Method and system for producing hydrogen and / or ammonia

Abstract

The invention relates to a method (10) for producing hydrogen and / or ammonia, having the following steps: providing a first synthesis gas stream (SG3) comprising hydrogen, carbon monoxide and carbon dioxide; providing a second synthesis gas stream (SG4), which is enriched with hydrogen and carbon dioxide and is depleted of carbon monoxide compared to the first synthesis gas stream (SG3), using the first synthesis gas stream (SG3) or a part thereof; providing a first hydrogen stream (HG1) using hydrogen of the second synthesis gas stream (SG4) and a first pressure swing adsorption unit (204); providing a carbon dioxide stream (CG1) using carbon dioxide of the second synthesis gas stream (SG4) and a carbon dioxide separation unit (205); and processing a first residual gas stream (RG2), or a part thereof, remaining downstream of where the first hydrogen stream (HG1) and the carbon dioxide stream (CG1) are provided in order to obtain a second hydrogen stream (HG2) and a second residual gas stream (RG3). The invention is characterized in that the second residual gas stream (RG3) is returned to a position directly upstream of where the carbon dioxide stream (CG1) is provided.

Description

[0001] Description

[0002] Process and plant for the production of hydrogen and / or ammonia

[0003] Area

[0004] The present disclosure relates to a process and a plant for producing hydrogen and / or ammonia.

[0005] background

[0006] More than 90% of the world's ammonia is currently produced using the Haber-Bosch process. This process converts hydrogen and nitrogen into ammonia at high temperatures and pressures in the presence of an iron catalyst. This process is extremely energy-intensive, with a typical energy consumption of 28 to 49 GJ per ton of ammonia.

[0007] To produce hydrogen, various hydrocarbon-containing feedstocks can be converted using suitable processes such as steam reforming, partial oxidation, autothermal reforming, or a combination of these. In all of these processes, carbon dioxide is produced in at least one flue gas, which in conventional processes is at least partially released into the atmosphere.

[0008] Recently, the production of so-called blue hydrogen has become increasingly important. The aim here is to avoid the release of carbon dioxide into the atmosphere as much as possible through suitable process steps. Typically, the resulting carbon dioxide is separated from flue gas or a precursor mixture of the aforementioned processes using chemical and / or physical scrubbing. After separation, the carbon dioxide can be compressed, purified, and / or liquefied before being deposited, for example, in a final storage facility. This is also referred to as sequestration. There is a need for processes for the production of hydrogen and / or ammonia that at least partially overcome the disadvantages of known processes.

[0009] Overview

[0010] Against this background, processes and systems for producing hydrogen and / or ammonia are proposed with the features of the independent claims. Further embodiments are the subject of the dependent claims and the following description.

[0011] The present disclosure relates to the production of ammonia, but also to the mere production of hydrogen without further conversion or with conversion to compounds other than ammonia.

[0012] The proposed process for producing hydrogen and / or ammonia comprises, but is not limited to, the following steps: providing a first synthesis gas stream comprising hydrogen, carbon monoxide, and carbon dioxide; providing a second synthesis gas stream enriched in hydrogen and carbon dioxide and depleted in carbon monoxide compared to the first synthesis gas stream, using the first synthesis gas stream or a portion thereof; providing a first hydrogen stream using hydrogen from the second synthesis gas stream and by means of a first pressure swing adsorption unit;Providing a carbon dioxide stream using carbon dioxide from the second synthesis gas stream and by means of a carbon dioxide separation unit, and processing a first residual gas stream or a portion thereof remaining downstream of the provision of the first hydrogen stream and the carbon dioxide stream to obtain a second hydrogen stream and a second residual gas stream;

[0013] To further develop and improve such a process, as disclosed, for example, in patent application EP 3 954650 A1, it is proposed to recirculate the second residual gas stream to a position directly upstream of the carbon dioxide stream supply. In this way, the carbon dioxide contained in the second residual gas stream is converted, in particular, into a pure carbon dioxide stream, which is subsequently disposed of, for example, by sequestration.

[0014] The proposed process makes it possible to increase the hydrogen yield and the degree of carbon dioxide separation compared to the state of the art without further separation steps.

[0015] Advantageously, the first residual gas stream is processed by means of a second pressure swing adsorption unit to obtain the second residual gas stream.

[0016] Preferably, the first synthesis gas stream is prepared from a feed gas stream containing one or more hydrocarbons using autothermal reforming or partial oxidation. The feed gas stream can be fed directly to the autothermal reforming or partial oxidation without prior reforming. However, it should not be precluded from converting the feed gas stream in an adiabatic reforming unit into a partially reformed stream, which is then further processed in the autothermal reforming or partial oxidation.

[0017] A preferred development of the process according to the invention provides that the second hydrogen stream, or a portion thereof, is thermally and / or materially utilized within the process itself or externally. Particularly when the second hydrogen stream is obtained by pressure swing adsorption, its thermal utilization is uncritical due to its largely carbon dioxide-free nature. Its material utilization can be achieved, in particular, by recirculation upstream of the first pressure swing adsorption unit, so that the hydrogen contained is largely transferred into the first hydrogen stream.

[0018] It is advisable to arrange a drying unit upstream of the carbon dioxide separation unit to prevent water from being introduced into the carbon dioxide treatment, which is particularly operated cryogenically, where it would lead to blockages. In a proposed embodiment, the method according to the invention comprises providing the second synthesis gas stream and converting carbon monoxide to carbon dioxide and hydrogen using a water-gas shift, in particular using an isothermal, high-temperature, medium-temperature, and / or low-temperature shift. In this way, the hydrogen yield can be increased and a carbon dioxide concentration suitable for separation can be achieved.

[0019] In a proposed embodiment, the method comprises providing the first hydrogen stream downstream of the provision of the carbon dioxide stream.

[0020] The proposed plant for producing hydrogen and / or ammonia comprises a device for providing a first synthesis gas stream comprising hydrogen, carbon monoxide and carbon dioxide, a conversion device for providing a second synthesis gas stream which is enriched in hydrogen and carbon dioxide and depleted in carbon monoxide compared to the first synthesis gas stream, using the first synthesis gas stream or a part thereof, a first pressure swing adsorption unit for providing a first hydrogen stream using hydrogen from the second synthesis gas stream, a carbon dioxide separation unit for providing a carbon dioxide stream using carbon dioxide from the second synthesis gas stream, and a separation device,with which a first residual gas stream remaining downstream of the provision of the first hydrogen stream and the carbon dioxide stream, or a part thereof, can be separated to obtain a second hydrogen stream and a second residual gas stream.

[0021] According to the invention, the device comprises a return device via which the second residual gas stream can be returned to a position directly upstream of the provision of the carbon dioxide stream.

[0022] For further features and advantages of a corresponding system and its embodiments, reference is expressly made to the above explanations concerning the method proposed according to the invention and its embodiments, as these apply equally to this. Drawings

[0023] Figure 1 schematically shows a method disclosed in patent application EP 3 954650 A1, while Figure 2 also schematically illustrates an embodiment of this method according to the invention. In both figures, identical system components and streams are marked with identical reference numerals.

[0024] In the process of Figure 1, a hydrocarbon-containing feed gas stream FG is fed to an endothermic reforming unit 200 and converted there into a partially reformed stream SG1, which is further reformed in an autothermal reforming unit 201 to form the first synthesis gas stream SG3. Heat generated in the autothermal reforming unit 201 is used to heat the endothermic reforming unit 200, as illustrated by the heat stream 202. In particular, the first synthesis gas stream SG3 can be used directly for heating in the endothermic reforming unit 200, i.e., the heat contained in the first synthesis gas stream SG3 can be used for heating in the endothermic reforming unit 200 without further transfer to a heat transport medium.

[0025] The first synthesis gas stream SG3 is fed to a conversion unit 203, in which carbon monoxide contained in the first synthesis gas stream SG3 is converted with water vapor to carbon dioxide and hydrogen. A second synthesis gas stream SG4 obtained in this way, which is enriched in hydrogen compared to the first SG3, is subsequently fed to a first separation device 204, designed as a pressure swing adsorption unit, in order to separate hydrogen HG1 from the second synthesis gas stream SG4 with high purity. Likewise, a first residual gas stream RG1, which is depleted in hydrogen compared to the second synthesis gas stream SG4, is removed from the first separation device

[0026] 204 and fed to a separation unit 205. In the separation unit 205, carbon dioxide is separated in high purity by several compression and cooling steps and is discharged as carbon dioxide stream CG1 from the separation unit

[0027] 205 deducted. In the terminology used here, the first hydrogen stream HG1 is provided using hydrogen from the second synthesis gas stream SG4, and a carbon dioxide stream CG1 is provided using carbon dioxide from the second synthesis gas stream SG4. The carbon dioxide stream CG1 still contains significant residual amounts of methane, which can optionally be removed by distillation of the carbon dioxide stream CG1 (not shown). A resulting pure carbon dioxide product is suitable for the sequestration of the carbon dioxide or for further use, for example, for the synthesis of methanol by reaction with hydrogen generated from electrolysis.

[0028] A second residual gas stream RG2, which is highly depleted in carbon dioxide, can be withdrawn from the separation unit 205. From this second residual gas stream RG2, a second hydrogen stream HG2, which is enriched in hydrogen compared to the second residual gas stream RG2, and a third residual gas stream RG3, which is depleted in hydrogen compared to the second residual gas stream RG2, can be generated in the second separation device 206, which is designed as a membrane separation unit. In Figure 1, the second hydrogen stream HG2 is fed to the autothermal reforming unit 201 as fuel gas. Alternatively, it can also be fed to the first separation device 204.

[0029] In the process designated 10 in Figure 2, a hydrocarbon-containing feed gas stream FG is fed to the adiabatic reforming unit 100 to generate the partially reformed stream SG1. No heat flow is passed from the autothermal reforming unit 201 into the adiabatic reforming unit 100. Also different from the process in Figure 1, the second separation device 206' is designed as a pressure swing adsorption unit, in which a third residual gas stream RG3 and a second hydrogen stream HG2 are obtained from the second residual gas stream RG2. While the second hydrogen stream HG2 is fed to the autothermal reforming unit 201 as fuel gas or used in the first separation device 204, the third residual gas stream RG3 is recirculated immediately upstream of the separation unit 205.

[0030] This means that the carbon dioxide separation rates typically required to produce blue hydrogen can be achieved with minimal equipment expenditure.

Claims

Patent claims 1. Process (10) for producing hydrogen and / or ammonia, comprising the following steps: Providing a first synthesis gas stream (SG3) comprising hydrogen, carbon monoxide and carbon dioxide; Providing a second synthesis gas stream (SG4) which is enriched in hydrogen and carbon dioxide and depleted in carbon monoxide compared to the first synthesis gas stream (SG3), using the first synthesis gas stream (SG3) or a part thereof; Providing a first hydrogen stream (HG1) using hydrogen from the second synthesis gas stream (SG4) and by means of a first pressure swing adsorption unit (204); Providing a carbon dioxide stream (CG1) using carbon dioxide from the second synthesis gas stream (SG4) and by means of a carbon dioxide separation unit (205), and Processing a first residual gas stream (RG2) remaining downstream of the provision of the first hydrogen stream (HG1) and the carbon dioxide stream (CG1) or a part thereof to obtain a second hydrogen stream (HG2) and a second residual gas stream (RG3), characterized in that the second residual gas stream (RG3) is returned to a position directly upstream of the provision of the carbon dioxide stream (CG1).

2. Method (10) according to claim 1, characterized in that the first residual gas stream (RG2) is processed by means of a second pressure swing adsorption unit (206') to obtain the second residual gas stream (RG3).

3. Process (10) according to one of claims 1 or 2, characterized in that the first synthesis gas stream (SG3) is provided from a feed gas stream (FG) containing one or more hydrocarbons using autothermal reforming (201) or partial oxidation.

4. Process (10) according to claim 3, characterized in that the feed gas stream (FG) is fed to the autothermal reforming (201) or the partial oxidation without prior reforming.

5. Process (10) according to claim 3, characterized in that a product stream (SG1) for feeding into the autothermal reforming (201) or the partial oxidation is formed from the feed gas stream (FG) in an adiabatic reforming unit (200).

6. The method (10) according to any one of claims 1 to 3, characterized in that the first hydrogen stream (HG1) is provided upstream of the provision of the carbon dioxide stream (CG1).

7. Process (10) according to any one of the preceding claims, characterized in that the provision of the second synthesis gas stream (SG4) comprises the conversion of carbon monoxide to carbon dioxide and hydrogen using a water gas shift reaction.

8. Process (10) according to one of the preceding claims, characterized in that the second hydrogen stream (HG2) or a part thereof is fed to a material and / or thermal utilization.

9. Process (10) according to claim 8, characterized in that the material and / or thermal recycling takes place within the process.

10. Method (10) according to one of claims 1 to 9, characterized in that a drying unit is arranged upstream of the carbon dioxide separation unit (205).

11. Plant for the production of hydrogen and / or ammonia, comprising a device for providing a first synthesis gas stream (SG3) comprising hydrogen, carbon monoxide and carbon dioxide, a conversion device for providing a second synthesis gas stream (SG4) which is enriched in hydrogen and carbon dioxide and depleted in carbon monoxide compared to the first synthesis gas stream (SG3), Use of the first synthesis gas stream (SG3) or a portion thereof, a first pressure swing adsorption unit (204) for providing a first hydrogen stream (HG1) using hydrogen from the second synthesis gas stream (SG4), a carbon dioxide separation unit (205) for providing a carbon dioxide stream (CG1) using carbon dioxide from the second synthesis gas stream (SG4), and a separation device with which a first residual gas stream (RG2) remaining downstream of the provision of the first hydrogen stream (HG1) and the carbon dioxide stream (CG1) or a portion thereof can be separated to obtain a second hydrogen stream (HG2) and a second residual gas stream (RG3), characterized in that it comprises a return device via which the second residual gas stream (RG3) can be returned to a position directly upstream of the provision of the carbon dioxide stream (CG1). 12.Plant according to claim 11, which is set up to carry out a method (10) according to one of claims 1 to 10.

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