Method for regulating the flow of lye within an electrolysis unit, and associated electrolysis unit

Abstract

The present invention relates to a method for regulating the flow of lye within an electrolysis unit and to an associated electrolysis unit (10) comprising a pump (12) and a module (14) comprising electrolysis cells held against each other in a stacking direction, the module (14) being traversed by a flow of lye (F) coming from the pump (12) and by an electric current (I), the electrolysis unit (10) further comprising: - a measurement unit for measuring the electric current (16), - a flow regulator (18) placed downstream of the pump (12) and upstream of the module (14), - a unit for measuring the flow of lye (20) able to measure the flow rate of lye (F) passing through the module (14), - a gas sensor (22) placed downstream of the module and able to measure an amount of gas, and - a control unit (24) connected to the pump (12), to the regulator (18), to the unit for measuring the electric current (16), to the unit for measuring the flow of lye (20) and to the gas sensor (22).

Description

[0001] DESCRIPTION

[0002] TITLE: Method for regulating the flow of lye within an electrolysis unit and associated electrolysis unit

[0003] Technical field of the invention

[0004] The present invention relates to a method for regulating the flow of lye within an electrolysis unit and an associated electrolysis unit. Technical background

[0005] The overall architecture of an electrolyzer stack, also called an electrolysis module, is usually made up of a block of electrolytic cells, stacked in series from an electrical point of view and in parallel from a fluidic point of view, and joints. The purpose of each electrolytic cell is to carry out the electrolysis of an electrolytic solution. As a whole, the objective of the electrolyzer stack is to promote the reaction of production of dihydrogen (H2) and dioxygen (O2) gas resulting from the dissociation of water after injecting a direct electric current into an alkaline solution, generally potassium hydroxide (KOH) or sodium hydroxide (NaOH). This water-electrolyte association is commonly called lye.

[0006] Each electrolytic cell, considered as a mainly metallic and conductive part, is generally composed of two bipolar plates, two spacers framed by the two bipolar plates and two electrodes including an anode and a cathode framed by the two spacers.

[0007] The electrodes are generally formed of plates or grids or metal fabrics and are arranged in such a way as to be separated by a membrane ensuring:

[0008] - electrical insulation between the electrodes,

[0009] - gas separation, as well as

[0010] - ionic conduction within the electrolytic cell.

[0011] The interlayer has two functions: i) to provide a low resistivity metallic path between each bipolar plate and the associated electrode, and ii) to allow proper circulation of the electrolytic solution for cooling the electrolyzer stack and transporting the generated gases.

[0012] Opposite these electrolytic cells appears a double output: i) the first is dedicated to the dihydrogen molecules in the presence of the lye flow, and ii) the second output has the same characteristics but reserved for the dioxygen molecules still in the presence of the lye.

[0013] Downstream of the electrolytic cells, gas-liquid separation is defined as a major step in the alkaline water electrolysis process.

[0014] The electrolytic solution present in each electrolytic cell as well as the gases produced by the electrolysis must not leak from the edge of the diaphragm to the outside of the electrolytic cell in question but must circulate only through the dedicated pipes. Each pipe is dedicated either to the electrolyte alone, or to the electrolyte mixed with one of the gases. The two gases cannot mix with each other.

[0015] The electrolyser stack can therefore no longer operate continuously if a leak is detected, whether from the electrolytic solution, gases generated by electrolysis, or any other substance.

[0016] Typically, when a leak occurs, various problems arise that have a negative impact on the environment and also on the safety of operators. The severity of a leak varies and can reach a significantly high value linked to irreversible consequences.

[0017] One of the causes of gas leaks can be the accumulation of gas bubbles around the electrodes. Thus, within an electrolytic cell of an electrolyzer stack in operation, when the value of the electric current increases significantly, the production of dihydrogen and dioxygen also increases and can cause an accumulation of gas bubbles around the electrodes. The accumulation of gas bubbles impairs the proper circulation of gas bubbles in the dedicated pipes since the accumulated gas bubbles circulate with more difficulty and are more difficult to evacuate towards the gas-liquid separator. Poor circulation of gas bubbles creates risks of leakage or even explosion.

[0018] Furthermore, due to the accumulation of gas bubbles, the circulation of charge carriers within an electrolytic cell of the electrolyzer stack is drastically slowed down, which leads to an increase in the electrical resistance of the electrolytic cell. The increase in the electrical resistance of the electrolytic cell leads to a deterioration in the efficiency of the electrolyzer stack.

[0019] Summary of the invention

[0020] The invention proposes an electrolysis unit comprising a pump and a module comprising electrolysis cells held against each other in a stacking direction, the module being crossed by a flow of lye coming from the pump and by an electric current, the electrolysis unit further comprising:

[0021] - a unit of measurement of electric current,

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

[0023] - a lye flow measurement unit capable of measuring the flow of lye passing through the module,

[0024] - a gas sensor placed downstream of the module, the gas sensor being capable of measuring a quantity of gas, and

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

[0026] "Measuring electric current" means measuring the value of the electric current intensity (in amperes) passing through the module.

[0027] The term "electric current" means an electric current resulting from the flow of electric charge.

[0028] "Flow" refers to the quantity of fluid that passes through the module in a given time. Flow is similar to a flow rate, which is measured, for example, in m 3 / s. The invention also proposes a method for regulating the flow of lye within an electrolysis unit according to the invention, the method comprising a step of optimizing the electric current in which:

[0029] - the control unit determines the measurement of the electric current from the information provided by the electric current measuring unit,

[0030] - the control unit compares the measurement of the electric current with a measurement of the reference electric current,

[0031] - if the electric current measurement is lower than the reference electric current measurement, then the control unit sends a command to the flow regulator capable of increasing the lye flow.

[0032] According to other variants of the method of the invention:

[0033] - the method includes a step of adapting the electric current in which:

[0034] - the control unit determines the measurement of the electric current from the information provided by the electric current measuring unit,

[0035] - the control unit compares the measurement of the electric current with a measurement of the reference electric current,

[0036] - if the measurement of the electric current is greater than the measurement of the reference electric current, then the control unit sends a command to the flow regulator capable of reducing the flow of lye;

[0037] - the method includes a step of adapting the quantity of gas bubbles in which:

[0038] - the control unit determines the quantity of lye from the information provided by the lye flow measurement unit,

[0039] - the control unit determines the quantity of gas bubbles from the information provided by the gas sensor,

[0040] - the control unit calculates a ratio equal to the quantity of gas bubbles divided by the quantity of lye,

[0041] - the control unit compares the ratio with a reference ratio,

[0042] - if the ratio is higher than the reference ratio, then the control unit sends a command to the flow regulator capable of increasing the lye flow; - the method includes a step of adapting the pump speed by higher stage in which:

[0043] - the control unit determines the value of the lye flow, i.e. the flow rate passing through the module, from the information provided by the lye flow measurement unit,

[0044] - the control unit compares the lye flow with a high level, if the lye flow is substantially equal to or greater than the high level, then:

[0045] - the control unit determines the measurement of the electric current from the information provided by the current measurement unit,

[0046] - the control unit compares the measurement of the electric current with a measurement of the threshold electric current,

[0047] - if the measurement of the electric current is substantially equal to or greater than the measurement of the threshold electric current, then the control unit sends a flow increase command to the pump capable of increasing the flow of lye;

[0048] - the method includes a step of adapting the pump speed by lower stage in which:

[0049] - the control unit determines the value of the lye flow, i.e. the flow rate passing through the module, from the information provided by the lye flow measurement unit,

[0050] - the control unit compares the lye flow with a low level, if the lye flow is substantially equal to or lower than the low level, then:

[0051] - the control unit determines the measurement of the electric current from the information provided by the electric current measuring unit,

[0052] - the control unit compares the electric current measurement with a threshold electric current measurement,

[0053] - if the measurement of the electric current is substantially equal to or less than the measurement of the threshold electric current, then the control unit sends a flow reduction command to the pump capable of reducing the flow of lye; - the control unit comprises a set of N increasing and predetermined command values ​​for the pump corresponding to N operating levels;

[0054] - the reference current measurements and / or the reference ratio are defined for each pump operating level;

[0055] - when the control unit sends a new command to the pump allowing a change in pump speed, then the control unit sends a maximum opening command to the flow regulator.

[0056] Brief description of the figures

[0057] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0058] [Fig.1] is a block diagram representing the arrangement and operation of an electrolysis unit according to the invention.

[0059] Detailed description of the invention

[0060] The invention relates to an electrolysis unit 10 shown in Figure 1. The electrolysis unit 10 comprises a module 14 also called an electrolyzer stack comprising a stack of electrolysis cells held against each other in a stacking direction.

[0061] The electrolysis cells of module 14 are connected in series from an electrical point of view and in parallel from a fluidic point of view. Each electrolytic cell is capable of carrying out the electrolysis of an electrolytic solution allowing the production of gaseous dihydrogen (H2) and dioxygen (O2). The electrolysis carried out is a chemical reaction allowing the dissociation of water after injecting a 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 comprises a combination of water and electrolyte, the electrolysis resulting from the dissociation of the solutes into ions. The solution obtained is commonly called lye. In operation, module 14 is crossed by a flow of lye F.In order to allow the flow of lye F to circulate in the module 14, the electrolysis unit 10 comprises a pump 12. The flow of lye F at the outlet of the module 14 is commonly routed to gas-liquid separators then to a filter to be freed of impurities, particularly metallic ones, then reinjected into the module 14 via the pump 12. The lye thus circulates within a closed circuit.

[0062] An electric current I flows through the module 14. The electric current flows through the electrolysis cells and thus allows the electrolysis of the alkaline solution to be carried out. To enable the generation of an electric current I, a voltage is applied to the terminals of the module 14. The resulting electric current I depends on the electrical resistance of the module 14.

[0063] Under optimal operating conditions, the module 14 operates according to theoretically defined reference values, both for the electric current I and for the lye flow F entering the module 14. The reference value of the electric current lo and the reference value of the lye flow Fo are defined according to the sizing of the upstream pump 12 in order to obtain an optimal quantity of gas bubbles B within the module 14. Thus, the electric current I and the quantity of gas bubbles B gravitating around the electrodes correspond to maximum efficiency.

[0064] In practice, during actual operation of the module 14, the actual measurements of the electric current I and lye flux F may be lower or higher than the respective reference values ​​lo and Fo, which causes a reduction in the efficiency of the module 14.

[0065] The invention proposes a control loop regulating the flow of lye to avoid significantly deviating from the reference measurements linked to the electric current I and / or the flow of lye F inside the module 14.

[0066] According to particular features of the invention and with a view to implementing a control loop, the electrolysis unit 10 further comprises:

[0067] - an electric current measurement unit 16 integrated into the power supply circuit of the module 14,

[0068] - a flow regulator 18 fluidly connected to the pump 12 and to the module 14 and placed downstream of the pump 12 and upstream of the module 14,

[0069] - a lye flow measurement unit 20 capable of measuring the flow rate of lye F passing through the module 14,

[0070] - a gas sensor 22 placed downstream of the module 14 capable of measuring a quantity of gas, and

[0071] - a control unit 24 connected to the pump 12, to the regulator 18, to the electric current measurement unit 16, to the lye flow measurement unit 20, and to the gas sensor 22.

[0072] In Figure 1, the dotted lines represent electrical connections, the solid lines represent lye transport pipes, and the broken line at the module outlet represents gas-charged lye transport pipes.

[0073] The arrangement of the electrolysis unit 10 allows the implementation of a control loop which acts on the regulation of the flow of lye F through the control of the flow regulator 18 and the pump 12 according to the information provided by:

[0074] - the unit of measurement of electric current 16,

[0075] - the unit of measurement of the lye flow 20, and

[0076] - gas sensor 22.

[0077] This control loop is fully automated, meaning that human intervention at Module 14 is no longer required, thereby eliminating a potential hazard associated with human intervention.

[0078] The control loop is implemented by the 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:

[0079] - the unit of measurement of electric current 16,

[0080] - the unit of measurement of the lye flow 20, and

[0081] - gas sensor 22.

[0082] Information can be received continuously by the control unit

[0083] 24. Based on the information received, the control unit 24 determines and sends commands intended for the flow regulator 18 and the pump 12.

[0084] The control loop is implemented by the control unit 24 according to a closed loop which is repeated cyclically with a predetermined periodicity or according to predefined occurrences.

[0085] The control unit 24 is managed and manipulated by human intervention remotely from the module 14.

[0086] The first element analyzed by the control unit 24 is the electric current I within the module 14 closely linked to the flow of lye F entering the latter 14. At each instant, it is possible to measure the electric current I entering the module 14 by means of the electric current measurement unit 16 in order to systematically compare the measurement of the electric current I with a reference measurement called the reference electric current lo.

[0087] If the measurement of the electric current I is similar to a measurement greater than the measurement of the reference electric current lo, the control unit 24 will send a signal to the lye flow regulator 18 to adapt the value of the lye flow F entering the module 14 so as to no longer exceed the measurement of the reference electric current lo. Thanks to this adjustment of the value of the lye flow F entering the module 14 through the lye flow regulator 18 located upstream of the module 14, the measurement of the current I within the electrolytic cells in the module 14 will therefore be adapted so that it reaches the measurement of the reference electric current lo.

[0088] Thus, the method of the invention comprises a step E1 of optimization based on the measurement of the electric current I in which:

[0089] - the control unit 24 determines the measurement of the electric current I from the information provided by the electric current measurement unit 16,

[0090] - the control unit 24 compares the measurement of the electric current I with the measurement of the reference electric current lo,

[0091] - if the measurement of the electric current I is lower than the measurement of the reference electric current lo, then the control unit 24 sends a command to the flow regulator 18 capable of increasing the flow of lye F. Alternatively or in addition, the method comprises a step E2 of adaptation according to the measurement of the electric current I in which:

[0092] - the control unit 24 determines the measurement of the current I from the information provided by the electric current measurement unit 16,

[0093] - the control unit 24 compares the measurement of the electric current I with a measurement of the reference electric current lo,

[0094] - if the measurement of the electric current I is greater than the measurement of the reference electric current lo, then the control unit 24 sends a command to the flow regulator 18 capable of reducing the flow of lye F.

[0095] Steps E1 and E2 can be combined into a single step in which:

[0096] - the control unit 24 determines the measurement of the electric current I from the information provided by the electric current measurement unit 16,

[0097] - the control unit 24 compares the measurement of the electric current I with the measurement of the reference electric current lo,

[0098] - if the measurement of the electric current I is greater than the measurement of the reference electric current lo, then the control unit 24 sends a command to the flow regulator 18 capable of reducing the flow of lye F, and

[0099] - if the measurement of the electric current I is lower than the measurement of the reference electric current lo, then the control unit 24 sends a command to the flow regulator 18 capable of increasing the flow of lye F.

[0100] When steps E1 and E2 are not combined, within step E1, if the measurement of the electric current I is not greater than the measurement of the reference electric current lo, then step E1 ends and can be the subject of a new subsequent iteration.

[0101] Similarly, when steps E1 and E2 are not combined, within step E2, if the measurement of the electric current I is not less than the measurement of the reference electric current lo, then step E2 ends and can be the subject of a new subsequent iteration.

[0102] The measurement of the electric current I is influenced by the accumulation of gas bubbles B which hinders and slows down the circulation of the charge carriers inside the module 14. The slowing down of the charge carriers leads to an increase in the electrical resistance of the module 14. The increase in the electrical resistance of the module 14 causes a deterioration in the efficiency of the electrolysis unit 10. In particular, for the same electrical voltage applied to the edges of the module 14 and for an unchanged contact surface between the electrodes and the electrolyte, the measurement of the electric current I is lower the greater the electrical resistance. Thus, the increase in the flow of lye F allows better circulation of the gas bubbles B towards the gas-liquid separation units and thus reduces the electrical resistance of the module 14 and therefore increases the measurement of the electric current I.This explains that when the measurement of the electric current I is lower than the measurement of the reference electric current lo, the increase in the flow of lye F makes it possible to readjust the measurement of the electric current I by increasing its value.

[0103] The second element analyzed by the control unit 24 is the value of the lye flow F entering the module 14 in direct relation to the quantity of gas bubbles B present around the electrodes in the electrolytic cells of the module 14, the quantity of gas bubbles B of which is preferably measured downstream of the module 14. To achieve maximum efficiency of the electrolysis unit 10, the ratio R between the quantity of gas bubbles B at the outlet of the electrolytic cells and the quantity of lye L must be equal to a reference ratio Ro in all circumstances. This is why the gas sensor 22, placed downstream of the module 14, is used to measure the quantity of gas bubbles B so that, subsequently, the control unit 24 calculates said ratio R between the quantity of gas bubbles B and the quantity of lye L.

[0104] The quantity of gas bubbles B is for example defined as being the number of moles of gas present in all the gas bubbles B passing through the gas sensor 22 in a predetermined period of time.

[0105] The quantity of lye L is for example defined as:

[0106] - the number of moles of solute entering module 14 in a predetermined period of time, or

[0107] - a volume of lye entering module 14 within a predetermined period of time, or

[0108] - a mass of lye entering module 14 within a predetermined period of time.

[0109] The method then comprises a step E3 of adapting the quantity of gas bubbles B in which:

[0110] - the control unit 24 determines the quantity of lye L from the information provided by the lye flow measurement unit 20,

[0111] - the control unit 24 determines the quantity of gas bubbles B from the information provided by the gas sensor 22,

[0112] - the control unit 24 calculates a ratio R equal to the quantity of gas bubbles B divided by the quantity of lye L: R=B / L,

[0113] - the control unit 24 compares the ratio R with the reference ratio Ro,

[0114] - if the ratio R is greater than the reference ratio Ro, then the control unit 24 sends a command to the flow regulator 18 capable of increasing the flow of lye F.

[0115] Indeed, increasing the flow of lye F makes it possible to reduce the ratio R by a double effect:

[0116] - on the one hand the ratio R=B / L being inversely proportional to the quantity of lye L and therefore to the flow of lye F, the ratio decreases when the flow of lye increases,

[0117] - on the other hand, the increase in the flow of lye F makes it possible to drive the gas bubbles B towards the gas-liquid separation units and thus to reduce the quantity of gas bubbles B and therefore the ratio R which is proportional to the quantity of gas bubbles B.

[0118] Thus, step E3 makes it possible to approach or even equal the value of the reference ratio Ro.

[0119] The third element analyzed by the control unit 24 is the value of the lye flow F to adjust the operation of the lye circulation pump 12 also located upstream of the module 14.

[0120] Two cases are studied including: i) a first case in which the lye flow F is equal to a high level Fmax while the measurement of the electric current I is greater than the measurement of the threshold electric current l max relative to the high level, and ii) a second case in which the lye flux F is equal to a low level Fmin while the measurement of the electric current I is lower than the threshold current value l m in relative to the low level. The measurement of the electric current I allows us to know if we are in the first case i) or in the second case ii).

[0121] The high level Fmax corresponds to a value of the lye flow rate limit in higher value.

[0122] The low level Fmin corresponds to a lower limit lye flow rate value.

[0123] It is also possible to be neither in the first case nor in the second case, for example:

[0124] - when the lye flow F is below a high level or above a low level, or

[0125] - when the measurement of the electric current I is substantially equal to within a tolerance margin of the measurement of the reference electric current lo, or

[0126] - when the lye flow F is equal to a high level but the measurement of the electric current I is lower than the measurement of the threshold electric current l ma x relative to the upper level, or

[0127] - when the lye flow F is equal to a low level but the measurement of the electric current I is greater than the measurement of the threshold electric current lmin relative to the low level.

[0128] When the second case ii) occurs, it is because the measurement of the electric current I is lower and the production of gas bubbles B is also lower. Consequently, for the same production of gas bubbles B, the pump speed as well as the value of the lye flow F can be lower.

[0129] When the first case i) occurs, in the presence of a high measurement of the electric current I, it is preferable to run the pump 12 at a higher speed to increase the importance of the flow of lye F. Indeed, this high measurement of the electric current I leads to a significant production of gas bubbles B and therefore creates an increased risk of accumulation of gas bubbles B within the module 14. This is why it is imperative to increase the flow of lye F entering the module 14 in order to promote the evacuation of the gas bubbles B.

[0130] In both cases, the ratio R between the quantity of gas bubbles B at the outlet of the module 14 and the quantity of lye L can always be measured by the control unit 24 as described previously so that the value of the ratio R is always sent to the control unit 24. The control unit 24 can also determine a command for the pump 12 as a function of the value of the ratio R in order to adapt the rotation speed of the pump 12 to thus regulate the value of the flow of the lye F and to optimize the circulation of the gas bubbles B within the module 14.

[0131] Thus, to manage the first case i), the method of the invention comprises a step E4 of adapting the pump speed by higher stage in which:

[0132] - the control unit 24 determines the value of the lye flow F, i.e. the flow rate passing through the module 14, from the information provided by the lye flow measurement unit 20,

[0133] - the control unit 24 compares the lye flow F with the high level Fmax.

[0134] If the lye flow F is lower than the high level Fmax, then step E4 ends and can be repeated in a new subsequent iteration.

[0135] If the lye flow F is substantially equal to or greater than the high level Fmax, then:

[0136] - the control unit 24 determines the measurement of the current I from the information provided by the current measurement unit 16,

[0137] - the control unit 24 compares the measurement of the current I with the measurement of the threshold current l ma x relative to the high level.

[0138] If the measurement of current I is lower than the measurement of threshold current lmax, then step E4 ends and can be subject to a new subsequent iteration.

[0139] If the measurement of current I is substantially equal to or greater than the measurement of threshold current lmax, then the control unit sends a flow increase command to the pump capable of increasing the flow of lye F.

[0140] To manage the second case ii), the method of the invention comprises a step E5 of adapting the pump speed by lower stage in which:

[0141] - the control unit 24 determines the value of the lye flow F, i.e. the flow rate passing through the module 14, from the information provided by the lye flow measurement unit 20,

[0142] - the control unit 24 compares the lye flow F with the low level Fmin.

[0143] If the lye flow F is greater than the low level Fmin, then step E5 ends and can be repeated in a new subsequent iteration.

[0144] On the contrary, if the lye flow F is substantially equal to or lower than the low level Fmin, then:

[0145] - the control unit 24 determines the measurement of the current I from the information provided by the current measurement unit 16,

[0146] - the control unit 24 compares the measurement of the current I with a measurement of the threshold current l m relative to the lower level.

[0147] If the measurement of current I is greater than the measurement of threshold current lmin, then step E5 ends and can be subject to a new subsequent iteration.

[0148] If the measurement of the current I is substantially equal to or less than the measurement of the threshold current lmin, then the control unit 24 sends a flow reduction command to the pump 12 capable of reducing the flow of lye F.

[0149] Equal or substantially equal means a comparison that may include a margin of tolerance, for example, to within 10%.

[0150] To send a command to the pump 12, the control unit 24 may use commands in a predetermined data table. For example, the control unit 24 may include, in a database, a set of N predetermined, increasing command values ​​for the pump 12 corresponding to N operating levels.

[0151] At each instant, the control unit 24 is able to determine in which stage the pump is operating. If the control unit 24 must send a flow reduction command to the pump 12, the control unit 24 sends the command corresponding to the stage immediately below the current stage. If the control unit 24 must send a flow increase command to the pump 12, the control unit 24 sends the command corresponding to the stage immediately above the current stage.

[0152] The measurements of the reference current lo and possibly the reference ratio Ro are defined for each operating level of the pump 12. Indeed, a large lye flow is adapted to a large current measurement.

[0153] When the control unit 24 sends a new command to the pump 12 allowing a change in the speed of the pump 12, then the control unit 24 sends a maximum opening command to the flow regulator 18. This allows the entire flow of lye circulated by the pump 12 to enter the module 14 during a change of level. Regulation by means of the flow regulator 18 can then be put in place according to the regulation method described above.

[0154] This embodiment of the invention is said to be preferred but it is entirely possible to have several modules 14 arranged in series and / or in parallel. Each module 14 can appear horizontally, vertically or a combination of the two orientations, regardless of the arrangement studied. The same applies to the number of electrolytic cells inside the module(s) 14. The approach defined is independent of the number of electrolytic cells studied.

[0155] In the invention described above, the gas bubbles G accumulated around the electrodes in the module 14 will move more easily towards the gas-liquid separator following the adaptation of the flow of lye F at the inlet of the module 14. Thus, the efficiency of the electrolysis unit 10 will be improved.

Claims

CLAIMS 1. Electrolysis unit (10) comprising a pump (12) and a module (14) comprising electrolysis cells held against each other in a stacking direction, the module (14) being crossed by a flow of lye (F) coming from the pump (12) and by an electric current (I), the electrolysis unit (10) being characterized in that it further comprises: - a unit for measuring electric current (16), - a flow regulator (18) placed downstream of the pump (12) and upstream of the module (14), - a lye flow measurement unit (20) capable of measuring the flow rate of lye (F) passing through the module (14), - a gas sensor (22) placed downstream of the module capable of measuring a quantity of gas, and - a control unit (24) connected to the pump (12), to the regulator (18), to the electric current measurement unit (16), to the lye flow measurement unit (20) and to the gas sensor (22).

2. Method for regulating the flow of lye (F) within an electrolysis unit (10) according to claim 1, characterized in that it comprises an optimization step as a function of the measurement of the electric current (I) (E1) in which: - the control unit (24) determines the measurement of the electric current (I) from the information provided by the electric current measurement unit (16), - the control unit (24) compares the measurement of the electric current (I) with a measurement of the reference electric current (lo), - if the measurement of the electric current (I) is lower than the measurement of the reference electric current (lo), then the control unit (24) sends a command to the flow regulator (18) capable of increasing the flow of lye (F).

3. Method for regulating the flow of lye (F) according to claim 2, characterized in that it comprises a step of adaptation according to of the measurement of the electric current (E2) in which: - the control unit (24) determines the measurement of the electric current (I) from the information provided by the electric current measurement unit (16), - the control unit (24) compares the measurement of the electric current (I) with a measurement of the reference electric current (lo), - if the measurement of the electric current (I) is greater than the measurement of the reference electric current (lo), then the control unit (24) sends a command to the flow regulator (18) capable of reducing the flow of lye (F).

4. Method for regulating the flow of lye (F) according to claims 2 or 3, characterized in that it comprises a step of adapting the quantity of gas bubbles (E3) in which: - the control unit (24) determines the quantity of lye (L) from the information provided by the lye flow measurement unit (20), - the control unit (24) determines the quantity of gas bubbles (B) from the information provided by the gas sensor (22), - the control unit (24) calculates a ratio (R) equal to the quantity of gas bubbles (B) divided by the quantity of lye (L): R=B / L, - the control unit (24) compares the ratio (R) with a reference ratio (Ro), - if the ratio (R) is greater than the reference ratio (Ro), then the control unit (24) sends a command to the flow regulator (18) capable of increasing the lye flow (F).

5. Method for regulating the flow of lye (F) according to any one of claims 2 to 4, characterized in that it comprises a step of adapting the pump speed by higher stage (E4) in which: - the control unit (24) determines the value of the lye flow (F), i.e. the flow rate passing through the module (14), from the information provided by the lye flow measurement unit (20), - the control unit (24) compares the lye flow (F) with a high level (Fmax), if the lye flow (F) is substantially equal to or greater than the high level (Fmax), then: - the control unit (24) determines the measurement of the electric current (I) from the information provided by the electric current measuring unit (16), - the control unit (24) compares the measurement of the electric current (I) with a measurement of the threshold electric current (Imax), - if the measurement of the electric current (I) is substantially equal to or greater than the measurement of the threshold electric current (Imax), then the control unit sends a flow increase command to the pump capable of increasing the flow of lye (F).

6. Method for regulating the flow of lye (F) according to any one of claims 2 to 5, characterized in that it comprises a step of adapting the pump speed by lower stage (E5) in which: - the control unit (24) determines the value of the lye flow (F), i.e. the flow rate passing through the module (14), from the information provided by the lye flow measurement unit (20), - the control unit (24) compares the lye flow (F) with a low level (Fmin), if the lye flow (F) is substantially equal to or lower than the low level (Fmin), then: - the control unit (24) determines the measurement of the electric current (I) from the information provided by the current measuring unit (16), - the control unit (24) compares the measurement of the electric current (I) with a measurement of the threshold electric current (Imin), - if the measurement of the electric current (I) is substantially equal to or less than the measurement of the threshold electric current (Imin), then the control unit (24) sends a flow reduction command to the pump (12) capable of reducing the flow of lye (F).

7. Method for regulating the flow of lye (F) according to any one of claims 5 or 6, characterized in that the control unit (24) comprises a set of N increasing and predetermined control values ​​for the pump (12) corresponding to N operating levels.

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

9. Method for regulating the flow of lye (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 a change in the speed of the pump (12), then the control unit (24) sends a maximum opening command to the flow regulator (18).

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