second reactor being activated second, even though this second reactor is between the first reactor and the furnace. The provided catalyst activation can then also result in the activation of the catalyst material of the first reactor, before the catalyst material in the downstream portion of the furnace is finally activated. This type of staged activation helps to provide a well-timed catalyst activation process that can also help avoid sintering of the catalyst material, while also helping to avoid high temperature profiles in the upstream reactor and upstream heat exchanger.

[0013] We have surprisingly found that the use of ammonia as a reactant in the second high-temperature phase of catalyst activation can help keep the front-end heat exchanger within a lower standard design temperature. The ammonia used in the second high-temperature phase of catalyst activation can be blended with nitrogen or used pure in some embodiments. It is contemplated that nitrogen (N2) can be injected to mix with ammonia to provide a preselected flow rate of the second reactant and a desired flow rate to obtain a preselected concentration of ammonia in the second reactant as the second reactant passes through tubes containing the pre-reactor and catalyst material of the furnace.

[0014] We have also found that the use of ammonia (NH 3 ) during catalyst activation can also reduce the demand for other cooling media / equipment during catalyst activation (such as load savings of cooling water towers or air coolers), and can provide a cooling source for the entire system during catalyst activation (such as the sensible heat, latent heat, endothermic reaction, etc. of ammonia decomposition to form nitrogen and hydrogen during catalyst activation with ammonia as a reactant).

[0015] In some embodiments, the ammonia feed rate used during catalyst activation can be made significantly lower than the design rate used for ammonia decomposition to produce hydrogen after the catalyst material has been activated. Also, more conversion can be carried out across the upstream reactor during catalyst activation. Since most of the ammonia can be utilized in the second catalyst activation phase such that the ammonia is converted in the upstream pre-reactor during use of the high-temperature second catalyst activation phase, the temperature in the furnace downstream of those reactors can rapidly rise to the desired activation temperature because the endotherm from the ammonia decomposition reaction that consumes the heat generated by the furnace burner during the catalyst activation process is low or significantly low (or in some cases there is no endotherm). We have surprisingly found that this effect can result in an improved catalyst activation that can also be carried out more rapidly (for example, since the downtime associated with catalyst activation for the ammonia decomposition process can be reduced, the activation process can be carried out much faster, enabling the catalyst activation to be carried out more flexibly, efficiently, and rapidly).

[0016] We have also found that embodiments can enable the use of some catalyst materials having a significantly high final activation temperature in conjunction with other catalyst materials having a lower final activation temperature. For example, in some embodiments, a catalyst material having an activation temperature above 600 °C (such as 650 °C, 600 °C - 700 °C, etc.) can be utilized in conjunction with other catalyst materials having a full activation temperature of 400 °C or less, 350 °C or less, or 300 °C - 400 °C.

[0017] In a first aspect, the process for catalyst activation for ammonia decomposition can include feeding a first reactant containing hydrogen to at least one pre-reactor positioned upstream of a furnace having at least one tube within a radiant section of the furnace such that the first reactant passes through a catalyst material of at least one pre-reactor and then through a catalyst material of at least one tube within the radiant section of the furnace. In response to detecting a first level of catalyst activation, the feeding of the first reactant can be stopped, and feeding of a second reactant containing ammonia to at least one pre-reactor and to at least one tube within the radiant section of the furnace can be initiated, whereby the second reactant passes through a catalyst material of at least one pre-reactor and then through at least one tube within the radiant section of the furnace to fully activate the catalyst material of at least one tube.

[0018] In some embodiments, the concentration of hydrogen in the first reactant can be controlled to be within a preselected concentration range. For example, the first reactant can include a mixture of nitrogen and hydrogen, and the hydrogen concentration can be in the range of 10 mole percent (mol%) and 20 mol%, or in the range of greater than 0 mol% and less than or equal to 25 mol%. The hydrogen concentration can be adjusted during the first catalyst activation phase such that the hydrogen concentration is adjusted over time within a preselected suitable concentration range.

[0019] Also, the concentration of ammonia in the second reactant can be controlled to be within a preselected concentration range. For example, the second reactant can include a mixture of nitrogen and ammonia, and the ammonia concentration can be in the range of 10 mole percent (mol%) and 20 mol%, or in the range of greater than 0 mol% and less than or equal to 25 mol%. The ammonia concentration can be adjusted during the second catalyst activation phase such that the ammonia concentration is adjusted over time within a preselected suitable concentration range. Also, since ammonia is utilized in the second catalyst activation phase, hydrogen and nitrogen can be formed during the activation process and can be present along with the ammonia and nitrogen of the second reactant.

[0020] In some embodiments, the first level of catalyst activation can be determined based on a preselected set of criteria. The criteria can include a temperature profile and / or a concentration profile of hydrogen. The criteria may also (or alternatively) include a preselected period.

[0021] In a second aspect, the feed of the first reactant and the feed of the second reactant are such that the catalyst material in the upstream portion of at least one tube is fully activated, then the catalyst material in at least one pre-reactor is fully activated, then the catalyst material in at least one pre-reactor is fully activated, and after the catalyst material in the upstream portion of at least one tube is fully activated, the catalyst material in the downstream portion of at least one tube can be fully activated. In other embodiments, the process can be implemented such that an alternative sequence of activation of different catalyst materials can be performed.

[0022] In a third aspect, the feed of the second reactant containing ammonia can be such that the catalyst material in the downstream portion of at least one tube is finally fully activated. For example, the catalyst material in the downstream portion of at least one tube can contain iron (Fe) and / or nickel (Ni), and can be finally activated after one or more of the upstream catalyst material layers in the tubes of the furnace and the pre-reactor containing ruthenium (Ru) are activated.

[0023] In a fourth aspect, the process can include mixing nitrogen with the ammonia of the second reactant such that the second reactant has ammonia at a preselected ammonia concentration and / or the second reactant has a preselected flow rate.

[0024] In a fifth aspect, the process can include mixing nitrogen with the hydrogen of the first reactant such that the first reactant has hydrogen at a preselected hydrogen concentration and / or the first reactant has a preselected flow rate.

[0025] In a sixth aspect, at least one pre-reactor can include a plurality of pre-reactors including a first pre-reactor and a second pre-reactor. The first pre-reactor can have a catalyst material within a vessel of the first pre-reactor, and the second pre-reactor can have a catalyst material within a vessel of the second pre-reactor. The second pre-reactor can be downstream of the first pre-reactor such that the second pre-reactor is between at least one tube of the furnace and the first pre-reactor.

[0026] The feeding of the first reactant can be performed as follows: (a) the catalyst material in the upstream portion of at least one tube is fully activated, (b) the catalyst material of the second pre-reactor is fully activated, and (c) the catalyst material of the first pre-reactor is fully activated. The feeding of the second reactant can be performed such that (d) the catalyst material in the downstream portion of at least one tube is fully activated. In some embodiments, the catalyst material in the downstream portion of at least one tube can have a higher activation temperature than the catalyst material in the upstream portion of at least one tube. The catalyst material in the downstream portion of at least one tube can also, in some embodiments, have a higher activation temperature than the catalyst material of the first pre-reactor. The catalyst material in the downstream portion of at least one tube can have a higher activation temperature than at least a portion of the catalyst material of the second pre-reactor.

[0027] In a seventh aspect, the feeding of the first reactant can also include recirculating the first reactant through at least one tube and at least one pre-reactor over a first period. The first period can be, for example, the first period of a first catalyst activation phase. This first period can be a preselected period defined by a set of preselected design criteria.

[0028] In an eighth aspect, the process can also include, in response to detecting a first level of catalyst activation, venting a first reactant while simultaneously beginning to feed a second reactant toward at least one pre-reactor and at least one tube. The venting can also be provided such that a second reactant output from at least one tube during the process of the second catalyst activation phase is also vented (e.g., not recycled).

[0029] In a ninth aspect, the process of the first aspect can further include one or more features of the second, third, fourth, fifth, sixth, seventh, and / or eighth aspects to provide further embodiments. Also, in embodiments of the process, other features can be utilized. Examples of such other features are considered in connection with the exemplary embodiments of the process provided herein.

[0030] In a tenth aspect, an apparatus for ammonia decomposition configured to facilitate catalyst activation is provided. Embodiments of the apparatus can be configured to utilize embodiments of a process for catalyst activation for ammonia decomposition. The apparatus can include a furnace having at least one tube containing a catalyst material within at least one tube for ammonia decomposition. The catalyst material within the at least one tube can have an upstream portion of the catalyst material and a downstream portion of the catalyst material. At least one pre-reactor can be positioned upstream of the at least one tube. The at least one tube can be in fluid communication with the at least one pre-reactor. The apparatus can be sized and configured such that a first reactant can be fed to the at least one pre-reactor and the at least one tube such that the first reactant passes through the catalyst material of the at least one pre-reactor and then through the catalyst material of the at least one tube. Also, the apparatus can be sized and configured such that a second reactant can be fed to the at least one pre-reactor and the at least one tube such that, in response to detecting a first level of catalyst activation, the first reactant can be exhausted and the second reactant can pass through the catalyst material of the at least one pre-reactor and then through the at least one tube such that the second reactant completely activates at least a portion of the catalyst material of the at least one tube.

[0031] Embodiments of the apparatus can also include other elements and features. For example, embodiments can include a plurality of heat exchangers positioned upstream of the pre-reactor and / or one or more heat exchangers positioned between the pre-reactor and at least one tube of the furnace. As another example, embodiments can utilize pumps and / or compressors to facilitate the flow of fluids.

[0032] In the eleventh aspect, the apparatus can be configured such that the feeding of the first reactant is carried out so that the upstream portion of the catalyst material in at least one tube is first fully activated and then the catalyst material in at least one pre-reactor is fully activated. The second reactant can also be fed to at least one tube and at least one pre-reactor such that the downstream portion of the catalyst material in at least one tube is fully activated after the catalyst material in at least one pre-reactor is fully activated and after the upstream portion of the catalyst material in at least one tube is fully activated. For example, in some embodiments, the apparatus can be configured such that the feeding of the second reactant is carried out so that the downstream portion of the catalyst material in at least one tube is fully activated last.

[0033] In the twelfth aspect, at least one pre-reactor of the apparatus can include a plurality of pre-reactors. The plurality of pre-reactors can include a first pre-reactor having a catalyst material in a container of the first pre-reactor and a second pre-reactor having a catalyst material in a container of the second pre-reactor. The second pre-reactor can be downstream of the first pre-reactor such that the second pre-reactor is between at least one tube of the furnace and the first pre-reactor. The apparatus can be configured such that the feeding of the first reactant is carried out so that (a) the upstream portion of the catalyst material in at least one tube is fully activated, (b) the catalyst material in the second pre-reactor is fully activated, and (c) the catalyst material in the first pre-reactor is fully activated. The feeding of the second reactant can be carried out such that (d) the catalyst material in the downstream portion of the catalyst material in at least one tube is fully activated. The downstream portion of the catalyst material in at least one tube can have an activation temperature higher than that of the catalyst material in the upstream portion of the catalyst material in at least one tube. The downstream portion of the catalyst material in at least one tube can also have an activation temperature higher than that of the catalyst material in the first pre-reactor, and the catalyst material in the downstream portion of at least one tube can also have an activation temperature higher than that of at least a part of the catalyst material in the second pre-reactor.

[0034] In a 13th aspect, the apparatus can include a reactant recirculation conduit arrangement positioned such that a first reactant is recirculatable from an outlet of at least one tube to at least one pre-reactor. In some embodiments, the reactant recirculation conduit can be positioned and configured such that a compressor can receive a portion of the first reactant output from at least one tube and compress it to recirculate the first reactant back to at least one of the pre-reactor and a tube of the furnace.

[0035] In a 14th aspect, an apparatus for ammonia decomposition configured to facilitate catalyst activation can include a furnace having at least one tube, the furnace including a catalyst material within at least one tube for decomposition of ammonia, the catalyst material within at least one tube having a more active portion of the catalyst material that is more active than a less active portion of the catalyst material. At least one pre-reactor can be positioned upstream of at least one tube, and at least one tube can be in fluid communication with at least one pre-reactor. The apparatus can be sized and configured such that a first reactant is feedable to at least one pre-reactor and at least one tube such that the first reactant passes through the catalyst material of at least one pre-reactor and then through the catalyst material of at least one tube. A second reactant can be feedable to at least one pre-reactor and at least one tube such that, in response to detecting a first level of catalyst activation, the first reactant is exhaustible, and the second reactant is such that the second reactant is passable through the catalyst material of at least one pre-reactor and then through at least one tube to fully activate a less active portion of the catalyst material of at least one tube. Embodiments of the apparatus can also include other features (e.g., recirculation conduits, heat exchangers, etc.).

[0036] In a 15th aspect, the apparatus of the 10th aspect or the apparatus of the 14th aspect can further include one or more other features of the 11th aspect, the 12th aspect, and / or the 13th aspect in order to provide further other embodiments. Also, in embodiments of the apparatus, other features can be utilized. Examples of such other features are considered in relation to the exemplary embodiments of the apparatus provided herein.

[0037] In still further other embodiments of the apparatus and process, it is contemplated that only a single reactant containing ammonia (e.g., ammonia, ammonia mixed with nitrogen gas, etc.) can be used for catalyst activation. The ammonia utilized is vaporized, optionally mixed with nitrogen, and then can be liquid ammonia that passes through a pre-reactor and at least one tube having therein a catalyst material positioned within the radiant section of a furnace for activation of the catalyst material. Activation of the catalyst material is carried out over a preselected period according to a preselected activation scheme to provide complete activation of all the catalyst materials within the temperature ratings of the various equipment. While adding additional liquid ammonia to the reactant feed to provide catalyst activation, and while controlling the temperatures of the different pre-reactor / furnace tubes and heat exchangers such that catalyst materials having the highest activation temperature within the furnace tubes are activated last while other catalyst materials are activated before the catalyst materials having the highest activation temperature within the furnace tubes, such activation can be provided via use of at least partial recirculation of the ammonia to provide a sequence of catalyst activation.

[0038] It should be understood that embodiments of the process and apparatus can utilize various conduit arrangements and process control elements. Embodiments can utilize sensors (e.g., pressure sensors, temperature sensors, flow sensors, concentration sensors, etc.), controllers, valves, piping, and other process control elements. Some embodiments can utilize, for example, an automatic process control system and / or a distributed control system (DCS). Various different conduit arrangements and process control systems can be utilized to meet a particular set of design criteria.

[0039] Other details, objects, and advantages of the present apparatus for the activation of a catalyst material used in ammonia decomposition, the process for the activation of a catalyst material used in ammonia decomposition, and methods of making and using them will become apparent as the following description of its specific exemplary embodiments proceeds.

[0040] Exemplary embodiments of our apparatus for the activation of a catalyst material used in ammonia decomposition, the process for the activation of a catalyst material used in ammonia decomposition, and methods of making and using them are shown in the drawings included herein. It should be understood that like reference characters used in the drawings may identify like components.

Brief Description of the Drawings

[0041]

Figure 1

Figure 2

Best Mode for Carrying Out the Invention

[0042] Referring to FIGS. 1-2, an apparatus 1 configured for ammonia decomposition can include several process elements that receive ammonia (NH 3 ) and decompose the ammonia to produce hydrogen gas and nitrogen gas. Then, the hydrogen formed can be separated from the nitrogen to produce a hydrogen stream 40.

[0043] For example, the feeding of liquid ammonia 2 can be maintained in a storage device (e.g., at least one ammonia storage tank) at an ammonia storage temperature (e.g., -32°C, -25°C to -40°C, etc.). The stored ammonia that can be stored as liquid ammonia is removed from the storage device and fed to pump P101, where the ammonia is pressurized at a preselected feed pressure (e.g., 4.6 MPa, 4 MPa to 5 MPa, or other suitable feed pressures within a preselected feed pressure range) to generate a flow 4 of pressurized liquid ammonia. The pressurized feed flow 4 can be fed to a preheating heat exchanger E271 that can preheat the pressurized feed of ammonia to generate a flow 6 of preheated liquid ammonia.

[0044] In some embodiments, the preheating heat exchanger E271 can utilize a heat transfer fluid that can be any suitable type of heat transfer fluid for preheating the liquid ammonia to a preselected preheating temperature (e.g., a temperature of 40°C to 60°C, a temperature of 45°C, etc.). In some embodiments, the heat transfer fluid can be (or can include) glycol (e.g., a fluid having 55 wt% ethylene glycol or propylene glycol). The preheating heat exchanger E271 can alternatively be (or also include) an electric heater that helps ensure that the temperature of the heat transfer fluid fed to the heat exchanger E271 as a heating medium is at a temperature sufficient to preheat the liquid ammonia to the desired temperature.

[0045] The preheated feed flow 6 can be further heated and vaporized through further preheating via other preheating heat exchanges. For example, one or more other preheating heat exchangers such as heat exchangers E312, E311, E310, and E2102 can be utilized.

[0046] For example, the initially preheated ammonia feed stream 6 output from the heat exchanger E271 can be further heated by heat exchange in the heat exchanger E312 to produce a further heated liquid ammonia stream 8. Next, the further heated liquid ammonia in the stream 8 can be evaporated via heat exchange in the heat exchanger E311 to produce a gaseous ammonia, or ammonia vapor stream 10. Next, the ammonia vapor in the stream 10 can be superheated by heat exchange in the heat exchanger E310 to produce a heated ammonia gas stream 12 at a preselected preheated ammonia gas temperature (e.g., a temperature of 260°C, a temperature in the range of 240°C to 280°C, etc.).

[0047] Next, the heated ammonia gas in the stream 12 can be further heated by heat exchange in the heat exchanger E2102 to produce a superheated ammonia gas stream 14 at a preselected superheated ammonia gas temperature (e.g., a temperature of 420°C, a temperature in the range of 400°C to 450°C, etc.).

[0048] In connection with providing such preheating of the ammonia gas, each of the heat exchangers E310, E311, E312, and E2102 can have a preselected temperature rating specified in consideration of the preheating conditions that a particular heat exchanger can be expected to experience during the ammonia decomposition operation and the availability of equipment capable of meeting those conditions. For example, the heat exchanger E312 can have a temperature rating in the range of 100°C to 300°C, the heat exchanger E311 can have a temperature rating in the range of 175°C to 450°C, the heat exchanger E310 can have a temperature rating in the range of 330°C to 570°C, and the heat exchanger E2102 can have a temperature rating in the range of 300°C to 500°C. Other embodiments may utilize other temperature profiles and have other heat exchangers with other suitable temperature ratings.

[0049] In some embodiments, there may be a single heat exchanger E2102 for providing superheated ammonia gas. In other embodiments, the heat exchanger E2102 can output a heated ammonia gas stream for being fed to at least one other feed preheating heat exchanger to generate a stream 14 of superheated ammonia gas. In some implementations, there may also be at least one selective catalytic reactor (SCR) located downstream of the heat exchanger E2102 or within the heat exchanger (e.g., within the heat exchanger E2102) and positioned between the heat exchanger E2102 and the second feed preheating heat exchanger. In some embodiments, the heat transfer fluid that can be utilized as a heating medium for the heat exchanger E2102 and / or other heat exchangers can be the flue gas output from the furnace F201 of the apparatus 1.

[0050] Other embodiments can utilize different arrangements of preheating heat exchangers to generate the stream 14 of superheated ammonia gas. For example, fewer or more heat exchangers can be utilized to provide the formation of superheated ammonia gas. The heat transfer fluid used for such heating can be any suitable heat transfer fluid that can function as a suitable heating medium for heating ammonia to form the stream 14 of superheated ammonia gas.

[0051] The superheated ammonia gas in the stream 14 can be fed to one or more pre-reactors upstream of the furnace F201. The superheated ammonia gas stream feed temperature for feeding to the one or more pre-reactors can be a preselected superheated ammonia gas feed temperature (e.g., a temperature of 420°C, a temperature in the range of 400°C to 500°C, a temperature in the range of 400°C to 450°C, etc.). The superheated ammonia gas stream feed pressure can be a suitable preselected feed pressure that can be less than the pressure at which the pump P101 outputs the stream 4 of pressurized liquid ammonia. For example, the preselected feed pressure of the superheated ammonia fed to the one or more pre-reactors can be 4.3 MPa, in the range of 4 MPa to 4.5 MPa, or other suitable pressures.

[0052] The upstream pre-reactor can include a first adiabatic reactor C141 that can have a catalyst bed within the reactor vessel, or a first pre-reactor C141. The catalyst bed can include a suitable catalyst material. For example, the catalyst material of the catalyst bed of the first adiabatic reactor C141 can be a bed of ruthenium-based catalyst or a bed of nickel-based catalyst. Other embodiments can alternatively use a first pre-reactor C141 that can utilize other catalyst materials or combinations of catalyst materials (e.g., a bed of iron-based catalyst material, a bed of catalyst material having a combination of nickel catalyst material and iron catalyst material, a catalyst material including a combination of an upstream layer of catalyst material and a downstream layer of a different catalyst material, etc.).

[0053] A portion of the ammonia gas can be decomposed as it passes through this catalyst bed of the first pre-reactor C141 to form a first pre-reactor output stream 16 of intermediate gas that includes ammonia gas and some products of partially decomposed ammonia (e.g., nitrogen gas and hydrogen gas). In some embodiments, the mole fraction of ammonia in the gas passing through the first adiabatic reactor vessel C141 can decrease from about 100 mole percent (mol%) ammonia to about 90 mol% ammonia (e.g., about 10% of the ammonia can be decomposed as it passes through the first pre-reactor C141). In other embodiments, the mole fraction of ammonia can vary differently (e.g., it can be 95 mol% - 90 mol% ammonia, or 95 mol% - 80 mol% ammonia, etc.).

[0054] The first pre-reactor output stream 16 of intermediate gas can be output at a preselected temperature. This temperature can be, for example, about 360 °C, 320 °C - 380 °C, or another suitable temperature. This intermediate stream can then be fed to a second pre-reactor C142 that can be, for example, a second adiabatic reactor C142.

[0055] In some embodiments, the first pre-reactor output stream 16 of the intermediate gas can be heated via the heat exchanger E2103 to generate a stream 18 of superheated intermediate gas, and then the stream 18 is fed to a second adiabatic reactor C142 which can also be another type of second pre-reactor. For example, the first pre-reactor output stream 16 of the intermediate gas can be heated to a preselected second pre-reactor feed temperature by passing through the heat exchanger E2103, and then the first pre-reactor output stream 16 is fed to the second adiabatic reactor C142. The second preselected second pre-reactor feed temperature can be, for example, a feed temperature of 590 °C, 450 °C to 610 °C, 550 °C to 620 °C, or other suitable temperatures. The intermediate gas preheating heat exchanger E2103 can utilize a suitable heat transfer fluid to provide the desired preheating (e.g., exhaust gas or flue gas from the furnace F201 or other heating medium).

[0056] The stream 18 of superheated intermediate gas can be fed to a second pre-reactor C142 (e.g., the second adiabatic reactor C142). The second pre-reactor can also include a vessel having a bed containing a catalyst material. The catalyst material of the second pre-reactor C142 can be the same catalyst material as the first pre-reactor or can include a different arrangement of the catalyst material. For example, the second pre-reactor C142 can have a bed of catalyst material including an upstream layer of nickel-based catalyst and a downstream layer of ruthenium-based catalyst. Other embodiments can alternatively utilize different combinations of a single type of catalyst material, or catalyst materials, or beds. For example, in some embodiments, the second pre-reactor C142 can utilize a bed of catalyst material including only an iron-based catalyst, only a ruthenium-based catalyst, or a combination of a downstream nickel-based catalyst and / or iron-based catalyst layer and an upstream ruthenium-based catalyst layer.

[0057] The overheated intermediate gas can be passed through a second pre-reactor for additional pre-decomposition of ammonia in the intermediate gas to produce a furnace feed stream 20 of partially decomposed ammonia gas. The molar fraction of ammonia in the gas output from the second pre-reactor C142 can be a preselected furnace feed concentration. For example, the molar fraction of ammonia in the furnace feed stream 20 can be 0.6 (e.g., 60 mol% ammonia), or can be from 55 mol% ammonia to 75 mol% ammonia.

[0058] When ruthenium-based catalysts are used in both the first pre-reactor C141 and the second pre-reactor C142, the same type of catalyst can be used in both reactors, or different ruthenium-based catalysts can be used. The types of catalyst materials utilized in the first and second pre-reactors can also be adapted to take into account different design criteria or operating objectives. In some embodiments, the catalyst bed of the first pre-reactor C141 can be configured to provide a lower level of ammonia decomposition compared to the catalyst bed of the second pre-reactor C142 located downstream of the first pre-reactor C141 and upstream of the furnace F201.

[0059] In some configurations, at least one of the pre-reactors can utilize a less active catalyst having a lower activity for promoting ammonia decomposition compared to a more highly active catalyst for promoting ammonia decomposition. For example, a ruthenium-based catalyst can be a more highly active catalyst, and a nickel-based catalyst or an iron-based catalyst can be a less active catalyst. The less active catalyst can also have a higher full activation temperature than the more highly active catalyst.

[0060] In other embodiments, there may be only a single pre-reactor (e.g., only pre-reactor C141 or C142). In such embodiments, the operating temperature of the single pre-reactor, the catalyst material utilized in the pre-reactor, and the size of the pre-reactor can be adjusted taking into account its use in providing a feed of partially decomposed ammonia as the furnace feed stream 20 for further decomposition in one or more tubes of furnace F201. In such a configuration, the feed temperature of the superheated ammonia gas stream for feed to the pre-reactor can be higher than a preselected superheated ammonia gas feed temperature that could be selected for use in an arrangement having multiple pre-reactors (e.g., a temperature of 450 °C to 550 °C, a temperature of 475 °C to 600 °C, etc.) for processing the internal ammonia to output the partially decomposed ammonia in the furnace feed stream 20.

[0061] The partially decomposed ammonia in the furnace feed stream 20 can be heated by heat exchange in heat exchanger E305 before being fed as the furnace feed stream 22 preheated to a preselected furnace feed temperature and a preselected furnace feed pressure. The heating medium utilized in heat exchanger E305 can be any suitable fluid (e.g., the hydrogen product gas and / or nitrogen product gas output from furnace F201, or another suitable heat transfer fluid). The preselected furnace feed pressure can be a suitable feed pressure (e.g., a pressure of 3.8 MPa, a pressure of 3 MPa to 4.1 MPa, etc.). The preselected furnace feed temperature can also be a suitable feed temperature (e.g., a temperature of 300 °C to 500 °C, a temperature of 450 °C, a temperature of 500 °C, etc.). In some embodiments, the inlet feed temperature of the preheated furnace feed stream 22 is limited to a preselected furnace feed temperature (e.g., a temperature of 500 °C, a temperature of 400 °C to 500 °C, etc.) to help limit the inner wall temperature of one or more ammonia decomposition tubes through which the preheated furnace feed stream 22 can pass for the ammonia in its stream to undergo decomposition within furnace F201.

[0062] The heat exchanger E305 can also, in some embodiments, have a preselected temperature rating. For example, the heat exchanger E305 can, in some embodiments, have a temperature rating of 500°C to 700°C. The selected temperature rating for the heat exchanger E305 can be specified considering the preheating conditions that this particular heat exchanger is expected to experience during the ammonia decomposition operation and the availability of equipment that can meet those conditions. Other embodiments may utilize other temperature profiles and have other heat exchangers with other suitable temperature ratings.

[0063] The furnace F201 can include a combustion chamber and one or more catalyst-filled tubes that can be positioned in the radiant section 89 of the furnace F201, which can be considered a furnace reactor or a primary ammonia decomposition reactor. The preheated furnace feed stream 22 can pass through one or more catalyst-filled tubes within the radiant section 89 of the furnace F201 and undergo ammonia decomposition within the catalyst-filled tubes. Combustion of at least one fuel in the combustion chamber generates flue gas via combustion of the fuel to heat the preheated furnace feed stream 22 containing ammonia as well as hydrogen and nitrogen (e.g., via preliminary decomposition of ammonia provided by one or more pre-reactors), which can facilitate the decomposition of ammonia passing through one or more catalyst-filled tubes of the furnace F201.

[0064] The catalyst material within the furnace F201 (e.g., the catalyst material within one or more catalyst-filled tubes that can be filled with the catalyst material or be tubes having the catalyst material arranged therein) can be positioned to help increase the amount of ammonia decomposition that can be performed using the heat from the furnace burner in the combustion chamber of the furnace by reducing the load required to heat the partially decomposed stream to the reaction temperature of ammonia decomposition.

[0065] As described above, the furnace F201 can include a combustion chamber that burns at least one fuel to generate flue gas and heat, and promotes ammonia decomposition within the furnace F201. In some configurations, a flow 62 of air or another oxidant (e.g., oxygen-rich air, etc.) can pass through the forced draft fan K212 before being preheated by heat exchange in the oxidant preheater E2141 to produce a preheated oxidant flow 64. The preheated oxidant flow 64 can be mixed with a flow 70 of fuel (e.g., natural gas, hydrogen gas, a mixture of natural gas and hydrogen, etc.) that is fed to a burner (not shown) of the furnace F201 for combustion of the fuel within the combustion chamber of the furnace. Preheating the oxidant can help reduce the fuel required to promote combustion to generate the desired level of heat for ammonia decomposition.

[0066] One or more tubes within the radiant section 89 of the furnace F201 can be filled with at least two types of ammonia decomposition catalysts in a plurality of different layers, and the plurality of different layers can be positioned at the inlet of the furnace F201 and / or at the outlet of the furnace that can output through the decomposed ammonia product and / or at a downstream layer adjacent to this outlet. In some contemplated embodiments, one or more tubes can also include at least one intermediate layer of catalyst material between an upstream layer of catalyst material and a downstream layer of catalyst material. In other embodiments, there can be only an upstream layer and a downstream layer of catalyst material.

[0067] The upstream and downstream catalyst materials in one or more tubes within the radiant section 89 of the furnace F201 can have different activation temperature requirements. For example, the upstream layer can have a lower activation temperature requirement than the layer of downstream catalyst material. In some embodiments, the catalyst material of the upstream layer can also be less active than the downstream layer (e.g., the upstream layer can be a less active portion of the catalyst material of the furnace F201). In other embodiments, the catalyst material of the upstream layer can be more active than the downstream layer (e.g., the upstream layer can be a more active portion of the catalyst material of the furnace F201, which is more active than a less active portion of the catalyst material of the furnace F201).

[0068] For example, a ruthenium-based catalyst can be used in the layer of the first upstream catalyst material in each tube of furnace F201 so that, with a faster reaction rate, the metal temperature can be maintained within a preselected design limit (for example, a design limit of about 660°C, a design limit of 600°C to 700°C, etc.). The layer of the second downstream catalyst material in one or more tubes of furnace F201, which is downstream of the layer of the first catalyst material, can include a lower-cost but less-active nickel-based catalyst or iron-based catalyst (for example, it can be the Ru-based catalyst in the first upstream layer, an example of the less-active part of the more-active part of the catalyst material of the furnace, an example of the less-active part of the catalyst material of furnace F201, etc.).

[0069] In other embodiments, the layer of the first upstream catalyst material and the layer of the second downstream catalyst material in one or more tubes of furnace F201 can utilize other types of catalyst materials. In some configurations, the layer of the upstream catalyst material can have a lower activation temperature than the layer of the downstream catalyst material, and in other configurations, the layer of the upstream catalyst material can have a higher activation temperature than the downstream layer. In still other embodiments, one or more tubes of furnace F201 can have a single type of catalyst material within the tube.

[0070] The furnace F201 can be operated via the combustion of fuel to heat the preheated furnace feed stream 22 fed into one or more tubes to decompose ammonia to produce hydrogen gas and also nitrogen gas. The furnace F201 can output at least one stream 24 of the decomposed gas, and the stream 24 can exit the radiant section 89 of the furnace F201 at a preselected outlet temperature (for example, a temperature of 640 °C, a temperature in the range of 600 °C to 700 °C, a temperature in the range of 620 °C to 750 °C, etc.). The decomposed gas output from the furnace F201 can be fed to the heat exchanger E305 as a heating medium to preheat the furnace feed stream 20 output from the second pre-reactor C142. The cooled decomposed gas can be output from the heat exchanger E305 at a preselected cooling temperature. Such a temperature can be lower than the temperature at which the gas is output from the furnace F201 (for example, it can be 500 °C to 600 °C, it can be 450 °C to 550 °C, etc.). The cooled decomposed gas can be fed to other heat exchangers and can be output from the heat exchanger E305 to undergo additional cooling before the decomposed gas is fed to the hydrogen recovery unit U501.

[0071] For example, the cooled stream 26 of the decomposed gas is output from the heat exchanger E305, fed to the heat exchanger E310, and then fed to other heat exchangers E311 and E312 and used as a heating medium to heat the ammonia passing through the other heat exchangers E311 and E312, and the decomposed gas can be cooled towards the feed temperature of the desired hydrogen recovery unit.

[0072] For example, the cooled and decomposed gas of stream 26 can be fed to heat exchanger E310 to provide heating for superheating ammonia gas, thereby further reducing the temperature of the decomposed gas and cooling the decomposed gas. The flow 28 of the decomposed gas fed from heat exchanger E310 to heat exchanger E311 is output from heat exchanger E310 to provide a load for evaporating the further heated liquid ammonia fed to heat exchanger E311 via flow 8, and the temperature of the decomposed gas can be further reduced. The flow 30 of the decomposed gas for being fed to heat exchanger E312 is output from heat exchanger E311 to provide a load for further heating the heated pressurized liquid ammonia of flow 6, thereby further reducing the temperature of the decomposed gas again.

[0073] Each of heat exchangers E305, E310, E311, and E312 is depicted as an individual shell and tube style heat exchanger in the exemplary embodiment of FIG. 1 where ammonia passes through the tubes and the decomposed gas passes through the shell side. However, this arrangement can be reversed. Alternatively, these heat exchangers can be combined into a single shell and tube style heat exchanger, or in fact different styles of heat exchangers can be used.

[0074] The flow 32 of the decomposed gas can be output from heat exchanger E312 to be fed to hydrogen recovery unit U501 at a preselected feed temperature of the hydrogen recovery unit. For example, heat exchanger E312 can output the cooled and decomposed gas to heat exchanger E323, and heat exchanger E323 can utilize a refrigerant or coolant (such as cooling water, etc.) to facilitate further cooling of the decomposed gas as desired and further cool the decomposed gas to the feed temperature of the preselected hydrogen recovery unit. Then, the sufficiently cooled decomposed gas can be output from heat exchanger E323 to be fed to hydrogen recovery unit U501 as hydrogen recovery feed stream 34.

[0075] In some embodiments, the hydrogen recovery unit U501 can be configured as a pressure swing adsorption (PSA) system. In other embodiments, other types of adsorption systems can be utilized (e.g., vacuum swing adsorption, temperature swing adsorption, etc.). In still other embodiments, other types of hydrogen separation systems can be utilized to separate the hydrogen of the decomposed gas from the nitrogen gas and other components of the decomposed gas.

[0076] The hydrogen recovery unit U501 can separate hydrogen from other components of the decomposed gas and provide a hydrogen product stream 40 that can contain hydrogen at a desired purity concentration (e.g., 99 mol% hydrogen, 99 mol% - 100 mol% hydrogen, etc.).

[0077] The hydrogen recovery unit U501 can also output a stream 42 that can be an off-gas containing nitrogen gas, residual hydrogen gas, and residual ammonia gas. The stream 42 may also contain other minor components in some embodiments.

[0078] The hydrogen gas in the stream 40 can be fed to a hydrogen liquefaction unit (not shown) to produce liquid hydrogen. In other embodiments, the stream 40 of hydrogen gas can be fed to at least one downstream plant process for use of the hydrogen gas.

[0079] The off-gas stream 42 can be fed as a fuel stream 60 to the combustion chamber of the furnace F201 for internal combustion. Alternatively (or additionally), the stream 42 can be split into multiple portions, one of which can be used as a fuel stream. In still other embodiments, the stream 42 can be split, and none of the split portions need to be fed to the furnace F201 as the fuel stream 60 (e.g., the combustion of the furnace F201 can be provided only via the fuel from the fuel stream 70).

[0080] For example, a first portion 44 of the off-gas in stream 42 is heated by heat exchange in heat exchanger E2112 to produce a stream 60 of heated off-gas, and then stream 60 can be combined with air feed 64 and optionally fuel stream 70 (e.g., a natural gas feed stream, etc.) and split stream 42 such that it is fed to one or more burners in furnace F201. A minimum amount of natural gas or other suitable fuel for fuel stream 70 can be used as trim fuel to provide the fuel balance required in the ignition section of the combustion chamber to supplement the ammonia and / or hydrogen present in the first portion 44 of the off-gas fed to furnace F201.

[0081] A second portion 46 of off-gas 42 (if utilized) can be sent to compression system K681 (e.g., a multi-stage compressor, compressor assembly, etc.) for compression. Compression system K681 can have a plurality of stages with intercoolers between each stage, along with an aftercooler following the last stage. Heat can be recovered from the compressed gas in the intercoolers and aftercooler by heat exchange with a heat transfer fluid. Heat can also be recovered from the lubricating oil and, if a positive displacement compression unit is used, from the cylinders of the compression unit via the heat transfer fluid.

[0082] The intercooler and aftercooler that can be utilized are shown by a single heat exchanger E6816 in FIG. 1, and heat exchanger E6816 can recover heat from stream 48 of compressed off-gas by heat exchange with stream 52 of the heat transfer fluid to produce a stream 50 of cooled compressed off-gas and a stream 54 of heated heat transfer fluid that can be utilized in another process or heat exchanger (e.g., heat exchanger E271, etc.). For example, using the heat transfer fluid heated in cooler E323 and in intercooler and aftercooler E6816, etc., a load can be provided to preheat liquid ammonia by heat exchange in heat exchanger E271.

[0083] The cooled and compressed off-gas in stream 50 can be fed to a phase separator C6816 where condensate can be removed as stream 56. The compressed off-gas can then be recycled as stream 58 to a hydrogen recovery unit U501 to recover additional hydrogen. In other embodiments, this process can be operated without the use of a compression system K681 and a second portion 46 of the off-gas that is processed and returned to the hydrogen recovery unit U501 for recycling. Such embodiments may result in lower hydrogen recovery in the hydrogen recovery unit U501. Reducing hydrogen recovery can result in less hydrogen gas product, but a decrease in hydrogen recovery can reduce the carbon intensity (CI) of the process because the off-gas contains more hydrogen, thereby reducing the need for natural gas as a trim fuel and reducing carbon dioxide emissions. Thus, a decrease in hydrogen recovery may still be desirable. Also, this type of arrangement can provide less overall power consumption due to the non-use of the compression system K681.

[0084] The furnace F201 can discharge at least one stream 72 of flue gas. The discharged flue gas can be at a preselected flue gas discharge temperature (e.g., a temperature in the range of 650 °C to 700 °C, a temperature of about 686 °C, etc.). The stream 72 of flue gas can pass from the radiant section 89 of the furnace F201, where the stream 72 can function as a heating medium as described above, to the convective section 90 of the furnace F201. For example, the flue gas output from the furnace F201 can provide a load for heating the intermediate gas from stream 16 in the heat exchanger E2103, thereby reducing the temperature of the flue gas that can then be output as a heating medium stream 74 for feeding from the heat exchanger E2103 to the heat exchanger E2012, and can provide a load for further heating the heated ammonia gas from stream 12 in the heat exchanger E2102, thereby further reducing the temperature of the flue gas. The flue gas can be routed to provide a heating load in a countercurrent direction to the flow of the feed gas to the radiant section of the furnace F201.

[0085] Output the cooled flue gas from heat exchanger E2102 as a further cooled flue gas stream 76 for feeding to heat exchanger E2142, providing a load for heating the air from stream 62 in heat exchanger E2142, thereby further reducing the temperature of the flue gas. Output the further cooled flue gas from heat exchanger E2142 as stream 78 and feed it to heat exchanger E2112, providing a load for preheating the first portion 44 of the off-gas stream 42 in heat exchanger E2112, thereby further cooling the flue gas.

[0086] The cooled flue gas can be output from the convection section 90 of the direct-fired tube furnace F201 as stream 80 at a preselected flue gas outlet temperature (e.g., a temperature above 100 °C, a temperature of about 121 °C, a temperature above the condensation point of water, a temperature above a preselected acid dew point to avoid acid condensation, etc.). In some embodiments, the cooled flue gas can be passed through an induced draft fan K211 for discharging as discharge stream 82. Embodiments can be configured to utilize a practical amount of useful energy from the flue gas for the economic exhaust of the cooled flue gas to the atmosphere. In some embodiments, the flue gas may first undergo other treatments (e.g., carbon dioxide capture, particulate removal treatment, etc.) depending on the composition of the flue gas.

[0087] In some embodiments, oil from a boil-off gas compressor (not shown) used with an ammonia storage tank (not shown) may be present in the liquid ammonia in an amount up to about 5 ppm at any location where ammonia is produced, or where ammonia is decomposed, or in fact at any passing point between these two locations. In some configurations, it may be desirable to remove the oil before the ammonia is exposed to the catalyst in the pre-reactor and / or furnace F201. The oil can be removed by passing the ammonia through an activated carbon bed or through one or more other types of oil removal treatment units. When the oil is to be removed from the ammonia, the oil removal unit (not shown) can be located in stream 2 (e.g., in the feed line to pump P101), in stream 4 (e.g., between pump P101 and heat exchanger E271), in stream 6 (e.g., between heat exchanger E271 and heat exchanger E312), in stream 8 (e.g., between heat exchangers E312 and E311), in stream 10 (e.g., between heat exchangers E311 and E310), or at other suitable locations upstream of the pre-reactor and furnace F201.

[0088] One or more tubes of furnace F201, and / or the pre-reactor upstream of furnace F201, can include a catalyst material for promoting ammonia decomposition. These catalyst materials can include, for example, metals for promoting an ammonia decomposition reaction that decomposes ammonia into nitrogen gas and hydrogen gas. Metals that can be included in the catalyst material include transition metals such as Group 6 of the periodic table (e.g., chromium (Cr) and molybdenum (Mo)); Group 8 of the periodic table (e.g., iron (Fe), ruthenium (Ru), and osmium (Os)); Group 9 of the periodic table (e.g., cobalt (Co), rhodium (Rh), and iridium (Ir)); Group 10 of the periodic table (e.g., nickel (Ni), palladium (Pd), and platinum (Pt)); and Group 11 of the periodic table (e.g., copper (Cu), silver (Ag), and gold (Au)). Metalloids (e.g., tellurium (Te), etc.) can also be used.

[0089] The activity of some of these metals as catalysts for ammonia decomposition has been reported by Masel et al (Catalyst Letters, vol.96, Nos 3-4, July 2004) to vary in the following order: Ru>Ni>Rh>Co>Ir>Fe>>Pt>Cr>Pd>Cu>>Te (Ru is a more active catalyst and Te is a less active catalyst).

[0090] The metal of the catalyst may not be supported, but is usually supported on a suitable support (e.g., metal oxide supports such as silica (SiO 2 ), alumina (Al 2 O 3 ), zirconia (ZrO 2 ), etc.), or mixed metal oxide supports such as spinel (MgAl 2 O 4 ) or perovskite (CaTiO 3 ). The activity of the supported metal catalyst may depend, in part, on the loading of the catalytically active metal on the support. In this regard, the metal loading can vary according to a set of preselected design criteria. In some embodiments, the metal loading of the catalyst material can be in the range of about 0.1 wt% to about 70 wt%. For example, in some catalyst materials, the loading may be closer to the lower end of the range (e.g., for a more active metal such as ruthenium, about 0.1 wt% to about 10 wt%, or about 0.2 wt% to about 5 wt%), and for a less active metal (e.g., nickel), the loading may be closer to the upper end of the range (e.g., about 20 wt% to about 65 wt% etc.).

[0091] The supported metal catalyst that can be used cannot be promoted, or can be promoted with at least one other metal, e.g., one or more Group 1 metals (e.g., lithium (Li), sodium (Na), and potassium (K)), Group 2 metals (e.g., magnesium (Mg) and calcium (Ca)), or Group 13 metals (e.g., aluminum (Al)) to improve the activity of the catalyst material.

[0092] Bimetallic catalysts, or catalysts containing two catalytically active metals, are also suitable for use in the present invention. Examples include US Patent Application Publication No. 2021 / 0001311A (e.g., CoNi-MgSrCeO 4 and 1 wt% K-CoNi-MgSrCeO 4 ), composite metals or metal alloys or metal nanoclusters supported on perovskites, composite oxides or nitrides, or mixed oxides or mixed nitrides. Other types of multiple metal ammonia decomposition catalysts can also be utilized.

[0093] In embodiments of the apparatus and process, any number of suitable ammonia decomposition catalysts can be used as the catalyst material. Examples of suitable catalyst materials are disclosed in US Patent Application Publication No. 2015 / 0217278A and Lamb et al (Int. J. Hydrogen Energy, 44 (2019) pp3726-3736) and Boisen et al (J. Catalysis 230 (2005) pp309-312).

[0094] Before the operation of the apparatus 1 for ammonia decomposition, the catalyst material in one or more tubes of the furnace F201 and / or one or more pre-reactors (e.g., in an embodiment where multiple pre-reactors can be utilized, the first and second pre-reactors C142 and C141) can be fully activated through a catalyst activation process. When the catalyst material is sufficiently activated so that ammonia decomposition can be efficiently carried out in accordance with a preselected ammonia decomposition design temperature of the apparatus 1 for ammonia decomposition, the catalyst material can be regarded as being fully activated. For example, the catalyst material can be fully activated when the entire oxide layer or passivation layer is removed from the catalyst material. As another example, when a significant portion of the oxide layer or passivation layer is removed from the catalyst material (e.g., 55% - 100% of the passivation layer and / or the oxide of the catalyst material is removed, 75% - 100% of the passivation layer and / or the oxide of the catalyst material is removed, etc.) so that the ammonia decomposition temperature required for ammonia decomposition can be significantly reduced within the preselected design parameters of the apparatus 1 for ammonia decomposition, the catalyst material can be fully activated. As yet another example, the complete activation of the catalyst material can be carried out when the use of the catalyst for promoting ammonia decomposition can be provided without any heat generation through the catalyst material. As yet another example, when the use of the catalyst material for promoting ammonia decomposition can be provided without using an excessive temperature for the ammonia decomposition reaction within the preselected temperature design limits of the apparatus 1, the complete activation of the catalyst material can be obtained. As yet another example, the complete activation of the catalyst material can be detected when the apparatus 1 for ammonia decomposition can decompose ammonia within the preselected design criteria of the apparatus 1 when the catalyst material is sufficiently activated. As yet another example, the catalyst material can be fully activated when the use of the catalyst for promoting ammonia decomposition can be provided without causing a significant level of heat generation from the catalyst. Position the fully activated catalyst material so that the catalyst material is in a suitable state (e.g., through a significant removal of the passivation layer and / or a significant removal of the oxide from the catalyst material, etc.), and ammonia decomposition can be promoted within an acceptable rate defined by the preselected design criteria of the apparatus 1 for ammonia decomposition.Detection of complete activation of the catalyst material can be provided via monitoring of a preselected set of criteria that can include a predefined temperature profile and / or a predefined reactant concentration profile during the catalyst activation process.

[0095] The catalyst activation process can be utilized at the start of the process (e.g., after installation of the ammonia decomposition facility, after a cycle of replacing the used catalyst material with fresh catalyst material, etc.). The activation process utilized for activation of the catalyst material can utilize the process elements of the ammonia decomposition apparatus 1 before a larger ammonia feed for generating hydrogen via the ammonia decomposition operation is fed.

[0096] For example, in a first catalyst activation phase, hydrogen (H2) can be fed to the apparatus as a first reactant for feeding to the pre-reactor and furnace F201 to help promote activation of the catalyst material within the tubes in the radiation section 89 of the furnace F201 and the pre-reactor (e.g., pre-reactors C141 and C142). In some configurations, hydrogen H2 can be fed to a conduit through which ammonia passes during the ammonia decomposition operation to preheat it before being fed to the pre-reactor and furnace F201. For example, hydrogen H2 can be fed to a preheat exchanger feed conduit through which the flow 6 of preheated liquid ammonia passes and reaches the heat exchanger E312 when the ammonia decomposition operation is to be performed.

[0097] Hydrogen H2 can be fed, in some embodiments, as a mixture of hydrogen gas and nitrogen gas to provide a desired concentration of hydrogen as a first reactant gas during a first catalyst activation phase. Nitrogen can also be injected into this reactant gas as it passes towards the pre-reactor and furnace F201 via at least one nitrogen injection feed (N2). The hydrogen reactant stream can be preheated via the flue gas output from the combustion of the fuel stream 70 that can occur through a heat exchanger and through the combustion chamber of furnace F201. The heat from the combusted fuel can provide preheating to the first reactant, and also provide a heat source for heating the catalyst material during activation of the catalyst such that the temperature of the catalyst rises in a desired ordered manner while the catalyst is simultaneously exposed to the reactant hydrogen gas for activation of the catalyst material.

[0098] For example, the flue gas output from furnace F201 can be utilized as a heating medium to preheat the hydrogen reactant gas passing through one or more of the preheating heat exchangers (e.g., heat exchanger E2102 or other heat exchanger). In some embodiments, the hydrogen reactant gas can be injected to pass only through a subset of such heat exchangers depending on how much preheating of the hydrogen reactant is required to provide the desired heating of the catalyst material via the heated stream of reactant gas.

[0099] The preheated hydrogen reactant gas can then be fed to the first pre-reactor C141 to pass through the bed of catalyst material in the vessel of that reactor. The hydrogen reactant gas and products from the catalyst activation reaction that can occur from the oxide, oxide layer, or passivation layer of the catalyst material reacting with the hydrogen in the reactant gas stream are output from the first pre-reactor C141 and, after heating in heat exchanger E2103, can heat the reactant stream to the desired second pre-reactor feed temperature for later feeding the reactant stream to the second pre-reactor C142.

[0100] The preheated hydrogen reactant gas can then be fed through a bed of catalyst material in a second pre-reactor C142, whereby products from a passivation layer of the catalyst material or a catalytic activation reaction that can occur from oxides that react with the hydrogen of the hydrogen reactant gas and the reactant gas stream are then output from the second pre-reactor C142 and, after passing through heating in a heat exchanger E305, can heat the reactant stream to a desired furnace feed temperature for feeding the reactant stream into one or more tubes of a furnace F201 for activation of the catalyst material within the tubes of the radiant section 89 of the furnace F201 later.

[0101] The formation of the first reactant gas and the catalytic activation product element via a catalytic activation process in which the first reactant gas (e.g., hydrogen) reacts with an oxide of a catalyst material that is not yet fully activated (e.g., an oxide of an oxide layer, an oxide of a passivation layer, etc.) can be carried out in the first catalytic activation phase such that the reactant gas is recycled during the first catalytic activation phase. For example, the internal reactant gas and the catalytic activation product element can be output from the tubes in the radiation section 89 of the furnace F201 while simultaneously undergoing heating via combustion of fuel in the furnace to preheat the fresh and / or recycled reactant gas fed towards the preheating reactor and the furnace F201 and to pass through the heat exchangers E305, E310, E311, and / or E312 later. The first reactant gas then passes through a knockout drum disposed upstream of the hydrogen recovery unit U501 to help remove water from the reactant gas that may be present via the activation process and then can pass through the reactant recycle conduit arrangement for recirculation through the heat exchanger, the pre-reactor, and the tubes of the furnace F201. The reactant recycle conduit arrangement is arranged and configured such that the recycled reactant passes through a first recycle conduit segment HR1 disposed between positions upstream of the hydrogen recovery unit U501, passes the first reactant gas through a compression system K681 where it is compressed, and then is output for recirculation to account for the pressure drop that may occur from the reactant gas passing through different process elements. Nitrogen (N2) can also be fed into the first reactant to help increase the nitrogen concentration of the reactant gas and / or to serve to provide the desired flow rate of the reactant gas. For example, nitrogen can be mixed with the hydrogen of the first reactant to provide the first reactant at a preselected flow rate and / or to provide a preselected concentration of hydrogen within the first reactant utilized in the first catalytic activation phase.

[0102] It may be necessary during the recirculation of the reactant gas to take into account the desired hydrogen concentration in the reactant gas, or the desired temperature profile, and / or the removal of undesired components (e.g., reducing the water content in the reactant gas). A portion of the reactant gas can be exhausted via an exhaust stream (vent). The exhaust can make it possible to remove water that can accumulate in the reactant gas via the exhaust. Also, fresh hydrogen gas H2 and / or nitrogen (N2) are injected into the recirculated reactant gas during the first catalyst activation phase, and a replenishment of hydrogen and / or nitrogen can be provided taking into account that hydrogen and / or nitrogen can react with the oxides, oxide layers, and / or passivation layers of the catalyst material in the furnace F201 and the pre-reactors (e.g., pre-reactors C141 and C142) while their materials are not yet fully activated.

[0103] After the pressure of the reactant gas is increased by the compression of the compression system K681, the recirculated output reactant gas can have a higher pressure and can pass through the phase separator C6816. Moisture (e.g., water) can be removed as a liquid stream 56 via the phase separator, and the reactant gas is then fed as a stream 58 for passage through a second reactant recirculation duct segment HR2 having an inlet positioned between the phase separator C6816 and the hydrogen recovery unit and an outlet in fluid communication with a conduit through which the reactant gas can pass to be directed to the heat exchanger, the pre-reactor, and the furnace F201. For example, the outlet of the second reactant recirculation duct segment HR2 can be at a location where nitrogen (N2) can be injected upstream of one or more heat exchangers (e.g., upstream of heat exchangers E312, E311, and / or E310), or upstream of the pre-reactor, and can also be drawn to another location upstream of the furnace F201 for passage through one or more of the heat exchanger, the pre-reactor, and the tubes of the furnace F201.

[0104] After the first level of catalyst activation is detected, the catalyst activation process can transition to a second catalyst activation phase and then be adjusted to initiate the second catalyst activation phase for the completion of the catalyst activation process. In some embodiments, the first level of catalyst activation can be preselected or predefined such that the catalyst material in the pre-reactor is fully activated during the first level of catalyst activation. Also, the first level of catalyst activation can be preselected or predefined such that the catalyst material of the more highly active catalyst material in the tubes of furnace F201 can be fully activated (e.g., in an embodiment where the upstream layer contains a more highly active catalyst material (e.g., a Ru-based catalyst material) and the downstream layer contains a less highly active catalyst material (e.g., a Ni-based catalyst material), the upstream layer of the catalyst material in the tubes of furnace F201). The first level of catalyst activation can be predefined or preselected such that at least one layer of the catalyst material in furnace F201 has not yet been fully activated and requires additional activation to be fully activated.

[0105] In some embodiments, one or more sensors collect data (e.g., temperature data, hydrogen concentration data, etc.) to detect that the first level of catalyst activation has occurred, indicating that the first catalyst activation phase has been reached and that it is appropriate to transition to the second catalyst activation phase. For example, the detection of a first preselected temperature profile and / or hydrogen concentration present in furnace F201, which can be provided via one or more sensors of furnace F201 or apparatus 1, can be utilized to determine that the first level of catalyst activation has occurred. Such detection can be facilitated by a controller or control device communicatively connected to one or more such sensors that receive the sensor data and provide an output to the user indicating that the first preselected level of catalyst activation has occurred.

[0106] Examples of the detected first - level catalyst activation can include detection of a temperature of 150°C to 500°C at the outlet region or outlet of the radiation section 89 of furnace F201, a duration of exposure of hydrogen to the first reactant for 1 hour to 48 hours, and / or a detected hydrogen concentration at the outlet of the furnace tube having an upstream catalyst material layer and a downstream catalyst material layer with 10 mol% or more. (For example, 10 mol% to 30 mol%, 10 mol% to 20 mol%, 10 mol% to 25 mol%, etc.). The first - level catalyst activation can also (or alternatively) be detected based on monitoring of heat generation within the design constraints of apparatus 1. One or more heat - generation conditions that can be monitored include, for example, detecting a temperature rise greater than a pre - selected temperature rise over a pre - selected period during the first catalyst activation phase (e.g., a temperature rise of 5°C to 50°C over a pre - selected period during the first catalyst activation phase, a temperature rise of 15°C over a pre - selected period during the first catalyst activation phase, a temperature rise of 5°C to 15°C over a pre - selected period during the first catalyst activation phase, a temperature rise of 3°C to 12°C over a pre - selected period during the first catalyst activation phase, etc.).

[0107] Other embodiments can utilize other predetermined criteria to facilitate detection of the first - level catalyst activation for use in triggering the transition from the first catalyst activation phase to the second catalyst activation phase. The transition can be made immediately after the first phase is completed such that the adjustment from the first catalyst activation phase to the second catalyst activation phase is made immediately after the transition from the first catalyst activation phase to the second catalyst activation phase.

[0108] For example, in response to the detection of this first level of catalyst activation, a second catalyst activation phase can be initiated to continue the catalyst activation process. For example, such a catalyst activation phase transition can occur, for example, after the temperature of the tubes within the radiation section 89 of the furnace F201 reaches a temperature in the range of 300°C to 550°C, and / or after the hydrogen concentration is detected to be in the range of 20 to 25 mol% or 15 to 25 mol%. As another example, the detection of the temperature of the flue gas output from the radiation section 89 of the furnace F201, which is at a temperature of 400°C, 450°C, 500°C, or other temperatures in the range of 400°C to 500°C, can be used to detect the first level of catalyst activation and trigger the transition to the second catalyst activation phase. As another example, the detection of the temperature of the reactant gas (which can include reactant / catalyst material reaction products including water, etc.) output from the tubes of the radiation section 89 of the furnace F201, which is at a temperature of 400°C, 450°C, 500°C, or other temperatures in the range of 400°C to 500°C, can be used to detect the first level of catalyst activation and trigger the transition to the second catalyst activation phase.

[0109] As yet another example for detecting that the first level of catalyst activation is satisfied, a preselected temperature threshold at a particular location (e.g., the outlet region of the radiant section 89 of the furnace) can be selected based on the temperature rating of the heat exchanger upstream of furnace F201 for preheating the ammonia feed fed to the tubes of furnace F201 for the ammonia decomposition operation, and / or the SCR that can be utilized upstream of furnace F201 for preheating the ammonia feed that is to be fed to the tubes of furnace F201 for the decomposition of ammonia. The temperature selected to facilitate the detection of the first level of catalyst activation that is satisfied to transition from the first catalyst activation phase to the second catalyst activation phase can be selected, for example, to avoid whether the temperature of this equipment is at, above, or within a preselected variance of the temperature rating of the equipment (e.g., 15 °C or 20 °C lower than its temperature rating). Using such a temperature selection profile, during the catalyst activation process that can be used to fully activate all of the catalyst materials in the tubes of furnace F201 and the pre-reactor upstream of the furnace, it can be helpful to avoid whether the equipment is at or above the designed temperature rating of the equipment.

[0110] Of course (and as described above, and as described elsewhere in this specification), other preselected first catalyst activation temperature profiles and / or preselected first catalyst activation hydrogen concentrations can be used as well to predefine the first level of catalyst activation obtained through the first catalyst activation phase. The selection of the temperature profile, reactant concentration, and / or other parameters (e.g., heat generation related parameters) that can be utilized can depend, for example, on the sizing of the tubes of furnace F201 having the catalyst material, the size and number of the pre-reactor having the catalyst material, the type of catalyst material to be activated, and the temperature ratings of the different equipment of apparatus 1.

[0111] The second catalyst activation phase can be initiated by stopping the feed of hydrogen (or other first reactant gas) to the pre-reactor and furnace F201 and starting the feed of ammonia as the second reactant to the pre-reactor and the furnace catalyst material. For example, the feed of liquid ammonia 2 can be passed through a preheating heat exchanger, the pre-reactor, and the furnace via pump P101, which is started to feed ammonia as the second reactant. In some embodiments, nitrogen can be mixed with ammonia to dilute the ammonia concentration in the feed of ammonia passed as the second reactant to the pre-reactor and furnace F201. For example, nitrogen can be mixed with ammonia to provide a desired flow rate of the second reactant when the second reactant passes through the catalyst material including the tubes of the pre-reactor and furnace F201. For example, nitrogen can be mixed with the ammonia of the second reactant to provide the second reactant at a preselected flow rate and / or to provide ammonia at a preselected concentration of the second reactant used in the second catalyst activation phase.

[0112] Also, the further feed of hydrogen H2 as the first reactant can be stopped, and the hydrogen that has been fed and / or recycled through the reactant recycle conduit arrangement can be stopped via at least one exhaust conduit for providing at least one exhaust stream (vent), through the exhaust of the hydrogen reactant with the catalyst activation reaction product contained therein. The exhaust of the utilized and / or recycled hydrogen reactant stream can be exhausted so that the reactant gas stream utilized during the initial first catalyst activation phase does not directly mix with the ammonia fed to the apparatus via the feed of liquid ammonia 2 for the second catalyst activation phase. However, the exhaust of the hydrogen reactant gas can be done such that the hydrogen gas passes through heat exchangers E305, E310, E311, and E312 to preheat the ammonia. The flue gas from furnace F201 can also be used to preheat the ammonia via heat exchangers E2103 and E2012 and the oxidant preheating heat exchanger E2142 for controlling the temperature of the ammonia reactant gas utilized during the second catalyst activation phase.

[0113] The feed rate of ammonia provided as a second reactant for the second catalyst activation phase can be a much lower feed rate than the feed of liquid ammonia 2 provided during the ammonia decomposition operation. For example, the feed rate of ammonia for the second catalyst activation phase can be 5% to 45%, or 20% to 40%, of the typically designed feed rate for the feed of liquid ammonia for the ammonia decomposition operation of apparatus 1. After the hydrogen reactant gas has been sufficiently exhausted, the ammonia utilized as a reactant for the second catalyst activation phase can be exhausted via an exhaust conduit (vent) upstream of the hydrogen recovery unit so that the ammonia used in the second catalyst activation phase is not recycled (e.g., the ammonia passes through the pre-reactor and furnace F201 once and is used once through the process without being recycled).

[0114] In other embodiments, it is contemplated that ammonia can alternatively be recycled to further limit the amount of ammonia feed required for the second catalyst activation phase. In such embodiments, it is envisioned that ammonia recycling can be provided using a reactant recycling conduit arrangement in a manner similar to how the first reactant gas containing hydrogen can be recycled.

[0115] As can be understood from above, the feed of liquid ammonia 2 fed to the apparatus for the second catalyst activation phase can be passed through preheat heat exchangers E312, E311, E310, and E2102 to preheat it to a desired temperature for later feeding to the first pre-reactor C141. Fresh ammonia from a liquid ammonia source (e.g., a storage container or a storage unit for liquid ammonia) can be provided for the continuous operation of the second catalyst activation phase so as to provide a heat sink that can help keep the liquid ammonia below a preselected temperature in various upstream preheat heat exchangers (e.g., heat exchangers E310, E311, E312, etc.) (e.g., to avoid overheating of the heat exchangers beyond the design temperature specifications).

[0116] The preheated ammonia reactant can be preheated so that ammonia vaporizes and becomes a gas before being fed into the first pre-reactor C141 via a preheating heat exchanger. The ammonia reactant gas can then be fed into the first pre-reactor C141 to pass through the bed of catalyst material in the vessel of the reactor. Ammonia can react with the internal catalyst material and can be partially decomposed internally due to the complete activation of the catalyst material (for example, ammonia can be converted into some hydrogen, nitrogen, and other components by reacting with the catalyst material in the first pre-reactor). The ammonia reactant gas and products from the possible catalyst activation reaction are output from the first pre-reactor C141 and, after passing through heating in the heat exchanger E2103, can heat the ammonia reactant stream to the desired second pre-reactor feed temperature for later feeding the reactant stream into the second pre-reactor C142.

[0117] The preheated ammonia reactant gas can then be fed through the bed of catalyst material in the second pre-reactor C142, whereby ammonia reacts with the catalyst material in the second pre-reactor C142, and the ammonia reactant gas and products (for example, hydrogen and nitrogen) from the reaction that can occur are output from the second pre-reactor C142 and fed into the heat exchanger E305 to heat the ammonia reactant stream to the desired furnace feed temperature for later feeding the reactant stream into one or more tubes of the furnace F201 for the activation of the catalyst material in the tubes in the radiation section 89 of the furnace F201.

[0118] The formation of a second reactant gas and catalytic activation product elements (e.g., nitrogen and hydrogen) via a catalytic activation process in which a reactant gas (e.g., ammonia) interacts with a catalyst material can be carried out in a second catalytic activation phase such that the reactant gas passes through the tubes of furnace F201. Ammonia and the reaction products (e.g., nitrogen and hydrogen) can be passed through the furnace tubes to serve to fully activate a less active catalyst material layer (e.g., the downstream layer if the downstream layer is a Ni-based catalyst material and the upstream layer is a Ru-based catalyst material) within the tubes that are not yet fully activated. Then, while the ammonia reactant gas and product elements can be output from the radiation section 89 of furnace F201, the flue gas can also be output from the radiation section 89 for feeding to the conventional section 90 of furnace F201 for passage through different heat exchangers E2103, E2102, E2142, and / or E2112.

[0119] For example, the internal ammonia reactant gas and catalytic activation product elements can be output from the tubes of the radiation section 89 of furnace F201 while simultaneously undergoing heating via combustion of fuel in the furnace to pass through heat exchangers E305, E301, E311, and / or E312 later to preheat fresh ammonia reactant gas. Then, after the ammonia reactant gas is output from heat exchanger E312, it can be exhausted upstream of hydrogen recovery unit U501.

[0120] Alternatively, in embodiments where ammonia can be recycled, the ammonia reactant gas and activation products can be passed through a reactant recycle conduit arrangement for returning them through the heat exchanger, pre-reactor, and tubes of furnace F201 for recycling. In such embodiments where ammonia recycling can be utilized, the reactant recycle conduit arrangement is such that the recycled second reactant (and products from catalytic activation reactions that a portion of the ammonia may have with catalytic material present therein) is recycled through a first reactant recycle conduit segment HR1 that can pass through a feed conduit for a compression system K681 for internal compression so as to help account for the pressure drop that can occur from the reactant gas passing through different process elements, and can be arranged to pass through the compression system K681. The reactant gas recycle conduit HR2 can be arranged, for example, in such embodiments as well to facilitate routing of the compressed reactant gas output from the compression system K681 back to the preheat heat exchanger for recycling (e.g., the compressed ammonia can pass through a phase separator C6816 and then, at a location between the hydrogen recovery unit U501 and the phase separator, be recycled back towards the heat exchanger and / or pre-reactor via a second reactant recycle conduit segment HR2 such that it changes direction).

[0121] The feed rate of the feed of liquid ammonia 2 can be similarly adjusted taking into account the recycling of the ammonia reactant gas (when ammonia recycling is utilized). Also, if at least a portion of the ammonia is recycled instead of being exhausted in a single pass processing scheme, during the second catalytic activation phase, the ammonia reactant gas can be periodically exhausted through at least one exhaust stream (vent) to account for one or more parameters of a preselected control criterion.

[0122] Ammonia can pass through the tubes of the first pre-reactor C141, the second pre-reactor C142, and the radiation section 89 of the furnace F201 during the second catalyst activation phase to provide sequential heating of the catalyst material in the tubes, thereby providing complete catalyst activation in a preselected sequence. For example, the heating of the catalyst material can be provided through the passage of heated ammonia gas, and the heated ammonia gas can be heated through the combustion of fuel in the furnace F201, whereby the least active catalyst material in the tubes of the furnace is finally completely activated. For example, if the downstream layer of the catalyst material in the tubes of the furnace F201 is Ni-based and the upstream layer of the catalyst material is Ru-based, the downstream Ni-based catalyst material can be finally completely activated during the second catalyst activation phase through the use of ammonia reactant gas.

[0123] In some embodiments, the heating of the catalyst material can be provided more directly through the feed of a heated second reactant containing ammonia gas during the second catalyst activation phase and the feed of a first reactant containing hydrogen used in the first catalyst activation phase, whereby the more active upstream layer of the catalyst material in the tubes of the furnace F201 is first completely activated, the layer of the catalyst material of the second pre-reactor C142 that is more active than the less active layer of the catalyst material of the second pre-reactor is second completely activated, the catalyst material of the first pre-reactor C141 is third completely activated, the less active layer of the catalyst material of the second pre-reactor C142 is fourth completely activated, and the less active downstream layer of the catalyst material in the tubes of the furnace F201 is finally completely activated.

[0124] The heating of the catalyst material provided via the first and second reactants can be driven mainly via the heat of the flue gas of furnace F201, which heats the fluid in the tubes of the furnace within the radiation zone 89 and can also be used as a heating medium in one or more preheating heat exchangers. Also, the heating of the reactants passing through the tubes of furnace F201 can be further utilized to provide preheating of the reactants as the output reactant stream passes through heat exchangers E305, E310, E311, and E312, etc. The combustion of the fuel in furnace F201 can be regarded as the main source of the heating provided via catalyst activation during the first and second catalyst activation phases.

[0125] Such feeding of the first and second reactants via the first and second catalyst activation phases can be carried out such that the more active layer of the catalyst material in the tubes of furnace F201 is first fully activated, the more active layer of the catalyst material of the second reactor C142, which is more active than the less active layer of the catalyst material of the second reactor, is second fully activated, the catalyst material of the first reactor C141 is third fully activated, and the less active layer of the catalyst material of the second reactor C142 is fourth fully activated in the first catalyst activation phase using the first reactor. Then, the less active layer of the catalyst material in the tubes of furnace F201 can be finally fully activated via the second reactant containing ammonia via the second catalyst activation phase. In embodiments where the less active layer of the catalyst material in the tubes of the furnace is the downstream layer, this will result in the downstream layer of the catalyst material in the tubes of furnace F201 being finally fully activated.

[0126] In some embodiments, it is contemplated that only a single pre-reactor or three or more pre-reactors may be present. In such embodiments, the first and second catalyst activation phases may be performed such that the more active layer of the catalyst material in the tubes of furnace F201 is activated first (e.g., the upstream layer when the upstream layer of the catalyst material is a Ru-based catalyst and the downstream layer of the catalyst material is a Ni-based catalyst). Then, the pre-reactor can activate the catalyst material in a sequential manner before the downstream layer of the catalyst material, which is the less active layer of the catalyst material in the tubes of furnace F201, is finally activated. If there is only one pre-reactor, the more active catalyst material in the tubes of the furnace is activated first, the catalyst material of the single pre-reactor is activated second, and then the less active layer of the catalyst material in the tubes of furnace F201 can be activated last (e.g., if the Ni-based catalyst is the downstream layer and the Ru-based catalyst is the upstream layer in the furnace tubes, the downstream layer of the tubes of furnace F201 can be finally fully activated), and the first and second catalyst activation phases can be performed.

[0127] As another example, in an embodiment where there may be three pre-reactors, the first and second catalyst activation phases may be performed such that the most downstream pre-reactor of the group of pre-reactors can first activate its catalyst material, then the pre-reactor downstream of the first pre-reactor can second activate the catalyst material, the most upstream pre-reactor can then activate its catalyst material, and then the downstream layer of the catalyst material in the tubes of furnace F201 can be activated to complete the second catalyst activation phase.

[0128] The different catalyst materials in the downstream and upstream layers of the catalyst material in the furnace tubes, and the sequencing of the activation of the catalyst material in the pre-reactor can be configured such that those elements reach different higher temperatures over a period of time at a desired activation rate that promotes complete activation of the catalyst material without causing sintering of the catalyst material. The overall temperature of each reactor and furnace desired for the targeted sequenced catalyst activation can depend on the type of catalyst material utilized. In some embodiments, the temperature profile can be controlled such that the higher temperature points of the different elements coincide with the desired sequencing for catalyst activation. For example, the upstream portion of furnace F201 can first reach the desired final activation temperature for complete activation of the upstream portion of the catalyst material within the tubes of the radiant section 89 of furnace F201. Next, the temperature of the second pre-reactor C142 can reach the desired final activation temperature for complete activation of the catalyst material of that pre-reactor. Next, the first pre-reactor C141 can reach the desired final activation temperature for complete activation of the catalyst material of that pre-reactor. Finally, the temperature of the downstream portion of the tubes of the radiant section having the second downstream layer of catalyst material can reach the desired final activation temperature of the downstream portion for complete activation of the catalyst material. In such embodiments, the temperature of the downstream portion of the catalyst material in the furnace tubes can be higher than the other activation temperatures (e.g., it can be 500°C to 700°C, or 600°C to 650°C, etc.). The other activation temperatures can be approximately the same or can vary between different desired temperatures (e.g., the temperature can vary from 300°C to 450°C, or 350°C to 500°C, etc.).

[0129] Figure 2 also shows an exemplary embodiment of a catalyst activation process that can include first and second catalyst activation phases. As can be seen from Figure 2, in a first step S1, hydrogen or other first reactant can be fed to activate the catalyst material in the upstream reactors (e.g., pre-reactors C141 and C142) and the furnace downstream of the reactor (e.g., furnace F201). Hydrogen can be fed during the first catalyst activation phase of the first step S1 until it is determined that the upstream section of the catalyst material in furnace F201 is at a first preselected activation condition (e.g., furnace F201 is determined to have conditions such that the furnace is at a first preselected temperature and / or a first preselected hydrogen concentration is detected in one or more tubes of the radiation section 89 of furnace F201). Complete activation of the catalyst material can include removal of the coating of the catalyst material (e.g., complete removal of the oxide coating the entire outer surface of the catalyst material, complete removal of the passivation layer covering the entire outer surface of the catalyst material, etc.).

[0130] In a second step S2, ammonia can be fed to the apparatus as a second reactant for replacement of the first reactant (e.g., hydrogen) for continued activation of the catalyst material in the furnace downstream of the reactor so that the less active catalyst in the furnace can be fully activated and for introduction to the furnace and upstream reactors (e.g., pre-reactor C141, pre-reactor C142, etc.).

[0131] In some embodiments, the feeding of the first reactant containing hydrogen in the first step S1 and the feeding of the second reactant containing ammonia in the second step S2 may be carried out such that the more active part of the catalyst material in the furnace is first completely activated, the more active catalyst material in the second reactor (e.g., the second pre-reactor C142) of the upstream reactor downstream of the first reactor (e.g., the first pre-reactor C141) of the upstream reactor is second completely activated, the catalyst material in the first reactor of the upstream reactor is third completely activated, the less active catalyst material in the second reactor is fourth activated, and the less active part of the catalyst material in the furnace is finally completely activated. Ammonia can be fed as pure ammonia or ammonia diluted with nitrogen and utilized in the second step S2 to completely activate the less active part of the catalyst material in the furnace. The first step S1 can be carried out to completely activate other catalyst materials (e.g., the more active part of the catalyst material in the furnace is completely activated through the first step S1, the more active catalyst material in the second reactor (e.g., the second pre-reactor C142) of the upstream reactor downstream of the first reactor (e.g., the first pre-reactor C141) of the upstream reactor is second completely activated through the first step S1, the catalyst material in the first reactor of the upstream reactor is third completely activated through the first step S1, and the less active catalyst material in the second reactor is fourth activated through the first step S1).

[0132] In still other embodiments, the feeding of the first reactant containing hydrogen may be carried out such that the catalyst material in one or more pre-reactors is first activated in the first step, and the furnace having tubes with less active catalyst material is finally completely activated through the feeding of the second reactant containing ammonia in the second step S2.

[0133] In other embodiments, the feeding of the first reactant can be carried out to first fully activate the catalyst material in one or more pre-reactors and, if present, the more active catalyst material in the tubes of the furnace. Then, the second reactant can be fed to the pre-reactor and the furnace tubes to finally fully activate the less active catalyst in the furnace tubes, completing the full catalytic activation of the catalyst material. Then, a third step S3 can be carried out for the ammonia decomposition operation.

[0134] As described above, in some embodiments, the feeding of ammonia can also be contemplated to include recycling the ammonia reagent of the second reactant to the reactor and the furnace, as well as other elements for catalyst activation (e.g., heat exchangers). The application of heat and the feeding of ammonia can be provided during a second step S2 such that the full activation of the catalyst material in the furnace and the reactor is carried out in a predefined sequence via the feeding of ammonia, which can help avoid sintering of the catalyst material. Also, as described above, the first reactant containing hydrogen previously used in the initial first catalyst activation phase can be removed while the second reactant containing ammonia is utilized (e.g., via the exhaust of the first reactant) for the transition between the first and second catalyst activation phases.

[0135] In the third step S3, after the downstream portion of the catalyst material of the furnace, which can have a less active catalyst material (for example, when the downstream portion of the catalyst material contains a Ni-based catalyst that is less active than the upstream portion of the catalyst material containing a Ru-based catalyst, the downstream portion of the catalyst material in the tube of the radiation section 89 of the furnace F201) is fully activated, ammonia can be fed to the reactor and the furnace to decompose the ammonia and form at least one product stream of hydrogen for use downstream of the ammonia decomposition system (for example, transported to a remote customer via a pipeline or vehicle and fed to a plant connected to the ammonia decomposition system for using hydrogen). The feed rate of ammonia provided during the third step S3 may be considerably higher than the feed of ammonia during the second catalyst activation phase that may be carried out during the second step S2. This process can result in, as discussed above, any exhaust shutdown or exhaust reduction, non-use of the reactant circulation conduit configuration, and optional use of the first portion 44 of the offgas stream 42 and / or the second portion 46 of the offgas stream 42 for use as a fuel source for the furnace, for use in further enhancing hydrogen recovery via the hydrogen recovery unit U501.

[0136] We have found that performing the second catalyst activation phase such that the less active downstream layer of the catalyst material of the furnace F201 is activated last can facilitate temperature control during the catalyst activation process that avoids long-term use of excessive temperatures for the catalyst activation of other upstream equipment so that various upstream equipment can avoid excessive exposure to high temperatures. For example, the temperature profiles to which the preheat heat exchangers E310, E311, E312, E2102, E2103, and E305 can be exposed can be minimized by such a sequence of catalyst activation.

[0137] For example, we have surprisingly found that the control of the temperature profile in furnace F201 can drive the temperature of the catalyst activation process, at least in part, due to the recirculation of reactants during the catalyst activation process. In situations where the catalyst material at a higher activation temperature in the furnace is activated before other upstream equipment can be activated, the temperature of the furnace becomes relatively high, which can result in excessive temperatures when the output reactant gas and flue gas streams pass other elements through the heat exchanger (e.g., recirculate the reactant gas to the pre-reactor). We have found that this can expose the heat exchanger to temperatures that can exceed 600 °C, well above the typical design ratings of heat exchanger equipment. This type of temperature condition during catalyst activation sequencing, where the reactant gas flow passing through the heat exchanger to be preheated is relatively low flow, can result in the heat exchanger and conduits through which the flue gas and high-temperature reactant gas streams pass being exposed to much higher temperatures for a significant portion of the catalyst activation process. We have also found that this type of temperature profile problem can be an important determining factor in the placement of catalyst materials with very high activation temperatures in the tubes of furnace F201 compared to other catalyst materials used in the apparatus.

[0138] We have surprisingly found that controlling the catalyst activation by controlling the temperature of the reactants during staged catalyst activation such that the less active layer of the catalyst material in furnace F201 is activated last can avoid exposing the heat exchanger to high-temperature flue gas and the reactants flowing for a long period of time, thereby avoiding the problem of excessive high-temperature exposure. This can also provide greater design flexibility, maintenance flexibility, and reduced capital costs, and enable the provision of more off-the-shelf equipment in embodiments that can avoid production delays associated with the acquisition of more specialized equipment.

[0139] The embodiments also enable catalytic activation to be performed without detrimental sintering of the catalyst material while the oxide and / or passivation layer is removed from the catalyst material for complete activation of the catalyst material. The first and second catalytic activation phases can be controlled such that the temperature during each phase gradually increases according to a predefined catalytic activation protocol. This temperature control can be used, for example, via the passage of an activation reactant (e.g., hydrogen mixed with nitrogen gas, ammonia, etc.) as described above.

[0140] We have also found that using ammonia as a second reactant for the second catalyst activation phase can reduce the demand for other cooling media / equipment during catalyst activation (such as load savings in cooling water towers or air coolers), and can also provide a cooling source for the entire system (such as the sensible heat, latent heat, endothermic reaction of ammonia decomposition that forms nitrogen and hydrogen during catalyst activation). Ammonia passing through during the process of the second catalyst activation phase can be decomposed in the pre-reactor due to the heat for generating hydrogen and nitrogen, and hydrogen and nitrogen can be provided to the upstream catalyst layer in the tubes of the radiation section 89 of the furnace F201, where ammonia can be further decomposed internally while being utilized as a reactant to provide more hydrogen for the activation of the downstream part of the catalyst material in the tubes of the radiation section 89 of the furnace F201. The ammonia feed rate during activation can be significantly lower than the design rate of ammonia decomposition (for example, about 40% - 50% conversion under the design conditions of ammonia decomposition versus 20% - 30% conversion) so that a higher amount of conversion can be carried out through the pre-reactor than at the design time of ammonia decomposition. Since most of the ammonia used as the second reactant can be converted in the pre-reactor during the second catalyst activation phase, there is little or no endotherm from the ammonia decomposition reaction, so the temperature in the furnace tubes can rapidly rise to the desired activation temperature, consuming the heat generated by the burner of the furnace F201. This enables the activation process to be carried out more rapidly, and at the same time, a stepwise approach for catalyst activation can be provided that can avoid sintering of the catalyst material covered by the passivation layer and provide the desired temperature adjustment.

[0141] After the complete activation of the catalyst material used in the ammonia decomposition apparatus 1 so that the catalyst material is fully activated (for example, the passivation layer has been completely removed from the catalyst material), the ammonia reactant stream can be exhausted to remove impurities (such as water, etc.) from the activation process. Then, the ammonia decomposition operation can be initiated by feeding liquid ammonia at an ammonia decomposition feed rate for hydrogen production via ammonia decomposition (as discussed above, for example). For example, the ammonia decomposition operation utilizes the ammonia flow as discussed above to feed ammonia through the first pre-reactor, the second pre-reactor, and the tubes in the radiation section 89 of furnace F201, decompose the ammonia to produce hydrogen, and then feed the decomposed gas to the hydrogen recovery unit U501 to form a hydrogen production stream 40.

[0142] It should be understood that the catalyst material that can be used in one or more of the pre-reactors and tubes in the radiation section 89 of furnace F201 can be any number of suitable catalyst materials for ammonia decomposition. The catalyst material can include supported catalysts and unsupported catalysts. The catalyst material can include catalysts containing Ni, Ru, and / or other suitable elements that can help promote the decomposition of ammonia into hydrogen and nitrogen. The shape of the catalyst material can also include any of a number of suitable shapes, including irregularly shaped catalyst particles, spherical catalyst particles, tube-shaped catalyst particles, polygonal catalyst particles, or other shaped catalyst particles for the catalyst material. The bed of catalyst material having reactors and / or tubes in the radiation section 89 of furnace F201 can include, for example, an assembly of particulate catalyst particles positioned such that ammonia can pass through the bed in order to contact the catalyst particles or other types of catalyst material.

[0143] It should also be understood that other modifications can be made to meet a particular set of criteria for different embodiments of the apparatus 1 or process. For example, valves, piping, and other conduit elements (e.g., conduit connection mechanisms, tubes, seals, valves, etc.) for interconnecting different units of the apparatus for fluid communication of the flow of fluid between different elements (e.g., pumps, compressors, fans, valves, conduits, etc.) can be arranged to meet a particular plant layout design taking into account the available area of the apparatus, the sized equipment of the apparatus, and other design considerations. For example, the size of each reactor, heat exchanger, and / or furnace, as well as the size and configuration of any adsorber, adsorption system, heat exchanger, conduit, expander, pump, or compressor can be modified to meet a particular set of design criteria. As another example, the flow rate, pressure, and temperature of the fluid passing through one or more heat exchangers and / or reactors and / or at least one furnace, as well as through other plant elements, can vary taking into account different plant design configurations and other design criteria. As yet another example, the number of plant units and how these plant units are arranged can be adjusted to meet a particular set of design criteria. As yet another example, the different structural components of the units of the plant and the material compositions for the plant can be any suitable type of material required to meet a particular set of design criteria.

[0144] As yet another example, in some embodiments, it is contemplated that only a single reactant containing ammonia (e.g., ammonia, ammonia mixed with nitrogen gas, etc.) can be used for catalyst activation. The ammonia utilized is vaporized, optionally mixed with nitrogen, and then can be liquid ammonia that passes through one or more pre-reactors and at least one tube having therein a catalyst material positioned within the radiant section 89 of furnace F201 for activation of the catalyst material. Activation of the catalyst material is carried out over a preselected period according to a preselected activation scheme to provide complete activation of all the catalyst materials within the temperature ratings of the various equipment according to the preselected activation scheme. In some embodiments, such activation can be provided through the use of at least partial recirculation of ammonia while adding additional liquid ammonia to the reactant feed to provide catalyst activation, and while controlling the temperatures of the different pre-reactors / furnace tubes and heat exchangers such that catalyst materials having the highest activation temperature in the furnace tubes are activated last, while other catalyst materials are activated prior to the catalyst materials having the highest activation temperature within the furnace tubes, to provide a sequence of catalyst activation.

[0145] As yet another example, embodiments of apparatus 1 and the process can each be configured to include process control elements (e.g., temperature and pressure sensors, flow sensors, an automated process control system having at least one workstation, where the at least one workstation includes a processor, non-transitory memory, and at least one transceiver, the at least one transceiver being for communicating with sensor elements, valves, and controllers, and the controller being for providing a user interface for an automated process control system that can be implemented on a plant workstation and / or another computer device) arranged and configured to monitor and control operation. Embodiments can similarly utilize a distributed control system (DCS) for implementation of one or more processes and / or for controlling the operation of the apparatus or process.

[0146] As another example, it is contemplated that certain features, whether individually recited or recited as part of an embodiment, may be combined with other individually recited features or with parts of other embodiments. Accordingly, elements and operations of the various embodiments described herein may be combined to provide further embodiments. Thus, specific exemplary embodiments of processes, apparatus, systems, and methods for making and using them have been shown and described above, but the invention is not limited thereto and may be variously embodied in other ways and practiced within the scope of the following claims.

Claims

1. 1. A process for catalyst activation for ammonia decomposition, said process comprising: feeding a first reactant comprising hydrogen to at least one pre-reactor located upstream of a furnace having at least one tube in a radiant section of the furnace, whereby the first reactant passes through a catalytic material of the at least one pre-reactor and thereafter through a catalytic material of the at least one tube in the radiant section of the furnace; in response to detecting a first level of catalyst activation, stopping the feeding of the first reactant and commencing feeding a second reactant comprising ammonia to the at least one pre-reactor and to the at least one tube in the radiant section of the furnace, whereby the second reactant passes through the catalytic material of the at least one pre-reactor and thereafter through the at least one tube in the radiant section of the furnace to fully activate the catalytic material of the at least one tube.

2. 2. The process of claim 1, wherein the feeding of the first reactant and the feeding of the second reactant are performed such that the catalytic material in the upstream portion of the at least one tube is fully activated, then the catalytic material in the at least one pre-reactor is fully activated, then the catalytic material in the downstream portion of the at least one tube is fully activated after the catalytic material in the at least one pre-reactor is fully activated and after the catalytic material in the upstream portion of the at least one tube is fully activated.

3. 2. The process of claim 1, wherein the feeding of the second reactant comprising ammonia is performed such that the catalytic material in the downstream portion of the at least one tube is ultimately fully activated.

4. mixing nitrogen with the ammonia of the second reactant such that the second reactant has a preselected ammonia concentration and / or a preselected flow rate; and / or 10. The process of claim 1, comprising mixing nitrogen with the hydrogen of the first reactant such that the first reactant has a preselected hydrogen concentration and / or such that the first reactant has a preselected flow rate.

5. 2. The process of claim 1, wherein the at least one prereactor comprises a first prereactor having a catalytic material in a vessel of the first prereactor and a second prereactor having a catalytic material in a vessel of the second prereactor, the second prereactor being downstream of the first prereactor such that the second prereactor is between the at least one tube of the furnace and the first prereactor.

6. The delivery of the first reactant comprises: (a) the catalytic material in the upstream portion of the at least one tube is fully activated; (b) the catalytic material of the second prereactor is fully activated; and (c) the catalytic material of the first pre-reactor is fully activated; The delivery of the second reactant comprises:

6. The process of claim 5, wherein (d) the catalytic material in the downstream portion of the at least one tube is fully activated.

7. The process of claim 6 , wherein the catalytic material in the downstream portion of the at least one tube has a higher activation temperature than the catalytic material in the upstream portion of the at least one tube.

8. 8. The process of claim 7, wherein the catalytic material in the downstream portion of the at least one tube has a higher activation temperature than the catalytic material in the first pre-reactor.

9. 10. The process of claim 8, wherein the catalytic material in the downstream portion of the at least one tube has a higher activation temperature than at least a portion of the catalytic material in the second pre-reactor.

10. 2. The process of claim 1, wherein the feeding of the first reactant also comprises recirculating the first reactant through the at least one tube and the at least one pre-reactor for a first period of time.

11. 2. The process of claim 1, comprising responsive to detecting a first level of catalyst activity, venting the first reactant while simultaneously beginning to pump the second reactant toward the at least one prereactor and the at least one tube.

12. 1. An apparatus for ammonia decomposition configured to facilitate catalyst activation, the apparatus comprising: a furnace having at least one tube, the furnace containing catalytic material in the at least one tube for decomposition of ammonia, the catalytic material in the at least one tube having an upstream portion of catalytic material and a downstream portion of catalytic material; at least one pre-reactor located upstream of said at least one tube, said at least one tube being in fluid communication with said at least one pre-reactor; The apparatus, a first reactant can be fed to the at least one prereactor and the at least one tube such that the first reactant passes through the catalytic material of the at least one prereactor and then through the catalytic material of the at least one tube; and an apparatus sized and configured such that, in response to detecting a first level of catalytic activation, the first reactant can be vented and the second reactant can be fed to the at least one prereactor and the at least one tube such that the second reactant can pass through the catalytic material of the at least one prereactor to fully activate at least a portion of the catalytic material in the at least one tube and thereafter pass through the at least one tube.

13. the apparatus is configured such that the feeding of the first reactant is performed such that the upstream portion of the catalytic material of the at least one tube is first fully activated, and then the catalytic material of the at least one pre-reactor is fully activated; 13. The apparatus of claim 12, wherein the second reactant is deliverable to the at least one tube and the at least one pre-reactor such that the downstream portion of the catalytic material of the at least one tube is fully activated after the catalytic material of the at least one pre-reactor is fully activated and after the upstream portion of the catalytic material of the at least one tube is fully activated.

14. 13. The apparatus of claim 12, wherein the apparatus is configured such that the delivery of the second reactant occurs such that the downstream portion of the catalytic material of the at least one tube is ultimately fully activated.

15. 13. The apparatus of claim 12, wherein the at least one prereactor comprises a first prereactor having a catalytic material in a vessel of the first prereactor and a second prereactor having a catalytic material in a vessel of the second prereactor, the second prereactor being downstream of the first prereactor such that the second prereactor is between the at least one tube of the furnace and the first prereactor.

16. The apparatus further comprising: (a) the upstream portion of the catalytic material of the at least one tube is fully activated; (b) the catalytic material of the second prereactor is fully activated; and (c) the catalytic material of the first pre-reactor is fully activated; The delivery of the second reactant comprises:

20. The apparatus of claim 15, further configured to: (d) cause the catalytic material in the downstream portion of the at least one tube to be fully activated.

17. The apparatus of claim 16 , wherein the downstream portion of the catalytic material of the at least one tube has a higher activation temperature than the catalytic material of the upstream portion of the catalytic material of the at least one tube.

18. the downstream portion of the catalytic material of the at least one tube has a higher activation temperature than the catalytic material of the first prereactor; 20. The apparatus of claim 17, wherein the catalytic material in the downstream portion of the at least one tube has a higher activation temperature than at least a portion of the catalytic material in the second pre-reactor.

19. 13. The apparatus of claim 12, comprising a reactant recirculation conduit arrangement positioned such that the first reactant can be recirculated from an outlet of the at least one tube to the at least one pre-reactor.

20. 1. An apparatus for ammonia decomposition configured to facilitate catalyst activation, the apparatus comprising: a furnace having at least one tube, the furnace containing catalytic material in the at least one tube for the decomposition of ammonia, the catalytic material in the at least one tube having a more active portion of the catalytic material that is more active than a less active portion of the catalytic material; at least one pre-reactor located upstream of said at least one tube, said at least one tube being in fluid communication with said at least one pre-reactor; The apparatus, a first reactant can be fed to the at least one prereactor and the at least one tube such that the first reactant passes through the catalytic material of the at least one prereactor and then through the catalytic material of the at least one tube; and an apparatus sized and configured such that, in response to detecting a first level of catalytic activation, the first reactant can be vented and the second reactant can be fed to the at least one prereactor and the at least one tube such that the second reactant can pass through the catalytic material of the at least one prereactor and thereafter pass through the at least one tube to fully activate the less active portion of the catalytic material of the at least one tube.

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