Expanding the operating range of an electrolysis system by optimizing the electrolyte flow rate

Abstract

The present invention relates to an electrolysis unit (10) comprising: - a pump (12), - an electrolysis module (14), - a first gas-liquid separator (20) dedicated to separating the dihydrogen-lye mixture, and - a second gas-liquid separator (22) dedicated to separating the dioxygen-lye mixture. The electrolysis unit (10) further comprises: - at least one gas analyzer capable of providing residual dioxygen content information in the first gas-liquid separator (20) or dihydrogen content information in the second gas-liquid separator (22), - a control unit configured to receive and process the residual content information and to provide a lye flow control based on the residual content information, - a lye flow adaptation means configured to receive the lye flow control and to adapt the lye flow rate based on the lye flow control. Figure for the abstract: 1

Description

Title of the invention: Expanding the operating range of an electrolysis system by optimizing the electrolyte flow rate. Technical field of the invention

[0001] The present invention relates to a method for regulating the flow of electrolyte within an electrolysis unit and circulation loop. Technical background

[0002] An electrolysis unit typically comprises an electrolysis module, also called an electrolyzer stack, designed to carry out the reaction producing dihydrogen (H2) at the cathode and dioxygen (O2) at the anode, resulting from the dissociation of water under the effect of injecting a generally direct electric current into an alkaline solution, usually potassium hydroxide (KOH) or sodium hydroxide (NaOH). This water-electrolyte association is commonly called the lye.

[0003] A diaphragm separates the anode from the cathode so that, under normal conditions, the dihydrogen and dioxygen molecules cannot be mixed (except in very small proportions).

[0004] Downstream of the electrolytic module, the gas-liquid separation, between dihydrogen and lye on one side and dioxygen and lye on the other, is defined as a major step in the alkaline electrolysis process of water.

[0005] However, depending on the design of the gas-liquid separators, their efficiency is not total and not all gas bubbles manage to extract themselves from the liquid phase in order to be eliminated through the appropriate orifice in the upper wall of the gas-liquid separator so that residual bubbles in the liquid phase may remain in a significant way.

[0006] However, in the current configuration of the separation system, the two liquid flows exiting the gas-liquid separators are mixed before being reintroduced into the electrolysis module via a closed loop. A single pump circulates the lye within the elements of the electrolysis unit, which are connected by a hydraulic circuit. Consequently, at the inlet of the electrolysis module, the cathodic flow, which will become charged with dihydrogen during electrolysis, already contains dioxygen bubbles dissolved in the lye. Similarly, the anodic flow, which will become charged with dioxygen, already contains dihydrogen bubbles dissolved in the lye. Thus, at the outlet of the electrolysis module and at the inlet of the gas-liquid separators, both flows consist of a lye-dihydrogen-dioxygen mixture. However, the dihydrogen-dioxygen mixture is highly dangerous, which implies that the ratios of residual gas to gases produced by electrolysis must be kept below a threshold specified by standards to reduce the risk of explosion.

[0007] Currently, the market demands the implementation of flexible di-hydrogen and dioxygen production plants that can adapt to intermittent renewable energy sources. This inevitably implies the ability of the electrolysis unit to operate at partial load, rather than just nominal load, which results in a loss of efficiency in the gas-liquid separator. In order to constantly keep the residual gas below the threshold specified by the standards, the current solution consists of limiting the operating range of the electrolysis unit according to the efficiency of the gas-liquid separator, for example, by limiting operation above 40% of the electrical current load while maintaining a constant fluid flow rate.Therefore, regardless of the operating load, the electrolysis steps in the electrolysis module and the gas-liquid separation steps in the gas-liquid separators are carried out at a constant flow rate while the production of dihydrogen and dioxygen varies.

[0008] The limitation of the operation of prior art electrolysis units lies in the fact that the electrolysis unit becomes unusable below a certain charge threshold, that is to say when the electric current falls below a certain value. Summary of the invention

[0009] The invention proposes an electrolysis unit comprising: - a pump, - an electrolysis module comprising electrolytic cells held against each other in a stacking direction, the electrolysis module being traversed by a flow of fluid from the pump and by an electric current, - a first gas-liquid separator dedicated to separating the dihydrogen-lye mixture from the electrolysis module, and - a second gas-liquid separator dedicated to separating the dioxygen-lye mixture from the electrolysis module, the electrolysis unit also comprising: - at least one gas analyzer capable of providing information on the residual oxygen level at the inlet or in the first gas-liquid separator or on the residual hydrogen level at the inlet or in the second gas-liquid separator, - a control unit configured to receive and process residual rate information sent by the gas analyzer and to provide a flow rate command based on the residual rate information, - a means of adapting the flow rate of the lye configured to receive the flow rate command of the lye and to adapt the flow rate of the lye according to the flow rate command of the lye.

[0010] According to other features of the invention:

[0011] - the electrolysis unit comprises two gas analyzers, including: a first gas analyzer at the inlet or in the first gas-liquid separator, capable of providing residual oxygen level information defined by the ratio of oxygen to hydrogen, and a second gas analyzer at the inlet or in the second gas-liquid separator and capable of providing residual dihydrogen rate information defined by the ratio of the quantity of dihydrogen to the quantity of dioxygen;

[0012] - the means for adapting the flow rate is integrated into the pump so that the pump is capable of adapting its operating mode according to the flow control of the fluid;

[0013] - the electrolysis unit further comprises: at least one temperature sensor at the inlet of the first gas-liquid separator or at the inlet of the second gas-liquid separator, and at least one means of regulating the temperature of the fluid flow at the outlet of the first gas-liquid separator or at the outlet of the second gas-liquid separator.

[0014] The invention also proposes a method for adapting the fluid flow within an electrolysis unit comprising: - a pump, - an electrolysis module comprising electrolytic cells held against each other in a stacking direction, the electrolysis module being traversed by a flow of fluid from the pump and by an electric current, - a first gas-liquid separator reserved for separating the dihydrogen-lye mixture from the electrolysis module, and - a second gas-liquid separator dedicated to separating the dioxygen-lye mixture from the electrolysis module, - a control unit capable of determining measured or estimated residual rate information, the residual rate being a residual oxygen level at the inlet or in the first gas-liquid separator or a residual hydrogen level at the inlet or in the second gas-liquid separator, and of providing a flow rate control based on the residual rate information, and - a means of adapting the lye flow rate configured to receive the lye flow rate command and to adapt the lye flow rate according to the lye flow rate command, The process involves the following steps: - determination of measured or estimated residual rate information by the control unit, - determination by the control unit of a flow rate command based on residual rate information, - sending by the control unit a command to adjust the flow rate of the lye by means of adapting the flow rate of the lye.

[0015] According to other features of the invention:

[0016] - the process is such that: If the residual rate is higher than a predetermined threshold value, the flow control tends to reduce the flow rate of the fluid, or if the residual rate is less than a predetermined threshold value, the flow control tends to increase the flow rate of the fluid;

[0017] - the residual rate information is derived from a measurement by: a first gas analyzer at the inlet or in the first gas-liquid separator and capable of providing residual oxygen level information defined by the ratio of the quantity of oxygen to the quantity of hydrogen, or a second gas analyzer at the inlet or in the second gas-liquid separator and capable of providing residual dihydrogen rate information defined by the ratio of the quantity of dihydrogen to the quantity of dihydrogen;

[0018] - the residual rate information is derived from an estimation by the control unit based on a mathematical calculation taking into account the value of the electric current intensity;

[0019] - the residual rate information is derived from an estimation by the control unit based on an experimentally constructed database and establishing a correspondence between the value of the electric current intensity and the residual rate;

[0020] - the electrolysis unit further comprising: at least one temperature sensor at the inlet of the first gas-liquid separator or the second gas-liquid separator, and at least one means of regulating the temperature of the fluid flow at the outlet of the first gas-liquid separator or at the outlet of the second gas-liquid separator, The process also includes temperature regulation of the fluid flow comprising the following steps: reception by the control unit of temperature information from at least one temperature sensor, - determination by the control unit of a temperature command based on temperature information, and temperature control unit sends temperature commands by means of temperature regulation. Brief description of the figures

[0021] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:

[0022] [Fig-1] is a block diagram representing the arrangement and operation of an electrolysis unit according to a first embodiment of the invention;

[0023] [Fig.2] is a schematic representation of a gas-liquid separator showing the incoming and outgoing flow;

[0024] [Fig.3] is a block diagram representing the arrangement and operation of a electrolysis unit according to a second embodiment of the invention;

[0025] [Fig.4] is a block diagram representing the arrangement and operation of a electrolysis unit according to a third embodiment of the invention. Detailed description of the invention

[0026] In the description that follows, identical, similar or analogous elements will be designated by the same reference numerals.

[0027] The invention relates to an electrolysis unit 10 shown in [Fig. 1]. The electrolysis unit 10 comprises an electrolysis module 14 consisting of a stack of electrolytic cells held against each other in a stacking direction. The case described is that of alkaline electrolysis, although the invention may be applicable to other types of electrolysis or electrolyzers.

[0028] The electrolytic cells of the electrolysis module 14 are connected in series electrically and in parallel fluidically. Each electrolytic cell is capable of performing the electrolysis of an electrolytic solution, producing gaseous dihydrogen (H2) and dioxygen (O2). The electrolysis performed is a chemical reaction that dissociates water after injecting a generally direct electric current into an alkaline solution to obtain dihydrogen (H2) and dioxygen (O2). The alkaline solution used is generally potassium hydroxide (KOH) or sodium hydroxide (NaOH). The alkaline solution contains a mixture of water and electrolyte; the electrolysis results from the dissociation of the solutes into ions. The resulting solution is commonly called the lye.

[0029] In operation, the electrolysis module 14 is traversed by a flow of lye F. In order to allow the circulation of the flow of lye F in the electrolysis module 14, the electrolysis unit 10 includes a single pump 12 arranged upstream of the electrolysis module 14.

[0030] The electrolysis module 14 is traversed by an electric current I. In the example, the electric current I comes from an electric generator 32. The electric current I flows through the electrolytic cells and thus enables the electrolysis of the alkaline solution. To allow the generation of an electric current I, a voltage is applied to the terminals of the electrolysis module 14. The resulting electric current I depends on the electrical resistance of the electrolysis module 14, the number of electrolytic cells and the voltage of the cathodic and anodic reactions.

[0031] Under optimal operating conditions, the electrolysis module 14 operates according to theoretically defined reference values, both for the electric current I and for the lye flux F entering the electrolysis module 14. The reference value of the electric current I and the reference value of the lye flux F are defined according to the sizing of the single upstream pump 12 in order to obtain an optimal quantity of dihydrogen and dioxygen gas bubbles within the electrolysis module 14. Thus, the electric current I and the quantity of gas bubbles gravitating around the electrodes correspond to a maximum efficiency.

[0032] The electrolysis module 14 has two hydraulic outlets, including: - a first outlet 16 dedicated to the cathodic flow transporting dihydrogen molecules in the presence of the lye flux F, and - a second outlet 18 reserved for the anodic flow transporting dioxygen molecules always in the presence of the flow of lye F.

[0033] To achieve gas-liquid separation, each hydraulic outlet of the electrolysis module is directly connected to a gas-liquid separator so that the flows of this mixture are introduced instantaneously into the appropriate gas-liquid separators.

[0034] The electrolysis unit 10 comprises two gas-liquid separators, of which: - a first gas-liquid separator 20 dedicated to separating the dihydrogen-lye mixture from the electrolysis module 14 and hydraulically connected to the first outlet 16, and - a second gas-liquid separator 22 dedicated to the separation of the dioxygen-lye mixture from the electrolysis module 14 and hydraulically connected to the second outlet 18.

[0035] An example of a gas-liquid separator is shown in [Fig.2]. The gas (H2 or O2)-liquid mixture is introduced into the dedicated gas-liquid separator through an inlet port 24.

[0036] Conventional gas-liquid separators operate on the principle of Archimedes' thrust which pushes gas bubbles to rise to the gas-liquid interface 26 thanks to the difference in density between the gas bubbles (dihydrogen / dioxygen) and the liquid.

[0037] The gas-liquid separators have two outlets, including: - a first vent 28 located on the upper face of the gas-liquid separator for the separated gas, and - a second evacuation 30 located on a lower face of the gas-liquid separator for the residual liquid phase.

[0038] The residual liquid phases evacuated by the second evacuations 30 of the gas-liquid separators 20, 22 are reinjected into the single pump 12 and mixed in the latter 12 before being rerouted into the electrolysis module 14 at the outlet of pump 12. The fluid thus circulates within a closed circuit.

[0039] Consequently, at the inlet of the electrolysis module 14, the cathodic flow, which will become charged with dihydrogen during electrolysis, already contains dioxygen bubbles dissolved in the lye from the gas-liquid separator 22. Similarly, the anodic flow, which will become charged with dioxygen, already contains dihydrogen bubbles dissolved in the lye from the gas-liquid separator 20. This is why, at the outlet of the electrolysis module 14 and at the inlet of the gas-liquid separators 20 and 22, both flows are composed of a lye-dihydrogen-dioxygen mixture. However, the mixture of dihydrogen and dioxygen gases can be dangerous because it is highly flammable, even explosive.

[0040] Therefore, residual rates are defined for each gas, including: - a residual oxygen level at the inlet or in the first gas-liquid separator 20, the residual oxygen level being defined as the ratio between the quantity of oxygen gas and the quantity of hydrogen gas (O2 / H2), and - a residual level of dihydrogen at the inlet or in the second gas-liquid separator 22, the residual level of dihydrogen being defined as the ratio between the quantity of dihydrogen gas on the quantity of dioxygen gas (H2 / O2).

[0041] According to Archimedes' principle, the larger the hydrogen or oxygen gas bubbles, the more efficient the gas-liquid separation. Similarly, the longer the residence time in the gas-liquid separators, the greater the opportunity for the gas bubbles to rise to the free surface of the liquid, and the more efficient the gas-liquid separation.

[0042] Under nominal operating conditions, gas-liquid separators operate optimally according to reference values ​​for liquid flow rate and gaseous hydrogen and oxygen production. When operating under partial load, i.e., with a current intensity lower than the reference electrical current intensity, the actual hydrogen and oxygen production values ​​will be lower than the nominal values, leading to a reduction in the volume of hydrogen bubbles in the cathodic flow as well as the volume of oxygen in the anodic flow. Consequently, the flow rates of the anodic and cathodic flows are no longer optimal for the operation of the gas-liquid separators, resulting in a decrease in the efficiency of the gas-liquid separators and a possible exceedance of the thresholds specified by the standards for residual gas ratios.Exceeding the residual gas thresholds defined by the standards automatically triggers the shutdown of the electrolysis unit.

[0043] The invention provides a control loop for modulating the fluid flow in order to extend the operating ranges of the electrolysis module 14, particularly for operation at very low partial load, i.e., with an electric current intensity lower than the reference electric current intensity. The invention also makes it possible to increase the efficiency of the electrolysis module 14, particularly at partial load.

[0044] According to features of the invention shown in [Fig. 1] and in order to implement a control loop, the electrolysis unit 10 further comprises: - a first gas analyzer 34 capable of providing information on the residual oxygen level in the first gas-liquid separator 20, - a second gas analyzer 36 capable of providing information on the residual dihydrogen level in the second gas-liquid separator 22, - a control unit 38 configured to receive and process information sent by gas analyzers 34, 36 and to provide a flow control of the fluid, - a means of adapting the flow rate of the lye configured to receive the flow rate command of the lye and to adapt the flow rate of the lye according to the flow rate command of the lye.

[0045] In the example shown, the means for adapting the flow rate of the lye is integrated into the single pump 12 so that the single pump 12 is able to adapt its operating regime according to the flow rate command of the lye.

[0046] In particular, the single pump 12 is a single speed-regulating pump offering an extended flow range and enabling an extended operating range of the electrolysis unit 10.

[0047] Alternatively, the means for adapting the flow rate of the lye can be a flow regulator separate from the pump 12 alone. For example, the flow regulator of the lye can be a diaphragm having an opening of variable cross-section.

[0048] In the example of [Fig.1], the electrolysis unit 10 includes two gas analyzers 34, 36, but it is possible to consider a variant in which the electrolysis unit 10 includes only one gas analyzer from among the two gas analyzers 34 and 36.

[0049] In addition, each gas analyzer 34, 36 can be placed in the corresponding gas-liquid separator 20, 22, in other words on the dedicated gas outlets or at the inlet of the latter 20, 22 or between the outlet of the electrolysis module 14 and the inlet of the gas-liquid separator 20, 22. The gas analyzer 34, 36 can also be placed in another location within the electrolysis unit 10.

[0050] In [Fig. 1], the dashed lines represent information flows. More specifically, widely spaced dashed lines represent measurement information and closely spaced dashed lines represent control information. Solid lines represent present transport pipes for the lye and the double line at the input of the electrolysis module 14 represents the power supply providing the electric current I to the electrolysis module 14.

[0051] The arrangement of the electrolysis unit 10 allows the implementation of a control loop that acts on the flow rate of fluid F through the control of the means for adapting the flow rate of fluid F according to the information provided by: - the first gas analyzer 34, and - the second gas analyzer 36.

[0052] This control loop is fully automated, meaning that human intervention at the electrolysis module 14 is not required, thereby eliminating a potential hazard related to human intervention.

[0053] The control loop is implemented by the control unit 38. The control unit 38 is, for example, a PLC, a computer, a computing unit, or a microcontroller. The control unit 38 receives and processes information from: - of the first gas analyzer 34, and - of the second gas analyzer 36.

[0054] Information can be received continuously by the control unit 38.

[0055] Based on the information received, the control unit 38 determines and sends a flow command intended solely for the pump 12.

[0056] The control loop is implemented by the control unit 38 according to a closed loop which is repeated cyclically with a predetermined periodicity or according to predefined occurrences.

[0057] The control unit 38 is managed and manipulated by remote human intervention from the electrolysis module 14.

[0058] The first element analyzed by the control unit 38 is a residual gas level.

[0059] Thus, when an increase in the residual gas levels of dihydrogen or dioxygen is detected by the control unit 38, a flow control command is sent by the control unit 38 to lower the fluid flow rate. The velocities of the anodic and cathodic flows within the gas-liquid separators 20, 22 are then reduced, which allows: - to optimize the time spent by the flows in the gas-liquid separators 20, 22, and - to promote coalescence, i.e. the merging of gas bubbles and their rise towards the gas-liquid interface of gas-liquid separators 20, 22.

[0060] The efficiency of the gas-liquid separators 20, 22 is thus improved even under partial load, which makes it possible on the one hand to keep the residual gases below the thresholds specified by the standards and on the other hand to extend the operating range of the electrolysis unit 10 towards lower loads.

[0061] In addition to this improved efficiency of the gas-liquid separators 20, 22, the increased density of gas bubbles within the lye increases the electrical resistance of this two-phase mixture, due to the increased electrical resistance of the gases. Thus, the anodic and cathodic flows are more electrically resistive, which reduces leakage currents, commonly known as "shunt currents," between the different electrolytic cells. Consequently, the electrochemical efficiency of the electrolysis module 14 is improved by increasing the Faraday efficiency; in other words, its effective operating range is further extended. It should be noted that the lower and upper limits of operability are also related to thermal aspects, as the lye circuit is responsible for dissipating the heat produced by Joule heating in the electrolyzer stack.

[0062] Of course, monitoring of residual concentration thresholds is maintained. At any given time, residual concentrations are measured using analyzers located in the gas-liquid separators 20, 22 and are systematically compared to reference values ​​linked to the maximum thresholds dictated by the standards. As soon as the measured values ​​approach values ​​exceeding those theoretically permitted, the control unit 38 sends a flow control command to the adjustable lye pump to adjust the lye flow rate entering the electrolysis module 14 in order to maintain residual concentrations below the set thresholds.

[0063] Conversely, when the load on the electrolysis unit 10 increases, i.e., when the intensity of the electric current I increases, the residual rates tend to decrease and fall below the reference values ​​for residual rates. In this case, the control unit 38 sends a flow rate increase command in order to approach the nominal values ​​allowing maximum efficiency for a larger load.

[0064] The process of the invention therefore comprises the following steps: - Determination of residual rate information by control unit 38, - Determination by control unit 38 of a flow rate command based on the residual rate information, - sending by the control unit 38 of a lye flow command by means of lye flow adaptation, in this case to the regulateable pump.

[0065] In particular, the control unit 38 determines the flow rate command of the lye such that: - if the residual rate is higher than a predetermined threshold value, the lye flow control tends to reduce the lye flow rate, and - if the residual rate is less than a predetermined threshold value, the lye flow control tends to increase the lye flow rate.

[0066] According to an effect resulting from the reduction in the flow rate of the lye, the temperature within The electrolysis unit 10 tends to increase in temperature because fewer calories are removed by the lye flow. Therefore, it is necessary to reduce the temperature of the anodic and cathodic flows at the inlet of the electrolysis module 14 in order to maintain a constant average temperature; in other words, the stack outlet temperature must remain constant.

[0067] Under partial load, the average temperature of the lye within the electrolysis module 14 decreases, which also implies a decrease in the electrical conductivity of the lye. The lower conductivity reduces leakage currents and tends to improve efficiency, as described above.

[0068] In order to regulate the temperature of the fluid within the electrolysis unit 10, the electrolysis unit 10 comprises: - a first temperature sensor 40 at the inlet of the first gas-liquid separator 20, which corresponds to the outlet of the electrolyzer stack on the anodic side, - a second temperature sensor 42 at the inlet of the second gas-liquid separator 22, which corresponds to the cathode side outlet of the electrolyzer stack and - a first means of temperature regulation 44 of the fluid flow at the outlet of the first gas-liquid separator 20, and - a second means of temperature regulation 46 of the flow of lye at the outlet of the second gas-liquid separator 22.

[0069] Alternatively, a single temperature sensor can be positioned at any point in the hydraulic circuit of the lye. A single temperature control means can also be used downstream of the single pump 12 and upstream of the electrolysis module 14.

[0070] Each temperature control means 44, 46 is for example a heat exchanger.

[0071] In practice, the lye temperature is continuously measured and compared to a reference temperature. If the measured lye temperature differs from the reference temperature, either because it is higher or lower, the control unit 38 will send a signal to adjust the lye temperature entering the electrolysis module 14 to approach the reference temperature at the output of the electrolysis module 14. By adjusting the lye temperature at the outlet of the gas-liquid separators 20, 22, and therefore at the inlet of the electrolysis module 14, the lye temperature at the output of the electrolysis module 14 will thus be adjusted to reach the reference temperature.

[0072] Temperature regulation comprises the following steps: - reception by control unit 38 of temperature information from a temperature sensor, - determination by control unit 38 of a temperature command based on the temperature information, and - The temperature command is sent by the control unit 38 to the temperature control means corresponding to the temperature sensor. The first temperature sensor 40 corresponds to the first temperature control means 44 and the second temperature sensor 42 corresponds to the second temperature control means 46.

[0073] According to variants of the invention shown in figures 3 and 4, the residual rate information can be obtained from an estimate by the control unit 38 based on a mathematical calculation taking into account the value of the electric current intensity I.

[0074] Indeed, the electrolysis unit 10 can be supplemented by at least one current indicator 48 as shown in [Fig. 3]. The current indicator 48 is, for example, integrated into the electric generator 32. The current intensity information I is sent to the control unit 38 and allows for more predictive control of the electrolysis unit 10 and the effects of a change in current intensity I on the residual gas levels in the gas-liquid separators 20, 22. The adaptation of the fluid flow rate is thus faster as a function of the current intensity I entering the electrolysis module 14, while being controlled by the measurements of the residual gas levels. This measurement of the current intensity I is directly related to the production volume of dihydrogen and dioxygen gas bubbles by Faraday's law, and depends on the operating load.At any given moment, it is possible to measure the value of the electric current intensity I. When this measured value of the electric current intensity I differs from the nominal value during partial load operation, the control unit 38 will send a signal to the pump 12 only to adjust the value of the lye flow entering the electrolysis module 14.

[0075] For example, the residual rate information can be obtained from an estimation by the control unit 38 based on an experimentally constructed database that establishes a correlation between the value of the electric current intensity I and the residual rate. In this case, it is possible to eliminate the gas analyzers 34, 36 as shown in [Fig. 4]. Indeed, through a learning process, the programmable logic unit can use an approach linking these residual rates to variations in the electric current intensity I. Thus, the fluid flow rate is automatically adjusted by the control loop according to changes in the electric current intensity I entering the electrolysis module 14.

[0076] This embodiment of the invention is said to be preferred, but it is entirely conceivable to have several electrolysis units made up of several electrolysis modules, gas-liquid separators, adjustable pumps, cooling systems The electrolytic cells and power conversion units are arranged in series and / or parallel. Each can be horizontal, vertical, or a combination of both orientations, regardless of the arrangement being studied. The same applies to the number of electrolytic cells within the electrolysis module(s); the defined approach is independent of the number of electrolytic cells studied.

[0077] Similarly, this embodiment can be applied to completely separate anodic and cathodic lye circuits, including independent pumps and independent lye cooling systems. At least two temperature sensors will then be required, namely at least one on each lye circuit.

[0078] The invention has several technical advantages which are presented below.

[0079] The invention makes it possible to avoid the shutdown of an electrolysis unit during partial load operation by avoiding reaching the residual rate thresholds.

[0080] The invention also makes it possible to extend the operating range of an electrolysis unit, in particular by allowing settings that permit operation below a load of 40% in electric current intensity.

[0081] The invention makes it possible to reduce the risks associated with the mixing of H2 and O2 gases within an electrolysis unit.

[0082] The invention also makes it possible to improve the efficiency of an electrolysis unit.

[0083] The invention allows for more automated operation of an electrolysis unit and faster adjustments thanks to anticipation of parameter changes.

Claims

Claims

1. Electrolysis unit (10) comprising: - a pump (12), - an electrolysis module (14) comprising electrolytic cells held against each other in a stacking direction, the electrolysis module (14) being crossed by a flow of lye (F) coming from the pump (12) and by an electric current (I), - a first gas-liquid separator (20) dedicated to the separation of the dihydrogen-lye mixture coming from the electrolysis module (14), and - a second gas-liquid separator (22) dedicated to the separation of the dioxygen-lye mixture coming from the electrolysis module (14), the electrolysis unit (10) being characterized in that it further comprises: - at least one gas analyzer capable of providing information on the residual level of dioxygen at the inlet or in the first gas-liquid separator (20) or on the residual level of dihydrogen at the inlet or in the second separator gas-liquid (22),- a control unit configured to receive and process the residual rate information sent by the gas analyzer and to provide a lye flow rate command based on the residual rate information, - a lye flow rate adaptation means configured to receive the lye flow rate command and to adapt the lye flow rate based on the lye flow rate command.,

2. Electrolysis unit (10) according to claim 1, characterized in that it comprises two gas analyzers including: - a first gas analyzer at the inlet or in the first gas-liquid separator (20) and capable of providing information on the residual level of dioxygen defined by the ratio of the quantity of dioxygen to the quantity of dihydrogen, and - a second gas analyzer at the inlet or in the second gas-liquid separator (22) and capable of providing information on the residual level of dihydrogen defined by the ratio of the quantity of dihydrogen to the quantity of dioxygen.

3. Electrolysis unit (10) according to any one of the preceding claims, characterized in that the means for adapting the lye flow rate is integrated in the pump (12) so that the pump (12) is able to adapt its operating speed according to the command of lye flow.

4. Electrolysis unit (10) according to any one of the preceding claims, characterized in that it further comprises: - at least one temperature sensor (40) at the inlet of the first gas-liquid separator (20) or at the inlet of the second gas-liquid separator (22), and - at least one means for regulating the temperature of the lye flow at the outlet of the first gas-liquid separator (20) or at the outlet of the second gas-liquid separator (22).

5. Method for adapting the flow of lye within an electrolysis unit (10) comprising: - a pump (12), - an electrolysis module (14) comprising electrolytic cells held against each other in a stacking direction, the electrolysis module (14) being crossed by a flow of lye (F) coming from the pump (12) and by an electric current (I), - a first gas-liquid separator (20) reserved for the separation of the dihydrogen-lye mixture coming from the electrolysis module (14), and - a second gas-liquid separator (22) reserved for the separation of the dioxygen-lye mixture coming from the electrolysis module (14), - a control unit (38) capable of determining measured or estimated residual rate information, the residual rate being a residual rate of dioxygen at the inlet or in the first gas-liquid separator (20) or a residual rate of dihydrogen at the inlet or in the first gas-liquid separator (20) or a residual rate of dihydrogen at the inlet or in the first gas-liquid separator (20) or a residual rate of dioxygen at the inlet or in the second gas-liquid separator (2 ... the inlet or in the second gas-liquid separator (22),and providing a lye flow rate command as a function of the residual rate information, and - a lye flow rate adaptation means configured to receive the lye flow rate command and to adapt the lye flow rate as a function of the lye flow rate command, the method being characterized in that it comprises the following steps: - determination of measured or estimated residual rate information by the control unit (38), - determination by the control unit (38) of a lye flow rate command as a function of the residual rate information, - sending by the control unit (38) of a lye flow rate command to the lye flow rate adaptation means.,

6. Method according to claim 5, characterized in that: - if the residual rate is greater than a predetermined threshold value, the flow control tends to reduce the lye flow rate, or - if the residual rate is below a predetermined threshold value, the flow control tends to increase the lye flow rate.

7. Method according to any one of claims 5 or 6, characterized in that the residual rate information comes from a measurement by: - ​​a first gas analyzer at the inlet or in the first gas-liquid separator (20) and capable of providing information on the residual rate of dioxygen defined by the ratio of the quantity of dioxygen to the quantity of dihydrogen, or - a second gas analyzer at the inlet or in the second gas-liquid separator (22) and capable of providing information on the residual rate of dihydrogen defined by the ratio of the quantity of dihydrogen to the quantity of dihydrogen.

8. Method according to any one of claims 5 or 6, characterized in that the residual rate information comes from an estimate by the control unit (38) based on a mathematical calculation taking into account the value of the electric current intensity (I).

9. Method according to any one of claims 5 or 6, characterized in that the residual rate information comes from an estimate by the control unit (38) based on a database created experimentally and establishing a correspondence between the value of the electric current intensity (I) and the residual rate.

10. Method according to any one of claims 5 to 9, characterized in that the electrolysis unit (10) further comprising: - at least one temperature sensor at the inlet of the first gas-liquid separator (20) or of the second gas-liquid separator (22), and - at least one means for regulating the temperature of the lye flow at the outlet of the first gas-liquid separator (20) or at the outlet of the second gas-liquid separator (22), the method further comprises a temperature regulation of the lye flow comprising the following steps: - reception by the control unit (38) of temperature information from the at least one temperature sensor, - determination by the control unit (38) of a temperature command as a function of the temperature information, and - sending by the control unit (38) of the temperature command by means of temperature regulation.

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