METHOD FOR OPERATING AN ELECTROLYSIS SYSTEM, AND ELECTROLYSIS SYSTEM

Abstract

A method for operating an electrolysis system which includes an electrolyzer for generating hydrogen and oxygen as product gases, the product gas streams being discharged from the electrolyzer. A secondary gas is mixed with at least one of the product gas streams with the goal of reducing the foreign gas concentration in the product gas stream to be treated by an increase of the overall volume flow.

Claims

1. A method for operating an electrolysis system comprising an electrolyzer for generating hydrogen and oxygen as product gases, the method comprising: discharging the product gas streams from the electrolyzer, and mixing a secondary gas with at least one of the product gas streams.

2. The method as claimed in claim 1, wherein the secondary gas comprises the same product gas as in the product gas stream with which it is mixed and/or comprises an inert gas.

3. The method as claimed in claim 1, wherein the secondary gas is a gas which is generated in the electrolysis system and is purified and recycled.

4. The method as claimed in claim 3, wherein at least part of the product gas stream is purified after a gas separation device and used as secondary gas.

5. The method as claimed in claim 4, wherein the secondary gas is recycled into the gas separation device under pressure.

6. The method as claimed in claim 1, wherein a foreign gas concentration in the product gas stream which is mixed with the secondary gas is determined and a volumetric flow rate of the secondary gas is adjusted depending on the foreign gas concentration.

7. The method as claimed in claim 1, wherein at least part of a product gas is branched off and temporarily stored in a gas store, wherein the stored product gas is recycled as secondary gas when the electrolysis system is started up.

8. An electrolysis system comprising: an electrolyzer for generating hydrogen and oxygen as product gases, a first product gas line and a second product gas line for discharging the product gases from the electrolyzer, and a secondary gas line, by which a secondary gas is mixed with at least one of the product gas streams in one of the product gas lines.

9. The electrolysis system as claimed in claim 8, wherein the secondary gas line opens into a gas separation device downstream of the electrolyzer.

10. The electrolysis system as claimed in claim 9, wherein the secondary gas line is branched off from the at least one product gas line after the gas separation device.

11. The electrolysis system as claimed in claim 8, wherein a recombiner is arranged on the at least one product gas line.

12. The electrolysis system as claimed in claim 8, wherein the secondary gas line comprises a fan.

13. The electrolysis system as claimed in claim 8, further comprising: a measuring device for measuring a foreign gas concentration in the product gas stream which is mixed with the secondary gas, and a control device suitable for adjusting a volumetric flow rate of the secondary gas depending on the foreign gas concentration.

14. The electrolysis system as claimed in claim 8, wherein the secondary gas line is fluidically connected to a gas store for the secondary gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One exemplary embodiment of the invention is explained in more detail with reference to the drawing.

DETAILED DESCRIPTION OF INVENTION

[0021] Herein, the single FIGURE illustrates an electrolysis system 1 comprising an electrolyzer 2. The electrolysis system 1 also has a first gas separation device 4 on the oxygen side and a second gas separation device 6 on the hydrogen side. The electrolyzer 2 is connected to the first gas separation device 4 via a first product gas line 8 and to the second gas separation device 6 via a second product gas line 10. Accordingly, a mixture of water and oxygen is transported via the first product gas line 8. A mixture of water and hydrogen is conducted out of the electrolyzer 2 through the second product gas line 10. A liquid/gas separation subsequently takes place in the respective gas separation device 4, 6.

[0022] Furthermore, water from the first gas separation device 4 is recycled into the electrolyzer 2 via a water return line 12.

[0023] The water from the second gas separation device 6 is conducted into a water supply line 14 of the electrolyzer 2.

[0024] In practice, the oxygen gas stream in the first product gas line 8 comprises small amounts of hydrogen and the hydrogen gas stream in the second product gas line 8 comprises small amounts of oxygen. In order to remove these foreign gases, i.e. to purify the product gases oxygen 16 and hydrogen 18, a recombiner 20, 22 is connected downstream of the respective gas separation device 4, 6, in which recombiner the gaseous hydrogen is catalytically oxidized with the gaseous oxygen to form water.

[0025] Part of the respective product gas 16, 18 processed in this way is recycled into the respective gas separation device 4, 6 via a secondary gas line 24. Integrated in the secondary gas line 24 here is a fan 26 which increases the pressure of the purified product gas, oxygen or hydrogen, before the gas separation device 4, 6. Due to the branched-off, pure product gas, the foreign gas concentration in the product gas stream in the product gas lines 8, 12 that is to be treated is reduced by the increase in the overall volumetric flow rate.

[0026] It is further possible to ensure particularly flexible operation by determining the foreign gas concentration in the respective product gas stream and varying the volumetric flow rate of the secondary gas depending on this foreign gas concentration. For this purpose, measuring devices, which however are not illustrated in the FIGURE, are attached to the product gas lines 8, 12.

[0027] A further option is to temporarily store the purified product gas, which is provided as secondary gas, in a gas store and to recycle it into the gas separator when the electrolysis system is started up. The gas store, not illustrated in greater detail, is in particular fluidically connected to the respective secondary gas line 24.

[0028] As an alternative to supplying the secondary gas into the gas separation device, said secondary gas may be conducted into the outlet region from the electrolyzer 2 and/or into the inlet region of the electrolyzer 2. As a further alternative, it is also conceivable to supply an inert gas, such as nitrogen, as secondary gas instead of a purified product gas at least on the oxygen side.

[0029] In the exemplary embodiment illustrated, the product gas stream is mixed with a secondary gas both on the oxygen side and on the hydrogen side. However, it is possible to supply the secondary gas to only one product side, for example only to the oxygen side.