Electrolysis facility comprising a device for balancing pressures in gas-liquid separators

Abstract

The invention relates to an electrolysis facility comprising a main circuit in which a water-electrolyte mixture (MLH2, MLO2) passes through a gas-liquid cathode separator (10cat) and a gas-liquid anode separator (10an), the electrolysis facility comprising a balancing device (100) which is connected to the gas-liquid cathode separator (10cat) and to the gas-liquid anode separator (10an), characterised in that the balancing device (100), which makes it possible to compensate for pressure variations, comprises: a chamber (102), forming an expansion tank, the interior volume of which is divided by at least one elastically deformable partition (108) into an anode portion (Van) and a cathode portion (Vcat); a cathode pipe (104cat) for connecting the cathode portion (Vcat) to the upper portion of the gas-liquid cathode separator (10cat); and an anode pipe (104an) for connecting the anode portion (Van) to the upper portion of the gas-liquid anode separator (10an).

Description

[0001] Description

[0002] Title of the invention: Electrolysis installation comprising a pressure balancing device in the gas-liquid separators

[0003] Technical field of the invention

[0004] [1]The invention relates to an electrolysis installation, for the electrochemical production of dioxygen (O2) and dihydrogen (H2).

[0005] [2]The invention relates more particularly to an installation comprising a separate gas-liquid cathodic separator and a separate gas-liquid anodic separator arranged in parallel.

[0006] Technical background of the invention

[0007] [3]According to a well-known electrochemical process of the prior art, water is brought inside an array of electrolytic cells, called an electrolyzer stack, in the presence of an electrolytic solution (usually potassium hydroxide (KOH) or sodium hydroxide (NaOH), possibly with an additive) through a specific inlet, this water-electrolyte association being commonly called the lye.

[0008] [4]The electrolyzer stack consists of a stack of electrolytic cells, and the fluid passes through these electrolytic cells. Following this combined passage and the passage of a direct electric current through the electrolytic cells, the water is decomposed into gaseous molecules of dihydrogen at the cathode and dioxygen at the anode.

[0009] [5]According to these electrolysis reactions taking place in electrolytic cells:

[0010] - 1) Hydroxide anions (OH-) are consumed at the anode and transformed into water (H2O) and gaseous dioxygen (O2) molecules under the action of an electric current (electron: e-), 4 OH- — > O2 + 4 e- + 2 H2O;

[0011] - 2) Water molecules (H2O) are transformed at the cathode into dihydrogen (H2) and hydroxide anions (OH-) under the action of the same direct electric current,

[0012] 4 H2O + 4 e- 2 H2 + 4 OH-.

[0013] The stoichiometry of the electrolysis reaction shows that the dissociation of a water molecule generates a dihydrogen molecule and half a dioxygen molecule.

[0014] Since the molar volume of a gas is a constant, the production of dihydrogen is twice as large in volume as the production of dioxygen.

[0015] [6]Within each electrolytic cell, a diaphragm separates the anode from the cathode, which implies that, under normal operating conditions, the gaseous molecules of dihydrogen and dioxygen cannot be mixed.

[0016] [7] Unlike electrolytic cells, the electrolyzer stack has two separate outputs, including:

[0017] - i) the first outlet of a cathodic flow is dedicated to dihydrogen molecules in the presence of the lye flux; and - ii) the second outlet of an anodic flow has the same characteristics, but is reserved for dioxygen molecules still in the presence of the lye flux.

[0018] [8]Next, gas-liquid separation is defined as a major step in the alkaline electrolysis process of water. Indeed, the liquid and gaseous phases of each of these two gas-liquid mixtures must be separated so that the liquid phase is recycled in the electrolyzer and the gaseous phase is conditioned before being supplied to an end user (most often for dihydrogen, but also for dioxygen) or released into the atmosphere (often in the case of dioxygen (O2), or for dihydrogen (H2) for certain specific operating points).

[0019] [9]This separation takes place within a gas-liquid separator in which the said substances are separated, then the gases are washed and cooled before continuing their journey to a potential purification unit, while the lye flux flows are reintroduced into the closed-circuit electrolyzer stack.

[0020]

[0010] To achieve gas-liquid separation, each cathodic and anodic outlet of the electrolyzer stack is directly connected to an associated gas-liquid separator, cathodic and anodic respectively, in order to introduce the lye instantly into the appropriate gas-liquid separator, and more particularly at the height of the lower part of an inlet side face of the gas-liquid separator, and more particularly under the gas-liquid interface.

[0021]

[0011] Thus, the first cathodic gas-liquid separator is reserved for the separation of the dihydrogen-lye mixture, while the second anodic gas-liquid separator is intended for the separation of the dioxygen-lye mixture.

[0022]

[0012] Conventional gas-liquid separators operate on the principle of Archimedes' principle, which pushes gas bubbles to rise to the gas-liquid interface surface thanks to the difference in density between the gas bubbles (dihydrogen / dioxygen) and the liquid, all subject to the force of gravity.

[0023]

[0013] Thus, most generally, each of the gas flows is extracted through an outlet located on the upper face of the associated gas-liquid separator, while the liquid flows through an outlet located on the lower wall of the same gas-liquid separator.

[0024]

[0014] Considering that the production of gas is proportional to the electrolysis current, and that the production of dihydrogen is twice as important in volume as the production of dioxygen, any sudden variation in the electrolysis current causes a differential variation in the production of the two gases.

[0025]

[0015] Thus, at constant volume, a differential pressure appears between the two anodic and cathodic flow circuits.

[0026]

[0016] More specifically, at the level of the gas-liquid separators, this pressure difference arises because the volume of the gas-liquid separators is fixed and the evacuation of gases through the associated outlet ports is not instantaneous.

[0017] In order to counteract small pressure differences between the two cathodic and anodic flow circuits, it is known to balance the two gas-liquid separators by means of a balancing line. This is implemented in the form of a balancing pipe connecting the liquid phases of the two gas-liquid separators in a "U" configuration located below the gas-liquid separators.

[0027]

[0018] This balancing line, filled with lye, makes it possible to limit the differential pressure between the cathodic gas-liquid separator and the anodic gas-liquid separator by circulating a flow of liquid from the cathodic gas-liquid separator to the anodic gas-liquid separator and vice versa.

[0028]

[0019] This balancing line is positioned at a specific height "H1", relative to the aligned bottoms of the two cathodic and anodic gas-liquid separators. According to the principle of communicating vessels, this design promotes an identical fluid level in both gas-liquid separators at all times.

[0029]

[0020] However, a balancing line is not sufficient to counterbalance strong pressure differences on the anodic and cathodic sides that may appear during transient operating points (start-ups, increase / decrease in loads and rapid stops during maintenance phases or with intermittent energies).

[0030]

[0021] These operations can cause significant and sudden pressure differences between the cathodic gas-liquid separator and the anodic gas-liquid separator, despite the presence of the balancing line. These substantial pressure differences between the two flow circuits are found inside the electrolyzer stack between the cathodic and anodic sides of the electrolytic cell. They must be strictly avoided because they damage the diaphragms and other structural parts inside the electrolyzer stack.

[0031]

[0022] Furthermore, in the particular case of diaphragm alkaline electrolyzers, the porosity of the diaphragm imposes restrictions on the differential pressure between the anodic and cathodic compartments.

[0032]

[0023] An excessive pressure difference on either side of the diaphragm leads to a net flow of electrolyte through the diaphragm of each of the electrolytic cells. However, the electrolyte contains dissolved gases (dihydrogen and / or dioxygen), the concentration of which depends in particular on the operating pressure of the electrolyzer.

[0033]

[0024] For example, if the pressure is higher on the cathodic side, an electrolyte flow containing dissolved dihydrogen passes through the diaphragm. This results in contamination of the anodic flow containing dissolved dioxygen by dissolved dihydrogen. The opposite case is also possible when the pressure is higher on the anodic side; an electrolyte flow containing dissolved dioxygen passes through the diaphragm towards the cathodic side. Contamination of the cathodic flow, which contains dissolved dihydrogen, occurs with dissolved dioxygen.

[0025] The incorporation of gaseous dihydrogen produced at the cathode into the anodic circuit charged with gaseous dioxygen, and conversely, of gaseous dioxygen produced at the anode into the cathodic circuit charged with gaseous dihydrogen, is problematic.

[0034]

[0026] In an electrolyzer stack, the ratios of HTO gas (HTO, Hydrogen To Oxygen, English term designating the concentration of dihydrogen in dioxygen) and OTH gas (OTH, Oxygen To Hydrogen, English term designating the concentration of dioxygen in dihydrogen) must be minimized.

[0035]

[0027] Indeed, a gaseous mixture with a high HTO ratio of dihydrogen to dioxygen has a very low explosive limit (equal to 4% in a water electrolysis system according to ISO 22734). Similarly, a maximum HTO level (equal to 2% according to the same ISO 22734 standard) is prescribed to avoid any risk of explosion.

[0036]

[0028] If the threshold values ​​for the HTO or OTH ratios, defined according to the standards, are exceeded, an emergency shutdown of the system is triggered to prevent any risk. Furthermore, in a conventional electrolyzer stack system, both at the inlet of the electrolyzer stack and at the outlet of the gas-liquid separators, the two flows of cathodic and anodic fluid are recombined, which can increase the risk of exceeding said standards.

[0037]

[0029] In order to limit the pressure differences induced by rapid transient operations, a constraint on the operating dynamics of the electrolyzer must be imposed, which may reduce its suitability to follow an intermittent electricity source (for example a photovoltaic field or a wind turbine) and / or to provide auxiliary services to the electrical grid (for example a primary, secondary or tertiary reserve service).

[0038]

[0030] A design of a sliding piston pressure balancing cylinder is known from document CN219976163U which does not allow the electrolysis installation to absorb pressure differences induced by rapid transient operations.

[0039]

[0031] The invention aims to remedy these drawbacks.

[0040] Summary of the invention

[0041]

[0032] The invention also proposes an electrolysis installation for the electrochemical production of dioxygen and dihydrogen, comprising a main circuit in which, under the action of a main pump, a water-electrolyte mixture, called lye, circulates in a loop, passing successively through:

[0042] - a stack of electrolytic cells, called an electrolyzer stack, comprising an anode section for the generation of dioxygen and a cathode section for the generation of dihydrogen;

[0043] - a set of gas-liquid separators comprising a cathodic gas-liquid separator and an anodic gas-liquid separator arranged in parallel and which:

[0044] - in the lower part, they are connected by a balancing pipe;

[0045] - in the upper part, each respectively comprising an outlet for dihydrogen and dioxygen gas, the electrolysis installation comprising a balancing device, allowing compensation of pressure variations, which is connected to the cathodic gas-liquid separator and the anodic gas-liquid separator, characterized in that the balancing device, allowing compensation of pressure variations, comprises:

[0046] - an enclosure, forming an expansion vessel, whose internal volume is divided, by at least one partition elastically deformable into an anodic part and a cathodic part;

[0047] - a cathode ray tube connecting said cathode ray section of the enclosure to the volume of gaseous H2 contained in the upper part of the gas-liquid cathode separator; and

[0048] - an anodic pipe connecting said anodic part of the enclosure to the volume of gaseous O2 contained in the upper part of the gas-liquid anodic separator.

[0049]

[0033] According to other characteristics of the installation:

[0050] - the internal volume of the enclosure is divided by at least one elastically deformable partition between said cathode part and said anode part of the enclosure;

[0051] - the internal volume of the enclosure is divided by at least two adjacent partitions, elastically deformable, which delimit between them an intermediate space between said cathodic part and said anodic part of the enclosure and which is equipped with a sensor for measuring the pressure prevailing inside this intermediate space;

[0052] - each elastically deformable partition is an elastically deformable membrane that extends between two parts, cathodic and anodic, of the enclosure wall;

[0053] - each elastically deformable partition is an elastically deformable bladder which is arranged inside the enclosure and whose connecting end is connected to the connecting pipe of said cathodic part of the enclosure or to the connecting pipe of said anodic part of the enclosure;

[0054] - The balancing device includes:

[0055] - a controlled cathodic valve allowing the connection of said cathodic part of the enclosure to the upper part of the gas-liquid cathodic separator to be interrupted; and

[0056] - a controlled anodic valve allowing the connection of said anodic part of the enclosure to the upper part of the gas-liquid anodic separator to be interrupted;

[0057] - the entrance to said cathode part of the enclosure is fitted with a permeable barrier; and the entrance to said anode part of the enclosure is fitted with a permeable barrier;

[0058] - Each permeable barrier is arranged in different locations within the enclosure, near each of the two opposite ends of each connecting pipe; - Each permeable barrier is shaped into a grid or a perforated plate or a non-hermetic arrangement.

[0059] Brief description of the figures

[0060]

[0034] [Fig. 1] - Figure 1 is a schematic and simplified representation of an electrolysis installation according to the prior art;

[0061]

[0035] [Fig. 2] - Figure 2 is a schematic representation of a first example of the realization of a pressure balancing device suitable for equipping an electrolysis installation illustrated in Figure 1;

[0062]

[0036] [Fig. 3] - Figure 3 is a schematic representation of a second example of the realization of a pressure balancing device suitable for equipping an electrolysis installation illustrated in Figure 1;

[0063]

[0037] [Fig. 4] - Figure 4 is a schematic representation illustrating a first variant of the first example of the realization of a pressure balancing device illustrated in Figure 2;

[0064]

[0038] [Fig.5] - Figure 5 is a schematic representation illustrating a second variant of the first example of an embodiment of a pressure balancing device illustrated in Figure 2.

[0065] Detailed description of the invention

[0066]

[0039] For the description of the invention and the understanding of the claims, the vertical, longitudinal, and transverse orientations according to the V, L, T coordinate system shown in the figures shall be adopted, without limitation and without limiting reference to Earth's gravity, in which the longitudinal axis L and transverse axis T extend in a horizontal plane. By convention, the vertical axis V is oriented from bottom to top and the longitudinal axis L is oriented from back to front.

[0067]

[0040] In the description that follows, identical, similar or analogous elements will be designated by the same reference numerals.

[0068]

[0041] Figure 1 shows an electrolysis installation 200 according to the prior art, for the electrochemical production of dioxygen and dihydrogen comprising a main fluid circulation circuit including successively a stack of electrolytic cells, called electrolyzer stack 202, a set of gas-liquid separators comprising a cathodic gas-liquid separator 10cat and an anodic gas-liquid separator 10an arranged in parallel, and a circulation pump P.

[0069]

[0042] A power conversion unit 204 has also been represented in a known manner.

[0070]

[0043] In a known manner, under the action of the pump P, the water-electrolyte mixture, called lye, circulates in a closed loop, successively passing through the electrolyzer stack 202 and the set of gas-liquid separators 10cat, 10an, from which it emerges in the form of a cathodic flow and an anodic flow of the lye, which feed the inlet of the pump P.

[0044] The outlet of the pump P is connected to the inlet of the electrolyzer stack 202.

[0071]

[0045] The pump P is a controlled variable flow pump.

[0072]

[0046] In Figure 1, each gas-liquid separator, cathodic 10cat and anodic 10an - that is to say separation of gaseous dihydrogen-gaseous dioxygen with the lye - is essentially and respectively made up of a cathodic body 12cate and anodic body 12an which extends longitudinally along the axis T in the direction "C" of circulation of the liquid phase inside them 12cat, 12an.

[0073]

[0047] According to the reference frame V, L, T, in cross-sectional view, the cathode body 12cate and anode body 12an are for example globally of circular cylindrical shape and in particular delimited respectively vertically by a lower wall 14cat, 14an and an upper wall 16cat, 16an and respectively longitudinally by an entrance lateral wall 18cat, 18an and an opposite lateral wall 20cat, 20an.

[0074]

[0048] Each body, cathodic 12cat and anodic 12an, here comprises an inlet for the introduction of a gas-liquid mixture, more particularly a dihydrogen-lye mixture and a dioxygen-lye mixture. In the present case, said inlet is respectively in the form of a lateral orifice 24cat, 24an for the introduction of this gas-liquid mixture which is arranged in the corresponding inlet lateral wall 18cat, 18an of said body 12cat, 12an.

[0075]

[0049] ll 12cat, 12an also includes a gas outlet, more particularly dihydrogen and dioxygen, which is in the form of an outlet 26cat, 26an which is arranged respectively in the upper wall 16cat, 16an of said body 12cat, 12an.

[0076]

[0050] These outlet ports 26cat, 26an are therefore located in the upper part of the body 12cat, 12an, more particularly in the upper part above the gas-liquid interface Seat, San, in the vicinity of the opposite side wall 20cat, 20an.

[0077]

[0051] By way of non-limiting, each body 12cat, 12an further includes an outlet of the liquid phase which is in the form of an outlet 22cat, 22an which is arranged in the lower wall 14cat, 14an, in the vicinity of the opposite lateral wall 20cat, 20an.

[0078]

[0052] The gas-liquid mixture is introduced into the gas-liquid separator 10cat, 10an, which it partially fills and within which it flows longitudinally, delimiting the gas-liquid interface Seat, San, of generally horizontal orientation, which separates the essentially liquid phase, more or less charged with gas bubbles (H2, O2) to be eliminated, underlying said gas-liquid interface Seat, San, from the gaseous phase, above said gas-liquid interface Seat, San.

[0079]

[0053] At the end of the passage of the gas-liquid mixture through gas-liquid separator 10cat, 10an, and therefore after separation, a cathodic liquid phase Ecat, an anodic phase Ean is recovered in the lower part and through the outlet orifice 22cat, 22an.

[0080]

[0054] In the upper part and through the outlet 26cat, 26an, a "separated" gaseous phase of dihydrogen and dioxygen O2 is recovered respectively.

[0081]

[0055] In order to counterbalance small pressure differences between the two cathodic and anodic flow circuits, it is known to balance the two gas-liquid separators 10cat, 10an by means of a balancing line 28. The latter is made in the form of a balancing line connecting the liquid phases of the two gas-liquid separators 10cat, 10an in a “U” configuration, located either under the latter 10cat, 10an by connecting the two lower walls 14cat, 14an, or laterally with respect to the latter 10cat, 10an by connecting the two opposite lateral walls 20cat, 20an.

[0082]

[0056] This balancing line, filled with lye, makes it possible to limit the differential pressure between the gas-liquid separator 10cat and the gas-liquid separator 10an by circulating a flow of liquid from the gas-liquid separator 10cat to the gas-liquid separator 10an, and vice versa.

[0083]

[0057] This balancing pipe is positioned at a specific height, "H", relative to the lower wall, aligned, of the two gas-liquid separators 10cat and 10an.

[0084]

[0058] This approach promotes an identical fluid level in both the cathodic and anodic gas-liquid separators at all times, according to the principle of communicating vessels. This differential pressure limitation is necessary for the proper operation of the electrolyzer. Furthermore, this hydraulic barrier prevents the passage of gas from the cathodic gas-liquid separator to the anodic gas-liquid separator, as well as in the opposite direction, in order to minimize the formation of an explosive mixture.

[0085]

[0059] First example of implementation

[0086] According to a first embodiment of the invention, and as can be seen in figure 2, the electrolysis installation 200 described previously (not shown in the present case) is equipped with a balancing device 100, allowing to absorb and compensate for pressure variations.

[0087]

[0060] The balancing device 100 makes a connection between the upper parts of the two cathodic gas-liquid separators 10cat and anodic 10an, more particularly a connection between the two sections in contact with the gaseous part of the gas-liquid separators 10cat, 10an which extends above the gas-liquid interface Seat, San.

[0088]

[0061] The balancing device 100 includes a chamber 102, forming an expansion vessel, which is connected to the upper parts of the two cathodic gas-liquid separators 10cat and anodic gas-liquid separators 10an.

[0089]

[0062] The connection is made by two connecting pipes 104cat, 104an.

[0090]

[0063] A cathodic connecting pipe 104cat is used to connect the upper part of the cathodic gas-liquid separator 10cat to the enclosure 102 and an anodic connecting pipe 104an is used to connect the upper part of the anodic gas-liquid separator 10an to the enclosure 102.

[0091]

[0064] An inlet 105cat, 105an of each connecting pipe 104cat, 104an allows communication between the upper part of the associated gas-liquid separators 10cat, 10an and the enclosure 102. Each inlet 105cat, 105an is preferably located in the upper wall 16cat, 16an of the associated gas-liquid separators 10cat, 10an.

[0065] An outlet 106cat, 106an of each connecting pipe 104cat, 104an is connected to the enclosure 102. Each outlet 106cat, 106an is located either on the lower wall 103, or on a transverse side wall 101, or at a lower corner of the enclosure 102, at the intersection of the transverse walls 101 and the lower wall 103, as illustrated.

[0092]

[0066] The two distinct outputs 106cat, 106an are preferably located opposite each other, distributed symmetrically with respect to a median vertical plane along the vertical axis V of the enclosure 102.

[0093]

[0067] Two separate and controlled valves 110cat, 110an allow the connection of each gas-liquid separator 10cat, 10an with the enclosure 102 to be interrupted.

[0094]

[0068] Each valve 110cat, 110an is here implanted in the associated connecting pipe 104cat, 104an.

[0095]

[0069] Preferably, at least one 110cat, 110an controlled valve is present on each of the 104cat, 104an connecting pipes.

[0096]

[0070] In the event of excessively high HTO and / or OTH or in the event of an emergency stop or forced depressurization of the gas-liquid separators 10cat, 10an, the valves 110cat and 110an allow the enclosure 102 to be isolated from the gas-liquid separators 10cat, 10an, more precisely these valves 110cat, 110an induce the cessation of gas exchange between the upper parts of the two gas-liquid separators 10cat, 10an and the enclosure 102.

[0097]

[0071] To ensure its function of compensating for rapid pressure variations, the internal volume of the enclosure 102 is divided, in a sealed manner, into two parts or volumes, of which a cathodic part, Vcat, to which the gaseous volume of the cathodic separator 10cat is connected by the connecting pipe 104cat, and an anodic part, Van, to which the gaseous volume of the anodic separator 10an is connected by the connecting pipe 104an.

[0098]

[0072] This division is obtained by means of at least one partition 108 which is here an elastically deformable membrane which gives the balancing device 100, and more particularly the enclosure 102, a variable geometry to balance the pressures between the two gaseous volumes of the cathodic 10cat and anodic 10an gas-liquid separators.

[0099]

[0073] The definition of a partition 108, and more particularly of a membrane 108, or of a bladder 112 (represented in figure 3) as will be seen later with reference to the second embodiment of the invention, is as follows.

[0100]

[0074] It is a structural element having the capacity to absorb large volumes of gas without deforming irreversibly, that is to say, it deforms elastically without plastic deformation or dilation.

[0101]

[0075] The membrane 108 deforms according to the pressure difference between the two gas-liquid separators 10cat, 10an, that is to say according to the differences between the pressures prevailing in each of the two parts Vcat, Van separated by the membrane

[0076] The constituent materials of such a partition 108, 112 are varied, with the capacity to withstand the operating conditions of the electrolyzer stack 202 (pressure, temperature, aggressiveness of the environment, ...), for example, it may be polymer material(s), such as for example those used in hydraulic accumulators.

[0102]

[0077] Each membrane 108 or bladder 112 provides a variable geometry to balance sudden and rapid pressure differences between the two gas-liquid separators 10cat, 10an. Indeed, in some cases, the flow velocities of the flows from the lower part of the gas-liquid separators 10cat, 10an containing the liquid phase through the balancing line 28, are insufficient to compensate for a sudden and high pressure differential.

[0103]

[0078] One or more membrane(s) 108 or bladder(s) 112 allow(s) to dampen the rapid pressure differentials between the two gas-liquid separators 10cat, 10an.

[0104]

[0079] The technical characteristics and capacity of the enclosure 102 acting as an expansion vessel are defined according to the geometry and dimensions of the enclosure 102 and of the membrane(s) 108 or the bladder(s) 112.

[0105]

[0080] In the first example of embodiment shown schematically in Figure 2, the deformable structural element forming an elastically deformable partition 108 is a membrane 108 whose perimeter is fixed to the inner walls of the enclosure 102. In other words, the entire periphery of the membrane 108 is continuously fixed to the inner walls of the enclosure 102 in order to ensure the seal between the two parts Vcat, Van, regardless of the geometry of said enclosure 102.

[0106]

[0081] The membrane 108 is secured by means of multiple fixing points located on the inner walls of the enclosure 102. In this case, and without limitation, the membrane 108 has a geometry close to that of a distended circular element. The longitudinal positioning of the membrane 108 is a parameter for the distribution of gas volumes in the Vcat and Van sections.

[0107]

[0082] Generally, the membrane 108 is positioned at any distance from the transverse walls 101 of the enclosure 102, in other words it is positioned anywhere along the total length L of the enclosure 102 so that the periphery of said membrane 108 remains fixed to the inner walls of the enclosure 102.

[0108]

[0083] Preferably, the membrane 108 is positioned at mid-length of the total length L of the enclosure 102. This position ensures an equivalent distribution of the gaseous volumes of the two gas-liquid separators 10cat, 10an.

[0109]

[0084]

[0110]

[0085] The pressure of the gas entering the cathodic gas-liquid separator 10cat and the pressure of the gas entering the anodic gas-liquid separator 10an are essentially the same. Consequently, the liquid levels in both gas-liquid separators 10cat and 10an are maintained in equilibrium, in conjunction with the analogous function provided by the balancing line 28.

[0111]

[0086] As can be seen in Figure 2, but also in Figure 3 illustrating the second embodiment, both the inlet into the cathodic part Vcat, and the inlet into the anodic part Van are respectively provided with at least one mechanical barrier 116cat, 116an, permeable to gases and liquids.

[0112]

[0087] Each barrier 116cat, 116an is for example formed into a grid or a perforated plate, or non-hermetic arrangements.

[0113]

[0088] lci, each barrier 116cat, 116an is adjacent to the outlet 106cat, 106an of the corresponding connecting pipe 104cat, 104an.

[0114]

[0089] Each barrier 116cat, 116an has a dual role. First, by being permeable, they allow gas exchange between the gas-liquid separators 10cat, 10an and the enclosure 102.

[0115]

[0090] Furthermore, each barrier 116cat, 116an prevents any possible displacement of the membrane 108 or the bladder 112 inside the associated connecting pipe 104cat, 104an. Thus, the barriers 116cat, 116an keep the membrane 108 or the bladder 112 inside the enclosure 102 and prevent deformation beyond its deformation capacity in the perfectly elastic range, wear, or even rupture.

[0116]

[0091] As an alternative, the barriers 116cat, 116an can be arranged in different locations within the enclosure 102, near each of the two opposite ends 106cat, 106an of each connecting pipe 104cat, 104an.

[0117]

[0092] Second example of implementation

[0118] As explained above, the design of the balancing device 100 incorporates at least one membrane 108 or at least one elastically deformable and gas-tight bladder 112.

[0119]

[0093] The term bladder or membrane depends on the type of enclosure and its method of attachment to the inner walls of the enclosure.

[0120]

[0094] In the second embodiment shown schematically in figure 3, the elastically deformable partition is a bladder 112.

[0121]

[0095] The bladder 112 is three-dimensionally shaped like a pouch or balloon, having a tapered end in the form of a connecting nozzle 114. In other words, the attachment to the inner walls of the enclosure 102 is made around a small periphery. The attachment points are close to each other and close to the connecting pipe, 104cat or 104an.

[0122]

[0096] This connecting end 114 must be fixed to one of the outlets 106cat, 106an of a connecting pipe 104cat, 104an, that is to say either to the outlet 106cat of the connecting pipe 104cat of the cathodic gas-liquid separator 10cat, or to the outlet 106an of the connecting pipe 104an of the anodic gas-liquid separator 10an.

[0123]

[0097] In figure 3, the connecting end 114 of the bladder 112 is connected in a sealed manner to the outlet 106cat and it delimits an internal part which is the Vcat part, separated in a sealed manner from the other Van part of the enclosure 102.

[0124]

[0098] According to this design and arrangement, the gas flow from outlet 106cat of connecting pipe 104cat will never, or only very partially, come into contact with the walls of enclosure 102.

[0099] Furthermore, the bladder 112 has the capacity to absorb a significant volume of gas, which can, for example, correspond to half the internal volume of enclosure 102, or even to the total volume of enclosure 102, or even to two-thirds of the volume of enclosure 102 in order, for the reasons mentioned above, to contain a greater volume of dihydrogen than dioxygen.

[0125]

[0100] Variants in embodiment of figures 4 and 5

[0126] As shown in figures 4 and 5, several adjacent or joined membranes can be arranged inside the enclosure 102, thus forming a group of adjacent membranes (which are generally and preferentially parallel but not limited to this) and which provide the same elastically deformable partition function as a single membrane.

[0127]

[0101] Similarly, although not shown in the figures, at least two adjacent or joined bladders, nested within each other, can be arranged inside the enclosure 102, thus constituting a group of adjacent bladders which provide the same elastically deformable partition function as that of the single bladder 112 illustrated in figure 3.

[0128]

[0102] In the case of a system with at least two membranes or at least two bladders, adjacent or joined, a pair of adjacent membranes, bladders delimit between them an intermediate space between the cathodic part Vcat and the anodic part Van of the enclosure 102.

[0129]

[0103] By way of non-limitation, the balancing device 100 may be equipped with a sensor 120 for measuring the pressure prevailing inside this intermediate space.

[0130]

[0104] More specifically, as illustrated in Figure 4, two adjacent membranes 108-1 and 108-2 are shown which delimit an intermediate space 109 to which a pressure sensor 120 is associated.

[0131]

[0105] The intermediate space 109 between the two membranes 108-1 and 108-2 is not subjected to the pressure prevailing inside the electrolysis installation 200, more specifically the pressure prevailing in the gas-liquid separators 10cat and 10van and in the electrolyzer stack 202.

[0132]

[0106] The pressure inside the intermediate space 109 is equivalent to a reference pressure (Pref) lower than the operating pressure of the electrolysis system.

[0133]

[0107] The pressure sensor 120 is permanently connected to a Programmable Logic Controller (PLC) not shown, in order to ensure continuous monitoring.

[0134]

[0108] If the pressure value in the intermediate space 109 is higher than the reference pressure Pref, this means that a rupture has occurred in one of the two adjacent partitions 108 (membranes or bladders), allowing the accidental passage of the gas contained in the enclosure 102 and the associated pressure of the installation into the intermediate space 109. The rupture of the elastically deformable partition 108 can be due, for example, to repetitive movements resulting from frequent use or to wear due to use in an aggressive environment. Indeed, the gases contain lye residues and have not yet been purified.

[0109] The proposed balancing device 100, with a pressure sensor 120 in the intermediate space 109, thus makes it possible to detect a leak and / or a rupture.

[0135]

[0110] Nevertheless, thanks to the presence of a second partition 108, no gas exchange in the enclosure 102, between the volume of gas coming from the gas-liquid separator 10cat and that coming from the gas-liquid separator 10an is possible and the risk of explosion (related to the HTO / OTH levels) is not increased.

[0136]

[0111] For their control, the valves 110cat and 110an are also connected to the PLC. Consequently, if the pressure sensor 120 indicates an inadequate pressure value in the intermediate space 109, the PLC generates a command to close the valves 110cat and 110an. This action either depressurizes the enclosure 102 or the gas-liquid separators 10cat and 10an, or triggers an emergency shutdown of the entire electrolysis plant 200.

[0137]

[0112] Maintenance operators can then proceed to replace the defective component.

[0138]

[0113] An overpressure value is reached when it exceeds the reference pressure value Pref. However, the overpressure must be accompanied by a tolerance. Indeed, part of the additional pressure is related to the measurement error due to the measurement accuracy of the pressure sensor 120, the connection with the PLC, the installation of the partition 108, etc.

[0139]

[0114] The pressure sensor 120, associated with the valves 110cat, 110an, is therefore an additional safety element in the electrolysis installation 200 because it prevents its operation in dangerous operating conditions and it allows the replacement of the partition(s) 108 when it is (are) at the end of its life.

[0140]

[0115] As shown in figure 5 it is possible to provide for more than two, and here for example three, adjacent membranes 108 joined together.

[0141]

[0116] Thus, three membranes 108-1, 108-2 and 108-3 can be joined together and which, two by two, delimit between them an intermediate space 109A, 109B, each of which is associated with a pressure sensor 120A, 120B.

[0142]

[0117] The operation is the same as that shown above in relation to figure 4 in the presence of two membranes 108-1, 108-2 joined together.

[0143]

[0118] In the case of a first pressure variation measured by a pressure sensor 120A, 120B located in the intermediate space 109 A, 109B, information representative of the rupture of one of the three membranes 108-1, 108-2, 108-3 is notified to the PLC (for example, failure of membrane 108-1).

[0144]

[0119] Nevertheless, the group of membranes 108-1, 108-2, 108-3, includes at least one additional membrane (for example the membrane 108-3), and the balancing device 100 can continue to play its role with at least two membranes 108-1, 108-2 operational because the pressure value in the intermediate space 109B between the two membranes 108-2 and 108-3 is always close to the reference pressure Pref.

[0145]

[0120] The division, and therefore the sealing, of the two parts Vcat and Van of the enclosure 102 is always maintained by two of the three membranes 108-1, 108-2. When a second pressure variation is measured by the pressure sensor(s) 120A (120B) located in one or more intermediate spaces 109A (109B), a rupture of one of the two remaining membranes 108-2, 108-3 is transmitted to the PLC. At this stage, the same procedure described in Figure 4 is applied with the actuation of valves 110cat and 110an.

[0146]

[0121] The approach described above in Figure 5, involving more than two, and here for example three, adjacent membranes 108 joined together, is also valid when considering more than two, and for example three, adjacent bladders 112 joined together (not shown in the figures). All the technical characteristics and associated functionalities are similar to those obtained in the case of multiple adjacent membranes 108 joined together.

[0147]

[0122] A possible integration of a balancing device 100 according to the invention into an electrolysis installation 200 with two gas-liquid separators connected by the balancing device 100 has been described.

[0148]

[0123] Without departing from the scope of the invention, it is conceivable to have several electrolysis systems consisting of several electrolyzer stacks, several gas-liquid separators, several controllable pumps, arranged in series and / or in parallel, and several power conversion units. Each gas-liquid separator can be arranged horizontally, vertically, or a combination of the two orientations.

[0149]

[0124] l The same applies with regard to the number of electrolytic cells inside the electrolyzer stack(s), namely that the implementation of the teachings of the invention is independent of the number of electrolytic cells.

[0150]

[0125] Cathodic and anodic gas-liquid separators typically have the shape of a cylinder with a circular base. However, other cross-sectional geometries, which can maximize the free surface area available to the gas, can be used, such as an elliptical or ovoid cross-section. The same applies to any geometric configuration of gas-liquid separators.

[0151]

[0126] Furthermore, the enclosure can also adopt several geometries other than that represented in the figures below, and for example ovoid, elliptical, rectangular or any other shape.

Claims

Demands

1. Electrolysis plant (200), for the electrochemical production of dioxygen (O2) and dihydrogen (H2), comprising a main circuit in which, under the action of a main pump (P), a water-electrolyte mixture (MLH2, MLO2), called lye, circulates in a loop, passing successively through: - a stack of electrolytic cells, called an electrolyzer stack (202), comprising an anode section for the generation of dioxygen and a cathode section for the generation of dihydrogen; - a set of gas-liquid separators comprising a cathodic gas-liquid separator (10cat) and an anodic gas-liquid separator (10an) arranged in parallel and which: - in the lower part, are connected by a balancing pipe (28); - in the upper part, each respectively comprising an outlet orifice (26cat, 26an) for dihydrogen and dioxygen gas, the electrolysis installation (200) comprising a balancing device (100), allowing compensation of pressure variations, which is connected to the cathodic gas-liquid separator (10cat) and the anodic gas-liquid separator (10an), characterized in that the balancing device (100), allowing compensation of pressure variations, comprises: - an enclosure (102), forming an expansion vessel, the internal volume of which is divided, by at least one partition (108, 112) elastically deformable into an anodic part (Van) and a cathodic part (Vcat); - a connecting cathode ray tube (104cat) from said cathode ray section (Vcat) of the enclosure (102) to the volume of gaseous H2 contained in the upper part of the gas-liquid cathode separator (10cat); and - an anodic connecting pipe (104an) from said anodic part (Van) of the enclosure (102) to the volume of gaseous O2 contained in the upper part of the gas-liquid anodic separator (10an); and in that the internal volume of the enclosure (102) is divided by at least two adjacent partitions (108-1, 108-2, 108-3), elastically deformable, which delimit between them an intermediate space (109, 109A, 109B) between said cathodic part (Vcat) and said anodic part (Van) of the enclosure (102) and which is equipped with a sensor (120, 120A, 120B) for measuring the pressure prevailing inside this intermediate space (109, 109A, 109B).

2. Electrolysis installation (200) according to claim 1, characterized in that each elastically deformable partition (108-1, 108-2, 108-3) is an elastically deformable membrane (108-1, 108-2, 108-3) which extends between two parts, cathodic (Vcat) and anodic (Van), of the wall of the enclosure (102).

3. Electrolysis installation (200) according to any one of claims 1 or 2, characterized in that each elastically deformable partition (108-1, 108-2, 108-3) is an elastically deformable bladder (112) which is arranged inside the enclosure (102) and of which a connecting end (114) is connected to the connecting pipe (104cat) of said cathodic part (Vcat) of the enclosure (102) or to the connecting pipe (104an) of said anodic part (Van) of the enclosure (102).

4. Electrolysis plant (200) according to any one of the preceding claims, characterized in that the balancing device (100) comprises: - a controlled cathodic valve (110cat) allowing the connection of said cathodic part (Vcat) of the enclosure (102) to the upper part of the gas-liquid cathodic separator (10cat); and - a controlled anodic valve (110an) allowing the connection of said anodic part (Van) of the enclosure (102) to the upper part of the gas-liquid anodic separator (10cat) to be interrupted.

5. Electrolysis plant (200) according to any one of the preceding claims, characterized in that: - the entrance of said cathode part (Vcat) of the enclosure (102) is equipped with a permeable barrier (116cat); - the entrance to said anodic part (Van) of the enclosure (102) is equipped with a permeable barrier (116an).

6. Electrolysis installation (200) according to claim 5, characterized in that each permeable barrier (116cat, 116an) is arranged at different locations in the enclosure (102), near each of the two opposite ends (106cat, 106an) of each connecting pipe (104cat, 104an).

7. Electrolysis installation (200) according to the preceding claim, characterized in that each permeable barrier (116cat, 116an) is shaped into a grid or a perforated plate or a non-hermetic arrangement.

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