AMMONIA SYNTHESIS WITH CO2-NEUTRAL HYDROGEN

Description

[0001] The invention relates to a device and a method for CO2-neutral hydrogen production and subsequent processing into ammonia.

[0002] Today, most of the hydrogen for ammonia synthesis is produced from methane via steam reforming. Due to the large quantity of ammonia produced, this has a significant impact on global CO₂ emissions.

[0003] It is therefore desirable to reduce CO2 emissions. One possibility under discussion is the production of hydrogen via electrolysis using electricity from renewable energy sources, such as solar power. However, due to the high energy demand for the electrochemical splitting of water, this process is energetically inefficient and therefore comparatively expensive. Nevertheless, it has significant merit in converting, for example, solar power into ammonia, as an energy storage medium that is easy to store, transport, and recycle.

[0004] However, in order to meet the high demand, particularly in the fertilizer industry, in a cost-sensitive manner, the search for alternatives makes sense.

[0005] The thermal decomposition of hydrocarbons and the synthesis of ammonia are known from US 7 094 384 B1.

[0006] WO 2002 038 499 A1 discloses a process for producing ammonia from a nitrogen-hydrogen mixture from natural gas.

[0007] The synthesis of ammonia is known from US 2019 0144768 A1.

[0008] The purpose of the invention is to provide a cost-effective but CO2-free hydrogen source for large-scale ammonia synthesis.

[0009] This problem is solved by the device with the features specified in claim 1 and by the method with the features specified in claim 9. Advantageous embodiments are described in the dependent claims, the following description, and the drawings.

[0010] The ammonia synthesis device according to the invention serves to produce hydrogen and to convert the hydrogen into ammonia. The ammonia synthesis device includes a converter for converting nitrogen and hydrogen to ammonia. Such converters are known to those skilled in the art and usually operate according to the Haber-Bosch process, i.e., at elevated temperature and high pressure over a suitable catalyst. Furthermore, the ammonia synthesis device includes a separation device for separating the ammonia from the gas stream. This is also known from the classic Haber-Bosch process. The ammonia synthesis device has a reactant inlet and a product outlet, while the separation device has a gas mixture inlet and a reactant gas outlet.The product outlet of the ammonia synthesis device is connected to the gas mixture inlet of the separation device, and the reactant gas outlet of the separation device is connected to the reactant inlet of the ammonia synthesis device. This recycles the unreacted hydrogen-nitrogen gas mixture, as is known from the classic Haber-Bosch process. The product outlet of the ammonia synthesis device is connected to the gas mixture inlet of the separation device via a first heat exchanger. This allows the heat generated during the exothermic ammonia synthesis process to be dissipated.

[0011] According to the invention, the ammonia synthesis device comprises a pyrolysis reactor for converting hydrocarbons into carbon and hydrogen. The pyrolysis reactor has a hydrocarbon inlet and a hydrogen outlet. The hydrogen outlet of the pyrolysis reactor is connected to the reactant inlet of the ammonia synthesis device. Furthermore, the reactant gas outlet of the separation device is connected to the hydrocarbon inlet of the pyrolysis reactor. In a pyrolysis reactor, a hydrocarbon is separated into carbon (solid) and hydrogen (gaseous). In contrast to the currently common process of steam reforming and a subsequent water-gas shift reaction, this process produces no CO₂, but rather carbon in solid form. This carbon can be stored relatively safely, thus reliably avoiding CO₂ emissions. The carbon can also be further utilized in a manner that does not cause CO₂ emissions.

[0012] Since pyrolysis is not complete, a certain amount of hydrocarbons can remain in the hydrogen stream. Because a cycle then exists between the converter and the separation unit in the ammonia synthesis process, these hydrocarbons would accumulate over time. To solve this problem, a portion of the stream is separated between the separation unit and the converter and returned to the pyrolysis reactor, where the hydrocarbons can be pyrolyzed. This results in a low but stable level of hydrocarbons in the ammonia synthesis cycle.

[0013] Another advantage is that, unlike steam reforming, pyrolysis does not produce carbon monoxide. Therefore, a device for converting carbon monoxide to methane between the steam reformer and the actual Haber-Bosch process is not required.

[0014] In a further embodiment of the invention, a methanizer is arranged downstream of the pyrolysis reactor and upstream of the converter. For example, with pure methane as the feedstock, this step, which is usually necessary after steam reforming, would be unnecessary, since carbon monoxide, which acts as a catalyst poison, cannot be produced without oxygen. However, there are natural gas deposits that contain a proportion of carbon dioxide and / or carbon monoxide. When using such a feedstock, the use of a methanizer to convert any carbon monoxide present with hydrogen to methane and carbon dioxide would be advantageous in order to protect the catalyst in the converter.

[0015] In a further embodiment of the invention, the ammonia synthesis reactant gas stream leaving the separation device is divided by means of an adjustable valve into a first partial stream to the converter and a second partial stream to the pyrolysis reactor. Particularly preferably, the adjustable valve is connected to a control device, wherein the control device is connected to an analysis device, the analysis device being arranged within the ammonia synthesis reactant gas stream between the separation device and the converter, including the first partial stream, or within the ammonia synthesis reactant gas stream between the converter and the separation device. The analysis device is designed for the quantitative detection of hydrocarbons.The quantitative measurement of hydrocarbons includes both direct measurement of the hydrocarbon concentration and measurement of a parameter correlated with the hydrocarbon concentration, such as heat capacity. The higher the hydrocarbon concentration within the Haber-Bosch cycle, the greater the proportion of the second partial flow relative to the first partial flow, as the control device adjusts the regulating valve accordingly.

[0016] In a further embodiment of the invention, the ammonia synthesis device includes an air separation unit. The air separation unit has a nitrogen outlet, which is connected to the reactant inlet of the ammonia synthesis device. Preferably, the nitrogen outlet of the air separation unit is connected to the reactant inlet of the ammonia synthesis device via a nitrogen compressor. The air separation unit further includes an oxygen outlet. The oxygen can either be used in other processes or simply released into the ambient air. Preferably, the air separation unit includes a membrane for air separation, as this is more energy-efficient than air separation according to the Linde process. Alternatively, nitrogen could, for example, also be obtained from the evaporation of liquid nitrogen.

[0017] In a further embodiment of the invention, the nitrogen outlet of the air separation device is connected to the reactant inlet of the ammonia synthesis device via an oxygen filter device. Since it cannot be guaranteed that the hydrogen stream contains no hydrocarbons after a pyrolysis process, it would be critical if oxygen were introduced even in low concentrations, as this could produce carbon monoxide, which, as a catalyst poison, must be avoided. An oxygen filter device can, for example, have a large surface area of ​​a readily corrosive material, such as a base metal. This chemically binds any oxygen present to the surface. The effect can be enhanced by a magnetic field, since oxygen is paramagnetic and nitrogen is diamagnetic.

[0018] In a further embodiment of the invention, the nitrogen outlet of the air separation device is connected to the reactant inlet of the ammonia synthesis device via the first heat exchanger. In this way, it is comparatively easy to bring the nitrogen flow to the temperature it should have when fed to the converter.

[0019] In a further embodiment of the invention, the first heat exchanger is connected to a heat exchange fluid system. The nitrogen outlet of the air separation device is connected via the second heat exchanger to the reactant inlet of the ammonia synthesis device. Furthermore, the hydrocarbon inlet of the pyrolysis reactor is connected to a hydrocarbon source, and this hydrocarbon inlet is connected to a hydrocarbon source via a third heat exchanger. The second and third heat exchangers are connected to the heat exchange fluid system. This makes it possible to transfer the heat from the first heat exchanger to the second and third heat exchangers via a heat exchange fluid, thus heating both reactant streams.

[0020] In a further embodiment of the invention, the hydrocarbon inlet of the pyrolysis reactor is connected to a hydrocarbon source, wherein the hydrocarbon inlet of the pyrolysis reactor is connected to a hydrocarbon source via the first heat exchanger.

[0021] In a further embodiment of the invention, the hydrogen outlet of the pyrolysis reactor is connected to the reactant inlet of the ammonia synthesis device via a first compressor. Furthermore, the reactant gas outlet of the separation device is connected to the hydrocarbon inlet of the pyrolysis reactor via an expansion device. The first compressor is coupled to the expansion device. The Haber-Bosch process typically operates at very high pressures to shift the equilibrium towards the product ammonia. Pyrolysis, however, is often carried out at lower pressures. To utilize the energy released by the gas returned to the pyrolysis reactor when it is depressurized from high pressure to the lower pressure level of the pyrolysis reactor, the first compressor is coupled to the expansion device, for example, via a single common shaft.

[0022] In another embodiment of the invention, the pyrolysis reactor is designed for a pressure of 1 bar to 20 bar and a temperature of 600 °C to 1500 °C. A pressure of 2 bar to 10 bar is particularly preferred. Regarding temperature, there are various optimal temperature ranges, which are attributable to different types of pyrolysis. The pyrolysis reactor preferably incorporates a molten metal, a moving bed, or a plasma. These technologies for the pyrolysis of hydrocarbons have been shown to be technologically mature for large-scale industrial use. Therefore, the pyrolysis reactor can, for example, be designed for a temperature range of 600 °C to 900 °C. This is optimal, for example, for a molten metal pyrolysis reactor. Alternatively, the pyrolysis reactor can be designed for a temperature range of 900 °C to 1500 °C, preferably 1200 °C to 1500 °C.

[0023] The pyrolysis reactor can preferably be designed in accordance with WO 2019 / 145279 A1.

[0024] In a further embodiment of the invention, the pyrolysis reactor has an electric heater. This makes it possible to avoid CO2 emissions for generating the energy required for pyrolysis by using electricity from renewable energy sources.

[0025] In another aspect, the invention relates to a process for the synthesis of ammonia from a hydrocarbon, wherein the process comprises the following steps: a) Feeding a hydrocarbon into a pyrolysis reactor, b) Pyrolyzing the hydrocarbon to carbon and hydrogen in the pyrolysis reactor, c) Directing the hydrogen from the pyrolysis reactor into a converter, d) Feeding nitrogen into the converter, e) Converting the hydrogen and nitrogen to ammonia in the converter, f) Cooling the ammonia synthesis product gas stream in a first heat exchanger, g) Separating the ammonia from the ammonia synthesis product gas stream in a separation device and obtaining an ammonia synthesis reactant gas stream, h) Dividing the ammonia synthesis reactant gas stream into a first partial stream and a second partial stream, i) Directing the first partial stream into the converter, j) Directing the second partial stream into the pyrolysis reactor.

[0026] Preferably, the method according to the invention is carried out on a device according to the invention.

[0027] In process steps h) and j), a portion of the ammonia synthesis reactant gas stream is recycled to decompose hydrocarbons contained therein and thus prevent enrichment.

[0028] In a further embodiment of the invention, the pyrolysis in step b) is not catalytic. Therefore, a purely thermal pyrolysis is preferably carried out.

[0029] In a further embodiment of the invention, methane is pyrolyzed in step b). Firstly, the pyrolysis of methane is advantageous in itself, and secondly, methane is also the main fuel used in steam reforming, which is currently employed for ammonia synthesis. Therefore, switching to the process according to the invention is relatively simple and, when using the existing supply infrastructure, can significantly reduce CO2 emissions.

[0030] In a further embodiment of the invention, when the hydrocarbon is supplied in step a), it is heated by means of the energy extracted from the ammonia synthesis product gas stream in the first heat exchanger.

[0031] In a further embodiment of the invention, when nitrogen is supplied in step d), it is heated by means of the energy extracted from the ammonia synthesis product gas stream in the first heat exchanger.

[0032] In a further embodiment of the invention, the hydrogen flow is compressed in step c) when it is directed from the pyrolysis reactor into the converter.

[0033] In a further embodiment of the invention, the second partial flow is expanded, and the energy gained through expansion is used to compress the hydrogen flow. This can preferably be achieved by coupling the first compressor and the expansion device, for example, via a common shaft.

[0034] In a further embodiment of the invention, the pyrolysis reactor and the converter are operated at the same pressure. This embodiment is particularly preferred because it avoids energy losses due to compression and decompression. On the other hand, this embodiment places very high demands on the pyrolysis reactor to prevent soot formation in the gas phase, since the comparatively high pressure and the resulting smaller average distance between molecules in the gas phase make the risk of carbon particle formation in the gas phase comparatively high.

[0035] In a further embodiment of the invention, the ammonia synthesis reactant gas stream is divided in step h) depending on the hydrocarbon content of the ammonia synthesis reactant gas stream. In particular, the hydrocarbon content in the ammonia synthesis reactant gas stream or also in the ammonia synthesis product gas stream is detected directly or indirectly. Direct detection would be possible, for example, using infrared (IR) technology, while indirect detection would be possible, for example, using thermal conductivity measurement. The higher the detected hydrocarbon content, the higher the proportion of the second partial stream is set.

[0036] In a further embodiment of the invention, the pyrolysis reactor is electrically heated. This makes the use of energy from a renewable energy source, and thus without CO₂ emissions, particularly easy. The ammonia synthesis device preferably includes a wind turbine, a solar power system, and an energy storage system. This energy mix and the intermediate storage enable relatively reliable continuous operation. If necessary, electrical energy can be drawn from a public grid.

[0037] In a further embodiment of the invention, the carbon produced in step b) is deposited, i.e., stored permanently. This reliably and permanently prevents the carbon from being released into the atmosphere in the form of CO2.

[0038] The device according to the invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. Fig. 1 first embodiment Fig. 2 second embodiment Fig. 3 third embodiment Fig. 4 fourth example Fig. 5 fifth embodiment Fig. 6 sixth embodiment

[0039] Identical components are provided with the same reference numerals in the following exemplary embodiments.

[0040] The first embodiment is described in more detail below; the differences are discussed in the subsequent embodiments.

[0041] In Fig. 1 Figure 1 shows a first embodiment of an ammonia synthesis device 10 according to the invention. The ammonia synthesis device 10 has a hydrocarbon source 150, for example, a connection to a methane gas network. The hydrocarbon is fed into a pyrolysis reactor 90 via a hydrocarbon inlet 100 and thermally converted there to carbon and hydrogen, for example, at 1200 °C to 1500 °C. For example, the pyrolysis reactor is designed as a moving-bed reactor, with cold hydrocarbon being introduced at the bottom. This rises while the hydrocarbon is heated by carbon coming in countercurrently, whereby the carbon cools down again. In the middle of the pyrolysis reactor 90, the carbon particles are electrically heated, which leads to pyrolysis of the hydrocarbon and thus to carbon growth.As the hydrogen continues to rise, it heats the oncoming carbon, preferably cooling it to the temperature of the Haber-Bosch process. The hydrogen exits the pyrolysis reactor 90 through the hydrogen outlet 110. The hydrogen stream 190 is compressed by the first compressor 160 and fed to the reactant inlet 40 of the converter 20. Since the hydrogen stream 190, unlike in steam reforming, does not contain nitrogen, the nitrogen is supplied separately. For this purpose, the ammonia synthesis device 10 includes an air separation device 120. The nitrogen exits the air separation device 120 via the nitrogen outlet 130. In the example shown, the nitrogen stream is routed to the reactant inlet 40 of the converter 20 via an optional oxygen filter device 140. In the converter 20, nitrogen and hydrogen are converted to ammonia.The ammonia synthesis product gas stream 210 leaves the converter 20 via product outlet 50 and is fed into the separation device 30 via the first heat exchanger 80 and the gas mixture inlet 60 of the separation device 30. Here, the product ammonia is separated and fed, for example, to a urea synthesis process via ammonia outlet 230. What remains is a mixture of unreacted hydrogen and unreacted nitrogen, which may contain hydrocarbons that were not or not completely converted in the pyrolysis reactor. This mixture leaves the separation device 30 as ammonia synthesis reactant gas stream 200 via reactant outlet 70. The majority of the ammonia synthesis reactant gas stream 200 is fed directly back into the reactant inlet 40 of the converter 20 as the first partial stream 240.Another portion of the ammonia synthesis reactant gas stream 220 is separated as a second partial stream 250 at valve 270 and fed back to the hydrocarbon inlet 100 of the pyrolysis reactor 90 as a second partial stream 250. Since ammonia synthesis typically takes place under much higher pressures, an expansion device 170 is arranged in the second partial stream 250, which is connected to the first compressor 160 via a coupling to utilize the released energy. To discharge the carbon from the pyrolysis reactor 90, it has a carbon outlet 260.

[0042] As already described, the following will only address the differences compared to the first example.

[0043] The in Fig. 2 The second embodiment shown differs from the first embodiment in that the nitrogen flow is passed directly through the first heat exchanger 80, and is thus heated directly by the process heat of the ammonia synthesis.

[0044] In Fig. 3 The third embodiment is shown, in which the hydrocarbon from the hydrocarbon source 150 is passed directly through the first heat exchanger 80 and thus heated. This allows the carbon exiting from the carbon outlet 260 to be comparatively warmer, which is why it could be used to heat the nitrogen stream 200, although this is not shown here for the sake of simplicity.

[0045] The in Fig. 4 The fourth embodiment shown, in addition to the first embodiment, features a second heat exchanger 280 in the nitrogen stream 200 and a third heat exchanger 290 for heating the hydrocarbon between the hydrocarbon source 150 and the pyrolysis reactor 90. The first heat exchanger 80, the second heat exchanger 280, and the third heat exchanger 290 are connected to each other via a heat exchange fluid system, which has been omitted here for simplicity. Thus, the process heat generated can be transferred to both reactant streams.

[0046] Fig. 5 Figure 5 shows a fifth embodiment in which the pyrolysis reactor 90 operates at the same pressure level as the converter 20. For this purpose, the first compressor has been moved from the hydrogen stream 190 and is now arranged between the hydrocarbon source 150 and the pyrolysis reactor 90; the expansion device 170 and thus also the coupling 180 are omitted. Additionally, a second compressor 300 is arranged in the nitrogen stream 200, which is preferably also present in the other embodiments.

[0047] The sixth embodiment is in Fig. 6This embodiment differs from the first embodiment in that the nitrogen stream does not flow into the hydrogen stream 190 and thus into the reactant inlet 40 of the converter 20, but rather into the hydrocarbon inlet 100 of the pyrolysis reactor 90. The advantage of this embodiment is that it reduces the probability of collisions between hydrocarbon molecules and thus soot formation. The disadvantage is that the nitrogen must also be heated to the pyrolysis temperature. However, this energy can be recovered at the end of the pyrolysis reactor 90. Reference sign

[0048] 10 Ammonia synthesis device 20 Converter 30 Separation device 40 Reactant inlet 50 Product outlet 60 Gas mixture inlet 70 Reactant gas outlet 80 First heat exchanger 90 Pyrolysis reactor 100 Hydrocarbon inlet 110 Hydrogen outlet 120 Air separation device 130 Nitrogen outlet 140 Oxygen filter device 150 Hydrocarbon source 160 First compressor 170 Expansion device 180 Coupling 190 Hydrogen flow 200 Nitrogen flow 210 Ammonia synthesis product gas flow 220 Ammonia synthesis reactant gas flow 230 Ammonia outlet 240 First partial flow 250 Second partial flow 260 Carbon outlet 270 Valve 280 Second heat exchanger 290 Third heat exchanger 300 Second compressor

Claims

1. An ammonia synthesis apparatus (10) for producing hydrogen and for converting the hydrogen into ammonia, wherein the ammonia synthesis apparatus (10) comprises a converter (20) for converting nitrogen and hydrogen into ammonia, wherein the ammonia synthesis apparatus (10) comprises a separation apparatus (30) for separating the ammonia from the gas stream, wherein the ammonia synthesis apparatus (10) has a reactant inlet (40) and a product outlet (50), wherein the separation apparatus (30) has a gas mixture inlet (60) and a reactant gas outlet (70), wherein the product outlet (50) of the ammonia synthesis apparatus (10) is connected to the gas mixture inlet (60) of the separation apparatus (30), wherein the reactant gas outlet (70) of the separation apparatus (30) is connected to the reactant inlet (40) of the ammonia synthesis apparatus, wherein the product outlet (50) of the ammonia synthesis apparatus (10) is connected to the gas mixture inlet (60) of the separation apparatus (30) via a first heat exchanger (80), characterized in that the ammonia synthesis apparatus (10) comprises a pyrolysis reactor (90) for conversion of hydrocarbon into carbon and hydrogen, wherein the pyrolysis reactor (90) has a hydrocarbon inlet (100) and a hydrogen outlet (110), wherein the hydrogen outlet (110) of the pyrolysis reactor (90) is connected to the reactant inlet (40) of the ammonia synthesis apparatus (10), wherein the reactant gas outlet (70) of the separation apparatus (30) is connected to the hydrocarbon inlet (100) of the pyrolysis reactor (90).

2. The ammonia synthesis apparatus (10) as claimed in claim 1, characterized in that the ammonia synthesis apparatus (10) comprises an air separation apparatus (120), wherein the air separation apparatus (120) comprises a nitrogen outlet (130), wherein the nitrogen outlet (130) of the air separation apparatus (120) is connected to the reactant inlet (40) of the ammonia synthesis apparatus (10).

3. The ammonia synthesis apparatus (10) as claimed in claim 2, characterized in that the nitrogen outlet (130) of the air separation apparatus (120) is connected to the reactant inlet (40) of the ammonia synthesis apparatus (10) via an oxygen filter apparatus (140).

4. The ammonia synthesis apparatus (10) as claimed in either of claims 2 to 3, characterized in that the nitrogen outlet (130) of the air separation apparatus (120) is connected to the reactant inlet (40) of the ammonia synthesis apparatus (10) via the first heat exchanger (80).

5. The ammonia synthesis apparatus (10) as claimed in either of claims 2 to 3, characterized in that the first heat exchanger (80) is connected to a heat transfer fluid system, wherein the nitrogen outlet (130) of the air separation apparatus (120) is connected to the reactant inlet (40) of the ammonia synthesis apparatus (10) via a second heat exchanger (280), wherein the hydrocarbon inlet (100) of the pyrolysis reactor (90) is connected to a hydrocarbon source (150), wherein the hydrocarbon inlet (100) of the pyrolysis reactor (90) is connected to a hydrocarbon source (150) via a third heat exchanger (290), wherein the second heat exchanger (280) and the third heat exchanger (290) are connected to the heat transfer fluid system.

6. The ammonia synthesis apparatus (10) as claimed in any of claims 1 to 4, characterized in that the hydrocarbon inlet (100) of the pyrolysis reactor (90) is connected to a hydrocarbon source (150), wherein the hydrocarbon inlet (100) of the pyrolysis reactor (90) is connected to a hydrocarbon source (150) via the first heat exchanger (80).

7. The ammonia synthesis apparatus (10) as claimed in any of the preceding claims, characterized in that the hydrogen outlet (110) of the pyrolysis reactor (90) is connected to the reactant inlet (40) of the ammonia synthesis apparatus (10) via a first compressor (160), wherein the reactant gas outlet (70) of the separation apparatus (30) is connected to the hydrocarbon inlet (100) of the pyrolysis reactor (90) via a decompression apparatus (170), wherein the first compressor (160) is coupled to the decompression apparatus (170).

8. The ammonia synthesis apparatus (10) as claimed in any of the preceding claims, characterized in that the pyrolysis reactor (90) is configured for a pressure of 1 bar to 20 bar and a temperature of 600 °C to 1500 °C.

9. A process for synthesis of ammonia from a hydrocarbon, wherein the process comprises the steps of: a) supplying a hydrocarbon into a pyrolysis reactor (90), b) pyrolyzing the hydrocarbon to afford carbon and hydrogen in the pyrolysis reactor (90), c) passing the hydrogen from the pyrolysis reactor (90) into a converter (20), d) supplying nitrogen to the converter (20), e) converting the hydrogen and the nitrogen into ammonia in the converter (20), f) cooling the ammonia synthesis product gas stream (210) in a first heat exchanger (80), g) separating the ammonia from the ammonia synthesis product gas stream (210) in a separation apparatus and obtaining an ammonia synthesis reactant gas stream (220), h) dividing the ammonia synthesis reactant gas stream (220) into a first substream (240) and a second substream (250), i) passing the first substream (240) into the converter (20), j) passing the second substream (250) into the pyrolysis reactor (90).

10. The process as claimed in claim 9, characterized in that during the supplying of the hydrocarbon in step a), said hydrocarbon is heated using the energy withdrawn from the ammonia synthesis product gas stream (210) in the first heat exchanger (80).

11. The process as claimed in either of claims 9 to 10, characterized in that during the supplying of the nitrogen in step d), said nitrogen is heated using the energy withdrawn from the ammonia synthesis product gas stream (210) in the first heat exchanger (80).

12. The process as claimed in any of claims 9 to 11, characterized in that the hydrogen stream (190) is compressed during the passing of said stream from the pyrolysis reactor (90) into the converter (20) in step c).

13. The process as claimed in claim 12, characterized in that the second substream (250) is decompressed, wherein the energy obtained via the decompressing is utilized for compressing the hydrogen stream (190).

14. The process as claimed in any of claims 9 to 11, characterized in that the pyrolysis reactor (90) and the converter (20) are operated at the same pressure.

15. The process as claimed in any of claims 9 to 13, characterized in that the dividing of the ammonia synthesis reactant gas stream (220) in step h) is carried out depending on the hydrocarbon content of the ammonia synthesis reactant gas stream (220).