Multistage electrically heated adiabatic ammonia cracking process

Abstract

To provide a process and an apparatus for the production of hydrogen gas from ammonia, and a use of the apparatus, so that the overall process has improved modularity while the process is made simple and has the optimized cost and conversion rate.SOLUTION: The invention relates to a process for the production of hydrogen gas (4) from ammonia, thereby obtaining an effluent gas (6) including hydrogen gas. The process includes the steps of providing an ammonia feedstock stream (8) and performing at least one electrical heating and conversion step, the step including: heating in at least one electric heater (12) the ammonia feedstock stream so as to produce a heated gas stream (14); and performing in at least one adiabatic reactor (16) an endothermic cracking reaction of the heated gas stream (14). The adiabatic reactor includes at least one catalyst bed (18) performing the endothermic cracking reaction of the ammonia feedstock stream into the effluent gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001]

[0001] The present invention relates to a process for the production of hydrogen gas from ammonia. The present invention also relates to an apparatus for the production of hydrogen gas from ammonia. The present invention also relates to the use of such an apparatus for an ammonia decomposition reaction.

Background Art

[0002]

[0002] Hydrogen is known for its lightweight nature and optimal combustion characteristics as a fuel, and its environmental consideration during combustion, i.e., when burned with air as an oxidant, there is no release of carbon dioxide (CO2), particulate matter or sulfur, and nitrogen oxides (NOx). This makes hydrogen an attractive medium for energy transition.

[0003]

[0003] However, transporting pure hydrogen gas poses complex challenges for safety reasons and energy density. For this purpose, ammonia (NH3), which contains three hydrogen atoms and facilitates the transport of hydrogen, is a good alternative as a fuel to pure hydrogen gas (H2).

[0004]

[0004] A hydrogen-containing gas can be produced by an endothermic decomposition reaction of an ammonia feedstock stream in a catalytic reactor, such as a plug flow reactor filled with a catalyst bed. The reactor requires a significant amount of heat and energy to maintain the reaction. Therefore, the ammonia feedstock stream and the reactor need to be heated to a sufficiently high temperature range, for example, between 400°C and 800°C, to reach the target conversion.

[0005]

[0005] Known solutions for generating hydrogen from ammonia involve using such a reactor placed inside a combustion chamber. In said combustion chamber, it is known to use some of the available ammonia as fuel to provide heat for the endothermic reaction of ammonia decomposition. However, ammonia suffers from the adverse effects of its slow kinetics during combustion. Additionally, the combustion of ammonia produces nitrogen oxides, which are harmful when inhaled.

[0006]

[0006] Regardless of the fuel used, the use of such indirect heat exchange reactors is accompanied by significant waste heat generation. Therefore, waste heat recovery systems and flue gas treatment are required.

[0007]

[0007] As a result, it is necessary to maintain a reaction medium temperature that is high enough to achieve reasonable ammonia conversion while making the process economically viable and scalable.

[0008]

[0008] Within this framework, efforts have been made to produce an exhaust gas comprising hydrogen gas from an ammonia feedstock stream in order to counter these problems.

Summary of the Invention

[0009]

[0009] For this purpose, the present invention relates to a process for the production of hydrogen gas from ammonia, whereby an exhaust gas comprising hydrogen gas is obtained, said process comprising: - providing an ammonia feedstock stream; - performing at least one electrical heating and conversion step, said step comprising: an electrical heating step comprising heating the ammonia feedstock stream in at least one electrical heater to generate a heated gas stream; a conversion step comprising performing an endothermic decomposition reaction of the heated gas stream in at least one adiabatic reactor, said adiabatic reactor comprising at least one catalyst bed for performing said endothermic decomposition reaction of the ammonia feedstock stream into said exhaust gas.

[0010]

[0010] Thanks to the present invention, a high degree of modularity of the process is made possible, because the present invention enables a single electrical heating and conversion step, or a plurality of electrical heating and conversion steps as required, especially as a function of the conversion rate at the end of the overall process.

[0011]

[0011] In other words, while knowing that the conversion rate can be increased while increasing the number of electrical heating and conversion steps and the temperature level in the preheater, by separating the classical ammonia decomposition conversion into two different steps, an electrical heating and a conversion step, it is possible to customize the target conversion rate of the ammonia feedstock stream into hydrogen gas according to the number of said electrical heating and conversion steps.

[0012]

[0012] In particular, during the electrical heating step, the temperature of the ammonia feedstock stream is brought to a temperature at which an endothermic decomposition reaction can occur.

[0013]

[0013] During the conversion step, no additional heat is supplied to the heated gas stream such that the temperature of the gas stream gradually decreases with the adiabatic reactor until the temperature reaches a temperature at which the catalyst is already deactivated.

[0014]

[0014] Furthermore, the use of electrical heating eliminates the need to supply fuel into the combustion chamber to bring heat to the reaction medium, thus removing this associated cost. Since there is no combustion during the electrical heating step, no further flue gas treatment is required.

[0015]

[0015] In short, the present invention makes it possible to simplify the process, optimize the cost and conversion rate of the process while improving the modularity of the overall process.

[0016]

[0016] The term "adiabatic reactor" is used to denote a chemical reactor in which a decrease in temperature is experienced from the inlet to the outlet of the reactor.

[0017]

[0017] The term "electric heater" is used to mean an electrically supplied device configured to heat an ammonia feedstock stream, for example based on the Joule heating effect. The electric heater does not include a catalyst bed suitable for converting a chemical reactant (e.g., ammonia) into a chemical product (e.g., hydrogen gas). Thus, the endothermic decomposition reaction of the ammonia feedstock stream occurring in the electric heater can be neglected compared to said reaction of such an ammonia feedstock stream occurring in the adiabatic reactor.

[0018]

[0018] The term "off-gas" is used to denote the raw gas product produced by the endothermic decomposition reaction that converts ammonia into hydrogen gas in the conversion step prior to the purification step. The off-gas is advantageously provided with hydrogen gas, nitrogen gas, and possibly some undissociated ammonia.

[0019]

[0019] The present invention may comprise at least one of the following optional features, employed independently or in combination.

[0020]

[0020] The electric heater is based on the Joule heating effect.

[0021]

[0021] The electric heater is based on electromagnetic induction.

[0022]

[0022] Each of the electric heating and conversion steps may require a plurality of electric heaters and / or a plurality of adiabatic reactors.

[0023]

[0023] At least one of the electric heaters, in particular the first electric heater, is protected by a protective coating to prevent nitridation of said electric heater.

[0024]

[0024] Alternatively, the temperature of the first electric heater is below the critical temperature, i.e., approximately less than 500 °C.

[0025]

[0025] The temperature of the first electric heater can be higher when the first electric heater is protected by a protective coating.

[0026]

[0026] The process comprises the following steps: - Performing at least two electric heating and conversion steps, including a first electric heating and conversion step and a last electric heating and conversion step therein. It is provided with.

[0027]

[0027] In particular, the process comprises performing at least five electric heating and conversion steps.

[0028]

[0028] The last electric heating and conversion step is: - Heating, in a last electric heater, an upstream partially converted gas stream from an upstream adiabatic reactor to generate a last heated and partially converted gas stream; and - Performing a last endothermic decomposition reaction of the last heated and partially converted gas stream in a last adiabatic reactor, wherein the last adiabatic reactor comprises at least one catalyst bed for performing an endothermic decomposition reaction of ammonia into hydrogen gas, thereby obtaining the exhaust gas.

[0029]

[0029] The first electric heating and conversion step is: - Heating an ammonia feedstock stream in a first electric heater to generate a first heated ammonia stream; and - Performing a first endothermic decomposition reaction of the first heated ammonia stream in an adiabatic reactor, wherein the adiabatic reactor comprises at least one catalyst bed suitable for converting ammonia into a first partially converted gas stream comprising hydrogen gas.

[0030]

[0030] The process comprises a step of bypassing at least one or some of the electric heating and conversion steps.

[0031]

[0031] The process further comprises the step of removing unreacted ammonia from the exhaust gas, thereby obtaining an unreacted ammonia stream and an exhaust gas depleted of ammonia.

[0032]

[0032] The step of removing unreacted ammonia can be carried out by partial condensation of unreacted ammonia, temperature swing adsorption (TSA), scrubbing of unreacted ammonia, for example, by washing the unreacted ammonia with water.

[0033]

[0033] The process further comprises the step of recycling the unreacted ammonia stream resulting from the step of removing unreacted ammonia as part of the ammonia feedstock stream.

[0034]

[0034] The exhaust gas comprises nitrogen gas.

[0035]

[0035] The process comprises the step of providing an ammonia feedstock stream from a liquid ammonia supply.

[0036]

[0036] The process comprises the step of vaporizing the liquid ammonia supply in a vaporizer so as to provide the ammonia feedstock stream, in particular by using the exhaust gas as a heat source into the vaporizer.

[0037]

[0037] The ammonia feedstock stream can be brought to a sufficiently high temperature so as to avoid the use of a preheater.

[0038]

[0038] The process comprises the step of pumping the liquid ammonia supply using a pump prior to the step of vaporizing the liquid ammonia supply.

[0039]

[0039] The process comprises the step of vaporizing the liquid ammonia supply in a vaporizer so as to provide a vaporized ammonia stream, in particular by using a pre-cooled exhaust gas.

[0040]

[0040] The process comprises providing, as the ammonia feedstock stream, the vaporized ammonia stream.

[0041]

[0041] The exhaust gas is cooled in a preheater so as to form the pre-cooled exhaust gas. This has the advantage that maximum heat is recovered from the exhaust gas.

[0042]

[0042] The process comprises providing an ammonia feedstock stream from a pipeline containing gaseous ammonia.

[0043]

[0043] In this way, ammonia in gaseous state can be provided directly into the preheater.

[0044]

[0044] The process comprises preheating the ammonia feedstock stream by a preheater to produce a preheated ammonia stream upstream of at least one electrical heating and conversion step.

[0045]

[0045] The process comprises preheating the vaporized ammonia stream and / or the gaseous ammonia feed (e.g. from the pipeline) by a preheater to produce a preheated ammonia stream upstream of at least one electrical heating and conversion step.

[0046]

[0046] The process comprises providing, as the ammonia feedstock stream, the preheated ammonia stream.

[0047]

[0047] The step of preheating the ammonia feedstock stream, in particular the vaporized ammonia stream and / or the gaseous ammonia feed, by a preheater to produce a preheated ammonia stream is upstream of the first electrical heating and conversion step.

[0048]

[0048] The preheating step is carried out by the exhaust gas.

[0049]

[0049] The process It may further include an upstream decomposition step that is performed upstream of at least one electric heating and conversion step, and the upstream decomposition step is performed by a heat source including a water boiler, or by a preheater, or by a combination thereof.

[0050]

[0050] The upstream decomposition step may include heating the vaporized ammonia stream and / or the gaseous ammonia supply (e.g., from the pipeline) by the water boiler.

[0051]

[0051] The upstream decomposition step is preferably carried out in at least one adiabatic reactor, - of the preheated ammonia stream and / or - of the vaporized ammonia stream and / or the gaseous ammonia supply preheated by the water boiler, comprising an endothermic decomposition reaction, thereby obtaining a pre-decomposed stream and providing the pre-decomposed stream as the ammonia feedstock stream.

[0052]

[0052] The upstream decomposition step is carried out upstream of the first electric heating and conversion step.

[0053]

[0053] The heating load is higher in the first electric heater than in the remaining electric heaters of the other electric heating and conversion steps.

[0054]

[0054] The term "heating load" means the heating power supplied to the ammonia feedstock stream, regardless of whether it is in a liquid or gaseous state. The higher the heating load, the higher the temperature of the stream at a given duration.

[0055]

[0055] Given the temperature difference between the initial temperature of the ammonia feedstock stream and the desired temperature of the ammonia feedstock at the outlet, the first electric heater may be configured to provide a greater amount of heat to the ammonia than the other electric heaters.

[0056]

[0056] The temperature of the ammonia feedstock stream upstream of the first electric heater is lower compared to the upstream of the remaining electric heaters in the other electric heating and conversion steps. Therefore, the heating load can be adapted to adjust the temperature difference.

[0057]

[0057] The heating load can be higher in the last electric heater compared to the remaining electric heaters in the other electric heating and conversion steps.

[0058]

[0058] Therefore, the high heating load at the last electric heater, compared to the remaining electric heaters in the other intermediate conversion steps, enables reaching the desired conversion rate, especially before any separation or purification step of hydrogen gas from the exhaust gas.

[0059]

[0059] To reach the final expected conversion of ammonia to hydrogen gas, the last electric heater can be configured to provide a larger amount of heat to the ammonia compared to the other electric heaters.

[0060]

[0060] The heating load is higher in the first electric heater and the last electric heater compared to the remaining electric heaters in the other electric heating and conversion steps.

[0061]

[0061] The process further comprises a step of hydrogen gas purification comprising feeding the exhaust gas, especially the exhaust gas depleted in ammonia, into a hydrogen gas purification unit, thereby obtaining a purified exhaust gas comprising hydrogen gas and off-gas.

[0062]

[0062] The step of hydrogen gas purification comprises separating hydrogen gas from nitrogen gas, thus generating purified hydrogen gas.

[0063]

[0063] The said step of hydrogen gas purification is performed by pressure swing adsorption (PSA), temperature swing adsorption (TSA), separation by partial condensation, such as cryogenic separation or cryogenic distillation, membrane separation, or a combination thereof.

[0064] Specifically, cryogenic separation or distillation has the advantage of significantly reducing the hydrogen gas content in the off-gas. The hydrogen recovery rate from the exhaust gas is increased.

[0065] As the hydrogen gas purification unit, a combination of a plurality of PSAs or at least one PSA using a downstream membrane can be used.

[0066] For example, two PSAs in series can be provided to supply the off-gas from the first PSA to the second PSA in order to recover most of the hydrogen gas in the off-gas.

[0067] Of course, the purification step can be performed regardless of the fact that there is exhaust gas with depleted ammonia.

[0068] The term "off-gas" refers to the exhaust gas or the remaining gas generated in the hydrogen gas purification unit after separating hydrogen gas from nitrogen gas. The "off-gas" includes, for example, nitrogen gas and the remaining hydrogen gas drawn into the off-gas by the internal operation of the hydrogen gas purification unit, but the content of the residual hydrogen gas is low compared to the content of nitrogen gas.

[0069] The hydrogen content of the purified exhaust gas is greater than 90%, preferably greater than 99.99%, and more preferably greater than 99.999%.

[0070] The temperature at the inlet of the electric heater ranges from 20 to 500 °C.

[0071] The temperature at the inlet of the adiabatic reactor ranges from 400 to 800 °C.

[0072] The temperature at the outlet of the adiabatic reactor ranges from 300 to 500 °C.

[0073]

[0073] The present invention also relates to an apparatus for the production of hydrogen gas from ammonia, said apparatus comprising: · an electric heater configured to receive an ammonia feedstock stream for generating a heated gas stream; · an adiabatic reactor arranged to perform an endothermic decomposition reaction of the heated gas stream, said adiabatic reactor comprising at least one catalyst bed suitable for said endothermic decomposition reaction of the ammonia feedstock stream into an exhaust gas comprising hydrogen gas; comprising at least one electrically heated and conversion stage comprising the above.

[0074]

[0074] The present invention may comprise at least one of the following optional features, employed independently or in combination.

[0075]

[0075] The electric heater is based on the Joule heating effect.

[0076]

[0076] The electric heater is based on electromagnetic induction.

[0077]

[0077] Some of the electrically heated and conversion stages are identical to each other.

[0078]

[0078] All of the electrically heated and conversion stages are identical to each other.

[0079]

[0079] As a variant, at least two of the electrically heated and conversion stages are different from each other.

[0080]

[0080] In this case, some of the electrically heated and conversion stages can comprise a different number of electric heaters and adiabatic reactors, or these stages can have different types of catalyst beds compared to each other.

[0081]

[0081] The apparatus - comprises at least two electrically heated and conversion stages having therein a first electrically heated and conversion stage and a last electrically heated and conversion stage, said stages being placed one after the other or in series.

[0082]

[0082] The last electrical heating and conversion stage comprises: · at least one final electrical heater configured to heat the upstream partially converted gas stream from the adiabatic reactor of the upstream conversion stage in order to generate a final heated and partially converted gas stream; · at least one final adiabatic reactor configured to perform a final endothermic decomposition reaction of the final heated and partially converted gas stream, said final adiabatic reactor comprising at least one catalyst bed suitable for converting ammonia into said exhaust gas.

[0083]

[0083] The first electrical heating and conversion stage comprises: · at least one first electrical heater configured to heat the upstream ammonia feedstock stream in order to generate a first heated ammonia stream; · at least one adiabatic reactor configured to perform a first endothermic decomposition reaction of the first heated ammonia stream, said adiabatic reactor comprising at least one catalyst bed suitable for the endothermic decomposition reaction of the ammonia feedstock stream into a first partially converted gas stream comprising hydrogen gas.

[0084]

[0084] The apparatus comprises a pump configured to be supplied with an ammonia feedstock stream, in particular an ammonia feedstock stream from a liquid ammonia supply.

[0085]

[0085] The apparatus comprises a vaporizer configured to provide a vaporized ammonia feedstock stream from the ammonia feedstock stream.

[0086]

[0086] The apparatus comprises a pump arranged to be supplied with a liquid ammonia supply.

[0087]

[0087] The vaporizer is arranged downstream of the pump.

[0088]

[0088] The device further comprises a preheater arranged to preheat the ammonia feedstock stream in order to generate a preheated ammonia feedstock stream upstream of at least one electrical heating and conversion stage.

[0089]

[0089] The preheater is arranged to preheat the ammonia feedstock stream, such as the vaporized ammonia feedstock stream, in order to generate a preheated ammonia feedstock stream upstream of at least one electrical heating and conversion stage.

[0090]

[0090] The ammonia feedstock stream can be brought to a sufficiently high temperature so as to avoid the use of the preheater.

[0091]

[0091] The device further comprises an unreacted ammonia removal unit configured to remove unreacted ammonia from the exhaust gas.

[0092]

[0092] The ammonia removal unit is capable of obtaining from the exhaust gas an unreacted ammonia stream and an exhaust gas depleted of ammonia.

[0093]

[0093] The device further comprises a hydrogen gas purification unit configured such that the exhaust gas, in particular the exhaust gas depleted of ammonia from the ammonia removal unit, is supplied thereto.

[0094]

[0094] In this way, the hydrogen gas purification unit is capable of obtaining from the gas a purified exhaust gas comprising hydrogen gas and an offgas from the exhaust.

[0095]

[0095] The device comprises at least three electrical heating and conversion stages, preferably at least four electrical heating and conversion stages, and more preferably at least five electrical heating and conversion stages.

[0096]

[0096] With five electrical heating and conversion stages and the inlet temperature of the adiabatic reactor at 600 °C, a conversion rate of 95% can be expected. With more than six electrical heating and conversion stages, the conversion rate can be excellent up to 99%.

[0097]

[0097] The device further comprises at least a bypass line arranged to bypass at least one or some of the electrical heating and conversion stages.

[0098]

[0098] In this way, there is no substantial reaction in the bypassed electrical heating and conversion stages, and the decomposition reaction occurs only in the remaining other electrical heating and conversion stages.

[0099]

[0099] The use of the bypass line makes it possible to reduce the replacement of the catalyst filling in the adiabatic reactor and enables maintenance intervention when one or more conversion stages need to be checked or repaired. The bypass line can also be used during part-load operation.

[0100]

[0100] The bypass line can be a conduit or a pipe and is arranged to avoid one or some of the electrical heating and conversion stages. The bypass line makes it possible to increase or decrease the number of the stages. In other words, the bypass line makes it possible to adjust the number of the stages while connecting the stages of the device to another stage.

[0101]

[0101] For example, the bypass line is configured to connect some of the stages between them, thereby separating at least one stage between the connected stages.

[0102]

[0102] The device further comprises an upstream decomposition stage upstream of at least one electrical heating and conversion stage, and the upstream decomposition stage comprises a heat source including a water boiler, or a preheater, or a combination thereof.

[0103]

[0103] The upstream decomposition stage is upstream of the first electrical heating and conversion stage.

[0104]

[0104] At least one of the electric heaters, in particular the first electric heater and / or the preheater, is protected by a protective coating in order to prevent nitridation of the electric heater.

[0105]

[0105] Alternatively, the temperature of the first electric heater is below a critical temperature, i.e. less than approximately 500 °C.

[0106]

[0106] The adiabatic reactor is a plug flow reactor or a shaft reactor.

[0107]

[0107] The catalyst bed comprises ruthenium, nickel, aluminum oxide, or combinations thereof.

[0108]

[0108] The catalyst bed of each adiabatic reactor is identical compared to the other adiabatic reactors.

[0109]

[0109] The catalyst beds of at least two adiabatic reactors are identical compared to each other.

[0110]

[0110] One of the electrical heating and conversion stages, in particular the adiabatic reactor of the first electrical heating and conversion stage, comprises a catalyst bed configured to be activated at an activation temperature lower than the activation temperature of the catalyst bed of the other adiabatic reactor of the subsequent stage.

[0111]

[0111] The adiabatic reactor, in particular the adiabatic reactor of the last electrical heating and conversion stage, comprises a reaction chamber and at least two catalyst beds, among others, - a first catalyst bed in a first zone of the reaction chamber, and - a second catalyst bed in a second zone of the reaction chamber, wherein the second zone is located downstream of the first zone in the flow direction of the ammonia feedstock stream.

[0112]

[0112] The first and second catalyst beds are arranged to carry out the endothermic decomposition reaction of ammonia into the reaction chamber, and the first catalyst bed has an activation temperature higher than the activation temperature of the second catalyst bed.

[0113]

[0113] The reactor of the present invention makes it possible to optimize the decomposition reaction along the entire reaction chamber and to limit the deterioration of the catalyst bed having its own activation temperature.

[0114]

[0114] The first zone is adjacent to the second zone.

[0115]

[0115] The first zone and the second zone are separated by a liquid-permeable layer arranged to hold the first catalyst bed in the first zone and the second catalyst bed in the second zone. In a variant form, the catalysts of the first and second catalyst beds can be directly stacked one after the other and filled into the reactor.

[0116]

[0116] The activation temperature of the first catalyst bed ranges from 600 °C to 800 °C.

[0117]

[0117] The activation temperature of the second catalyst bed ranges from 400 °C to 700 °C.

[0118]

[0118] The temperature of the reactor decreases along the reactor from the beginning. Therefore, since the activation temperature of the first catalyst bed is higher than the activation temperature of the second catalyst bed, the decomposition reaction is optimized and the catalyst bed is not damaged by an excessively high temperature of the ammonia feedstock stream and / or the partially decomposed ammonia gas stream.

[0119]

[0119] The catalyst bed comprises a catalytically active material, in particular a catalytically active material on a support such as an aluminum oxide (Al2O3) support.

[0120]

[0120] In particular, such materials can avoid nitridation.

[0121]

[0121] The first and second catalyst beds comprise the same catalytically active material, for example nickel as the catalytically active material.

[0122]

[0122] The first and second catalyst beds comprise catalytically active materials of the same type with different concentrations, for example catalytically active materials containing nickel.

[0123]

[0123] The first and second catalyst beds may comprise 5 to 75 wt% nickel.

[0124]

[0124] For example, the first catalyst bed comprises 10 to 45 wt% nickel, preferably 15 to 30 wt% nickel, as the catalytically active material, and the second catalyst bed comprises up to 50 wt% nickel, preferably 20 to 40 wt% nickel, as the catalytically active material.

[0125]

[0125] The first catalyst bed comprises a catalytically active material different from that of the second catalyst bed.

[0126]

[0126] For example, the first catalyst bed comprises nickel as the catalytically active material, and the second catalyst bed comprises ruthenium as the catalytically active material.

[0127]

[0127] The second catalyst bed comprises 0.5 to 4 wt% ruthenium as the catalytically active material.

[0128]

[0128] The catalyst bed is a structured catalyst layer.

[0129]

[0129] Alternatively, the catalyst bed is a loaded catalyst bed.

[0130]

[0130] The reactor comprises more than two catalyst beds, and each catalyst bed is arranged in a different zone of the reaction chamber.

[0131]

[0131] The catalyst bed configured in the zone closest to the inlet of the adiabatic reactor has the highest activation temperature among all the catalyst beds, and the catalyst bed configured in the zone closest to the outlet of the adiabatic reactor has the lowest activation temperature among all the catalyst beds.

[0132]

[0132] The catalyst beds are arranged such that their activation temperatures decrease from the inlet to the outlet, and each catalyst bed has its activation temperature.

[0133]

[0133] Therefore, the second catalyst bed will start safely before approaching the maximum applicable temperature of the first catalyst bed. The "maximum applicable temperature of the catalyst bed" here means the maximum temperature at which the catalyst bed can be heated. Exceeding such a maximum applicable temperature may damage the catalyst.

[0134]

[0134] The adiabatic reactor is arranged such that the ammonia feedstock stream at the inlet of the reactor has a temperature ranging from 400 °C to 900 °C, preferably between 600 and 800 °C.

[0135]

[0135] The inlet of the adiabatic reactor in the first electrical heating and conversion stage has a temperature ranging from 500 to 700 °C.

[0136]

[0136] The inlet of the adiabatic reactor in the last electrical heating and conversion stage has a temperature ranging from 600 to 850 °C.

[0137]

[0137] The adiabatic reactor is arranged such that the exhaust gas at the outlet of the reactor has a temperature ranging from 300 °C to 600 °C, preferably between 400 and 500 °C. For example, the temperature at the outlet of the reactor is approximately 450 °C.

[0138]

[0138] The outlet region of the adiabatic reactor is provided with a low-temperature active catalyst, for example, a catalyst that is active at a temperature ranging from 300 to 600 °C.

[0139]

[0139] The present invention also relates to the use of the apparatus of the present invention for the endothermic decomposition reaction of an ammonia feedstock stream into an exhaust gas comprising hydrogen gas.

[0140]

[0140] It should be noted that all of the above features and configurations are purely examples. Other features, details, and advantages of the present invention will become clearer by reading the following detailed description, which is shown purely by way of example and illustration, together with several embodiments shown with reference to the accompanying schematic drawings.

Brief Description of the Drawings

[0141]

Figure 1

[0141] A diagram schematically showing the apparatus of the present invention, by way of example and not limitation.

Modes for Carrying Out the Invention

[0142]

[0142] Referring to FIG. 1, an apparatus 2 for the production of hydrogen gas from ammonia.

[0143]

[0143] The apparatus 2 comprises four electrically heated and conversion stages 9, 10, all identical to each other in terms of heating power and reactor volume.

[0144]

[0144] The apparatus 2 comprises a first electrically heated and conversion stage 9, 10 and a last electrically heated and conversion stage 9, 10, said stages being arranged in series.

[0145]

[0145] The first electrically heated and conversion stage · One first electric heater 12 configured to heat an upstream ammonia feedstock stream 8 to produce a first heated ammonia stream 14, · One first adiabatic reactor 16 configured to perform a first endothermic decomposition reaction of the first heated ammonia stream 14, said adiabatic reactor 16 comprising one catalyst bed 18 suitable for the endothermic decomposition reaction of the ammonia feedstock stream 8 into a first partially converted gas stream 20 containing hydrogen gas 4.

[0146]

[0146] The last electrically heated and conversion stage · One final electric heater 12 configured to heat the upstream partially converted gas stream 22 from the adiabatic reactor 16 of the upstream conversion stage 10 in order to produce a final heated and partially converted gas stream 24; · One final adiabatic reactor 16 configured to perform a final endothermic decomposition reaction on the final heated and partially converted gas stream 24, said final adiabatic reactor 16 comprising one catalyst bed 18 suitable for converting ammonia into said exhaust gas 6.

[0147]

[0147] The catalyst bed 18 comprises ruthenium, nickel, aluminum oxide, or a combination thereof.

[0148]

[0148] The catalyst bed 18 of each adiabatic reactor 16 is identical compared to the other adiabatic reactors 16.

[0149]

[0149] In this way, the activation temperatures of the catalyst beds 18 of each adiabatic reactor 16 are identical compared to each other.

[0150]

[0150] The apparatus 2 comprises a pump 17 configured to be supplied with an ammonia feedstock stream 8, in particular an ammonia feedstock stream 8 from a liquid ammonia supply (not shown).

[0151]

[0151] The apparatus 2 comprises a vaporizer 19 downstream of the pump 17, said vaporizer 19 being configured to provide a vaporized ammonia feedstock stream 21 from the ammonia feedstock stream 8.

[0152]

[0152] The apparatus 2 further comprises a preheater 24 arranged to preheat the vaporized ammonia feedstock stream 21 in order to produce a preheated ammonia feedstock stream 26 upstream of the first electric heating and conversion stages 9, 10.

[0153]

[0153] The apparatus 2 further comprises an undecomposed ammonia removal unit 28 configured to remove undecomposed ammonia from the exhaust gas.

[0154]

[0154] The ammonia recovery unit 28 enables the acquisition of an unconverted ammonia stream 30 and an exhaust gas 32 depleted of ammonia from the exhaust gas 6.

[0155]

[0155] The apparatus 2 further comprises a hydrogen gas purification unit 34 configured to be supplied with the exhaust gas 32 depleted of ammonia.

[0156]

[0156] In this way, the hydrogen gas purification unit 34 enables the acquisition of a purified exhaust gas 36 containing the hydrogen gas 4 and the off-gas 38 from the exhaust gas 6.

[0157]

[0157] In an example not shown, the apparatus 2 further comprises at least a bypass line (not shown) configured to bypass at least one or some of the heating and conversion stages 9, 10.

[0158]

[0158] In this way, there is no substantial reaction in the bypassed heating and conversion stages 9, 10, and the decomposition reaction occurs only in the remaining other heating and conversion stages 9, 10.

[0159]

[0159] The use of the bypass line makes it possible to reduce the replacement of the catalyst filling in the adiabatic reactor 16 and enables maintenance intervention when one or more of the conversion stages 10 need to be checked or repaired. The bypass line can also be used during part-load operation.

[0160]

[0160] The bypass line can be a conduit or a pipe and is arranged to avoid one or some of the heating and conversion steps. The bypass line makes it possible to increase or decrease the number of said steps. In other words, the bypass line makes it possible to adjust the number of steps while connecting the steps of device 2 to another step.

[0161]

[0161] For example, the bypass line is configured to connect some of the steps therebetween, thereby separating at least one step between the connected steps.

[0162]

[0162] Device 2 further comprises an upstream decomposition step 40 upstream of the first electrical heating and conversion steps 9, 10, said upstream decomposition step 40 comprising a heat source (not shown) including a water boiler, or a preheater 24, or a combination thereof.

[0163]

[0163] At least one of the electric heaters 12, in particular the first electric heater 12 and / or the preheater 24, is protected by a protective coating to prevent nitridation of the electric heater 12.

[0164]

[0164] The temperature of the first electric heater 12 is below the critical surface temperature, i.e., approximately less than 500°C.

[0165]

[0165] A comparative example for device 2 based on six electrical heating and conversion steps 9, 10 is described below.

[0166]

[0166] To achieve the modularized device 2, all the electric heaters 12 were designed to have the same heating load so as to heat from 450°C after the previous adiabatic reactor 16 to the required inlet temperature of approximately 600°C.

[0167]

[0167] For the first and last stages, higher heating loads are required to heat from 245 °C to 600 °C and from 450 °C to 745 °C. To achieve this, additional electric heaters 12 with the same heating load as the other electric heaters 12 are introduced upstream of the first and last stages. Alternatively, two electric heaters 12 having twice the capacity compared to the other electric heaters 12 can be introduced upstream of the first and last stages.

[0168]

[0168] Using electric heaters with the same electrical duty reduces the device design effort and capital expenditure (CAPEX).

[0169]

[0169] Using a total of six electric heating and conversion stages 9, 10, approximately 99% of the ammonia feedstock stream 8 was converted into hydrogen gas 4 and nitrogen gas.

[0170]

[0170] Downstream of the present invention, two purification methods for this component were considered for the calculations of PSA and cryogenic methods, i.e., cryogenic separation by nitrogen liquefaction.

[0171]

[0171] PSA usually consists of a lower hydrogen gas recovery rate, i.e., between 80 - 90%. In this case, a larger amount of off-gas 38 with hydrogen gas 4 is available and needs to be thermally vaporized outside the device 2.

[0172]

[0172] In the case of cryogenic separation, approximately 95% of the hydrogen gas 4 can be recovered. In this case, the off-gas 38 with hydrogen gas 4 can be combusted. The overall ammonia and power consumption for this device 2 are shown in Table 1 and compared with three SMR-based devices using different temperatures and purification techniques.

Claims

1. A process for the production of hydrogen gas (4) from ammonia, comprising the steps of: obtaining an exhaust gas (6) comprising hydrogen gas (4) by said process; - supplying an ammonia feed stream (8), performing at least one electrical heating and conversion step, said step comprising: heating said ammonia feed stream (8) in at least one electric heater (12) to produce a heated gas stream (14); carrying out an endothermic decomposition reaction of said heated gas stream (14) in at least one adiabatic reactor (16), said adiabatic reactor (16) comprising at least one catalyst bed (18) for carrying out said endothermic decomposition reaction of said ammonia feed stream (8) into said exhaust gas (6).

2. 10. The process of claim 1, comprising performing at least two electrical heating and converting steps, including a first electrical heating and converting step and a final electrical heating and converting step.

3. 3. The process of claim 2 comprising performing at least five electrical heating and converting steps.

4. 4. The process of any one of claims 1 to 3, further comprising the step of preheating the ammonia feed stream (8) by a preheater (24) to produce a preheated ammonia stream (26) upstream of at least one electrical heating and conversion step.

5. 5. The process of any one of claims 1 to 4, further comprising an upstream cracking step upstream of the at least one electrical heating and conversion step, the upstream cracking step being performed by a heat source including a water boiler, or by a preheater (24), or a combination thereof.

6. 6. The process according to claim 1, further comprising removing undecomposed ammonia from the exhaust gas (6), thereby obtaining an unconverted ammonia stream (30) and an ammonia-depleted exhaust gas (32).

7. 7. The process of claim 6, wherein the step of removing the undecomposed ammonia is performed by partial condensation of the undecomposed ammonia, temperature swing adsorption (TSA), scrubbing of the undecomposed ammonia, e.g., washing the undecomposed ammonia with water.

8. 8. The process according to any one of claims 1 to 7, further comprising feeding the exhaust gas (6), in particular the ammonia-depleted exhaust gas (32), into a hydrogen gas purification unit (34), thereby obtaining a purified exhaust gas (36) comprising hydrogen gas (4) and off-gas (38).

9. 9. The process of claim 8, wherein the hydrogen gas purification unit (34) is a combination of multiple pressure swing adsorption (PSA) or at least one PSA with downstream membrane.

10. An apparatus (2) for the production of hydrogen gas from ammonia, said apparatus (2) obtaining an exhaust gas (6) comprising hydrogen gas (4) from an ammonia feed stream (8), said apparatus (2) comprising at least one electric heating and conversion stage (9, 10), said electric heating and conversion stage (9, 10) comprising: an electric heater (12) configured to receive said ammonia feed stream (8) to produce a heated gas stream (14); an adiabatic reactor (16) arranged to carry out an endothermic decomposition reaction of the heated gas stream (14), said adiabatic reactor (16) comprising at least one catalyst bed (18) suitable for said endothermic decomposition reaction of the ammonia feed stream (8) into an exhaust gas (6) comprising hydrogen gas (4).

11. 11. The device (2) according to claim 10, comprising at least two electric heating and converting stages, said stages being placed one after the other or in series, said stages comprising a first electric heating and converting stage and a last electric heating and converting stage.

12. 12. The device (2) according to claim 11, comprising at least five electric heating and conversion stages.

13. 13. The apparatus (2) according to any one of claims 10 to 12, comprising an undecomposed ammonia removal unit configured to remove undecomposed ammonia from the exhaust gas.

14. 14. The apparatus (2) according to any one of claims 10 to 13, further comprising a preheater (24) for preheating said ammonia feed stream (8) upstream of said at least one electrical heating and conversion stage (9, 10) so as to produce a preheated ammonia stream (26).

15. Upstream of at least one of said electrical heating and conversion stages (9, 10), there is further provided an upstream decomposition stage (40), said upstream decomposition stage (40) comprising: A heat source including a water boiler, or a preheater (24), or a combination thereof.

15. The device (2) according to claim 14, comprising:

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