LU103170B1 - Start-up of a plant for the catalytic decomposition of ammonia - Google Patents

Abstract

The invention relates to a plant for producing H2 by catalytic decomposition of NH3. The plant according to the invention can be operated in a start-up mode in order to heat devices of the plant to an increased operating temperature using a heat transfer medium, e.g. after an interruption of continuous operation of the plant due to maintenance work. After heating to operating temperature, the plant according to the invention can be operated in a production mode for the continuous production of H2. The invention further relates to a method for starting up a plant for producing H2 by catalytic decomposition of NH3.

Description

230085P00LU 12.07.2023

Start-up of a plant for the catalytic decomposition of ammonia LU103170

[0001] The invention relates to a plant for the production of Hz by catalytic decomposition of

NHz to Hz and Na. The plant according to the invention can be operated in a start-up mode in order to

Devices of the system can be heated to an increased operating temperature using a heat transfer medium, e.g. after an interruption of continuous operation of the system due to maintenance work. After heating to operating temperature, the system according to the invention can be operated in a production mode for the continuous production of H>. The invention further relates to a

Process for starting up a plant for the production of H> by catalytic decomposition of NH4.

[0002] Hz can be obtained from H2O using renewable energy and then converted into NH3 with N2. NH3 can be stored and transported much more safely than Hz. NH3 can then be broken down into Hz and N2 again. After separating N2, H2 can be used in a wide variety of industrial applications.

[0003] The decomposition of NH; to N> and H; is an endothermic reaction (AH° = 45.9 kJ-mol), in which the amount of substance doubles (2 NH; - Na + 3 Hz), so that the reaction is basically characterized by high

Temperatures and low pressures are favoured. The higher the pressure, the higher the

Temperature to achieve satisfactory reaction yields. In large-scale

The catalytic decomposition of NH; into N; and Hz at high temperature and medium

pressure in the gas phase.

[0004] Stored NH; is liquid in cooled tanks at atmospheric pressure and -32.8°C. NH; is fed into the system at system pressure using a pump. Due to the increased system pressure, the boiling point of the NH; rises, e.g. at 27.8 bar a to about 62.2°C. In order to convert NH; into the gas phase, heat must be added to evaporate the NH;. The evaporated NH; is then heated further until it has reached a sufficiently high temperature at which it can be

NH4 decomposition catalyst can be decomposed.

[0005] The known processes for the catalytic decomposition of NH; into N; and Hz require the supply of considerable amounts of heat. On the one hand, heat is required to heat the process gas and the NH;

To bring the decomposition catalyst to a sufficiently high temperature at which satisfactory

conversions can be achieved. On the other hand, heat is required to maintain the endothermic decomposition reaction.

[0006] In large-scale industrial processes, this heat is usually generated by the combustion of a

energy source (see e.g. US 4 704 267 A; FR 1 469 045 A; CN 111 957 270 A; CN 113 896 168 A; WO 2001/087770 A1; WO 2011/107279 A1; WO 2017/160154 A1; WO 2019/038251 A1;

WO 2012/039183 Al; WO 2012/090739 Al; WO 2020/095467 A; WO 2021/257944 A1; WO 2022/096529 Al; WO 2022/243410 Al; WO 2022/265647 Al; WO 2022/265648 Al; WHERE 1

230085P00LU 12.07.2023 2022/265649 A1; WO 2022/265650 A1; WO 2022/265651 A1). In principle, all energy sources come into consideration, e.g. natural gas or mixtures of NH; and Ho.

[0007] Plants for the production of Ha from NH; are usually operated continuously over longer periods

Periods of time without interruption, for example several weeks or months. Nevertheless, it is occasionally necessary to shut down such systems into a standby mode, for example to carry out safety checks, replace catalyst material or carry out other maintenance work. In the standby mode, the systems cool down to ambient temperature, depending on the length of the interruption in operation.

[0008] In order to bring such a system back into continuous operation from a standby state, it must first be warmed up to operating temperature; at room temperature, NH3 cannot be decomposed. Different parts of the system usually have different operating temperatures and therefore require warming up to different degrees. Warming up can basically be achieved by passing a heat transfer medium through the process side of the system, e.g. Na, water vapor, natural gas or mixtures thereof, and starting the combustion of the

The energy carrier is started in order to provide the heat for the heating process. Depending on its properties, the heat transfer medium can either be circulated in a circuit or burned off via a flare.

[0009] In order to reduce the use of fossil fuels or even to avoid them completely, part of the NH; is burned instead of fossil fuels during normal operation of the plant and the resulting combustion heat is used for the heating process. NH; is then on the one hand

Educt for the decomposition process, on the other hand energy carrier for the production of the necessary

Heat. However, NH; only burns incompletely when mixed with air, which is why the sole combustion of pure NH; together with combustion air is disadvantageous. The result would be emissions of unburned NHs, which would be unacceptable. In order to improve the combustion of NH; together with combustion air, a certain amount of generated H> is added to the portion of NH; to be burned during normal operation of the plant.

[0010] However, when starting up the plant, a major problem is that there is no

Hz is available as a decomposition product.

[0011] This problem could be solved for the duration of the start-up of the plant by temporary

The solution can be solved by two measures, which will be terminated once normal operation is achieved: (i) generating heat by combustion of natural gas or propane; this would not require H2 but would result in CO2 emissions; or (ii) providing H2 on a small scale and then burning the H2 in a mixture with

NHz, e.g. by 2

230085P00LU 12.07.2023 - Production of H2 using an electrically heated device for the catalytic decomposition LU103170 of NH3; - Production of H2 by electrolysis of water; or - Use of stored H2 retained from previous production.

[0012] However, these solution approaches have several disadvantages.

[0013] The alternative combustion of natural gas or propane would not only lead to undesirable emissions of CO2, but would also require dual operation in the combustion of the

Since the configuration of the burners typically has to be adapted to the energy source, changes to the configuration would have to be made when changing from natural gas/propane to NHs/H>, or a second, separate combustion device would have to be provided.

[0014] The temporary generation of Hz on a small scale by separate catalytic decomposition devices or electrolysis cells would require considerable additional equipment. This also applies to the storage of Hz, which would also be associated with significant safety problems.

[0015] WO 2011/150370 A2 relates to the decomposition of NH; into a H. gas mixture, wherein an NH;-rich gas mixture of NH; and air enters a line in which the combustion and decomposition of a part of the mixture is initiated, thereby releasing heat and Hz. Hz mixes with the main part of the gas mixture, and the released heat drives the combustion reaction. When starting the NH+ flame splitter, the catalyst can be activated electrically, inductively, by short-term

Combustion of chemicals on the catalyst and/or surrounding structure, or by an electric arc. Heating of the catalyst can be used to initiate the combustion and decomposition reactions of the NH; and to provide residual heat to the burning gases as needed until the NHs flamesplitter is fully warmed up. After starting the NHs flamesplitter, the power supply can be turned off or turned down so that the energy required to decompose the NH; is provided essentially by the combustion of a portion of the NH; and the combustion of NH; is essentially sufficient to keep the catalyst hot.

[0016] WO 2013/119281 A1 relates to the decomposition of NH3 into a H2-containing gas mixture, wherein a

A NH2-rich gas mixture of NH; and air enters a heat exchanger. Part of the NH; is burned, the rest is decomposed, which produces the H»-containing gas mixture. NHz-

Flame splitters are brought to operating temperature by burning a starting mixture and then flowing the burned starting mixture through the NHs flame splitters, so that the burned starting mixture thermally contacts the heat exchangers and/or burners of the NH; flame splitters during a starting phase. Since the surface temperatures during the warm-up phase 3

230085P00LU 12.07.2023 increase, one or more of the following measures can be taken: increasing the total flow of the starting mixture, reducing the oxygen content of the oxidizer component, or increasing the total content of the starting mixture. This allows the NHs flame splitters to be started quickly even with a comparatively low flow of purified oxygen. The

Purified oxygen supply is turned off at or near the end of the start-up phase.

[0017] The plants and processes known from the prior art for the production of H; from

NHz are not satisfactory in all respects, especially with regard to interruptions of the

Normal operation and the subsequent start-up of the plants. There is therefore a need for improved plants and processes that can be implemented economically on a large scale.

[0018] It is an object of the invention to provide an advantageous system and an advantageous method for

Production of Hz from NH; which overcome the above mentioned disadvantages.

The plant should be able to be started up without additional, costly measures and equipment, should not be based on any fossil fuels, should not entail any additional safety risks and should be economically viable and possible on a large technical scale.

[0019] This object is solved by the subject matter of the patent claims.

[0020] It was surprisingly found that certain devices which serve other purposes during normal operation of the plant can be converted and connected differently for the duration of the start-up. In this way, it is possible to obtain Hz in sufficient quantities from NH; by decomposition during the start-up of the plant, so that the combustion of NH; in a mixture with Hz can be started and the plant can be slowly warmed up to operating temperature. The additional equipment required for starting up the plant is thus minimized.

[0021] A first aspect of the invention relates to a plant for producing H from NH3; wherein the plant can be operated in a production mode (normal operation) at operating temperatures; wherein the plant can be operated in a start-up mode (start-up operation) in order to heat at least one device of the plant from an initial temperature to an operating temperature; wherein the plant for the start-up mode comprises at least the following devices for heating the at least one device to the operating temperature: - a heating element for heating NHs; - in the flow direction of the NH; downstream of the heating element, a first NH3: decomposition device (pre-reactor) for the partial catalytic decomposition of the heated NH; with the production of a

combustion gas comprising Hz, N; and remaining NH3; 4

230085P00LU 12.07.2023 - optionally, in the flow direction of the combustion gas downstream of the first NH3 decomposition device (pre-reactor), a device for metering combustion air into the combustion gas; - in the flow direction of the combustion gas downstream of the first NH3 decomposition device, a combustion device for burning the combustion gas to generate combustion heat and flue gas; - a compressor for compressing a heat transfer medium; and - in the flow direction of the flue gas downstream of the combustion device and in the flow direction of the heat transfer medium downstream of the compressor - a first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the

Start-up mode] and/or - a second heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] for heating the heat transfer medium by absorbing heat from the flue gas; and wherein the at least one device of the system is arranged in the flow direction of the heat transfer medium downstream of the first heat exchanger and/or the second heat exchanger and is in fluid communication with the heat transfer medium for absorbing heat from the heat transfer medium.

[0022] A second aspect of the invention relates to the use of a system according to the invention for

Production of Ho.

[0023] A third aspect of the invention relates to a method for starting up a plant for producing Hz from NH; comprising the following steps: (a) optionally, evaporating water to produce water vapor; (b) optionally, evaporating liquid NH; by absorbing heat from the water vapor; (c) heating NH3; (d) partial catalytic decomposition of the heated NH; in a first NH3 decomposition device to produce a combustion gas comprising Hz, N; and remaining NH3; (e) optionally, metering combustion air into the combustion gas; (f) burning the combustion gas in a combustion device to produce combustion heat and flue gas; (g) compressing a heat transfer medium; (h) heating the heat transfer medium by absorbing heat from the flue gas; and

230085P00LU 12.07.2023 (i) Heating at least one device of the system by absorbing heat from the heat transfer medium.

[0024] Steps (a), (b) and (e) of the method according to the invention are optional, independently of one another. Preferably, steps (a) to (i), if implemented, are carried out in alphabetical order.

[0025] According to the invention, a distinction is made between the production mode (normal operation) and the

Start-up mode (start-up operation). While Hz is already produced from NH3 to a certain extent in start-up mode, the amount and yield of Hz produced preferably differ considerably.

[0026] In the start-up mode, both the amount and the yield of H 2 produced are preferably comparatively low; preferably only the first NH 3 decomposition device is used for the partial catalytic decomposition of NH 3 and the intermediate product gas produced is burned as combustion gas to generate the required heat.

[0027] In the production mode, both the amount and the yield of produced NH3 are preferably comparatively high; preferably both the first NH3 decomposition device (pre-reactor) and the downstream second NH3 decomposition device (main reactor) are used for the most complete catalytic decomposition of NH3. The intermediate product gas produced in the first NH3 decomposition device is not burned as combustion gas, but is preferably fed after heating to the downstream second NH3 decomposition device, where the most complete decomposition of the NH3 takes place. From the gas produced in the second NH3 decomposition device

The product gas is then separated, preferably by pressure swing adsorption, and the remaining gas mixture is burned as combustion gas to generate the required heat. Since in practice the decomposition of the NH3 in the second NH3 decomposition device is not absolutely complete (100.0%), a residual amount of NH3 remains, which is burned as combustion gas after additional, fresh NH3 is added.

[0028] The heat exchangers according to the invention serve to transfer heat from one medium to another medium without the media being mixed together. For the purpose of description, in relation to an "A/B heat exchanger", the medium A that releases the heat is mentioned first, followed by the medium B that absorbs the heat. Accordingly, for example, a "flue gas/NH3 heat exchanger" serves to release heat contained in the flue gas to NH;. For this purpose, the flue gas/NH: heat exchanger is connected accordingly, i.e. its warmer side is

flue gas flows through it, whereas its cooler side is flowed through by NH:.

[0029] For the purpose of description, the heat exchangers are numbered. This numbering serves only as a linguistic distinction, but should not be understood to mean that the presence of a heat exchanger with a higher number, e.g. "fourth heat exchanger", always necessarily means the 6

230085P00LU 12.07.2023

Presence of all heat exchangers with lower numbers is required ("first heat exchanger", "second heat exchanger", "third heat exchanger"). For example, it is possible for the system according to the invention to comprise a second heat exchanger according to the invention and a fourth heat exchanger according to the invention, but neither a first heat exchanger according to the invention nor a third heat exchanger according to the invention.

[0030] It is possible and also preferred according to the invention that one and the same heat exchanger in the

Manufacturing mode may serve a different function than in start-up mode, in particular at least for

part or on one side (warm side vs. cold side) is flowed through by other media. In such

In some cases, for the purpose of description, a distinction is made in square brackets between the two operating modes and the respective preferred forms of heat exchange. For example, "first heat exchanger [preferably flue gas/NH3: heat exchanger for the production mode; flue gas/heat transfer medium heat exchanger for the start-up mode]" means that the first

Heat exchanger preferably takes on two different functions: In the production mode, the first heat exchanger prefers to transfer heat from the flue gas to NH; in the start-up mode, the first heat exchanger prefers to transfer heat from the flue gas to the heat transfer medium. If in the

If the heat transfer medium in the start-up mode is NH3, it is ultimately a flue gas/NH3 heat exchanger in the start-up mode. If such a heat exchanger is described in the context of a specific mode (either production mode or start-up mode), the square brackets after it may only refer to the associated preferred form of heat exchange.

[0031] For the purpose of description, the term "water", unless expressly stated otherwise, is used for all its states of aggregation, whereby, depending on temperature and pressure, this water can be liquid or gaseous or as a two-phase system, i.e. possibly also as

Water vapor. This also applies to "NH3".

[0032] The plant according to the invention comprises a first NHz decomposition device and a second

NH3 decomposition device, both of which contain NH3 decomposition catalyst. The first NH3 decomposition device is preferably a fixed bed reactor. In the first NH3 decomposition device, the decomposition of NH; preferably takes place adiabatically. The downstream second NH3; decomposition device is preferably designed together with a combustion device analogous to a primary reformer, as is used in conventional steam reforming to produce H2, O2 and CO/CO» from HO and

CH, is used.

[0033] In the production mode, the catalytic decomposition of NH occurs in two stages in the first NH2

decomposition device and the downstream second NH3 decomposition device. Preferably, the second heat exchanger [preferably flue gas/intermediate product gas heat exchanger for the production mode] is arranged in the flow direction of the NH3; downstream of the first NH3 decomposition device and preferably upstream of the downstream second NH3 decomposition device. In the production mode, the second heat exchanger preferably serves to heat the intermediate product gas after 7

230085P00LU 12.07.2023 leaving the first NHz decomposition facility and before entering the downstream second LU103170

NH4 decomposition facility (main reactor, together with combustion facility analogous to primary reformer). In production mode, intermediate product gas preferentially absorbs heat from flue gas in the second heat exchanger (see Figure 2, second heat exchanger 67).

[0034] In the production mode, preheated NH; enters the first NH3; decomposition device, in which a partial catalytic decomposition of NH; to N; and Hz takes place to a certain extent. An intermediate product gas is formed, which still contains considerable residual amounts of non-decomposed NH3, but also already formed N> and Hz. As a result of the endothermic decomposition of NH;, the

Intermediate product gas preferentially. Preferably, the conversion of decomposed NH; in the first

NH 3 decomposition device is at most 25%, more preferably at most 20% of the total conversion achieved. Preferably, the conversion of decomposed NH 3 in the first NH 3 decomposition device is at least 5%, more preferably at least 10%, even more preferably at least 15% of the total conversion achieved. After leaving the first NH 3 decomposition device, the intermediate product gas is preferably in the second heat exchanger [preferably flue gas/intermediate product gas-

Heat exchanger for the production mode] is heated again before it is fed into the downstream, second NHz

decomposition device. The remaining decomposition then takes place in the second NHz decomposition device.

Decomposition of NH; until the total conversion is achieved.

[0035] In contrast, in the start-up mode, the catalytic decomposition of the NH; preferably only takes place in one stage, and only in the first NH3 decomposition device. In the start-up mode, the second NH3 decomposition device preferably does not yet contribute to the decomposition of NH;, at least during early phases of the start-up mode.

[0036] In the start-up mode, preheated NH; enters the first NHs decomposition device, in which a partial catalytic decomposition of NH; to N; and H 2 takes place to a certain extent. An intermediate gas is also formed, which still contains considerable residual amounts of undecomposed

NH3, but also already formed N, and Hz. Preferably, the conversion of decomposed NH; in the first NHs decomposition device is at most 25%, more preferably at most 20% based on the

Amount of NH3. Preferably, the conversion of decomposed NH3 in the first NH3 decomposition device is at least 5%, more preferably at least 10%, even more preferably at least 15% based on the amount of NH3.

[0037] In contrast to the production mode, in the start-up mode the intermediate product gas formed in the first NH 3 decomposition device is preferably not passed into the second NH 3 decomposition device, but instead into the combustion device. The intermediate product gas contained in the

The amount of H> formed is sufficient for a satisfactory combustion of the NH;, so that the

Combustion of the intermediate gas produces sufficient combustion heat to gradually warm the system up to operating temperature. 8

230085P00LU 12.07.2023

[0038] In preferred embodiments, in the start-up mode, the NH; stream is converted into a first NH3- LU103170

partial flow and a second NHz partial flow. Only the first NHz partial flow is added to the first

decomposition device. The second NH3 partial flow instead flows through the second NHs

decomposition device, whereby the second NHz decomposition device extracts heat from the second

NH3 partial flow. The second NH3 partial flow therefore initially only functions as a heat transfer medium. In this way, the second NH3; decomposition device is gradually heated until the start-up temperature (activation temperature) for the catalytic decomposition of NH; is reached, so that from this point on additional H> is produced in the second NHs decomposition device by catalytic decomposition of NH; (see Figure 3).

[0039] In preferred embodiments, the amount of Hz in the combustion gas is increased in the start-up mode compared to the production mode. Due to the larger ratio of Hz to NH;, the

Combustion is promoted, allowing the operating temperature to be reached more quickly.

[0040] It is a significant advantage of the invention that the first NHs decomposition device can be used for two different purposes, namely in start-up mode for the production of the

combustion gas and in production mode for the first stage of a total of two-stage decomposition of NH; for the production of the product gas. The plant according to the invention preferably does not comprise any further separate NH3 decomposition device, which is used exclusively in start-up mode, but not in production mode. Such separate NH3 decomposition devices are commercially available, possibly already equipped with an electric heater, but even such additional equipment expenditure can be dispensed with according to the invention.

[0041] Preferably, the system according to the invention essentially comprises only two devices, which are used exclusively in the start-up mode, but not in the production mode, namely - the preferably electrically operated heating element and - the preferably electrically operated H>O steam generator.

[0042] So that the NH; has a sufficiently high temperature for the catalytic decomposition in the first NH3 decomposition device, the system according to the invention has a heating element for heating NH; for the start-up mode. The heating element is preferably electrically operated. The heating of NH; in step (c) of the method according to the invention preferably takes place using electrical energy.

[0043] Preferably, the heating element is only intended for the start-up mode and is switched off in the production mode. In preferred embodiments, the heating element is connected via a line system in a

Bypass connected so that the NH; can be led through the heating element via the bypass in start-up mode to be heated there. Once the production mode is reached, the 9

230085P00LU 12.07.2023 the entire bypass including the heating element is no longer flowed through by NH;. In order to enable such a reaction, suitable valves are preferably provided which enable the targeted flow of NH; through the bypass or not through the bypass.

[0044] The NH; is typically provided in liquid form as a starting material and must therefore first be evaporated. This applies not only to the production mode, but also to the start-up mode. According to the invention, the NH; is preferably evaporated by absorbing heat from water vapor.

[0045] In the production mode, the water vapor is preferably provided by process heat by

Water as a heat transfer medium absorbs heat from the product gas and/or the flue gas and the heated water vapor releases heat to liquid NH;.

[0046] In the start-up mode, however, there is initially no process heat present, so that the system according to the invention preferably comprises an H:O evaporation device for evaporating water to produce water vapor. The H:O evaporation device is preferably arranged in the flow direction of the NH; upstream of the heating element. The H>O evaporation device is preferably heated electrically. The method according to the invention therefore preferably comprises the two optional steps (a) and (b), with the generation of water vapor in step (a) of the method according to the invention preferably taking place using electrical energy.

[0047] Preferably, the preferably electrically heated H:O evaporation device is only provided for the start-up mode and is switched off in the production mode. In preferred embodiments, the H:O evaporation device is connected via a line system in a bypass, so that the

Water can be passed through the H>O evaporation device via the bypass in the start-up mode to be heated and evaporated there. Once the production mode is reached, the entire bypass, including the H:O evaporation device, is preferably no longer flowed through by water. In order to enable such a reaction, suitable valves are preferably provided which allow the targeted flow of water through the bypass or not through the

bypass through.

[0048] Furthermore, the plant according to the invention preferably comprises an NH 3 evaporation device for evaporating liquid NH 3 by absorbing heat from the water vapor.

[0049] In this way, in the start-up mode, the liquid NH; can first be evaporated by

absorbs heat from the water vapor, which in turn is heated in the preferably electrically heated H:O

evaporation device. The evaporated NH; is then passed through the preferably electrically heated heating element and heated therein to a temperature which is sufficient for the subsequent partial catalytic decomposition of the NH; in the first NH3 decomposition device. The intermediate product gas thus produced is then burned in the combustion device and in the process produces a flue gas and combustion heat.

230085P00LU 12.07.2023

[0050] According to the invention, the heat generated by the combustion of the combustion gases is not only used in the production mode, but also in the start-up mode. The combustion gases can typically have different origins and compositions.

[0051] In the production mode, the heat of combustion essentially serves to heat the NH; to the necessary reaction temperature so that the reaction heat of the endothermic reaction is provided in the first NH3 decomposition device and the downstream second NH3 decomposition device and the conversion takes place via both NH3 decomposition devices with a high conversion. For this purpose, water vapor is preferably used as a heat transfer medium, in particular for the evaporation of the NH;.

[0052] In start-up mode, the combustion heat essentially serves to heat a heat transfer medium, which is preferably compressed in a compressor and then passed through parts of the

system. To do this, the heat transfer medium preferably absorbs heat directly from the heat of combustion and/or indirectly from the flue gas. To do this, preferably in the flow direction of the flue gas downstream of the combustion device and in the flow direction of the heat transfer medium downstream of the compressor - the first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] and/or - the second heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] is arranged to heat the heat transfer medium by absorbing heat from the flue gas.

[0053] In preferred embodiments, the heat transfer medium comprises Na or consists essentially of it. Na is preferably circulated through at least part of the system until the desired operating temperatures of the parts of the system are reached. Once this state has been reached, N; is preferably discharged from the system and switched to the production mode. For this

Alternately, NH; is preferably continuously added to the N; and the mixture of N; and NH; is burned using a torch if necessary. If the content of NH; in the mixture with N; is large enough, the production mode can begin.

[0054] In other preferred embodiments, the heat transfer medium comprises NH; or consists essentially of it. NH; is preferably circulated through at least part of the system until the desired operating temperatures of the parts of the system are reached. If this

Once this state is reached, the manufacturing mode begins.

[0055] In preferred embodiments, in the start-up mode, the NH3 stream is converted into a first NHs

partial flow and a second NHz partial flow. Only the first NHz partial flow is added to the first

decomposition device. The second NH3 partial flow instead flows through the second NHs

decomposition device, whereby the second NHz decomposition device extracts heat from the second 11

230085P00LU 12.07.2023

The second NH3 partial flow initially only functions as a heat transfer medium. In this way, the second NH3; decomposition device is gradually heated until the start-up temperature (activation temperature) for the catalytic decomposition of NH; is reached, so that from this point on additional H> is produced in the second NHs decomposition device by catalytic decomposition of NH;.

[0056] In preferred embodiments, the amount of Hz in the combustion gas is increased in the start-up mode compared to the production mode. Due to the larger ratio of Hz to NH;, the

Combustion is promoted, allowing the operating temperature to be reached more quickly.

[0057] In the start-up mode, at least one device of the system is arranged in the flow direction of the heat transfer medium downstream of the first heat exchanger and/or the second heat exchanger and is in fluid communication with the heat transfer medium for absorbing heat from the heat transfer medium. This at least one device of the system is activated in the start-up mode by

Absorption of heat from the heat transfer medium.

[0058] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the heat transfer medium is the second NH3 decomposition device (see Figure 2, second NH3 decomposition device 24). In the production mode, the second NH3 decomposition device is preferably connected downstream of the first NH3 decomposition device and is preferably used for the catalytic decomposition of vaporized NH3, producing a product gas comprising H2 and Na. For the change from the start-up mode to the production mode, the system according to the invention preferably comprises corresponding lines and valves which enable a changed connection (see Figure 2).

[0059] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the heat transfer medium is a third heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] (see Figure 2, third heat exchanger 26). In the production mode, the third heat exchanger [preferably product gas/water heat exchanger for the production mode] is preferably used to heat water, preferably to heat or generate water vapor, by absorbing heat from the product gas.

For the change from start-up mode to production mode, the system according to the invention preferably comprises corresponding lines and valves which enable a changed connection (see Figure 2).

[0060] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the heat transfer medium is a fourth heat exchanger [preferably heat transfer medium/heat transfer medium heat exchanger for the start-up mode] (see Figure 2, fourth heat exchanger 20). In the production mode, the fourth heat exchanger [preferably product gas/NH: heat exchanger for the production mode] is used to heat NH; by absorbing 12

230085P00LU 12.07.2023 of heat from the product gas. For the change from start-up mode to production mode, the LU103170 system according to the invention preferably comprises corresponding lines and valves which enable a changed connection (see Figure 2).

[0061] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the heat transfer medium is a fifth heat exchanger [preferably a heat transfer medium/water heat exchanger for the start-up mode] (see Figure 2, fifth heat exchanger 28). In the production mode, the fifth heat exchanger [preferably a product gas/water heat exchanger for the production mode] is preferably used to heat water by absorbing heat from the product gas. For the change from the start-up mode to the production mode, the system according to the invention preferably comprises corresponding lines and valves which enable a changed connection (see Figure 2).

[0062] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the heat transfer medium is a sixth heat exchanger [preferably a heat transfer medium/water heat exchanger for the start-up mode] (see Figure 2, sixth heat exchanger 29). In the production mode, the sixth heat exchanger [preferably a product gas/water heat exchanger for the production mode] is preferably used to heat water by absorbing heat from the product gas. For the change from the start-up mode to the production mode, the system according to the invention preferably comprises corresponding lines and valves which enable a changed connection (see Figure 2).

[0063] In addition, in start-up mode, the flue gas generated during combustion of the

Combustion gas is generated, release heat to at least one device of the system. This at least one device is typically arranged in the flue gas duct. This at least one device is preferably arranged in the flow direction of the flue gas downstream of the first heat exchanger and/or the second heat exchanger.

[0064] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the flue gas is a first flue gas/combustion air heat exchanger (see Figure 2, first flue gas/combustion air heat exchanger 45), which is preferably used in the start-up mode and/or in the production mode for heating combustion air by

absorbing heat from the flue gas.

[0065] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the flue gas is a flue gas denitrification unit (see Figure 2, flue gas denitrification unit 50), which is preferably in the start-up mode and/or in the

Production mode for cleaning the flue gas from nitrogen oxides (NOx). 13

230085P00LU 12.07.2023

[0066] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the flue gas is a flue gas/water heat exchanger (see Figure 2, flue gas/water heat exchanger 52), which is preferably used in the start-up mode and/or in the production mode for heating water, preferably for heating or producing

Water vapor, by absorbing heat from the flue gas.

[0067] In preferred embodiments, the at least one device which is heated in the start-up mode by absorbing heat from the flue gas is a second flue gas/combustion air heat exchanger (see Figure 2, second flue gas/combustion air heat exchanger 43), which preferably serves in the start-up mode and/or in the production mode to heat combustion air by absorbing heat from the flue gas.

[0068] Preferably, the combustion device and the second NH3 decomposition device are in heat exchange with each other and are configured for a heat flow from the combustion device into the second NH3 decomposition device. For this purpose, they are preferably designed analogously to a primary reformer, as is used in conventional steam reforming to produce Hz, O> and

CO/CO- from H:0 and CH, is used.

[0069] In preferred embodiments of the plant according to the invention, the plant in production mode (i.e. during normal operation) is designed for a throughput based on H> of at least 500 mol-h!, preferably at least 1000 mol-h!, more preferably at least 5000 mol-h", even more preferably at least 10,000 mol-h!, most preferably at least 50,000 mol-h!, and in particular at least 100,000 mol-h".

[0070] In preferred embodiments of the system according to the invention, the system comprises a

Tank for liquid NH3, which has a volume of at least 50 m°, preferably at least 100 m', more preferably at least 500 m?, even more preferably at least 1000 m?, most preferably at least 5000 m?, and in particular at least 10,000 m'.

[0071] In preferred embodiments of the plant according to the invention, the plant comprises, in addition to the first NH3 decomposition device, a second NHs decomposition device with at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven and in particular at least eight catalyst beds, each comprising NHs decomposition catalyst; each catalyst bed preferably being in a

tube; the catalyst beds are preferably connected in parallel. Preferably, each

Catalyst bed contains the same NH3 decomposition catalyst.

[0072] In preferred embodiments of the plant according to the invention, the plant comprises, in addition to the first NH3 decomposition device, a second NHs decomposition device with at least one catalyst bed which comprises NH3; decomposition catalyst, the length of the catalyst bed in the flow direction for NH; being at least 1.0 m, preferably at least 1.5 m, 14

230085P00LU 12.07.2023 more preferably at least 2.0 m, even more preferably at least 2.5 m, most preferably at least 3.0 LU103170 m and in particular at least 3.5 m; wherein the catalyst bed is preferably present in a tube.

[0073] In preferred embodiments of the system according to the invention, the system comprises a

Combustion device with at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven and in particular at least eight burners for combustion of the combustion gas.

[0074] In preferred embodiments of the system according to the invention, the system comprises a first heat exchanger and/or a second heat exchanger, which are independently of one another as

tube heat exchangers or tube bundle heat exchangers.

[0075] In preferred embodiments of the process according to the invention, in the production mode (i.e. during normal operation), a throughput based on H> of at least 500 mol-h" is achieved, preferably at least 1000 mol-h!, more preferably at least 5000 mol-h!, even more preferably at least 10,000 mol-h"!, most preferably at least 50,000 mol-h!, and in particular at least 100,000 mol-h!.

[0076] In preferred embodiments of the process according to the invention, in the production mode (i.e. during normal operation), the liquid NH3 is taken from a tank with a volume of at least 50 m3, preferably at least 100 m3, more preferably at least 500 m3, even more preferably at least 1000 m3, most preferably at least 5000 m3, and in particular at least 10,000 m3.

[0077] In preferred embodiments of the process according to the invention, the catalytic decomposition of NH takes place in the production mode (i.e. during normal operation) on at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven and in particular at least eight catalyst beds, each of which comprises NH s decomposition catalyst; each catalyst bed preferably being present in a tube; the

Catalyst beds are preferably flowed through in parallel by NH;

[0078] In preferred embodiments of the process according to the invention, in the production mode (i.e. during normal operation), the catalytic decomposition takes place on at least one catalyst bed, which

NH 3 decomposition catalyst, wherein the length of the catalyst bed in the flow direction for NH 3 is at least 1.0 m, preferably at least 1.5 m, more preferably at least 2.0 m, even more preferably at least 2.5 m, most preferably at least 3.0 m and in particular at least 3.5 m; wherein the catalyst bed is preferably present in a tube

[0079] In preferred embodiments of the method according to the invention, in the production mode (i.e. during normal operation), the combustion of the combustion gas takes place with the aid of at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven and in particular at least eight burners.

[0080] According to the invention, the catalytic decomposition of NH; means the formation of N; and Ha, in

State of the art sometimes also referred to as "cleavage" or "cracking" of NH;.

230085P00LU 12.07.2023

[0081] The catalytic decomposition of NH; is preferably carried out in the absence of LU103170

Os.

[0082] Preferably, the invention comprises the following measures in the production mode: (i) evaporation of NH3; (ii) catalytic decomposition of NH3 with supply of heat to obtain a product gas comprising N3, H3 and optionally undecomposed NH3; (iii) recovery of heat; (iv) optionally recovery of undecomposed NH3; (v) purification of Ha.

[0083] HO is not a product of the reaction and can be present in very small amounts, since H:O is often present in liquid NH3, in concentrations of maximum 0.5 wt.%, typically < 0.3 wt.%. Due to the evaporation of NH; it is to be expected that H>O is present in lower concentrations.

NH; - from storage to catalytic decomposition

[0084] According to the invention, the NH; is preferably stored as starting material.

[0085] Preferably, the stored NH; is in liquid form in a cooled tank, at atmospheric pressure and at a temperature below its boiling point of -33.5°C. NH; is fed into the system using a pump, preferably at system pressure.

[0086] Before the NH3 can be catalytically decomposed, it is preferably heated successively to several temperature levels according to the invention.

[0087] Starting from liquid NH;, NH; is preferably heated and then evaporated to a medium temperature level (<300°C) by absorbing heat from water or water vapor. In the production mode, the water vapor is preferably generated by absorbing heat from flue gas and/or product gas. In the start-up mode, the water vapor is preferably generated by an electrically operated H>O evaporation device.

[0088] Preferably, in the flow direction of the NH; downstream of the tank and upstream of the

A preheater is arranged in the NH 2 evaporator, which preferably serves to heat the NH 3 to the desired temperature at the inlet to the NH 2 evaporator and in which

NH; absorbs heat from water, which in turn previously passed the NH3 evaporation device as

Water vapor condensate has left. Water vapor and water vapor condensate are preferred in the

Countercurrent through the preheater and the NH: evaporator.

[0089] This is followed preferably by further heating of the NH to a high temperature level (>300°C). 16

230085P00LU 12.07.2023

[0090] In the production mode, the further heating of NH is preferably carried out by absorption of heat directly from flue gas and/or product gas, i.e. without water as a heat transfer medium.

[0091] For this purpose, appropriate heat exchangers are provided for the production mode: - preferably a fourth heat exchanger [preferably product gas/NH: heat exchanger for the production mode]; - preferably a first heat exchanger [preferably flue gas/NH: heat exchanger for the production mode]; and/or - preferably a second heat exchanger [preferably flue gas/intermediate product gas heat exchanger for the production mode].

[0092] In start-up mode, further heating of NH occurs, preferably by absorption of heat from an electrical heating element.

[0093] In order for the vaporized NH; to be catalytically decomposed in start-up mode, it must be

activation temperature of the NHs decomposition catalyst.

[0094] In preferred embodiments, the NH3; decomposition catalyst is nickel-based and the

Heating of the vaporized NH; occurs to a temperature in the range of preferably 600 to 650°C.

[0095] In other preferred embodiments, the NH3: decomposition catalyst is ruthenium-based and the vaporized NH3 is heated to a temperature in the range of preferably 350 to 400°C.

[0096] In all of these embodiments, NH; (part or all of the amount) is passed through the electrical heating element and heated therein above the activation temperature of the NH 2 decomposition catalyst in the first NH 2 decomposition device. The heated NH; then flows into the first NH s decomposition device, where the NH; is at least partially decomposed. In the preferably adiabatic reaction, a conversion of e.g. 18% can be achieved, depending on the preheating temperature.

NH; - catalytic decomposition

[0097] The catalytic decomposition of NH; according to the invention is the actual reaction for the formation of Ha, which basically takes place thermally, but is accelerated by the use of an NH3; decomposition catalyst. The catalytic decomposition of NH; can be carried out according to the invention under different conditions using different NHs decomposition catalysts and with different connections with different reactor types. 17

230085P00LU 12.07.2023

[0098] According to the invention, the catalytic decomposition of NH is preferably carried out by supplying LU103170

Heat in the presence of an NH3 decomposition catalyst. Important parameters for the catalytic decomposition of NH3 are the type of NH3 decomposition catalyst, the reaction temperature and the reaction pressure.

[0099] According to the invention, various materials can be considered as NH 2 decomposition catalyst. The reaction temperature at which the catalytic decomposition of NH 3 takes place is determined in particular by the choice of the NH 3 decomposition catalyst.

[0100] In preferred embodiments of the invention, a nickel-based NH3 decomposition catalyst is used. The reaction temperature and the reaction pressure determine the equilibrium conversion. At 900°C and 20 bar pressure, the decomposition of NH3 is almost quantitative. At 650°C, the conversion of NH3 is about 98.5%, at 500°C only about 95%. According to the invention, reaction temperatures are preferably set in the range from about 600°C to about 900°C, preferably about 600°C to about 700°C, so that a high conversion is achieved. With regard to energy balance and

Optimum reaction temperatures are in the range of about 630°C to 640°C. Nickel-based

NH4 decomposition catalysts are advantageous despite the comparatively high reaction temperature.

Due to the high conversion, the remaining content of non-decomposed NH; in the product gas is comparatively low, so that separate separation of non-decomposed NH; for its recovery is preferably avoided. Instead, Na and non-decomposed NH; are separated together from the product gas by pressure swing adsorption during the purification of H;.

[0101] Preferably, the NH 2 decomposition catalyst comprises supported nickel. Preferred support materials are selected from the group consisting of Al 2 O 3 , MgO, SiO 2 , mesoporous SiO 2 (e.g.

MCF-17, MCM-41, SBA-15), zeolite (e.g. HY, H-ZSM-5), BaMnOs3, BaTiOs, BaZrO3, CaMnOs, Ca-

TiO3, CaZrO3, CeOz, Gd:O3, GdA103;, KNbO3, La:O3, LaAIO3;, MnO», NaNbO;, Nb,Os, Sm2Os,

SMAIO3, SrMnO3, SrTiOs, SrZrO3, TiO», Y2O3, ZrO», carbon (e.g. CNTs, SWCNTs, AX-21,

MSC-30, MESO-C, GNP, activated carbon, graphene, graphene oxide), attapulgite, hydrocalumite, sepiolite, and

mixtures thereof.

[0102] In other preferred embodiments of the invention, a ruthenium-based NHs-

decomposition catalyst is used. For this purpose, according to the invention, reaction temperatures in the range of about 450°C to about 500°C are preferably set, although somewhat lower conversions of, for example, about 95% can be achieved, so that the remaining residual content of non-decomposed NH; in the product gas is greater. 18

230085P00LU 12.07.2023

[0103] Alternatively, other NH3 decomposition catalysts can also be used at even lower reaction temperatures. The lower the reaction temperature, the lower the conversion and the more non-decomposed NH3 must be separated from the product gas and recycled.

[0104] In preferred embodiments, the first NHs decomposition device comprises two catalyst beds connected in series, of which one catalyst bed contains an NH3 decomposition catalyst with a comparatively high activation temperature (preferably a first nickel-based NH3 decomposition catalyst) and the other catalyst bed contains an NH: decomposition catalyst with a comparatively low activation temperature (preferably a second nickel-based NH3 decomposition catalyst). NH3 decomposition catalysts with different activation temperatures are known to a person skilled in the art (cf. e.g. I. Lucentini et al., Ind. Eng. Chem. Res. 2021, 60, 51, 18560-18611). According to the invention, NH3 decomposition catalysts are preferably used on

Based on iron, ruthenium, nickel, cerium, cobalt, chromium, iridium, copper, platinum, molybdenum, palladium,

Zirconium, tungsten and/or vanadium; more preferably based on nickel, iron and/or cerium.

[0105] In the start-up mode, the catalytic decomposition of the NH preferably takes place; in particular on the NH3 decomposition catalyst with the comparatively low activation temperature (preferably a second nickel-based NH3 decomposition catalyst). In the production mode, however, the catalytic decomposition of the NH preferably takes place first; in particular on the NH3 decomposition catalyst with the comparatively high activation temperature (preferably a first nickel-based

NH3 decomposition catalyst), and optionally additionally or subsequently on the NH3 decomposition catalyst with the comparatively low activation temperature (preferably a second nickel-based NH3 decomposition catalyst).

[0106] According to the invention, the reaction pressure is preferably about 15 bar a to about 25 bar a. The

The stoichiometry of the reaction (2 NH; - N; + 3 Hy) increases the volume, which is why an increased reaction pressure generally has a negative effect on the conversion. On the other hand, it is sensible to operate the entire process at higher pressures in order to limit the container volume and thus the investment costs. With a reaction pressure of only 1 bar, conversions of more than 99% could be achieved at reaction temperatures from 400°C. However, since a reaction pressure of 1 bar is only sensible for very small systems, the system according to the invention is preferably operated at a higher reaction pressure, even if this means a certain loss in conversion.

[0107] The reaction pressure is particularly determined by the execution of the purification of

Ha. The pressure swing absorption (PSA) preferred according to the invention for purifying Hz can preferably be operated effectively at a pressure in the range from about 15 bar to about 25 bar. The pressure of the product gas when leaving the second NHz decomposition device is preferably in the range from about 15 to about 25 bar a, more preferably about 18 bar a to about 22 bar a, even more preferably about 19 bar a to about 21 bar a. In this way, a good balance is found 19

230085P00LU 12.07.2023 between the requirements of pressure swing adsorption on the one hand and the achieved sales on the other.

[0108] The decomposition of NH3 can basically take place in different reactor types.

[0109] In adiabatic reaction, the internal heat of the reaction gas is used as an energy source for the reaction. Suitable reactors for this are autothermal reformers and secondary reformers, which work with internal energy generation. Combustion air is added to the process gas and part of the reaction gas is burned in order to increase the temperature so that the desired temperature prevails at the reactor outlet. A disadvantage is the presence of water in the process gas that is produced during combustion and must be removed by condensation. Part of the non-decomposed NH; then dissolves in the condensed water and is lost or must be recycled.

In addition, the high temperatures lead to the formation of significant amounts of nitrogen oxides.

[0110] According to the invention, these disadvantages are avoided by physically separating the product gas from the combustion gas and the flue gas formed therefrom.

[0111] In the production mode, the decomposition of NH; according to the invention preferably takes place in two stages in two NHs decomposition devices through which the gas flows one after the other. In the first NH3 decomposition device, initially only a portion of the NH; is partially decomposed. The remaining decomposition of NH; up to the maximum conversion achieved then takes place in the second NH3 decomposition device. For this purpose, the second NHs decomposition device together with the combustion device according to the invention preferably forms a reactor, as described in more detail above, designed analogously to a primary reformer.

[0112] In the start-up mode, the decomposition of NH according to the invention is preferably carried out in one stage, namely only in the first NH s decomposition device, which may optionally comprise several catalyst beds connected in series.

[0113] In both operating modes, the preheated NH3 enters the first NH3 decomposition device, which contains NH3 decomposition catalyst and in which a partial catalytic decomposition of NH3 to N3 and H2 takes place to a certain extent. An intermediate product gas is formed which still contains considerable residual amounts of non-decomposed NH3, but also Na and H2 that have already been formed.

As a result of the endothermic decomposition of NH;, the intermediate product gas cools preferentially. Preferably, the conversion of decomposed NH; in the first NH3 decomposition device is at most 25%, more preferably at most 20% of the total conversion achieved overall. Preferably, the conversion of decomposed NH; in the first NH2 decomposition device is at least 5%, more preferably at least 10%, even more preferably at least 15% of the total conversion achieved overall.

[0114] After leaving the first NH 2 decomposition device, the intermediate gas is

Operating mode used differently.

230085P00LU 12.07.2023

[0115] In start-up mode, the intermediate gas is mixed with NH; if necessary and then in the LU103170

Combustion facility with supply of combustion air.

[0116] As already mentioned, in preferred embodiments in the start-up mode the NHs stream is divided into a first NH3 partial stream and a second NH3 partial stream. Only the first NHs partial stream is fed to the first decomposition device. Instead, the second NH3 partial stream flows through the second NH3 decomposition device, whereby the second NHs decomposition device absorbs heat from the second NH3 partial stream. The second NHs partial stream therefore initially only functions as a heat transfer medium. In this way, the second NH3 decomposition device is gradually heated until the start-up temperature for the catalytic decomposition of NH3 is reached, so that from this point on additional NH3 is produced in the second NHs decomposition device by catalytic decomposition of NH3. For example, it is possible for the first NH3 partial stream of the first

NH3 decomposition device and the entire intermediate product gas produced (e.g. at 20% conversion: 20 mol% Hz + N; and 80 mol% undecomposed NH3) is completely burned in the combustion device. The second NHs partial stream is neither fed to the first NH3 decomposition device nor burned, but is preferably used as a heat transfer medium, preferably circulated for this purpose, and is preferably used, among other things, to heat the second NH3 decomposition device.

[0117] In the production mode, the intermediate product gas is preferably heated again before it enters the downstream, second NH3 decomposition device. The remaining decomposition of NH3 then takes place in the second NH3 decomposition device until the total conversion is achieved.

[0118] In the production mode, the product gas is formed in the second NH3 decomposition device according to the invention by decomposition of NH; and leaves the second NHs decomposition device via its own outlet. The combustion gas is burned together with combustion air in the combustion device and the flue gas formed thereby also leaves the combustion device via its own outlet, preferably into a flue gas channel. Product gas and flue gas are not mixed with one another, but remain physically separated from one another. Combustion heat formed during the combustion of the combustion gas flows as a heat flow into the second

NH4 decomposition facility and thus provides the heat required to maintain the endothermic decomposition of NH4.

[0119] In preferred embodiments of the invention, the catalytic decomposition of NH; takes place in the production mode in the second NH3 decomposition device analogously to a primary reformer. For this purpose, the analog primary reformer comprises both the second NH3 decomposition device according to the invention and the combustion device according to the invention. For this purpose, the NH3 decomposition catalyst is preferably arranged in the second NH3 decomposition device according to the invention in at least one tube through which NH; flows, more preferably at least two tubes, even more preferably at least three tubes. The at least one tube contains the NH3 decomposition catalyst. The at least one 21

230085P00LU 12.07.2023

NH; preferably flows through the pipe from top to bottom. In a physically separate combustion chamber, a mixture of NH; and Hz is preferably burned together with combustion air as combustion gas (combustion device). The gas produced during the catalytic decomposition of NH; in addition to

The N> formed in the combustion chamber of the combustion device is inert and serves as an additional heat carrier. The combustion heat generated by the combustion process in the combustion chamber of the combustion device is used to heat the second NHs decomposition device, preferably the pipe or pipes through which the NH; to be decomposed is passed. For this purpose, a heat flow is passed from the combustion device into the second NHs decomposition device.

[0120] The NH3 decomposition catalyst in the first NH3 decomposition device is preferably the same as in the second NH3 decomposition device. If the first NH3; decomposition device comprises several catalyst beds connected in series, preferably at least one of these catalyst beds connected in series contains the same NH3 decomposition catalyst as the second

NH3 decomposition device.

combustion gas

[0121] According to the invention, heat is provided by combustion of a combustion gas in a combustion device. The combustion device preferably has one or more

burners, preferably at least two burners, more preferably at least three burners.

[0122] The combustion gas preferably contains NH3. This applies in particular to the start-up mode. The combustion device according to the invention is therefore preferably an NH3 combustion device.

[0123] The combustion gas preferably contains a mixture of H2 and NH3, since this mixture produces a medium flame temperature and has better combustion properties than pure NH3. A suitable mixing ratio of H2 and NH3 also results in less nitrogen oxide being formed than in the absence of H2.

[0124] In the production mode, the residual gas mixture which remains after the separation of Hz from the product gas, preferably by pressure swing adsorption, is preferably used as the combustion gas. Fresh NH; is preferably added to this residual gas mixture. Since the pressure swing adsorption typically does not separate the complete amount of Hz from the product gas, the remaining

Residual amount of Hz in the residual gas mixture preferred as a combustion improver for the NHs.

[0125] The intermediate product gas formed in the first NH3 decomposition device in the start-up mode contains H> and is optionally mixed with further NH; and burned in the start-up mode in the combustion device to form flue gas. Due to the at least partial decomposition of NH2, a sufficient amount of H» is available to ensure or improve the combustion of the NH;. 22

230085P00LU 12.07.2023

[0126] In start-up mode, the preferably electrically operated H2O evaporation device LU103170 and the electric heating element require electrical energy to evaporate and further heat the

NH3 for the catalytic decomposition; the subsequent combustion of NH3 together with the Hz formed by the catalytic decomposition then provides the heat to heat the heat transfer medium.

[0127] As already mentioned, in preferred embodiments in the start-up mode the amount of

Hz in the combustion gas compared to the production mode. Due to the higher proportion of Hz in the

Combustion gas promotes the combustion of the mixture of NH; and H>, whereby the operating temperature can be reached more quickly. Accordingly, the process according to the invention is preferably operated in the production mode at a Ha proportion A; and in the start-up mode at a Hz-A proportion A», where A» > Ay. In preferred embodiments, the relative difference between

Az and A; at least 1 vol.%, more preferably at least 2 vol.%, even more preferably at least 3 vol.%, most preferably at least 4 vol.%, and especially at least 5 vol.%.

[0128] The person skilled in the art will recognize that the state during the start-up mode does not have to be statically constant, but can change dynamically, particularly in view of the continuous heating of the system or parts thereof. Thus, it is preferred according to the invention that for at least one

Part of the total duration of the start-up mode, the portion Az is increased in comparison to the portion A;. For example, the start-up mode can be divided into a first section and an immediately following one.

Benden second section of the total duration, whereby during the first section A» >

A, and during the second section A> = A; applies.

combustion air

[0129] Preferably, the combustion device (combustion chamber of the reactor) is supplied with combustion air, which is preferably preheated beforehand in a first flue gas/combustion air heat exchanger and/or a second flue gas/combustion air heat exchanger. Preferably, the first flue gas/combustion air heat exchanger and/or the second flue gas/combustion air heat exchanger are

Heat exchanger arranged in the flue gas duct, whereby the combustion air absorbs heat from the flue gas.

[0130] Preferably, the combustion air is cleaned by a filter before being fed into the system, compressed to the required pressure with a compressor and then fed through the first

Flue gas/combustion air heat exchanger and/or the second flue gas/combustion air heat exchanger in the flue gas duct and heated. From there, the heated combustion air flows into the combustion device. Shortly before entering the combustion device or within the combustion device, the combustion air is mixed with the combustion gas (preferably NH; in a mixture with H»).

Product gas - after catalytic decomposition until purification of H> 23

230085P00LU 12.07.2023

[0131] In the production mode, product gas leaves the second NHs decomposition device at a high temperature. In order to use the heat contained in the product gas, at least one heat exchanger is preferably provided in the flow direction of the product gas downstream of the second NHs decomposition device for the production mode, through which the product gas flows before the product gas is fed to a

Purification of Hz is fed: - preferably a third heat exchanger [preferably product gas/water heat exchanger for the production mode]; - preferably a fourth heat exchanger [preferably product gas/NH: heat exchanger for the production mode]; - preferably a fifth heat exchanger [preferably product gas/water heat exchanger for the production mode]; and/or - preferably a sixth heat exchanger [preferably product gas/water heat exchanger for the production mode]).

Product gas - residual amounts of undecomposed NH;

[0132] In the production mode, the recovery of NH; according to the invention preferably serves to separate non-decomposed NH: from the product gas and to make it available for further use as combustion gas or recovered starting material. A separate

Recovery of NH; is omitted. Thus, according to the invention, in the production mode, the purification of Hz from the product gas preferably takes place by pressure swing adsorption (PSA). Small residual amounts of non-decomposed NH; can preferably be separated according to the invention during pressure swing adsorption, whereby the recovery of NH; and the purification of Hz are combined into a common step.

Product gas - purification of H> and separation of residual gas mixture

[0133] In the production mode, according to the invention, H2 is particularly preferably purified by pressure swing adsorption (PSA). An adsorptive separation in a pressure swing adsorption device is preferred according to the invention, among other things because it takes place at moderate pressures and additionally also achieves high purity of H2, if required > 99.9%, with a yield of H2 in the range of e.g. approx. 80 to 85%.

As already mentioned, pressure swing adsorption can also separate residual amounts of NH3 and possibly HO in the same work step. To do this, the product gas is cooled to the desired temperature before entering the pressure swing adsorption device, preferably with a sixth heat exchanger [preferably product gas/water heat exchanger for the production mode]. The corresponding amount of heat is preferably absorbed by the water in the sixth heat exchanger.

According to the invention, the cooling water heated in this way is preferably used to preheat NH; in a preheating device in which NH; absorbs heat from the water. The cooled product gas is then preferably fed to a pressure swing adsorption device, where the gas mixture is separated under pressure by adsorption. 24

230085P00LU 12.07.2023

Hz - after purification until storage LU103170

[0134] In the production mode, the separated H> preferably leaves the pressure swing adsorption device and is preferably brought to an increased pressure, for example to about 200 bar, using an H> compressor. However, compression of the separated H> to an increased pressure is not absolutely necessary and pressures of significantly less than 200 bar are also included according to the invention. The compressed H> then preferably flows through a first H> heat exchanger in which cooling water absorbs heat from the compressed H>. In preferred embodiments, the separated H> is then brought to a further increased pressure using a second H> compressor.

Preferably, the further compressed H2 then flows through a second H2: heat exchanger, in which cooling water also absorbs heat from the compressed H2. The compressed H2 is then discharged from the system at a pressure of, for example, about 70 bar and, for example, stored in a suitable pressure vessel or directly fed for further use.

residual gas mixture

[0135] In the manufacturing mode, the product after purification/separation of Hz, preferably in the

Pressure swing adsorption device, remaining residual gas mixture typically N, H2O, remaining

NH; and Ho. Preferably, the residual gas mixture is fed to the combustion device so that it can be used to generate combustion heat.

flue gas

[0136] The flue gas leaves the combustion device at a high temperature and preferably enters a flue gas channel. In order to use the heat contained in the flue gas, heat exchangers are preferably provided in the flow direction of the flue gas downstream of the combustion device, through which the flue gas flows before the flue gas is released into the environment, e.g. via a chimney: - preferably a second heat exchanger [preferably flue gas/intermediate product gas heat exchanger for the production mode; preferably flue gas/heat transfer medium heat exchanger for the start-up mode]; - preferably a first heat exchanger [preferably flue gas/NH: heat exchanger for the production mode; flue gas/heat transfer medium heat exchanger for the start-up mode]; - preferably a first flue gas/combustion air heat exchanger; - preferably a flue gas/water heat exchanger; and/or - preferably a second flue gas/combustion air heat exchanger.

[0137] Even in start-up mode, the combustion of the mixture comprising NH; and

Hz formed flue gas enters the flue gas channel and thereby preferentially heats the second heat exchanger [preferably flue gas/heat transfer medium heat exchanger for start-up mode] and then preferably the first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for

230085P00LU 12.07.2023 the start-up mode], both of which release heat to the heat transfer medium. The flue gas then flows preferentially through the first flue gas/combustion air heat exchanger, preferably the

Flue gas denitrification unit, preferably the flue gas/water heat exchanger and preferably the second flue gas/combustion air heat exchanger. In this way, combustion air or

Water is heated by absorbing heat from the flue gas.

water or water vapor

[0138] Demineralized water is preferably fed into the plant as water for generating steam. Air and other gases dissolved in the water are preferably removed in a degasser.

[0139] Preferably, the water is preheated via a fifth heat exchanger. In the production mode, the fifth heat exchanger [preferably product gas/water heat exchanger for the production mode] is preferably flowed through by product gas, so that water absorbs heat from the product gas. In the start-up mode, the fifth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] is preferably flowed through by heat transfer medium, so that water absorbs heat from the heat transfer medium. In the flow direction of the product gas/heat transfer medium, the fifth heat exchanger is preferably arranged downstream of the third heat exchanger.

[0140] Preferably, the water is then passed through a flue gas/water heat exchanger and heated. The flue gas/water heat exchanger cools the flue gases from the combustion device in the flue gas channel, whereby the heat contained in the flue gas is used to heat the water vapor.

[0141] The steam is then preferably passed into a steam drum.

[0142] From the steam drum, the water is preferably passed through a third heat exchanger and thereby absorbs further heat, in order to then preferably be returned to the steam drum. The third heat exchanger is arranged in the flow direction of the product gas/heat transfer medium downstream of the second NH 3 decomposition device. In the production mode, the third heat exchanger [preferably product gas/water heat exchanger for the production mode] preferably serves to cool the product gas after it leaves the second NH 3 decomposition device, whereby heat contained in the product gas is also used to heat the steam. In the start-up mode, the third heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] preferably serves to release heat from the heat transfer medium to

Water. In start-up mode, hot water vapor is also generated in a H,O0 evaporation device and, if necessary, fed to the NH3; evaporation device together with the water vapor from the steam drum. 26

230085P00LU 12.07.2023

[0143] The condensation of water vapor in the NHi evaporator produces LU103170

Heat is obtained to evaporate the preheated NH;. After flowing through the NH evaporation device, the steam condensate is preferably fed to the preheater, which serves to preheat the NH; so that the heat contained in the steam is used in two stages to heat the NH;. After flowing through the preheater, the steam condensate can be discharged from the system.

[0144] As long as there is not enough heat available in the start-up mode to generate water vapor, the preferably electrically operated H20 evaporation device provides water vapor. The NH3 fed from the tank into the system is preferably preheated in the preheater using the electrically generated water vapor in analogy to the production mode and then evaporated in the NH3 evaporation device.

heat transfer medium

[0145] In the start-up mode, a heat transfer medium, preferably N; or NH3s, is supplied through at least one

Part of the system to absorb combustion heat or heat from the flue gas and to heat one or more of the system's devices to operating temperature. The heat transfer medium is preferably circulated and brought to the necessary pressure using a compressor.

The system according to the invention preferably comprises several valves at suitable locations in order to close the main process path at several locations in start-up mode and to enable the circulation of the heat transfer medium.

[0146] Preferably, in start-up mode, the heat transfer medium circulates from the compressor to a fourth heat exchanger [preferably heat transfer medium/heat transfer medium heat exchanger for start-up mode], where it absorbs heat from cross-flow heat transfer medium.

[0147] From there, the heat transfer medium flows in the start-up mode preferably to a first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode], where it

absorbs heat from the flue gas.

[0148] Subsequently, in start-up mode, the heat transfer medium preferably flows to a second

Heat exchanger [preferably flue gas/heat transfer medium heat exchanger for start-up mode], where it also absorbs heat from the flue gas.

[0149] From there, the heat transfer medium flows in start-up mode preferably through the second NHz

decomposition device, where it absorbs combustion heat, which flows as a heat flow from the combustion device into the second NHs decomposition device.

[0150] Then, in start-up mode, the heat transfer medium preferably reaches a third heat exchanger [preferably heat transfer medium/water heat exchanger for start-up mode], where it transfers heat to water. 27

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[0151] Subsequently, in start-up mode, the heat transfer medium preferably flows through the LU103170 fourth heat exchanger [preferably heat transfer medium/heat transfer medium heat exchanger for the

start-up mode] (i.e. cross-flow), where it transfers heat to the heat transfer medium guided in cross-flow.

[0152] Thereafter, the heat transfer medium in the start-up mode preferably flows through a fifth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode], where it

transfers heat to water.

[0153] Subsequently, in start-up mode, the heat transfer medium preferably flows through a sixth

Heat exchanger [preferably heat transfer medium/water heat exchanger for start-up mode], where it also transfers heat to water.

[0154] Finally, the heat transfer medium is returned to the compressor.

Description of the figures

[0155] The invention is explained in more detail below using preferred embodiments with reference to the figures. Figures 1, 2 and 3 each show, using flow diagrams, preferred embodiments of systems according to the invention on which preferred embodiments of the method according to the invention can be carried out. The embodiment according to Figure 3 is a variant of the embodiment according to Figure 2 and is only intended as

The details not shown in the detail of Figure 3 preferably correspond to those of Figure 2.

[0156] Figure 1 shows a schematic illustration of such a process. Part of the total NH3 used is burned in a mixture with H2 and O2 (reaction (A)). Combustion releases heat of combustion A. The other part of the NH3 is catalytically decomposed to H2 and N2 with the addition of heat of combustion, the mixture formed containing a residual amount of undecomposed NH3 in addition to H2 and N2 (reaction (B)). Reactions A and B are preferably carried out separately from one another in a common reactor which is designed analogously to a primary reformer. The majority of the H2 is separated as a product from the mixture formed during the decomposition of NH3, typically by pressure swing adsorption (PSA), and the remaining mixture of unseparated H2, Na and undecomposed NH3 is fed to the combustion (recycle (C)).

[0157] If the amount of unseparated Hz contained in the remaining mixture is not sufficient for satisfactory combustion of NH;, Hz can be branched off from the product Hz and also fed to the combustion (recirculation (D)). However, this is not preferred. Pressure swing adsorption typically already achieves an excellent purity of the

Hz is reached, and the remaining 28

230085P00LU 12.07.2023

The residual gas mixture contains, in addition to N2 and residual NH3, a sufficient amount of Ha, which can hardly be avoided for technical reasons. By returning this H2-containing residual gas mixture to the combustion device, the energy contained in the residual gas mixture can be used to generate combustion heat. An additional enrichment of the residual gas mixture with H2 for combustion does not make economic sense, at least not in the production mode, and is therefore not preferred. If the total amount of the residual gas mixture is not sufficient to produce the required

In order to generate the necessary amount of heat for the catalyzed decomposition of NH;, the amount of NH; in the combustion gas is preferably increased according to the invention, but not the amount of Hz from the purified valuable product.

[0158] Figure 2 illustrates a preferred system according to the invention. For convenience, the production mode and start-up mode are explained one after the other below.

[0159] Plant/process according to Figure 2 in manufacturing mode:

[0160] In the production mode, liquid NH3, which is present at low temperature and increased pressure, is led from tank 10 via line 11 by means of pump 12 through preheater 13 and heated. In NH3-

The NH; is evaporated in the evaporation device 14 and then flows via line 15 to branch 16, where the NH; flow is divided into two partial flows. Starting from branch 16, a first partial flow of the NH; is expanded and fed via line 17 to combustion device 18. A second partial flow of the NH; is fed from branch 16 via line 19 through the fourth heat exchanger [preferably product gas/NH: heat exchanger for the production mode] 20 and then flows via line 21 through the first heat exchanger [preferably flue gas/NH2-

Heat exchanger for the production mode] 22, where the NH; is further heated. The preheated NH; is fed to the first NH 3 decomposition device 65, where a partial catalytic decomposition takes place, preferably adiabatically. The intermediate product gas leaving the first NH 3 decomposition device 65 is fed via line 66 to the second heat exchanger [preferably flue gas/intermediate product gas-

Heat exchanger for the production mode] 67, which is arranged in the flue gas channel 49 in the flow direction of the flue gas upstream of the first heat exchanger 22. There, the intermediate product gas is heated and then introduced via line 23 into the second NH3 decomposition device 24. The flow through the second NHs decomposition device 24 is preferably from top to bottom. The heat required to maintain the reaction is generated by heating the second NHs decomposition device 24 by combustion of H> and NH; in the combustion device 18.

[0161] In the production mode, after the decomposition of NH3, the product gas formed (comprising N3, H2 and possibly remaining NH3) flows through the third heat exchanger [preferably product gas/water heat exchanger for the production mode] 26, then the fourth heat exchanger [preferably product gas/NH3

Heat exchanger for the production mode] 20, then line 27 and for further cooling a 29

230085P00LU 12.07.2023 fifth heat exchanger [preferably product gas/water heat exchanger for the production mode] 28, which is preferably operated with water. Finally, the product gas is further cooled by means of a sixth heat exchanger [preferably product gas/water heat exchanger for the production mode] 29 and then fed via line 30 to a pressure swing adsorption device 31, where the gas mixture is separated under pressure by adsorption. The H2 separated in this way leaves the pressure swing adsorption device 31 via line 32, is brought to an increased pressure via a first H2 compressor 33, flows through a first H2 heat exchanger 34, a second H2 compressor 35 for further pressure increase, a second H2 heat exchanger 36 and is discharged from the system at a pressure of, for example, about 70 bar via line 37.

[0162] The residual gas mixture remaining in the pressure swing adsorption device 31 after separation of the H > contains Na, residual NH ; and H 2 and is returned via return line 38 and fed to the combustion device 18 via branch line 39, so that energy contained in the residual gas mixture can be used to generate combustion heat.

[0163] In the production mode, combustion air for the combustion process in the combustion device 18 is cleaned via filter 40, compressed by means of compressor 41, passed via line 42 through the second flue gas/combustion air heat exchanger 43 and heated. The

Combustion air via line 44 and through the first flue gas/combustion air heat exchanger 45 is further heated there and then flows via line 46 and the two branching branch lines 47 and 48 into combustion device 18, where the combustion air is fed to the partial flow of NH3 fed via line 17 in order to burn it and thus generate combustion heat.

[0164] In the production mode, the hot flue gas from the combustion in the combustion device 18 is first cooled via the second heat exchanger [preferably flue gas/intermediate product gas heat exchanger for the production mode] 67, whereby heat is used to heat the second NHz

Decomposition device 24 is obtained after leaving the first NH3 decomposition device 65. The flue gas is then further cooled via the first heat exchanger [preferably flue gas/NH: heat exchanger for the production mode] 22, whereby

Heat is obtained for heating the NH3 supplied to the first NH3 decomposition device 65. The flue gas is then passed through flue gas channel 49 via the first flue gas/combustion air heat exchanger 45, by means of which the combustion air is preheated, and then flows through flue gas denitrification unit 50, by means of which the flue gas is cleaned of nitrogen oxides (NOx). The flue gas then flows through line 51 through flue gas/water heat exchanger 52, whereby heat is obtained for heating water, and then flows through the second

Flue gas/combustion air heat exchanger 43, which also serves to heat the combustion air. The flue gas is then compressed in the end area of the flue gas duct 49 by means of the flue gas compressor 53 and leaves the system via chimney 54.

230085P00LU 12.07.2023

[0165] In the production mode, water for the production of steam is fed in via line 55, passed through the fifth heat exchanger [preferably product gas/water heat exchanger for the production mode] 28 and then passed at an increased temperature into degasser 56, in which air and other gases dissolved in the water are removed. By means of pump 57, the water is pumped through line 58

Flue gas/water heat exchanger 52 and heated. The flue gas/water heat exchanger 52 serves to cool the flue gases from the combustion device 18 in the flue gas channel 49, whereby the thermal energy contained in the flue gas is used to heat the water vapor, which is then passed through the flue gas/water heat exchanger 52 via line 59 into the water vapor drum 60. Water can be fed from the water vapor drum 60 via line 61 through the third

Heat exchanger [preferably product gas/water heat exchanger for the production mode] 26 and thereby absorb further heat energy to then be returned to the steam drum via line 62. The third heat exchanger 26 is arranged in the outlet line 25 in the flow direction of the product gas downstream of the second NH3 decomposition device 24 and serves to

Cooling of the product gas after leaving the second NH4 decomposition device 24. The heat obtained can thus be used to generate further water vapor.

[0166] In production mode, the hot steam generated in the steam drum 60 is introduced via line 63 into the upper area of the NH+ evaporator 14. The condensation of the steam generates the heat to evaporate the preheated NH;. After flowing through the NH+ evaporator 14, the steam condensate is fed via line 64 to the preheater 13, which serves to preheat the NH; so that the heat contained in the steam is used in two stages to heat the NH;. After flowing through the preheater 13, the steam condensate can be discharged from the system.

[0167] Plant/process according to Figure 2 in start-up mode

[0168] In the system concept according to the invention, in the start-up mode, a heat transfer medium, preferably N 3 or N 2 , is passed through at least part of the system in order to absorb heat from the combustion device or the flue gas and to heat the system's devices to operating temperature. The cold heat transfer medium is preferably circulated and passed through a compressor 77 in order to build up the necessary pressure. In the start-up mode, the main process path is closed at several points with at least some of the valves 68, 75, 79, 81, 82, 83 in order to enable the circulation of the heat transfer medium. The first NH 3 decomposition device 65 is excluded from the circulation.

[0169] As long as there is not enough heat available for the generation of steam during start-up, the preferably electrically operated H:O evaporation device 84 provides steam. The NH; fed from the tank 10 into the system is preheated with the help of the electrically generated steam in analogy to the production mode in preheater 13 and then 31

230085P00LU 12.07.2023

Bend evaporated in the NH3 evaporation device 14. In order for the evaporated NH; to be catalytically decomposed, it must be heated to the activation temperature of the NHs decomposition catalyst, in the case of a nickel-based NH2 decomposition catalyst preferably to 600 to 650°C, in the case of a nickel-based NH3 decomposition catalyst

In the case of a ruthenium-based NHs decomposition catalyst, the temperature is preferably 350 to 400°C.

[0170] In the start-up mode, NH; (part or all of the amount) is passed through the electrical heating element 74 and heated therein above the activation temperature of the NHs decomposition catalyst in the first NHs decomposition device 65. The heated NH; then flows via line 73 into the first NHs decomposition device 65, where the NH; is at least partially decomposed. In the preferably adiabatic reaction, a conversion of e.g. 18% can be achieved, depending on the preheating temperature.

[0171] In start-up mode, the intermediate gas thus formed contains Hz and is optionally mixed with further

NH; mixed and burned in the combustion device 18 to form flue gas. Due to the partial decomposition of NH;, a sufficient amount of Hs is available to ensure or improve the combustion of the NH;. The preferably electrically operated H:O evaporation device 84 and the electrical heating element 74 require electrical energy to evaporate and further heat the NH; for the catalytic decomposition; the subsequent combustion of NH; together with the H> formed by the catalytic decomposition then provides the

Heat to heat the heat transfer medium.

[0172] In the start-up mode, the heat transfer medium circulates from the compressor 77 to the fourth heat exchanger [preferably heat transfer medium/heat transfer medium heat exchanger for the start-up mode] on the cold side, from there via line 21 to the first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] 22, and then via line 80 to the second heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] 67. From there, the heat transfer medium flows through the second NH3 decomposition device 24 and reaches the third heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 26 via line 25 and then the fourth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 26. carrier medium/heat transfer medium heat exchanger for start-up mode] 20 on the hot side.

From there, the heat transfer medium flows through the fifth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 28 and then the sixth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 29, which ensures a constant inlet temperature in the downstream nitrogen compressor, which

Pressure loss across the system is compensated. Alternatively, the downstream compressor can also be a

N2/NHz compressor, which fulfils a dual function, i.e. is used to compress both the N> and the NH;.

[0173] In preferred embodiments, in the start-up mode, the NH3 stream is converted into a first NHs

partial flow and a second NHz partial flow. Only the first NHz partial flow is added to the first 32

230085P00LU 12.07.2023

decomposition device 65. The second NHz partial flow is fed after flowing through the first LU103170

Heat exchanger [preferably flue gas/heat transfer medium heat exchanger for start-up mode] 22 via line 80, preferably flows through the second heat exchanger [preferably flue gas/heat transfer medium heat exchanger for start-up mode] 67 and then the second NHs-

decomposition device 24, whereby the second NHs decomposition device 24 absorbs heat from the second NHs partial flow. The second NHs partial flow therefore initially only has the function of

Heat transfer medium. In this way, the second NH 2 decomposition device 24 is gradually heated until the start-up temperature (activation temperature) for the catalytic decomposition of NH 3 is reached, so that from this point on additional Hz is produced in the second NH 2 decomposition device 24 by catalytic decomposition of NH 3 .

[0174] The heat transfer medium is heated in the start-up mode when it flows through the cold

Side of the fourth heat exchanger [preferably heat transfer medium/heat transfer medium heat exchanger for the start-up mode] 20, where it absorbs heat from the heat transfer medium guided in cross-flow. In addition, the heat transfer medium is heated when flowing through the first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] 22 and the second heat exchanger [preferably flue gas/heat transfer medium heat exchanger for the start-up mode] 67, where it absorbs heat from the flue gas. In addition, the heat transfer medium is heated when flowing through the second NH3 decomposition device 24, where it absorbs combustion heat, which flows as a heat flow from the combustion device 18 into the second NH3 decomposition device 24.

[0175] The heat transfer medium is cooled in the start-up mode when flowing through the third heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 26, where it gives off heat to water, and when flowing through the warm side of the fourth heat exchanger [preferably heat transfer medium/heat transfer medium heat exchanger for the start-up mode] 20, where it gives off heat to the heat transfer medium guided in cross-flow. In addition, the

Heat transfer medium is cooled as it flows through the fifth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 28 and then the sixth heat exchanger [preferably heat transfer medium/water heat exchanger for the start-up mode] 29, where it releases heat to water.

[0176] The flue gas formed during the combustion of the mixture comprising NH; and H> flows through the flue gas channel 49 in the start-up mode and heats the second heat exchanger [preferably

Flue gas/heat transfer medium heat exchanger for start-up mode] 67 and then the first heat exchanger [preferably flue gas/heat transfer medium heat exchanger for start-up mode] 22, both of which transfer heat to the heat transfer medium. The flue gas then flows through the first flue gas/combustion air heat exchanger 45, the flue gas denitrification unit 50, the

Flue gas/water heat exchanger 52 and the second flue gas/combustion air heat exchanger. 33

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In this way, combustion air or water is heated by absorbing heat from the flue gas.

[0177] When the system has warmed up sufficiently to switch from start-up mode to production mode, the circulation of the heat transfer medium is terminated by means of the valves 68, 75, 79, 81, 82, 83.

[0178] If NH3 or another combustible gas is used as the heat transfer medium, it can be discharged via line 76 and valve 68 and then burned at the flare tower 70.

Preferably, condensate is separated beforehand in separation device 71. This condensate can comprise water which is present in small amounts in the NH; (< 0.5 wt. %), and/or NH; which was not converted in the second NH3 decomposition device 24 in the start-up mode.

[0179] Figure 3 illustrates a preferred variant of the system according to the invention according to Figure 2. Since the production mode according to the variant of Figure 3 largely corresponds to that according to Figure 2, only the start-up mode is expediently explained below.

[0180] If Na is used as heat transfer medium, NH3 can be added continuously.

[0181] Plant/process according to Figure 3 in start-up mode

[0182] According to this preferred embodiment, for the start-up mode, the electric heating element 74 is arranged in the flow direction of the NH3; downstream of the valve 82 and upstream of the first NH3-

Decomposition device 65 is arranged. The valve 82 regulates which portion of NH; is fed into the first NH: decomposition device 65 for partial catalytic decomposition and which portion of NH; is fed via line 80 into the second NH2 decomposition device 24 as a heat transfer medium.

[0183] Via valve 75, which is installed in the flow direction of the NH; downstream directly after branch 16, the supply of fuel-NHz into the combustion device 18 is temporarily blocked or regulated; this function is performed by the first NHz decomposition device 65 and the

Valve 82.

[0184] The circulation of the NH3 as a heat transfer medium then takes place according to the invention as follows: With the valve 75 closed, the NH3 is passed past branch 16 to the fourth heat exchanger 20 (not shown again in Figure 3) and then to the first heat exchanger 22. From there, it is divided into a first NH3 partial flow and a second NH3 partial flow.

[0185] The first NH3 partial stream is fed via valve 82 into the first NH3 decomposition device 65. Valve 81 is closed so that the intermediate product gas leaving the first NH3 decomposition device is fed via branching line 39 to the combustion device 18 and burned therein. 34

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[0186] The second NHz partial flow is fed via line 80 with valve 81 closed via the second LU103170

Heat exchanger 67 of the second NH3; decomposition device 24, where it initially serves as a heat transfer medium (provided the activation temperature of the NH3; decomposition catalyst in the second

NH3 decomposition device has not yet been reached). The second N3 partial flow leaving the second N3 decomposition device 24 is passed via lines 25 and 27 to the fourth heat exchanger 20, then to the fifth heat exchanger 28 and finally to the sixth heat exchanger 29 (all not shown again in Figure 3). Valve 83 and valve 68 are closed so that the second N3 partial flow is passed via line 76 to the compressor 77 (all not shown again in Figure 3). Part of the NH3 is consumed in this way and intermediate product gas, for example, is passed via line 19.

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List of reference symbols: LU103170

Tank 29 sixth heat exchanger [preferably product gas/water heat exchanger for the production mode; heat transfer medium/water heat exchanger for the start-up mode] 11 line 12 pump 13 pre-heater 14 NH; evaporation device]

Line 30 Line 16 Branch 31 Pressure swing adsorption device 17 Line 32 Line 18 Combustion device 33 Hz compressor 19 Line 34 First H2 heat exchanger Fourth heat exchanger [preferably product gas/NH3 heat exchanger for the 35 Hz compressor 36 Second H2 heat exchanger

manufacturing mode; heat transfer medium/heat transfer medium heat exchanger for start-up mode] 37 hydrogen output line 38 return line 39 branch line 21 line 40 filter for combustion air 22 first heat exchanger [preferably 41 compressor

Flue gas/NH; heat exchanger for the 42 line

Production mode; flue gas/heat transfer medium heat exchanger 43 second flue gas/combustion air heat exchanger for start-up mode] 44 line 23 line 45 first flue gas/combustion air heat exchanger 24 second NHs decomposition device

Outlet line 46 Line 26 third heat exchanger [preferably product gas/water heat exchanger for the 47 Branch line

Manufacturing mode; heat transfer medium/water heat exchanger for the 49 flue gas duct 50 flue gas denitrification unit

start-up mode] 51 Line 27 Line 52 Flue gas/water heat exchanger 28 fifth heat exchanger [preferably product gas/water heat exchanger for the 53 Flue gas compressor 54 chimney

Production mode; heat transfer medium/water heat exchanger for the 55 degasser

Start-up mode] 57 Pump 58 Line 36

230085P00LU 12.07.2023 59 line 71 condensate separator LU103170 60 steam drum 72 pump 61 line 73 line 62 line 74 electric heating element 63 line 75 valve 64 line 76 line 65 first NHz decomposition device 77 compressor 66 line 78 additional tank 67 second heat exchanger [preferably 79 valve

Flue gas/intermediate product gas heat exchanger for production mode; 80 Line Flue gas/heat transfer medium heat exchanger for start-up mode] 81 Valve 82 Valve 83 Valve 68 Valve 84 H:0 evaporation device. 69 Line 70 Flare tower 37

Claims (1)

230085P00LU 12.07.2023 Patent claims: LU103170 1. A plant for producing H2 from NH3; wherein the plant is operable in a production mode at operating temperatures; wherein the plant is operable in a start-up mode to heat at least one device of the plant from an initial temperature to an operating temperature; wherein the plant for the start-up mode comprises at least the following devices for heating the at least one device to the operating temperature: - a heating element (74) for heating NH3; - in the flow direction of the NH3; downstream of the heating element (74), a first NH3 decomposition device (65) for partially catalytically decomposing the heated NH3 to produce a combustion gas comprising Ha, N3 and residual NH3; - optionally, in the flow direction of the combustion gas, downstream of the first NH3 decomposition device (65), a device for metering combustion air into the combustion gas; - in the flow direction of the combustion gas downstream of the first NH3 decomposition device (65), a combustion device (18) for burning the combustion gas to generate combustion heat and flue gas; - a compressor (77) for compressing a heat transfer medium; and - in the flow direction of the flue gas downstream of the combustion device (18) and in the flow direction of the heat transfer medium downstream of the compressor (77), a first heat exchanger (22) and/or a second heat exchanger (67) for heating the heat transfer medium by absorbing heat from the flue gas; and wherein the at least one device of the system is arranged in the flow direction of the heat transfer medium downstream of the first heat exchanger (22) and/or the second heat exchanger (67) and is in fluid communication with the heat transfer medium for absorbing heat from the heat transfer medium. 2. The plant according to claim 1, wherein the at least one device is selected from: - a second NH 2 decomposition device (24); preferably in production mode for the catalytic decomposition of vaporized NH 3 ; to produce a product gas comprising H 2 and N 2 ; 1 230085P00LU 12.07.2023 - a third heat exchanger (26); preferably in production mode for heating water, LU103170 preferably for heating or generating water vapor, by absorbing heat from the product gas; - a fourth heat exchanger (20); preferably in production mode for heating NH; by absorbing heat from the product gas; - a fifth heat exchanger (28); preferably in production mode for heating water by absorbing heat from the product gas; and - a sixth heat exchanger (29); preferably in production mode for heating water by absorbing heat from the product gas. 3. The system according to claim 1 or 2, wherein the system comprises at least one device selected from: - a first flue gas/combustion air heat exchanger (45); preferably in start-up mode and/or in production mode for heating combustion air by absorbing heat from the flue gas; - a flue gas denitrification unit (50); preferably in start-up mode and/or in production mode for cleaning the flue gas of nitrogen oxides (NOx); - a flue gas/water heat exchanger (52); preferably in start-up mode and/or in production mode for heating water, preferably for heating or generating water vapor, by absorbing heat from the flue gas; - a second flue gas/combustion air heat exchanger (43); preferably in start-up mode and/or in production mode for heating combustion air by absorbing heat from the flue gas. 4. The system according to any one of the preceding claims, wherein the heating element (74) is electrically heated. 5. The system according to one of the preceding claims, comprising in the flow direction of the NH; upstream of the heating element (74) - an H:O evaporation device (84) for evaporating water to produce water vapor; and - an NHs evaporation device (14) for evaporating liquid NH; by absorbing heat from the water vapor. 2 230085P00LU 12.07.2023 LU103170 6. The system of claim 5, wherein the H:0 evaporator (84) is electrically heated. 7. The plant according to any one of the preceding claims, wherein the combustion device (18) and the second NH s decomposition device (24) are in heat exchange with each other and are configured for a heat flow from the combustion device (18) into the second NH s decomposition device (24). 8. A method for starting up a plant for producing H2 from NH3; comprising the following steps: (c) heating NH3; (d) partial catalytic decomposition of the heated NH3 in a first NH3 decomposition device (65) to produce a combustion gas comprising H2, N2 and remaining NH3; (e) optionally, metering combustion air into the combustion gas; (f) burning the combustion gas in a combustion device (18) to produce combustion heat and flue gas; (g) compressing a heat transfer medium; (h) heating the heat transfer medium by absorbing heat from the flue gas; and (i) heating at least one device of the plant by absorbing heat from the heat transfer medium. 9. The method according to claim 8, wherein the at least one device is selected from: - a second NH3 decomposition device (24); preferably after starting up the plant for the catalytic decomposition of vaporized NH3; to produce a product gas comprising H3 and N3; - a third heat exchanger (26); preferably after starting up the plant for heating water, preferably for heating or producing water vapor, by absorbing heat from the product gas; - a fourth heat exchanger (20); preferably after starting up the plant for heating NH3; by absorbing heat from the product gas; - a fifth heat exchanger (28); preferably after starting up the plant for heating water by absorbing heat from the product gas; and 3 230085P00LU 12.07.2023 - a sixth heat exchanger (29); preferably after starting up the plant for heating water by absorbing heat from the product gas. 10. The method according to claim 8 or 9, wherein the heating of NH; in step (c) is carried out using electrical energy. 11. The process of any one of claims 8 to 10, comprising the additional steps of (a) evaporating water to produce water vapor; and (b) evaporating liquid NH3 by absorbing heat from the water vapor. 12. The method according to claim 11, wherein the generation of water vapor in step (a) is carried out using electrical energy. 13. The method according to any one of claims 8 to 12, wherein the heat transfer medium is circulated through at least a portion of the plant. 14. The method according to any one of the preceding claims, wherein the heat transfer medium comprises N» or consists essentially thereof. 15. The method according to any one of the preceding claims, wherein the heat transfer medium comprises NH; or consists essentially thereof. 4