Hydrogen prodution from ammonia by autothermal cracking

Abstract

Process and plant for the production of a product gas containing nitrogen and hydrogen from ammonia, the process comprising the steps of: i) pre-cracking an ammonia feed stream to a pre-cracked process gas containing hydrogen, nitrogen, ammonia by contact with a first ammonia cracking catalyst; ii-1) non-catalytic partial oxidation of the pre-cracked process gas with an oxygen containing gas to a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia; ii-2) cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a second ammonia cracking catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during at least the pre-cracking of the ammonia feed stream, thereby producing said product gas containing nitrogen and hydrogen; iii) withdrawing the product gas. The product gas is purified downstream to a hydrogen product.

Description

[0001] HYDROGEN PRODUCTION FROM AMMONIA BY AUTOTHERMAL CRACKING

[0002] TECHNICAL FIELD

[0003] The present application relates to the production of a hydrogen containing gas from ammonia by a sequence of pre-cracking an ammonia feed into a pre-cracked process gas, non-catalytically partial oxidation of the pre-cracked gas with an oxygen containing gas and cracking of residual amounts of ammonia contained in the partial oxidized process gas to a product gas containing nitrogen and hydrogen, while also reducing nitrogen oxides (NOX) generated in the process. The non-catalytically partial oxidation of the pre-cracked gas with an oxygen containing gas and cracking of residual amounts of ammonia contained in the partial oxidized process gas is autothermal cracking. The product gas may be further purified in hydrogen. The present application is in particular for processes or plants of large capacity, i.e. large-scale hydrogen plants producing at least 300000 Nm3H2 / h.

[0004] BACKGROUND

[0005] In the ammonia cracking process gaseous ammonia is dissociated into a mixture of hydrogen and nitrogen according to the reversible reaction: 2 NH3

[0006]

[0007] N2+ 3 H2. The reaction is endothermic, requiring heat for maintaining the ammonia cracking reaction.

[0008] The ammonia cracking is performed industrially in fired tubular crackers. For instance, Applicant's WO 2022 / 189560 and WO 2024 / 246097 disclose the production of hydrogen from ammonia cracking in fired tubular crackers.

[0009] Applicant's WO 2019 / 038251 Al discloses an autothermal cracking process, in which the amount of nitrogen oxides generated in a non-catalytic partial oxidation step is reduced by more than 80%, practically up to 100% as limited by thermodynamic equilibrium, through reaction of the nitrogen oxides (NOX) with hydrogen by contact with a nickel containing catalyst after the non-catalytic partial oxidation step.

[0010] EP 4495054 Al discloses autothermal cracking process including the provision of a gas heated reactor arranged in parallel or in series with an autothermal cracker, in which air is fed as the oxygen containing gas to the autothermal cracker.

[0011] Further prior art is found in the following patent literature: US2013 / 0266506 Al,

[0012] 03129-WOUS2005 / 0037244 Al, DE 2617089 Al, WO 2008 / 124625 A2, EP 0572778 A2, US 2009 / 0304574 Al and EP 3059206 Al.

[0013] SUMMARY

[0014] It would be desirable to be able to further reduce the risk of NOXproduction during the autothermal cracking process while at the same time increasing the capacity of the process and plant in terms of hydrogen production.

[0015] It would be desirable to reduce the carbon footprint compared to fired tubular crackers at large scales.

[0016] It would be desirable to increase the hydrogen production compared to a fired tubular cracker or an autothermal cracker, while at the same time providing a more energy efficient plant and with reduced carbon footprint.

[0017] It would be desirable to be able to achieve quick starting-up of an autothermal cracker without resorting to external hydrogen sources.

[0018] It would be desirable to reduce the oxygen content in the oxygen containing gas to the autothermal cracker while maintaining a desired equilibrium temperature in the product gas from the autothermal cracker of 800-1100°C or close to 800°C such as 780°C or such as 790°C.

[0019] It would be desirable to reduce the oxygen consumption in the autothermal cracker while at the same time increasing the hydrogen efficiency of the process or plant.

[0020] It would be desirable to provide a simpler construction and approach for protecting the burner of an autothermal cracker, while at the same time reducing the risk of any CO2reacting with NH3to form solids (carbonate, bicarbonate and carbamate) clogging equipment, along with reducing the oxygen consumption in the autothermal cracker as well as increasing the hydrogen efficiency of the process or plant.

[0021] The present invention is set out to solve one or more of the above problems.

[0022] For the purposes of the present application:

[0023] O312 -\NOThe term "invention" or "present invention" may be used interchangeably with "application" or "present application", respectively.

[0024] The term "first aspect" or "first aspect of the invention" means embodiments related to the method (process). The term "second aspect" or "second aspect of the invention" means embodiments related to the system (process plant i.e. plant).

[0025] The use of the term "process / plant" means the method (process) or system (plant) according to the invention.

[0026] It is understood that a given step may comprise one or more sub-steps. It is also understood that a given step is conducted in a corresponding unit or combination of units.

[0027] It is understood that the term "arranged to" or similar terminology connected to the verb "arrange" may be used interchangeably with the term "configured to" or similar terminology connected to the verb "configure".

[0028] The term "suitably" means "optionally", i.e. an optional embodiment.

[0029] The term "at least a part" or "at least a portion" of a given stream means a portion of the stream or the entire stream. The interpretation applies also to physical items, such as a conduit carrying a given process stream.

[0030] The term "and / or" means in connection with a given embodiment any of three options. The term "and / or" may be used interchangeably with the term "at least one of" the three associated options. Same interpretation applies in connection with the term "at least one" where there more than three associated options. For instance, the term "at least one of A, B, C" means: A or B or C, or combinations thereof e.g. A and B, A and C, A and B and C, B and C, B and D, etc.

[0031] The use of the article "a" or "an" means at least one. It covers the singular and plural form. The term "ammonia" shall be understood broadly and includes the ammonia feed stream. The term "ammonia feed stream" is to be understood as a "gaseous ammonia feed stream", and which is for instance derived, i.e. obtained, from liquid ammonia such as liquid ammonia imported from storage or from battery limits (outside battery limits).

[0032] The use of mole% in gas streams may be used interchangeably with vol.%.

[0033] It is understood that for gaseous streams, concentrations are preferably given in mole% or vol.%, while for liquid streams are preferably given in wt.%.

[0034] Unless otherwise stated, when only % are presented, it is meant mole%.

[0035] The term "comprising" encompass the use of the term "consisting of", i.e. "comprising only". The term "inerts" refers to the elements N2and / or Ar. Preferably N2represents at least 90 vol.% or at least 95 vol.% of the inerts. For instance, in the oxygen containing gas the inerts are 15 vol.% N2and 0.5 vol.% Ar.

[0036] The term "hydrogen efficiency" (H2-eff.) is defined by:

[0037] molar (vol. basis) flow rate of H2-product / (1.5 x ammonia feed flow rate (vol. basis);

[0038] 03129-WOsince for 1 mole of ammonia there is 1.5 mole of H2-product, according to the NH3cracking reaction 2 NH3= N2+ 3 H2. The ammonia feed flow is the liquid ammonia feed from outside battery limits, i.e. the liquid ammonia entering the process / plant. For instance, the byproduct has >99.97 mole% H2i.e. a H2-purity of > 99.97 mole%. For instance, the ammonia feed flow is commercial grade anhydrous ammonia from outside battery limits having 99.5% ammonia and about 0.5% water.

[0039] Other definitions are provided in connection with one or more of the above or below embodiments.

[0040] In a first general embodiment according to a first aspect (process) of the invention there is provided a process for the production of a product gas containing nitrogen and hydrogen from ammonia, the process comprising the steps of:

[0041] i) pre-cracking an ammonia feed stream to a pre-cracked process gas containing hydrogen, nitrogen, and ammonia by contact with a first ammonia cracking catalyst;

[0042] ii-1) non-catalytic partial oxidation of the pre-cracked process gas with an oxygen containing gas to a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia;

[0043] ii-2) cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a second ammonia cracking catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during at least the pre-cracking of the ammonia feed stream, thereby producing said product gas containing nitrogen and hydrogen;

[0044] iii) withdrawing the product gas;

[0045] - wherein the non-catalytic partial oxidation of step ii-1) and the cracking step of step ii-2) are performed in an autothermal cracking reactor (autothermal cracker) and the autothermal cracker comprises a burner arranged to receive the oxygen containing gas in step ii-1);

[0046] - wherein the oxygen containing gas comprises 30-99.9 mole% 02;

[0047] - wherein the ammonia feed stream in step i) is at least partly obtained from a liquid ammonia feed and the total amount of water (Nm3 / h) being supplied, preferably directly supplied, to the autothermal cracker in the pre-cracked process gas from step i) is lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage; - wherein the pre-cracking step i) is conducted in at least one of:

[0048] an adiabatic pre-cracking reactor (adiabatic pre-cracker) and

[0049] a convection type pre-cracking reactor (convection type pre-cracker) selected from at least one of: a convection heating pre-cracking reactor with bayonet tubes (convection heating pre-cracker with bayonet tubes) and a heat exchange pre-cracking reactor (heat exchange pre-cracker).

[0050] 03129-WOThereby, the need for actively adding steam to the autothermal cracker or to its burner, such as the need of directly and separately supplying steam i.e. actively adding steam to the burner, is avoided.

[0051] Preferably, the burner comprises a burner nozzle. The present invention thus enables not only a simpler process and construction for protecting the burner of an autothermal cracker, by virtue of not requiring active addition of steam to dilute the oxidant gas or active addition of steam to the burner, suitably to the burner nozzle of the burner to protect the burner nozzle from overheating, but also at the same time reducing the oxygen consumption in the autothermal cracker as well as increasing the hydrogen efficiency of the process or plant.

[0052] Suitably, the oxygen containing gas in step ii-1) comprises: 22-99.9 mole% O2. For instance, the lower limit of said range is any of: 23,, 24,, 25, 26, 27, 28,, 29 mole% O2. The values, including intermediate values, may be combined, for instance in ranges. The rest of the oxygen containing gas is inerts, in which the inerts comprise at least one of N2and Ar, preferably N2as the main (major) element inert, representing at least 90 vol.% or at least 95 vol.% of the inerts,

[0053] Suitably, the oxygen containing gas in step ii-1) comprises: 30-99.8 mole% O2. For instance, the lower limit of said range is any of: 35, 40, 45, 50, 55, 60, 65 mole% O2. The values, including intermediate values, may be combined, for instance in ranges. The rest of the oxygen containing gas is inerts, in which the inerts comprise at least one of N2and Ar, preferably N2, preferably N2as the main (major) element inert, representing at least 90 vol.% or at least 95 vol.% of the inerts,

[0054] In an embodiment, the oxygen containing gas in step ii-1) is: at least 70 mole% O2and no more than 30 mole% inerts, in which the inerts comprise at least one of N2and Ar; or at least 75 mole% O2and no more than 25 mole% inerts, in which the inerts comprise at least one of N2 and Ar; preferably, the oxygen containing gas in step ii-1) comprises 75-95 mole% O2and 5-25 mole% inerts; or 80-90 mole% O2and 10-20 mole% inerts.

[0055] Thereby, the oxygen and inert content are specifically tailored to use the inerts as diluent for the oxygen in the oxygen containing gas and protection of the burner, thus enabling increased burner safety, instead of e.g. diluting with steam in the oxygen containing gas.

[0056] The use of oxygen containing gas with a high O2-content, hence O2-rich, such as said 75-95

[0057] 03129-WOmole% O2instead of using air (21% O2) as the oxygen containing gas, avoids the risks associated with having to deal with any CO2being present in the air. In the present invention, CO2is advantageously removed from air during air enrichment, preferably in an air separation unit (ASU), as further explained in connection with another embodiment of the invention.

[0058] It is understood that the term "air enrichment" means enrichment in the oxygen content.

[0059] In an embodiment, the oxygen containing as in step ii-1) comprises at least one of: 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 mole% O2. The values, including intermediate values, for instance 76, 77, 78, 79 mole% O2, may be combined, for instance in ranges, such as 75-95 mole % O2. etc.

[0060] In an embodiment, the margin percentage is at least 10%, such as at least 15%, or such as at least 20%. For instance, the margin percentage is 10-20%, such as 15-20%. For instance, the margin percentage is at least one of: 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%. The values, including intermediate values may be combined, for instance in other ranges, such as 13-17% etc.

[0061] It is understood that there may be internal recirculation of streams in the process / plant which increases the water content inlet the autothermal cracker, by approach about 8%.

[0062] So, by way of example, as also more specifically shown in the Examples section, the water content in the pre-cracked process gas of step i) i.e. inlet the autothermal cracker is e.g. 1342 Nm3 / h, while the water content in the liquid ammonia feed from battery limits is e.g. 1244 Nm3 / h. Applying a margin percentage of 15% the maximum content of allowed water inlet the autothermal cracker becomes 1431 Nm3 / h (1244x1.15). So, the requirements defined are met (1342 < 1431 Nm3 / h water). Thereby, the use of directly and separately supplying steam to the burner is avoided.

[0063] Hence, alternatively or supplementary or complementary to the recited feature: "wherein the ammonia feed stream in step i) is at least partly obtained from a liquid ammonia feed and the total amount of water (Nm3 / h) being directly supplied to the autothermal cracker in the pre-cracked process gas from step i) is lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage", the following recital may be used: "wherein there is no separate steam addition for diluting the oxygen containing gas, or there is no

[0064] 03129-WOseparate steam addition for diluting the oxygen containing gas in step ii-1), or there is no separate steam addition to the burner".

[0065] Traditionally, based on experience with autothermal reformers in the production of synthesis gas, a skilled person would protect the burner of the autothermal reformer by diluting the oxidant containing gas, in particular oxygen e.g. containing oxygen at a high concentration, for instance about 99 vol.% or more O2, with some inerts and some steam. This provides safety in the burner design. In prior art disclosing the use of autothermal crackers, for instance EP 4495054 Al, steam is actively added separately to the burner as "moderator steam" to protect the burner nozzle from overheating. The moderator steam is e.g. concentrically introduced through the burner nozzle around the oxidant gas. In contrast thereto, the invention provides a simpler approach, by which there is the condition or requirement that the water inlet the autothermal cracker is maintained at a level below that of the amount of water in the liquid ammonia feed from battery limits plus a margin percentage, as recited. Also, in contrast to the above-mentioned prior art, in the present invention the oxygen in the oxidant containing gas is, in an embodiment, diluted with inerts, mostly N2, and no steam is added.

[0066] Ammonia cracking is produced industrially in fired tubular crackers. The size of these units is constrained by mechanical considerations. For very large capacities, multiple lines are installed, which is very costly. In addition, the carbon footprint not least associated with the CO2emitted in the flue gas from a fired tubular cracker becomes large. It is understood that in this context, supplementary fuels are used which contain carbon. If H2or NH3is used as fuel gas in the fired tubular cracker (fired cracker), the CO2footprint is the same. An advantage of autothermal cracking is that it does not require nor allows for C-containing supplementary fuels. The provision of pre-cracking step i) prior to steps ii-1) and ii-2), despite the penalty incurred in not least increased capital and operating expenditures (CAPEX and OPEX) in connection with the pre-cracking, enables further reducing the generation of NOx during at least the subsequent step ii-1), while at the same time at least increasing the capacity of the process / plant in terms of hydrogen production. The provision of pre-cracking step i) also enables reducing the O2-consumption in the autothermal cracker which is a major contributor to OPEX of the process / plant.

[0067] NOx compounds in the partially oxidized gas in step ii-1) are reduced by hydrogen already produced during the pre-cracking step i) with the first ammonia cracking catalyst. Further, the presence of hydrogen already in step ii-1), thus generated in-situ i.e. during the prior

[0068] 03129-WOpre-cracking operation of step i), provides a simple approach for reducing the autoignition temperature needed in step ii-1).

[0069] The autoignition temperature is reduced by up to 100°C, which enables autoignition of the ammonia at lower preheating temperature, thereby reducing the duty and associated fuel requirements for preheating the ammonia feed stream and / or pre-cracked process gas, for instance in a fired heater. This results also in lower CO2emissions or eliminating CO2-emissions in the flue gas from for instance a fired heater used for pre-heating streams while at the same time increasing the hydrogen production downstream, as the need of burning in e.g. the fired heater a hydrocarbon fuel gas such as natural gas and / or hydrogen produced in the process / plant is reduced. Furthermore, the presence of hydrogen already in step ii-1) increases the flammability during operation, thereby providing flame stability in the non-catalytic partial oxidation, since ammonia has a low flame speed which makes it difficult to burn.

[0070] The present invention not only enables better NOXcontrol while increasing hydrogen production capacity, but also favourable CAPEX in ammonia cracking plants of large capacity e.g. about 300000 Nm3 / h H2product or higher, together with reduced carbon footprint compared to fired tubular cracking at large scales or compared to an autothermal cracker without pre-cracking. Accordingly, in an embodiment, the process / plant is for producing at least 300000 Nm3 / h H2product, such as 300000-500000 Nm3 / h H2product.

[0071] For the purposes of the present application, the lower limit, 300000 Nm3 / h, is preferably within a -5% range, thus covering e.g. 285000 Nm3 / h H2product, or higher.

[0072] In an embodiment, the process further comprises:

[0073] - supplying an air feed stream to an air enrichment unit, preferably an air separation unit (ASU), for providing at least one of: said oxygen containing gas and a nitrogen gas.

[0074] Thereby, there is co-production of nitrogen, which may be sent to outside battery limits and sold (exported) as product. The power demand of a large ASU is quite large, so by preconverting some ammonia, the demand of oxygen is reduced. Hence, a process / plant without pre-conversion becomes much less competitive. The present invention prefers the use of an ASU for producing the oxygen containing gas to the autothermal cracker, rather than just using air, in particular compressed air, since CO2in the air is inherently removed in the ASU. There is no need to provide a separate upstream unit, such as a scrubber, for removing CO2in the air. CO2can react with NH3to form solids (carbonate, bicarbonate and carbamate) that

[0075] 03129-WOare corrosive and can clog equipment. It has been found that by utilizing air to the autothermal cracker, the clogging compounds formed by the reaction of CO2and NH3, require removal downstream, for instance in the ammonia recovery step, more specifically in a distillation column. While these compounds formed by the reaction of CO2and NH3can be removed via this distillation step, detailed knowledge of the thermodynamics of formation and decomposition of those compounds is necessary, thus constraining operating conditions, such as in turndown scenarios. While CO2-removal from the air can be envisaged upstream the autothermal cracker, as recited, such as by the provision of a scrubber / washing unit using a NaOH solution, a simpler and safer operation is ensured in the present invention by utilizing O2-rich, i.e. said oxygen containing gas comprising 30-99.9 mole% O2, such as at least 75 mole% O2and no more than 25 mole% inerts, instead of air.

[0076] Further, as it will also become apparent from one or more of below or above recited embodiments, the ASU enables high integration. Not only is the oxygen from the ASU being utilized in the autothermal cracker as oxygen containing gas, but also the nitrogen gas from the ASU can be used as a dilution gas to the oxygen containing gas to provide said 30-99.9 mole% O2, such as at least 75 mole% O2and no more than 25 mole% inerts, in which the inerts comprise at least one of N2and Ar; or as a separate addition of a N2-rich gas to the autothermal cracker, while the nitrogen not required for said dilution of the oxygen containing gas, and / or for said separate addition to the autothermal cracker, is suitably exported as product. Hence, the ASU acts as a unit for removing undesired CO2in the air, while at the same time providing the oxygen containing gas, i.e. O2-rich gas, and nitrogen used in the autothermal cracker; and / or for exporting nitrogen as product.

[0077] An ASU is well-known in the art. It is a unit where the oxygen content is increased by e.g. cryogenic distillation of air, in which air is cooled to very low temperatures so that the air can be liquefied and then separated into O2and N2and optionally also Ar based on boiling points.

[0078] In an embodiment, the oxygen containing gas is indirectly or directly supplied to the autothermal cracker.

[0079] In the context of the oxygen containing gas being indirectly supplied to the autothermal cracker:

[0080] In an embodiment, the oxygen containing gas is indirectly supplied to the autothermal cracker by combining an oxygen-rich gas (O2-rich gas) comprising above 95 mole% O2, such as at least 99 mole% O2, with a dilution gas comprising inerts, thereby producing the oxygen

[0081] 03129-WOcontaining gas comprising e.g. 75-95 mole% O2and 5-25 mole% inerts.

[0082] Accordingly, the oxygen containing gas is combined with a dilution gas comprising inerts, thus actively diluted, for producing the oxygen containing gas comprising for instance: 75-95 vol.% O2and 5-25 mole% inerts; or 80-90 vol.% O2and 10-20 vol.% inerts. The term "actively diluted" herein means by separate addition of a stream comprising inerts.

[0083] So, the oxygen containing gas to the autothermal cracker, i.e. inlet the autothermal cracker, is obtained after adding a dilution gas. The dilution gas is preferably a N2-rich gas stream, such as N2-rich gas stream comprising at least 90 mole% N2, preferably with no significant content of hydrogen, for safety reasons.

[0084] In an embodiment, the dilution gas is at least a portion of a nitrogen gas from the oxygen enrichment unit, preferably said ASU; preferably the nitrogen gas comprising at least 99 mole% N2, e.g. at least 99.9 mole% N2.

[0085] The nitrogen not required in the autothermal cracker is suitably exported as product.

[0086] The oxygen containing gas may comprise at least 99.5 mole% O2.

[0087] For instance, the oxygen containing gas is at least a portion of an oxygen stream from a unit separating atmospheric air into O2and N2, e.g. an ASU. Such an oxygen containing gas stream is O2-rich, for instance comprising at least 99.5 mole% O2, e.g. at least 99.9 mole% O2, the rest being inerts, more specifically N2and Ar.

[0088] In the context of the oxygen containing gas being directly supplied to the autothermal cracker:

[0089] For instance, there is no addition of a dilution gas to the oxygen containing gas to the autothermal cracker. The oxygen containing gas is thus directly supplied to the autothermal cracker i.e. inlet the autothermal cracker, and may already comprise the required content of oxygen and inerts, namely for instance at least 75 mole% O2and no more than 25 mole% inerts, such as about 85 mole% O2and about 15.0 mole% N2.

[0090] For instance, there is no addition of a fuel gas such as externally sourced natural gas to support the combustion.

[0091] Regardless of whether the oxygen containing gas is directly or indirectly supplied to the autothermal cracker:

[0092] 03129-WOIn an embodiment, the autothermal cracker has only two inlets and only one outlet, namely: the pre-cracked process gas inlet, i.e. a conduit carrying the pre-cracked process gas inlet, the oxygen containing gas inlet, i.e. a conduit carrying the oxygen containing gas, and the product gas outlet, i.e. a conduit carrying the product gas being withdrawn from the autothermal cracker.

[0093] For the purposes of the present application, the term "directly supplied" or similar terminology means that there are no intermediate process units changing the composition of the associated process stream or conduit carrying the associated process stream, such as a process gas or product gas. The process stream is in direct fluid communication with the unit receiving the process stream. Conversely, the term "indirectly supplied" or similar means that that there are intermediate process units changing the composition of the associated process stream or conduit carrying the associated process stream, such as a process gas or product gas. The process stream is in indirect fluid communication with the unit receiving the process stream.

[0094] In an embodiment, there is a separate addition of a N2-rich gas stream to the autothermal cracker, such as separate addition of a N2-rich gas stream comprising at least 90 mole% N2, preferably with no significant content of hydrogen, for safety reasons. Preferably, at least a portion of said nitrogen gas is from the air enrichment unit, preferably said ASU. Such a nitrogen gas is at least 99 mole% N2, e.g. at least 99.9 mole% N2.

[0095] This enables burner protection in the autothermal cracker while at the same time integrating the nitrogen stream from the air enrichment unit, preferably the ASU. The nitrogen not required in the autothermal cracker is suitably exported as product.

[0096] Accordingly, in an embodiment, the autothermal cracker has only three inlets and only one outlet, namely: the pre-cracked process gas inlet, i.e. a conduit carrying the pre-cracked process gas inlet, the oxygen containing gas inlet, i.e. a conduit carrying the oxygen containing gas, the N2-rich gas inlet, i.e. a conduit carrying the N2-rich gas, and the product gas outlet, i.e. a conduit carrying the product gas being withdrawn from the autothermal cracker.

[0097] It is understood that in the autothermal cracker, herein also referred to as ATC, the non-catalytic partial oxidation of ammonia is performed by means of a burner by burning the ammonia in gaseous form with oxygen. The burner is arranged at the inlet side of the reactor

[0098] 03129-WOvessel comprising a combustion chamber i.e. a non-catalytic partial oxidation zone and a downstream catalyst bed i.e. a catalytic zone downstream, similar to the known autothermal cracker illustrated in Fig. 2 of said applicant's WO 2019 / 038251 Al. The non-catalytic partial oxidation step and the cracking step in a catalytic zone are performed within a single reactor vessel as said ATC, the catalytic zone being arranged downstream the non-catalytic partial oxidation zone, and in which both zones are in direct fluid communication.

[0099] Thereby the reaction heat from the exothermic partial oxidation is preserved for carrying out the endothermic ammonia cracking reaction.

[0100] In an embodiment, step ii-2) further comprises simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during cracking of the process gas by contact of the pre-cracked process gas with the second ammonia cracking catalyst.

[0101] Hence, NOXin the partially oxidized gas in step ii-1) are reduced by hydrogen already produced during the pre-cracking step i) with the first ammonia cracking catalyst, along with hydrogen produced by the downstream cracking in step ii-2) by contact with the second ammonia cracking catalyst. This further reduces the NOXgenerated in step ii-1) to non-detectable limits, thus up to 100% NOXreduction, thereby eliminating the need of providing a further downstream catalytic zone comprising a NOXreducing or a separate downstream catalytic unit comprising a NOXreducing catalyst e.g. downstream an autothermal cracker in which steps ii-1) and ii-2) are conducted, for eliminating any NOXleft in the product gas of step iii).

[0102] Accordingly, in an embodiment, in step iii) the product gas is directly withdrawn from step ii-2).

[0103] As recited, the term "directly" means that there are no intermediate units changing the composition of product gas produced in step ii-2) within the ATC.

[0104] The non-catalytic partial oxidation of step ii-1) and the cracking step of step ii-2) are performed in the autothermal cracker, i.e. ATC.

[0105] The ATC thus comprises a non-catalytic partial oxidation zone for conducting step ii-1) and a downstream catalytic zone comprising the second ammonia cracking catalyst for conducting step ii-2). As mentioned, the autothermal cracker is as shown in Fig. 2 of said applicant's WO

[0106] 03129-WO2019 / 038251 Al. It is understood that the so-called "combustion chamber" of Fig. 2 WO 2019 / 038251 Al corresponds to the non-catalytic partial oxidation zone of the present application.

[0107] The present invention, by virtue of the pre-cracking further enables achieving quick starting-up of the autothermal cracker without resorting to external hydrogen sources.

[0108] In an embodiment, the content of hydrogen in the pre-cracked process gas is at least 5-25 vol.% H2, such as at least 10-20 vol.% H2, or at least 20 vol.% H2, for instance 20-25 vol.% H2.

[0109] Ammonia has a low flame speed which makes it difficult to burn. The presence of H2, such as the at least 10-20 vol.% H2, or at least 20 vol.% H2, facilitates the combustion.

[0110] In an embodiment, the content of hydrogen in the product gas exiting the autothermal cracker is at least 40 vol.% H2, such as at least 50 vol.% H2, or such as at least 60 vol.% H2, for instance 60-70 vol. % H2.

[0111] The presence of the H2in the pre-cracked gas facilitates the combustion in step ii-1), thereby also reducing or eliminating the need of recycling hydrogen produced in the process / plant. The hydrogen being produced becomes part of the H2-product downstream, thus increasing process / plant capacity.

[0112] In an embodiment,

[0113] - the first ammonia cracking catalyst comprises a metal or a metal alloy selected from at least one of: iron (Fe), cobalt (Co), ruthenium (Ru), nickel (Ni), preferably Fe and Co as the only metals, or Fe and Ni as the only metals; and / or

[0114] - the second ammonia cracking catalyst is a nickel containing catalyst, preferably nickel as the only metal

[0115] - optionally:

[0116] wherein the second ammonia cracking catalyst is free of a precious metal, the precious metal being at least one of: gold (Au), iridium (Ir), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), silver (Ag); such as the second ammonia cracking catalyst being free of any of Pt and Pd; or

[0117] wherein there is no third catalyst arranged downstream the second ammonia cracking catalyst, and comprising a precious metal, the precious metal being at least one of: gold (Au), iridium (Ir), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), silver (Ag).

[0118] 03129-WOFor instance, the first ammonia cracking catalyst comprises a combination of 20-50 wt% Fe, 20-50 wt% Co and 20-50 wt% alumina, optionally promoted with an alkali metal oxide, and or oxides of Ca, Si, Al or combinations hereof. The Fe-Co catalyst may be bimetallic or an alloy. The Fe-Co catalyst exhibits a significantly higher activity than Ni-containing i.e. Ni-based catalysts.

[0119] For instance, the first ammonia cracking catalyst comprises 20-50 wt% Fe, 20-50 wt% Co and 20-50 wt% alumina, optionally promoted with an alkali metal oxide, a lanthanide group metal oxide, and / or oxides of Ca, Si, Al or combinations thereof.

[0120] The provision of the above catalysts enables operation of the pre-cracking step i) in the temperature range 300-700°C such as 500-650°C. Preferably, where the pre-cracking step i) is conducted in a heat exchange pre-cracking reactor (heat exchange pre-cracker) arranged in series with the autothermal cracker, the pre-cracked process gas temperature exiting the heat exchange pre-cracker is not higher than 520°C, for instance 480-515°C. Preferably, the pre-cracked process gas is directly supplied to the autothermal cracker, i.e. there are no process units or steps changing its composition before entering the autothermal cracker. It is understood that in the present context, the pre-cracked process gas enters via an individual conduit, thus a separate conduit, while a conduit carrying the oxygen containing gas is separately introduced to the autothermal cracker, thus as a separate conduit.

[0121] The second ammonia cracking catalyst is a nickel containing catalyst. Hence, the second ammonia cracking catalyst comprises nickel; the nickel content being 10-60 wt% Ni, such as 10-20 wt% Ni or 10-30 wt% Ni, or 20-60 wt% Ni, with balance being of any oxides of Al, Ca, Mg or combinations thereof, optionally promoted with a lanthanide group metal oxide, such as La2O3. Preferably, as recited, Ni is the only metal, i.e. active metal. It is understood that the other elements recited, such as Al, Ca, Mg, La2O3 are not regarded as active metals, but e.g. as a promoter. For the purposes of the present application, the active metal(s) is(are), as recited, a metal or a metal alloy selected from at least one of: iron (Fe), cobalt (Co), ruthenium (Ru), nickel (Ni).

[0122] For instance, the content of nickel in the second ammonia cracking catalyst is 10-20 wt%, preferably as a monometallic nickel catalyst.

[0123] For instance, the first and second ammonia cracking catalyst are provided as a monometallic nickel catalyst.

[0124] 03129-WOIt is understood that that term "lanthanide" refers to any of the fifteen elements from La to Lu in the periodic table of elements. Lanthanum (La), as used herein, is also a lanthanide.

[0125] It is understood that the wt% are with respect to the total weight of catalyst.

[0126] It is understood that the total wt% sums up to 100%.

[0127] This enables flexibility in the selection of catalysts. For instance, an iron-based catalyst alloyed with Co, may be used as the first ammonia cracking catalyst, which is less expensive than a nickel containing catalyst. An iron-based catalyst may also be together with Ni and used as the first ammonia cracking catalyst. It has been found that iron alone is not very suitable for ammonia cracking, as it nitrides and deactivates, yet advantageously it can be utilized if alloyed with Ni or Co. A nickel containing catalyst is advantageously used as the second ammonia cracking catalyst.

[0128] The invention enables that the concentration of NOXin the product gas exiting the autothermal cracker is negligible. There is no need for adding expensive precious metal(s) in the second ammonia cracking catalyst for reducing the NOx content to negligible content. There is no need to incorporate a third catalyst arranged downstream the second ammonia cracking catalyst and comprising a precious metal.

[0129] The pre-cracking step i) is conducted in at least one of:

[0130] - an adiabatic pre-cracking reactor (adiabatic pre-cracker);

[0131] - a convection type pre-cracking reactor (convection type pre-cracker) selected from at least one of: a convection heating pre-cracking reactor with bayonet tubes (convection heating pre-cracker with bayonet tubes, e.g. HTCR type) and a heat exchange pre-cracking reactor (heat exchange pre-cracker, herein also referred to as HTEC).

[0132] These reactors for conducting the pre-cracking step i) are well-known in the art. These may also be referred to as "pre-converter(s)".

[0133] For instance, adiabatic pre-crackers are disclosed in said applicant's WO 2024246097.

[0134] For the purposes of the present application, a convection type pre-cracker may be used interchangeably with the term "heat exchange pre-cracker". A heat exchange pre-cracker according to the present application is constructed as a heat exchange reformer (HER). A specific HER is the so-called convection reformer HTCR (Haldor TOPSOE™ Convection

[0135] 03129-WOReformer™) utilizing bayonet tubes as described in e.g. EP 0535505. The convection heating pre-cracker with bayonet tubes corresponds to the HTCR. The HTCR is a vertical, refractory-lined vessel with a bundle of bayonet tubes inside. Each bayonet tube is surrounded by another tube that guides the hot flue gas around the bundle of tubes containing the feedstock. Below the vertical section there is an adjacent combustion chamber, such as a horizontal combustion chamber containing one or more burners, typically utilizing a hydrocarbon fuel gas such as natural gas, as fuel. In the present application, off-gas comprising hydrogen may be advantageously supplied as fuel thereto, thereby reducing the natural gas consumption and associated CO2-emissions in the flue gas. The heat is transferred to the ammonia feed by convection, resulting in more effective exploitation of the thermal inputs, lower fuel consumption and no steam export.

[0136] An arrangement of HER (heat exchange reformer) and an autothermal reformer (ATR) in series is described in WO 2012 / 084135. In the present application, the heat exchange precracker arranged in series with the ATC may also be referred to as "HTEC-s with ATC", or "HTEC-s + ATC".

[0137] An arrangement of HER and ATR in parallel is described in WO 2015 / 128456. In the present application, the heat exchange pre-cracker arranged in series with the ATC may also be referred to as "HTEC-p with ATC2, or "HTEC-p + ATC".

[0138] Suitably, as recited above, the pre-cracking step i) is conducted in the temperature range 300-700°C. For instance, the process comprises the provision of a single adiabatic pre-cracker operating in the range 500-700°C, or 500-650°C. For instance, the process comprises the provision of two ammonia pre-crackers operating in the range 500-700°C, such as two adiabatic pre-crackers operating in the range 500-650°C. For instance, an adiabatic pre-cracker operates in the temperature rage 350-600°C, for instance 350-500°C, 350-550°C or 400-550°C. For instance, the inlet temperature may be 500-550°C, and the outlet temperature may be 400-450°C.

[0139] In an embodiment, the heat exchange pre-cracker is arranged in series or in parallel with the autothermal cracker (HTEC-s or HTEC-p), preferably arranged in series with the autothermal cracker (HTEC-s with ATC).

[0140] In a preferred embodiment, the pre-cracking step i) is conducted in:

[0141] a heat exchange pre-cracking reactor (heat exchange pre-cracker, HTEC) arranged in series with the autothermal cracker. In short: a HTEC-s with ATC.

[0142] 03129-WOFor the heat exchange pre-cracker being arranged in series with the autothermal cracker, the product gas withdrawn from the autothermal cracker is supplied to the heat exchange precracker for providing heat thereto and thereby cooling the product gas.

[0143] The provision of preferably the heat exchange pre-cracker arranged in series with the autothermal cracker, reduces oxygen consumption whereby apart from improving energy efficiency, the ammonia to hydrogen efficiency (H2-efficiency) is improved. This improvement is also achievable with respect to an embodiment in which the pre-cracking step is conducted in an adiabatic pre-cracker. The oxygen consumption directly impacts the hydrogen efficiency. There is an associated reduction in oxygen consumption and power savings in the air enrichment unit, e.g. air separation unit (ASU). The ASU is the largest consumer of electricity in the process / plant. For the purposes of the present application, a value of 0.6 kW per Nm3 / h oxygen used is provided as a first estimate of the energy demand. Hence, the invention enables also a lower energy demand, i.e. energy consumption, and thereby higher energy efficiency.

[0144] The use of compressed air to the ATC, instead of an oxygen containing gas being O2-rich as in the present application, conveys the risk, as recited, that CO2can react with NH3to form solids (carbonate, bicarbonate and carbamate) that are corrosive and can clog equipment, thereby complicating the operation of the process / plant.

[0145] In an embodiment, the process further comprises electrolysis of a water or steam feedstock, thereby producing electrolysis-oxygen and electrolysis-hydrogen, and providing at least a portion of the electrolysis-oxygen containing gas as at least a portion of the oxygen in the oxygen containing gas.

[0146] Where or when the process / plant has access to e.g. renewable electricity or readably available electricity, such as from a thermonuclear source, the electrolysis is advantageously integrated in the process / plant, thereby reducing the size of the air enrichment unit, as electrolysis-oxygen can be used to at least supplement the oxygen produced in the air enrichment unit. The electrolysis-hydrogen may also be integrated with the produced hydrogen from a downstream product adjustment unit or upstream a product adjustment unit, e.g. a pressure swing adsorption unit (PSA unit). This enables also flexibility where the nitrogen gas from the air enrichment unit cannot be exported or where such use as product for export is limited. A smaller air enrichment unit results in a smaller nitrogen gas stream which may be adapted in connection with the ATC as explained earlier, with less concerns

[0147] 03129-WOabout producing excess nitrogen.

[0148] The design and thus provision of a feed / effluent heat exchanger at the outlet temperature of the autothermal cracker is highly complicated. In an embodiment, the temperature in the product gas withdrawn in step iii) is 800-1100°C, for instance 800-850°C, or for instance 780-850°C, which is advantageous as the ammonia slip in the autothermal cracker is reduced. The embodiment in which the heat exchange pre-cracker is arranged in series with the autothermal cracker enables a solution with no-steam production by which a feed / effluent heat exchanger and a pre-converter are combined as a single heat exchange pre-cracker.

[0149] In an embodiment, the non-catalytic partial oxidation of step ii-1) is performed by burning the pre-cracked gas in said burner with under-stoichiometric amounts of oxygen gas, wherein the content of oxygen in the oxygen containing gas is varied corresponding to a lambdavalue (A) between 0.18 and 0.30, or a lambda-value (A) between 0.10 and 0.20, in which A is the ratio between the actual oxygen feed flow and that required for full stoichiometric combustion of the ammonia into nitrogen and water.

[0150] The presence of hydrogen already generated in the pre-cracking step i) further enables operation at the same or lower lambda values than e.g. applicant's WO 2019 / 038251 Al, such as between 0.10 and 0.20, thus at significant sub-stoichiometric conditions (A =1 means stoichiometric conditions). This further reduces the NOXgeneration in step ii-1), more specifically in the burner arranged in the non-partial partial catalytic zone on the autothermal cracker by virtue of a lower flame temperature, while at the same time reducing the oxygen requirement. Oxygen is expensive and may be sourced from the air separation unit (ASU) and / or from water / steam electrolysis, as already recited. The operation with lower lambda values enables therefore e.g. a smaller ASU, thus lower capital expenditures (CAPEX) and associated operating expenditures (OPEX), e.g. power / electricity demand, thus reduced energy consumption. Furthermore, the need to provide a downstream catalytic unit dedicated to NOXremoval, such as an expensive precious metal such as Pt-based catalyst, is further eliminated.

[0151] In an embodiment, the product gas further contains uncracked ammonia and the process further comprises:

[0152] iv) supplying, preferably directly supplying, the product gas to a separating step, in which the separating step comprises separating the uncracked ammonia in the product gas by a water wash, thereby providing a separated aqueous stream comprising ammonia and a water-depleted product gas;

[0153] 03129-WOv-1) supplying, preferably directly supplying, the separated aqueous stream comprising ammonia to an ammonia recovery step, such as distillation, thereby providing a recovered ammonia stream preferably comprising at least 90 vol.% NH3, a light off-gas stream preferably comprising at least 20 vol.% H2, and a stripped process condensate stream i.e. a water stream;

[0154] v-2) supplying, preferably directly supplying, at least a portion of the recovered ammonia stream to at least one of:

[0155] the pre-cracking step i), preferably to the ammonia feed stream in the pre-cracking step i); the cracking step ii-1), preferably to the pre-cracked process gas in step ii-1);

[0156] v-3) optionally: supplying, preferably directly supplying, at least a portion of the stripped process condensate stream to said water wash in step iv).

[0157] Preferably, in step v-1) the ammonia recovery step, such as distillation, is only carried out in the separated aqueous stream comprising ammonia. In other words, the only feed stream to the ammonia recovery step is the separated aqueous stream comprising ammonia. This enables also a simpler distillation system.

[0158] As recited earlier, it is understood that the term "directly supplying" in step iv) means that there are no intermediate units changing the composition of the product gas up to the separating step, or in step v-1) changing the composition of the separated aqueous stream comprising ammonia up to the ammonia recovery step. The same interpretation applies for steps v-2) and v-3).

[0159] Thereby, there is high integration of process streams as the recovered ammonia stream is rich in ammonia, e.g. at least 95 vol.% NH3, thus making it suitable for conversion in step i) and ii). The stripped process condensate i.e. the water stream, is suitable utilized as wash water in the water wash step iv). The light off-gas stream, preferably where step v-1) is distillation, is suitably withdrawn as the overhead gas stream of an ammonia recovery separator arranged in an overhead section of the ammonia recovery distillation column, and has a significant hydrogen concentration, e.g. 30 vol.% or higher, apart from NH3, which makes it suitable for e.g. providing clean burning in for instance a fired heater for preheating ammonia feed streams, i.e. with low or no CO2-emissions.

[0160] In an embodiment, the process further comprises:

[0161] vi) adjusting the hydrogen to nitrogen mole ratio of the product gas or adjusting the hydrogen to nitrogen mole ratio of the water-depleted product gas in a product gas adjustment unit, the product gas adjustment unit being at least one of: a pressure swing

[0162] 03129-WOadsorption (PSA) unit and a membrane unit, thereby producing a hydrogen product and a product gas adjustment unit off-gas stream.

[0163] The term "at least one of a PSA and a membrane unit" is understood as: PSA and / or membrane unit. Hence: in an embodiment the product adjustment unit is a PSA; in an embodiment the product adjustment unit is a membrane unit; in an embodiment the product adjustment unit is a PSA and membrane unit.

[0164] In an embodiment, the product adjustment unit is a membrane unit, preferably a Pd-based membrane unit, a double-stage PSA unit, or a single PSA-unit arranged in series with the membrane unit. The skilled person is well-aware of any of these units and configurations and how to implement them without undue burden.

[0165] The term "product gas adjustment unit" may be used interchangeably with the term "hydrogen recovery unit" or "hydrogen purification unit" and is for instance: a) a single-stage PSA unit, b) a double-stage PSA unit, or c) a single-PSA unit and a membrane, or d) a membrane unit. Embodiments b) and c) in particular, increase the H2efficiency, minimizing the amount of hydrogen in the product gas adjustment unit off-gas.

[0166] PSA units and membrane units, such as Pd-based membrane units are well-known in the art. In an embodiment, the membrane unit is for instance a hollow fiber membrane comprising one or more modules, such as membrane as disclosed in e.g. WO 2024121590 Al.

[0167] To avoid losing H2in the product adjustment unit off-gas stream and maintain high integration of process streams in the process / plant, this off-gas stream is advantageously used as fuel, optionally along with the light off-gas from ammonia recovery, in a fired heater to preheat ammonia feed or process gas or to produce steam thus in an auxiliary boiler (steam superheater); or in the combustion chamber of the convection heating pre-cracking reactor with bayonet tubes.

[0168] Accordingly, in an embodiment, the process further comprises:

[0169] - combining at least a portion of the light off-gas stream of step v-1) with at least a portion of the product gas adjustment unit off-gas stream of step vi) into a combined off-gas stream comprising H2and N2;

[0170] - supplying at least a portion of the product gas adjustment unit off-gas of step vi) or at least a portion of the combined off-gas stream comprising H2and N2, as fuel gas to at least one of: a fired heater for producing heat and pre-heating the ammonia feed gas, an auxiliary boiler

[0171] 03129-WO(steam superheater) for producing steam, and a combustion chamber (combustion section) of the convection heating pre-cracker with bayonet tubes, e.g. HTCR type.

[0172] High integration is thereby achieved while reducing the requirement of externally sourcing a hydrocarbon fuel gas such as natural gas, for the burning in any of the fired heater, auxiliary boiler and the burner in the combustion section of the convection heating pre-cracker. The associated CO2-emissions in the flue gas generated from these units is significantly reduced, thereby reducing the carbon footprint of the plant. Further, the need for utilizing hydrogen product for the burning is also reduced, thereby increasing the H2-capacity of the process / plant.

[0173] In an embodiment, as recited, the pre-cracking step i) is conducted in a heat exchange pre-cracker arranged in series with the autothermal cracker (HTEC-s with ATC) and the process further comprises:

[0174] - supplying, preferably directly supplying, the product gas withdrawn from the autothermal cracker to the heat exchange pre-cracker for providing heat thereto and thereby cooling the product gas.

[0175] As recited, the arrangement in series with the autothermal cracker enables a solution with no-steam production by which a feed / effluent heat exchanger and a pre-converter are combined in a single heat exchange pre-cracker.

[0176] Further, as also recited, a main effect of adding an additional pre-cracker is further reduced oxygen consumption whereby ammonia to hydrogen efficiency is improved. The oxygen consumption is directly impacting the hydrogen efficiency.

[0177] In an embodiment, the pre-cracking step i) is conducted in an adiabatic pre-cracker, and the process further comprises:

[0178] - recovering heat from the product gas withdrawn from the autothermal cracker in at least one of a steam superheater and a waste heat boiler (WHB), under the production of steam; - supplying a portion of said steam as export steam, and / or supplying at least a portion of said steam, such as a portion of said steam, to a solid oxide electrolysis (SOE) unit thereby producing a SOE-unit oxygen stream and additional hydrogen;

[0179] - supplying at least a portion of the SOE-unit oxygen stream to step ii-1), preferably as part of the oxygen containing gas, and / or supplying at least a portion of said steam

[0180] to a steam turbine for producing electricity.

[0181] 03129-WOThis a solution with steam production. Rather than a heat exchange pre-cracker arranged in parallel or in series with the autothermal cracker, an adiabatic pre-cracker is arranged upstream the autothermal cracker. The WHB is located immediately downstream the autothermal cracker. Steam production allows the autothermal cracker to operate at higher temperatures (above 800°C), which decreases the ammonia slip in the autothermal cracker.

[0182] There are, as mentioned, a number of mechanical and material aspects that make the design of a feed / effluent exchanger difficult at temperatures above 800°C. which the present application addresses.

[0183] The H2O produced by combustion in the autothermal cracker is a plant effluent, either as process condensate or as steam. Part of the invention, according to a specific embodiment, is therefore sending steam to a SOE-unit to obtain more hydrogen and oxygen as byproduct. The O2can be recycled as oxidant to the autothermal cracker.

[0184] While in a fired-tubular cracker the water formed in the combustion is emitted with the flue gas, in a plant with an autothermal cracker the water ends up as stripped process condensate. While it can be sent to battery limits, preferably, it is used in the heat integration to produce steam. Steam can be exported, used to produce electricity, or sent to the SOE-unit to increase the hydrogen recovery.

[0185] Because combustion takes place in the presence of the process gas, a challenge associated with the autothermal process is that the reactor effluent contains a significant amount of H2O (5-15 vol.%). Preheating of the process gas and the oxidant stream is beneficial to minimize the firing duty, thereby the amount of water produced. For the same reason O2rich streams are preferred over air, as heating of the associated N2is avoided. An additional benefit of using of oxygen is that the equipment becomes more compact; an air separation unit (ASU) is suitably provided for producing the oxygen. Accordingly, in an embodiment, as recited, the process further comprises: supplying an air feed stream to an air separation unit (ASU) for providing said oxygen containing gas.

[0186] Where a SOE-unit is also arranged in the process or plant, this provides in particular synergy with the SOE-unit which increases the H2production while reducing the oxygen consumption to the ASU.

[0187] As recited, in an embodiment, the process further comprises:

[0188] - supplying an air feed stream to an air separation unit (ASU) for providing: said oxygen

[0189] 03129-WOcontaining gas and further a nitrogen gas.

[0190] Thereby, regardless of the provision of SOE-unit or not, there is co-production of nitrogen, which may be sent to outside battery limits and sold as product.

[0191] In an embodiment, the heat exchange pre-cracker is arranged in series with the autothermal cracker and further a pre-cracking reactor, preferably an adiabatic pre-cracker, is arranged upstream said heat exchange pre-cracker arranged in series with the autothermal cracker.

[0192] Thereby, material demands on the heat exchange pre-cracker may be lessened because the nitriding potential of the gas is decreased. The term "nitriding potential" refers to the thermodynamic tendency of a gas mixture to form nitrides on the surface of metals, and it may be expressed in terms of the ratio of partial pressures of nitrogen to hydrogen in the gas to the heat exchange pre-cracker. The nitriding potential indicates how likely it is for nitrogen to react with a metal surface to form nitrides, which can affect the properties of the materials in the heat exchange pre-cracker, such as hardness, wear resistance, and corrosion resistance. Controlling the nitriding potential enables to mitigate corrosion issues. Nitrides can form protective layers that reduce the susceptibility of the materials to corrosion.

[0193] By adding an additional pre-cracker there is a further reduction in oxygen consumption in the ATC, whereby the ammonia to hydrogen efficiency is improved. Again, the oxygen consumption is directly impacting the hydrogen efficiency.

[0194] Preferably, there is no additional pre-cracking reactor such as an adiabatic pre-cracker arranged upstream the heat exchange pre-cracker arranged in series with the autothermal cracker. This provides more simplicity in the process and plant, while at the same time reducing OPEX and CAPEX.

[0195] In an embodiment, the process further comprises:

[0196] - combining at least a portion of the light off-gas stream of step v-1) and / or at least a portion of the product adjustment unit off-gas stream of step vi) with combustion air, thereby producing a catalytic oxidation unit (CATOX) feed gas;

[0197] - supplying the CATOX feed gas to a CATOX unit, thereby producing a CATOX flue gas, preferably the CATOX flue gas having a temperature of 200-650°C, such as about 600°C; - preheating at least one of: the oxygen containing gas in step ii-1), the ammonia feed stream in step i), and optionally the CATOX feed gas,

[0198] with at least a portion of the CATOX flue gas.

[0199] 03129-WOThe term "catalytic oxidation" (CATOX), as is well known in the art, means the oxidation of combustible compounds in a gas stream, such compounds being at least one of: H2, MeOH, CH4, and CO, the gas stream also comprising inerts e.g. Ar, over a catalyst in the presence of oxygen.

[0200] The catalyst(s) in the CATOX step can be selected from tungsten, vanadium, molybdenum, platinum and palladium in metallic and / or in metal oxide form supported on a carrier; or from vanadium, tungsten, chromium, copper, manganese, molybdenum, platinum, palladium, rhodium or ruthenium in metallic and / or metal oxide form supported on a carrier selected from alumina, titania, silica and ceria and combinations thereof.

[0201] After delivering heat to the oxygen containing gas in step ii-1) and to the ammonia feed stream in step i), the CATOX flue gas may further deliver heat to the CATOX feed gas. The thus cooled CATOX flue gas may be withdrawn and directed to outside battery limits as a flue gas sent to ambient air or stack.

[0202] The heat integration of the CATOX unit arranged downstream the product adjustment unit enables less oxygen consumption, thus less oxygen burning, to reach the same required temperature in the autothermal cracker. There is an associated improvement in the energy efficiency of the process / plant.

[0203] Where the power demand is accounted for, the process or plant meets the demands for at least the European Market (H2to grid), giving hydrogen efficiencies > 78%.

[0204] In a second general embodiment according to the first aspect (process) of the invention, there is provided a process for the production of a product gas containing nitrogen and hydrogen from ammonia, the process comprising the steps of:

[0205] i) optionally: pre-cracking an ammonia feed stream to a pre-cracked process gas containing hydrogen, nitrogen, and ammonia by contact with a first ammonia cracking catalyst;

[0206] ii-1) non-catalytic partial oxidation of the ammonia feed stream and / or the optionally precracked process gas, with an oxygen containing gas to a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia;

[0207] ii-2) cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a second ammonia cracking catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a

[0208] 03129-WOportion of the hydrogen formed during cracking of the process gas and / or hydrogen formed during the pre-cracking of the ammonia feed stream,

[0209] thereby producing said product gas containing nitrogen and hydrogen;

[0210] iii) withdrawing the product gas;

[0211] - wherein the non-catalytic partial oxidation of step ii-1) and the cracking step of step ii-2) are performed in an autothermal cracking reactor (autothermal cracker) and the autothermal cracker comprises a burner arranged to receive the oxygen containing gas in step ii-1);

[0212] - wherein the oxygen containing gas in step ii-1) preferably comprises 30-99.9 mole% O2; - wherein the ammonia feed stream in step i) is at least partly obtained from a liquid ammonia feed and the total amount of water (Nm3 / h) being supplied, preferably directly supplied, to the autothermal cracker in the pre-cracked process gas from step i) is lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage; - wherein the optional pre-cracking step i) is conducted in at least one of:

[0213] an adiabatic pre-cracking reactor (adiabatic pre-cracker) and

[0214] a convection type pre-cracking reactor (convection type pre-cracker) selected from at least one of: a convection heating pre-cracking reactor with bayonet tubes (convection heating pre-cracker with bayonet tubes) and a heat exchange pre-cracking reactor (heat exchange pre-cracker).

[0215] In a third general embodiment according to the first aspect (process) of the invention, there is provided a process for the production of a product gas containing nitrogen and hydrogen from ammonia, the process comprising the steps of:

[0216] i) pre-cracking an ammonia feed stream to a pre-cracked process gas containing hydrogen, nitrogen, and ammonia by contact with a first ammonia cracking catalyst;

[0217] ii-1) non-catalytic partial oxidation of the pre-cracked process gas with an oxygen containing gas to a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia;

[0218] ii-2) cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a second ammonia cracking catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during at least the pre-cracking of the ammonia feed stream, thereby producing said product gas containing nitrogen and hydrogen;

[0219] iii) withdrawing the product gas;

[0220] preferably, wherein step ii-1) and ii-2) are in direct fluid communication;

[0221] - wherein the product gas further contains uncracked ammonia and the process further comprises:

[0222] 03129-WOiv) supplying, preferably directly supplying, the product gas to a separating step, in which the separating step comprises separating the uncracked ammonia in the product gas by a water wash, thereby providing a separated aqueous stream comprising ammonia and a water-depleted product gas;

[0223] v-1) supplying, preferably directly supplying, the separated aqueous stream comprising ammonia to an ammonia recovery step, such as distillation, thereby providing a recovered ammonia stream, a light off-gas stream and a stripped process condensate stream;

[0224] v-2) supplying, preferably directly supplying, at least a portion of the recovered ammonia stream to at least one of:

[0225] the pre-cracking step i), preferably to the ammonia feed stream in the pre-cracking step i), and

[0226] the cracking step ii-1), preferably to the pre-cracked process gas in step ii-1);

[0227] v-3) optionally: supplying, preferably directly supplying, at least a portion of the stripped process condensate stream to said water wash in step iv);

[0228] vi) adjusting the hydrogen to nitrogen mole ratio of the product gas or adjusting the hydrogen to nitrogen mole ratio of the water-depleted product gas in a product gas adjustment unit, the product gas adjustment unit being at least one of: a pressure swing adsorption (PSA) unit and a membrane unit, thereby producing a hydrogen product and a product gas adjustment unit off-gas stream.

[0229] In an embodiment of the third general embodiment, the process further comprises:

[0230] - combining at least a portion of the light off-gas stream of step v-1) and / or at least a portion of the product adjustment unit off-gas stream of step vi) with combustion air, thereby producing a catalytic oxidation unit (CATOX) feed gas;

[0231] - supplying the CATOX feed gas to a CATOX unit, thereby producing a CATOX flue gas, preferably the CATOX flue gas having a temperature of 200-650°C, such as about 600°C; - preheating at least one of: the oxygen containing gas in step ii-1), the ammonia feed stream in step i), and optionally the CATOX feed gas,

[0232] with at least a portion of the CATOX flue gas;

[0233] or

[0234] - combining at least a portion of the light off-gas stream of step v-1) and / or at least a portion of the product adjustment unit off-gas stream of step vi), optionally along with combustion air, thereby producing a fuel gas;

[0235] supplying at least a portion of the fuel gas to at least one of: a fired heater for producing heat and pre-heating the ammonia feed gas, an auxiliary boiler (steam superheater) for

[0236] 03129-WOproducing steam, and a combustion chamber of the convection heating pre-cracker with bayonet tubes, e.g. HTCR type.

[0237] In a fourth general embodiment according to the first aspect (process) of the invention, there is provided a process for the production of a product gas containing nitrogen and hydrogen from ammonia, the process comprising the steps of:

[0238] i) pre-cracking an ammonia feed stream to a pre-cracked process gas containing hydrogen, nitrogen, and ammonia by contact with a first ammonia cracking catalyst;

[0239] ii-1) non-catalytic partial oxidation of the pre-cracked process gas with an oxygen containing gas to a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia;

[0240] ii-2) cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a second ammonia cracking catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during at least the pre-cracking of the ammonia feed stream, thereby producing said product gas containing nitrogen and hydrogen;

[0241] iii) withdrawing the product gas;

[0242] wherein the product gas further contains uncracked ammonia and the process further comprises:

[0243] iv) supplying, preferably directly supplying, the product gas to a separating step, in which the separating step comprises separating the uncracked ammonia in the product gas by a water wash, thereby providing a separated aqueous stream comprising ammonia and a water-depleted product gas;

[0244] v-1) supplying, preferably directly supplying, the separated aqueous stream comprising ammonia to an ammonia recovery step, such as distillation, thereby providing a recovered ammonia stream, a light off-gas stream and a stripped process condensate stream;

[0245] v-2) supplying, preferably directly supplying, at least a portion of the recovered ammonia stream to at least one of:

[0246] the pre-cracking step i), preferably to the ammonia feed stream in the pre-cracking step i), and

[0247] the cracking step ii-1), preferably to the pre-cracked process gas in step ii-1);

[0248] v-3) optionally: supplying, preferably directly supplying, at least a portion of the stripped process condensate stream to said water wash in step iv).

[0249] Preferably, in connection with any of said second, third and fourth general embodiments:

[0250] 03129-WO- the oxygen containing gas is air, thus comprising 78 mole% N2and 21 mole% O2, as well as about 0.04 mole% CO2;

[0251] or

[0252] - the oxygen containing gas comprises 30-99.9 mole% O2.

[0253] For instance, in connection with the second general embodiment, the oxygen containing gas is air, or preferably, the oxygen containing gas comprises 30-99.9 mole% O2.

[0254] For instance, in connection with the third general embodiment, the oxygen containing gas is air or the oxygen containing gas comprises 30-99.9 mole% O2.

[0255] For instance, in connection with the fourth general embodiment, the oxygen containing gas is air or the oxygen containing gas comprises 30-99.9 mole% O2.

[0256] The skilled person is able to adapt any of said embodiments of the first general embodiment depending on whether the oxygen containing gas is air or the oxygen containing gas comprises 30-99.9 mole% O2.

[0257] Although the use of air conveys risks in terms of production of solid compounds clogging equipment due to the presence of CO2in the air, which complicates operation of e.g. downstream distillation, these compounds can nonetheless be removed via the downstream distillation step.

[0258] In connection with the second to fourth general embodiments, the benefits associated with the particular water-requirement i.e. wherein the ammonia feed stream in step i) is at least partly obtained from a liquid ammonia feed and the total amount of water (Nm3 / h) being supplied, preferably directly supplied, to the autothermal cracker in the pre-cracked process gas from step i) is lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage; despite of for instance the use of pre-cracking step i) in the second general embodiment being optional, still enables a simpler process and construction for protecting the burner of an autothermal cracker by virtue of not requiring active addition of steam to dilute the oxidant gas or active addition of steam to the burner, suitably to the burner nozzle of the burner to protect the burner nozzle from overheating.

[0259] Any of the embodiments and associated benefits recited in connection with the first general embodiment may be used in connection with any of the second, third and fourth general

[0260] 03129-WOembodiments.

[0261] The present invention provides at least the following benefits:

[0262] - Favorable CAPEX in ammonia cracking plants of large capacity (300000 Nm3 / H2product or higher).

[0263] - Reduced carbon footprint compared to fired tubular cracking with pre-cracking at large scales.

[0264] - Reduced carbon footprint compared to autothermal cracking without pre-cracking at large scales.

[0265] - Better control of NOXin the autothermal cracking while at the same increasing the hydrogen production downstream.

[0266] - Synergy with SOE-unit increases the H2production while reducing the air consumption to the ASU.

[0267] - Autothermal cracker (ATC) outlet temperature of 800°C or higher, or close to 800°C, such as 780°C or such as 790°C, resulting in low ammonia slip from the autothermal cracker. - Co-production of H2and N2.

[0268] - Where a pre-cracking reactor is arranged upstream as a heat exchange pre-cracker arranged in series with the autothermal cracker, the oxygen consumption in the ATC is reduced whereby the ammonia to hydrogen efficiency is improved.

[0269] - The use of a HTEC-s with ATC is advantageous in terms of specific ammonia consumption. The reason is that by pre-converting some ammonia, the demand of oxygen is reduced. The power demand of preferably an ASU for producing the oxygen containing gas, this preferably being O-rich, e.g. at least 75 mole% O2is quite large, meaning that a process without preconversion is much less competitive.

[0270] - The burner of the ATC, in particular the burner nozzle, is protected without the need to separately add steam to the burner.

[0271] - There is higher energy efficiency by virtue of reduced O2-consumption and thereby reduced power demand in the associated ASU. particularly when using the HTEC-s plus ATC configuration.

[0272] - No use of air as oxygen containing gas to the ATC significantly reduces risk of any generated CO2reacting with NH3to form solids (carbonate, bicarbonate and carbamate) that are corrosive and can clog equipment downstream. Further, there is an associated benefit in terms of higher energy efficiency as there is no need to heat inert N2comprising a major part, about 78 vol.% of air as oxygen containing gas.

[0273] 03129-WO- An air enrichment unit, preferably an air separation unit (ASU) is advantageously integrated in the process or plant, as the oxygen from the ASU is utilized in the ATC, while N2from the ASU may be utilized to dilute the oxygen containing gas into the proper content of N2in the oxygen containing gas to the ATC, or as a separate stream to the ATC to protect the burner. - No net steam production when using the HTEC-s plus ATC configuration. No need to export steam, as steam export is often undesired. It is understood that the term "no net steam production" or simply "no steam production" means that there is no steam generation from imported water in the process / plant. The term "imported water" means liquid water passing the battery limit of the process / plant.

[0274] - The heat integration of a CATOX unit arranged downstream in the process or plant, enables less oxygen consumption, thus less oxygen burning, to reach the same required temperature in the ATC. There is an associated improvement in the energy efficiency of the process / plant. - Where the power demand is accounted for, the process or plant meets the demands for at least the European Market (H2to grid), giving hydrogen efficiencies > 78%.

[0275] In a second aspect, the invention relates to a plant for producing a product gas containing nitrogen and hydrogen, comprising:

[0276] - a pre-cracking reactor (pre-cracker) comprising a first ammonia cracking catalyst, the precracker being arranged to receive an ammonia feed stream and provide a pre-cracked process gas containing hydrogen, nitrogen, ammonia by contact with said first ammonia cracking catalyst;

[0277] - an autothermal cracking reactor (autothermal cracker) comprising a non-catalytic partial oxidation zone and a catalytic zone arranged downstream in which the catalytic zone comprises a second ammonia cracking catalyst; the non-catalytic partial oxidation zone being arranged to receive the pre-cracked process gas and an oxygen containing gas, and provide a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia; the catalytic zone being arranged to receive said process gas and provide said product gas containing nitrogen and hydrogen; the autothermal cracker further comprising an outlet for withdrawing the product gas; preferably, wherein the non-catalytic partial oxidation zone and the catalytic zone are arranged in direct fluid communication;

[0278] - wherein the autothermal cracker is arranged to receive an oxygen containing gas, preferably the oxygen containing gas comprising 30-99.9 mole% O2;

[0279] - wherein the autothermal cracker comprises a burner arranged to receive the oxygen containing gas;

[0280] - wherein the plant is arranged for the ammonia feed stream being at least partly obtained

[0281] 03129-WOfrom a liquid ammonia feed and for the total amount of water (Nm3 / h) being supplied, preferably directly supplied, to the autothermal cracker in the pre-cracked process gas being lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage;

[0282] or

[0283] wherein the plant is arranged so that there is no separate steam addition for diluting the oxygen containing gas, or there is no separate steam addition to the burner;

[0284] - wherein the pre-cracker is at least one of:

[0285] an adiabatic pre-cracking reactor (adiabatic pre-cracker);

[0286] a convection type pre-cracking reactor (convection type pre-cracker) selected from at least one of: a convection heating pre-cracking reactor with bayonet tubes (convection heating pre-cracker with bayonet tubes) and a heat exchange pre-cracking reactor (heat exchange pre-cracker);

[0287] preferably the pre-cracker is a heat exchange pre-cracker arranged in series with the autothermal cracker.

[0288] In an embodiment according to the second aspect of the invention:

[0289] - the oxygen containing gas is air, thus comprising 78 mole% N2and 21 mole% O2, as well as about 0.04 mole% CO2;

[0290] or

[0291] - the oxygen containing gas comprises 30-99.9 mole% O2, as recited.

[0292] It is understood here in connection with the plant, that the non-catalytic partial oxidation zone of the autothermal cracker is arranged to receive the oxygen containing gas as:

[0293] - an air-conduit;

[0294] or

[0295] - as an oxygen-containing-gas-conduit comprising 30-99.9 mole% O2.

[0296] The plant is preferably for conducting the process according to any of the preceding process embodiments according to the first aspect of the invention, hence wherein the oxygen containing gas preferably comprises 30-99.9 mole% O2. Accordingly, the non-catalytic partial oxidation zone of the autothermal cracker is arranged to receive the oxygen containing gas as an oxygen containing gas conduit preferably comprising 30-99.9 mole% O2.

[0297] Any of the embodiments and associated benefits of the first aspect of the invention (process) may be used in connection with the second aspect of the invention (plant), or vice versa.

[0298] 03129-WOIt is understood that, for instance, the autothermal cracker is absent of a further downstream catalytic zone comprising a NOXreducing catalyst; or for instance, the plant is absent of a separate catalytic unit comprising a NOXreducing catalyst arranged downstream the autothermal cracker.

[0299] It is understood that, in an embodiment, the autothermal cracker has only two inlets and only one outlet, namely: the pre-cracked process gas inlet, i.e. a conduit carrying the precracked process gas inlet, the oxygen containing gas inlet, i.e. a conduit carrying the oxygen containing gas, and the product gas outlet, i.e. a conduit carrying the product gas being withdrawn from the autothermal cracker.

[0300] It is understood that, in an embodiment, the autothermal cracker has only three inlets and only one outlet, namely: the pre-cracked process gas inlet, i.e. a conduit carrying the precracked process gas inlet, the oxygen containing gas inlet, i.e. a conduit carrying the oxygen containing gas, the N2-rich gas inlet, i.e. a conduit carrying the N2-rich gas, and the product gas outlet, i.e. a conduit carrying the product gas being withdrawn from the autothermal cracker.

[0301] It is understood that in connection with any of the plant embodiments:

[0302] - the conduit carrying the pre-cracked process gas inlet may be referred to as: pre-cracked process gas conduit;

[0303] - the conduit carrying the oxygen containing gas may be referred to as: oxygen-containing-gas-conduit;

[0304] - the conduit carrying the N2-rich gas may be referred to as: N2-rich gas conduit;

[0305] - the conduit carrying the product gas being withdrawn from the autothermal cracker may be referred to as: product gas conduit.

[0306] Same terminology is applicable to other process streams, since there is a conduit carrying a given process stream.

[0307] LEGENDS

[0308] FIG. 1 shows a process for producing hydrogen from an ammonia feed stream which is not in accordance with the invention according to the first general embodiment of the process, and a plant for producing hydrogen from an ammonia feed stream according to the second aspect of the invention.

[0309] 03129-WOFIG. 2 shows a process for producing hydrogen from an ammonia feed stream in accordance with an embodiment of the invention according to the first general embodiment of the process, and a plant for producing hydrogen from an ammonia feed stream according to the second aspect of the invention.

[0310] DETAILED DISCLOSURE

[0311] The first general embodiment of the process excludes the use of air as the oxygen containing gas to the ATC. The oxygen containing gas comprises instead 30-99.9 mole% O2.

[0312] The accompanying figure (FIG. 1) shows a process / plant layout for producing a hydrogen product from ammonia, where air is used as the oxygen containing gas to the ATC. Ammonia is used as received (liquid ammonia feed) from battery limits with no purification. The conversion of an ammonia feed stream 1, which is suitably combined with a recovered ammonia stream 21 into ammonia feed stream 3, takes place in a pre-cracker 10 followed by an autothermal cracker 12. The pre-cracker 10 can be an adiabatic reactor, a convection type pre-cracker, or a heat exchange pre-cracker, for instance a heat exchange pre-cracker (HTEC). The pre-cracked gas 7 (pre-cracked process gas) and the oxygen containing gas 5, 9 are added separately to the autothermal cracker (ATC 12), here air, as more specifically shown in Fig. 2 of applicant's WO2019 / 038251 Al. The oxygen containing gas 5, as shown herein, is optionally mixed with a combined off-gas stream 29 comprising N2into said oxygen containing gas 9. The mixing with downstream stream 29 is valid where the oxygen containing gas 5 is air.

[0313] Further in connection with Fig. 1, the pre-cracked gas 7 and the now oxygen containing gas 9 or 5 are supplied to the ATC 12, which consists of a non-catalytic combustion zone and a catalyst bed downstream where the hot remaining ammonia decomposes into H2and N2. The ATC 12 comprises a burner (not shown), the burner comprises a burner nozzle, the burner being arranged to receive the oxygen containing gas 5, optionally mixed with downstream stream 29. There is no separate steam addition for diluting the oxygen containing gas, or there is no separate steam addition to the burner. The temperature of the effluent from the autothermal cracker is suitably between 800°C and 1100°C or 780°C-1100°C. The then cracked gas is withdrawn as product gas 11 and supplied to a separating step 14, in which the separating step 14 comprises separating the uncracked ammonia in the product gas 11 by a water wash via supply of water 13, thereby providing a separated aqueous stream 17 comprising ammonia, as well as a water-depleted product gas 15. The separated aqueous stream 17 comprising ammonia is supplied to an ammonia recovery step 18, such as

[0314] 03129-WOdistillation, thereby providing: the recovered ammonia stream 21, a light off-gas stream 23 and a stripped process condensate stream 19. Suitably, at least a portion of the stripped process condensate stream 19 is supplied (not shown) to the water wash 14, for instance by mixing with water stream 13. Then, the hydrogen to nitrogen mole ratio of the water-depleted product gas 15 is adjusted in a product gas adjustment unit 16, this unit preferably being at least one of a pressure swing adsorption (PSA) unit and a membrane unit, thereby producing a hydrogen product 25 and a product gas adjustment unit off-gas stream 27. At least a portion of the light off-gas stream 23 is combined with at least a portion of the product gas adjustment unit off-gas stream 27 into the combined off-gas stream 29 comprising N2.

[0315] Now with reference to Fig. 2, in which i.a. the oxygen containing gas comprises 30-99.9 mole% O2.

[0316] The oxygen containing gas 5 is from an air enrichment unit such as an ASU 20 and is for instance supplied directly, thereby without changing its composition, to the ATC 12, the C -content in stream 5 from the ASU 20 is e.g. 99 to 99.5 mole% O2or higher. With this oxygen containing gas 5, the admixing with downstream stream 29 of Fig. 1 is omitted and advantageously a CATOX flue gas 39 is utilized for preheating at least one of streams 5, 1, 3, preferably at least stream 5 (the oxygen containing gas), as also explained below. The ATC 12 comprises a burner (not shown), the burner comprises a burner nozzle, the burner being arranged to receive the oxygen containing gas 5. There is no separate steam addition for diluting the oxygen containing gas, or there is no separate steam addition to the burner. The operation is tailored so that: the oxygen containing gas entering i.e. at inlet the ATC comprises said 30-99.9 mole%; such as at least 75 mole% O2, e.g. about 85 mole% O2, while the content of N2is about 15 vol.%; further, the ammonia feed stream 1, 3 is at least partly obtained from a liquid ammonia feed from battery limits; furthermore, the total amount of water (Nm3 / h) being directly supplied to the ATC 12 in the pre-cracked process gas 7 is lower than : the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage, the margin percentage for instance being 15%.

[0317] The light off-gas stream 23 is combined with the product adjustment unit off-gas stream 27 and further with combustion air 35, thereby producing a catalytic oxidation unit (CATOX) feed gas 37. The CATOX feed gas 37 is pre-heated via pre-heater (heat exchanger) 22 with CATOX flue gas 39 and supplied to CATOX unit 22, thereby producing the CATOX flue gas 39 at about 600°C. The cooled CATOX flue gas exits the process / plant as stream 39'. The ammonia feed stream 1, for instance when combining with the recovered ammonia stream

[0318] 03129-WO21 into ammonia feed stream 3 to the pre-cracker 10, is preheated via pre-heater (heat exchanger) 24 with the CATOX flue gas 39, as so is the oxygen containing gas 5 via preheater 26. The oxygen containing gas 5 is, as recited, preferably sourced from the ASU 20 being supplied with air 31. From the ASU 20 a nitrogen stream 33 is also produced. A portion 33' may be used to dilute the oxygen containing gas 5 and / or be supplied separately 33" to the ATC 12 to protect its burner; while nitrogen not required for said dilution of the oxygen containing gas via line 33', and / or for said separate addition via line 33" to the ATC 12, is suitably exported as nitrogen product 33'".

[0319] Fig. 2 shows an embodiment of the ATC 12 where the oxygen containing gas 5 is directly or indirectly supplied to the ATC 12. In an embodiment, the ATC 12 has only two inlets 5, 7 and only one outlet 11; namely: the pre-cracked process gas inlet, i.e. a conduit carrying the precracked process gas inlet 7, the oxygen containing gas inlet, i.e. a conduit carrying the oxygen containing gas 5, optionally after combining with dilution gas 33', this being here a portion 33' of the nitrogen gas 33 from the ASU 20; and the product gas outlet, i.e. a conduit carrying the product gas 11 being withdrawn from the ATC 12. Fig. 2 shows also another embodiment of the ATC, now having only three inlets and only one outlet; namely: the precracked process gas inlet, i.e. a conduit carrying the pre-cracked process gas inlet 7, the oxygen containing gas inlet, i.e. a conduit carrying the oxygen containing gas 5, e.g. without combining with dilution gas 33'; the N2-rich gas inlet, i.e. a conduit carrying the N2-rich gas 33", and the product gas outlet, i.e. a conduit carrying the product gas 11 being withdrawn from the ATC 12. The numbering of the units and process streams correspond otherwise to those of Fig. 1.

[0320] EXAMPLES

[0321] EXAMPLE I

[0322] There is provided an autothermal cracker (ATC, 12) in which a pre-cracker 10 is a convection type pre-cracking reactor (convection type pre-cracker), here a heat exchange pre-cracking reactor (heat exchange pre-cracker), is arranged in series with the ATC 12 (HTEC-s with ATC). The product gas 11 withdrawn from the ATC 12 is supplied to the heat exchange pre-cracker 10 for providing heat thereto thereby cooling the product gas. This embodiment, which is in accordance with the present invention is compared with an embodiment according to the prior art (applicant's EP3672906 Bl or equivalently WO 2019 / 038251 Al), in which there is no pre-cracker 10 arranged upstream the ATC 12. The oxygen containing gas

[0323] 03129-WOentering the ATC according to this prior art is air, thus about 21 mole% O2and about 78 mole% N2. In the process / plant according to the present invention (HTEC-s with ATC), the oxygen containing gas entering the ATC is about 90 mole% O2and 8 mole% N2. In both arrangements, there is no separate steam addition for diluting the oxygen containing gas to the ATC or there is no separate steam addition to the burner of the ATC. In the process / plant according to the present invention utilizing HTEC-s with ATC and said about 90 mole% O2and 8 mole% N2, there is no steam production. No steam production means that there is no steam generation from imported water in the process / plant. Imported water is liquid water passing the battery limit of the process / plant. Both are for a large-scale process / plant, i.e. producing at least 300000 Nm3H2 / h.

[0324] Table 1 below shows the results:

[0325] TABLE 1

[0326]

[0327] *For the prior art: from Example-Table 1 of EP3672906 Bl or equivalently WO 2019 / 038251 Al.

[0328] Assuming that of all H2from the wash unit (stream 5 Fig. 1 of WO 2019 / 038251 Al), 97% is recovered downstream in a product adjustment unit as H2-product (Product gas), then 51.44% H2x 602700 Nm3 / h x 0.97 = 300728 Nm3H2 / h. O2-consumption in ATC: O2-from air in stream 2, thus 20.60% x 205100 = 42251 Nm3O2 / h. The O2-consumption in ATC with respect to produced H2becomes: 42251 / 300728 = 0.14 Nm3-O21 Nm3-H2.

[0329] ** A value of 0.6 kW per Nm3 / h of O2is used as a first estimate of the power demand and attendant energy consumption.

[0330] The table serves to illustrate that, according to the present invention, it is possible to reduce the O2-consumption in the ATC, thereby enabling reduction in ASU power demand / consumption, when operating with the O2-rich gas entering the ATC. While in the prior art, there is no pre-cracker and no ASU as the oxygen containing gas (referred to as "oxidant" in Table 1) is air, the O2-consumption is higher due to at least the absence of the

[0331] 03129-WOpre-cracker. There is an attendant increase in energy efficiency, at least by using the ASU associated power demand as a proxy, here estimated to 14% by reducing the C -consumption from 0.14 to 0.12 ((0.14-0.12) / 0.14)). Alternatively, using the embodiment according to the present invention as reference (embodiment A) there is about 17% increase in power demand ((0.12-0.14) / 0.12). By the present invention there are no heat losses associated with the high content of the inert N2in air. In addition, there are no issues related to the presence of CO2. In the prior art, where air is used, the presence of CO2causes the production of clogging compounds. These are formed by the reaction of CO2and NH3and are withdrawn in the distillation column downstream. This, while possible, it is preferably avoided, as it requires knowing very well the thermodynamics of formation and decomposition of these compounds, which constrain operating conditions, for instance during turndown scenarios etc.

[0332] EXAMPLE II

[0333] The results of so-called embodiments A) to C) are shown in below Table 2. All three embodiments are for a large-scale process / plant, i.e. producing at least 300000 Nm3H2 / h, and in accordance with the first general embodiment of the process, thus where the oxygen containing gas comprises 30-99.9 mole% O2.

[0334] For embodiments A) and C), HTEC-s with ATC means, as already recited, a heat exchange pre-cracker in series with the autothermal cracker. There is no steam production in the process / plant. There are no further pre-crackers. No steam production means that there is no steam generation from imported water in the process / plant. Imported water is the liquid water passing the battery limit of the process / plant.

[0335] For embodiment B), there is an adiabatic pre-cracker in series with the autothermal cracker. There is steam production in the process / plant. There are no further pre-crackers.

[0336] Specifically for embodiment C), the entire light off-gas stream comprising ammonia from the overhead section of a distillation column (ammonia recovery step) is combined with the entire product adjustment unit off-gas stream and then with combustion air, for producing a catalytic oxidation unit (CATOX) feed gas, as shown in Fig. 2. The CATOX feed gas is supplied to a CATOX unit for producing a CATOX flue gas having a temperature of about 600°C. This hot flue gas is used for preheating the ammonia feed stream to the HTEC-s from about 290°C to about 450°C, and to preheat the oxygen containing gas directly supplied to the ATC from

[0337] 03129-WOabout 35°C to about 300°C. The CATOX flue gas is cooled to about 300°C and used to preheat the CATOX feed gas to about 200°C.

[0338] For all embodiments A) to C), there is no separate steam addition for diluting the oxygen containing gas, or there is no separate steam addition to the burner of the ATC.

[0339] No steam addition to the ATC is expressed in the present invention by requiring that the total amount of water (Nm3 / h) being directly supplied to the autothermal cracker is lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage, the margin percentage being for instance 15%.

[0340] In embodiment A) the HTEC-s with ATC configuration is further with a dilution gas to upstream Ch-containing gas to the ATC. The liquid ammonia feed from battery limits contains 0.47% water. This liquid ammonia feed is calculated as 263148 Nm3 / h. The water content in the liquid ammonia feed from battery limits is thus 1244 Nm3 / h. Applying a margin percentage of 15% the maximum content of allowed water inlet the autothermal cracker becomes 1431 Nm3 / h (1244x1.15). After combining with the dilution gas, the oxygen containing gas directly to the ATC contains 90.5 mole% O2and 8.3 mole% N2(the content of water in the oxygen containing gas is only 0.07 mole%, corresponding here to 28 Nm3 / h). The water content in the pre-cracked process gas inlet the ATC is calculated as 1339 Nm3 / h, representing 0.50 mole% H2O in this stream. So, the requirements defined are met ~1340 < 1431 Nm3 / h water). Thereby, the use of directly and separately supplying steam to the burner of the ATC is avoided.

[0341] In embodiment B) the adiabatic pre-cracker in series with ATC is further with a dilution gas to upstream O2-containing gas to the ATC. The liquid ammonia feed from battery limits contains 0.47% water. This liquid ammonia feed is calculated as 263148 Nm3 / h. The water content in the liquid ammonia feed from battery limits is thus 1244 Nm3 / h. Applying a margin percentage of 15% the maximum content of allowed water inlet the autothermal cracker becomes 1431 Nm3 / h (1244x1.15). The oxygen containing gas directly to the ATC contains 90.5 mole% O2and 8.3 mole% N2(the content of water in the oxygen containing gas is only 0.05 mole%, corresponding here to 25 Nm3 / h). The water content in the pre-cracked process gas inlet the ATC is 1340 Nm3 / h, representing 0.50 mole% H2O in this stream. So, the requirements defined are met ~1340 < 1431 Nm3 / h water). Thereby, the use of directly and separately supplying steam to the burner of the ATC is avoided.

[0342] 03129-WOIn embodiment C), the liquid ammonia feed from battery limits contains 0.47% water. This liquid ammonia feed is calculated as 263148 Nm3 / h. The water content in the liquid ammonia feed from battery limits is thus 1244 Nm3 / h. Applying a margin percentage of 15% the maximum content of allowed water inlet the autothermal cracker becomes 1431 Nm3 / h (1244x1.15). The water content in the pre-cracked process gas inlet the ATC is 1342 Nm3 / h, representing 0.43 mole% H2O in this stream. So, the requirements defined are met (~1342 < 1431 Nm3 / h water). Thereby, the use of directly and separately supplying steam to the burner of the ATC is avoided.

[0343] Further details of the embodiments A) to C) are provided at the bottom of Table 2.

[0344] The present invention according to the first general embodiment of the process, apart from avoiding issues related to the presence of CO2, enables a simple approach for protecting the burner of the ATC, since there is no separate steam addition for diluting the oxygen containing gas in step ii-1) to the ATC, or there is no separate steam addition to the burner. Instead, in the present invention the upstream oxygen containing gas is, in an embodiment, diluted so as to still being O2-rich and have e.g. 15 vol.% inerts, while no steam is added; or the upstream oxygen containing gas already being O2-rich and having e.g. about 15 vol.% inerts, is not diluted and directly supplied to the ATC. In addition, there is a further reduction in the oxygen consumption in the ATC and thereby a reduction in power demand of an ASU producing the oxygen containing gas along with an attendant increase in energy efficiency, while at the same time there is an increase in the hydrogen efficiency, even above 78% (embodiment C)).

[0345] 03129-WOTABLE 2

[0346]

[0347] * In embodiment A), oxygen containing gas entering ATC is after adding a dilution gas to upstream oxygen containing gas. The dilution gas comprises about 90 mole% N2. The upstream oxygen containing

[0348] 03129-WOgas comprises 99.5 mole% O2. By combining with the dilution gas, the upstream oxygen containing gas is indirectly supplied to the ATC and comprises about 90 mole% O2, about 8 mole% N2, 0.5 mole% Ar. ** In embodiment B), oxygen containing gas entering ATC is after adding a dilution gas to upstream oxygen containing gas. The dilution gas comprises about 90 mole% N2. The upstream oxygen containing gas comprises 99.5 mole% O2. By combining with the dilution gas, the upstream oxygen containing gas is indirectly supplied to the ATC and comprises about 90 mole% O2, about 8 mole% N2, 0.5 mole% Ar. ***In embodiment C), there is no addition of a dilution gas to an upstream Ch-containing gas to ATC. The oxygen containing gas is thus directly supplied to the ATC and comprises: 84.5 mole% O2, 15.0 mole% N2, 0.50 mole% Ar. The downstream CATOX flue gas preheats the ammonia feed to the HTEC-s and the oxygen containing gas to the ATC.

[0349] **** A value of 0.6 kW per Nm3 / h of O2 is used as a first estimate of the power demand and attendant energy consumption.

[0350] ***** H2-eff. = molar (vol. basis) flow rate of H2-product I (1.5 x ammonia feed flow rate (vol. basis). The ammonia feed is the liquid ammonia feed from outside battery limits.

[0351] 03129-WO

Claims

CLAIMS1. Process for the production of a product gas containing nitrogen and hydrogen from ammonia, the process comprising the steps of:i) pre-cracking an ammonia feed stream to a pre-cracked process gas containing hydrogen, nitrogen, and ammonia by contact with a first ammonia cracking catalyst;ii-1) non-catalytic partial oxidation of the pre-cracked process gas with an oxygen containing gas to a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia;ii-2) cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a second ammonia cracking catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during at least the pre-cracking of the ammonia feed stream, thereby producing said product gas containing nitrogen and hydrogen;iii) withdrawing the product gas;- wherein the non-catalytic partial oxidation of step ii-1) and the cracking step of step ii-2) are performed in an autothermal cracking reactor (autothermal cracker) and the autothermal cracker comprises a burner arranged to receive the oxygen containing gas in step ii-1);- wherein the oxygen containing gas in step ii-1) comprises 30-99.9 mole% O2;- wherein the ammonia feed stream in step i) is at least partly obtained from a liquid ammonia feed and the total amount of water (Nm3 / h) being supplied, preferably directly supplied, to the autothermal cracker in the pre-cracked process gas from step i) is lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage; - wherein the pre-cracking step i) is conducted in at least one of:an adiabatic pre-cracking reactor (adiabatic pre-cracker) anda convection type pre-cracking reactor (convection type pre-cracker) selected from at least one of: a convection heating pre-cracking reactor with bayonet tubes (convection heating pre-cracker with bayonet tubes) and a heat exchange pre-cracking reactor (heat exchange pre-cracker).

2. Process according to claim 1, wherein the oxygen containing gas in step ii-1) is: at least 70 mole% O2and no more than 30 mole% inerts, in which the inerts comprise at least one of N2 and Ar; or at least 75 mole% O2and no more than 25 mole% inerts, in which the inerts comprise at least one of N2and Ar; preferably, wherein the oxygen containing gas in step ii-1) comprises 75-95 mole% O2and 5-25 mole% inerts; or 80-90 mole% O2and 10-20 mole% inerts.03129-WO3. Process according to any preceding claims, wherein the margin percentage is at least 10%, such as at least 15%, or such as at least 20%.

4. Process according to any preceding claims, wherein the process is for producing at least 300000 Nm3 / h H2product.

5. Process according to any preceding claims, the process further comprises:- supplying an air feed stream to an air enrichment unit, preferably an air separation unit (ASU), for providing at least one of: said oxygen containing gas and a nitrogen gas.

6. Process according to any preceding claims, wherein the oxygen containing gas is indirectly or directly supplied to the autothermal cracker.

7. Process according to claim 6, wherein the oxygen containing gas is indirectly supplied to the autothermal cracker by combining an oxygen-rich gas (O2-rich gas) comprising above 95 mole% O2, such as at least 99 mole% O2, with a dilution gas comprising inerts, thereby producing the oxygen containing gas comprising e.g. 75-95 mole% 02 and 5-25 mole% inerts.

8. Process according to claim 7, wherein the dilution gas is at least a portion of a nitrogen gas from the oxygen enrichment unit; preferably said ASU, preferably the nitrogen gas comprising at least 99 mole% N2, e.g. at least 99.9 mole% N2.

9. Process according to any preceding claims, wherein there is a separate addition of a N2-rich gas stream to the autothermal cracker, such as a separate addition of a N2-rich gas stream comprising at least 90 mole% N2; preferably, at least a portion of said nitrogen gas is from the air enrichment unit, preferably said ASU.

10. Process according to any preceding claims, wherein step ii-2) further comprises simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with at least a portion of the hydrogen formed during cracking of the process gas by contact of the pre-cracked process gas with the second ammonia cracking catalyst.

11. Process according to any preceding claims, wherein the content of hydrogen in the precracked process gas is at least 5-25 vol.% H2, such as at least 10-20 vol.% H2, or at least 20 vol.% H2, for instance 20-25 vol.% H2.03129-WO12. Process according to any preceding claims, wherein:- the first ammonia cracking catalyst comprises a metal or a metal alloy selected from at least one of: iron (Fe), cobalt (Co), ruthenium (Ru), nickel (Ni), preferably Fe and Co as the only metals, or Fe and Ni as the only metals; and / or- the second ammonia cracking catalyst is a nickel containing catalyst, preferably nickel as the only metal- optionally:wherein the second ammonia cracking catalyst is free of a precious metal, the precious metal being at least one of: gold (Au), iridium (Ir), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), silver (Ag); such as the second ammonia cracking catalyst being free of any of Pt and Pd; orwherein there is no third catalyst arranged downstream the second ammonia cracking catalyst, and comprising a precious metal, the precious metal being at least one of: gold (Au), iridium (Ir), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), silver (Ag).

13. Process according to any of the preceding claims, wherein the pre-cracking step i) is conducted in: a heat exchange pre-cracking reactor (heat exchange pre-cracker, HTEC) arranged in series with the autothermal cracker (ATC).

14. Process according to any preceding claims, wherein the process further comprises: electrolysis of a water or steam feedstock, thereby producing electrolysis-oxygen and electrolysis-hydrogen, and providing at least a portion of the electrolysis-oxygen containing gas as at least a portion of the oxygen in the oxygen containing gas.

15. Process according to any preceding claims, wherein the non-catalytic partial oxidation of step ii-1) is performed by burning the pre-cracked gas in said burner with under-stoichiometric amounts of oxygen gas, wherein the content of oxygen in the oxygen containing gas is varied corresponding to a lambda-value (A) between 0.18 and 0.30, or a lambda-value (A) between 0.10 and 0.20, in which A is the ratio between the actual oxygen feed flow and that required for full stoichiometric combustion of the ammonia into nitrogen and water.

16. Process according to any preceding claims, wherein the product gas further contains uncracked ammonia and the process further comprises:iv) supplying, preferably directly supplying, the product gas to a separating step, in which the separating step comprises separating the uncracked ammonia in the product gas by a water wash, thereby providing a separated aqueous stream comprising ammonia and a water-03129-WOdepleted product gas;v-1) supplying, preferably directly supplying, the separated aqueous stream comprising ammonia to an ammonia recovery step, such as distillation, thereby providing a recovered ammonia stream preferably comprising at least 90 vol.% NH3, a light off-gas stream preferably comprising at least 20 vol.% H2, and a stripped process condensate stream i.e. a water stream;v-2) supplying, preferably directly supplying, at least a portion of the recovered ammonia stream to at least one of:the pre-cracking step i), preferably to the ammonia feed stream in the pre-cracking step i); the cracking step ii-1), preferably to the pre-cracked process gas in step ii-1);v-3) optionally: supplying, preferably directly supplying, at least a portion of the stripped process condensate stream to said water wash in step iv).

17. The process according to any preceding claims, wherein the process further comprises: vi) adjusting the hydrogen to nitrogen mole ratio of the product gas or adjusting the hydrogen to nitrogen mole ratio of the water-depleted product gas in a product gas adjustment unit, the product gas adjustment unit being at least one of: a pressure swing adsorption (PSA) unit and a membrane unit, thereby producing a hydrogen product and a product gas adjustment unit off-gas stream.

18. The process according to any preceding claims, wherein the heat exchange pre-cracker is arranged in series with the autothermal cracker and further a pre-cracking reactor, preferably an adiabatic pre-cracker, is arranged upstream said heat exchange pre-cracker arranged in series with the autothermal cracker.

19. The process according to preceding claims 16-17, wherein the process further comprises: - combining at least a portion of the light off-gas stream of step v-1) and / or at least a portion of the product adjustment unit off-gas stream of step vi) with combustion air, thereby producing a catalytic oxidation unit (CATOX) feed gas;- supplying the CATOX feed gas to a CATOX unit, thereby producing a CATOX flue gas, preferably the CATOX flue gas having a temperature of 200-650°C, such as about 600°C; - preheating at least one of: the oxygen containing gas in step ii-1), the ammonia feed stream in step i), and optionally the CATOX feed gas,with at least a portion of the CATOX flue gas.

20. Plant for producing a product gas containing nitrogen and hydrogen, comprising:- a pre-cracking reactor (pre-cracker) comprising a first ammonia cracking catalyst, the pre-03129-WOcracker being arranged to receive an ammonia feed stream and provide a pre-cracked process gas containing hydrogen, nitrogen, ammonia by contact with said first ammonia cracking catalyst;- an autothermal cracking reactor (autothermal cracker) comprising a non-catalytic partial oxidation zone and a catalytic zone arranged downstream in which the catalytic zone comprises a second ammonia cracking catalyst; the non-catalytic partial oxidation zone being arranged to receive the pre-cracked process gas and an oxygen containing gas, and provide a process gas containing nitrogen, water, nitrogen oxides and residual amounts of ammonia; the catalytic zone being arranged to receive said process gas and provide said product gas containing nitrogen and hydrogen; the autothermal cracker further comprising an outlet for withdrawing the product gas; preferably, wherein the non-catalytic partial oxidation zone and the catalytic zone are arranged in direct fluid communication;- wherein the autothermal cracker is arranged to receive an oxygen containing gas, preferably the oxygen containing gas comprising 30-99.9 mole% O2;- wherein the autothermal cracker comprises a burner arranged to receive the oxygen containing gas;- wherein the plant is arranged for the ammonia feed stream being at least partly obtained from a liquid ammonia feed and for the total amount of water (Nm3 / h) being supplied, preferably directly supplied, to the autothermal cracker in the pre-cracked process gas being lower than: the amount of water (Nm3 / h) in said liquid ammonia feed plus a margin percentage;orwherein the plant is arranged so that there is no separate steam addition for diluting the oxygen containing gas, or there is no separate steam addition to the burner;- wherein the pre-cracker is at least one of:an adiabatic pre-cracking reactor (adiabatic pre-cracker);a convection type pre-cracking reactor (convection type pre-cracker) selected from at least one of: a convection heating pre-cracking reactor with bayonet tubes (convection heating pre-cracker with bayonet tubes) and a heat exchange pre-cracking reactor (heat exchange pre-cracker);preferably the pre-cracker is a heat exchange pre-cracker arranged in series with the autothermal cracker.03129-WO

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