Method for adjusting flow of lye in electrolysis unit and associated electrolysis unit

Abstract

The invention relates to a method for regulating the flow of lye in an electrolysis unit and to an associated electrolysis unit (10) comprising a pump (12) and a module (14) comprising electrolytic cells held against each other in a stacking direction, through which module (14) an electric current (I) and a flow (F) of lye from the pump (12) flow, the electrolysis unit (10) further comprising:-a unit (16) for measuring the electric current; -a flow regulator (18) placed downstream of the pump (12) and upstream of the module (14); -a unit (20) for measuring the flow rate of the lye, capable of measuring the flow rate (F) of the lye flowing through the module (14); -a gas sensor (22) placed downstream of the module and capable of measuring an amount of gas; and-a control unit (24) connected to the pump (12), to the regulator (18), to the unit (16) for measuring the measured value of the current, to the unit (20) for measuring the flow rate of the lye and to the gas sensor (22).

Description

Technical Field

[0001] The invention relates to a method for regulating the flow of alkaline solution in an electrolysis unit and a related electrolysis unit. Background Art

[0002] In a broad sense, the architecture of an electrolyzer stack (also called an electrolysis module) generally consists of electrolytic cell blocks and seals, which are stacked in series from an electrical point of view and in parallel from a fluidic point of view. Each electrolytic cell is intended to perform electrolysis of an electrolyte. In general, the purpose of an electrolyzer stack is to promote the reaction of water dissociation to produce gaseous dihydrogen (H2) and dioxygen (O2) after direct current is injected into an alkaline solution (usually potassium hydroxide (KOH) or sodium hydroxide (NaOH)). This water-electrolyte combination is commonly referred to as lye.

[0003] Each electrolytic cell (which can be thought of as primarily metallic and conductive components) typically consists of two bipolar plates, two layers of flow field material sandwiched between the two bipolar plates, and two electrodes (i.e., an anode and a cathode) sandwiched between the two layers of flow field material.

[0004] The electrodes are usually formed of metal mesh or grids or plates and are arranged to be separated by diaphragms to ensure:

[0005] - electrical insulation of the electrodes,

[0006] - separation of gases, and

[0007] -Ionic conduction within the electrolytic cell.

[0008] The flow field material layer has two functions:

[0009] i) provide a low resistivity metal path between each bipolar plate and the associated electrode, and

[0010] ii) Allowing adequate flow of electrolyte to cool the electrolyser stack and transport the gases produced.

[0011] Opposite these cells there are two outlets:

[0012] i) a first outlet dedicated to dihydrogen molecules in the presence of a caustic soda stream, and

[0013] ii) A second outlet, which has the same characteristics but is also reserved for dioxygen molecules in the presence of alkali.

[0014] Downstream of the electrolysis cell, gas-liquid separation is defined as the main step in the alkaline electrolysis of water.

[0015] The electrolyte present in each electrolytic cell and the gases produced by electrolysis must not leak outside the cell from the edges of the diaphragm and must flow only through the lines dedicated to them. Each line is dedicated to a single electrolyte or to an electrolyte mixed with one of the gases. The two gases cannot mix with each other.

[0016] Thus, if a leak is detected, be it a leak of the electrolyte or a leak of the gas produced by electrolysis or a leak of any other substance, the electrolyser stack can be stopped from continuous operation.

[0017] When a leak occurs, various problems arise that negatively impact the environment as well as the safety of operators. The severity of a leak is variable and can reach extremely high values ​​associated with irreversible consequences.

[0018] One possible cause of gas leakage is the accumulation of bubbles around the electrodes. Within the electrolytic cells of an operating electrolyzer stack, when the current increases significantly, the production of dihydrogen and dioxygen increases, potentially leading to bubble accumulation around the electrodes. Bubble accumulation hinders the smooth flow of bubbles in the dedicated pipelines, as accumulated bubbles are less likely to flow and reach the gas-liquid separator. This poor bubble flow creates the risk of leakage and even explosion.

[0019] Furthermore, due to the accumulation of gas bubbles, the flow of charge carriers within the electrolytic cells of the electrolytic cell stack is drastically slowed down, which results in an increase in the resistance of the electrolytic cells. This increase in the resistance of the electrolytic cells results in a deterioration in the efficiency of the electrolytic cell stack. Summary of the Invention

[0020] The present invention provides an electrolysis unit comprising a pump and a module, the module comprising electrolysis cells held against each other in a stacking direction, through which current and a stream of alkali solution from the pump flow, the electrolysis unit further comprising:

[0021] - a unit for measuring current,

[0022] - a flow regulator placed downstream of the pump and upstream of the module,

[0023] - a unit for measuring the flow of alkali solution, capable of measuring the flow of alkali solution passing through the module,

[0024] a gas sensor placed downstream of the module and capable of measuring the amount of gas, and

[0025] a control unit connected to the pump, the regulator, the unit for measuring the current, the unit for measuring the lye flow rate and the gas sensor.

[0026] The expression "measuring the current" is understood to mean the measurement of the current (in amperes) flowing through the module.

[0027] The expression "electrical current" is understood to mean an electric current resulting from a flow of electric charges.

[0028] The term "flow rate" is understood to mean the amount of fluid that flows through a module in a given time. Flow rate is equivalent to flow rate, which is expressed in m 3 The unit is / s.

[0029] The present invention also provides a method for regulating the flow of alkali solution in an electrolysis cell according to the present invention, the method comprising the step of optimizing the current, wherein:

[0030] the control unit determines a measured value of the current from the information provided by the unit for measuring the current,

[0031] - the control unit compares the measured value of the current with a reference current measured value,

[0032] If the measured value of the current is less than the reference current measured value, the control unit sends a command to the flow regulator to increase the lye flow rate.

[0033] Other variants of the method according to the invention:

[0034] - The method comprises the step of configuring the current, wherein:

[0035] the control unit determines a measured value of the current from the information provided by the unit for measuring the current,

[0036] - the control unit compares the measured value of the current with a reference current measured value,

[0037] If the measured value of the current is greater than the reference current measured value, the control unit sends a command to the flow regulator to reduce the lye flow rate;

[0038] - The method comprises the step of configuring the amount of bubbles, wherein:

[0039] the control unit determines the amount of lye based on the information provided by the unit for measuring the lye flow rate,

[0040] - the control unit determines the amount of gas bubbles based on the information provided by the gas sensor,

[0041] - The control unit calculates a ratio which is equal to the amount of bubbles divided by the amount of lye,

[0042] - the control unit compares the ratio with a reference ratio,

[0043] - if the ratio is greater than the reference ratio, the control unit sends a command to the flow regulator to increase the lye flow rate;

[0044] - The method comprises the step of increasing the rotational speed of the pump, wherein:

[0045] the control unit determines the value of the lye flow rate, ie the flow rate through the module, from the information provided by the unit for measuring the lye flow rate,

[0046] - the control unit compares the lye flow rate to a high level and if the lye flow rate is substantially equal to or greater than the high level, then:

[0047] the control unit determines a measured value of the current from the information provided by the unit for measuring the current,

[0048] - the control unit compares the measured value of the current with a threshold current measurement value,

[0049] - if the measured value of the current is substantially equal to or greater than the threshold current measured value, the control unit sends a flow increase command to the pump to increase the lye flow rate;

[0050] - The method comprises the step of reducing the rotational speed of the pump, wherein:

[0051] the control unit determines the value of the lye flow rate, ie the flow rate through the module, from the information provided by the unit for measuring the lye flow rate,

[0052] - the control unit compares the lye flow rate with a low level and if the lye flow rate is substantially equal to or less than the low level, then:

[0053] the control unit determines a measured value of the current from the information provided by the unit for measuring the current,

[0054] - the control unit compares the measured value of the current with a threshold current measurement value,

[0055] - if the measured value of the current is substantially equal to or less than the threshold current measured value, the control unit sends a flow reduction command to the pump in order to reduce the lye flow;

[0056] - the control unit comprises a set of N predetermined incremental command values ​​for the pump corresponding to N operating levels;

[0057] - the reference current measurement values ​​and / or the reference ratio are defined for each operating level of the pump;

[0058] When the control unit sends a new command to the pump allowing a change in the speed of rotation of the pump, the control unit then sends a full opening command to the flow regulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Other features and advantages of the present invention will become more apparent by reading the following detailed description. For a better understanding, these detailed descriptions should be read with reference to the accompanying drawings, in which:

[0060] [ Figure 1 ] is a block diagram showing the layout and operation of an electrolysis cell according to the present invention. DETAILED DESCRIPTION

[0061] The present invention relates to an electrolysis unit 10 (in Figure 1 ). The electrolysis unit 10 comprises a module 14 (also called an electrolysis cell stack) comprising a stack of electrolysis cells held against each other in a stacking direction.

[0062] The electrolytic cells of module 14 are connected in series from an electrical point of view and in parallel from a fluid point of view. Each electrolytic cell is capable of performing electrolysis of an electrolyte, thereby producing gaseous dihydrogen (H2) and dioxygen (O2). The electrolysis performed is a chemical reaction that dissociates water to obtain dihydrogen (H2) and dioxygen (O2) after direct current is injected into an alkaline solution. The alkaline solution used is typically potassium hydroxide (KOH) or sodium hydroxide (NaOH). The alkaline solution comprises a combination of water and an electrolyte, and electrolysis is produced by the dissociation of a solute into ions. The solution obtained is commonly referred to as lye.

[0063] In operation, a caustic soda stream F flows through the module 14. To allow the caustic soda stream F to flow through the module 14, the electrolysis unit 10 includes a pump 12. The caustic soda stream F leaving the module 14 is typically sent to a gas-liquid separator and then to a filter to remove impurities (particularly metallic impurities) before being reinjected into the module 14 via the pump 12. The caustic soda thus circulates in a closed loop.

[0064] A current I flows through the module 14. This current flows through the electrolytic cell and thus allows the electrolysis of the alkaline solution to proceed. To generate the current I, a voltage is applied across the module 14. The generated current I depends on the resistance of the module 14.

[0065] Under optimal operating conditions, the module 14 operates at theoretically defined reference values ​​for both the current I and the lye flow rate F entering the module 14. The reference current value I0 and the reference lye flow rate F0 are defined based on the size of the upstream pump 12 in order to obtain the optimal amount of bubbles B within the module 14. Therefore, the current I and the amount of bubbles B attracted around the electrodes correspond to maximum efficiency.

[0066] In practice, during actual operation of the module 14 , the actual measured values ​​of the current I and the lye flow rate F may be smaller or larger than the corresponding reference values ​​I0 and F0 , which results in a decrease in the efficiency of the module 14 .

[0067] The invention provides a control loop for regulating the lye flow rate in order to avoid significant deviations from reference measurement values ​​associated with the current I and / or the lye flow rate F inside the module 14 .

[0068] According to a particularity of the invention and in order to implement the control circuit, the electrolysis unit 10 further comprises:

[0069] a unit 16 for measuring the measured value of the current, which is integrated into the power supply circuit of the module 14 ,

[0070] a flow regulator 18 , which is fluidically connected to the pump 12 and the module 14 and is placed downstream of the pump 12 and upstream of the module 14 ,

[0071] a unit 20 for measuring the flow of alkali solution, capable of measuring the flow rate F of the alkali solution flowing through the module 14,

[0072] a gas sensor 22 placed downstream of the module 14 and capable of measuring the amount of gas, and

[0073] A control unit 24 connected to the pump 12 , the regulator 18 , the unit 16 for measuring the measured value of the electric current, the unit 20 for measuring the lye flow rate and the gas sensor 22 .

[0074] exist Figure 1 In FIG, dot-dashed lines represent electrical connections, solid lines represent pipes for conveying lye, and short dashed lines leaving the module outlet represent pipes for conveying lye laden with gas.

[0075] The layout of the electrolysis cell 10 allows the implementation of a control circuit that acts on the regulation of the lye flow F through the flow regulator 18 and the commands of the pump 12 according to the information provided by:

[0076] - a unit 16 for measuring current,

[0077] - a unit 20 for measuring the lye flow rate, and

[0078] -Gas sensor 22.

[0079] The control loop is fully automated, which means that manual intervention in the module 14 is no longer necessary, thereby eliminating the potential hazards associated with manual intervention.

[0080] The control loop is implemented by a control unit 24. The control unit 24 is, for example, a computer, a computing unit or a microcontroller. The control unit 24 receives and processes information from:

[0081] - a unit 16 for measuring current,

[0082] - a unit 20 for measuring the lye flow rate, and

[0083] -Gas sensor 22.

[0084] Information may be received continuously by the control unit 24 .

[0085] Based on the information received, the control unit 24 determines and sends commands intended for the flow regulator 18 and the pump 12 .

[0086] The control loop is implemented by the control unit 24 in a closed loop that is cyclically repeated with a predetermined periodicity or a predefined number of occurrences.

[0087] The control unit 24 is managed and operated by human intervention remote from the module 14 .

[0088] The first factor analyzed by the control unit 24 is the current I in the module 14, which is closely related to the lye flow F entering the module 14. At any given time, the current I entering the module 14 can be measured by means of the unit 16 for measuring the current, in order to systematically compare the measured value of the current I with a reference measured value, called the reference current I0.

[0089] If the measured value of the current I is equal to or greater than the measured value of the reference current measurement value I0, the control unit 24 will send a signal to the regulator 18 of the caustic soda flow rate to adjust the value of the caustic soda flow rate F entering the module 14 so that the reference current measurement value I0 is no longer exceeded. By means of this adjustment of the value of the caustic soda flow rate F entering the module 14 by the regulator 18 of the caustic soda flow rate, located upstream of the module 14, the measured value of the current I in the electrolytic cell of the module 14 will thus be adjusted so that it reaches the reference current measurement value I0.

[0090] Therefore, based on the measured value of the current I, the method of the invention comprises an optimization step E1 in which:

[0091] - the control unit 24 determines the measured value of the current I from the information provided by the unit 16 for measuring the current,

[0092] - the control unit 24 compares the measured value of the current I with the reference current measurement value I0,

[0093] If the measured value of the current I is less than the reference current measurement value I0, the control unit 24 sends a command to the flow regulator 18 to increase the lye flow F.

[0094] As a variant or in addition, according to the measured value of the current I, the method comprises a configuration step E2 in which:

[0095] - the control unit 24 determines the measured value of the current I from the information provided by the unit 16 for measuring the measured value of the current,

[0096] - the control unit 24 compares the measured value of the current I with the reference current measurement value I0,

[0097] If the measured value of the current I is greater than the reference current measurement value I0, the control unit 24 sends a command to the flow regulator 18 to reduce the lye flow F.

[0098] Steps E1 and E2 can be combined into a single step where:

[0099] - the control unit 24 determines the measured value of the current I from the information provided by the unit 16 for measuring the measured value of the current,

[0100] - the control unit 24 compares the measured value of the current I with the reference current measurement value I0,

[0101] - If the measured value of the current I is greater than the reference current measurement value I0, the control unit 24 sends a command to the flow regulator 18 to reduce the lye flow F, and

[0102] If the measured value of the current I is less than the reference current measurement value I0, the control unit 24 sends a command to the flow regulator 18 to increase the lye flow F.

[0103] When steps E1 and E2 are not combined, within step E1 , if the measured value of the current I is not greater than the reference current measurement value I0 , step E1 ends and a new subsequent iteration can be performed.

[0104] Similarly, when steps E1 and E2 are not combined, within step E2 , if the measured value of the current I is not less than the reference current measurement value I0 , step E2 ends and a new subsequent iteration can be performed.

[0105] The measured value of current I is affected by the accumulation of bubbles B, which hinders and slows the flow of charge carriers within module 14. This slowing of the charge carriers increases the resistance of module 14. This increased resistance of module 14 leads to a decrease in the efficiency of electrolysis cell 10. In particular, for a given voltage applied across the edges of module 14 and for a given contact area between the electrodes and the electrolyte, the measured value of current I decreases as the resistance increases. Therefore, increasing the lye flow rate F allows bubbles B to flow better into the gas-liquid separation unit, thereby reducing the resistance of module 14 and, consequently, increasing the measured value of current I. This explains why, when the measured value of current I is less than the reference current measurement value I0, increasing the lye flow rate F allows the measured value of current I to be readjusted by increasing its value.

[0106] The second factor analyzed by the control unit 24 is the value of the lye flow rate F entering the module 14, which is directly related to the amount of gas bubbles B present around the electrodes in the electrolytic cell of the module 14, this amount of gas bubbles B being preferably measured downstream of the module 14. In order to maximize the efficiency of the electrolysis cell 10, the ratio R between the amount of gas bubbles B leaving the electrolytic cell and the amount of lye L must in all cases be equal to a reference ratio R0. For this reason, a gas sensor 22 placed downstream of the module 14 is used to measure the amount of gas bubbles B, so that the control unit 24 can then calculate said ratio R between the amount of gas bubbles B and the amount of lye L.

[0107] The bubble amount B is defined as, for example, the number of moles of gas present in all bubbles B flowing through the gas sensor 22 within a predetermined time range.

[0108] For example, the amount of lye L is defined as:

[0109] - the number of moles of solute entering the module 14 within a predetermined time frame, or

[0110] - the volume of lye entering the module 14 within a predetermined timeframe, or

[0111] - The quality of the lye entering the module 14 within a predetermined time frame.

[0112] The method then comprises a step E3 of configuring the bubble volume B, wherein:

[0113] - the control unit 24 determines the amount of lye L from the information provided by the unit 20 for measuring the lye flow rate,

[0114] - the control unit 24 determines the amount of bubbles B based on the information provided by the gas sensor 22,

[0115] - the control unit 24 calculates the ratio R, which is equal to the amount of bubbles B divided by the amount of lye L: R=B / L,

[0116] - the control unit 24 compares the ratio R with a reference ratio R0,

[0117] If the ratio R is greater than the reference ratio R0, the control unit 24 sends a command to the flow regulator 18 to increase the lye flow F.

[0118] Specifically, an increase in the alkali flow rate F reduces the ratio R via a dual effect:

[0119] - On the one hand, since the ratio R=B / L is inversely proportional to the amount of lye L and therefore to the lye flow F, this ratio decreases when the lye flow increases,

[0120] On the other hand, an increase in the alkali solution flow rate F causes the bubbles B to be brought toward the gas-liquid separation unit and thus reduces the bubble amount B and thus reduces the ratio R proportional to the bubble amount B.

[0121] Step E3 thus makes it possible to get closer to or even equal the value of the reference ratio R0 .

[0122] The third factor analyzed by the control unit 24 is the value of the lye flow F in order to regulate the operation of the pump 12 for producing the lye flow, which is also located upstream of the module 14 .

[0123] Two cases were studied, namely:

[0124] i) In the first case, the lye flow F is equal to the high level Fmax, and the measured value of the current I is greater than the threshold current measurement value I relative to the high level max ,as well as

[0125] ii) In the second case, the lye flow rate F is equal to the low level Fmin, and the measured value of the current I is less than the threshold current value I relative to the low level min The measured value of the measuring current I makes it possible to determine whether the first case i) or the second case ii) prevails.

[0126] The high level Fmax corresponds to the upper limit of the alkali solution flow rate.

[0127] The low level Fmin corresponds to the lower limit of the alkali solution flow rate.

[0128] It is also possible that neither the first nor the second case is advantageous, for example:

[0129] - When the alkali solution flow rate F is less than the high level or greater than the low level, or

[0130] - when the measured value of the current I is substantially equal to the reference current measured value I0 within the tolerance margin, or

[0131] - When the lye flow F is equal to the high level but the measured value of the current I is less than the threshold current measurement value I relative to the high levelmax When, or

[0132] - When the lye flow F is equal to the low level but the measured value of the current I is greater than the threshold current measurement value I relative to the low level min hour.

[0133] When the second case ii) prevails, this is because the measured value of the current I is low and the generation of bubbles B is also low. Therefore, for a given degree of generation of bubbles B, the values ​​of the pump rotation speed and the lye flow rate F can be low.

[0134] When the first case i) prevails, in the presence of a high measured value of the current I, it is preferred to drive the pump 12 at a higher rotational speed to increase the magnitude of the lye flow F. Specifically, such a high measured value of the current I can lead to a significant generation of bubbles B and thus increase the risk of bubbles B accumulating within the module 14. For this reason, the lye flow F entering the module 14 must be increased to facilitate the removal of the bubbles B.

[0135] In both specific cases, the ratio R between the amount of gas bubbles B and the amount of lye L leaving the module 14 can still be measured by the control unit 24 as described above, so that the value of the ratio R is still sent to the control unit 24. The control unit 24 can also determine the command for the pump 12 based on the value of the ratio R to configure the rotation speed of the pump 12, thereby adjusting the value of the lye flow rate F and optimizing the flow rate of gas bubbles B inside the module 14.

[0136] Therefore, in order to manage the first case i), the method of the invention comprises a step E4 of increasing the rotational speed of the pump, wherein:

[0137] - the control unit 24 determines the value of the lye flow F, ie the flow through the module 14 , from the information provided by the unit 20 for measuring the lye flow,

[0138] - The control unit 24 compares the lye flow F with the upper level Fmax.

[0139] If the lye flow F is less than the upper level Fmax, step E4 ends and a new subsequent iteration can be carried out.

[0140] If the alkali solution flow rate F is substantially equal to or greater than the high level Fmax, then:

[0141] - the control unit 24 determines the measured value of the current I from the information provided by the unit 16 for measuring the current,

[0142] - The control unit 24 compares the measured value of the current I with the threshold current measurement value I relative to the high level max Make a comparison.

[0143] If the measured value of the current I is less than the threshold current measurement value I max , then step E4 ends and a new subsequent iteration can be performed.

[0144] If the measured value of the current I is substantially equal to or greater than the threshold current measurement value I max , the control unit sends a flow increase command to the pump to increase the alkali solution flow F.

[0145] In order to manage the second situation ii), the method of the invention comprises a step E5 of reducing the rotational speed of the pump, wherein:

[0146] - the control unit 24 determines the value of the lye flow F, ie the flow through the module 14 , from the information provided by the unit 20 for measuring the lye flow,

[0147] - The control unit 24 compares the lye flow F with the low level Fmin.

[0148] If the lye flow F is greater than the low level Fmin, step E5 ends and a new subsequent iteration can be carried out.

[0149] On the contrary, if the alkali solution flow F is substantially equal to or less than the low level Fmin, then:

[0150] - the control unit 24 determines the measured value of the current I from the information provided by the unit 16 for measuring the current,

[0151] - The control unit 24 compares the measured value of the current I with the measured value of the current I relative to the low level threshold current value I min Make a comparison.

[0152] If the measured value of the current I is greater than the threshold current measurement value I min , then step E5 ends and a new subsequent iteration can be performed.

[0153] If the measured value of the current I is substantially equal to or less than the threshold current measurement value I min , the control unit 24 sends a flow reduction command to the pump 12 to reduce the alkali solution flow rate F.

[0154] Equal or substantially equal refers to a comparison that may include a tolerance margin (eg, + / - 10%).

[0155] The control unit 24 may use commands from a predetermined database table in order to send commands to the pump 12. For example, the control unit 24 may include in the database a set of N predetermined incremental command values ​​for the pump 12 corresponding to N operating levels.

[0156] At any given time, the control unit 24 is able to determine which level the pump is operating in. If the control unit 24 needs to send a command to the pump 12 to decrease the flow rate, the control unit 24 sends a command corresponding to the level below the current level. If the control unit 24 needs to send a command to the pump 12 to increase the flow rate, the control unit 24 sends a command corresponding to the level above the current level.

[0157] A reference current measurement value I0 and optionally a reference ratio R0 are defined for each operating level of the pump 12. In particular, a high lye flow rate is suitable for a high current measurement value.

[0158] When the control unit 24 sends a new command to the pump 12 allowing a change in the rotational speed of the pump 12, the control unit 24 then sends a full opening command to the flow regulator 18. This allows the entire caustic soda flow pumped by the pump 12 to enter the module 14 during the level change. The regulation by means of the flow regulator 18 can then be implemented according to the regulation method described above.

[0159] This embodiment of the invention is considered preferred, but multiple modules 14 arranged in series and / or in parallel are entirely conceivable. Each module 14 can be arranged horizontally, vertically, or in a combination of these two orientations, regardless of the layout being considered. The same applies to the number of electrolytic cells within one or more modules 14. The defined method is independent of the number of electrolytic cells being considered.

[0160] In the present invention described above, after configuring the flow rate F of the alkali solution entering the module 14, the bubbles G accumulated around the electrodes in the module 14 will more easily move toward the gas-liquid separator. Therefore, the efficiency of the electrolysis unit 10 will be improved. Claims (as amended under Article 19) 1. A method for regulating the flow rate (F) of an alkali solution in an electrolysis unit (10), the electrolysis unit comprising a pump (12) and a module (14), the module comprising electrolysis cells held against each other in a stacking direction, an electric current (I) and a flow (F) of alkali solution from the pump (12) flowing through the module (14), the electrolysis unit (10) comprising: - a unit (16) for measuring current, - a flow regulator (18) placed downstream of the pump (12) and upstream of the module (14), - a unit (20) for measuring the flow of alkali solution, capable of measuring the flow rate (F) of alkali solution flowing through said module (14), a gas sensor (22) placed downstream of the module and capable of measuring the amount of gas, and a control unit (24) connected to the pump (12), the regulator (18), the unit for measuring the measured value of the electric current (16), the unit for measuring the lye flow rate (20) and the gas sensor (22), According to the measured value of the electric current (I), the method for regulating the flow rate (F) of the alkali solution comprises an optimization step (E1), wherein: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the measured value of the current, - the control unit (24) compares the measured value of the current (I) with a reference current measurement value (I0), - in the event that the measured value of the current (I) is less than the reference current measured value (I0), the control unit (24) sends a command to the flow regulator (18) to increase the alkali solution flow rate (F), And the method for regulating the flow rate of alkali solution includes a step (E3) of configuring the amount of bubbles, wherein: - the control unit (24) determines the amount of alkali solution (L) based on the information provided by the unit (20) for measuring the flow rate of alkali solution, - the control unit (24) determines the amount of bubbles (B) based on the information provided by the gas sensor (22), - the control unit (24) calculates a ratio (R) equal to the amount of bubbles (B) divided by the amount of lye (L): R=B / L, - said control unit (24) compares said ratio (R) with a reference ratio (R0), - In the case where the ratio (R) is greater than the reference ratio (R0), the control unit (24) sends a command to the flow regulator (18) to increase the alkali solution flow rate (F). 2. The method for regulating the flow rate (F) of lye according to claim 1, characterized in that, according to the measured value of the current, the method comprises a configuration step (E2), wherein: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the measured value of the current, - the control unit (24) compares the measured value of the current (I) with a reference current measurement value (I0), - In the event that the measured value of the current (I) is greater than the reference current measured value (I0), the control unit (24) sends a command to the flow regulator (18) to reduce the alkali solution flow rate (F). 3. The method for regulating the flow rate (F) of alkali liquor according to any one of claims 1 to 2, characterized in that the method comprises a step (E4) of increasing the rotation speed of the pump, wherein: - the control unit (24) determines the value of the lye flow (F), i.e. the flow through the module (14), based on the information provided by the unit (20) for measuring the lye flow, - the control unit (24) compares the lye flow rate (F) with a high level (Fmax), and in case the lye flow rate (F) is substantially equal to or greater than the high level (Fmax), then: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the current, - the control unit (24) compares the measured value of the current (I) with the threshold current measurement value (I max ) for comparison, - when the measured value of the current (I) is substantially equal to or greater than the threshold current measurement value (I max ), the control unit sends a flow increase command to the pump to increase the alkali solution flow (F). 4. The method for regulating the flow rate (F) of alkali liquor according to any one of claims 1 to 3, characterized in that the method comprises a step (E5) of reducing the rotation speed of the pump, wherein: - the control unit (24) determines the value of the lye flow (F), i.e. the flow through the module (14), based on the information provided by the unit (20) for measuring the lye flow, - the control unit (24) compares the alkali solution flow rate (F) with a low level (Fmin), and in the event that the alkali solution flow rate (F) is substantially equal to or less than the low level (Fmin), then: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the current, - the control unit (24) compares the measured value of the current (I) with the threshold current measurement value (I min ) for comparison, - when the measured value of the current (I) is substantially equal to or less than the threshold current measurement value (I min ), the control unit (24) sends a flow reduction command to the pump (12) to reduce the alkali solution flow rate (F). 5. Method for regulating the lye flow rate (F) according to any one of claims 3 and 4, characterized in that the control unit (24) comprises a set of N predetermined incremental command values ​​for the pump (12) corresponding to N operating levels. 6. Method for regulating the lye flow (F) according to the preceding claim, characterized in that the reference current measurement value (I0) is defined for each operating level of the pump (12). 7. The method for regulating the alkali liquor flow (F) according to any one of claims 3 to 6, characterized in that when the control unit (24) sends a new command to the pump (12) allowing the speed of the pump (12) to be changed, the control unit (24) sends a command to fully open the flow regulator (18).

Claims

1. An electrolysis unit (10) comprising a pump (12) and a module (14), the module comprising electrolysis cells held against each other in a stacking direction, through which an electric current (I) and a lye flow (F) from the pump (12) flow, characterized in that The electrolysis unit (10) further comprises: - a unit (16) for measuring current, - a flow regulator (18) placed downstream of the pump (12) and upstream of the module (14), - a unit (20) for measuring the flow of alkali solution, capable of measuring the flow rate (F) of alkali solution flowing through said module (14), a gas sensor (22) placed downstream of the module and capable of measuring the amount of gas, and - a control unit (24) connected to the pump (12), the regulator (18), the unit for measuring the measured value of the electric current (16), the unit for measuring the lye flow (20) and the gas sensor (22).

2. A method for regulating the flow rate (F) of alkali solution in the electrolysis unit (10) according to claim 1, characterized in that According to the measured value of the current (I), the method comprises an optimization step (E1), wherein: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the measured value of the current, - the control unit (24) compares the measured value of the current (I) with a reference current measurement value (I0), - In the event that the measured value of the current (I) is less than the reference current measured value (I0), the control unit (24) sends a command to the flow regulator (18) to increase the alkali solution flow rate (F).

3. The method for regulating the alkali solution flow (F) according to claim 2, characterized in that According to the measured value of the current, the method comprises a configuration step (E2), wherein: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the measured value of the current, - the control unit (24) compares the measured value of the current (I) with a reference current measurement value (I0), - In the event that the measured value of the current (I) is greater than the reference current measured value (I0), the control unit (24) sends a command to the flow regulator (18) to reduce the alkali solution flow rate (F).

4. The method for regulating the alkali solution flow (F) according to any one of claims 2 and 3, characterized in that The method comprises a step (E3) of configuring the amount of bubbles, wherein: - the control unit (24) determines the amount of alkali solution (L) based on the information provided by the unit (20) for measuring the flow rate of alkali solution, - the control unit (24) determines the amount of bubbles (B) based on the information provided by the gas sensor (22), - the control unit (24) calculates a ratio (R) equal to the amount of bubbles (B) divided by the amount of lye (L): R=B / L, - said control unit (24) compares said ratio (R) with a reference ratio (R0), - In the case where the ratio (R) is greater than the reference ratio (R0), the control unit (24) sends a command to the flow regulator (18) to increase the alkali solution flow rate (F).

5. The method for regulating the alkali solution flow (F) according to any one of claims 2 to 4, characterized in that The method comprises a step (E4) of increasing the rotational speed of the pump, wherein: - the control unit (24) determines the value of the lye flow (F), i.e. the flow through the module (14), based on the information provided by the unit (20) for measuring the lye flow, - the control unit (24) compares the lye flow rate (F) with a high level (Fmax), and in case the lye flow rate (F) is substantially equal to or greater than the high level (Fmax), then: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the current, - the control unit (24) compares the measured value of the current (I) with the threshold current measurement value (I max ) for comparison, - when the measured value of the current (I) is substantially equal to or greater than the threshold current measurement value (I max ), the control unit sends a flow increase command to the pump to increase the alkali solution flow (F).

6. The method for regulating the alkali solution flow (F) according to any one of claims 2 to 5, characterized in that The method comprises a step (E5) of reducing the rotational speed of the pump, wherein: - the control unit (24) determines the value of the lye flow (F), i.e. the flow through the module (14), based on the information provided by the unit (20) for measuring the lye flow, - the control unit (24) compares the alkali solution flow rate (F) with a low level (Fmin), and in the event that the alkali solution flow rate (F) is substantially equal to or less than the low level (Fmin), then: - the control unit (24) determines the measured value of the current (I) based on the information provided by the unit (16) for measuring the current, - the control unit (24) compares the measured value of the current (I) with the threshold current measurement value (I min ) for comparison, - when the measured value of the current (I) is substantially equal to or less than the threshold current measurement value (I min ), the control unit (24) sends a flow reduction command to the pump (12) to reduce the alkali solution flow rate (F).

7. The method for regulating the alkali solution flow (F) according to any one of claims 5 and 6, characterized in that The control unit (24) includes a set of N predetermined incremental command values ​​for the pump (12) corresponding to N operating levels.

8. Method for regulating the lye flow (F) according to the preceding claim, characterized in that The reference current measurement value (I0) is defined for each operating level of the pump (12).

9. The method for regulating the alkali solution flow (F) according to any one of claims 5 to 8, characterized in that When the control unit (24) sends a new command to the pump (12) allowing the speed of the pump (12) to be changed, the control unit (24) sends a full-opening command to the flow regulator (18).

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