System and method for controlling the gas-liquid separators of an electrolyser

Abstract

The invention relates to a system and method for controlling the operation of the gas-liquid separators (GLSan, GLSca) of an electrolyser comprising a stack (10), and anode and cathode gas-liquid separators that separate the electrolyte and the gas along an alkaline solution level (lan, lca), wherein the dioxygen and dihydrogen gases flow from their respective chambers through a gas control valve (V <sb / > an <sb / >, V <sb / > ca <sb / >), such that the control system uses control data representative of the anode gas pressure (p <sb / > an <sb / >), the cathode gas pressure (p <sb / > an <sb / >), the anode alkaline solution level (lan) and the cathode alkaline solution level (lca) to control each of the two gas control valves (V <sb / > an <sb / > , V <sb / > ca <sb / > ), and wherein each of the sensors transmits operating signals to the two gas control valves (Van, Vca) in order to control the gas pressures (p <sb / > an <sb / >, p <sb / > ca <sb / >) and the alkaline solution levels (lan, lca) in the anode gas-liquid separator (GLSan) and the cathode gas-liquid separator (GLSca).

Description

Description Title of the invention: System and method for regulating the gas-liquid separators of an electrolyzer

[0001] TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to a control or monitoring system for regulating the operation of the anode and cathode gas-liquid separators of an alkaline water electrolysis apparatus.

[0003] TECHNICAL BACKGROUND

[0004] The present invention relates to a control or monitoring system for regulating the operation of the anode and cathode gas-liquid separators of an alkaline water electrolysis apparatus.

[0005] According to a well-known electrochemical electrolysis method of the prior art, water is brought into the electrolyzer tank or cell 10 of an electrolysis apparatus in the presence of an electrolytic solution (generally KOH or NaOH) via a specific inlet, this water-electrolyte association being commonly called "lye".

[0006] Said battery 10 is made up of a set of electrolytic cells so that the mixture defined above passes through these cells.

[0007] As can be seen in the attached figures 1 or 2, after this passage combined with the crossing of an electric current through said electrolytic cells, the water is decomposed into gaseous molecules of dihydrogen H2 at the cathode, and into dioxygen O2 at the anode.

[0008] A diaphragm separates the anode from the cathode so that, under normal conditions, the oxygen O2 and hydrogen H2 molecules cannot mix.

[0009] Opposite these electrolytic cells appears a double output: 1) the first is dedicated to the dihydrogen molecules in the presence of the detergent flow; and 2) the second outlet has the same characteristics, but it is dedicated to the oxygen molecules always in the presence of said detergent flow.

[0010] Then, gas-liquid separation is defined as a major step in the alkaline water electrolysis process.

[0011] To carry out said gas-liquid separation, each outlet of the electrolyser stack 10 is directly connected to a gas-liquid separator so that this mixture is introduced instantly into said appropriate gas-liquid separator, and more particularly at the height of the lower part of the lateral face located upstream of said gas-liquid separator.

[0012] Thus, the cathodic gas-liquid separator GLSca is reserved for the separation of the cathodic H2-lye mixture flow, while the anodic gas-liquid separator GLSan is intended for the separation of the cathodic O2-lye mixture flow.

[0013] Throughout the electrolyser installation, each of the GLSca, GLSan gas-liquid separators has two outlets: the first of them for the separated gas while the second is linked to the residual liquid phase.

[0014] Thus, in this configuration, the gas bubbles are evacuated through an orifice located on the upper wall of each of said gas-liquid separators, while the liquid flows through an orifice located on the lower wall of this same gas-liquid separator.

[0015] The two holes appear opposite the inlet hole, through which the gas-lye mixture is introduced.

[0016] To ensure a low differential gas pressure on both sides (anodic and cathodic) of the diaphragm of the electrolyzer stack 10, it is preferable to balance the two gas-liquid separators, both their gas phase pressures p ca and p an and their liquid laundry phase levels l an and Ica-

[0017] In order to balance the two gas-liquid separators GLSan and GLSca, a balancing line 16 is installed between the H2 (cathodic) and O2 (anodic) gas-liquid separators in a “U” configuration located below them.

[0018] Without limitation, on each of the anode and cathode sides, the fluid circulation loop of the lye through the cell 10 and the corresponding gas-liquid separator comprises an associated pump 14an, 14ca; and the electrolysis system also includes a mixer 12 supplied with detergent by these two pumps.

[0019] As illustrated in Figure 1, the first part of a conventional control system 101 can then control a gas control valve V an of the GLSan anode gas-liquid separator to achieve the desired gas pressure at the anode separator, thanks to the gas control valve on the O2 gas flow.

[0020] The second part of the control system 101 also adjusts the exhaust gas flow rate of the cathode gas-liquid separator GLSca by controlling a gas control valve V ca on the H2 gas flow to achieve the same leaching level in the GLSan anode gas-liquid separator and in the GLSca cathode gas-liquid separator.

[0021] As illustrated in the attached figure 2, another usual control system 102 consists of the same gas pressure control logic on the anode side and on the cathode side.

[0022] So, for the cathode side, the gas control valve V ca is used to achieve the same anode and cathode gas pressures p an and p ca in the GLSan and GLSca gas-liquid separators.

[0023] In fact, the detergent level is self-regulated between the two gas-liquid separators GLSan and GLSca through the balancing line 16.

[0024] This control system 101 is then suitable for a mixed lye flow configuration, where the properties of the lye in the anode gas-liquid separator GLSan and in the cathode gas-liquid separator GLSca are the same.

[0025] However, for an unrepresented non-mixed flow configuration, the KOH NAOH concentration may be different on the anodic side and the cathodic side.

[0026] This leads to a difference between the lye densities on the anodic and cathodic sides.

[0027] So, balancing the detergent levels l an and Z ca does not necessarily lead to an equalized charge height between the anodic and cathodic sides.

[0028] This can be very critical, especially during transient operations and the usual control system 101 of Figure 1 can cause different gas pressures at the anode and cathode, which can damage the electrolyzer diaphragm.

[0029] The system according to the invention as illustrated in Figure 3 is identical to that illustrated in Figures 1 or 2, except with respect to its proposed control system 103 which regulates the gas pressures p ca and p an , while keeping the difference between the detergent levels l an and l ca within a certain limit.

[0030] It is possible to regulate the gas pressure p ca in the anode gas-liquid separator GLSan and the gas pressure in the cathode gas-liquid separator GLSca using the control system 102 of Figure 2, but this can lead to a significant difference in the lye levels l an and lca in these GLSan and GLSca gas-liquid separators, which causes the electrolysis process to stop immediately.

[0031] In current industrial alkaline electrolyzers, the control system of gas-liquid separators is based on maintaining the same lye levels in the anodic and cathodic gas-liquid separators at all times, since the gas pressure is the same in both the GLSan and GLSca gas-liquid separators while the lye density could be different on the anodic and cathodic sides.

[0032] However, during transient conditions there is a possibility of having different gas pressures p ca and p an in the GLSan and GLSca anodic and cathodic gas-liquid separators.

[0033] This could lead to a remarkable gas pressure difference on the cathode and anode sides of the electrolysis cell, which would damage the diaphragm(s) and other parts of the electrolyzer stack 10.

[0034] On the other hand, the actual regulation by the system of the anode and cathode gas pressures p ca and p an by anode and cathode gas control valves V an and V ca can lead to a significant difference an - Enter the detergent levels l an and l ca of these gas-liquid separators, which causes the electrolysis process to stop immediately, especially in the case of unmixed lye streams where the properties of the lye in the anodic gas-liquid separator and the lye in the cathodic gas-liquid separator are different

[0035] The object of the invention is to propose a system and a method overcoming the drawbacks of the prior art.

[0036] SUMMARY OF THE INVENTION

[0037] The invention provides a system for regulating the operation of the anodic and cathodic gas-liquid separators of an alkaline water electrolysis apparatus, the apparatus comprising: - an electrolysis tank comprising: - an anode chamber generating oxygen gas; - a cathode chamber generating dihydrogen gas; - an ion-permeable separation membrane separating the anode chamber and the cathode chamber; - an anode gas-liquid separator being connected to the anode chamber and separating an anode electrolyte and oxygen gas along an anode wash level, the oxygen gas flowing out of the anode chamber through an anode oxygen gas control valve; - a cathode gas-liquid separator being connected to the cathode chamber and separating a cathode electrolyte and dihydrogen gas along a cathode wash level, the dihydrogen gas flowing out of the cathode chamber through a cathode dihydrogen gas control valve, said control system comprising: - at least one anode gas pressure sensor; -- at least one cathode gas pressure sensor; -- at least one anode detergent level sensor; -- at least one cathode detergent level sensor; -- and a programmable logic control device or computer, which is connected to each of said two gas control valves and each of said four sensors to send operating signals to the two gas control valves to regulate the gas pressures and lye levels in the anode gas-liquid separator and the cathode gas-liquid separator.

[0038] According to other characteristics of the system according to the invention: - the operation of the two gas control valves is based on a model-based control system; - the system regulates the gas pressures in the anodic and cathodic gas-liquid separators while ensuring that the difference between the lye levels in the gas-liquid separators does not exceed a given threshold value; - the system regulates the lye levels in the anodic and cathodic gas-liquid separators while ensuring that the difference between the lye levels in the gas-liquid separators does not exceed a given threshold value; - in this system: - i) the value of the oxygen gas pressure in the anode gas-liquid separator is continuously measured to compare it with a fixed reference value, or with an optimal transient curve; - ii) the value of the dihydrogen gas pressure in the cathode gas-liquid separator is continuously measured to compare it with the dioxygen gas pressure in the anodic gas-liquid separator; iii) the level of anode liquor is continuously measured to check whether it remains within a safe range; iv) the cathode lye level is continuously measured to compare it with the lye level in the anode gas-liquid separator; v) the oxygen gas control valve is actuated; vi) the hydrogen gas control valve is actuated; - if the measured value of the oxygen gas pressure in the anode gas-liquid separator is different from said fixed reference value, operating signals are sent to the anode exhaust gas check valve and the cathode exhaust gas check valve to operate their opening / closing according to said pattern; - if the measured value of the dihydrogen gas pressure in the cathode gas-liquid separator is different from said fixed reference value, operating signals are sent to the anode gas control valve and the cathode gas control valve to operate their opening / closing according to said pattern; - if the measured value of the anode lye level is not within the safe range, operating signals are sent to the anode gas control valve and the cathode gas control valve to operate their opening / closing according to said pattern; - if the measured value of the cathode lye level is different from said fixed value, operating signals are sent to the anode gas control valve and the cathode gas control valve to operate their opening / closing according to said pattern; - in the nominal operating mode of the apparatus, the position of the anode gas control valve is more or less constant, and in which, in a transient operating mode of the apparatus, the position of the anode gas control valve will be continuously adapted to regulate the oxygen gas pressure and the anode lye pressure; - in the nominal operating mode of the device, the position of the cathode gas control valve is more or less constant, and in which, in a transient operating mode of the device, the position of the valve cathode gas control will be continuously adapted to regulate the hydrogen gas pressure and the cathode wash pressure.

[0039] The invention also provides a method for regulating the operation of the anodic and cathodic gas-liquid separators of an alkaline water electrolysis apparatus, the apparatus comprising: - an electrolysis tank comprising: - an anode chamber generating oxygen gas; - a cathode chamber generating dihydrogen gas; - an ion-permeable separation membrane separating the anode chamber and the cathode chamber; - an anode gas-liquid separator being connected to the anode chamber and separating an anode electrolyte and oxygen gas along an anode wash level, the oxygen gas flowing out of the anode chamber through an anode oxygen gas control valve; - a cathode gas-liquid separator being connected to the cathode chamber and separating a cathode electrolyte and dihydrogen gas along a cathode wash level, the dihydrogen gas flowing out of the cathode chamber through a cathode dihydrogen gas control valve, characterized in that it uses control data representing: -- the anode gas pressure; -- the cathode gas pressure; - the level of anodic lye; - the cathode lye level; to control each of the two said gas control valves and each of the four said sensors to send operating signals to the two gas control valves to regulate the gas pressures and the lye levels in the anode gas-liquid separator and the cathode gas-liquid separator.

[0040] According to other characteristics of the process: - the control of the operation of the two gas control valves is based on a control model for regulating the gas pressures in the anodic and cathodic gas-liquid separators while ensuring that the difference between the lye levels in the gas-liquid separators does not exceed a given threshold value; - the control of the operation of the two gas control valves is based on a control model for regulating the lye levels in the anodic and cathodic gas-liquid separators while ensuring that the difference between the lye levels in the gas-liquid separators does not exceed a given threshold value; - in the process: -- i) the value of the oxygen gas pressure in the anode gas-liquid separator is continuously measured to compare it with a fixed reference value, or with an optimal transient curve; -- ii) the value of the dihydrogen gas pressure in the cathode gas-liquid separator is continuously measured to compare it with the dioxygen gas pressure in the anodic gas-liquid separator; -- iii) the level of anode lye is continuously measured to verify that it remains within a safe range; -- iv) the cathode lye level is continuously measured in order to compare it with the lye level in the anode gas-liquid separator; - v) the oxygen gas control valve is actuated; - vi) the dihydrogen gas control valve is actuated.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] [Fig.1] - Figure 1 is a schematic and partial representation of a first example of an electrolysis system with a control system according to the prior art for regulating gas-liquid separators;

[0043] [Fig.2] - Figure 2 is a schematic and partial representation of a second example of an electrolysis system with a control system according to the prior art for regulating gas-liquid separators;

[0044] [Fig.3] - Figure 3 is a schematic and partial representation of an example of an electrolysis system with a control system according to the invention for regulating the gas-liquid separators;

[0045] [Fig.4] - Figure 4 is a representation of a model used for the regulation of gas-liquid separators.

[0046] DETAILED DESCRIPTION OF THE INVENTION

[0047] In the following description, identical, similar or analogous elements will be designated by the same references.

[0048] According to the invention described below, the regulation of the GLSan and GLSca gas-liquid separators is based on a new control system based on a model 103 which allows the gas control valves V to be correctly controlled an and V ca on the anode and cathode sides to achieve the same gas pressures at the anode and cathode, while keeping the difference an- Brings the detergent levels in the gas-liquid separators within a certain limit, the anodic and cathodic gas-liquid separators GLSan and GLSca, i.e. ensuring that the difference l an - Enter the detergent levels l an and Z ca in gas-liquid separators does not exceed a certain limit or threshold value.

[0049] The invention allows the system to operate safely during all operations, avoiding damage to the electrolyzer stack 10 due to the difference in gas pressures p an - p ca between the anodic side and the cathodic side, while avoiding the stopping of the electrolysis process due to too great a difference. an - Enter the detergent levels.

[0050] This control system can be implemented on mixed and non-mixed flow configurations, i.e. with or without mixer 12.

[0051] In a preferred embodiment, the implementation of the solution is based on a control loop that interacts with six specific components or constituents: - i) at least one anode gas pressure sensor (p_ari); - ii) at least one cathode gas pressure sensor (p_ca); - iii) at least one anode lye level sensor (l_an); - iv) at least one cathodic detergent level sensor (l_ca); - v) at least one anode gas control valve (V_an); - vi) at least one cathode gas control valve (V_ca).

[0052] This control loop is fully automated, meaning that human intervention at the electrolyzer system is no longer required, thereby eliminating a potential hazard associated with said human intervention. Gas control valves V an and V cacould be replaced by back pressure valves, shut-off valves or other types of valves.

[0053] As shown in Figure 3, the arrangement of said components is as follows: - the anode gas pressure sensor providing a representative value of corresponding gas pressure p an and the anode detergent level sensor providing a corresponding representative level value l an are located in the O2 GLSan gas-liquid separator, while the cathode gas pressure sensor and the cathode lye level sensor are located in the H2GLSca gas-liquid separator. The anode gas control valves V an and cathode V ca are downstream of the gas-liquid separators in the gas flow system.

[0054] The operating principle is based on a model-based control system that allows the gas control valves to be correctly and automatically controlled in a closed loop through a programmable logic controller (PLC), so that the PLC is permanently connected to the six components defined above (two gas pressure sensors, two lye level sensors and two gas control valves), while being managed and controlled by a remote human intervention from said electrolyzer system, if necessary.

[0055] Under nominal operating conditions, the control system manipulates the anode gas-liquid separator gas control valve to achieve the desired gas pressure in the anode gas-liquid separator, while manipulating the cathode gas control valve to achieve the same lye level in both the anode and cathode gas-liquid separators.

[0056] However, during transient operations (rapid change in the electrical current density and therefore in the production of hydrogen H2 and oxygen O2 and in the lye flow rates), and / or with an unmixed lye flow configuration (anodic and cathodic flows are separate), this conventional control system may induce a different gas pressure at the anode and cathodic flows, which may damage the diaphragm or other parts of the electrolyzer stack 10.

[0057] The proposed model-based control system regulates the gas pressures in the anode and cathode separators while ensuring that the difference l an - Keeps the detergent levels in the gas-liquid separators within a certain limit, thus avoiding a system shutdown.

[0058] The said model-based control system of an alkaline electrolyzer allows for safe operation under transient conditions.

[0059] In practice, particularly during transient operations of the electrolyser system, a sudden change in electric current (or electric current density) will induce an adaptation of the cathodic H2 and anodic O2 wash flow rates, while the production of dihydrogen H2 and dioxygen O2 bubbles will change accordingly.

[0060] Thus, gas pressures on the cathode and anode gas-liquid separators will vary, a priori, in different ways, as will the lye levels in the cathode and anode gas-liquid separators.

[0061] Then, the model-based control system will adjust the exhaust gas flow rate at the anode and cathode sides in the meantime by controlling the cathode and anode gas control valves through an analysis of the monitored parameters: a) cathode and anode gas pressures; b) and cathodic and anodic wash levels.

[0062] Consequently, through an analytical model, the proposed control system regulates the gas pressures p an and p an in the anodic and cathodic gas-liquid separators while ensuring that the difference an - L ca between the detergent levels in the gas-liquid separators does not exceed a certain limit.

[0063] The said model-based control system will enable better control of electrolyzer performance and more stable operations, which will eventually result in better electrolysis efficiency during transient operations.

[0064] This model-based control system will prevent damage to the diaphragm or other parts of the electrolyzer by controlling the gas pressure difference between the anode and cathode sides.

[0065] The first parameter monitored is the gas pressure value in the GLSan anode gas-liquid separator, which is directly related to the O2 distribution gas pressure (outlet) of the electrolyzer and the production of O2 bubbles.

[0066] This gas pressure is continuously measured to compare it to a fixed reference, or with an optimal transient curve, particularly during system startup and shutdown. If the measured value is different from this, the PLC will send a signal to the anode and cathode gas control valves to activate their opening / closing according to the developed electrolyzer model.

[0067] Thanks to this adjustment, the anode gas pressure in the gas-liquid separator will be continuously adapted to reach its reference or optimal value.

[0068] The second monitored value concerns the gas pressure value in the cathode gas-liquid separator GLSca, which is directly related to the production of H2 bubbles and may involve a gas pressure difference with the anode side, and damage the diaphragm or other parts of the electrolyzer.

[0069] This gas pressure is then continuously measured and compared to the gas pressure in the anode gas-liquid separator. If the measured value is different from this, the PLC will send a signal to the anode and cathode gas control valves to operate their opening / closing according to the developed electrolyzer model.

[0070] With this adjustment, the difference p an - p ca between the anode and cathode gas pressures in the gas-liquid separators will thus be continuously maintained close to zero.

[0071] The third element monitored is the anodic lye level I an , which is directly related to the anode gas pressure in the GLSan gas-liquid separator and the total pressure head on the cathode side, through the balance line 16 of the wash.

[0072] This level of laundry l anis continuously measured to ensure that it remains within a safe range, especially during system startup and shutdown. If the measured value is not within the range, the PLC will send a signal to the anode and cathode gas control valves to operate their opening / closing according to the developed electrolyzer model.

[0073] By this adjustment, at a fixed total pressure height on the cathode side, the anode gas pressure will vary accordingly, involving a change in the anode lye level, through the lye balancing line 16. Thus, the anode lye level l an , in the GLSan gas-liquid separator, will thus be continuously adapted so that it remains within the safe range.

[0074] The fourth element monitored is the cathode wash level l ca, which is directly related to the cathode gas pressure in the gas-liquid separator GLSca and the total pressure head on the anode side, through the balance line 16 of the wash.

[0075] This lye level is then continuously measured and compared to the lye level in the anode gas-liquid separator. If the measured value is different from this, the PLC will send a signal to the anode and cathode gas control valves to operate their opening / closing according to the developed electrolyzer model.

[0076] With this adjustment, at a fixed total pressure height on the anode side, the cathode gas pressure will vary accordingly, involving a change in the cathode wash level l ca , thanks to the 16 balancing line of the detergent. Thus, the difference l an - L cabetween anodic and cathodic wash levels in gas-liquid separators will thus be continuously maintained close to zero.

[0077] The fifth element considered is based on the operation of a gas control valve on the anode gas flow, downstream of the GLSan gas-liquid separator. In this approach, the gas pressure of the anode gas-liquid separator could vary rapidly depending on the transient operation of the electrolyzer, as well as the lye level.

[0078] Thus, in the nominal operation of the electrolyser system, the position of the gas control valve is more or less constant.

[0079] Conversely, in a transient operating mode, the production of oxygen bubbles can occur abruptly, so that the position of the anode gas control valve V an will be continuously adapted to regulate the anode gas pressure and the lye level.

[0080] The sixth element considered is based on the operation of a gas control valve on the cathode gas flow, downstream of the GLSca gas-liquid separator. It will operate in the same way as the gas control valve on the anode side.

[0081] It is also possible to have several electrolysis systems consisting of several electrolyzer stacks 10, gas-liquid separators, controllable lye pumps, gas control valves and power conversion units arranged in series and / or in parallel.

[0082] Each can appear horizontally, vertically, or a combination of both orientations, regardless of the arrangement being studied.

[0083] The same applies to the number of electrolytic cells in said electrolyser stack(s), i.e. the defined approach is independent of the relevant number of electrolytic cells.

[0084] This approach can also be applied to mixed or non-mixed (completely separate) anode and cathode wash circuits, with independent 14an, 14ca pumps or with a mutual pump.

[0085] The invention also applies if the cathode gas pressure (H2) is controlled to reach a set value and the anode gas pressure (O2) is adjusted so as not to have a difference.

[0086] The same applies to the detergent levels. an and l ca , and the anodic lye level Z an could be adjusted to reduce the difference with the cathode wash level l ca which is controlled to reach a set value.

[0087] A preferable embodiment of the invention uses gas pressure and level sensors, but it is also possible to use differential sensors to detect gas pressure levels p an and p ca and the laundry levels l an and l ca .

[0088] It is also possible to use other types of exhaust gas check valves to regulate the system on the anode and cathode flow side, including back pressure valves or gas pressure relief valves.

[0089] The model used as master to control the PLC is preferably based on usual predictive modeling, but can also be based on a simple linear equation model up to a data learning model to be self-adaptive.

[0090] Furthermore, a seventh element could be added in addition, that is, at least one electric current sensor (or electric current density) to allow the control system to be more predictive and react more quickly.

[0091] Example of a monitoring model

[0092] The measured outputs of the alkaline electrolysis process are the anode gas pressure value p^, the cathode gas pressure value p^, and the difference l an - Enters the lye level values ​​in the anode gas-liquid separator GLSan and in the cathode gas-liquid separator GLSca respectively.

[0093] The process inputs include the gas flow rate value Qg n of the anode gas-liquid separator GLSan and the gas flow rate value Q^“ of the cathode gas-liquid separator GLSca.

[0094] Therefore, the input and output vectors can be:

[0095] [Math. 1] Y Y

[0096] The new control system uses a control model to estimate future outputs of the electrolyzer based on current inputs and outputs as shown in Figure 4.

[0097] Using the estimated future outputs, the optimizer finds the best inputs by minimizing the following objective function:

[0098] [Math. 2]

[0099] Or : - Ÿ(k + j\k) is an optimal forecast at level j of the system output; - w(k + j\k) is the future reference trajectory; - Q and R are the weighting factors; - N p and N c are the prediction and control horizons.

[0100] Q, R, N p and N c must be properly tuned to achieve reasonable control performance.

[0101] Once the optimization problem of the above equation is solved, the first element of the input vector is applied to the process and the optimization problem is solved again for subsequent sampling times.

[0102] Six constraints are considered to solve the optimization problem.

[0103] The first and second constraints are to limit the oxygen exhaust gas retaining valves V an and the hydrogen exhaust gas check valves V ca so that the anode gas flow values and cathode Q£ a each remain between a minimum value Q™ in and a maximum value Q ^y™ ax :

[0104] [Math. 3]

[0106] The third constraint concerns the difference in detergent levels. an - L ca .

[0107] The absolute difference an - L ca between the lye level values ​​in the anode gas-liquid separator GLSan and in the cathode gas-liquid separator GLSca respectively must not be higher than a lye level threshold value M max :

[0108] [Math. 5] \ lan lca \ — ^max

[0109] There must be two constraints for the detergent level values ​​l an and l ca to ensure the safe operation of the anode gas-liquid separator GLSan and the cathode gas-liquid separator GLSca, by limiting the lye level values ​​l an and Z ca so that each detergent level value remains between a minimum value r / Lvft and a maximum value :

[0110] [Math. 6] Imin — ^an — ^max

[0111] [Math. 7] Imin — lca — ^max

[0112] The final constraint is to avoid that the absolute difference p an - p ca between the anodic and cathodic gas pressure values ​​is not greater than a gas pressure threshold value ùp max :

[0113] [Math. 8] IPan Pca l — ^Pmax

[0114] Different models can be used as a control model to calculate future outputs.

[0115] As an example, the formulation of the Hammerstein model which is a time-varying nonlinear model is as follows:

[0116] [Math. 9] where aL to a na and b0 to b nb are coefficients of the Hammerstein model and v(k) is a nonlinear function of u(k):

[0117] [Math. 10]

[0118] The parameters of the Hammerstein model and the function f must be identified for a given electrolyzer using available experimental data or simulation results.

Claims

AMENDED CLAIMS received by the International Bureau on January 27, 2025 (27.01.2025) 1. Control system (100) for regulating the operation of the anode and cathode gas-liquid separators (GLSan, GLSca) of an alkaline water electrolysis apparatus, the apparatus comprising: - an electrolysis tank (10) comprising: - an anode chamber generating oxygen gas; - a cathode chamber generating dihydrogen gas; - an ion-permeable separation membrane separating the anode chamber and the cathode chamber; - an anode gas-liquid separator (GLSan) being connected to the anode chamber and separating an anode electrolyte and dioxygen gas along an anode electrolyte level (I an ), the oxygen gas flowing out of the anode chamber through an anode oxygen gas control valve (V an ) ; - a cathode gas-liquid separator (GLSan) being connected to the cathode chamber and separating a cathode electrolyte and dihydrogen gas along a cathode electrolyte level (l ca ), the hydrogen gas flowing out of the cathode chamber through a cathode hydrogen gas control valve (V ca ), said control system comprising: -- at least one anode gas pressure sensor (p an ) ; -- at least one cathode gas pressure sensor (p an ) ; -- at least one anode electrolyte level sensor ( / an ) ; -- at least one cathodic electrolyte level sensor (Z ca ); characterized in that the control system comprises a programmable logic control device (PLC) or a computer, which is connected: - to each of the two said gas control valves (V an , V ca ) ; - and to each of the four said sensors, to send operating signals to the two gas control valves (V an , V ca ) to regulate gas pressures (p an> p ca ) and electrolyte levels (l an , L ca ) in the anode gas-liquid separator (GLSan) and in the cathode gas-liquid separator (GLSca), keeping the difference between electrolyte levels (l an , L ca ) within a certain limit.

2. Control system according to claim 1, wherein the operation of the two gas control valves (V an , V ca ) is based on a model-based control system.

3. A control system according to claim 1 or 2, wherein it regulates the gas pressures (p an , p ca ) in the anodic and cathodic gas-liquid separators (GLSan, GLSca) while ensuring that the difference (l an - Lca ) between electrolyte levels in gas-liquid separators (GLSan, GLSca) does not exceed a given threshold value (A / max ).

4. A control system according to any one of claims 1 to 3, wherein it regulates the electrolyte levels (l an , L ca ) in the anodic and cathodic gas-liquid separators (GLSan, GLSca) while ensuring that the difference (p an - p ca ) between the electrolyte levels in the gas-liquid separators (GLSan, GLSca) does not exceed a given threshold value (at max ).

5. Control system according to any one of claims 1 to 4, wherein: - i) the value of the oxygen gas pressure (p an ) in the anode gas-liquid separator (GLSan) is continuously measured to compare it to a fixed reference value, or to an optimal transient curve; - ii) the value of the dihydrogen gas pressure (pca ) in the cathode gas-liquid separator (GLSca) is continuously measured to compare it with the oxygen gas pressure (p an ) in the anode gas-liquid separator (GLSan); iii) the anode electrolyte level (I an ) is continuously measured to check whether it remains within a safe range; iv) the cathode electrolyte level (l ca ) is continuously measured to compare it to the electrolyte level ( / an ) in the anode gas-liquid separator (GLSan); v) the oxygen gas control valve (V an ) is actuated; vi) the dihydrogen gas control valve (V ca ) is activated.

6. A control system according to claim 5 in combination with claim 2, wherein, if the measured value of the oxygen gas pressure (p an) in the anode gas-liquid separator (GLSan) is different from the said fixed reference value, operating signals are sent to the anode exhaust gas check valve (V an ) and to the cathode exhaust gas check valve (V ca ) to operate their opening / closing according to the said model.

7. A control system according to claim 5 in combination with claim 2, wherein, if the measured value of the dihydrogen gas pressure (p ca ) in the cathode gas-liquid separator (GLSca) is different from the said fixed reference value, operating signals are sent to the anode gas control valve (V an ) and to the cathode gas control valve (V ca ) to operate their opening / closing according to the said model.

8. A control system according to claim 5 in combination with claim 2, wherein, if the measured value of the anodic electrolyte level {ï an ) is not within the safe range, operating signals are sent to the anode gas control valve (V an ) and to the cathode gas control valve (V ca ) to operate their opening / closing according to the said model.

9. A control system according to claim 5 in combination with claim 2, wherein, if the measured value of the cathode electrolyte level (l ca ) is different from said fixed value, operating signals are sent to the anode gas control valve (V an ) and to the cathode gas control valve (Vca) to operate their opening / closing according to said model.

10. A control system according to claim 5 in combination with claim 2, wherein, in the nominal operating mode of the apparatus, the position of the anode gas control valve (V an ) is more or less constant, and in which, in a transient operating mode of the device, the position of the gas control valve anodic (V an ) will be continuously adapted to regulate the oxygen gas pressure and the anodic electrolyte pressure.

11. Control system according to claim 5 in combination with claim 2, wherein, in the nominal operating mode of the apparatus, the position of the cathode gas control valve (V ca ) is more or less constant, and in which, in a transient operating mode of the apparatus, the position of the cathode gas control valve (V ca) will be continuously adapted to regulate the hydrogen gas pressure and the cathode electrolyte pressure.

12. Method for regulating the operation of the anodic and cathodic gas-liquid separators (GLSan, GLSca) of an alkaline water electrolysis apparatus, the apparatus comprising: - an electrolysis tank (10) comprising: - an anode chamber generating oxygen gas; - a cathode chamber generating dihydrogen gas; - an ion-permeable separation membrane separating the anode chamber and the cathode chamber; - an anode gas-liquid separator (GLSan) being connected to the anode chamber and separating an anode electrolyte and oxygen gas along an anode electrolyte level ( / an ), the oxygen gas flowing out of the anode chamber through an anode oxygen gas control valve (V an ) ; - a cathode gas-liquid separator (GLSan) being connected to the cathode chamber and separating a cathode electrolyte and dihydrogen gas along a cathode electrolyte level (l ca ), the hydrogen gas flowing out of the cathode chamber through a cathode hydrogen gas control valve (V ca ), characterized in that it uses control data representing: -- the anode gas pressure (p an ) ; -- the cathode gas pressure (p an ) ; -- the anodic electrolyte level (I an ) ; -- the cathode electrolyte level (l ca ); to control each of the two said gas control valves (Km. Ka) et each of the four said sensors allowing operating signals to be sent to the two gas control valves (V an , V ca ) to regulate gas pressures (p a n,Pca) etelectrolyte levels (l an , ka) in the anodic gas-liquid separator (GLSan) and in the cathodic gas-liquid separator (GLSca), keeping the difference between the electrolyte levels (l an , L ca ) within a certain limit.

13. The method of claim 12, wherein controlling the operation of the two gas control valves (V an , V ca ) is based on a control model for regulating gas pressures (p an , p ca ) in the anodic and cathodic gas-liquid separators (GLSan, GLSca) while ensuring that the difference (l an - L ca ) between electrolyte levels in gas-liquid separators (GLSan, GLSca) does not exceed a given threshold value (A / max ).

14. The method of claim 12, wherein controlling the operation of the two gas control valves (V an , V ca) is based on a control model to regulate electrolyte levels (l an , L ca ) in the anodic and cathodic gas-liquid separators (GLSan, GLSca) while ensuring that the difference (p an - p ca ) between electrolyte levels in gas-liquid separators (GLSan, GLSca) does not exceed a given threshold value (Ap max ).

15. Method according to any one of claims 12 to 14, in which: - i) the value of the oxygen gas pressure (p an ) in the anode gas-liquid separator (GLSan) is continuously measured to compare it to a fixed reference value, or to an optimal transient curve; - ii) the value of the dihydrogen gas pressure (p ca ) in the cathode gas-liquid separator (GLSca) is continuously measured to compare it with the oxygen gas pressure (p an ) in the anode gas-liquid separator (GLSan); - iii) the anodic electrolyte level (l an ) is continuously measured to verify that it remains within a safe range; - iv) the cathodic electrolyte level (l an ) is continuously measured in order to compare it to the electrolyte level (l an ) in the gas-liquid separator anodic (GLSan); - v) the oxygen gas control valve (v an ) is activated; - vi) the dihydrogen gas control valve (V ca ) is activated.

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