Method and installation for the electrolytic production of liquid hydrogen

Abstract

The invention relates to a method (100) for the electrolytic production of a liquid hydrogen product (4), in which a water-containing feed is subjected to an electrolysis (E) while receiving an anode raw gas (3), rich in oxygen and containing hydrogen, and a cathode raw gas (2) which is depleted of oxygen and rich in hydrogen, wherein the cathode raw gas (2) downstream of the electrolysis (E) is subjected to a purification (R), a compression (K), and a liquefaction (L), characterized in that the cathode raw gas (2) at least partially undergoes intermediate storage (Z) downstream of the electrolysis (E) and upstream of the liquefaction (L). A corresponding installation is also proposed.

Claims

1. A method (100) for the electrolytic production of a liquid hydrogen product (4), comprising: subjecting a water-containing feed to electrolysis (E) while receiving an anode raw gas (3), rich in oxygen and containing hydrogen, and a cathode raw gas (2) which is depleted of oxygen and rich in hydrogen, wherein the electrolysis (E) is carried out, in parallel, at two different pressure levels, a higher pressure level and a lower pressure level, to produce a first cathode raw gas produced by the electrolysis at the higher pressure level and a second cathode raw gas produced by the electrolysis at the lower pressure level, wherein, downstream of the electrolysis (E), the first cathode raw gas and the second cathode raw gas are each subjected to purification (R), compression (K), and a liquefaction (L), wherein, downstream of the electrolysis (E) and upstream of liquefaction (L), the first cathode raw gas produced by the electrolysis at the higher pressure level is subjected at least partially to intermediate storage (Z), and the second cathode raw gas produced by the electrolysis at the lower pressure level is not subjected to intermediate storage (Z).

2. The method (100) according to claim 1, wherein the intermediate storage (Z) takes place at a temperature level in a range of 250 to 330 K and a pressure level in a range of 1 to 20 MPa, or at a temperature level in a range of 50 to 100 K and a pressure level of 1 to 20 MPa.

3. The method (100) according to claim 1, wherein intermediate storage (Z) is carried out upstream and/or downstream of the purification (R).

4. The method (100) according to claim 1, wherein the first cathode raw gas is subjected to compression upstream of the intermediate storage (Z).

5. The method (100) according to claim 1, wherein the purification (R) comprises at least one of catalytic conversion of oxygen to water, adsorption, a distillative separation, and a-scrubbing with an absorption fluid.

6. The method (100) according to claim 1, wherein the electrolysis (E) is operated as a function of an external energy supply, wherein at a high external energy supply, a high electrolysis output is set, and, wherein at a low supply external energy, a low electrolysis output is set.

7. The method (100) according to claim 6, wherein the electrolysis (E) has a maximum output and the electrolysis output is adapted to the external energy supply at a rate of change more than 1%/min in relation to the maximum output of the electrolysis.

8. The method (100) according to claim 1, wherein the intermediate storage (Z) takes place at a temperature level in a range of 273 to 313 K and a pressure level in a range of 1 to 20 MPa, or at a temperature level in a range 75 to 100 K, and a pressure level of 1 to 20 MPa.

9. The method (100) according to claim 1, wherein the intermediate storage (Z) takes place at a temperature level in a range of 273 to 313 K and a pressure level in a range of 1 to 20 MPa, or at a temperature level in a range 75 to 100 K, and a pressure level of 3 to 10 MPa.

10. The method (100) according to claim 1, wherein the intermediate storage (Z) takes place at a temperature level in a range of 250 to 330 K and a pressure level in a range of 1 to 20 MPa.

11. The method (100) according to claim 1, wherein the intermediate storage (Z) takes place at a temperature level in a range of 50 to 100 K and a pressure level of 1 to 20 MPa.

12. The method (100) according to claim 1, wherein intermediate storage (Z) is carried out upstream of the purification (R).

13. The method (100) according to claim 1, wherein intermediate storage (Z) is carried out downstream of the purification (R).

14. The method (100) according to claim 6, wherein the electrolysis (E) has a maximum output and the electrolysis output is adapted to the external energy supply at a rate of change of more than 0.1%/s, in relation to the maximum output of the electrolysis.

15. The method (100) according to claim 6, wherein the electrolysis (E) has a maximum output and the electrolysis output is adapted to the external energy supply at a rate of change of more than 1%/s, in relation to the maximum output of the electrolysis.

16. The method (100) according to claim 6, wherein a liquefaction output is adapted more slowly to the external energy supply than is the electrolysis output.

17. The method (100) according to claim 16, wherein the liquefaction has a maximum output and the liquefaction output is at a rate of less than 5%/min, in relation to the maximum output of the liquefaction.

18. The method (100) according to claim 16, wherein the liquefaction has a maximum output and the liquefaction output is at a rate of less than 2%/min, in relation to the maximum output of the liquefaction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention or advantageous developments thereof are explained in more detail below with reference to the attached drawing, wherein

(2) FIG. 1 is a simplified view of an advantageous development of concepts according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) As already explained at the outset, the invention relates both to a method and to an installation for the electrochemical production of a liquid hydrogen product. The schematic representation in FIG. 1 can be interpreted both as an installation and as a flowchart of a method. If, therefore, an installation component is described below, the statements will also apply analogously to a method step carried out in this installation component, and vice versa. For this reason, the reference signs are also used below to designate method steps which are carried out in corresponding installation parts, and vice versa.

(4) An advantageous development of the invention is shown schematically In FIG. 1 and denoted as a whole by 100.

(5) An installation 100 comprises an electrolysis unit E, a cooling and/or compression unit K, a purification unit R, an intermediate storage Z, and a liquefaction unit L.

(6) Such an installation 100 can also be integrated into one or more containers, such as are usually used for transportation purposes by land and sea, which can thus be transported and set up very quickly and cost-effectively.

(7) Accordingly, the method comprises an electrolysis step E, a cooling and/or compression step K, a purification step R, an intermediate storage Z, and a liquefaction step L.

(8) In the electrolysis E, a water-containing feed 1 is converted, using electrical energy, into a hydrogen-containing cathode raw gas 2 and an oxygen-containing anode raw gas 3. In addition to water, the feed 1 can contain additional componentsin particular, electrolytes such as, for example, alkaline, acidic, or neutral salts or ions. The feed 1 can, in particular, be fed into the electrolysis unit E on the anode side.

(9) The cathode raw gas 2 is taken from the electrolysis unit E and is fed into a post-processing stage, which, in a suitable sequence, comprises compression, purification, intermediate storage, and liquefaction. The liquefaction in each case forms the conclusion of the post-processing, and the remaining steps can be varied in their sequence.

(10) The cooling or compression K of the cathode raw gas 2 can be carried out using a conventional mechanical chiller, or, particularly advantageously, using waste heat from the electrolysis E by means of an absorption chiller or adsorption chiller, which has a particularly advantageous effect on the total energy balance of the installation 100. Even conventional mechanical chillers can utilize waste heat from the electrolysis E, wherein these can initially be used for carrying out volume work, e.g., by steam generation in combination with a turbine for compressing the cathode raw gas 2.

(11) Various methods are available for purification Rfor example, (in particular, cryogenic) adsorption, oxidative combustion of oxygen, condensation of components with comparatively high boiling points, and so on.

(12) Purification requirements can be significantly reduced if the feed 1 has already been stripped of impurities upstream of the electrolysis E, or depleted thereof. Particularly relevant in this context are gases, e.g., nitrogen, carbon dioxide, and/or noble gases, dissolved in the water of the feed 1. These can, for example, be expelled or otherwise removed from the feed 1 by so-called stripping, using the anode raw gas 3 produced in the electrolysis, or by other degassing strategies such as, for example, membrane degassing.

(13) As noted above, intermediate storage Z can be implemented upstream and/or downstream of purification. The intermediate storage Z can be implemented, for example, at a constant volume using a pressure tank, wherein the pressure tank can be operated at a pressure level which corresponds to a cathode-side, electrolysis pressure level or is filled by means of a compressor with cathode raw gas 2, which can lie at a pressure level above the cathode-side pressure level. Units arranged downstream of the storage tank can in particular be designed such that they can be operated with variable input pressures, or a pressure regulator can be provided downstream of the intermediate storage Z, which ensures a constant pressure.

(14) Within the scope of the invention, it is also possible to use storage tanks with a constant pressure as the intermediate storage Z. Such storage tanks have, for example, a variable volume (for example, in the form of a plunger or piston in a hollow cylinder or the like), or they can regulate the pressure by appropriate control of the storage temperature.

(15) In addition, metal hydride storage tanks can be used in which a metal, e.g., an alloy containing palladium, is capable of absorbing hydrogen to form a metal hydride. If such a metal hydride storage tank is used, the release or delivery of hydrogen stored in the intermediate storage Z can, in turn, take place using waste heat from the electrolysis E, with corresponding energy advantages.

(16) To further increase the dynamicsparticularly in the region of the post-processing downstream of the electrolysis Ethe respective components can also be operated in parallel to one another in a multiple embodiment, so that a larger controllable range is available. For example, several compressors and/or turbines can be provided for compression, so that the liquefaction output can be reduced to, for example, below 30% of nominal output, by completely switching off at least one component that is present several times.

(17) As mentioned at the outset, it is advantageous to control the output of the installation 100 as a function of an external energy supply. For example, such an installation 100 can be operated with renewable electrical energyfor example, from a wind farm or a wind park. In the event of a calm, there will accordingly be little or no output available, so that electrolysis may be massively reduced in such a case. In the event that no electrical energy is available, a portion of the generated hydrogen, e.g., from the intermediate storage Z, can be used for generating electrical energy in order to continue to operate the electrolysis E at a minimum output levelfor example, 10% of nominal output. Use of hydrogen which evaporates in a liquid tank downstream of the liquefaction L can also be suitable for such use. As a result, it is possible to ensure a more rapid restart or increase in electrolysis output with an increasing external energy supply, i.e., for example, with a stronger wind. In comparison to this, it takes considerably longer to run up an electrolysis unit E that has been taken out of operationin particular, since the electrolysis unit E must be brought up to an operating temperature. In this case, such an installation 100 can in principle be integrated directly into a wind power installation (e.g., an offshore wind farm)for example, in order to minimize power transmission losses. Liquid hydrogen and/or cold gases generated by the wind turbine can here be used in part also for cooling the wind turbine (for example, the generator), e.g., in order to minimize the power transmission losses by using superconducting materials.

(18) To further increase the energy efficiency, a conventional heat exchanger can be used, in which the use of anode raw gas 3 and/or cathode raw gas 2 removed from electrolysis E is heated.

(19) The anode raw gas 3 can likewise be fed into a processing facility, so that, here too, the steps of purification, drying, compression, liquefaction, and/or storage can be provided. Alternatively, the anode raw gas can be discharged to the surrounding atmosphere, since it does not in principle contain any harmful components, and is therefore harmless in terms of health and environment.