LU103144B1 - Catalytic decomposition of ammonia using water vapor as a heat transfer medium - Google Patents

Abstract

The invention relates to a system and a method for producing H2 by catalytic decomposition of NH3. Water serves as a heat transfer medium for recovering process heat. The process heat is absorbed by water or steam and then transferred to NH3, whereby NH3 is heated and evaporated. The use of water or steam as a heat transfer medium has advantages, including in terms of cost-effectiveness and safety.

Description

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LU103144

Catalytic decomposition of ammonia using water vapor as a heat transfer medium

[0001] The invention relates to a plant and a process for the production of H, by catalytic

Decomposition of NH;. Water serves as a heat transfer medium for the recovery of process heat. The process heat is absorbed by water or steam and then transferred to

NH; is released, whereby NH; is heated and evaporated. The use of water or steam as a heat transfer medium has advantages, including in terms of cost-effectiveness and safety.

[0002] H, can be obtained from H,O using renewable energy and then converted into NH; with N,. NH; can be stored and transported much more safely than H,. NH; can then be broken down into H, and N,. After separating from N,, H, finds 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; - N; + 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 in order to achieve satisfactory reaction yields. A variety of materials that are active at different temperatures have been proposed as catalysts for the decomposition of NH; (see, for example, Il. Lucentini et al., Ind. Eng. Chem. Res. 2021, 60, 18560- 18611).

[0004] During the catalytic decomposition of NH; a product gas is obtained which contains H, mixed with N, and possibly other gaseous components, e.g. undecomposed NH;. Many industrial

However, applications require H, in high purity, so that purification of the product gas is necessary before H, can be supplied to industrial applications. While the purification of

H, is basically possible via various processes, e.g. cryogenic processes or membrane processes, on a large scale, purification by pressure swing adsorption is particularly economical.

[0005] The catalytic decomposition of NH; into N, and H, takes place at high temperature and medium

Pressure in the gas phase. 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 feed NH; into the

To convert the NH into a gas phase, the addition of heat is necessary for the evaporation of the NH;

[0006] Conventional processes for the catalytic decomposition of NH3 produce significant amounts of

Heat which can be used to evaporate NH;

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[0007] US 4 704 267 A relates to the production of high-purity H 2 from liquid, anhydrous N 2 H 2 . LU103144

NH; is evaporated and then split into its components. The resulting dissociated

Gas stream is fed to an adiabatic metal hydride purification unit to absorb the H, present in the stream. The adsorbed H, is then recovered as a high purity product.

[0008] FR 1 469 045 A relates to an apparatus comprising a preheater fed with NH;, a tube bundle enclosing a catalyst for splitting NH; and optionally a cell for

Purification of H, by diffusion, which are interconnected and located in a single housing containing heating medium.

[0009] CN 111 957 270 A relates to an NH; decomposition apparatus comprising an NH; decomposition unit and a combustion unit acting on the NH; decomposition unit. NH; enters the NH; decomposition unit via a first purified gas inlet to carry out a decomposition reaction of the NH;. Mixed gas produced is discharged via a second purified gas outlet.

Gas is discharged and then enters the combustion unit via a second purified gas inlet. The mixed gas comprises N,, H, and undecomposed NH;. The mixed gas enters the combustion unit to provide heat for the decomposition reaction of the NH; of the NH; decomposition unit, so that the self-sufficiency of heat is realized in the NH2 decomposition-H, production system. No additional fuel is required for energy supply and the cost of the NH2

decomposition H, production system are reduced.

[0010] CN 113 896 168 A relates to a process for producing H, or reducing gas by

Decomposition of NH; using a two-stage process comprising the following steps: The liquid

NH; of the raw material is fully gasified and heated by a heat exchange gasification system and then enters a first-stage heat exchange NH; cracking reaction system to produce a partial NHz cracking reaction. The reaction gas from the heat exchange NHz; cracking system

The first stage reaction system enters a high temperature NH; cracking reaction system of the second

stage to carry out residual NH; cracking reaction. The high-temperature NH; cracking reaction gas of the second stage enters the heat exchange NH2 cracking reaction system of the first stage and the heat exchange gasification system in sequence to gradually recover heat, so that the reducing gas is obtained.

[0011] WO 2001/087770 A1 relates to the autothermal decomposition of NH 3 for the production of high-purity H 2 .

[0012] WO 2011/107279 A1 relates to an NH3-based H2 production reactor comprising a

NH; cracking chamber with an NH3 cracking catalyst, an inner combustion chamber with a combustion or oxidation catalyst which is in thermal contact with the NH; cracking chamber, an NH; gas preheating chamber and an outer jacket ring for heat recovery from the combustion products emerging from the combustion chamber, wherein the cracking chamber, the inner

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Combustion chamber, preheating chamber and heat recovery jacket ring are arranged concentrically LU103144.

[0013] WO 2017/160154 A1 relates to a method for generating energy with a gas turbine, comprising the following steps: (i) evaporating and preheating liquid NH; to produce preheated

NH; gas; (ii) introducing the preheated NH; gas into an NH; cracking device suitable for converting NH; gas into a mixture of H, and N,; (iii) converting the preheated NH; gas into a mixture of H, and N, in the device; (iv) cooling the mixture of

H; and N, to obtain a cooled H,- and N,-mixture; (v) introducing the cooled H,- and N,-

mixture into a gas turbine; and (vi) combusting the cooled H, and N, mixture in the gas turbine to generate power.

[0014] WO 2019/038251 A1 relates to a process for producing a product gas containing N, and H, from NH3, comprising the steps of non-catalytic partial oxidation of NH3 with an O--containing gas to give a process gas containing N,, water, amounts of nitrogen oxides and residual amounts of NH3; cracking at least part of the residual amounts of NH3 to give H3 and N3, in which

process gas by contact with a nickel-containing catalyst and simultaneously reducing the amounts of nitrogen oxides to N, and water by reaction with a portion of the H, formed during cracking of the process gas by contact of the process gas with the nickel-containing catalyst; and

Removal of the product gas containing H, and N,.

[0015] WO 2012/039183 A1 relates to an NH 2 decomposition device which produces H 2 as a combustion improver and an NH 3 oxidation device which reacts a portion of the introduced NH 3 with O 2 under

Using an oxidation catalyst, which causes combustion to achieve the required NHz

to provide the heat required for the decomposition reaction.

[0016] WO 2012/090739 A1 relates to an H 2 generator comprising a decomposition device that decomposes a compound containing an H atom and an N atom and generates H 2 ; a compound supply device that supplies the compound to the decomposition device; and an O 2 supply device that supplies O 2 to the decomposition device.

[0017] WO 2020/095467 A relates to a device for generating H, gas comprising: a NHz

Evaporation device which heats liquid NH; to produce NH2 gas; a main thermal decomposition device which causes combustion of a fuel gas, thereby producing the

NH;-gas produced by the NH;-evaporator is heated and decomposed into N,-gas and H,-gas; a

A cooler which cools a gas produced by the decomposition which contains the N, gas and the H, gas produced by the decomposition by the main thermal decomposition device; and a

Separator that separates the H, gas from the cooled gas produced by the decomposition.

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[0018] WO 2021/257944 A1 relates to the recovery of H, from an NH; cracking process in which the cracking gas is purified in a PSA device. The use of a membrane separator for the PSA exhaust gas improves the recovery.

[0019] WO 2022/096529 A1 relates to a process for cracking NH 3 , producing H 3 and generating electric current, comprising electrolysis of water in supplied NH 3 , evaporation, preheating and cracking of NH 3 using NH 3 synthesis catalysts at low temperatures.

[0020] WO 2022/243410 A1 relates to a process for the synthesis of H, via the catalytic cracking of NH3; wherein an NH3-containing stream is subjected to a catalytic cracking step in the presence of heat to obtain a combusted gas and a thermally cracked stream containing N3, H3 and possibly residual NH3 and optionally water; wherein the thermally cracked

stream is subjected to a H, recovery step to obtain a high purity H, stream.

[0021] WO 2022/265647 A1 relates to the recovery of a renewable H, product from a

NH; cracking process in which the cracked gas is purified in a first PSA device and at least a portion of the first PSA tail gas is recycled as fuel to reduce the carbon intensity of the renewable H- product.

[0022] WO 2022/265648 A1 relates to the removal of NOx pollutants by selective catalytic

Analytical reduction (SCR) of a flue gas produced in an NH3 cracking process using an aqueous NH3 solution obtained by cooling the compressed exhaust gas from a H3 reactor.

PSA device is used to clean the cracked gas.

[0023] WO 2022/265649 A1 relates to the reduction of the water content of the NH 3 used in an NH 3 cracking process, thereby enabling the use of water-incompatible cracking catalysts. The water removal process can also be used to recover and recycle NH 3 from the cracking gas.

[0024] WO 2022/265650 A1 relates to an NH; cracking process in which cracking gas is purified in a PSA system. Residual NH; in a first cracking gas is converted into further H, and N, by

PSA residual gas or a gas derived from it is fed to a secondary fission reactor and a second

fission gas is further processed.

[0025] WO 2022/265651 A1 relates to a process in which residual NH; in a H,-PSA system with a non-zeolitic adsorbent such as activated carbon, activated alumina or silica gel from NH2-

fission gas is removed.

[0026] The processes known from the prior art for the production of H, from NH; are not satisfactory in all respects and there is a need for improved processes which can be carried out economically on an industrial scale.

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[0027] The methods according to the state of the art have safety-related disadvantages. As LU103144

Heat transfer media are used for the preheating and evaporation of NH; the process gas in the main process line or the flue gas. In these state-of-the-art processes, NH; absorbs heat directly from the process gas or the flue gas in suitably connected heat exchangers. In both cases, the heat exchanger on the side of the liquid or evaporating NH; has the higher pressure. If a heat exchanger is damaged during such a process, e.g. if a pipe breaks, which can certainly happen in practice in large industrial plants, then NH; could flow in significant quantities either into the main process line or into the flue gas as a result of the pressure drop.

[0028] If NH; were to flow into the main process line in significant quantities, the gaseous

NH; from there into the system for separating H,, e.g. into a pressure swing adsorption device. Although pressure swing adsorption devices can be configured to separate polar substances such as NH;, a significant increase in the amount of adsorption can lead to a breakdown, whereby NH; would enter the product stream directly.

[0029] If NH; were to flow into the flue gas in significant quantities, the NH; would be

chimney emitted into the environment.

[0030] It is an object of the invention to provide an advantageous system and an advantageous method for

Production of H, by catalytic decomposition of NH;. The production of H, should be safe, economical and possible on an industrial scale.

[0031] This object is solved by the subject matter of the patent claims.

[0032] It was surprisingly found that water can be preferably used as a heat transfer medium to heat and evaporate cooled liquid NH3 (reactant).

[0033] According to the invention, NH; absorbs heat from heated water or steam in suitably connected heat exchangers and thus passes into the gas phase. If, in the case of the inventive

If a heat exchanger were to be damaged during the process, NH; would be mixed with the aqueous phase and possibly dissolved therein (approx. 1200 liters of NH; dissolve in one liter of water at 0°C, and approx. 500 liters of NH; at 23°C). Any breakthrough into the product gas or flue gas is efficiently prevented in this way according to the invention, thereby improving the safety of the process.

[0034] NH; is preferably stored cold, e.g. in a tank, and preferably enters the inventive system at -33°C. NH; must be heated and evaporated to carry out the catalytic decomposition reaction. To preheat the NH; to its boiling point and then

According to the invention, medium-pressure steam or its condensate is preferably used for evaporation, which is preferably fed in countercurrent to the NH;. This process is advantageous

° 230088P00LU with regard to the safety of the system, since it prevents NH; emissions into the flue gas or process gas in the event of damage to the heat exchanger involved (e.g. due to a pipe burst).

[0035] According to the invention, water serves as a heat transfer medium for heating and evaporating

NHz. Taking the pressure conditions into account, both water and NH; can be present independently of one another in liquid or gaseous form (water vapor, NH; vapor). With regard to water as a heat transfer medium which gives off heat to NH;, it is expedient to make the following distinction: (a) water vapor, preferably medium-pressure water vapor, preferably with a pressure in the range from 10 to 40 bar and with a temperature in the range from approx. 180°C to approx. 250°C; (b) liquid warm water, preferably with a temperature in the range from > 44°C to 90°C; (c) liquid heated cooling water at a higher temperature, preferably with a temperature in the range from > 32°C to 44°C; and (d) liquid heated cooling water at a lower temperature, preferably with a temperature in the range from 20°C to 32°C.

[0036] It has been found that measures to save water vapor for the preheating and evaporation of NH; lead to an increase in the yield of H, provided that the less required (released) amount of energy is otherwise integrated back into the overall process. Such a saving in water vapor is preferably achieved according to the invention by providing the amount of energy for preheating the NH; by other water streams, in particular by heated cooling water which is liquid, i.e. not in the form of water vapor. The amount of energy released by the absorption of

Heat from these water streams preheats NH 3 which is either still liquid or already vaporized under the given pressure conditions; can then be subsequently converted into

Steam, preferably medium-pressure steam, can be further heated.

[0037] Thus, the NH3 entering the plant is cold enough to use the cooling water produced in the plant as a heat source.

[0038] In preferred embodiments, for this purpose, downstream of an NH evaporation device according to the invention in which water vapor releases heat to NH evaporation and condenses in the process, (i) the blowdown which arises when water vapor is generated in an H 0 evaporation device according to the invention is added to the resulting condensed water vapor; and/or (ii) excess heated boiler feed water which is preheated by absorbing heat from product gas and/or flue gas is added, the excess amount resulting from the fact that more boiler feed water is heated than is required to generate water vapor in an H 0 evaporation device according to the invention.

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[0039] The invention relates to a plant for the production of H, by catalytic decomposition of LU103144

NH; comprising - a combustion device for burning a combustion gas to produce combustion heat and flue gas; - an NH; evaporation device for evaporating liquid NH; by absorbing

Heat from heated water, preferably water vapor; - in the flow direction of the NH; downstream of the NH evaporation device, an NH decomposition device for the catalytic decomposition of evaporated NH; taking up in the

Combustion device and producing a product gas comprising H; and Ny; - in the flow direction of the flue gas downstream of the combustion device a flue gas

Heat exchanger for heating water, preferably for heating or generating water vapor, by absorbing heat from the flue gas; and/or in the flow direction of the product gas downstream of the NH; decomposition device, a product gas heat exchanger for heating water, preferably for heating or generating water vapor, by absorbing heat from the product gas; and - a line for the heated water from the flue gas heat exchanger and/or from the product gas

Heat exchanger to the NH3 evaporator.

[0040] In preferred embodiments of the system according to the invention, the system 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!.

[0041] 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 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.

[0042] In preferred embodiments of the plant according to the invention, the NH3 decomposition device comprises 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 NH3 decomposition catalyst; wherein each catalyst bed is preferably present in a tube; wherein the catalyst beds are preferably connected in parallel.

[0043] In preferred embodiments of the plant according to the invention, the NH; decomposition device comprises at least one catalyst bed which comprises NH; decomposition catalyst, wherein the length of the catalyst bed in the flow direction for NH; is at least 1.0 m, preferably

230088P00LU at least 1.5 m, more preferably at least 2.0 m, even more preferably at least 2.5 m, most preferably LU103144 at least 3.0 m and especially at least 3.5 m; wherein the catalyst bed is preferably in a

pipe is present.

[0044] In preferred embodiments of the plant according to the invention, the combustion device comprises 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.

[0045] In preferred embodiments of the plant according to the invention, the flue gas heat exchanger and/or the product gas heat exchanger is a tube heat exchanger or tube bundle heat exchanger.

[0046] The invention also relates to the use of a plant according to the invention for the production of H-.

[0047] The invention further relates to a process for the production of H, by catalytic

Decomposition of NH; comprising the steps of: (a) burning a combustion gas to produce combustion heat and flue gas; (b) optionally, preheating NH; by absorbing heat from heated cooling water; preferably wherein the heated cooling water has previously absorbed heat from the product gas before

Carrying out a pressure swing adsorption and/or from H, after its compression; (c) optionally, preheating NH; by absorbing heat from water; and heating the water thus obtained by absorbing heat from the flue gas; preferably wherein the water is circulated. (d) optionally, heating NH; by absorbing heat from water obtained by step (e); (e) evaporating liquid NH; by absorbing heat from heated water, preferably

Water vapor; (f) catalytic decomposition of NH vaporized in step (e); taking up combustion heat generated in step (a) and generating a product gas comprising H, and N,; and (g) heating water, preferably heating or generating water vapor, by taking up heat from the flue gas generated in step (a) and/or from the gas generated in step (f).

product gas; and introducing the heated water or the heated or generated water vapor into step (e).

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[0048] Steps (b), (c) and (d) of the method according to the invention are optionally independent of one another. Preferably, steps (a) to (g), if implemented, are carried out in alphabetical order.

[0049] In preferred embodiments of the process according to the invention, in step (f) 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!.

[0050] In preferred embodiments of the process according to the invention, in step (e) the liquid NH3 is taken from a tank having 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.

[0051] In preferred embodiments of the process according to the invention, in step (f) the catalytic decomposition of NH; takes place 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; decomposition catalyst; each catalyst bed is preferably present in a tube; the catalyst beds are preferably flowed through in parallel by NH;.

[0052] In preferred embodiments of the process according to the invention, in step (f) the catalytic decomposition takes place on at least one catalyst bed which comprises NH; decomposition catalyst, wherein the length of the catalyst bed in the flow direction for NH; 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.

[0053] In preferred embodiments of the process according to the invention, in step (a) the

Combustion of the combustion gas by means 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.

[0054] In preferred embodiments of the process according to the invention, the heating in step (g) takes place in a heat exchanger selected from tube heat exchangers and tube bundle heat exchangers.

[0055] According to the invention, the catalytic decomposition of NH; the formation of N, and Hs, in

In the prior art, this is occasionally referred to as "cleavage" or "cracking" of NH;. According to the invention, the catalytic decomposition of NH; preferably takes place in the absence of O,.

[0056] Preferably, the invention comprises the following measures: (i) evaporation of NHz;

230088P00LU (ii) catalytic decomposition of NH; with supply of heat to obtain a product gas comprising N,, H, and possibly undecomposed NH; and H,O; (iii) recovery of heat; (iv) possible recovery of undecomposed NH2; (v) purification of H,.

Recovery of heat for evaporation of NH; with water as heat transfer medium

[0057] The recovery of heat according to the invention is an essential aspect of the invention because the catalytic decomposition of NH3 takes place at elevated temperature in the gas phase and the resulting residual heat should be used as efficiently as possible for economic and ecological reasons.

[0058] According to the invention, heat is provided by combustion of a combustion gas in a combustion device. A first part of the heat formed during combustion preferably flows into an NH3 decomposition device in which the NH3 decomposition catalyst is present, for example in the form of one or more catalyst beds. The endothermic catalytic decomposition of NH3 takes place there. A second part of the heat formed during combustion preferably leaves the combustion device with the flue gas and enters a flue gas channel.

[0059] According to the invention, the following are available as a source for the recovery of heat: - the hot product gas which leaves the NH3 decomposition device, and - the hot flue gas which leaves the combustion device.

[0060] The hot product gas typically represents a larger mass flow than the hot flue gas, but the temperature of the product gas is typically lower than the temperature of the flue gas. Through efficient heat integration, heat can be extracted to a suitable extent from the product gas on the one hand and the flue gas on the other, thereby increasing the overall yield.

[0061] As a heat transfer medium for the transfer of heat from product gas or flue gas to

NH; according to the invention, heated water, preferably water vapor, is used for the purpose of heating and evaporating it.

[0062] The water vapor is preferably generated in a H,O evaporation device, which preferably comprises a water vapor drum and a heat exchanger, which are operatively connected to one another. In a preferred embodiment, the H,O evaporation device comprises, in addition to the water vapor drum, the product gas heat exchanger in which water absorbs heat from the product gas. In another preferred embodiment, the H,O evaporation device comprises, in addition to the water vapor drum, the flue gas heat exchanger in which water absorbs heat from

230088P00LU the flue gas. In a further preferred embodiment, the H,0 evaporation device comprises, in addition to the steam drum, both the product gas heat exchanger, in which

Water extracts heat from the product gas, as well as the flue gas heat exchanger, in which water

absorbs heat from the flue gas.

[0063] To generate steam, boiler feed water is fed to the steam drum. If more boiler feed water is fed in than steam is removed, the result is a

Surplus of heated boiler feed water, which can be separated from the steam and used like other heated cooling water, in particular for heating NHz.

[0064] Preferably, heat contained in the hot product gas and/or flue gas is absorbed by the water, whereby water vapor is heated or generated. The water vapor is fed via a pipe system into the NH3 evaporation device, where NH3 absorbs heat from the water vapor, is heated and finally evaporates itself.

[0065] In a preferred embodiment, boiler feed water is preheated in the flue gas duct, then a bypass stream is branched off from it and the remaining remainder of the preheated boiler feed water is fed into the steam drum.

[0066] In another preferred embodiment, no bypass flow is diverted, but the entire amount of preheated boiler feed water is fed into the steam drum. Preferably, a surplus is then discharged from the steam drum in liquid boiling form. In this way, more heat can be extracted from the process gas (flue gas or product gas), which is

can be advantageous if excess heat is available there.

[0067] After leaving the NH; evaporation device, the heated and evaporated

NH; is then heated to an even higher temperature level, as is desirable or necessary for the catalytic decomposition of NH;, and finally fed to the NH; decomposition device.

[0068] In an economical process, only medium temperature levels for the heated NH; can be achieved with steam (<300°C). Therefore, starting from a medium temperature level achieved with the help of steam, the further heating of NH; up to a high

Temperature level (>300°C) according to the invention, preferably at least one heat exchanger, preferably at least two heat exchangers, are then used, in which the NH; absorbs heat from the hot product gas and/or the hot flue gas.

[0069] Additional heat required to reach the desired decomposition temperature or

Maintaining the endothermic catalytic decomposition is preferably provided according to the invention directly by a heat flow which flows from the combustion device into the NH;-

decomposition device. For this purpose, the NH4 decomposition device and the combustion device preferably together form a reactor which is designed analogously to a primary reformer.

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[0070] The recovery of heat according to the invention can preferably fulfill, for example, the following tasks LU103144: - preheating of water (e.g. boiler feed water); - preheating of NH3; - generation of water vapor; - evaporation of NH3; and - preheating of combustion air.

[0071] According to the invention, various combination options are available for the arrangement of the plant components for heat recovery.

[0072] Preferably, heat contained in the flue gas stream of the combustion device and/or heat contained in the product gas stream of the NH 2 decomposition device is converted into at least three, preferably at least four, particularly preferably at least five in the flow direction of the

flue gas stream or product gas stream are used in heat exchangers arranged one behind the other, preferably for different sub-processes of the process.

[0073] The evaporation of NH3 using the NH3 evaporation device according to the invention and a preferred preheater is explained in more detail below.

[0074] In the NH; evaporation device, NH; absorbs heat from water, preferably water vapor, and passes into the gas phase. Preferably, the temperature of the NH; when entering the NH2-

Evaporation device in the range of about 60+30°C, more preferably about 60+15°C. Preferably, the temperature of the NH; at the outlet from the NH; evaporation device is in the range of about 60+30°C, more preferably about 60+15°C.

[0075] Preferably, at least one heat exchanger is arranged downstream of the NH evaporation device in the flow direction of the NH ;, which is either the product gas heat exchanger or the flue gas heat exchanger. Preferably, at least two heat exchangers are arranged downstream of the NH ;, which are the product gas heat exchanger and the flue gas heat exchanger. The heated water supplied as a heat source for the operation of the NH ; evaporation device, preferably

Water vapor is generated in the product gas heat exchanger by absorbing heat from the product gas and/or in the flue gas heat exchanger by absorbing heat from the flue gas. The

Heat in the product gas and/or flue gas is used to heat or generate water vapor in a H,0 evaporator and this water vapor is fed to the NH; evaporator.

[0076] Preferably, the water vapor, optionally in the form of water vapor condensate, is used again after exiting the NH evaporation device, namely as a heat medium in an NH 2

Preheating and NH; evaporation.

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[0077] This is preferably done in at least a two-stage process in which NH3 and water vapor, or its water vapor condensate, are conducted in countercurrent. Due to the

Due to the ratio between the condensation enthalpy of the water vapor and the free enthalpy of its water vapor condensate, the condensation of the water vapor alone may not be sufficient to evaporate the NH; if the water vapor condensate is to be released at an acceptable temperature of e.g. 40°C. Therefore, according to the invention, a preheater is preferably used in which the evaporation of the NH; may already have partially begun.

[0078] Preferably, the preheater is arranged in the flow direction of the NH; upstream of the NH; evaporation device in order to preheat NH;. In the preheater, NH; absorbs heat from water, preferably water vapor condensate. Preferably, the temperature of the NH; when entering the

Preheater in the range of about -35+10°C, more preferably about -35+5°C. Preferably, the temperature of the NH; at the outlet from the preheater is in the range of about 60+30°C, more preferably about 60+15°C.

[0079] The water vapor flow is preferably adjusted so that the NH; evaporation device in the

Essentially only steam condensate leaves. In preferred designs, "blowdown" and/or boiler feed water, e.g. from a bypass, can be mixed into this steam condensate (see below).

[0080] Preferably, generated water vapor and generated water vapor condensate are passed in countercurrent through the preheater and the NH 3 evaporation device.

[0081] The NH; passes through the preheater, in which NH; in countercurrent from steam condensate

absorbs heat. The energy input is high enough to heat the NH; to the boiling point and to partially evaporate it. Preferably, an evaporation of at least 5%, more preferably at least 10%, even more preferably at least 15%, most preferably at least 20% and in particular at least 25% of the total flow of NH; takes place in the preheater. For example, the

Vapor content of NH; up to 35%.

[0082] The preheater preferably contains a device for separating the two NH; phases, so that the not yet evaporated remainder of the NH; enters the NH; evaporation device at boiling temperature, and the gaseous NH; is transported in a separate pipeline.

[0083] Alternatively, both phases of the NH; can also be fed into the NH;-

evaporation device.

[0084] In the NH 3 evaporation device, steam serves as the heat medium, for example saturated steam at 33.5 bar a and a temperature of 239.8°C. The steam ensures the complete evaporation of the NH 3 , preferably again via a device integrated into the heat exchanger for separating the two phases. Both gaseous NH 3 streams are preferably combined and fed further into the process.

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[0085] For the NH evaporation device described above and the possibly present LU103144

Water or steam is used as a preheater, which has previously absorbed heat from the flue gas and/or product gas.

[0086] According to the invention, in addition to heating NH; heat from heated

Cooling water is used.

[0087] Heated cooling water, which is preferably used according to the invention for heating NH, is preferably obtained during - cooling of the product gas with the aid of a process cooler in the flow direction of the product gas upstream of a pressure swing adsorption device; - cooling of the water vapor condensate with the aid of a water vapor condensate heat exchanger in the flow direction of the water vapor condensate downstream of the NH evaporation device and preferably downstream of any preheater present; - cooling of the H product with the aid of a heat exchanger in the flow direction of the H product downstream of an H compressor, possibly upstream of a second H compressor; and/or - cooling of the flue gas with the aid of a flue gas heat exchanger in the flue gas duct.

[0088] In preferred embodiments of the invention, the yield of H , is increased by relatively reducing the amount of water vapor produced and the resulting less heat remains in the process, whereby less combustion gas is required. The energy gap arising with regard to the preheating and evaporation of NH ;, which results from the relatively smaller amount of water vapor provided, is preferably closed by preheating NH ; with the heated cooling water.

[0089] For this purpose, a preheating device is preferably arranged in the flow direction of the NH; downstream of the tank and upstream of the NH; evaporation device, preferably also in the flow direction of the NH; upstream of the preheater, if present, which preferably serves to preheat the NH; and in which NH; absorbs heat from water, which in turn has previously accrued elsewhere as heated cooling water.

[0090] Preferably, the heated cooling water from a process cooler is supplied in the flow direction of the

Product gas is taken upstream of a pressure swing adsorption device, where it was previously

Heat has been absorbed from the product gas. Preferably, the heated cooling water is additionally or alternatively taken from a heat exchanger of a possible H, compressor, where it was previously

Heat from compressed H. Preferably, the heated cooling water is additionally or alternatively taken from a water vapor condensate heat exchanger which is connected downstream of the NHz evaporation device.

230088P00LU

[0091] Preferably, heat from the condensed water vapor is also used, i.e. the LU103144

Steam condensate is cooled before it is returned for processing. For this purpose, a steam condensate heat exchanger is preferably arranged downstream of the NH evaporation device in the flow direction of the steam condensate.

[0092] If a preheater is connected upstream of the NH evaporation device, the steam condensate heat exchanger is preferably located downstream of the

preheater. The steam condensate then preferably leaves the NH; evaporation device first and is returned to the preheater, in which NH; absorbs heat from the steam condensate and is thus preheated. The steam condensate then enters the steam condensate heat exchanger, in which cooling water absorbs heat from the steam condensate. The cooling water heated in this way can be used elsewhere, for example to preheat liquid NH;.

[0093] In addition, the flue gas can also be cooled with cooling water. This can be useful, for example, if there is no H compressor and therefore not enough heated cooling water is available to provide the required amount of heat for preheating and evaporating the NH;.

[0094] The sources for heated cooling water preferred according to the invention are illustrated in Figure 11, whereby it is possible according to the invention that only one of these sources, several of these sources, or all of these sources are used for preheating and, if necessary, evaporating

NH;.

[0095] The initial temperature at which fresh, i.e. not yet heated, cooling water is usually supplied depends on the climate of the location. The cooling water removes process heat through its

Heating by a temperature difference of typically about 8°C to about 15°C. The heat absorbed by cooling water is then preferably used to preheat liquid NH; (cf.

Figure 7).

[0096] The temperature of the cooling water or heated cooling water is thus preferably significantly below the temperature of the water or water vapor which is present in the NH;-

Evaporation device for evaporating NH; is used. The temperature of the heated cooling water is preferably at most 100°C, more preferably at most 80°C, even more preferably at most 60°C. For example, on the Arabian Peninsula a cooling water return temperature of approx. 50°C can be expected, in Central Europe it is more likely to be approx. 30°C.

[0097] As already mentioned, according to the invention a distinction is made between liquid heated

Cooling water of higher temperature (preferably > 32°C to 44°C) on the one hand, and liquid heated

Cooling water of lower temperature (preferably 20°C to 32°C) on the other hand.

[0098] If liquid heated cooling water of a lower temperature is used to heat NH;, it is preferred according to the invention to produce this liquid heated cooling water

230088P00LU lower temperature in the flue gas duct to install a heat exchanger (Figures 10, 14 and LU103144 16, additional heat exchanger 71) and thus preheat the NH; to its boiling point. The subsequent evaporation of the NH; heated in this way is then preferably achieved only by heat from the water vapor condensate.

[0099] If liquid heated cooling water of higher temperature is used to heat NH;, the NH; can be preheated to significantly higher temperatures. In this case, in the

A heat exchanger must be provided in the flue gas duct to absorb heat from the flue gas.

This is particularly useful if there is no H, compressor, so that a H,

There is no heat exchanger downstream of the compressor, in which heated cooling water at a higher temperature would otherwise be produced. Alternatively, such an H2 compressor is available. In this case, a heat exchanger downstream of the H2 compressor or between several H2 compressors preferably provides a sufficient amount of heated cooling water at a higher temperature.

[0100] For example, if a total power of 709 kW is required for preheating and evaporating NH;, then without using heated cooling water, e.g. 409 kW can be generated by condensing water vapor and the remaining 300 kW by heat transfer from water vapor condensate. With a sufficiently large amount of cooling water (e.g. heated from 25°C to 35°C), preheating of NH; can be achieved with a power of 115 kW, which

NH; to a temperature of 12°C. For preheating, only 252 kW of power is required and for evaporation, 342 kW of power is required. By appropriately integrating the heat released in the process gas, the yield of the

Investment by, for example, 0.4 to 0.5% can be achieved.

[0101] Furthermore, according to the invention, in addition to heating NH;, heat from water is preferably used, which absorbs heat from the flue gas, then releases this heat to NH; for preheating, then absorbs heat from the flue gas again, etc. The water is therefore preferably circulated in a circle for this purpose.

[0102] Warm water (>44-90°C) or heated cooling water are preferably not used to evaporate the NH;, but only to preheat it to the boiling point. In the case of preheating, a minimally higher temperature of the heat transfer medium of only 10 K can still lead to an economical design of a heat exchanger. In contrast, in the case of evaporation, the heat transfer medium should be at least 40 K hotter at its coldest point.

For this to happen, the warm water or the heated cooling water would have to have a significantly higher temperature, i.e. heat would have to be extracted from the flue gas and/or product gas at a higher temperature to generate it. According to the invention, however, the low temperature levels are preferably used to generate heated cooling water, in particular the low

230088P00LU

Temperature levels of the flue gas, and therefore preferably only a preheating LU103144 of NHz takes place, but not additional evaporation.

[0103] In preferred embodiments of the invention, an additional heat exchanger is provided in the flow direction of the NH; downstream of the tank and upstream of the NH evaporation device, preferably in the flow direction of the NH; downstream of the possibly present preheating device, preferably in the flow direction of the NH; upstream of the possibly present preheater, which preferably serves to preheat the NH; and in which NH; heat from

Water, which is preferably circulated in a circle and which has previously absorbed heat from the

has absorbed smoke gas.

[0104] For this purpose, the additional heat exchanger is preferably connected to another heat exchanger in

Active connection. The further heat exchanger is preferably arranged in the flow direction of the flue gas downstream of the flue gas heat exchanger and serves to heat the water by

Absorption of heat from the flue gas. Preferably, the additional heat exchanger and the further heat exchanger are connected to each other via a ring line through which the water is circulated, preferably with a pump.

[0105] The temperature of this water or heated water is therefore preferably significantly below the temperature of the water or water vapor which is used in the NH evaporation device according to the invention for evaporating NH . The temperature of the heated water (i.e. after absorption of heat from the flue gas) is preferably at most 110°C, more preferably at most 100°C, even more preferably at most 90°C.

[0106] Even after passing through several heat exchangers in which it has given off heat to water or NH; as a heat transfer medium and has been cooled as a result, the flue gas typically still has a comparatively high temperature of, for example, about 150°C. If the

If the flue gas has a temperature of around 120°C, preheating the combustion air in a heat exchanger arranged in the flue gas duct by absorbing heat from the flue gas would no longer be satisfactory, as this requires a relatively high temperature difference (see Figures 8 and 9, heat exchanger 43). The residual heat contained in the flue gas cannot therefore be converted into

process streams are integrated.

[0107] The flue gas also contains a high content of N-: A proportion of N, is released during the combustion of NH;. A proportion of N, is contained in the combustion air. A proportion of N, is generated during the catalytic decomposition of NH; and is possibly returned to the combustion device from a pressure swing absorption device. Due to the high content of N, the dew point of the flue gas is very low under the prevailing pressure conditions, e.g. at around 60°C. In order to achieve a

To avoid condensation, which can damage the heat exchangers mounted in the flue gas duct.

230088P00LU , according to the invention a temperature difference of 25°C is preferably maintained as a safety distance from the dew point.

[0108] Preferably, this residual heat in the flue gas (temperature range from about 85°C to about 120°C) is used by being absorbed by the water circulating in the circuit. For this purpose,

The flue gas duct is preferably provided with an additional heat exchanger through which water circulates as a heat transfer medium, preferably driven by a pump (see Figure 10).

[0109] The water is heated in this additional heat exchanger, for example from about 40°C to about 90°C and can then in turn serve as a heat source for NHz, which has advantageously already been preheated by the cooling water.

[0110] For example, at a flue gas outlet temperature of 90°C (see Figure 16), which complies with the distance criterion to the dew point, a power of 101 kW can be absorbed and used to heat NH; until the boiling point of the NH; is reached. The preheater arranged downstream in the flow direction of the NH; increases the proportion of evaporated NH; to about 34%. The NH; evaporation device used in the fourth stage is then only a

Output of e.g. 320 kW. Compared to a two-stage heating and evaporation of NH, the amount of heat required to produce the steam can be almost halved. The yield in relation to the amount of H produced can be increased by e.g. about 0.3%.

[0111] The use of water or steam for the preheating, heating and evaporation of the initially liquid NH; is economically and safety-wise advantageous compared to the otherwise basically also possible direct use of flue gas or

Process gas as a heat source for the evaporation of NH3. If a pipe is damaged, NH3 could flow into the exhaust gas and thus into the atmosphere, or enter the process stream. Electrical evaporation of water to generate steam would lead to high energy consumption and corresponding costs.

[0112] From a safety and economic point of view, water is therefore advantageous as a heat transfer medium.

[0113] According to the invention, the water vapor preferably has a slightly higher pressure than the NHz, so that in

In the event of damage to a heat exchanger (e.g. due to a burst pipe), water vapor might flow into the NH3. However, due to the comparatively low pressure difference, the inflow of water would be minimal.

[0114] In the NH; evaporation device, there would be a comparatively low mass inflow due to the low density of the water vapor, but due to the comparatively high

Temperature of the water vapor also leads to a significant inflow of energy. This would result in increased evaporation of NH;. However, since the NH; evaporation device and the heat exchanger integrated therein are intended and designed to evaporate NH;, such increased evaporation of NH; would be less critical.

230088P00LU

[0115] In the preheater, if present, the mass flow from the LU103144 would be due to the higher density

Water is higher, but the energy flow is lower.

[0116] NH evaporation devices preferred according to the invention and preheaters preferred according to the invention are equipped independently of one another in such a way that they remove any water (high boilers) contained in the NH as a "blowdown", so that in such a case no water breakthrough would possibly occur in the process.

[0117] If water vapor were to enter the process, the water would be in the decomposition of

NH; is inert and, like NH; in higher concentrations, would pass through the H, purification device (preferably pressure swing adsorption device). The presence of water in the H, product is less dangerous for end users.

[0118] In contrast to the use of water as a heat transfer medium according to the invention, the conventional use of process heat directly from the product gas or the flue gas would have

Evaporation of NH; instead the NH; the higher pressure. Compared to the product gas or

There would be a significant pressure difference in the flue gas, so that in the event of damage to a heat exchanger (e.g. due to a pipe burst) due to the high pressure difference and the high density of the liquid

NH; would result in a high mass inflow. A breakthrough of NH; into the flue gas would lead to emissions through the "stack" and to a significant environmental impact. A breakthrough of NH; into the

Product gas would pass the NH; into the H, product, which could be dangerous for end users.

[0119] Preferably, at least two heat exchangers are used for the evaporation of NH;, in which NH; is first preheated to the boiling point and then evaporated.

[0120] To improve safety, according to the invention the preheating, heating and evaporation of the NH; are decoupled from the decomposition of the NH; and the further process path.

currents

[0121] In the following, preferred embodiments of the invention are described with reference to the various

Streams are explained which are preferably used or formed when carrying out the process according to the invention or when operating/using the plant according to the invention. For this purpose, the following streams are conveniently distinguished below: e NH;: o from storage up to catalytic decomposition; o catalytic decomposition; e combustion gas; e combustion air; e product gas:

230088P00LU o after catalytic decomposition until purification of H,; LU103144 o separation of residual amounts of non-decomposed NH3; o purification of H, and separation of residual gas mixture; e H, -after purification until storage; e residual gas mixture: e flue gas; and e water or water vapor.

[0122] The following explanations apply equally to the system according to the invention, the use of the system according to the invention and the method according to the invention. Reference is made in part to the figures in order to illustrate a possible and possibly preferred embodiment according to the invention.

Integration of individual components or steps into the system or method according to the invention. However, this does not mean that all other components or steps described in the respective

The components shown in the figures or the steps associated therewith must necessarily be implemented simultaneously. The references to the figures are not to be interpreted as limiting, but serve merely to illustrate isolated preferred embodiments of the invention.

NH; - from storage to catalytic decomposition

[0123] According to the invention, the NH; is preferably stored as starting material.

[0124] 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. The boiling point of the NH; rises due to the increased system pressure. In order to convert NH; into the gas phase, the supply of

Heat is necessary. The evaporation of NH; requires considerable amounts of heat.

At a pressure of e.g. 30 bar, approximately 2.4 t/h NH3 can be preheated and evaporated per megawatt of energy input.

[0125] Before the NH3 can be catalytically decomposed, it is preferably heated successively to several temperature levels according to the invention.

[0126] Starting from liquid NH;, heating and subsequent evaporation of NH; to a medium temperature level (<300°C) preferably takes place by absorbing heat from water or water vapor.

[0127] This is followed by a further heating of NH; to a high temperature level (>300°C) by absorbing heat directly from flue gas and/or product gas, i.e. without

Water as a heat transfer medium. In these subsequent measures for further heating to a high temperature level (>300°C), the pressure differences and the density of the NH;

230088P00LU in the heat exchanger is significantly lower than with the previous measures for heating and evaporating NH; to a medium temperature level (<300°C). Any damage to the heat exchanger (e.g. pipe bursting) would therefore cause far less drastic safety problems with the subsequent measures (temperature level >300°C) than with the previous measures (temperature level <300°C).

[0128] The energy integration brings NH; preferentially to the desired temperature at the inlet into the

NH; decomposition device. In addition, the combustion air is preferably preheated. It is advantageous to preheat and evaporate water or boiler feed water. Since the process heat is present in two strands, in the product gas on the one hand and in the flue gas on the other, the heat exchangers can be arranged in different variants according to the invention.

[0129] According to the invention, liquid NH is preferably vaporized by absorbing heat from hot steam. This hot steam is in turn generated from water or cooler steam.

[0130] 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 "NH".

[0131] Preferably, the water absorbs heat from the flue gas downstream of the combustion device in the flow direction of the flue gas and/or heat from the product gas downstream of the NH; decomposition device in the flow direction of the product gas. For this purpose, in the inventive

Preferably, suitable heat exchangers are provided and connected.

[0132] Depending on the reaction temperature, the amount of heat contained in the product gas may be less than the heat contained in the combustion gas. This may influence the heat recovery.

Thus, at comparatively low temperatures at the outlet of the NH; decomposition device (e.g. about 500°C), the amount of heat in the product gas is significantly lower than in the flue gas. In such a case, according to the invention, the steam generation is preferably carried out largely or completely with

Heat from the flue gas from the combustion device is carried out. This variant of the connection of the components for heat recovery does have the disadvantage of a lower temperature gradient between the flue gas and the fed-in water, but can be compensated for by a larger NHz

evaporation device or a reduction in the pressure level.

[0133] It may also be preferred according to the invention to provide two NH; evaporation devices, which can be connected in parallel. The NH; is then preferably initially evaporated in a

preheater and then fed via two parallel lines into a first NH;-

evaporation device and a second NH; evaporation device. Preferably, the second NH; evaporation device can be fed with steam, while the first NH; evaporation

230088P00LU evaporation device is fed with water vapor condensate. After flowing through the first evaporation device, the water vapor condensate preferably reaches the preheater and flows through it, also giving off heat.

[0134] In preferred embodiments of the invention, water in the flow direction of the

Flue gas downstream of the combustion device in at least one first heat exchanger and at least one second heat exchanger, whereby the flue gas during

Flowing through the first heat exchanger has a higher temperature than flowing through the second heat exchanger (see Figure 10, first heat exchanger: flue gas heat exchanger 52; second heat exchanger: further heat exchanger 71).

[0135] Stations preferred according to the invention, through which the NH; preferably passes on the way from the tank to the NH; decomposition device, are explained below.

[0136] In preferred embodiments of the invention, liquid NH; leaves a tank and is fed into the system with a pump at system pressure. In order to evaporate the NH;, the NH; evaporation device is arranged in the flow direction of the NH; downstream of the tank, in which NH; absorbs heat from water vapor, which in turn has previously absorbed heat from product gas and/or flue gas (cf. Figures 1-10, NH; evaporation device 14).

[0137] Preferably, in the flow direction of the NH; downstream of the tank and upstream of the

NH; evaporation device, a preheater is arranged, which preferably serves to heat the NH; to the desired temperature at the inlet to the NH; evaporation device and in which

NH; absorbs heat from water, which in turn previously passed the NH; 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 (see Figures 4-10, preheater 13).

[0138] Preferably, a first heat exchanger is arranged in the flow direction of the NH; downstream of the NH; evaporation device, which preferably serves to further heat the NH; and in which NH; preferably absorbs heat from product gas (cf. Figures 8 and 9, heat exchanger 20).

[0139] Preferably, a second heat exchanger is arranged in the flow direction of the NH; downstream of the first heat exchanger, which preferably serves to further heat the NH; and in which NH; preferably absorbs heat from flue gas (cf. Figures 8 and 9, heat exchanger 22).

[0140] In preferred embodiments of the invention, when the catalytic decomposition of the NH; takes place in two stages in a first NH; decomposition device (pre-reactor) and a second NH; decomposition device, a further heat exchanger is preferably arranged in the flow direction of the NH; downstream of the first NH; decomposition device (pre-reactor) and preferably upstream of the second NH; decomposition device, which is preferably used to heat the intermediate product gas

230088P00LU after leaving the first NH; decomposition facility (pre-reactor) and before entering the second LU103144

NH; decomposition device (together with combustion device analogous to primary reformer) and in which NH; preferentially absorbs heat from flue gas (see Figure 9, further heat exchanger 67).

[0141] In preferred embodiments of the invention, a preheating device is arranged in the flow direction of the NH; downstream of the tank and upstream of the NH; evaporation device, preferably also in the flow direction of the NH; upstream of the preheater, if present, which preferably serves to preheat the NH; and in which NH; absorbs heat from water, which in turn has previously accrued elsewhere as cooling water, preferably in a

Process cooler in the flow direction of the product gas upstream of a pressure swing adsorption device or in a heat exchanger of an H, compressor (see Figures 7 and 10, preheating device 70).

[0142] In preferred embodiments of the invention, an additional heat exchanger is present in the flow direction of the NH; downstream of the tank and upstream of the NH; evaporation device, preferably in the flow direction of the NH; downstream of the possibly present preheating device, preferably in the flow direction of the NH; upstream of the possibly present preheater, which preferably serves to preheat the NH; and in which NH; absorbs heat from water, which is preferably circulated in a circuit and which has previously absorbed heat from the flue gas (cf. Figure 10, additional heat exchanger 73).

[0143] According to the invention, liquid NH; is preferably heated in at least one stage, more preferably in at least two stages, even more preferably in at least three stages, particularly preferably in at least four stages and converted from the liquid phase into the gas phase, i.e. evaporated. In this case, the NH; preferably reaches a medium temperature level (<300°C).

[0144] In the case of single-stage heating and evaporation, the liquid NH; is preferably heated in a single stage and also evaporated immediately (see Figures 1 to 3). In preferred embodiments of the invention, at least one heat exchanger is provided and connected for this purpose (see

Figure 1, flue gas heat exchanger 52; Figure 2, product gas heat exchanger 26). In other preferred embodiments of the invention, at least two heat exchangers are provided and connected (cf. Figure 3, product gas heat exchanger 26 and flue gas heat exchanger 52).

[0145] In two-stage heating and evaporation, the NH; is preferably first in a first

Stage heated (but not yet completely evaporated) and then evaporated in a second stage (see Figures 4 to 6, 8, 9). In preferred embodiments of the invention, at least one heat exchanger is used for the first stage and at least one heat exchanger for the second stage.

Heat exchangers are provided and connected (see Figure 4, stage 1: preheater 13; stage 2: pro-

230088P00LU product gas heat exchanger 26 or flue gas heat exchanger 52). In other preferred embodiments of the invention, at least one heat exchanger is used for the first stage and for the second stage

At least two heat exchangers are provided for each stage (see Figures 5, 6, 8 and 9 Stage 1: preheater 13; Stage 2: product gas heat exchanger 26 and flue gas heat exchanger 52).

[0146] In three-stage heating and evaporation, the liquid NH; is preferably first preheated in a first stage (but not yet completely evaporated), then additionally heated in a second stage (but also not yet completely evaporated) and then in a third

stage evaporates (see Figure 7).

[0147] In preferred embodiments, the ratio of condensation enthalpy to latent

Heat of the water vapor condensate so that the preheater evaporates a certain part of the NH; even in two-stage operation. If one wanted to use the preheater exclusively for preheating in order to achieve the evaporation of NH; exclusively via the condensation enthalpy of the

To realize the water vapor condensation, the amount of water vapor would have to be increased considerably and the water vapor condensate would exit with a very high remaining temperature, which is

disadvantage would be.

[0148] In preferred embodiments of the invention, at least one heat exchanger is used for the first stage, at least one heat exchanger for the second stage and at least one heat exchanger for the third stage.

At least one heat exchanger is also provided and connected (see Figure 7, stage 1: preheating device 70; stage 2: preheater 13; stage 3: product gas heat exchanger 26 or flue gas

Heat exchanger 52). In other preferred embodiments of the invention, at least one heat exchanger is provided for the first stage, at least one heat exchanger for the second stage and at least two heat exchangers for the third stage (not shown as a figure; corresponds to a variation of Figure 5 or 6 by the embodiment according to Figure 7; Stage 1:

Preheating device 70; stage 2: preheater 13; stage 3: product gas heat exchanger 26 and flue gas heat exchanger 52). A three-stage heating and evaporation of the liquid NH; can also be derived from Figure 10, namely if either preheating device 70 is missing or if the additional heat exchanger 73 is missing.

[0149] In four-stage heating and evaporation, the liquid NH; is preferably first preheated in a first stage (but not yet evaporated), then additionally heated in a second stage (but also not yet completely evaporated), then additionally heated in a third stage (but also not yet completely evaporated) and then in a third

Stage evaporates (see Figure 10). In preferred embodiments of the invention, at least one heat exchanger is provided and connected for the first stage, at least one heat exchanger for the second stage, at least one heat exchanger for the third stage and at least one, preferably at least two heat exchangers for the fourth stage (see Figure 10, stage

230088P00LU 1: preheating device 70; stage 2: additional heat exchanger 73; stage 3: preheater 13; stage 4: LU103144

product gas heat exchanger 26 (not shown) and flue gas heat exchanger 52).

[0150] After the NH3 has been heated and vaporized, it has preferably reached an intermediate temperature level (<300°C).

[0151] According to the invention, NH is then preferably further heated to a high

Temperature level (>300°C) by absorbing heat from flue gas and/or product gas. For this purpose, heat is absorbed in at least one heat exchanger from the product gas in the flow direction of the product gas downstream of the NH3 decomposition device and/or from the flue gas in the flow direction of the flue gas downstream of the combustion device.

[0152] In preferred embodiments of the invention, the further heating of NH; is initially carried out by absorbing heat from the product gas in a first heat exchanger provided and connected for this purpose. The first heat exchanger is preferably arranged in the flow direction of the product gas downstream of the NH; decomposition device and is flowed through on the one hand by the hot product gas and on the other hand by the NH; to be further heated. Heat recovered from the product gas is thus used for further heating of NH; (cf. Figures 8 and 9, heat exchanger 20).

[0153] In preferred embodiments of the invention, the further heating of NH; takes place alternatively or subsequently by absorbing heat from the flue gas in a second heat exchanger provided and connected for this purpose. The second heat exchanger is preferably arranged in the flow direction of the flue gas downstream of the combustion device and is flowed through on the one hand by the hot flue gas and on the other hand by the NH; to be further heated. From the

Heat recovered from flue gas is used for further heating of NH; (see Figures 8 and 9, heat exchanger 22).

NH; - catalytic decomposition

[0154] The catalytic decomposition of NH; according to the invention is the actual reaction for the formation of H,, which basically takes place thermally, but is accelerated by the use of an NH; decomposition catalyst. The catalytic decomposition of NH; can be carried out according to the invention under different conditions using different NH2 decomposition catalysts and with different connections with different reactor types.

[0155] According to the invention, the catalytic decomposition of NH is preferably carried out by supplying

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

230088P00LU

[0156] 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.

[0157] In preferred embodiments of the invention, a nickel-based NH 2 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 NH 3 is almost quantitative. At 650°C, the conversion of NH 3 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

NH; 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, N, and non-decomposed NH; are separated together from the product gas by pressure swing adsorption during the purification of H,.

[0158] Preferably, the NH 2 decomposition catalyst comprises supported nickel. Preferred support materials are selected from the group consisting of Al 2 O 3 , MgO, S 10 , mesoporous S 10 , (e.g.

MCF-17, MCM-41, SBA-15), zeolite (e.g. HY, H-ZSM-5), BaMnQ;, BaTiO;, BaZrO;, CaMnOs, Ca-

TiO;, CaZrO;, CeO,, Gd,O;, GdAIO;, KNbO;, La,0;, LaAlO;, MnO,, NaNbO;, Nb,0;, Sm,0;,

SmAIO;, SrMnOs, SrTi0;, SrZrO;, TiO,, Y,0;, ZrO,, carbon (e.g. CNTs, SWCNTs, AX-21,

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

mixtures thereof.

[0159] In other preferred embodiments of the invention, a ruthenium-based NHz

Decomposition catalyst is used. For this purpose, according to the invention, reaction temperatures in the range from 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.

[0160] Alternatively, other NH; decomposition catalysts can optionally be used at even lower reaction temperatures. The lower the reaction temperature, the lower the conversion and the more non-decomposed NH; must be separated from the product gas and recycled.

[0161] 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 H;) increases the volume, which is why an increased reaction pressure generally has a negative effect on the conversion. On the other hand, it is useful to increase the overall process

230088P00LU 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 of 400°C and above. However, since a reaction pressure of 1 bar only makes sense for very small systems, the system according to the invention is preferably operated at a higher reaction pressure, even if this means that a certain loss in conversion must be accepted.

[0162] The reaction pressure is particularly determined by the execution of the purification of

H,. The pressure swing absorption (PSA) preferred according to the invention for purifying H, 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 NH; 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 between the requirements of pressure swing adsorption on the one hand and the conversion achieved on the other.

[0163] The decomposition of NH3 can basically take place in different reactor types.

[0164] 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 a portion 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 which must be removed by condensation. A portion of the non-decomposed NH; then dissolves in the condensed water and is lost. In addition, the high

temperatures to form significant amounts of nitrogen oxides.

[0165] According to the invention, these disadvantages are avoided by physically separating the product gas from the combustion gas and the flue gas formed therefrom. The product gas is formed in the NH; decomposition device according to the invention by decomposition of NH; and leaves the

NH; decomposition device has its own outlet. The combustion gas is discharged together with

Combustion air is burned in the combustion device and the flue gas formed in the process also leaves the combustion device via its own outlet, preferably into a flue gas duct. 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 NH; decomposition device and thus supplies the heat required to maintain the endothermic decomposition of NH3.

[0166] Preference is given to the catalytic decomposition of NH; isothermal, quasi-isothermal or in a

A mixed form of isothermal and adiabatic process control is used. In isothermal reaction control, the temperature of the gas remains largely unchanged.

230088P00LU

[0167] In preferred embodiments of the invention, the catalytic decomposition of NH; LU103144 takes place in a reactor analogous to a primary reformer. For this purpose, the reactor comprises both the NH; decomposition device according to the invention and the combustion device according to the invention.

[0168] For this purpose, the NH; decomposition catalyst is preferably arranged in at least one tube through which NH; flows, more preferably at least two tubes, even more preferably at least three tubes (NH; decomposition device). The at least one tube contains the NH; decomposition catalyst. The at least one tube is preferably flowed through from top to bottom with NH;. In a physically separate combustion chamber, a mixture of NH; and H, is preferably burned together with combustion air as combustion gas (combustion device). The gas produced during the catalytic decomposition of

NH; N, formed in addition to H, 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 NH; 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 NH; decomposition device.

[0169] In particularly preferred embodiments of the invention, NH; is preheated before entering the NH; decomposition device according to the invention. As a result of this preheating, the temperature of the NH; before entering the NH; decomposition device according to the invention is preferably at least about 600°C, preferably at least about 630°C. The temperature of the NH; is preferably at most about 850°C, more preferably at most about 820°C. The temperature of the NH; is particularly preferably at

Entry into the NH; decomposition device according to the invention is about 780°C to 820°C, preferably about 800°C. The NH; decomposition device according to the invention and the

The combustion device preferably comprises a reactor designed analogously to a primary reformer. The NH; decomposition catalyst is preferably nickel-based. In preferred embodiments, the

Reaction temperature in the NH; decomposition device, preferably in the at least one tube which contains the NH; decomposition catalyst and through which the NH; is passed, is preferably about 630°C to about 670°C, preferably about 650°C. In other preferred embodiments, this temperature is about 660°C to 700°C, preferably about 680°C. The product gas leaves the reactor (the NH; decomposition device) preferably at a pressure of about 15 bar a to about 25 bar a, preferably about 20 bar a.

[0170] In further particularly preferred embodiments of the invention, the decomposition of NH; takes place in two stages in two NH; decomposition devices through which the gas flows one after the other (see Figure 9). In a pre-reactor (first NH; decomposition device), only a portion of the NH; is initially decomposed. The remaining decomposition of NH; up to the maximum conversion achieved then takes place subsequently.

Bend in a second NH; decomposition device. Preferably, the second NH; decomposition device together with the combustion device according to the invention forms a reactor, as described in more detail above, designed analogously to a primary reformer.

230088P00LU

[0171] Preferably, the NH; is preheated before being introduced into the pre-reactor (first NH; decomposition device) LU103144. Preferably, the temperature of the NH; after heating and upon entry into the pre-reactor (first NH; decomposition device) is about 620°C to about 680°C, more preferably about 650°C. The preheated NH; then enters the pre-reactor, which contains NH; decomposition catalyst and in which a catalytic decomposition of NH; to N, and H, takes place to a certain extent. An intermediate product gas is formed, which still contains considerable residual amounts of non-decomposed NH;, but also already formed N, and H,. As a result of the endothermic decomposition of NH;, the

Intermediate gas preferentially escapes.

[0172] Preferably, the conversion of decomposed NH in the pre-reactor is at most 25%, more preferably at most 20% of the total conversion achieved.

[0173] Preferably, the conversion of decomposed NH in the pre-reactor is at least 10%, more preferably at least 15% of the total conversion achieved.

[0174] After leaving the pre-reactor, the intermediate product gas is preferably heated again before it enters the downstream, second NH; decomposition device. The temperature of the intermediate product gas after renewed heating and upon entry into the second NH; decomposition device is preferably about 620°C to about 680°C, more preferably about 650°C. The remaining decomposition of NH; then takes place in the second NH; decomposition device until the total conversion is achieved.

[0175] In this preferred embodiment of the invention, with the same total conversion, the

Temperature of the intermediate product gas when entering the pre-reactor (first NH; decomposition device) and when entering the second NH; decomposition device should be lower than the temperature of the NH; in single-stage decomposition of NH;, i.e. when only a single NH; decomposition device is flowing through. Due to the lower temperature, nitriding of the pipes occurs to a lesser extent, which increases the service life of the steel that comes into contact with NH;.

[0176] The NH3 decomposition catalyst in the first NH3 decomposition device (pre-reactor) is preferably the same as in the second NH3 decomposition device.

combustion gas

[0177] 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.

[0178] The combustion gas preferably contains NH;. The combustion device according to the invention is therefore preferably an NH; combustion device.

[0179] The combustion gas preferably contains a mixture of H, and NH2, since this mixture produces a medium flame temperature and has better combustion properties than pure NH;

230088P00LU. By using a suitable mixing ratio of H, and NH;, less nitrogen oxide is formed than in the absence of H,.

combustion air

[0180] Preferably, the combustion device (combustion chamber of the reactor) is supplied with combustion air, which is preferably preheated beforehand in at least one heat exchanger. Preferably, this at least one heat exchanger is arranged in the flue gas channel, wherein the combustion air

absorbs heat from the flue gas. Excess heat in the flue gas can thus be used to preheat the combustion air (see Figures 8 and 9, heat exchanger 43 or heat exchanger 45).

[0181] Preferably, the combustion air is preheated in at least two heat exchangers. Preferably, these at least two heat exchangers are both arranged in the flue gas channel, whereby the combustion air absorbs heat from the flue gas. In preferred embodiments of the

In accordance with the invention, a first heat exchanger is arranged in the flue gas duct in the flow direction of the flue gas downstream of the flue gas heat exchanger and preferably serves to preheat the combustion air, whereby the combustion air absorbs heat from the flue gas (see Figures 8 and 9, heat exchanger 43). Preferably, a second heat exchanger is arranged in the flue gas duct in the flow direction of the flue gas upstream of the flue gas heat exchanger and preferably serves to further heat the combustion air, whereby the combustion air again absorbs heat from the

absorbs flue gas (see Figures 8 and 9, heat exchanger 45).

[0182] Preferably, the combustion air is cleaned by a filter before being fed into the system, compressed to the required pressure using a compressor and then passed through at least one 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,

[0183] The product gas leaves the NH; decomposition device at high temperature. In order to

To utilize the heat contained in the product gas, the heat exchanger is located downstream of the

Preferably, at least one heat exchanger is arranged in the NH; decomposition device, through which the product gas flows before the product gas is supplied to a purification of H,. Preferably, at least two heat exchangers, more preferably at least three heat exchangers, even more preferably at least four heat exchangers are flowed through by the product gas before the product gas is supplied to a purification of H,

H, is supplied.

[0184] Preferably, the temperature of the product gas on exiting the NH3 decomposition device is in the range of about 650+100°C, more preferably about 650+50°C.

230088P00LU

[0185] Preferably, a product gas heat exchanger is arranged as part of an H,O evaporation device downstream of the NH; decomposition device in the flow direction of the product gas. In this way, hydrogen embrittlement can be avoided. The product gas heat exchanger is preferably in operative connection with a steam drum. The H,O evaporation device thus preferably comprises the product gas heat exchanger and the steam drum. In this case, preference is given to

Heat contained in the hot product gas leaving the NH; decomposition device is absorbed by water in the product gas heat exchanger and used to heat or generate water vapor in the water vapor drum. The water vapor drum is preferably fed with demineralized water. The water vapor is fed into the

NH; evaporation device, in which NH; absorbs heat from the water vapor and evaporates. After leaving the NH; evaporation device, the NH; is then further heated and fed to the NH; decomposition device.

[0186] Preferably, the temperature of the product gas at the outlet from the product gas heat exchanger is in the range of about 350+100°C, more preferably about 350+50°C.

[0187] Preferably, a further heat exchanger is arranged in the flow direction of the product gas downstream of the product gas heat exchanger (H2O evaporation device), which preferably serves to heat the NH3 to the desired temperature at the inlet to the NH3 decomposition device or to an intermediate temperature even lower than this.

[0188] Preferably, the temperature of the product gas at the outlet from the product gas heat exchanger is in the range of about 150+100°C, more preferably 150+50°C.

[0189] Since the temperature of the process gas stream is already comparatively low after the product gas has flowed through the product gas heat exchanger (H,O evaporation device) and the further heat exchanger, it is preferred to arrange a preheater for water, which is used in steam generation, in the flow direction of the product gas downstream of the product gas heat exchanger (H,O evaporation device) and preferably also in the flow direction of the product gas downstream of the further heat exchanger (cf. Figures 8 and 9: product gas

Heat exchanger 26; further heat exchanger 20; preheater 28).

[0190] Preferably, the temperature of the product gas at the outlet from the preheater is in the range of about 90+50°C, more preferably about 90+25°C.

[0191] Preferably, an additional heat exchanger is arranged in the flow direction of the product gas, preferably in the flow direction of the product gas downstream of the preheater for water, which preferably serves to heat water and brings the product gas to the desired temperature for a preferably subsequent purification of H 2 (cf. Figures 8 and 9, process cooler 29). The heat absorbed by the water in this process is preferably used according to the invention for preheating liquid NH 3 .

230088P00LU

[0192] Preferably, the temperature of the product gas at the outlet from the additional heat exchanger is in the range of about 35-15°C, more preferably about 35+10°C.

Product gas - residual amounts of undecomposed NH;

[0193] The recovery of NH; preferred 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 reactant.

[0194] NH; can be separated technically in various ways, e.g. membrane separation,

Adsorption and condensation, although these processes require high pressures and are therefore energy-intensive.

[0195] In preferred embodiments of the invention, the absorption of NH; in water can be carried out at process-technical pressures. In order to separate the mixture of NH; and water by rectification, however, water vapor is required as an energy carrier. Since according to the invention the combustion gas also comprises NH;, preferably in a mixture with H,, in order to generate the required

Due to the steam required for rectification, additional NH; or H, is burned, which leads to a reduction in the overall yield of H,.

[0196] If water vapor is required not only for heating and evaporating NH3, but also for additional purposes, i.e. if there is another consumer of water vapor, for example an evaporator of an NH3 scrubber, it may be advantageous to use the combination of

Product gas heat exchanger and flue gas heat exchanger to be expanded by a third heat exchanger in which water absorbs additional heat from the product gas or the flue gas.

[0197] In other preferred embodiments of the invention, a separate recovery of NH; is dispensed with. For this purpose, the reaction parameters are selected so that the greatest possible

Conversion is achieved and the amount of undecomposed NH; in the product gas is kept as low as possible. However, this is hardly possible with an economical process control simply by using a high reaction temperature, since the equilibrium temperature would then have to be 900°C or even higher. If separate recovery of NH; is dispensed with, small residual amounts of undecomposed NH; can be separated by other measures if the process parameters are optimized within economically acceptable limits and the conversion is correspondingly good. For example, according to the invention, the purification of H, from the product gas is preferably carried out by pressure swing adsorption (PSA). Small residual amounts of undecomposed NH; can preferably be separated off during pressure swing adsorption, whereby the recovery of NH; and the purification of H, are combined into a single step.

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

230088P00LU

[0198] The type of purification of H, in the product gas depends on the subsequent technical use of the H,, which determines the quality requirements. Technical H, can remain relatively impure and, for example, have a purity of about 99.7%. If, however, H, is intended for use in fuel cells, a significantly higher purity in the range of, for example, about 99.96% would be necessary.

[0199] In preferred embodiments of the invention, H is purified, for example analogously to air separation by partial condensation. However, this requires the use of a compressor in order to generate the high required inlet pressures of, for example, about 230 bar. Furthermore, upstream adsorptive drying is necessary in order to remove traces of NH 3 and H 2 O.

Furthermore, the separation unit itself is required, which is why this concept is cost-intensive in terms of investment and operation.

[0200] In other preferred embodiments of the invention, H 1 is purified by membranes. However, H 1 and N 1 can be separated from one another with only moderate selectivities and yields. Even for separation via membranes, a high inlet pressure must be created, which requires the use of a compressor.

[0201] According to the invention, H, 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 H,, if required > 99.9%, with a yield of H, of e.g. approx. 85%. As already mentioned, the

Pressure swing adsorption also removes residual amounts of NH3 and H2O in the same step.

[0202] For this purpose, the product gas is preferably cooled to the desired temperature using a process cooler before entering the pressure swing adsorption device. The corresponding amount of

Heat is preferentially absorbed by water in the process cooler (see Figures 8 and 9,

Process cooler 29). The cooling water heated in this way is preferably used according to the invention for preheating

NH; is used in a preheating device in which NH; absorbs heat from the water (see Figure 7, preheating device 70).

[0203] The cooled product gas is then preferably fed to a pressure swing adsorption device, where the gas mixture is separated under pressure by adsorption.

H, - after purification until storage

[0204] The H , separated in this way preferably leaves the pressure swing adsorption device and is preferably brought to an increased pressure with a H , compressor. The compressed H , then preferably flows through a heat exchanger in which cooling water extracts heat from the compressed

H (see Figures 8 and 9, compressor 33 and heat exchanger 34).

230088P00LU

[0205] In preferred embodiments of the invention, the separated H, is then brought to a further increased pressure using a second H, compressor. Preferably, the further compressed H, then flows through a second heat exchanger in which cooling water is also

absorbs heat from the compressed H (see Figures 8 and 9, compressor 35 and heat exchanger 36).

[0206] The cooling water heated in this way is preferably used according to the invention for preheating NH; in a preheating device in which NH; absorbs heat from the water (see Figure 7,

preheating device 70).

[0207] The compressed H , is then discharged from the plant at a pressure of, for example, about 70 bar and stored, for example, in a suitable pressure vessel or directly fed to another

used.

residual gas mixture

[0208] The residual gas mixture remaining after the purification/separation of H,, preferably in the pressure swing adsorption device, typically contains N,, H,O, residual NH; and H>.

[0209] Preferably, the residual gas mixture is fed to the combustion device so that it is available for the

can be used to generate combustion heat.

flue gas

[0210] 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, at least one heat exchanger is preferably arranged 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 to the environment, e.g. via a chimney. Preferably, the flue gas flows through at least two heat exchangers, more preferably at least three heat exchangers, even more preferably at least four heat exchangers, before the flue gas is released to the environment.

[0211] In preferred embodiments, the temperature of the flue gas at the exit from the

Combustion facility in the range of about 850+100°C, more preferably about 850+50°C.

[0212] In other preferred embodiments, the temperature of the flue gas exiting the combustion device is in the range of about 880+100°C, more preferably about 880+50°C.

[0213] Preferably, a first heat exchanger is arranged in the flue gas channel in the flow direction of the flue gas downstream of the combustion device, which is preferably used to heat the NH; to the desired temperature at the inlet into the

NH; decomposition device.

230088P00LU

[0214] Preferably, the temperature of the flue gas at the outlet from the first heat exchanger LU103144 is in the range of about 700+100°C, more preferably about 700+50°C.

[0215] Preferably, a second heat exchanger is arranged downstream of the first heat exchanger in the flow direction of the flue gas, which second heat exchanger preferably serves to heat the combustion air.

[0216] Preferably, the temperature of the flue gas at the outlet from the second heat exchanger is in the range of about 300+100°C, more preferably about 300+50°C.

[0217] Since the temperature of the flue gas stream is already comparatively low after the flue gas has flowed through the first heat exchanger and the second heat exchanger, it is advantageous to have a

Flue gas heat exchanger for water, which is used to generate steam, arranged in the flow direction of the flue gas downstream of the first heat exchanger and preferably also in the flow direction of the flue gas downstream of the second heat exchanger (cf. Figures 8 and 9: first heat exchanger: heat exchanger 22; second heat exchanger: heat exchanger 45;

flue gas heat exchanger 52).

[0218] The flue gas heat exchanger preferably contributes at least part of the heat for the generation of water vapor.

[0219] Preferably, the temperature of the flue gas at the outlet from the flue gas heat exchanger is in the range of about 250+100°C, more preferably about 250+50°C.

[0220] Preferably, in the flow direction of the flue gas, preferably in the flow direction of the

Flue gas downstream of the flue gas heat exchanger, an additional heat exchanger is arranged, which preferably serves to heat combustion air (see Figures 8 and 9, heat exchanger 43).

[0221] Preferably, the temperature of the flue gas at the outlet from the additional heat exchanger is in the range of about 150+100°C, more preferably about 150+50°C

[0222] In preferred embodiments of the invention, when the catalytic decomposition of the NH; takes place in two stages in a first NH; decomposition device and a second NH; decomposition device, a further heat exchanger is preferably arranged downstream of the first heat exchanger in the flow direction of the flue gas and preferably upstream of the second heat exchanger in the flow direction of the flue gas, which heat exchanger is preferably used to heat the intermediate product gas after leaving the first NH; decomposition device (pre-reactor) and before entering the second

NH; decomposition device (together with combustion device analogous to primary reformer) (see Figure 9, further heat exchanger 67).

[0223] Preferably, the temperature of the flue gas at the outlet from the further heat exchanger is in the range of about 450+100°C, more preferably about 450+50°C.

230088P00LU

water or water vapor LU103144

[0224] The flue gas leaving the combustion device represents the largest energy sink in the process after the catalytic decomposition of the NH; and the evaporation of the NH;. The energy recovery from the flue gas is limited by the fact that temperature differences of less than approximately 45 K between the flue gas and the other process-side streams (reactant for the catalytic decomposition, combustion gas, combustion air, water for the generation of water vapor) would require uneconomically large heat exchangers. Therefore, even after all economically viable steps of the process-side heat integration, a certain temperature difference remains between the flue gas and the dew point of the water contained in the flue gas.

[0225] According to the invention, this remaining temperature difference is preferably used to generate heated cooling water, which is then used to preheat NH3.

[0226] For the preheating and subsequent evaporation of NH; the following five configurations are particularly preferred according to the invention:

I. with heat from steam and steam condensate, preferably in countercurrent: 2. additionally with heat from blowdown and from non-evaporated excess boiler feed water; 3. additionally with heat from cooling water, but without using heat from the flue gas and without using heat from the H, compression; the preheating is limited by the existing heat that is removed from the process stream and used to heat cooling water; 4. additionally with heat from the H, compression and from the steam condensate from the NHz

evaporation; to produce liquid heated cooling water at a higher temperature or liquid heated cooling water at a lower temperature; there is more heat available in the heated cooling water than can be used in the process, so that the preheating of the NH3 is limited by the minimum temperature difference between the cooling water and the NH3; and/or 5. additionally with heat from the flue gas, but without using heat from the H3 compression; to produce liquid heated cooling water at a higher temperature or liquid heated cooling water at a lower temperature; there is also more heat available in the heated cooling water than can be used in the process, so that the preheating of the NH3 is limited by the minimum temperature difference between the cooling water and the NH3.

[0227] Demineralized water is preferably fed into the plant as water for the production of steam.

230088P00LU

[0228] Preferably, the water is preheated via a preheater, through which product gas preferably flows and in which the water absorbs heat from the product gas (see Figures 8 and 9, preheater 28). In the flow direction of the product gas, the preheater is preferably arranged downstream of the product gas heat exchanger.

[0229] Preferably, the water after leaving the preheater has a temperature of at least 100°C, more preferably at least 110°C, even more preferably at least 115°C.

[0230] Preferably, the temperature of the water subsequently does not fall below this temperature of at least 100°C, more preferably at least 110°C, even more preferably at least 120°C, before the

Water in the NH; evaporation device according to the invention releases heat to NH; for its evaporation.

[0231] Preferably, air and other gases dissolved in the water are removed in a degasser.

[0232] Preferably, the water is then passed through the flue gas heat exchanger and heated. The flue gas 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.

[0233] Preferably, the water after leaving the flue gas heat exchanger has a temperature of at least 180°C, more preferably at least 200°C, even more preferably at least 220°C.

[0234] Preferably, the temperature of the water subsequently does not fall below this temperature of at least 180°C, more preferably at least 200°C, even more preferably at least 220°C, before the

Water in the NH; evaporation device according to the invention releases heat to NH; for its evaporation.

[0235] A person skilled in the art will recognize that, depending on the temperature and prevailing pressure conditions, the water can be in liquid, gaseous (i.e. as water vapor) or as a two-phase system.

[0236] The steam is then preferably passed into a steam drum (see Figures 1-9, steam drum 60).

[0237] From the steam drum, the water is preferably passed through the product gas heat exchanger and thereby absorbs further heat in order to then preferably be returned to the steam drum. The product gas heat exchanger is arranged in the flow direction of the product gas downstream of the NH3 decomposition device and serves to cool the product gas after leaving the NH3 decomposition device, wherein the heat contained in the product gas

Heat is also used to heat the water vapor.

[0238] The hot steam preferentially leaves the steam drum and is preferably fed into the

NH;-evaporation device. Heat is gained through the condensation of the water vapor in order to evaporate the preheated NH;. After flowing through the NH;-evaporation

230088P00LU device, the water vapor condensate is preferably fed to the preheater, which serves to LU103144

NH; so that the heat contained in the water vapor is used in two stages to heat the NH;. After flowing through the preheater, the water vapor condensate can be drained from the system.

[0239] When steam is produced, a liquid stream is produced at boiling temperature, the so-called "blowdown". The "blowdown" is preferably added to the condensed steam after the

Leaving the NH; evaporator and before entering the preheater (Figure 5).

[0240] Since the process provides heat, it is preferable to recover this heat by producing more than the required amount of boiler feed water and to remove this amount before entering the

H,0 evaporation device and is mixed with the "blowdown". For this purpose, the water vapor leaving the flue gas heat exchanger is preferably divided into two partial flows. A first partial flow is preferably introduced into the water vapor drum. A second partial flow preferably bypasses the water vapor drum via a bypass and is mixed with the "blowdown" (Figure 6).

[0241] In addition to the above-described flow of water or water vapor, other water flows preferably play a role according to the invention.

[0242] Such a preferred water stream according to the invention comprises cooling water, which is preferably taken from a process cooler in the flow direction of the product gas upstream of a pressure swing adsorption device, where it has previously absorbed heat from the product gas (heated cooling water), or from a heat exchanger of a possible H, compressor, where it has previously

Heat from compressed H (heated cooling water).

[0243] Another such water flow preferred according to the invention comprises water which is preferably circulated in a circle and which has previously absorbed heat from the flue gas, for which purpose an additional heat exchanger is preferably in operative connection with a further heat exchanger, wherein these are preferably connected to one another via a ring line through which the water is circulated, preferably with a pump.

Description of the figures

[0244] The invention will be explained below using embodiments with reference to the

Figures explained in more detail. Figures 1 to 16 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. Figures 4, 7, 10 and 12-16 each show only a portion of embodiments according to the invention, which are preferred as preferred developments of all other figures of embodiments according to the invention.

230088P00LU

[0245] A first exemplary flow diagram LU103144 of a system according to the invention is explained below with reference to Figure 1. Liquid NH; is led from tank 10 into NH; evaporation device 14 and evaporated therein. The heat required for this is generated by condensation of

Water vapor is obtained (see below). From the NH; evaporation device 14, the vaporized NH; flows into the NH; decomposition device 24, where the endothermic decomposition of NH; to N, and H, is catalyzed. The heat required to maintain the reaction is generated as combustion heat by burning combustion gas (e.g. NH,/H,/air or CHy/air) and is used as

Heat flow from the combustion device 18 is introduced into the NH; decomposition device 24.

The flue gas obtained during combustion flows through flue gas heat exchanger 52, where

The heat contained in the flue gas is transferred to water, whereby water vapor is obtained. After passing through the flue gas heat exchanger 52, the water vapor is introduced into the water vapor drum 60 and then via line 63 into the NH; evaporation device 14. The NH; is evaporated by the heat released during the condensation of the water vapor in the NH; evaporation device 14 (see above).

[0246] Figure 2 illustrates a variant of the embodiment according to Figure 1, the essential difference being that it is not the heat in the flue gas, but the

Heat in the product gas is used to heat water and to heat steam.

The product gas obtained during the catalytic decomposition flows through product gas heat exchanger 26, whereby heat contained in the product gas is transferred to water, thereby obtaining water vapor.

After passing through the product gas heat exchanger 26, the water vapor is introduced into the water vapor drum 60 and then via line 63 into the NH3 evaporator 14.

[0247] Figure 3 illustrates a variant according to the invention in which both flue gas heat exchanger 52 and product gas heat exchanger 26 are used to heat water or water vapor. Water vapor is passed from the flue gas heat exchanger 52 and the product gas heat exchanger 26 into the water vapor drum 60. From there, the water vapor is then passed through

Line 63 is introduced into NH; evaporator 14.

[0248] Figure 4 illustrates a detail of a variant according to the invention in which liquid

NH; from tank 10 is first fed into preheater 13 and preheated therein by absorbing heat from heated water before the preheated NH; is fed to the NH; evaporation device 14. The heated water used is fed as steam condensate via line 64 from the NH; evaporation device 14 to the preheater 13. In this way, the heat contained in the steam is used in two stages for the heating and subsequent evaporation of NH;. After flowing through the preheater 13, the steam condensate can be discharged from the system, for example.

[0249] Figure 5 illustrates a variant according to the invention which takes into account that when steam is generated at boiling temperature, a liquid stream is also produced as a "blowdown".

230088P00LU According to this preferred embodiment, the "blowdown" is added to the condensed water vapor after leaving the NH; evaporator 14 and before entering the preheater 13.

In the example shown, the "blowdown" is fed via "blowdown" line 68 from water vapor drum 60 into line 64.

[0250] Figure 6 illustrates a variant according to the invention in which the heat released during the formation of the "blowdown" is recovered. In the flue gas heat exchanger 52, more

Water is heated or more steam is generated than is required for the steam drum 60.

The steam leaving the flue gas heat exchanger 52 is then divided into two partial streams. A first partial stream is introduced into the steam drum 60. A second partial stream bypasses the steam drum 60 via bypass 69 and is fed into the "blowdown" line 68.

[0251] Figure 7 illustrates a detail of a variant according to the invention in which the yield of H, is increased by reducing the amount of water vapor produced and instead

The residual heat remaining in the process is reintegrated. This ultimately requires less fuel, which preferably contains H,. According to the variant illustrated in Figure 7, the energy

Gap in the preheating and evaporation of NH; closed by a preheating device 70 fed with cooling water. Water for cooling may be required at various points in the plant, for example in process cooler 29 in the flow direction of the product gas upstream of a

Pressure swing adsorption device 31 or in heat exchangers 34 or 36 of possible H, compressors 33 or 35. The water absorbs process heat and is thereby heated. The absorbed

Heat can be used to preheat liquid NH;.

[0252] Figure 8 illustrates a further variant according to the invention, which is more complex and in which several other systems are integrated. Liquid NH;, 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, evaporated in NH; evaporation device 14 and then flows over

Line 15 to branch 16, where the NH; stream is divided into two partial streams. From

A first partial flow of NH; is fed from branch 16 via line 17 to combustion device 18. A second partial flow of NH; is fed from branch 16 via line 19 through

Heat exchanger 20 and then flows via line 21 through heat exchanger 22, where the NH; is further heated and then flows via line 23 into NH; decomposition device 24, where the

NH; decomposition catalyst is located, so that the catalytic decomposition of NH; takes place there. The

The NH; decomposition device 24 preferably flows from top to bottom. The heat required to maintain the reaction is generated by heating the NH; decomposition device 24 by burning NH; in the combustion device 18.

[0253] After the decomposition of NH;, the product gas formed (comprising N,, H,, H,O and possibly remaining NH;) flows through product gas heat exchanger 26, then heat exchanger 20 in cross-flow, then line 27 and for further cooling a further heat exchanger and preheater 28.

230088P00LU which is operated with water, for example. Finally, the product gas is cooled further by means of a process cooler 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 H, separated in this way leaves the pressure swing adsorption device 31 via line 32, is brought to an increased pressure via a first H, compressor 33, flows through a heat exchanger 34, a second H- compressor 35 for further pressure increase, a second heat exchanger 36 and is discharged from the system at a pressure of, for example, about 70 bar via line 37.

[0254] The residual gas mixture remaining in the pressure swing adsorption device 31 after separation of the H, contains N,, H,O, residual NH; and H, 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.

[0255] Combustion air for the combustion process in the combustion device 18 is supplied via

Filter 40 cleaned, compressed by means of compressor 41, passed via line 42 through heat exchanger 43 and heated, then flows via line 44 and through 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 supplied via line 17 in order to burn it and thus generate combustion heat.

[0256] The hot flue gas from the combustion in combustion device 18 is first

Heat exchanger 22 cooled, whereby heat is obtained for heating the NH; supplied to the NH; decomposition device 24. The flue gas is then passed further through flue gas channel 49 over

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 heat exchanger 52, whereby heat is obtained for heating water, and then flows through 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.

[0257] Water for the production of steam is fed in via line 55, passed through preheater 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 flue gas

Heat exchanger 52 and heated. The flue gas heat exchanger 52 serves to cool the flue gases from the combustion device 18 in the flue gas channel 49, whereby the heat contained in the flue gas

Thermal energy is used to heat the water vapor, which then passes through the

flue gas heat exchanger 52 via line 59 into the steam drum 60. Water can be passed from the steam drum 60 via line 61 through the product gas heat exchanger 26 and thereby absorb further heat energy in order to then be passed via line 62 to the steam drum.

230088P00LU. The product gas heat exchanger 26 is arranged in the outlet line 25 in the flow direction of the product gas downstream of the NH; decomposition device 24 and serves to

Cooling of the product gas after leaving the NH3 decomposition device 24. The heat obtained can thus be used to generate further water vapor.

[0258] The hot steam generated in the steam drum 60 is introduced via line 63 into the upper area of the NH; evaporation device 14. The condensation of the steam generates the heat to evaporate the preheated NH;. After flowing through the NH; evaporation device 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.

[0259] Figure 9 also illustrates another variant according to the invention, which is more complex and in which several other systems are integrated. Some system components correspond to those of the

Figure 8 and are therefore not explained in detail again. Heating and evaporation of the NH; are largely unchanged, as are the plant components and process steps downstream of the

Pressure swing adsorption after separation of the H,. In contrast to the variant according to Figure 8, a total of five heat exchangers are arranged in the flue gas channel 49. Here too, line 21 for heating the NH; leads from heat exchanger 20 to the heat exchanger 22 arranged in the flue gas channel 49. However, after flowing through the heat exchanger 22, the NH; is led through pre-reactor 65, where the NH; cools down. The gas mixture leaving the pre-reactor 65 is then

Line 66 leads to heat exchanger 67, which is installed in flue gas duct 49 in the flow direction of the

flue gas is arranged upstream of heat exchanger 22. There, the gas mixture is heated up and then introduced into NH; decomposition device 24 via line 23. The heating of the combustion air for the combustion device 18 takes place analogously to Figure 8, first by heating via heat exchanger 43 and then by further heating via heat exchanger 45, whereby both heat exchangers 43 and 45 are arranged in the flue gas channel 49. The heating and evaporation of the water supplied for the steam drum 60 takes place via preheater 28 and flue gas heat exchanger 52, which is arranged in the flue gas channel 49, analogously to Figure 8. In the variant according to

In Figure 8, five heat exchangers 67, 22, 45, 52 and 43 are arranged one behind the other in the flow direction of the flue gas in the flue gas duct 49.

[0260] A difference in the reaction procedure according to Figure 9 compared to Figure 3 is that the preheating of the NH; is limited to lower temperatures, whereby the service life of the steel from which the NH; decomposition device 24 is made is extended, even in contact with NH;. For this purpose, the incoming gas stream is first preheated and then part of the catalytic decomposition is carried out in the pre-reactor 65. The gas leaving the pre-reactor 65 is then

230088P00LU the resulting gas mixture is reheated and passed into NH; decomposition device 24, where the remaining catalytic decomposition takes place.

[0261] Figure 10 illustrates a detail of a variant according to the invention in which a further

Heat flow from the system is integrated into the preheating of NH;. Without further measures, the flue gas from the combustion device 18, e.g. when the process is carried out according to Figures 8 and 9, still leaves the flue gas channel 49 at an increased temperature, because a relatively high temperature difference is required for the preheating of the combustion air. According to the variant according to the invention illustrated in Figure 10, this heat in the flue gas is used by being absorbed by another water as a heat transfer medium. For this purpose, another

Heat exchanger 71 is mounted through which water circulates as a heat transfer medium, driven by pump 72. The water is heated in the further heat exchanger 71 and can then be used in additional

Heat exchanger 73 in turn serves as a heat source for NH;, which was advantageously previously preheated by the cooling water in the cooling water-fed preheating device 70.

[0262] Figure 11 schematically illustrates possible sources for heated cooling water 80a to 80d, which is used for preheating and possibly evaporating NH;. According to the invention, only one of these sources for heated cooling water 80a to 80d or several or all of these sources for heated cooling water 80a to 80d can be used for preheating and possibly evaporating NH;

NH; can be used (embodiments (a) to (d) and any combination thereof). Liquid

NH; enters preheater 13 and absorbs heat from water vapor condensate 76. The NH; preheated in this way then enters the NH; evaporation device 14 and absorbs heat from the water vapor 75, which in turn condenses to water vapor condensate 76. (a) In the flow direction of the water vapor condensate 76, a water vapor condensate heat exchanger 83 is arranged downstream of the preheater 13, in which cooling water 80a absorbs heat from the water vapor condensate 76. The evaporated NH; leaves the NH; evaporation device 14 and is fed into two

The combustion device 18 and the NH; decomposition device 24 exchange heat with each other. A first partial flow of the vaporized NH; is burned as combustion gas in the combustion device 18 and leaves it as flue gas 78, from which heat is subsequently recovered in a flue gas heat integration 81 and reintegrated into the process. (b) In the flow direction of the flue gas, a flue gas heat exchanger 52 is arranged downstream of the flue gas heat integration 81, in which cooling water 80b absorbs heat from the flue gas 78. A second partial flow of the vaporized NH; is burned in the NH; decomposition device 24 in

Product gas 79 is decomposed. In order to be heated to the required temperature, this second partial flow of the vaporized NH; is first in a product gas heat integration 82 and then

Bend in the flue gas heat integration 81. The hot NH; then enters the NH; decomposition device 24. After leaving the NH; decomposition device 24, heat is recovered from the product gas 79 in the product gas heat integration 82 and reintegrated into the process. (c) In the flow direction of the product gas, downstream of the product gas heat integration

230088P00LU 82 a process cooler 29 is arranged, in which cooling water 80c absorbs heat from the product gas 78. LU103144

The product gas leaving the process cooler 29 is then fed to a pressure swing adsorption device 31 and the hydrogen separated in this process is compressed in one or more H2 compressors 33, 35. (d) In the flow direction of the hydrogen, one or more heat exchangers 34, 36 are arranged downstream of the one or more H2 compressors 33, 35, wherein

Cooling water 80d absorbs heat from the hydrogen 78.

[0263] Figures 12 to 16 are related to each other and also to Figures 4 to 7, which respectively show the preheating of NH3 in preheater 13 and the subsequent

Bende evaporation of NH; in NH; evaporation device 14. Figures 12 to 16 each illustrate sections of variants according to the invention. In all of these variants, blowdown and boiler feed water (both not shown) are preferably combined with the steam condensate after the steam condensate has left the NH; evaporation device and before it has been returned to the preheater 13.

[0264] Figure 12 illustrates a comparatively simple variant in which liquid NH; from

Tank 10 is first fed into preheater 13 and therein by absorbing heat from heated

Water is preheated before the preheated NH; is fed to the NH; evaporation device 14. The heated water used is discharged as steam condensate via line 64 from the

NH; evaporation device 14 is fed to the preheater 13. In this way, the heat contained in the water vapor is used in two stages for the heating and subsequent evaporation of NH;. After flowing through the preheater 13, the water vapor condensate can be used, for example, from the

system can be derived.

[0265] Figure 13 illustrates a further development of the variant according to Figure 12, wherein in the flow direction of the NH; downstream of the compressor 12 and upstream of the preheater 13 a

Preheating device 70 is arranged. In the preheating device 70, NH; is preheated by absorbing heat from heated water before the preheated NH; is fed to the preheater 13. The heated water can come from different sources, preferably from one of the sources for heated cooling water 80a to 80d explained above in connection with Figure 11, i.e. preferably (a) from a water vapor condensate heat exchanger 83, (b) from a flue gas

heat exchanger 52, (c) from a process cooler 29, or (d) from a heat exchanger 34 and/or 36.

[0266] Figure 14 illustrates another development of the variant according to Figure 12, in which

Flow direction of the NH; downstream of the compressor 12 and upstream of the preheater 13 an additional heat exchanger 73 is arranged, which in turn is preferably connected to a further

Heat exchanger 71 in the flue gas duct is in operative connection. In the additional heat exchanger 73, NH; is preheated by absorbing heat from heated water before the preheated NH; is fed to the preheater 13. The heated water preferably comes from the further heat

230088P00LU exchanger 71, in which water absorbs heat from the flue gas in the flue gas duct. In addition, a water vapor condensate heat exchanger 83 is arranged in the flow direction of the water vapor condensate downstream of the preheater 13, in which cooling water absorbs heat from the water vapor condensate.

[0267] Figure 15 illustrates a further development of the variant according to Figure 13, in which a steam condensate heat exchanger 83 is also arranged in the flow direction of the steam condensate downstream of the preheater 13, in which cooling water absorbs heat from the steam condensate.

[0268] Finally, Figure 16 illustrates a combination of all variants according to Figures 12 to 15.

List of reference symbols:

Tank 35 H,-compressor 11 Line 36 Heat exchanger 12 Pump 37 Output line for hydrogen 13 Preheater 38 Return line 14 NH;-evaporation device 39 Branching line

Line 40 Filter for combustion air 16 Branch 41 Compressor 17 Line 42 Line 18 Combustion device 43 Heat exchanger 19 Line 44 Line

Heat exchanger 45 Heat exchanger 21 Line 46 Line 22 Heat exchanger 47 Branch line 23 Line 48 Branch line 24 NH; decomposition device 49 Flue gas duct

Outlet line 50 Flue gas denitrification unit 26 Product gas heat exchanger 51 Line 27 Line 52 Flue gas heat exchanger 28 Preheater 53 Flue gas compressor 29 Process cooler 54 Chimney

Line 55 Line for the supply of water 31 Pressure swing adsorption device 56 Degasser 32 Line 57 Pump 33 H,-compressor 58 Line 34 Heat exchanger 59 Line

230088P00LU 60 Steam drum LU103144 61 Line 62 Line 63 Line 64 Line 65 Pre-reactor 66 Line 67 Additional heat exchanger 68 Blowdown line 69 Bypass 70 Preheating device 71 Additional heat exchanger 72 Pump 73 Additional heat exchanger 74 Ring line 75 Steam 76 Steam condensate 77 Combustion gas 78 Flue gas 79 Product gas 80a-d Cooling water 81 Flue gas heat integration 82 Product gas heat integration 83 Steam condensate heat exchanger

230088P00LU

LU103144

implementation examples

[0269] The following embodiments serve to explain the invention, but are not to be interpreted as limiting.

[0270] For different process configurations according to the diagrams illustrated in Figures 12 to 16

Variants were simulated for a model system of heat flows and temperatures. The results are summarized in the following table: [TNH)before | - | -34°C | 34°C | 34°C | -34°CT(NH;) after | - | -5°C | 39°C | 27°C | 27°CPower | = | 63kW [| 166 kW | 136 kW | 136 kWT(HOyes | - | 44°C | 44°C | 32°C | 32°C

Tas | | 32°C | 32°C | 20°C | 20°C [TNH)before | - I - [ - [ | 27°C [TNH)after ~~ | - [| - | - | = [624°C]

Power | - | = | - | - [|101kW]T(HOjein | - | - | - | = | 90°C

LTH0) out | - | - | - | = | 40°CFlue gas) before | - | | 143°C | - | 156°CFlue gas) after | - | - | 88°C | - | 86°CPower | = | = [79kW | - |I101kW]THO) in | - | = | 32°C | - | 40°C

THQout | - | - | 4c | - | 90°C

T(H,O condensate) before | - | - | 49°C | 37°C | 105°CT (H,O condensate) to | - | - | 30°C | 30°C | 30°CPower | = | = | 14kW | 8kW | 84kWT(HOjein | - | - | 32°C | 20°C | 20°C

THQout | - | - | 44°C | 32°C | 32°C

230088P00LU

Steam condensate 14 kW 84 kW LU105144 79 kW.

H,-Compressor T4kW | 74 kW

Somme | | 1 1 0 N

[0271] In Examples 4 and 5, heat from the cooling water of the H2 compressor is transferred to the ammonia in cooling water preheater 70.

Claims (15)

230088P00LU Patent claims: LU103144 1. A plant for producing H, by catalytic decomposition of NH; comprising - a combustion device (18) for burning a combustion gas to generate combustion heat and flue gas; - an NH; evaporation device (14) for evaporating liquid NH; by absorbing heat from heated water; - in the flow direction of the NH; downstream of the NH; evaporation device (14) an NH; decomposition device (24) for catalytically decomposing evaporated NH; by absorbing combustion heat generated in the combustion device (18) and by generating a product gas comprising H, and Nj; - in the flow direction of the flue gas downstream of the combustion device (18) a flue gas heat exchanger (52) for heating water by absorbing heat from the flue gas; and/or in the flow direction of the product gas downstream of the NH3 decomposition device (24) a product gas heat exchanger (26) for heating water by absorbing heat from the product gas; and - a line (63) for the heated water from the flue gas heat exchanger (52) and/or from the product gas heat exchanger (26) to the NH3 evaporation device (14). 2. The plant according to claim 1, wherein (1) the plant is designed for a throughput based on H, of at least 500 mol-h-!; and/or (ii) the plant comprises a tank (10) for liquid NH; which has a volume of at least 50 m3; and/or (iii) the NH3 decomposition device (24) comprises at least three catalyst beds, each comprising NH3 decomposition catalyst; and/or (iv) the NH3 decomposition device comprises 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; and/or (v) the combustion device (18) comprises at least three burners for combusting the combustion gas; and/or (vi) the flue gas heat exchanger (52) and/or the product gas heat exchanger (26) is a tube heat exchanger or a tube bundle heat exchanger. 230088P00LU 3. The plant according to claim 1 or 2, wherein the plant comprises a preheater (13) in the flow direction of the NH; upstream of the NH; evaporator (14) for heating NH; by absorbing heat from water which exits the NH; evaporator (14). 4. The plant according to one of the preceding claims, wherein the plant comprises a preheating device (70) for preheating NH; by absorbing heat from heated cooling water in the flow direction of the NH; upstream of the NH; evaporation device (14), preferably upstream of the optionally present preheater (13). 5. The plant according to claim 4, wherein the heated cooling water - emerges from a process cooler (29) in the flow direction of the product gas upstream of a pressure swing adsorption device (31); and/or - from a heat exchanger (34) of an H, compressor (33); and/or - from a water vapor condensate heat exchanger (83) in the flow direction of the water vapor condensate downstream of the NH; evaporation device (14), preferably downstream of the preheater (13) if present. 6. The system according to one of the preceding claims, wherein the system - in the flow direction of the NH; upstream of the NH; evaporation device (14), preferably upstream of the optionally present preheater (13), preferably downstream of the optionally present preheating device (70), an additional heat exchanger (73) for preheating NH; by absorbing heat from water; and - in the flow direction of the flue gas downstream of the flue gas heat exchanger (52) a further heat exchanger (71) for heating the water by absorbing heat from the flue gas. 7. The system according to claim 6, wherein the additional heat exchanger (73) and the further heat exchanger (71) are connected to one another via a ring line (74) for circulating the water. 8. Use of a plant according to one of the preceding claims for the production of H,. 230088P00LU 9. A process for producing H, by catalytic decomposition of NH; comprising the LU103144 steps: (a) burning a combustion gas to produce heat of combustion and flue gas; (e) evaporating liquid NH; by absorbing heat from heated water; (f) catalytically decomposing NH vaporized in step (e) by absorbing heat of combustion generated in step (a) and producing a product gas comprising H, and Ny; and (g) heating water by absorbing heat from the flue gas generated in step (a) and/or from the product gas generated in step (f); and using the heated water in step (e). 10. The process according to claim 9, wherein (1) in step (f) a throughput based on H, of at least 500 mol-h"! is achieved; and/or (ii) in step (e) the liquid NH; is taken from a tank with a volume of at least 50 m3; and/or (iii) in step (f) the catalytic decomposition of NH; takes place on at least three catalyst beds, each of which comprises NH; decomposition catalyst; and/or (iv) in step (f) the catalytic decomposition takes place on at least one catalyst bed, which comprises NH; decomposition catalyst, the length of the catalyst bed in the flow direction for NH; being at least 1.0 m; and/or (v) in step (a) the combustion of the combustion gas takes place with the aid of at least three burners; and/or (vi) the heating in step (g) in a Heat exchangers are selected from tube heat exchangers and tube bundle heat exchangers. 11. The process of any preceding claim, wherein the process comprises the additional step of: (d) heating NH3 by absorbing heat from water obtained by step (e). 12. The method according to any one of the preceding claims, wherein the method comprises the additional step: 230088P00LU (b) Preheating of NH3; by absorption of heat from heated cooling water. LU103144 13. The process of claim 12, wherein the heated cooling water has previously absorbed heat from the product gas before performing pressure swing adsorption and/or from H after compression thereof. 14. The process according to any preceding claim, wherein the process comprises the additional step of: (c) preheating NH3; by absorbing heat from water; and heating the water thus obtained by absorbing heat from the flue gas. 15. The method of claim 14, wherein the water is circulated.