PROCESS AND PLANT FOR PRODUCING AND STORING HYDROGEN

Abstract

A process for producing and storing hydrogen includes providing an intermediate gas mixture having an increased proportion of hydrogen and contacting of the intermediate gas mixture with a hydrogen carrier medium in order to hydrogenate the hydrogen carrier medium.

Claims

1. A process for producing and storing hydrogen, the process comprising the process steps of: providing an intermediate gas mixture having an increased proportion of hydrogen; contacting the intermediate gas mixture with a hydrogen carrier medium in order to hydrogenate the hydrogen carrier medium.

2. A process as claimed in claim 1, further comprising: providing a raw material gas mixture comprising at least one hydrocarbon compound and pretreatment of the raw material gas mixture to produce the intermediate gas mixture having an increased proportion of hydrogen.

3. A process as claimed claim 2, wherein the pretreatment comprises at least one of desulfurization in order to defecate the raw material gas mixture of sulfur compounds and steam reforming.

4. A process as claimed in claim 2, wherein the pretreatment comprises at least one of a water gas shift reaction and a selective removal of carbon monoxide.

5. A process as claimed in claim 2, wherein the pretreatment comprises a selective removal of water.

6. A process as claimed in claim 1, further comprising: storing the hydrogenated hydrogen carrier medium.

7. A process as claimed in claim 1, further comprising: dehydrogenating the hydrogenated hydrogen carrier medium in order to release hydrogen.

8. A process as claimed in claim 1, further comprising: introducing dehydrogenated hydrogen carrier medium.

9. A process as claimed in claim 1, further comprising: discharging the hydrogenated hydrogen carrier medium.

10. A process as claimed in claim 1, further comprising: utilizing carbon dioxide as product of the hydrogenation of the hydrogen carrier medium.

11. A plant for producing and storing hydrogen, the plant comprising: a reaction apparatus for contacting an intermediate gas mixture having at least one of an increased proportion of hydrogen and a reduced proportion of carbon monoxide with a hydrogen carrier medium in order to hydrogenate the hydrogen carrier medium.

12. A plant as claimed in claim 11, further comprising: a pretreatment apparatus for pretreating a raw material gas mixture to give the intermediate gas mixture having at least one of the increased proportion of hydrogen and the reduced proportion of carbon monoxide.

13. A plant as claimed in claim 11, further comprising: a first storage unit for storing the hydrogenated hydrogen carrier medium.

14. A plant as claimed in claim 11, further comprising: a dehydrogenation unit for dehydrogenating the hydrogenated hydrogen carrier medium.

15. A plant as claimed in claim 11, further comprising at least one of: a first hydrogen carrier medium interface for discharging hydrogenated hydrogen carrier medium from the plant; and a second hydrogen carrier medium interface for introducing dehydrogenated hydrogen carrier medium into the plant.

16. A process as claimed in claim 3, wherein the steam reforming is a two-stage steam reforming.

17. A process as claimed in claim 3, wherein the pretreatment comprises steam reforming in the presence of a catalyst.

18. A process as claimed in claim 4, wherein the water gas shift reaction is a two-stage water gas shift reaction.

19. A process as claimed in claim 4, wherein the pretreatment comprises a water gas shift reaction in the presence of a catalyst.

20. A process as claimed in claim 4, wherein the pretreatment comprises a selective removal of carbon monoxide after a water gas shift reaction.

21. A process as claimed in claim 2, wherein the pretreatment comprises a selective removal of water after a water gas shift reaction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In the drawings:

[0034] FIG. 1 is a schematic view of a plant according to the invention for producing and storing hydrogen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Referring to the drawings, FIG. 1 shows a plant 1 for producing and storing hydrogen from natural gas. Natural gas is a raw material gas mixture which comprises one or more hydrocarbon compounds and in particular methane. The plant 1 is connected to a natural gas source 2 via a natural gas conduit 3. The plant 1 has a pretreatment apparatus 4 for pretreatment of the raw material gas mixture to give an intermediate gas mixture. The pretreatment apparatus 4 is connected via an intermediate gas mixture conduit 5 to a reaction apparatus 6.

[0036] The pretreatment apparatus 4 comprises a desulfurization unit 7 for freeing the raw material gas mixture of sulfur compounds. The desulfurization unit 7 is, in particular, connected directly to the natural gas conduit 3. The desulfurization unit 7 is connected via a conduit 8 to a steam reforming unit 9. The steam reforming unit 9 comprises a first steam reforming stage 10 and a second steam reforming stage 11 located downstream of the first steam reforming stage 10. The steam reforming unit 9 is connected to a water gas shift reaction unit 13 via a further conduit 12. The water gas shift reaction unit 13 comprises a first water gas shift reactor 14 and a second water gas shift reactor 15 located downstream of the first water gas shift reactor 14. The water gas shift reaction unit 13 is connected to a carbon monoxide removal unit 16 and a water removal unit 17. A connecting conduit system 18 provided for this purpose allows optional inclusion of the carbon monoxide removal unit 16 and the water removal unit 17 in the pretreatment apparatus 4. This means that the pretreatment apparatus 4 can be operated with the carbon monoxide removal unit 16 and/or with the water removal unit 17 or none of the two units. The connecting conduit system 18 is connected directly to the intermediate gas mixture conduit 5.

[0037] The reaction apparatus 6 is, in particular, configured as a trickle-bed reactor. The reaction apparatus 6 serves as hydrogenation unit for hydrogenating a hydrogen carrier medium by means of the hydrogen of the intermediate gas mixture. The reaction apparatus 6 contains a solid hydrogenation catalyst. LOHC serves as hydrogen carrier medium. The reaction apparatus 6 is connected via a hydrogen carrier medium conduit 19 to a first storage unit 20 for storing the hydrogenated hydrogen carrier medium. From the first storage unit 20, the hydrogenated hydrogen carrier medium can be fed to a dehydrogenation unit 21 for dehydrogenating the hydrogenated hydrogen carrier medium. Hydrogen is liberated in the dehydrogenation unit 21. The hydrogen liberated can be fed to a hydrogen utilization unit 22. As an alternative to the dehydrogenation unit 21, a first hydrogen carrier medium interface 23 can be provided. The first hydrogen carrier medium interface 23 can, for example, provide for transport of the hydrogenated hydrogen carrier medium using tankers or via a suitable pipeline. Correspondingly, it is possible to provide a second hydrogen carrier medium interface 24 which allows unloaded hydrogen carrier medium to be fed into the plant 1, in particular in the form of tankers or a pipeline provided for this purpose. In addition, it is possible to provide a second storage unit 25 in which the unhydrogenated hydrogen storage medium is stored, in particular before it is fed to the reaction apparatus in order to be hydrogenated.

[0038] The reaction apparatus 6 as hydrogenation unit, the first storage unit 20, the dehydrogenation unit 21 and the second storage unit 25 can form a circulatory system, in particular a closed circulatory system.

[0039] A unit 26 for direct use of the carbon dioxide-rich gas from the hydrogenation unit or an isolation unit for carbon dioxide is connected to the reaction apparatus 6.

[0040] A process for producing and storing hydrogen will be explained in more detail below. From a natural gas source 2, for example a stranded gas source, natural gas is fed via the natural gas conduit 3 of the pretreatment apparatus 4 to the plant 1, in particular to the desulfurization unit 7. In the desulfurization unit 7, the natural gas is freed of sulfur compounds. The purified natural gas is subjected to two-stage steam reforming. For this purpose, the natural gas which has been freed of sulfur compounds is fed via the conduit 8 to a first steam reforming stage 10 of the steam reforming unit 9. Steam reforming occurs there at a first temperature. A gas mixture which can be produced in the first steam reforming stage 10 is fed to the second steam reforming stage 11. By addition of air and partial combustion of the gas mixture which has been partially formed in the first steam reforming stage 10, an increased process temperature of, for example, from 600° C. to 1000° C. can be achieved in the second steam reforming stage. Steam reforming is carried out in the presence of a nickel-containing catalyst. Steam reforming is carried out at a pressure of, in particular, from 20 bar to 40 bar. Later compression of the hydrogen is thus dispensable.

[0041] The steam-reformed gas mixture is fed to the water gas shift reaction unit 13 via the conduit 12. In the first water gas shift reactor 14, carbon monoxide in the gas mixture is reacted with water to form carbon dioxide and hydrogen. The process temperature in the first water gas shift reactor 14 is from 300° C. to 500° C. A solid iron/chromium catalyst is used for this purpose. In the second water gas shift reactor 15, a particularly effective, virtually complete, conversion of carbon monoxide is carried out at reduced temperatures, in particular in the range from 180° C. to 300° C., by means of a solid copper/zinc oxide catalyst. The water gas shift reactors 14, 15 are, in particular, configured as adiabatically operable fixed-bed reactors.

[0042] After the water gas shift reaction, the gas mixture can, within the framework of the pretreatment, be subjected to a selective removal of carbon monoxide in the carbon monoxide removal unit 16 and/or a selective removal of water in the water removal unit 17.

[0043] Overall, an intermediate gas mixture which has an increased proportion of hydrogen compared to the natural gas as raw material gas mixture is provided by the pretreatment in the pretreatment apparatus 4. A proportion of carbon monoxide formed during steam reforming is made so low by the process steps of the pretreatment apparatus 4 that it is unproblematical for a subsequent hydrogenation.

[0044] The intermediate gas mixture is fed to the reaction apparatus 6 and contacted there with the LOHC. The hydrogen is chemically bound directly to the hydrogen carrier medium, i.e. to the LOHC. The hydrogenated LOHC is conveyed via the conduit 19 to the first storage unit 20 and from there fed via the first hydrogen carrier medium interface 23 into a pipeline grid provided for this purpose or into a tanker provided for this purpose and transferred to a remote location for utilization after liberation of hydrogen.

[0045] The plant 1 can be supplied with unhydrogenated LOHC via a second storage unit 25. The second storage unit 25 can, for example, be supplied from the outside via a second hydrogen carrier medium interface 24. It is also possible for the dehydrogenation unit 21 to be connected directly to the second storage unit 25.

[0046] After the liberation of hydrogen in the dehydrogenation unit 21, dehydrogenated LOHC can be conveyed to further use in the circulatory system of the second storage unit 25.

[0047] As a result of the hydrogenation of the LOHC in the reaction apparatus 6, carbon dioxide is obtained in enriched form. The carbon dioxide has been largely freed of hydrogen. The carbon dioxide-rich gas obtained in the hydrogenation in the reaction apparatus 6 is industrially usable. The isolation unit 26 for the carbon dioxide can be connected to further components for handling and/or direct utilization of the carbon dioxide.

[0048] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.