METHOD FOR OPERATING A WATER ELECTROLYSIS DEVICE

Abstract

The method for operating a water electrolysis device for generating hydrogen and oxygen from water has a PEM electrolyser (1), to which water for generating the hydrogen and the oxygen is supplied together with water for cooling. The cooling water is conducted in the circuit and treated by means of an ion exchanger unit (17). Only part of the water conducted in the circuit is supplied to the ion exchanger unit (17) and another part is supplied to the PEM electrolyser (1) via a bypass (13) circumventing the ion exchanger unit (17).

Claims

1. A method for operating a water electrolysis device for generating hydrogen and oxygen from water, the method comprising the steps of: supplying water for generating the hydrogen and the oxygen together with water for cooling to a PEM electrolyser, and the water for cooling is carried in a circuit and treated by means of a cleaning and/or separating device, wherein only part of the water carried in the circuit is supplied to the cleaning and/or separating device as a partial flow and a different part, as another partial flow is supplied to the PEM electrolyser via a bypass, which bypasses the cleaning and/or separating device.

2. The method according to claim 1, wherein at least one ion exchanger is used as the cleaning and/or separating device.

3. The method according to claim 1, wherein a ratio of the partial flows of the cooling circuit, which flow through the cleaning and/or separating device and the bypass, is set up such that a water quantity is guided through the cleaning and/or separating device every hour and treated, which is at least four times a water quantity carried in the cooling circuit.

4. The method according to claim 1, wherein during the start-up of the water electrolysis device, the water carried in the circuit is guided completely through the cleaning and/or separating device until the water has achieved at least one predetermined quality value and only subsequently is the bypass of the circuit enabled for bypassing the cleaning and/or separating device.

5. A water electrolysis device for generating hydrogen and oxygen from water, the water electrolysis device comprising: a PEM electrolyser, which is incorporated into a cooling water circuit, via which the reaction water is also supplied; a cleaning and/or separating device, which is connected in the cooling water circuit upstream of the electrolyser; and a bypass provided in the circuit, via which water can be supplied to the electrolyser, bypassing the cleaning and/or separating device.

6. The water electrolysis device according to claim 5, wherein the cleaning and/or separating device comprises one ion exchanger or a plurality of ion exchangers connected in series.

7. The water electrolysis device according to claim 5, wherein that the cleaning and/or separating device comprises at least one filter.

8. The water electrolysis device according to claim 5, further comprising a cooling device or a heat exchanger of a cooling device connected upstream of the cleaning and/or separating device for cooling down incoming water.

9. The water electrolysis device according to claim 5, further comprising a heating device or a heat exchanger of a heating device connected downstream of the cleaning and/or separating device to heat the exiting water.

10. The water electrolysis device according to claim 5, further comprising pressure-increasing means, provided in the circuit and arranged in a flow path, in both flow paths and/or in the common flow path.

11. The water electrolysis device according to claim 5, wherein at least one valve is provided in the bypass, wherein the at least one valve is configured to completely or partially shut off the bypass.

12. The water electrolysis device according to claim 10, further comprising a control system configured to control the pressure-increasing means.

13. The water electrolysis device according to claim 5, wherein the cleaning and/or separating device comprises a plurality of parallel-connected ion exchanger units, which each have two ion exchangers connected in series.

14. The water electrolysis device according to claim 13, wherein the number of the parallel-connected ion exchanger units is chosen such that at maximum load, without functional impairment, one ion exchanger unit can be switched off for maintenance.

15. The water electrolysis device according to claim 8, further comprising a heating device or a heat exchanger of a heating device connected downstream of the cleaning and/or separating device to heat the exiting water, wherein the heat exchangers of the cooling and/or heating devices are assigned to a common temperature control circuit.

16. The water electrolysis device according to claim 8, further comprising a control system configured to control the cooling device.

17. The water electrolysis device according to claim 9, further comprising a control system configured to control the heating device.

18. The water electrolysis device according to claim 11, further comprising a control system configured to control the valve.

19. The water electrolysis device according to claim 8, further comprising: a heating device or a heat exchanger of a heating device connected downstream of the cleaning and/or separating device to heat the exiting water; a pressure-increasing means provided in the circuit and arranged in a flow path, in both flow paths and/or in the common flow path; at least one valve in the bypass, wherein the at least one valve is configured to completely or partially shut off the bypass; and a control system configured to control the pressure-increasing means, the valve and/or the heating and/or cooling devices in a coordinated manner.

20. A method for operating a water electrolysis device for generating hydrogen and oxygen from water, the method comprising the steps of: providing the water electrolysis device for generating hydrogen and oxygen from water, wherein the water electrolysis device comprises: a PEM electrolyser incorporated into a cooling water circuit, via which the reaction water is also supplied; a cleaning and/or separating device connected in the cooling water circuit upstream of the electrolyser; and a bypass connected in the circuit, via which water may be supplied to the electrolyser, bypassing the cleaning and/or separating device; supplying water for cooling to a PEM electrolyser, wherein at least a partial flow of the water for cooling is carried in the circuit and treated by the cleaning and/or separating device and another partial flow is carrier to the PEM electrolyser via the bypass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the drawings:

[0027] FIG. 1 is circuit diagram of a water electrolysis device according to the invention in a simplified illustration;

[0028] FIG. 2 is an alternative embodiment of the integration of a cleaning and/or separating device, and;

[0029] FIG. 3 is a further configuration of the integration of a cleaning and/or separating device.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Referring to the drawings, the water electrolysis device according to FIG. 1 has an electrolyser 1 of Polymer Electrolyte Membrane configuration, which is formed as a stack, that is to say as a stack of a multiplicity of individual cells, which adjoin one another, and in which water is supplied via an inlet 2, specifically on the one hand as a reactant and on the other hand as a cooling fluid. Part of this supplied water is electrolytically broken down to hydrogen and oxygen using electric current. The hydrogen is removed via an output 3 of the electrolyser, the oxygen reaches a container 6 via an output 4 together with the excess water via a line 5.

[0031] The container 6 forms a gas separator and at the upper side thereof, the oxygen collected there is removed via a line 7. Demineralized water is supplied via an inlet 8, in order to replace the water converted into hydrogen and oxygen by the electrolytic breakdown in the electrolyser 1. The container 6 has an output 9, which is connected via a line 10 first to a circulation pump 11 for the cooling water circuit and then to a heat exchanger 12 of a cooling set. At the end of the line 10, the line divides into a line 13 forming a bypass, labelled with 13 in the figures, and a line 14 parallel thereto, in which a water treatment device in the form of two ion exchangers 15 and 16 connected one behind the other is incorporated. In the line 14, a circulation pump 18 and downstream a heat exchanger 19 of a cooling set are arranged upstream of the ion exchanger unit 17 formed by the ion exchangers 15 and 16. A shut-off valve 20 is arranged in the line 13 forming the bypass, which is electromotively controlled. The line 13 forming the bypass and the line 14, which contains the water treatment device 17, are merged at the output side and open at the inlet 2 of the electrolyser 1.

[0032] During operation of the device when started up, water is fed to the electrolyser 1 via the inlet 2. This water is broken down electrolytically into hydrogen and oxygen using electrical energy, the hydrogen is removed via the output 3, the oxygen leaves the output 4 of the electrolyser 1 together with the excess water. The water-oxygen mixture reaches the container 6 via the line 5, in which container the oxygen is removed via the line 7 and the water is removed via the line 10 connected at the output 9, if appropriate with the supply of further demineralized water via the inlet 8.

[0033] This heated water is, where necessary, cooled down by means of a heat exchanger 12, to a temperature which corresponds approximately to the desired operating temperature of the electrolyser 1, that is to say for example approximately 70° C. This water then reaches the lines 13 and 14, wherein the quantitative proportion of the lines 13 and 14 is controlled by means of the valve 20 or controlled to predetermined desired values. Alternatively or additionally, this can take place by actuating the variable speed circulation pump 18, which increases the pressure level inside the line 14, in order to be able to overcome the hydraulic resistance increased by the heat exchanger 19 and the downstream-connected ion exchanger unit 17.

[0034] The water carried in the line 14 is cooled by means of the heat exchanger 19 to a temperature of 60° C., this is the maximum permitted temperature for the operation of the ion exchanger unit 17. The water exiting the ion exchanger unit 17 then makes it back into the inlet 2 of the electrolyser together with the water coming from the line 13. The ratio of the partial flows of the lines 13 and 14 is chosen in such a manner that the partial flow through the line 13 is as large as possible and the partial flow through the line 14 is as large as necessary, so that the cleaning and/or separating treatment of this water is sufficient in order not to damage the electrolyser 1 during operation. As the water quantity required for cooling the electrolyser 1 and to be circulated is substantially larger than the water quantity to be cleaned, during operation when run in, a flow rate which is typically ten to thirty times as high as that in the line 14 results in the line 13.

[0035] If the previously described water electrolysis device has to be started up after maintenance works or after an interruption to operation, the proportion of the metal ions located in the water is typically excessive, which is why during the start-up of the device, first the valve 20 is actuated in a completely closing manner, so that the whole of the water flow supplied to the electrolyser 1 via the inlet 2 is conveyed through the line 14 and thus through the ion exchanger unit 17, in order to ensure that an impermissibly high loading of the electrolyser 1 with metal ions does not develop even in this start-up situation. The valve 20 is opened either in a time-controlled or temperature-controlled manner or as a function of the metal ion concentration in the line 10 until finally, the above-described flow conditions are set in the run-in state, in which conditions only a comparatively small partial flow is still supplied through the line 14 and a considerably larger partial flow is supplied through the line 13 to the electrolyser 1.

[0036] FIG. 2 illustrates how advantageously, in an electrolysis device according to FIG. 1, first a cooling of the water carried in the line 14 and, after flowing through the ion exchanger unit 17, a subsequent heating takes place. To this end, a heat exchanger 21 is connected downstream of the ion exchanger unit 17, which heat exchanger is connected via a common heat cycle to the heat exchanger 12 for cooling down the water. The heat exchangers 12 and 21 are connected to one another via a line 22, from which a line 23 to a cooling set 24 branches, to the output line 25 of which a mixing valve 26 is supplied, which is connected to the line coming from the heat exchanger 21 and into which a line 27 furthermore opens, which leads to the heat exchanger 12. Using this arrangement, the cooling down of the water carried in the line 14 upstream of the ion exchanger unit 17 and the subsequent heating via the heat exchanger 21 can take place substantially without external energy, if required, additional cooling is provided by the cooling set 24.

[0037] The configuration according to FIG. 3 is more extensive with regards to the heat carrying in a common temperature control circuit. There, the cooling unit connected via the heat exchanger 12 in FIG. 1 is connected to the previously described temperature control device for the ion exchanger unit 17, as has been described on the basis of FIG. 2. There, the output of the heat exchanger 12 and that of the heat exchanger 19 is supplied to the line 22, the output of the heat exchanger 21 and the output of the cooling set 24 are supplied to the mixing valve 26, which does not lead directly to the heat exchanger 19 however, but rather is connected via a further mixing valve 28 and a line 29 to the inlet of the heat exchanger 19 and the mixing valve 26.

[0038] In the temperature control device illustrated on the basis of FIG. 3, the heat of the entire water flow can therefore be used, which is advantageous in particular with regards to the heating following the ion exchanger unit 17 in the heat exchanger 21.

[0039] On the basis of FIG. 3, it is furthermore illustrated that three ion exchanger units 17, each consisting of a first ion exchanger 15 and a second ion exchanger 16 connected downstream of the same in the flow direction, are connected in parallel. This parallel arrangement clarifies only by way of example that by connecting a plurality of such ion exchanger units 17 in parallel, ion exchangers of virtually any desired size can be used, without having to fall back on custom-made devices here. The ion exchanger units 17 are configured in such a manner, which is known per se, that with the ageing of the ion exchanger material, if this therefore approaches its saturation, first the ion exchanger material from the downstream-connected ion exchanger 16 is placed into the upstream-connected ion exchanger 15 and the ion exchanger 16 is provided with fresh ion exchanger material, in order therefore to ensure that the treatment in the downstream-connected second ion exchanger 16 is always more intensive than in the upstream-connected ion exchanger 15.

[0040] In this case, the dimensioning of the parallel-connected ion exchanger units is configured such that at least one ion exchanger unit 17 more is present than would be required for the actual operation of the electrolysis device. This ion exchanger unit 17 can then be taken out of operation by valves, which are not illustrated here in detail, if the ion exchanger material is to be exchanged or replaced for maintenance purposes, as described previously.

[0041] The electrolysis device illustrated on the basis of the figures and described previously has a central control system, which controls both the start-up and the continuous operation automatically. Feedback control cycles are incorporated in this case, which in particular actuate the mixing valves of the temperature control circuit in a suitable manner. This control system also comprises the actuation of the shut-off valve 20 and the circulation pumps 11 and 18.

[0042] 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.