Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/02—Hydrogen or oxygen
  • C25B1/04—Hydrogen or oxygen by electrolysis of water
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/70—Assemblies comprising two or more cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

• the invention relates to a method for the electrolysis of high temperature water (EHT) also called electrolysis of high temperature water vapor (EVHT) in order to produce hydrogen.
• EHT high temperature water
• EVHT high temperature water vapor
• EHT electrolysers at high temperatures
• An electrolyser comprises a plurality of elementary cells formed by a cathode and an anode separated by an electrolyte, the elementary cells being connected electrically in series by means of interposed interconnecting plates, generally between an anode of an elementary cell and a cathode of the next elementary cell.
• interconnecting plates are electronic conductive components formed by a metal plate. These plates also ensure the separation between the cathodic fluid circulating at the level of an elementary cell of the anode fluid flowing in a next elementary cell.
• the anode and the cathode are porous material in which the gases can flow.
• water vapor circulates at the cathode where hydrogen is generated in gaseous form, and a draining gas can circulate at the same time. level of the anode and thus participate in the evacuation of oxygen generated in gaseous form at the anode.
• Most high temperature electrolysers use air as the draining gas at the anode.
• the design of a plant implies first that it is necessary to consider breaking one or more cells, which causes either the shutdown of 1 electrolyser concerned, or its operation in degraded mode.
• An object of the invention is to propose a solution that allows a hydrogen production plant comprising a large number of high temperature electrolysers to have high reliability and to maintain a constant production efficiency. without the disadvantages of the solutions of the prior art.
• An object of the invention is therefore to provide a solution that allows, at lower cost, not to suffer losses of efficiency of a high temperature electrolyser (EHT) due to possible breakage of cells and further aging of those -this.
• EHT electrolyser
• the subject of the invention is a process for the electrolysis of water at high temperatures carried out by an electrochemical reactor comprising a stack of N elementary electrochemical cells each formed of a cathode, an anode and and an electrolyte interposed between the cathode and the anode, at least one interconnecting plate being arranged between two adjacent elementary cells and in electrical contact with an electrode of one of the two elementary cells and an electrode of the other of the two cells elementary elements, in which at least water vapor is circulated in contact with the cathode and a draining gas is circulated in contact with the anode to evacuate the oxygen produced, characterized in that the following steps are carried out: :
• the electrolyzer to aim a stable operation that is to say self-thermal assembly consisting of 1 electrolyser (electrochemical reactor) and the associated heat exchanger system.
• 1 electrolyser electrochemical reactor
• the aim here is therefore a slightly exothermic operation of the electrolyser.
• the water vapor containing at most 1% of hydrogen enters the electrolyzer at lower temperatures (heat at low temperatures) at high operating temperatures and is warmed by the energy dissipated by the Joule effect. electrical origin therefore) in the heart of 1 electrolyser, that is to say within each cell.
• the cell break configurations contemplated in the context of the invention are those which do not cause interruption of the electrical connection at the cell but only create a hydraulic "short circuit" between anode and cathode. The inventors have found that these breakage configurations were those typically observed in practice, that is to say with the architectures and sizing electrolysers already known to date. It goes without saying that one skilled in the art will take care, in the context of the invention, to ensure that the architecture and sizing of an electrolyser do not lead to breakage of electrical connection at each level. cell.
• the solution according to the invention makes it possible to operate a high temperature electrolyser with little or no yield loss due to possible breakage of one or more cells, without the need to involve active piloting. compensation.
• the electrolyser reacts by itself and reliably to cell breakage phenomena, reducing any risk of serious damage.
• the solution according to the invention therefore consists of a combination of means for respectively carrying out:
• the voltage at the terminals of the broken elementary cell decreases: in fact, the amount of water vapor is greater, the broken elementary cell is hotter. As the voltage at the terminals of the cell is lower, the operation of the broken elementary cell can be considered endothermic, that is to say that the local electrolysis downstream as well as upstream of the case consumes some of the heat in excess. .
• N + 1 cells Considering a stack of a number of N + 1 cells, with the number N very high, for example N ⁇ 1000.
• u cel u cel 0 - ⁇
• N u 0 N u - ⁇
• i i 0 + ⁇ / NR.
• the inventor reaches the conclusion that the variations induced by a breakage of a cell on the other unbroken cells are even lower than the value of N is large.
• this is the case.
• the electrolysis made locally downstream of the case participates in the global production of hydrogen by stacking cells.
• the overpressure of the water vapor containing at most 1% hydrogen at the anode relative to that at the cathode may be between 5 and 100 mbar, preferably 30 mbar.
• the number N of elementary cells and the voltage level imposed and kept constant are such that the unit voltage level at the terminals of each elementary cell is of the order of 1.3 volts.
• This value corresponds to the voltage which allows the assembly consisting of 1 electrolyser associated with the system of heat to have a stable operation, that is to say the auto thermal operation with some heat losses if necessary. It goes without saying that this value is determined for water vapor containing at most 1% hydrogen.
• the conversion rate to initial hydrogen is preferably of the order of 100%.
• the flow of water vapor is increased at each cathode, when the conversion rate to hydrogen initially determined at the outlet of each cathode decreases. This ensures a given production rate that does not decrease.
• hydrolysis rate at the outlet of the cathode it is understood the proportion of water vapor at the inlet of the cathode which is converted by electrolysis into hydrogen at the cathode outlet.
• the initial conversion rate 100%, it collects, out of any breakage, only hydrogen at the cathode outlet.
• the initial conversion rate determined is of the order of 100%, those skilled in the art will take care to implement a condensation stage to condense the unconverted water vapor during aging.
• the process can operate at temperatures of at least 450 ° C, typically between 700 ° C and 1000 ° C.
• the invention also relates to a device for electrolysis of water at high temperatures, comprising an electric voltage source and a reactor comprising a stack of elementary electrochemical cells each formed of a cathode, anode and a electrolyte interposed between the cathode and the anode, at least one interconnecting plate being arranged between two adjacent elementary cells and in electrical contact with an electrode of one of the two elementary cells and an electrode of the other of the two elementary cells, the interconnecting plate comprising at least one cathode compartment and at least one anode compartment for the circulation of gas respectively at the cathode and the anode.
• one of the ends of the cathode compartments is connected to a feed adapted to deliver steam containing at most 1% of hydrogen and one of the ends of the anode compartments is also connected to a feed adapted to deliver water vapor containing at most 1% hydrogen at overpressure with respect to those of the cathode, the feeds being adapted to deliver water vapor at lower temperatures at which the electrolysis is carried out,
• the device comprises means connected to the voltage source for delivering a substantially constant voltage Uo across the two interconnecting plates of the stack furthest away from each other.
• the invention relates to a hydrogen production assembly comprising a plurality of devices such as that described above.
• FIG. 1 is a side view of an embodiment of a reactor for high temperature electrolysis according to the present invention
• FIG. 1A is a sectional view of the reactor of FIG. 1 along plane A-A in cell-free electrolysis operation
• Figure 1B is a sectional view of the reactor of Figure 1 along the plane B-B also in cell-free electrolysis operation
• FIG. 2 is a view similar to FIG. 1B but schematizing a case of a cell
• FIGS. 3A, 3B, and 3C show schematically a current distribution along a channel in an electrolysis reactor according to the invention respectively in operation without the breakage of electrolysis cells, in operation with a break located in a first zone of a cell and, in operation with a case located in a second cell area distinct from the first zone,
• FIG. 4 shows schematically the evolution of the hydrogen conversion rate along a cell according to the invention and having not undergone aging.
• the invention is described in connection with a type of high temperature water electrolyser architecture to produce hydrogen. It goes without saying that the invention can be applied to other architectures.
• the high temperatures at which the electrolyser represented is at least at 450 ° C, typically between 700 ° C and 1000 ° C.
• upstream and downstream are used by reference with the direction of circulation of the water vapor and the hydrogen produced at the cathode.
• FIG. 1 there is shown an EHT electrolyser according to the present invention comprising a plurality of elementary cells C1, C2 ... stacked.
• Each elementary cell comprises an electrolyte disposed between a cathode and an anode.
• the cell C1 comprises a cathode 2.1 and anode 4.1 between which is disposed an electrolyte 6.1, generally 100 ⁇ thick for so-called cells with electrolyte support and a few ⁇ thickness for so-called cathode support cells.
• Cell C2 comprises a cathode 2.2 and anode 4.2, between which an electrolyte 6.2 is disposed.
• the cathodes 2.1, 2.2 and the anodes 4.1, 4.2 are made of porous material and have, for example, a thickness of 40 ⁇ for so-called support electrolyte cells and with a thickness of about 500 ⁇ for the cathode of the so-called cells. cathode support and 40 ⁇ for the anode.
• the anode 4.1 of the cell C1 is electrically connected to the cathode 2.2 of the cell C2 by an interconnecting plate 8 coming into contact with the anode 4.1 and the cathode 2.2. Furthermore, it allows the power supply of the anode 4.1 and the cathode 2.2.
• An interconnecting plate 8 is interposed between two elementary cells C1, C2.
• the interconnecting plate 8 defines with the adjacent anode and cathode channels for the circulation of fluids. More specifically, they define anode compartments 9 dedicated to the flow of gases at the anode 4 and cathode compartments 11 dedicated to the flow of gas at the cathode 2.
• an anode compartment 9 is separated from a cathode compartment 11 by a wall 9.11.
• the interconnecting plate 8 further comprises at least one duct 10 delimiting with the wall 9.11, the anode compartments 9 and the cathode compartments 11.
• the interconnecting plate 8 comprises a plurality of ducts 10 and a plurality of anode compartments 9 and cathodes 11.
• the duct 10 and the compartments have hexagonal sections, honeycomb, which allows to increase the density of compartments 9, 11 and ducts 10.
• Other sections may also be suitable for compartment sections.
• FIG. 1A water vapor containing at most 1% of hydrogen is circulated to each cathode 2.1, 2.2 and to each anode 4.1, 4.2 as a draining gas.
• the arrows 12 and 13 of FIG. 1A thus clearly represent the simultaneous path in the anode compartments 9 and cathodes 11. It goes without saying that in the context of the invention the symbolized flow can equally well be done in the other direction (arrows 12 and 13 in opposite direction).
• the architecture of the electrolyser further makes it possible to connect the first end 10.1 of the conduit 10 to a feed of water vapor containing at most 1% of hydrogen via another conduit and to connect the second end 10.2 of the conduit 10 to the cathode compartment 11.
• the arrow 14 symbolizes the return flow of the water vapor since its flow in the conduit 10 (arrow 16) to the cathode compartment 11. It is specified here that the initial flow in the conduit 10 of the water vapor allows to homogenize the temperatures and thus to avoid thermal gradients likely to damage cells.
• each cathode compartment 11 is at lower operating temperatures, i.e. those at which the electrolysis of the water along each cathode compartment is carried out by heating the steam by the dissipated energy. by Joule effect.
• the temperatures at the inlet of the cathode compartment 11.1 are of the order of 800 ° C for operating temperatures (during electrolysis along the cathode compartment 11) up to 820 ° C.
• the circulating water vapor in the anode channel or compartment 9 is also put under overpressure with respect to that flowing in the cathode channel or compartment 11 (arrows 13).
• the overpressure is between 15 and 100mbar, preferably of the order of 30mbar.
• FIG. 2 shows a cell C1 case situation typically observed in already experimented electrolysers: the electrolyte 6.1 is broken but the electrical connection is still ensured by the interconnecting plate 8.
• the oxygen having passed through the broken zone 17 recombines with the hydrogen already present upstream in the cathode compartment 11 to form water with a release of heat.
• FIG. 3A shows the line of distribution of the current along an electrolytic cell cathode 2 according to the invention that has not undergone any breakage: the area of the hatched area represents the total current passing through the cell. elementary. This total current is fully used for local electrolysis at the cell cathode 2.
• FIGS. 3B and 3C respectively show the distribution line segments of the current along the same cathode but in a situation of breakage, the location of the broken zone 17 in FIG. 3B being distinct from that of FIG. 3C.
• the area of the hatched areas here also represents the total current always applied to the elementary cell. However, here the current represented by the hatched area in continuous lines, that is to say corresponding to the part of the cell downstream of the breakage 17 contributes mainly to the electrolysis at the cell. Indeed, the current represented by the hatched area in broken lines, that is to say upstream of the breakage 17 contributes in a minor way to the electrolysis.
• the electric voltage across the broken elementary cell decreases. Since the electrical voltage at the terminals of the cell is lower, the operation of the broken elementary one can be considered endothermic, that is to say that the local electrolysis downstream as well as upstream of the case consumes some of the heat in excess.
• FIG. 3B and 3C are distinguished by the fact that, in the configuration of FIG. 3C, the current is not zero at the output of the cathode compartment 11.2: it can therefore be considered that compared to the configuration of Figure 3B the local production of hydrogen is less. It can therefore also be deduced from these examples that the lower the initial conversion rate (outside of any breakage) is chosen, the less self-regulation referred to by the invention is effective. We must therefore aim for the highest possible conversion rate, at best of the order of 100%.
• FIG. 4 shows the evolution of the hydrogen conversion rate a which occurs by the electrolysis reaction along a channel (cathode compartment 11) flowing along a cathode 2.i of an electrolysis cell Ci.
• this conversion rate has increased as the gas progresses.
• the initial aim is to designate an electrolyser according to the invention, a conversion rate ⁇ of the order of 0 at compartment inlet 11.1. , corresponding to a non-hydrogenated water vapor, and of the order of 100% at the outlet of the cathode compartment 11.2, corresponding only to hydrogen.
• the inventors started from the principle that this conversion rate necessarily decreased due to the aging phenomenon of the electrolysis cells in an electrolyser according to the state of the art.
• the inventors thus believe that with a conversion rate initially targeted of 100% at the cell outlet, an increase of 10 to 20% of the available surface area of the cell and an increase in the flow of water vapor of this same order. If necessary, despite aging, it is possible to maintain a conversion rate of the order of 100%, the reduction of this rate then taking place much later.
• the method according to the invention is less expensive; at the most it is necessary to oversize the electrolysis cells with respect to the overall hydrogen production efficiency targeted,
• the regulation according to the invention is made only within the electrolyser and it adjusts locally locally, only the increase in the flow rate of non-hydrogenated water vapor is to be regulated by the user of the electrolyser according to its need (target conversion rate).

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• Chemical & Material Sciences (AREA)
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• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 2010
  • 2010-03-12 FR FR1051782A patent/FR2957360B1/fr not_active Expired - Fee Related
• 2011
  • 2011-03-11 EP EP11707682A patent/EP2545204A1/de not_active Withdrawn
  • 2011-03-11 WO PCT/EP2011/053725 patent/WO2011110676A1/fr active Application Filing
  • 2011-03-11 US US13/634,043 patent/US20130032490A1/en not_active Abandoned
  • 2011-03-11 JP JP2012556535A patent/JP2013522459A/ja active Pending

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