System for electrochemical processing and method for preventing electrode deterioration - Patents.com

Abstract

The system for electrochemical processing includes an electrochemical reactor 101, a power supply 104 for providing a controllable DC voltage to multiple electrodes of the electrochemical reactor, a measurement device 105 for generating measurement data indicative of the formation of product gas in the system, and a controller 106 configured to receive an idle command to place the system in an idle state and to reduce the DC voltage when the measurement data indicates the formation of product gas and the DC voltage exceeds a lower limit of a safe voltage region without electrode degradation. Thus, in the idle state, the DC voltage is reduced by an amount necessary to stop the formation of product gas, but not further. Thus, in the idle state, degradation, such as corrosion, of the electrodes can be avoided or at least reduced.

Description

[Technical field]

[0001] The present disclosure relates to systems for electrochemical processes, such as alkaline water electrolysis, proton exchange membrane "PEM" water electrolysis, or saturated saline electrolysis. Additionally, the present disclosure relates to methods for preventing degradation, such as corrosion, of electrodes in electrochemical reactors. Additionally, the present disclosure relates to computer programs for preventing degradation of electrodes in electrochemical reactors. [Background technology]

[0002] An electrochemical process in which a substance interacts with an electrode can be, for example, an electrolysis process such as water electrolysis, in which electrical energy is converted into chemical energy carried by hydrogen gas H2 and oxygen gas O2 is produced as a by-product. A direct current is passed between the electrodes, producing hydrogen gas at the cathode or negative electrode and oxygen gas at the anode or positive electrode. Faraday's law of electrolysis states that the production of hydrogen gas is directly proportional to the charge transferred at the electrodes. Thus, the average value of the direct current determines the rate of hydrogen gas production.

[0003] Alkaline water electrolysis is a widely used and mature water electrolysis technology. An alkaline water electrolysis reactor comprises multiple electrodes operating in a liquid electrolyte solution, e.g., potassium hydroxide KOH or sodium hydroxide NaOH. The multiple electrodes are separated by a non-conductive porous diaphragm. This diaphragm prevents mixing of hydrogen H2 and oxygen O2 gases produced at the cathode and anode electrodes, respectively. Hydroxide ions penetrate the porous diaphragm, thereby providing the ionic conductivity required for the electrolysis process. The stack structure of an alkaline water electrolysis reactor can comprise relatively low-cost materials such as nickel and stainless steel as the electrodes. Another water electrolysis technology is proton exchange membrane "PEM" water electrolysis. In contrast to alkaline water electrolysis, PEM water electrolysis reactors utilize a solid and acidic electrolyte. The electrolyte transports protons from the anode to the cathode and acts as a gas separator membrane. Typically, sulfonated fluoropolymers are used as the solid electrolyte. The sulfonic acid side chains of this polymer, HSO3, are ionic bonds, and due to these ionic bonds, H + and SO3 - There is a strong attraction between sulfonic acids and water, and their proton conduction depends on hydration. Due to the acidity of the membrane, the catalyst materials for PEM water electrolysis reactors are typically selected from platinum group metals, most often iridium for the anode and platinum for the cathode. A third exemplary electrolysis technique is the electrolysis of saturated salt solutions, such as chlor-alkali electrolysis.

[0004] Lifetime is an essential factor for electrolysis reactors of the above mentioned kind. Typically, the lifespan of an electrolysis reactor stack structure is about 10 years, the stack structure typically representing about half of the investment cost of an industrial electrolysis plant. The lifespan of an industrial electrolysis reactor is characterized by the operation time and the maximum number of start-stop cycles. Cathode degradation is the factor limiting the lifespan of the stack structure. Cathode degradation is further intensified when the operation of the electrolysis reactor is interrupted and the direct current voltage supplied to the electrodes falls below the system-specific voltage limit. This voltage limit is defined by the material of each electrode and the operating conditions such as temperature, pressure and pH of the electrolyte.

[0005] Taiwan Patent Publication No. 201308741 describes a method for preventing voltage reversal in a water electrolysis cell when the cell is idle and hydrogen gas production is thereby stopped. The method presented in the patent document 1 comprises supplying to the electrodes of the water electrolysis cell a protection voltage that is lower than a known a priori voltage required to initiate and maintain the water electrolysis process in the water electrolysis cell. However, the method presented in the patent document 1 is not without challenges. One of the challenges relates to typical industrial electrochemical reactors that comprise multiple cells connected in series and possibly parallel connections of the series-connected sections. In these electrochemical reactors, the stack voltage does not reveal information about how the individual cell voltages are divided. Therefore, it can be difficult to determine a suitable protection voltage for the above-mentioned type of industrial electrochemical reactor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Taiwan Patent Application Publication No. 201308741 Summary of the Invention

[0007] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of various embodiments. This summary is not an extensive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents some concepts in a simplified form as a prelude to a more detailed description of exemplary and non-limiting embodiments.

[0008] In accordance with the present invention, a system is provided for a new electrochemical process which may be, but is not necessarily, for example, alkaline water electrolysis, proton exchange membrane "PEM" water electrolysis, or saturated salt water electrolysis, such as a chlor-alkali electrolysis process.

[0009] The system according to the present invention comprises: an electrochemical reactor for containing an electrolyte, the electrochemical reactor comprising a plurality of electrodes for conducting an electric current to the electrolyte; a power supply configured to provide a controllable DC voltage to a plurality of electrodes of the electrochemical reactor; a measurement device configured to generate measurement data indicative of the formation of at least one product gas, e.g., hydrogen gas, H2; and a controller communicatively connected to the power source and the measurement device, the controller configured to reduce the DC voltage in response to a situation in which: i) the controller receives an idle command to place the system in an idle state; ii) the measurement data indicates the formation of product gas; and iii) the DC voltage exceeds a lower limit of a safe voltage area without degradation of the electrodes.

[0010] Thus, during idle conditions, the DC voltage is reduced only by the amount necessary to stop the formation of product gas, but no further, thus avoiding or at least reducing degradation, such as corrosion, of the electrodes during idle conditions, thereby extending the life of the electrochemical reactor.

[0011] The present invention also provides a new method for preventing degradation, such as corrosion, of the electrodes of an electrochemical reactor during idle conditions of the electrochemical reactor. The method according to the invention comprises the steps of: providing a controllable DC voltage to electrodes of an electrochemical reactor; generating measurement data indicative of formation of at least one product gas of the electrochemical reactor; (i) reducing the DC voltage in response to a situation where the measurement data indicates the formation of product gas and (ii) the DC voltage exceeds a lower limit of a safe voltage region without degradation of the electrodes.

[0012] The present invention also provides a novel computer program for preventing degradation of electrodes in an electrochemical reactor during idle conditions of the electrochemical reactor. The computer program according to the present invention comprises: Controlling a power supply for providing a controllable direct current voltage to the electrodes of the electrochemical reactor; receiving measurement data indicative of formation of at least one product gas of the electrochemical reactor; The power supply includes computer executable instructions for controlling the programmable processor to control the power supply to reduce the DC voltage in response to a condition where: i) the measurement data indicates the formation of product gas; and ii) the lower limit of a safe voltage region without degradation of the electrodes is exceeded.

[0013] According to the present invention there is also provided a novel computer program product comprising a non-volatile computer readable medium, for example a compact disc "CD", encoded with a computer program according to the present invention.

[0014] Exemplary and non-limiting embodiments are set forth in the accompanying dependent claims.

[0015] Various exemplary and non-limiting embodiments, both as to structure and method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplary and non-limiting embodiments when read in conjunction with the accompanying drawings.

[0016] The verbs "to comprise" and "to include" are used herein as open-ended limitations which neither exclude nor require the presence of unrecited features.

[0017] The features recited in the dependent claims are mutually freely combinable, unless expressly stated otherwise.

[0018] Furthermore, it will be understood that throughout this specification the use of the articles "a" or "an", ie the singular, does not exclude a plural.

[0019] Exemplary and non-limiting embodiments and their advantages are explained in more detail below, by way of example and with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 illustrates a system according to an exemplary and non-limiting embodiment for electrochemical processing. [Diagram 2] FIG. 2 shows an exemplary, non-limiting embodiment Pourbaix diagram according to the prior art, utilized in an exemplary, non-limiting embodiment system for electrochemical processing. [Diagram 3] FIG. 3 shows a flow chart of a method for preventing degradation of electrodes in an electrochemical reactor according to an exemplary and non-limiting embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Specific examples provided in the specification set forth below should not be construed as limiting the scope and / or applicability of the appended claims. The lists and groups of examples provided in the description given below are not exhaustive unless expressly stated otherwise.

[0022] FIG. 1 shows a system according to an exemplary and non-limiting embodiment for electrochemical processing. The system comprises an electrochemical reactor 101 containing an electrolyte and comprising electrodes for conducting a current through the electrolyte. In FIG. 1, two of the electrodes are indicated with reference numbers 102 and 103. In the exemplary system shown in FIG. 1, the electrochemical reactor 101 comprises a stack of electrolytic cells. The electrolytic cells may contain, for example, an alkaline liquid electrolyte for alkaline water electrolysis. The alkaline liquid electrolyte may comprise, for example, an aqueous potassium hydroxide solution "KOH" or an aqueous sodium hydroxide solution "NaOH". However, it is also possible for the electrolytic cells to contain other electrolytes. In this exemplary system, each of the electrolytic cells comprises an anode, a cathode, and a porous diaphragm that divides the electrolytic cell into a cathode compartment containing the cathode and an anode compartment containing the anode. The diaphragm prevents mixing of hydrogen H2 and oxygen O2 gases produced at the cathode and anode electrodes, respectively. The hydroxide ions penetrate the porous diaphragm, thereby providing the ionic conductivity required for the electrolysis process. The system may, for example, comprise tens or hundreds of electrolytic cells. However, the system according to the exemplary and non-limiting embodiment may comprise 1 to 10 electrolytic cells. In the exemplary system shown in FIG. 1, the electrolytic cells are electrically connected in series. However, the electrolytic cells of the system according to the exemplary and non-limiting embodiment may be electrically connected in parallel, or the electrolytic cells may be arranged to form a series-connected group of parallel-connected electrolytic cells, or a parallel-connected group of series-connected electrolytic cells, or the electrolytic cells may be electrically connected to each other in some way.

[0023] 1, the electrochemical reactor 101 includes a hydrogen separator tank 126 and piping from the cathode compartment of the electrolysis cell to the hydrogen separator tank 126. The electrochemical reactor 101 includes an oxygen separator tank 127 and piping from the anode compartment of the electrolysis cell to the oxygen separator tank 127. The electrochemical reactor 101 may further include circulation piping for circulating liquid electrolyte from the bottom of the hydrogen separator tank 126 and from the bottom of the oxygen separator tank 127 to the electrolysis cell. The circulation piping is not shown in FIG. 1.

[0024] This device is a controllable DC U DC The power supply 104 includes a power source 104 configured to supply AC voltage to the electrodes of the electrochemical reactor 101. In the exemplary system shown in FIG. 1, the power source 104 includes a transformer bridge 113 having AC voltage terminals for receiving AC voltage and DC voltage terminals for supplying DC current to the electrodes of the electrochemical reactor 101. The transformer bridge 113 includes transformer legs 120, 121, and 122, each with one of the AC voltage terminals and connected between a plurality of DC voltage terminals. Each of the transformer legs includes a bidirectional upper branch controllable switch between the AC voltage terminal of the converter leg under consideration and a positive one of the DC voltage terminals, and a bidirectional lower branch controllable switch between the AC voltage terminal of the converter leg under consideration and a negative one of the DC voltage terminals. In FIG. 1, the bidirectional upper branch controllable switch of the transformer leg 121 is indicated with reference numeral 123, and the bidirectional lower branch controllable switch of the transformer leg 121 is indicated with reference numeral 124. In this exemplary case, each bidirectional controllable switch comprises an insulated gate bipolar transistor "IGBT" and a retrograde diode. However, it is also possible that each bidirectional controllable switch comprises, for example, a gate turn-off thyristor "GTO", or a metal oxide field effect transistor "MOSFET", or some other suitable semiconductor switch instead of an IGBT. The forced commutation of the bidirectional switches of the transformer bridge 113 makes it possible to reduce current ripples in the direct current supplied to the electrodes of the electrochemical reactor 101. Furthermore, the forced commutation of the bidirectional switches makes it possible to control the power factor of the alternating voltage supply of the system.

[0025] In the exemplary system shown in FIG. 1, the power supply 104 comprises a transformer 115 for transferring power from an AC voltage network 116 to a transformer bridge 113 via an inductor-capacitor-inductor “LCL” filter 114. It is also possible that instead of the LCL filter 114, there is only a series inductance between the transformer 115 and the transformer bridge 113. The secondary winding 115 of the transformer is connected to the AC voltage terminals of the transformer bridge 113 via the LCL filter. The secondary voltage of the transformer 115 is advantageously a DC voltage U DC is selected to be low so that the transformer bridge 113 can operate with a suitable duty cycle ratio of the controllable switches when the AC voltage is in a range suitable for the electrochemical reactor 101. DC The conversion to is done in a single step, which typically results in a voltage boost characteristic for the transformer bridge 113. The transformer 113 may be provided with a tap changer to vary the transformation ratio of the transformer. The tap changer is not shown in FIG.

[0026] 1, the power supply 104 further comprises a rechargeable converter 117 for controllably charging a DC voltage capacitor 125 connected to the DC voltage terminals of the transformer bridge 113 during a start-up phase of the system. The rechargeable converter 117 may comprise, for example, a thyristor bridge or any other suitable controllable alternating current voltage to direct current voltage "AC-DC" converter. The power supply 104 further comprises a rechargeable resistor 118 and a bypass switch 119.

[0027] The device comprises a measurement device 105 configured to generate measurement data MD indicative of whether hydrogen gas H2 is produced in the electrochemical reactor 101. In a system according to an exemplary and non-limiting embodiment, the measurement device 105 comprises at least one pressure sensor 109 configured to detect the gas pressure present in the gas space 110 of the electrochemical reactor 101. In this exemplary case, the output signal of the pressure sensor 109 represents at least a part of the measurement data MD. In a system according to an exemplary and non-limiting embodiment, the measurement device 105 comprises at least one gas mass flow sensor 111 configured to detect the gas mass flow rate from the electrolysis cell of the electrochemical reactor 101. In this exemplary case, the output signal of the mass flow sensor represents at least a part of the measurement data MD. The gas mass flow sensor 111 may comprise, for example, a differential pressure flow meter and / or a thermal mass flow meter. In the system according to the exemplary and non-limiting embodiment, the measurement device 105 comprises a gas composition sensor 112 configured to detect the relative content of hydrogen gas H2 in the sample of gas taken from the gas space 110 of the electrochemical reactor 101. In this exemplary case, the output signal of the gas composition sensor 112 represents at least a part of the measurement data MD. The gas composition sensor 112 may comprise, for example, a gas chromatograph and / or a mass spectrometer. In the exemplary system shown in FIG. 1, the measurement device 105 comprises a pressure sensor 109, a gas mass flow sensor 111 and a gas composition sensor 112 to improve the reliability of the measurement data MD. However, the measurement device of the device according to the exemplary and non-limiting embodiment may also comprise only one or two of the above-mentioned devices for detecting whether hydrogen gas H2 is produced or not.

[0028] The system includes a controller 106 communicatively connected to a power source 104 and a measurement device 105. The controller 106 is configured to operate in response to: i) an idle command that causes the controller 106 to set itself to an idle state; ii) measurement data MD indicates the formation of hydrogen gas H2; and iii) a DC voltage U DC In response to a situation where the DC voltage U exceeds the lower limit of the safe voltage region where deterioration of the electrodes does not occur, DCIn a system according to an exemplary and non-limiting embodiment, the controller 106 includes a memory configured to store data indicative of a Pourbaix diagram for a material of the electrode, and the controller 106 is configured to read a lower limit of a safe voltage region from the data indicative of the Pourbaix diagram.

[0029] An example of a Pourbaix diagram for a nickel electrode is shown in Figure 2. The oxygen evolution reaction "OER" and hydrogen evolution reaction "HER" potentials for the normal hydrogen electrode "NHE" are shown as dashed-dotted lines, which can be determined based on the Nernst equation. The reactions involve both electron transfer and proton exchange. The OER and HER lines represent equilibrium points at a particular pH level where each half-reaction can occur. To split water with electrical energy, the potential difference between the anode and cathode of each electrolytic cell must be greater than the difference between the OER and HER lines. At standard ambient conditions, the theoretical minimum voltage, i.e. the required potential difference, is about 1.23 volts. The minimum voltage is a thermodynamic state function that depends on the temperature and partial pressures prevailing, so that an increase in temperature reduces the voltage requirement, while an increase in pressure increases it. The solid lines correspond to the equilibrium between the different chemical species. For example, the horizontal line at -0.39 volts represents the equilibrium between Ni and Ni 2+ ions, and therefore only electron transfer occurs. The vertical lines indicate acid-base reactions, i.e., removal and addition of protons. The Pourbaix diagram can be divided into regions of degradation, passivation, and resistance to degradation such as corrosion. In Figure 1, the cross-hatched regions represent nickel degradation by dissolution, the diagonal hatched regions represent passivation, and the horizontal hatched regions represent resistance. Under acidic conditions, i.e., pH below 7, nickel electrodes should be avoided, especially over a wide potential range, Ni 2+1, dissolution to 0.5V can occur. Instead, the condition shown by the two black dots in FIG. 1 means that the cell voltage is 1.2 volts, which is less than the above-mentioned 1.23 volts, and the lower black dot is in the resistance region, while the upper black dot is in the passivation region, so the electrodes do not degrade and hydrogen gas H2 is not produced. Therefore, the condition shown by the two black dots in FIG. 1 is favorable for keeping the electrochemical reactor 101 idle.

[0030] In the system according to the exemplary and non-limiting embodiment, the electrochemical reactor 101 includes a temperature controller 107 configured to regulate the temperature of the electrolyte and the electrodes. DC The temperature control device 107 is configured to control the temperature controller 107 to change the temperature in response to a situation where the measurement data MD indicates the formation of hydrogen gas H2, even if the maximum voltage is equal to or less than the lower limit of the safe voltage region. As described above, an increase in temperature will reduce the minimum cell voltage required for the electrolysis process. This allows the upper limit of the region where hydrogen gas H2 is not generated to be raised by lowering the temperature. This can therefore be used to find an operating point in an idle state where neither hydrogen gas H2 generation nor electrode deterioration occurs.

[0031] In a system according to an exemplary and non-limiting embodiment, the electrochemical reactor 101 includes a pH controller 108 configured to adjust the pH of the electrolyte. The pH can be adjusted, for example, by adding an acid or a base to the electrolyte, depending on whether the pH is to be increased or decreased. The controller 106 controls a DC voltage U DC is configured to control the pH controller 108 to change the pH of the electrolyte in response to a condition where the measurement data MD indicates the formation of hydrogen gas H2 even if the pH is at most equal to or less than the lower limit of the safe voltage region. The appropriate change in pH to find an idle operating point where neither hydrogen gas H2 generation nor electrode degradation occurs can be derived from the Pourbaix diagram.

[0032] The procedure for controlling the electrochemical reactor 101 in an idle state may, for example, include the following actions: 1) Stopping the electrolysis process by controlling the direct current of the electrochemical reactor 101 to zero; 2) DC voltage U when the DC current reaches zero DC The numerical value of U DC1 The act of preserving 3) Optionally, releasing pressure in the system for safety purposes; and 4) Optionally, purging the system with an inert gas, e.g., nitrogen N2, for safety purposes; 5) Defining safe system pressure levels based on the pressure of the product gas, e.g., H2; 6) The lower limit of the safe voltage area U DCmin The act of defining 7) When the generated gas pressure increases, the DC voltage U DC The above value U is based on the pressure measurement of the product gas, e.g. H2, so that DC1 DC voltage starting with U D The act of controlling 8) If the pressure of any of the produced gases continues to rise, the DC voltage U DC is the lower limit U DCmin If the pH falls below 100, changing the pH in the electrochemical reactor 101 and / or the temperature in the electrochemical reactor 101.

[0033] If the system is purged with an inert gas, such as nitrogen N2, during a shutdown procedure, the presence of the inert gas may corrupt the pressure measurement of one or more of the product gases due to changes in the gas composition. DC can be controlled.

[0034] In the exemplary device shown in FIG. 1, the DC voltage U DC, i.e. the protection voltage, can be maintained and controlled by means of the rechargeable converter 117. The supply of the protection voltage requires only a small amount of electrical energy, since its main purpose is to provide polarization and a sufficient controllable potential across the electrochemical cell, and therefore the power rating of the rechargeable converter 117 can remain low. When the rechargeable converter 117 is used to pre-charge the DC voltage capacitor 125 during the start-up phase, the rechargeable resistor 118 is advantageously used to limit the current. In the idle state, the rechargeable resistor 118 is advantageously bypassed, minimizing losses in the protection voltage supply operation. The electrodes of the electrochemical reactor 101 may be temporarily in the corrosion zone in terms of the potential of the electrodes when switching from the productive use of the electrochemical reactor 101 to the idle state, where the rechargeable converter 117 is utilized to supply the protection voltage. However, the time that may be spent in the corrosion zone is negligible compared to the case in which the protection voltage was not used before in the idle state. Furthermore, if system pressure relief and / or inert gas purging is required upon system shutdown for safety purposes, such safety procedures may lead to situations where the electrodes of the electrochemical reactor 101 are momentarily in the corrosion zone, and in these cases the time spent in the corrosion zone is negligible compared to when in idle condition and no protective voltage is applied.

[0035] 1 may comprise one or more analog circuits, one or more digital processing circuits, or a combination thereof. Each digital processing circuit may be a programmable processor circuit with appropriate software, a dedicated hardware processor such as, for example, an application specific integrated circuit "ASIC," or a configurable hardware processor such as, for example, a field programmable gate array "FPGA." Additionally, the controller 106 may comprise one or more memory circuits, each of which may be, for example, a random access memory "RAM" circuit.

[0036] It should be noted that the present invention is not limited to any particular electrolysis process. For example, a system according to exemplary and non-limiting embodiments may comprise an electrochemical reactor for proton exchange membrane "PEM" water electrolysis, an electrochemical reactor for a solid oxide electrolyte cell "SOEC" process, an electrochemical reactor for electrolysis of saturated salt solutions, such as a chlor-alkali electrolysis process, or an electrochemical reactor for some other electrolysis process.

[0037] FIG. 3 illustrates a flow chart of a method according to an exemplary and non-limiting embodiment for preventing degradation, such as corrosion, of electrodes of an electrochemical reactor during idle conditions of the electrochemical reactor. The method comprises the following acts: An act of providing a controllable DC voltage to electrodes of an electrochemical reactor; an act of generating 302 measurement data indicative of formation of at least one product gas, such as H2, of the electrochemical reactor; and act 303 of reducing the DC voltage in response to a situation where i) the measurement data indicates the formation of product gas and ii) the DC voltage exceeds a lower limit of a safe voltage region without degradation of the electrodes.

[0038] In the method according to the exemplary and non-limiting embodiment, the electrochemical reactor is one of an alkaline water electrolysis reactor, a proton exchange membrane "PEM" water electrolysis reactor, and a saturated saline electrolysis reactor.

[0039] A method according to an exemplary and non-limiting embodiment comprises storing data indicative of a Pourbaix diagram for a material of an electrode, and reading a lower limit of a safe voltage region from the data indicative of the Pourbaix diagram.

[0040] A method according to an exemplary and non-limiting embodiment comprises varying a temperature of an electrode and an electrolyte of an electrochemical reactor in response to a situation in which a measurement signal indicates formation of a product gas while the DC voltage is at most at the lower limit of a safe voltage region.

[0041] A method according to an exemplary and non-limiting embodiment comprises varying the pH of an electrolyte solution of an electrochemical reactor in response to a measurement signal indicating formation of a product gas, even when the DC voltage is at a maximum or at a lower limit of a safe voltage region.

[0042] In a method according to an exemplary and non-limiting embodiment, generating the measurement data comprises detecting a gas pressure present in the gas space of the electrochemical reactor, in this exemplary embodiment, an output signal of the pressure sensor represents at least a portion of the measurement data indicative of the formation of the product gas.

[0043] In a method according to an exemplary and non-limiting embodiment, generating measurement data comprises detecting a gas mass flow rate from one or more electrolytic cells of an electrochemical reactor. In this exemplary embodiment, an output signal of a mass flow sensor represents at least a portion of the measurement data indicative of the formation of product gas. The gas mass flow rate may be detected, for example, with a differential pressure flow meter and / or a thermal mass flow meter.

[0044] In a method according to an exemplary and non-limiting embodiment, generating the measurement data comprises detecting a relative content of the product gas in a sample of gas taken from the gas space of the electrochemical reactor. In this exemplary embodiment, the output signal of the gas composition sensor represents at least a portion of the measurement data indicative of the formation of the product gas. The relative content of the product gas can be detected, for example, using a gas chromatograph and / or a mass spectrometer.

[0045] A computer program according to the exemplary and non-limiting embodiments comprises computer-executable instructions for controlling a programmable processor to perform operations associated with a method according to any of the exemplary and non-limiting embodiments described above.

[0046] A computer program according to an exemplary and non-limiting embodiment comprises a software module for preventing degradation of electrodes of an electrochemical reactor during idle conditions of the electrochemical reactor. This software module is Controlling a power supply for providing a controllable direct current voltage to the electrodes of the electrochemical reactor; receiving measurement data indicative of formation of at least one product gas of the electrochemical reactor; The power supply includes computer executable instructions for controlling the programmable processor to control the power supply to reduce the DC voltage in response to a condition where: i) the measurement data indicates the formation of product gas; and ii) the lower limit of a safe voltage region without degradation of the electrodes is exceeded.

[0047] The software modules described above may be, for example, subroutines or functions implemented in a suitable programming language.

[0048] A computer program product according to an exemplary and non-limiting embodiment comprises a computer readable medium, for example a compact disc "CD", encoded with a computer program according to one embodiment.

[0049] The signal according to the exemplary non-limiting embodiment is encoded to convey information defining a computer program according to one embodiment of the invention, in this exemplary case the computer program being downloadable from a server forming, for example, part of a cloud service.

[0050] The specific examples provided in the above description should not be construed as limiting the applicability and / or interpretation of the appended claims. The lists and groups of examples provided in the above description are not exhaustive unless expressly stated otherwise.

Claims

1. A system for electrochemical treatment, wherein the system comprises: an electrochemical reactor (101) for containing an electrolytic solution, the electrochemical reactor comprising a plurality of electrodes (102, 103) for guiding an electric current to the electrolytic solution; and a power source (104) configured to supply a controllable DC voltage to the plurality of electrodes of the electrochemical reactor. In the system, the system further comprises: a measuring device (105) configured to generate measurement data indicating the formation of at least one product gas of the system; and a control unit (106) communicably connected to the power source and the measuring device, wherein: i) the control unit is configured to receive an idle command for setting the system to an idle state, and ii) the control unit is configured to reduce the DC voltage in response to a situation where the measurement data indicates the formation of the product gas and the DC voltage exceeds a lower limit of a safe voltage range without degradation of the plurality of electrodes. A system characterized by the above.

2. The system according to claim 1, wherein the control unit comprises a memory configured to store data indicating a Pourbaix diagram of the material of the plurality of electrodes, and the control unit is configured to read out the lower limit of the safe voltage range from the data indicating the Pourbaix diagram.

3. The system according to claim 1, wherein the electrochemical reactor comprises a temperature control device (107) configured to adjust the temperature of the electrolytic solution and the plurality of electrodes, and the control unit is configured to control the temperature control device to change the temperature in response to a situation where the measurement data indicates the formation of the product gas even though the DC voltage is at most the lower limit of the safe voltage range.

4. The system according to claim 1, wherein the electrochemical reactor comprises a pH control device (108) configured to adjust the pH of the electrolytic solution, and the control unit is configured to control the pH control device to change the pH of the electrolytic solution in response to a situation where the measurement data indicates the formation of the product gas even though the DC voltage is at most the lower limit of the safe voltage range.

5. The system according to claim 1, wherein the measuring device (105) comprises at least one pressure sensor (109) configured to detect a gas pressure present in the gas space (110) of the electrochemical reactor, and an output signal of the pressure sensor represents at least a part of the measurement data indicating the formation of the product gas.

6. The system according to claim 1, wherein the measuring device (105) comprises at least one gas mass flow sensor (111) configured to detect a gas mass flow from one or more electrolytic cells of the electrochemical reactor, and an output signal of the at least one mass flow sensor represents at least a part of the measurement data indicating the formation of the product gas.

7. The system according to claim 6, wherein the gas mass flow sensor (111) comprises at least one of a differential pressure flow meter and a thermal mass flow meter.

8. The system according to claim 1, wherein the measuring device (105) comprises a gas component sensor (112) configured to detect a relative content of the product gas in a sample of gas taken from the gas space of the electrochemical reactor, and an output signal of the gas component sensor represents at least a part of the measurement data indicating the formation of the product gas.

9. The system according to claim 8, wherein the gas component sensor (112) comprises at least one of a gas chromatograph and a mass spectrometer.

10. A method for preventing deterioration of electrodes of an electrochemical reactor during an idle state of the electrochemical reactor, the method comprising supplying a controllable DC voltage to a plurality of electrodes of the electrochemical reactor (301), wherein the method further comprises generating measurement data indicating the formation of at least one product gas of the electrochemical reactor (302), and reducing the DC voltage in response to a situation where i) the measurement data indicates the formation of the product gas and ii) the DC voltage exceeds a lower limit of a safe voltage range without deterioration of the plurality of electrodes (303).

11. The method according to claim 10, wherein the electrochemical reactor is one of a reactor for alkaline water electrolysis, a reactor for proton exchange membrane water electrolysis, and a reactor for brine electrolysis.

12. The method according to claim 10, the method further comprising storing data indicating a Pourbaix diagram of a material of the plurality of electrodes, and reading a lower limit of the safe voltage range from the data indicating the Pourbaix diagram.

13. The method according to claim 10, comprising changing the temperature of the plurality of electrodes and the electrolyte of the electrochemical reactor in response to a situation where the measurement signal indicates the formation of a product gas, even if the DC voltage is at its maximum or at the lower limit of the safe voltage range.

14. The method according to any one of claims 10 to 13, comprising changing the pH of the electrolyte of the electrochemical reactor in response to a situation where the measurement signal indicates the formation of a product gas, even if the DC voltage is at its maximum or at the lower limit of the safe voltage range.

15. A computer program for preventing deterioration of a plurality of electrodes of an electrochemical reactor during an idle state of the electrochemical reactor, the computer program comprising computer-executable instructions for controlling a programmable processor to control a power supply to supply a controllable DC voltage to the plurality of electrodes of the electrochemical reactor, wherein the computer program receives measurement data indicating the formation of at least one product gas of the electrochemical reactor, and controls the power supply to reduce the DC voltage in response to a situation where i) the measurement data indicates the formation of the at least one product gas and ii) the DC voltage exceeds the lower limit of a safe voltage range without deterioration of the plurality of electrodes. The computer program is characterized by comprising computer-executable instructions for controlling the programmable processor.

16. A computer program product comprising a non-transitory computer-readable medium encoded by the computer program according to claim 15.

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