ELECTROLYSIS SYSTEM AND METHOD FOR OPERATING AN ELECTROLYSIS SYSTEM

Abstract

An electrolysis system for electrochemically breaking down water to form hydrogen and oxygen, having at least one electrolyser for electrochemically breaking down water to form hydrogen and oxygen. The electrolysis system also has a housing device for receiving the electrolyser, wherein the electrolyser is at least partially arranged in the housing device and the housing device is sealed relative to a first fluid surrounding the housing device. In the electrolyser, water is broken down to form hydrogen and oxygen. The hydrogen and the oxygen are directed out of the housing device.

Claims

1.-15. (canceled)

16. An electrolysis system for electrochemical decomposition of water to afford hydrogen and oxygen, comprising: at least one electrolyzer for electrochemical decomposition of water to afford hydrogen and oxygen, a housing apparatus for accommodating the electrolyzer, wherein the electrolyzer is entirely arranged in the housing apparatus and the housing apparatus is tightly sealed off from a first fluid surrounding the housing apparatus, wherein a first pressure inside the housing apparatus is higher than a second pressure outside the house apparatus, a heat exchanger arranged in the housing apparatus for thermal equalization of a temperature in the housing apparatus and outside the housing apparatus.

17. The electrolysis system as claimed in claim 16, further comprising: at least one oxygen sensor.

18. The electrolysis system as claimed in claim 16, further comprising: at least one hydrogen sensor.

19. The electrolysis system as claimed in claim 16, wherein the housing apparatus comprises a chemical molecular scavenger for reducing hydrogen, oxygen and/or water arranged in the housing apparatus.

20. The electrolysis system as claimed in claim 16, wherein the housing apparatus comprises an electrochemical hydrogen pump arranged in the housing apparatus.

21. The electrolysis system as claimed in claim 16, wherein the housing apparatus comprises a shell, wherein the shell has a fluid-tightly sealing through-flow apparatus arranged in the shell.

22. The electrolysis system as claimed in claim 16, wherein a periphery of the electrolyzer comprising conduits and heat exchangers is arranged in the housing apparatus.

23. A process for operating an electrolysis system for decomposition of water to afford hydrogen and oxygen, comprising: providing the electrolysis system comprising at least one electrolyzer for electrochemical decomposition of water to afford hydrogen and oxygen, comprising a housing apparatus for accommodating the electrolyzer, wherein the electrolyser is entirely arranged in the housing apparatus and the housing apparatus is tightly sealed off from a first fluid surrounding the housing apparatus, wherein a first pressure inside the housing apparatus is higher than a second pressure outside the house apparatus, decomposing water to afford hydrogen and oxygen in the electrolyser, discharging the hydrogen and the oxygen from the housing apparatus.

24. The process as claimed in claim 23, wherein the first fluid is a gas mixture.

25. The process as claimed in claim 24, wherein the housing apparatus is filled with a second fluid.

26. The process as claimed in claim 25, wherein the second fluid employed is a gas or a gas mixture.

27. The process as claimed in claim 26, wherein the second fluid comprises a low-oxygen or oxygen-free fluid.

28. The process as claimed in claim 25, wherein the second fluid has a different composition to the first fluid.

29. The process as claimed in claim 24, wherein the first fluid is air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a schematic diagram of an electrolysis system having an electrolyzer comprising an electrolytic cell and a housing apparatus,

[0030] FIG. 2 is a schematic diagram of an electrolysis system having an electrolyzer comprising an electrolytic cell, a periphery and a housing device.

DETAILED DESCRIPTION OF INVENTION

[0031] FIG. 1 shows an electrolysis system 1 having an electrolyzer comprising an electrolytic cell 2 and a housing apparatus 10. An electrolyser typically comprises several electrolytic cells 2. These electrolytic cells 2 are in particular arranged in stacks. For the sake of simplicity FIGS. 1 and 2 each show only one electrolytic cell 2. However, in principle the entire electrolyzer is arranged in the housing apparatus 10.

[0032] The housing apparatus 10 has the electrolytic cell 2 arranged in it. The electrolytic cell 2 comprises an anode space 4 and a cathode space 5. The anode space 4 has an anode 7 arranged in it. The cathode space 5 has a cathode 8 arranged in it. Water W flows from a water storage apparatus 30 into the anode space 4 and the cathode space 5. The water W is subjected to decomposition to afford H.sub.2 and oxygen O.sub.2 in the electrolytic cell 2. The hydrogen H.sub.2 exits the electrolytic cell 2 and the housing apparatus 10. It is passed into hydrogen storage apparatus. The oxygen O.sub.2 exits the anode space 4 and is passed into an oxygen storage apparatus 31 or is released to the environment outside the housing apparatus 10. The feedthroughs of the water-conducting, hydrogen-conducting and oxygen-conducting conduits through the housing apparatus 10 are fluid-tight. Outside the housing apparatus 10 is a first fluid F1. This fluid is especially air contaminated with salt or dust. Inside the housing apparatus 10 is a second fluid F2. The second fluid F2 especially comprises a gas mixture comprising very little, if any, oxygen. The second fluid is especially nitrogen.

[0033] The electrolytic cell 2 and the peripheral conduits are thus advantageously protected from external influences by the first fluid F1. In order to ensure heat exchange the housing apparatus 10 comprises a second heat exchanger 23. Valve 22 may be used to allow the first fluid F1 to flow into said exchanger to transport heat from the housing apparatus 10 into the environment.

[0034] Further valves may also be arranged in the housing apparatus 10. These may in particular be used to vent the second fluid F2 into the environment, i.e. into the first fluid F1, in the case of a hydrogen or oxygen leak. This is not shown in the figures.

[0035] FIG. 2 shows a second exemplary embodiment of an electrolysis system 1 comprising an electrolytic cell 2. In this second exemplary embodiment electrolysis is carried out at atmospheric pressure with natural circulation. This therefore advantageously requires just a few, if any, pumps. This setup comprises a periphery which especially comprises conduits and separation apparatuses.

[0036] Virtually all components (with the exception of the material storage apparatuses) are arranged in a housing apparatus 10 in this example. The housing apparatus 10 protects the components inside the housing apparatus 10 in particular from dust or salt from the environment. Outside the housing apparatus 10 is a first fluid F1. This comprises in particular dust or salt. Inside the housing apparatus 10 is a second fluid F2. This is especially a gas mixture containing very little, if any, oxygen. As already illustrated in the first exemplary embodiment the oxygen conduit, the hydrogen conduit and the water conduit are arranged such that they pass through the housing apparatus 10 in a fluid-tight manner. This means that the conduits are passed through an opening in the shell of the housing operators and is open is subsequently fluid-tightly sealed. In order to allow heat exchange with the environment the housing apparatus 10, in particular the shell of the housing apparatus 10, comprises a second heat exchanger 23. A valve may be used to pass the first fluid F1 from the environment through said heat exchanger so that the first fluid can absorb heat from the housing apparatus 10 and dissipate it to the environment.

[0037] The electrolytic cell 2 comprises a proton exchange membrane 3 which separates the anode space 4 from the cathode space 5. The anode space 4 comprises an anode 7. The cathode space 5 comprises a cathode 8. In the anode space 4, water W is oxidized to oxygen O.sub.2 at the anode 7. The oxygen-water mixture formed during the electrolysis in the anode space 4 has a lower density than pure water. It therefore ascends in the first conduit 9, also known as a riser tube, into a first gas separation apparatus 20. The first gas separation apparatus 20 is arranged above the anode space 4. In the first gas separation apparatus 20 the oxygen separates from the water. The oxygen O.sub.2 is especially passed into an oxygen storage means (now shown in the figure). The water W is passed via a second conduit 15 into a first heat exchanger 6. In the cathode space water is reduced to hydrogen H.sub.2 at the cathode 8 during the electrolysis. On account of the relatively low density relative to water the hydrogen-water mixture ascends especially in the context of a “forced circulation” via a third conduit 11 into a second gas separation apparatus 21. In the second gas separation apparatus 21 the hydrogen H.sub.2 separates from the water W. The hydrogen H.sub.2 exits the housing apparatus 10 and is advantageously passed into a hydrogen storage means. The water W may be passed into the first heat exchanger 6 via a fourth conduit 12. The water W is subsequently recycled from the first heat exchanger 6 into the anode space 4 and the cathode space 5. The first heat exchanger 6 is operated with a coolant, especially water. No mass transfer occurs between this coolant and the water from the electrolysis. The coolant inflow and outflow from the first heat exchanger 6 is not shown in FIG. 2 for the sake of simplicity.

[0038] The electrolysis system 1 can advantageously be operated dynamically, i.e. depending on the load the electrolysis unit may be operated with an energy density of more than 0 A/cm.sup.2 to 4 A/cm.sup.2, particularly advantageously of more than 1 A/cm.sup.2 to 3 A/cm.sup.2.

[0039] The first and the second gas separation apparatus 20, 21 are at a second height. The maximum height of the electrolytic cell is at a first height. The second height is above the first height. Thus the density differences resulting in the electrolyzer alone can ensure a natural circulation of the reactants and products in the electrolyzer. However, both heights must be above the first height of the electrolytic cell. Additional pumps or other conveying means are advantageously unnecessary. As an alternative to the embodiment shown here it is also possible to perform the natural circulation exclusively on the oxygen side, i.e. in the anode space 4. The principle of natural circulation which is based on the physical parameter of density results in automatic control of the water conveying rate. In a suitable process configuration an increased gas production rate thus increases the water conveying rate, with the result that the heat in turn is advantageously dissipated.

[0040] The operation of natural circulation at atmospheric pressure is particularly advantageous since at this pressure the gas bubble size of the hydrogen and/or oxygen and thus the resulting transportability in respect of the gases and the water is sufficiently large to allow pumps to be completely avoided.

[0041] The water circuits of the hydrogen and oxygen side, i.e. the water in the anode space 4 and in the cathode space 5, are connected to one another via the first heat exchanger 6.

[0042] It is clear from the reaction equation of water splitting that the decomposition of the water results in approximately twice the volume of hydrogen gas relative to oxygen gas. Thus at identical pipe diameter of the hydrogen side and the oxygen side the hydrogen side would exhibit a higher water conveying rate than the oxygen side, provided that the conveying rate is not limited by the pipe diameter. If the conveying rate of the water is limited by the riser tube, the conveying rate may be optimized by adapting the riser pipe diameter. In order thus to optimize the water flow on both sides the first diameter of the first conduit 9 is made smaller than the second diameter of the third conduit 11. It is particularly advantageous when the first conduit 9 has a cross sectional area of about half of the cross sectional area of the third conduit 11. A higher water conveying rate, in particular on the anode side, can advantageously be achieved compared to a conventional identical pipe diameter distribution.

LIST OF REFERENCE NUMERALS

[0043] 1 electrolysis system [0044] 2 electrolytic cell [0045] 3 proton exchange membrane [0046] 4 anode space [0047] 5 cathode space [0048] 6 first heat exchanger [0049] 7 anode [0050] 8 cathode [0051] 9 first conduit [0052] 10 housing apparatus [0053] 11 third conduit [0054] 12 fourth conduit [0055] 15 second conduit [0056] 20 first gas separation apparatus [0057] 21 second gas separation apparatus [0058] 22 valve [0059] 23 second heat exchanger [0060] 30 water storage apparatus [0061] 31 oxygen storage apparatus [0062] 32 hydrogen storage apparatus [0063] W water [0064] H.sub.2 hydrogen [0065] O.sub.2 oxygen [0066] F1 first fluid [0067] F2 second fluid