ENERGY AND HYDROGEN LOGISTICS

Abstract

A method for transporting liquid methane includes generating electricity in plants; using the electricity to split water into hydrogen and oxygen; providing carbon dioxide; feeding the hydrogen and the carbon dioxide from step into a reactor system for producing methane, wherein this reactor system comprises a catalytic reactor cooled with boiling water; liquefying the methane so produced; transporting the liquefied methane to a place of consumption located far away; utilising the liquefied methane at the place of consumption subject to generating carbon dioxide;) separating this carbon dioxide. At the place of consumption the methane is subjected to a steam reformation for producing hydrogen, wherein carbon dioxide is generated. At least a part of the carbon dioxide generated during the steam reformation is transported back to the reactor system for producing methane.

Claims

1. A method for transporting hydrogen as liquid methane, comprising: a) generating electricity; b) using the electricity generated in order to split water into hydrogen and oxygen; c) providing carbon dioxide, ; d) feeding the hydrogen from b) and the carbon dioxide from c) into a reactor system configured to produce methane, wherein the reactor system comprises a catalytic reactor cooled with boiling water; e) liquefying the methane; f) transporting the liquefied methane to a place of consumption located a distance away; g) utilising the liquefied methane at the place of consumption subject to generating carbon dioxide, wherein the methane is subjected to a steam reformation to produce gaseous hydrogen, wherein carbon dioxide is generated; and h) separating the carbon dioxide; wherein c) includes: a return transport of carbon dioxide from h); and c1) at least a part of the carbon dioxide generated during the steam reformation is transported back to the reactor system for producing methane.

2. The method according to claim 1, wherein h) includes the following: liquefying reaction gas generated through the steam reformation by cooling and during the cooling, the carbon dioxide, which is liquefied, is separated from the gaseous hydrogen; and wherein in c1) the separated carbon dioxide is transported back into the reactor system according to d) by a CO.sub.2 transport.

3. The method according to claim 1, wherein through d) to f), g1), h) and c1) a largely closed CO.sub.2 cycle is formed.

4. The method according to claim 1, wherein in c) methanization is operated with an excess of hydrogen with respect to conversion of the carbon dioxide of under 10% by volume, with at least 0.3% by volume.

5. The method according to claim 4, wherein the excess of hydrogen amounts to more than 1.0% by volume.

6. The method according to claim 5, wherein the excess of hydrogen amounts to more than 1.5% by volume.

7. The method according to claim 1, wherein in e) excess hydrogen is separated from the liquid methane in a gas phase, and in d) the excess hydrogen is returned to the reactor system.

8. The method according to claim 1, wherein in b) the electricity generated in a) is used for operating an electrolysis plant.

9. The method according to claim 1, wherein c) includes: collecting of carbon dioxide from an emission source.

10. The method according to claim 9, wherein the emission source is a power plant operated with methane, a biomass energy plant, or an industrial plant emitting carbon dioxide.

11. The method according to claim 1, wherein the electricity is generated in a plant that utilises renewable energies.

12. The method according to claim 11, wherein the renewable energies comprise wind, solar, biomass, or geo-thermal.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0025] The invention is additionally explained in more detail exemplarily by way of the only FIGURE:

[0026] The FIGURE shows an exemplarily method for transporting hydrogen in the form of liquid methane.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0027] The starting point of the method is formed by the generation of electric energy by way of renewable energy sources, for example from wind energy 1 or from solar energy 2. This electric energy is utilised—for example in an electrolyser 3—for splitting water 4 into hydrogen 5 and oxygen 6. In the simplest case, the oxygen 6 is released into the atmosphere. However, it can also be advantageously utilised in industrial processes or for supporting the biological wastewater purification in treatment plants. The generated hydrogen 5 is merged in a mixer 7 with a CO.sub.2 flow 8 to form a reaction gas 9. Here, the mixing ratio is preferentially adjusted so that it contains hydrogen at a super-stoichiometric ratio. In a methanization reactor 10, the reaction gas 9 is converted into methane 11.

[0028] The converted reaction gas is cooled in a cooler 12 and liquefied. Condensable reaction products such as water are separated in a separator 13 and non-converted reaction gas components are again returned via a return line 14, preferably via the mixer 7, to the inlet into the methanization reactor 10. The methane 15 thus liquefied, also referred to as LNG (liquid natural gas) is fed into a specially equipped transport, in the case of a sea transport into a specially equipped tanker 16, and transported with the same to a place of consumption geographically further distant.

[0029] On arrival there, it is buffer-stored if applicable in tanks. In an evaporator 17, it is again transformed into gaseous methane 18. The methane 18 is converted in a steam reformer (SR) 19 with steam 20 to form synthetic gas 21 consisting of carbon dioxide and hydrogen. In a preferred embodiment, the reaction gas, by supplying further steam (WGS, water-gas shift) 21 the reaction gas is finally converted to form a product gas 22. In a separator 23, the same is, cooled, separated into its main constituent hydrogen (H.sub.2, gaseous) 24 and carbon dioxide (CO.sub.2, liquid) 25. Non-converted methane 26 is again returned into the steam reformer 19. The generated hydrogen 24 is fed to a hydrogen user (C1) 27. Another utilisation path of the gaseous methane 18 flowing out of the evaporator 17 is the conventional direct utilisation by a consumer (C2) 28. This can be for example a gas power plant, an industrial operation or a heating plant. Generally, this utilisation consists of combustion processes subject to forming CO.sub.2, 29. Preferably, the latter is separated from the exhaust gas and in the same manner as the CO.sub.2 25 generated in the preferred embodiment supplied to a cleaning stage 30. The CO.sub.2 31 cleaned in this manner is liquefied in a cooler 32 and in a transport 33 that is identical or similar to the transport 16 returned to the mixer 7 of the methanization plant. It is likewise possible that the transport means 16 is used as transport means 33 for the CO.sub.2.

[0030] The CO.sub.2 31 from the consumption processes is largely reclaimed and conducted in the cycle. The term “largely” is to mean that as much as possible CO.sub.2 is reclaimed. However, as with any eclamation process there are losses that cannot be entirely avoided for technical and economic reasons. The losses created have to be offset through other CO.sub.2 sources. The CO2 supplementation flow 34 originating from there is fed back to the mixer 7 together with the CO.sub.2 flow 8.

[0031] The conveying devices required for the various part processes are known to the person skilled in the art. There is therefore no detailed representation here. Further, modifications of individual method steps such as for example the switching of cleaning and cooling stages are within the scope of the invention. The plant-internal heat utilisation of heat generating and heat utilising processes is likewise known to the person skilled in the art and is not discussed further here.

[0032] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.