Methods for operating an electrolysis plant and electrolysis plant

Abstract

Method for operating an electrolysis plant (2) with an electrode assembly (4), with a water reservoir (16) to which fresh water can be supplied by means of a water supply (24), and with a heat exchanger (18) connected between the water reservoir (16) and the electrode assembly (4), - wherein water for temperature control is directed from the water reservoir (16) to the heat exchanger (18), - wherein the heat exchanger (18) is used to temper the water supplied to it depending on a valve position (p V ) and / or a time course of the valve position (p V ) of a valve (26) of the water supply (24) is adjusted, - where a temperature expectation value (T E ) for the temperature of the water in the water reservoir based on the valve position (p V ) and / or based on the temporal progression of the valve position (p V) is determined, wherein the heat exchanger (18) is determined as a function of the expected temperature value (T E ) is set up, and - wherein the tempered water is directed to the electrode assembly (4).

Description

[0001] The invention relates to a method for operating an electrolysis plant for the production of gaseous hydrogen.

[0002] An electrolysis plant has a water circuit through which water flows to an electrode assembly. At the electrode assembly, the water is split into oxygen and hydrogen. The water flowing to the electrode assembly is also used for temperature control, specifically for temperature regulation.

[0003] A heat exchanger is typically installed between the water reservoir and the electrode assembly to regulate the water temperature. The temperature of the water supplied to the electrode assembly is measured, for example, by a temperature sensor positioned between the heat exchanger and the electrode assembly, oriented with respect to the water flow direction.

[0004] A disadvantage is that the water supplied to the electrode assembly exhibits comparatively large temperature fluctuations, especially if the temperature sensor is located directly after the heat exchanger and other components are positioned between the heat exchanger and the electrode assembly. Furthermore, temperature fluctuations can result from the addition of fresh water to the water reservoir.

[0005] For example, additional temperature sensors, in particular a temperature sensor to measure the (water) temperature of the water in the water reservoir, are used in a comparatively elaborate and / or costly manner to control the heat exchanger more precisely.

[0006] From WO 2021 / 228 412 A1, a method for operating a water electrolysis device for producing hydrogen and oxygen from water is known. The water electrolysis device comprises a PEM electrolyzer to which water for producing the hydrogen and oxygen is supplied, along with water for cooling. The cooling water is circulated and treated by means of an ion exchange unit. Only a portion of the circulated water is fed to the ion exchange unit, while another portion is fed to the PEM electrolyzer via a bypass, bypassing the ion exchange unit.

[0007] EP 2 623 640 A1 discloses an electrolyzer for producing hydrogen and oxygen by splitting water. In this electrolyzer, waste heat generated in the electrolyzer is stored in a heat transfer medium, which is then fed to a water treatment plant. In the water treatment plant, deionized water is produced from raw water using the waste heat.

[0008] The invention is based on the objective of providing a particularly suitable method for operating an electrolysis plant, by virtue of which temperature fluctuations of the water at the electrode assembly are avoided or at least reduced. Furthermore, such an electrolysis plant is to be described.

[0009] The process serves to operate an electrolysis plant, which is specifically designed for the production of gaseous hydrogen from water. The electrolysis plant comprises an electrode assembly for splitting water into hydrogen and oxygen. Advantageously, the electrode assembly includes or comprises a PEM electrolyzer (proton exchange membrane electrolyzer), wherein, for the electrolysis of water, the water is preferably supplied to the anode of the electrolyzer.

[0010] The electrolysis system also includes a water reservoir, such as a water tank. This serves as an (intermediate) storage tank for water used in the electrolysis process. Fresh water can be supplied to the reservoir via a water inlet. This inlet has a valve that allows the amount and / or rate of fresh water supplied to the reservoir to be adjusted.

[0011] A heat exchanger is arranged between the water reservoir and the electrode assembly; in other words, from a fluid dynamics perspective, the heat exchanger is connected between the water reservoir and the electrode assembly.

[0012] As per the procedure, water is directed from the water reservoir to the heat exchanger. The water is tempered by the heat exchanger. In other words, the water's temperature is adjusted using the heat exchanger. Specifically, the water is cooled or heated by the heat exchanger.

[0013] To temper the water supplied from the water reservoir, the heat exchanger is adjusted depending on the position of the water supply valve and / or the time-dependent position of the water supply valve. Specifically, the position of a (heat exchanger) valve, which controls the flow rate of a tempering medium through the heat exchanger, is adjusted depending on the position of the water supply valve or the time-dependent position of the water supply valve.

[0014] It is advantageous to temper the water in such a way that its temperature corresponds to a predetermined target value, or that its temperature lies within a predetermined target temperature range.

[0015] The tempered water is directed to the electrode assembly. There, at least a portion of the supplied water is split into hydrogen and oxygen. In other words, the electrode assembly performs electrolysis on at least a portion of the supplied water. During this process, water is split, with hydrogen being produced at the cathode and oxygen at the anode. The hydrogen is then extracted from the electrode assembly and, for example, stored.

[0016] Because the heat exchanger is adjusted according to the fresh water supply to the water reservoir, its influence on the water temperature in the reservoir is taken into account. This allows for comparatively precise temperature control of the water. Consequently, temperature fluctuations of the water at the electrode assembly are avoided or at least the risk of them being affected is significantly reduced.

[0017] Furthermore, it is advantageous that no temperature sensor is needed to measure the temperature of the water in the water reservoir or the temperature of the water supplied to the heat exchanger. In fact, such a sensor is not used. This results in a comparatively inexpensive electrolysis system.

[0018] Based on a (first) assignment, which is designed, for example, as an (assignment) table, as a characteristic curve or as an assignment rule (assignment function), a setting parameter for the heat exchanger, in particular a valve position for the heat exchanger valve, can be assigned to the valve position of the water supply valve.

[0019] Additionally or alternatively, the setpoint for the heat exchanger is assigned to the temporal profile of the water supply valve position. For this purpose, a duration of the open state of the water supply valve, a valve opening degree of the water supply valve, and / or a period for a periodically opened water supply valve are determined from the temporal profile of the valve position, and the setpoint for the heat exchanger is assigned to at least one of these values ​​using a (second) assignment, which is, for example, designed as a (assignment) table, a characteristic curve, a characteristic map, or an assignment rule.

[0020] For example, the valve position or its temporal progression of the water supply valve is derived from a control signal for this; in other words, the valve position or its temporal progression is determined based on the control signal for the water supply valve.

[0021] Furthermore, an expected temperature value for the temperature of the water in the water reservoir is first determined based on the valve position and / or the time course of the valve position of the water supply valve.

[0022] For example, the expected temperature value is assigned to the valve position based on a (third) assignment, which may be in the form of a (assignment) table, a characteristic curve, or an assignment rule. Alternatively, the duration of the open state of the water supply valve, the degree of opening of the water supply valve, and / or the period for a periodically opened water supply valve are determined from the time course of the valve position, and the expected temperature value is assigned to at least one of these values ​​based on a (fourth) assignment, which may be in the form of a table, a characteristic curve, a characteristic map, or an assignment rule.

[0023] The expected temperature value represents the anticipated actual temperature of the water in the reservoir. The temperature of the water in the reservoir is not measured; in other words, the expected temperature value is not a measured temperature value. The expected temperature value is determined, specifically calculated, without the use of a temperature sensor.

[0024] The heat exchanger, and in particular the valve position of its heat exchanger valve, is then adjusted depending on the expected temperature value. Preferably, the expected temperature value is used as a parameter, especially as a (feed-)control parameter, in a control loop for controlling the temperature of the water supplied to the electrode assembly, i.e., the temperature of the water immediately before the electrode assembly, and / or for controlling the temperature of the water tempered by the heat exchanger, i.e., the temperature of the water immediately after the heat exchanger. The expected temperature value is preferably used for feedforward control within the control loop.

[0025] In summary, one assignment, namely the first, the second, the third, or the fourth assignment, is used for adjusting the heat exchanger depending on the valve position or depending on its temporal progression.

[0026] The first, second, third, and / or fourth assignments were determined, preferably in advance, by means of a simulation. During this simulation, all volume flows of water into and out of the water reservoir are determined. The temperature of the water in each volume flow, especially the initial temperature, and / or any temperature change of the respective volume flow as it passes through a component of the electrolysis system, is suitably specified for the simulation and / or calculated during the simulation. In particular, the amount of waste heat from the electrode assembly during electrolysis is also calculated, especially based on the electrical power consumption of the electrode assembly during electrolysis, and / or a corresponding expected value is specified.

[0027] It is advantageous to store the first, second, third, and / or fourth assignments in a memory of a control and / or regulation unit of the electrolysis plant.

[0028] In a suitable configuration, the temperature of the water supplied to the electrode assembly and / or the temperature of the water tempered by the heat exchanger is measured. The measured temperature of the water supplied to the electrode assembly or of the water tempered by the heat exchanger is used to adjust the heat exchanger. In other words, the heat exchanger is adjusted based on the measured temperature of the water supplied to the electrode assembly or of the water tempered by the heat exchanger.

[0029] Preferably, the measured temperature of the water supplied to the electrode device or of the water tempered by the heat exchanger is used as a control variable for the control loop for regulating the temperature of the water supplied to the electrode device and / or for regulating the temperature of the water tempered by the heat exchanger.

[0030] Another aspect of the invention relates to an electrolysis plant, which can be operated and / or is operated in particular according to one of the variants of the method described above. The electrolysis plant is therefore specifically intended for the production of gaseous hydrogen from water.

[0031] The electrolysis system comprises the electrode assembly for splitting water into hydrogen and oxygen, which is designed, for example, as a PEM electrolyzer or incorporates one, as well as the water reservoir, to which fresh water can be supplied. The electrolysis system also includes the heat exchanger for temperature control of the supplied water, with the heat exchanger being fluidically connected between the water reservoir and the electrode assembly.

[0032] The electrolysis plant further comprises means for carrying out the process steps of the process according to one of the variants described above. These means include, in particular, the control unit and / or a (temperature) sensor for measuring the temperature of the water supplied to the electrode assembly or for measuring the temperature of the water immediately after the heat exchanger. Suitablely, the means also includes the heat exchanger valve and / or the water supply valve.

[0033] In particular, the control unit is designed and configured to control the heat exchanger depending on the position of the water supply valve and / or the time course of this valve position. Preferably, the control unit is designed and configured to determine the expected temperature value based on the valve position and / or the time course of the valve position and to control the heat exchanger based on the expected temperature value.

[0034] Advantageously, the water reservoir is without a temperature sensor. Therefore, the electrolysis system does not have a sensor to measure the temperature of the water in the reservoir. Preferably, the electrolysis system also does not have a sensor to measure the temperature of the water between the reservoir and the heat exchanger.

[0035] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 an electrolysis plant with an electrode assembly, with a water reservoir and with a heat exchanger connected between the water reservoir and the electrode assembly, Fig. 2. A flowchart shows a process flow for operating the electrolysis plant, wherein the heat exchanger is adjusted depending on an expected temperature value for the temperature of the water in the water reservoir, and Fig. 3 schematically shows a control loop for regulating the temperature of the water supplied to the electrode device.

[0036] Corresponding parts and sizes are always marked with the same reference symbols in all figures.

[0037] In the Fig. Figure 1 shows an electrolysis plant 2 for the production of gaseous hydrogen from water.

[0038] To split water and produce gaseous oxygen and gaseous hydrogen, the electrolysis plant includes an electrode assembly 4. This assembly comprises, for example, a PEM electrode stack with a number of PEM electrolyzers. During electrolysis, gaseous oxygen is produced at the anode 6 and gaseous hydrogen at the cathode 8. The hydrogen is then expediently fed to a water separator 10 and subsequently to a gas heat exchanger 12.

[0039] The electrolysis system 2 has a pump 14, which supplies water from a water reservoir 16 to the electrode assembly 4. The water temperature can be adjusted via a heat exchanger 18, so that the temperature of the water at the electrode assembly 4 is adjustable and / or controllable. Thus, the water reservoir 16 is fluidically connected to the electrode assembly 4, with the heat exchanger 18 fluidically positioned between the electrode assembly 4 and the water reservoir 16.

[0040] For flow control purposes, an ion exchanger 20 is advantageously connected between the heat exchanger 18 and the electrode assembly 4. For example, a control valve 22 is suitably connected between the heat exchanger 18 and the electrode assembly 4, specifically between the ion exchanger 20 and the electrode assembly 4. This valve serves to adjust the quantity and / or rate of the tempered water supplied to the electrode assembly 4. Alternatively or additionally, the quantity and / or rate of the water supplied to the electrode assembly 4 can be adjusted using the pump 14.

[0041] Water that has not been split by the electrode assembly 4 can be supplied to the water reservoir 16. Additionally, fresh water can be supplied to the water reservoir 16 via a water supply 24. The water supply 24 includes a (water supply) valve 26, which allows the quantity and / or rate of fresh water supplied to the water reservoir 16 to be adjusted.

[0042] The water supply valve 26 is controlled by a control and / or regulating unit 28 (control and / or regulating device 28). For this purpose, the water supply 24, in particular its water supply valve 26, is connected to the control and / or regulating unit 28 via signal and / or data transmission. To set the valve position p v The water supply valve 26 outputs a corresponding control signal Sv to the water supply 24, in particular to its water supply valve 26.

[0043] The electrolysis system includes a temperature sensor 30 for measuring the temperature of the water supplied to the electrode assembly 4. For this purpose, the temperature sensor 30 is arranged such that it measures the water temperature directly upstream of the electrode assembly 4. Alternatively, and in the Fig. Figure 1, therefore, shows the temperature sensor 30 for measuring the temperature of the water tempered by the heat exchanger 18. For this purpose, it is arranged directly downstream of the heat exchanger 18 in terms of flow characteristics. The temperature sensor 30 may be connected to the control unit 28 via signal and / or data transmission to supply the measured values ​​or data or signals generated therefrom.

[0044] The heat exchanger 18 includes a (heat exchanger) valve 32 for adjusting the flow rate, in particular the quantity and / or rate of the flow, of a temperature control medium through the heat exchanger. Thus, the cooling and / or heating capacity of the heat exchanger 18 is set via the heat exchanger valve 32. The heat exchanger valve 32 is connected to the control unit 28 via signal and / or data transmission. The heat exchanger valve 32, and in particular its valve position, can therefore be controlled by the control unit 28. For this purpose, the control unit 28 outputs a control signal Sw for the heat exchanger 18, specifically for the valve position of its valve 32.

[0045] Electrolysis system 2 has neither a temperature sensor for measuring the water temperature in water reservoir 16 nor a temperature sensor for measuring the water temperature of the water supplied to reservoir 18. Therefore, water reservoir 16 is without a temperature sensor.

[0046] In the Fig. Figure 2 shows a schematic flowchart illustrating the process flow for operating electrolysis plant 2. Fig. 1 represents. When the electrolysis plant 2 is in operation, in a first step I water is directed from the water reservoir 16 to the heat exchanger 18.

[0047] In a second step II, the water supplied to the heat exchanger 18 is tempered. Here, the temperature of the heat exchanger 18, specifically its heat exchanger valve 32, is adjusted as a function of the temperature T. w The temperature T is set by the water supplied by electrode assembly 4. wThe temperature of the water supplied to the electrode assembly 4 is detected by the temperature sensor 30 and transmitted to the control and / or regulation unit 28.

[0048] Furthermore, the adjustment of the heat exchanger valve 32 depends on the valve position p. v of the water supply valve 26 and / or depending on its temporal progression. For this purpose, the control signal Sw for the heat exchanger 18 is used. An example is shown below in connection with the Fig. 3 more precisely shown how, based on the temperature T w and based on the valve position p v or its temporal progression, the control signal Sw is determined.

[0049] In step III, the tempered water is directed to the electrode assembly 4, where it is split into hydrogen and oxygen.

[0050] In summary, the control and / or regulating unit 28, the temperature sensor 30, the heat exchanger valve 32 and / or the water supply valve 26 are referred to as means for carrying out the procedure.

[0051] In the Fig. Figure 3 schematically represents a control loop 34 for controlling the temperature T w of the water supplied to the electrode assembly 4 is shown. Here, a difference between a temperature setpoint 30 and the measured temperature T is calculated. w The result of this difference is fed to a control device 36 of the control and / or regulation unit 28. The control device 36 is, for example, configured as an I-controller or a PL-controller. The measured temperature T w This is therefore the controlled variable for control loop 34.

[0052] The control signal Sv for the water supply valve 26 is evaluated by an evaluation unit 38 of the control and / or regulation unit 28. Here, the valve position p corresponding to the control signal Sv is determined based on an assignment, which is implemented, for example, as an assignment table, a characteristic curve, a characteristic map, or an assignment function. v and / or one or more quantities determined from the control signal Sv, in particular from its temporal progression, such as a duration for an open state of the water supply valve 26, a valve opening degree for the water supply valve 26, and / or a period duration for a periodically open water supply valve 26, a temperature expectation value T E assigned. The expected temperature value T represents E the expected temperature T w of the water supplied to electrode assembly 4. In summary, the valve position pv or its temporal progression, the expected temperature value T E , in other words, the expected temperature value T E based on the valve position p V or determines their temporal course.

[0053] The assignment is appropriately stored on a memory of the control and / or regulation unit 28, in particular its evaluation unit 38, which is not shown further.

[0054] In summary, the evaluation unit 38 is used to determine the valve position p. v and / or an expected temperature value is determined for the temperature of the water supplied to electrode assembly 4 over its time course. Therefore, an expected value calculation is performed.

[0055] Based on the determined expected temperature value T E as well as based on the result R issued by the control unit 36 EThe control signal Sw for the heat exchanger 18 is determined by the control system. A corresponding rule is conveniently stored in the memory of the control and / or regulating device 28. For example, the expected temperature value T is... E as well as the result R E Each value is weighted and added together, and a signal corresponding to the sum is used as the control signal S. W Issued for heat exchanger 18.

[0056] In summary, the expected temperature value T E for feed-forward control in control loop 34. In further summary, the heat exchanger 18 is controlled depending on the expected temperature value T. E The system is set. The control loop is marked with the reference number 40.

[0057] The invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived by a person skilled in the art within the scope of the claims, without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiments and / or in the claims can also be combined with one another in other ways without departing from the subject matter of the invention. Reference symbol list 2 Electrolysis plant 4 Electrode system 6 Anode 8 Cathode 10 Water separator 12 gas heat exchangers 14 Pump 16 Water reservoir 18 heat exchangers 20 ion exchangers 22 Control valve 24 Water supply 26 (Water supply) valve 28 Control and / or regulating unit 30 Temperature sensor 32 (heat exchanger) valve 34 Control loop 36 Control unit 38 Evaluation unit 40 Control section p V Valve position R E Result S V Control signal for the water supply valve S W Control signal for the heat exchanger T E Expected temperature value T S Target temperature value T W Temperature of the water supplied to the electrode assembly I. Directing water from the water reservoir to the heat exchanger II Tempering the water III. Directing water from the heat exchanger to the electrode assembly

Claims

[1] Method for operating an electrolysis plant (2) with an electrode assembly (4), with a water reservoir (16) to which fresh water can be supplied by means of a water supply (24), and with a heat exchanger (18) connected between the water reservoir (16) and the electrode assembly (4), - wherein water for temperature control is directed from the water reservoir (16) to the heat exchanger (18), - wherein the heat exchanger (18) is used to temper the water supplied to it depending on a valve position (p V ) and / or a time course of the valve position (p V ) of a valve (26) of the water supply (24) is adjusted, - where a temperature expectation value (T E ) for the temperature of the water in the water reservoir based on the valve position (p V ) and / or based on the temporal progression of the valve position (p V) is determined, wherein the heat exchanger (18) is determined as a function of the expected temperature value (T E ) is set up, and - wherein the tempered water is directed to the electrode assembly (4). [2] Method according to claim 1, characterized by , that the expected temperature value (T E ) is used for a feedforward control in a control loop (34) for controlling the temperature of the water supplied to the electrode device. [3] Method according to claim 1 or 2, characterized by , - that the temperature (T W ) of the water supplied to the electrode assembly (4) and / or of the water tempered by means of the heat exchanger (18) is detected, and - that the heat exchanger (18) depending on the detected temperature (T W ) is set up. [4] Method according to claims 2 and 3, characterized by , that the recorded temperature (T W) is used as the controlled variable for the control loop (34). [5] Electrolysis system (2), comprising - an electrode device (4) for splitting water into hydrogen and oxygen, - a water reservoir (16) to which fresh water can be supplied by means of a water supply (24), - a heat exchanger (18) which is fluidically connected between the water reservoir (16) and the electrode assembly (4), as well as - a means (ME) for carrying out the method according to any one of claims 1 to 4. [6] Electrolysis system (2) according to claim 5, characterized by , that the water reservoir (16) is without a temperature sensor.

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