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    • 专利摘要:
    The present invention relates to a reversible system (1) for solid oxide type fuel cell (SOFC) power generation comprising: a fuel cell (SOFC) (2) comprising at least one elementary electrochemical cell with solid oxides each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode; a gas-liquid phase separator (3) connected to the output of the fuel cell; a methanation reactor (4), adapted to implement a methanation reaction, the input of which is connected to the output of the phase separator and the output of which is connected to the input of the fuel cell; a reversible hydrogen storage tank (5) adapted to store hydrogen, the outlet of which is connected to the inlet of the methanation reactor.
    公开号:FR3034570A1
    申请号:FR1552685
    申请日:2015-03-30
    公开日:2016-10-07
    发明作者:Magali Reytier；Le Borgne Isabelle Noirot；Guilhem Roux
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    [0001] FIELD OF THE INVENTION The present invention relates to the field of solid oxide fuel cells (SOFC). It more generally relates to a new power generation system comprising such a battery and a hydrogen storage tank. The invention is particularly applicable with a reversible storage tank of hydrogen, preferably containing hydrides and more preferably metal hydrides, such as MgH 2. Part of the system according to the invention can advantageously be used in reverse mode, with the electrochemical cells constituting an EHT electrolyser, the tank then serving to store the hydrogen produced by the electrolysis of water at high temperature (EHT, or EVHT for electrolysis of water vapor at high temperature, or HTE acronym for "High Temperature Electrolysis", or HTSE acronym for "High Temperature Steam Electrolysis") also with solid oxides (SOEC, acronym for "Solid Oxide") Electrolysis Cell "). PRIOR ART A SOFC fuel cell or an electrolyser EHT generally consists of a stack of elementary patterns (also called SRUs for "Single Repeat Units") each comprising a solid-oxide electrochemical cell consisting of three superimposed layers. on the other anode / electrolyte / cathode, and interconnect plates of metal alloys also called bipolar plates, or interconnectors. The function of the interconnectors is to ensure both the passage of electric current and the circulation of gases in the vicinity of each cell (injected water vapor, hydrogen and oxygen extracted in an EHT electrolyser, injected air and hydrogen and water extracted in a SOFC stack) and to separate the anode and cathode compartments which are the gas circulation compartments on the anode side and the cathode side of the cells respectively.
    [0002] A fuel cell usually gives off a lot of heat because of the oxidation of the hydrogen within it which is a strongly exothermic reaction. Also, it is necessary to cool a fuel cell running on hydrogen.
    [0003] Hydrogen fueled cells operating at relatively low temperatures are typically cooled by a liquid water circuit. This solution is unthinkable for a SOFC battery technology because the operating temperatures of the latter are usually between 700 ° C and 900 ° C.
    [0004] To date, several technical solutions make it possible to respond to this difficulty. The first is to increase the gas flow rates, especially on the oxidizer side, usually air to heat the battery, that is to say to try to balance the temperatures within it. But, this has many disadvantages.
    [0005] Indeed, the high flows that it is necessary to circulate to evacuate the heat by the gases have several adverse impacts on the battery. First of all, when you have to compress a high flow of oxidizer (air), this leads to a significant drop in the efficiency of the battery. Then, the high flow rates lead to stack stack inlet pressure levels which can be prohibitive for the holding of the seals. Finally, a high airflow associated with a low fuel flow to maintain a high electrical efficiency, that is to say a ratio between the electric power produced and the heat output of the incoming gases, can cause imbalances in the air. noticeable pressure between fuel / oxidizer chambers. Therefore, the conventional thermal management solution of this type of high temperature fuel cell is to supply it directly with methane and steam to take advantage of the endothermic reforming reaction occurring in contact with the electrode. cermet based on nickel-zirconia.
    [0006] This solution is adopted naturally when the cell is coupled to the gas distribution network (methane). In addition, the use of cells of the battery whose support is the nickel-zirconia cermet is favorable to the application of this solution. Indeed, with such a support, it is possible to put a sufficient thickness, typically greater than 5001.1m, so that the amount of nickel is sufficient to perform the almost total reforming of methane within the battery. If, for technical and / or economic reasons, it is not possible to directly couple a SOFC fuel cell to a methane distribution network, then we find ourselves in the conventional solution of supplying pure hydrogen with the related disadvantages as mentioned above. Moreover, the operation of a SOFC cell directly supplied with methane generates CO2 carbon dioxide, the rejection of which has an impact on the environment. The patent application US20090291336 describes the use of a methanation reactor coupled to a SOFC fuel cell in order to be able to use kerosene which can not be used as such as fuel by the battery, the kerosene being previously reformed with steam. water in a reforming reactor upstream of that of methanation. The patent application EP 1768207 also describes the use of a methanation reactor coupled to a SOFC fuel cell in order to be able to use ethanol which can not be used as such as fuel by the battery. It is also a matter of enriching the reformed gas only in methane.
    [0007] US Patent 7482078 B2 discloses a system for producing reversible hydrogen by circulating a gaseous fuel containing carbon C and hydrogen C elements, such as methane, through an SOFC fuel cell, a separating device. being arranged at the outlet of the SOFC cell to extract the hydrogen produced at the cell cathode outlet, for the primary purpose of storing it. According to one embodiment, by referring to the references of this patent, there is provided a feedback loop referenced 112 in FIGS. 1A to 1D, to exclusively reinject hydrogen H2 either upstream of the stack referenced 110 (FIGS. 1A, 1C). , 1D) is in a reformer referenced 124 itself upstream of the stack 110. In electrolysis operation mode, inverse to that of the SOFC fuel cell, according to one embodiment, a Sabatier reactor referenced 30 in FIG. 7 is arranged at the anode outlet of the electrolyser referenced 10, for the primary purpose of storing methane produced by the Sabatier reaction in the reactor 30. Still according to this electrolysis mode of operation, a device of FIG. Separation referenced 113 3034570 4 is arranged downstream of the reactor 30 to extract the hydrogen produced in the Sabatier reactor and reinject it exclusively upstream of this reactor 30. There is therefore a need for to improve the electricity generation systems comprising a hydrogen storage tank and a solid oxide fuel cell (SOFC), operating at high temperature, typically between 600 ° C. and 1000 ° C., in particular in order to overcome the disadvantages of thermal management by a high rate of supply of a SOFC cell directly supplied with hydrogen, and when a direct coupling to a methane distribution network is not technically and / or economically feasible, or in particular in order to to overcome the drawbacks of CO2 emissions of SOFC cells fed directly with methane. The object of the invention is to respond at least in part to this need. SUMMARY OF THE INVENTION To this end, the invention relates, in one of its aspects, to a reversible system for producing electricity by solid oxide fuel cell (SOFC) comprising: a fuel cell (SOFC) comprising at least one elemental electrochemical cell with solid oxides each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode; a gas-liquid phase separator connected to the output of the fuel cell; A methanation reactor, adapted to implement a methanation reaction, whose input is connected to the output of the phase separator and the output of which is connected to the input of the fuel cell; a reversible hydrogen storage tank adapted to store hydrogen, the outlet of which is connected to the inlet of the methanation reactor.
    [0008] In other words, the invention consists in supplying hydrogen with a closed loop methanation reactor to an SOFC fuel cell. Hydrogen added from the storage tank is used to compensate for the liquid water that is removed by the gas-liquid separator downstream of the SOFC fuel cell. Thus, thanks to the system according to the invention, it is possible to use 100% of the fuel removed from the tank while circulating all the carbon species closed loop on itself.
    [0009] In other words, with a system according to the invention, not only is it overcome the disadvantages of a SOFC battery directly supplied with hydrogen, in particular those related to the need for supply in high flow rates oxidizer, and without use a methane distribution network, but in addition, there is no release of CO 5 or CO2 out of the pile, as according to the state of the art, since here the carbon species circulate in a loop closed. With regard to the actual operation of the system, in the range of temperatures preferably between 700 and 900 ° C for the fuel cell, the reforming reaction within the cell is endothermic, whereas the oxidation of Hydrogen is exothermic. The choice of the incoming methane flow rate and the operating point (I-U) of the cell makes it possible to regulate the overall exothermicity of the cell, or even an autothermal operation. A high methane flow rate associated with a high current density can lead to a high thermal gradient within the cell, especially in the cell plane between the inlet and the outlet. Those skilled in the art can apply known design solutions to homogenize the temperature within the stack. The advantages of the system according to the invention are numerous among which may be mentioned: - the realization of the reforming reaction and its inverse, methanation both within the same system and within independent components (reactors) allows to have a cold source and a hot source well separate while being connected to one another. Thus, rather than operating a SOFC hydrogen battery as conventionally, which can generate a highly exothermic reaction for which it is still difficult to evacuate and enhance the heat by gases, the SOFC stack according to the invention can to be in quasi-isothermal nominal operation and the hot source to be valorized is provided by the methanation reactor. This heat is then more controllable through the cooling circuit of the methanation reactor, that is to say via a dedicated metal fluid circuit. This avoids the risk of losing the joints of the high-volume battery, and the risk of breakage of fragile cells as in a state-of-the-art system where the SOFC cell is directly supplied with hydrogen; the separation of the thermal functions in a system according to the invention, associated with 100% use of the fuel discharged from the reservoir via a gas circulation loop closed on itself, offers a large operating range and therefore a large operating flexibility for a SOFC battery. Indeed: the current density produced by the cell is dependent on the hydrogen flow rate supplied by the tank; The total flow rate of the gases circulating in the system, in particular the flow of methane, controls the cold source within the cell and especially the valuable heat source released by the methanation reactor; the difference between these two flow rates (total flow in the closed loop, flow of hydrogen from the reservoir) corresponds to the rate of utilization of the fuel which effectively crosses the stack with respect to that actually consumed and thus out of the reservoir. This utilization rate makes it possible to control the heat supplied by the system for a given battery power. for a flow of hydrogen out of the given reservoir and therefore for a given current density, the lower the total circulating hydrogen utilization rate, the more the battery will produce electricity rather than heat, and therefore with a better yield and more the amount of heat produced by the methanation reactor is important. Thus, a system according to the invention overcomes the disadvantages of other SOFC battery systems according to the state of the art, in which the high yields are necessarily achieved with high utilization rates, which can damage the battery and wherein a portion of fuel is generally burnt at the output to limit CO emissions or to generate the required heat; the operating control of the system according to the invention can also be carried out by modifying the temperature of the methanation reactor, which modifies the quantity of methane CH4 formed and therefore the ratio between hydrogen and methane (H2 / CH4) at the inlet of stack; the electric power produced by the battery can be decoupled from the available heat available within the system by adjusting the fuel utilization rate with respect to the flow rate of H2 leaving the tank; over-stoichiometry of hydrogen makes it possible to reduce the heat evolved by the methanation in favor of greater exothermicity for the cell. It is thus possible to envisage a better management of the degradation over time of the SOFC stack, by compensating for its decrease in performance for a higher temperature, or by optimizing the preheating of the stack input gases by a heat exchange between the entrance and exit; the thermal management of the SOFC cell according to the invention at a maximum temperature of 850 ° C. offers a possible operation at a higher inlet temperature (800 ° C. instead of 700 ° C.), conferring on it an electrical efficiency well better than according to the state of the art. Indeed, the difficulty of cooling pure hydrogen in a SOFC battery system according to the state of the art generally imposes a maximum inlet temperature at 700 ° C; the air flow only serves to supply the oxidant necessary for the SOFC 10 cell according to the invention. In other words, it does not have an important cooling function as in state-of-the-art SOFC battery systems supplied directly with hydrogen, ie without closed loop circulation of carbonaceous species and without methanation reactor according to the invention. invention; the (re) circulation of the fuel is simple to carry out in a system according to the invention; because the circulating gas mixtures are dry, since all the water leaving the cell is removed by condensation. The recirculating auxiliaries (pumps) are then less expensive than in the systems according to the state of the art. The water required for internal reforming is provided by the methanation reaction itself. The invention thus also differs from conventional SOFC battery systems in which the water formed by the cell is used to reform the fuel internally, which imposes recirculation difficult to achieve water vapor. By "reversible In the context of the invention, it is meant that the SOFC fuel cell can be used as an EHT electrolyser in electrolysis operation mode, the reverse of that of the battery, the anode (s) of the SOFC stack then playing the role of cathode (s) of the electrolyser.
    [0010] In operating mode as the SOFC fuel cell according to the invention, there is no storage of hydrogen in the tank feeding the methanation reactor. In addition, the heat generated by the methanation reaction can be used for the system, in particular by being brought to the hydrogen storage tank to desorb it.
    [0011] In the EHT electrolysis operating mode according to the invention, no methanation reaction is carried out and the reservoir is used solely to store the hydrogen produced by the electrolysis. In addition, the heat generated by the storage of hydrogen can be used for the system, in particular by being supplied to the steam generator upstream of the electrolyser EHT. According to an advantageous embodiment, the cell is a stacked reactor of elementary electrochemical cells of SOFC type each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, and a plurality electrical and fluidic interconnectors each arranged between two adjacent elementary cells with one of its faces in electrical contact with the cathode of one of the two elementary cells and the other of its faces in electrical contact with the anode of the other of the two elementary cells.
    [0012] Each anode of the cell consists of an yttria stabilized nickel-zirconia cermet (Ni-YSZ). The methanation reactor preferably comprises a solid methanation catalyst based on nickel (Ni) supported by a zirconium oxide (ZrO 2), or based on nickel (Ni) supported by an aluminum oxide (Al 2 O 3), or bimetallic nickel-based (Ni) and iron (Fe) supported by an aluminum oxide (Al 2 O 3), preferably Ni-Fe / Al 2 O 3, or nickel-based (Ni) supported by mixed oxides of Cerium (Ce) and zirconium, preferably Ceo 72Zr0 2802. The hydrogen reservoir may be a storage tank in solid form, preferably containing metal hydrides, preferably magnesium hydrides (MgH 2) or a storage tank. in the form of hydrogen gas, preferably compressed between 350 and 700 bar. Advantageously, the system comprises at least a first heat exchanger adapted to preheat the fuel from the methanation reactor at the fuel cell inlet from the heat generated by the gases leaving the fuel cell. Advantageously, the system comprises at least one second heat exchanger, adapted to preheat the gases from the hydrogen reservoir and / or gas-liquid phase separator at the methanation reactor inlet, from the heat released by the gases. at the output of the battery after the exchanger.
    [0013] The invention also relates to a method of continuous operation of the reversible system described above, comprising the following simultaneous steps: desorption of hydrogen from the reservoir to feed the inlet of the methanation reactor; - operation of the methanation reactor; operation of the fuel cell in an input temperature range of 700 ° C to 800 ° C; operation of the gas-liquid separator so as to separate the water from the gas mixture consisting of hydrogen (H 2), carbon monoxide (CO) and carbon dioxide (CO 2), at the outlet of the fuel cell; fuel, a process in which the molar flow rate of hydrogen at the outlet of the tank which feeds the inlet of the methanation reactor is substantially equal to that oxidized in water in the fuel cell and condensed in the separator. Preferably, the hydrogen from the reservoir is mixed with the mixture of gases consisting of hydrogen (H2) carbon monoxide (CO) and carbon dioxide (CO2), coming from the fuel cell, before their injection into the methanation reactor. The difference between the circulating hydrogen flow rate and the hydrogen flow rate out of the reservoir allows the system to operate more flexibly, in particular for flexibility in the electrical power produced, without requiring the battery to use the fuel too much. More preferably, the flow of methane (CH4) is adjusted at the outlet of the methanation reactor 20 and the nominal current-voltage operating point (I, U) of the fuel cell (SOFC) is selected so as to obtain a steady state. autothermal operation of the fuel cell (SOFC). According to yet another advantageous variant, at least a portion of the heat generated by the methanation reactor is recovered and supplied to the hydrogen reservoir in order to desorb the hydrogen. If it is a hydrogen gas tank under pressure, this heat at about 400 ° C can be upgraded to other forms of cogeneration. The invention finally relates to the use of a part of the reversible system described above for producing and storing hydrogen at high temperature, in which: the cell (s) is (are) used in as an electrolysis cell (s) by constituting a high temperature electrolyser (EHT); The outlet of the electrolyser EHT is connected to the hydrogen storage tank. - If it is a hydrogen reservoir in the form of hydrides, the heat released to the absorption is used to vaporize the water needed by the electrolyser.
    [0014] In this use, the second heat exchanger is preferably adapted to preheat the water vapor from the steam generator at the inlet of the EHT electrolyser from the heat released by the hydrogen and / or the water vapor. at the output of the electrolyser EHT. DETAILED DESCRIPTION Further advantages and features of the invention will become more apparent upon reading the detailed description of exemplary embodiments of the invention, given by way of nonlimiting illustration and with reference to the following figures among which: Figure 1 is a schematic view of the principle of the SOFC fuel cell power generation system according to the invention; FIG. 2 is a schematic view of an exemplary SOFC fuel cell power generation system according to the invention; FIG. 3 is a schematic view and is a schematic view of an example of electrolysis production of EHT water and hydrogen storage product, implementing in reverse mode part of the system of Figure 2.
    [0015] Throughout the present application, the terms "inlet", "outlet" "downstream" and "upstream" are to be understood with reference to the direction of closed-loop circulation of gases through respectively the SOFC fuel cell and the methanation reactor. In the EHT electrolyser mode, these same terms are to be understood with reference to the direction of circulation of the water vapor and the air supplying the electrolyser, and of the hydrogen and oxygen produced therein. It is also specified that the fuel cell described is of solid oxide type (SOFC), operating at high temperature. Thus, all the constituents (anode / electrolyte / cathode) of an electrolysis cell are ceramics.
    [0016] Typically, and preferably, the characteristics of an SOFC elemental electrochemical cell suitable for a battery according to the invention, of the anode support cell type (ASC), may be those indicated as follows. in Table 1 below. TABLE 1 Electrochemical cell Unit Value Anode Constituent material Ni-YSZ Jim thickness> 500 Thermal conductivity w in-i K-1 13.1 Electrical conductivity 1-2-1 m-1 105 Porosity 0.37 Permeability m2 10-13 Tortuosity 4 Current Density A.111-2 5300 Cathode Constituent Material LSM Thickness ûm 20 Thermal Conductivity w in-i K-1 9.6 Electrical Conductivity 1-2-1 m-1 1 104 Porosity 0.37 Permeability m2 10-13 Tortuosity 4 Current Density A.111-2 2000 Electrolyte Constituent Material YSZ Thickness ûm Resistivity f2 m 0.42 A SOFC fuel cell suitable for the invention is preferably an elementary electrochemical cell reactor C1, C2, of oxide type solid (SOFC) stacked alternately with interconnectors. Each cell consists of a cathode and an anode, between which is disposed an electrolyte.
    [0017] So far, SOFC fuel cell systems operate at high temperatures either with a battery powered by pure hydrogen or directly with methane and water vapor. The first conventional way of supplying pure hydrogen has the major cooling constraint necessary due to the exothermic reaction of hydrogen oxidation. The solutions to achieve this have many disadvantages.
    [0018] The second conventional method for feeding methane and water vapor makes it possible to overcome this major constraint because by using a type of nickel-zirconia cermet anode, it makes good use of the endothermic reforming reaction at this anode. If this second path appears natural, when the SOFC 5 fuel cell can be easily coupled to a methane distribution network, it can not be retained if it is not technically and / or economically feasible. Thus, there still remains the major constraint of cooling a SOFC fuel cell when the latter can only be fed from a hydrogen reservoir, which concerns a large number of applications.
    [0019] Also, the inventors have judiciously thought of arranging a methanation reactor between an SOFC fuel cell and a hydrogen storage tank. The SOFC cell can then be operated with CH4 methane produced by hydrogenation in the methanation reactor with the major advantage of circulating the carbon species transformed in both the cell and the methanation reactor in a closed loop. A system 1 according to the invention implementing such circulation of carbon species in a closed loop is shown schematically in FIG. 1. Thus, the system 1 respectively comprises a closed loop from upstream to downstream, a SOFC 2 fuel cell, a condensation / separation device 3, a methanation reactor 4. Thus, the inlet of the SOFC 2 cell is connected to the outlet of the methanation reactor 4. The inlet of the methanation reactor 4 is itself connected to the outlet of the SOFC stack 2. The condensation / separation device 3 is connected downstream to the outlet of the stack 2 and upstream to the methanation reactor 4. In addition, the inlet of the methanation tank 4 is connected to the output of a reversible storage tank of hydrogen 5. As shown in Figure 1, the heat that emerges from the methanation reactor can be enhanced. In particular, it can advantageously be used in part in the loop of the system according to the invention, as described below. Prior to its nominal operation, the system 1 operates in the following manner.
    [0020] 3034570 13 Battery 2 runs at low current and low utilization rate in pure hydrogen. The unconsumed hydrogen circulates in a closed loop within the system 1. The hydrogen consumed in the loop is replaced by hydrogen from the tank 5 and produces water which is condensed.
    [0021] Upstream of the methanation reactor 4, a quantity of CO2 is introduced in stages so as to reach the fixed quantity, that is to say at a value of flow rate of H2 divided by 4. During the introduction of this amount of CO2 in steps, the stack 2 then receives a mixture of CH4 + H20 + H2 until no longer receive hydrogen at the head.
    [0022] The current is then gradually increased stepwise so as to compensate for the endothermicity of the CH4 internal reforming. Once the target amount of CO2 is introduced, the CO2 injection is stopped and the amount of carbon rotates within the closed-loop system. The nominal closed-loop operation of a system 1 in the SOFC stack mode according to the invention is as follows. The hydrogen delivered by the tank 5 and the required amount of CO2 carbon dioxide initially introduced at the inlet of the methanation reactor 4 produce methane and water (CH 4 + H 2 O) with, where appropriate, hydrogen overhead. stochiometry from the reservoir 5.
    [0023] Indeed, in the reactor 4 containing a solid catalyst of the methanation reaction, the following reactions are possible in the temperature range of 400 to 500 ° C. A single hydrogenation reaction of CO 2 can take place according to the following equation: CO2 + 4H 2 CH 4 + 21/20 (1) It can also occur both a hydrogenation reaction of CO2 (2) and a so-called Reverse Water Gas Shift reaction (3) according to the following equations: CO 2 + H 2 CO + H 2 O (2) CO + 3H 2 CH 4 + H 2 O (3) It goes without saying that one can have in the context of the invention a methanation total or not, within the reactor 4. In the case where the methanation is not total, then it remains hydrogen at its output, and the performance of the battery is increased by the presence of this hydrogen, but the thermal management targeted by the invention will be less than in the case of a total methanation. The CH 4 + H 2 O + (H 2) gas mixture from the reactor 4 is then introduced into the fuel cell inlet 2. The reactions (1), (2) and (3) then occur within the cell 2 reverse. Thus, there is a reforming reaction transforming methane and water into hydrogen and carbon monoxide (H2 + CO), fuel usable by the battery. The electrochemical operation of the cell 2 leads to the oxidation of these species to water and carbon dioxide (H 2 O + CO 2), the cell being supplied simultaneously with oxidant which is supplied by air or oxygen. As indicated above, the battery 2 uses a cell (s) whose support (anode) is a Ni-YSZ-based cermet, which allows a total reforming of the CH4 methane in the cell. . Thus, the gas at the outlet of the stack consists of a mixture of hydrogen H2 and CO not used within the cell as well as CO2 and H2O formed by the cell. It goes without saying that one can also have in the context of the invention a reforming that is not total within the stack 2. In the latter case, only the performance of the stack 2 are partially affected by potentially less hydrogen in the presence and dilution with methane CH4.
    [0024] At the outlet of the cell 2, the water is removed by condensation within the condensation / separation device 3. At the outlet of the device 3, the mixture of dry exit gas is then re-injected into the methanation reactor and it is supplemented with hydrogen coming from the tank 5. According to the invention, the molar flow rate of hydrogen coming from the tank 5 corresponds to that which is oxidized in water within the cell 2, and therefore to that of the cell. condensed water and evacuated by the device 3. The recirculation of dry gas output being total, the flow flowing within the cell 2 may be much greater than that from the tank 5. The rate of use of hydrogen within the system 1 is 100% (no hydrogen lost or burned).
    [0025] Thus, the system according to the invention which has just been described allows the use of carbon species in a closed circuit in their entirety. There is therefore neither CO rejection nor CO2 discharge at the stack outlet 2 at rated speed.
    [0026] In order to demonstrate the strong interest presented by the invention, the inventors have dimensioned a system with a reversible storage tank for hydrogen based on MgH 2 magnesium hydrides. This type of storage is advantageous because it makes it possible to use at least a portion of the heat generated by the methanation reactor 4 by coupling the latter to the tank 5. Such a tank 5 containing hydrides MgH, typically operates at a temperature of the order of 380 ° C. The desorption of hydrogen from the tank 5 to feed the fuel cell 2 requires the supply of heat which is therefore advantageously provided by the methanation reactor 4. In addition, the absorption of hydrogen in the tank 5 is exothermic. and may make it possible to vaporize the water required when a part of the system according to the invention is used in the reverse mode of electrolysis of water (EHT). The inventors have thus made different examples according to the invention and according to the state of the art, for comparison both for operation in SOFC battery mode and in EHT electrolyser mode. It should be noted that in the tables below, values have been rounded up. Examples 1 and 2 according to the invention: The system 1 according to the invention comprises the essential elements already described. In addition, as illustrated in Figure 2, the system 1 according to the invention firstly comprises a heat exchanger 6 at high temperature (HT exchanger in Figure 2). This exchanger 6 is adapted to preheat fuel gas input 2 from the methanation reactor 4, at about 700 ° C, from the heat released by the gas output of the fuel cell. The system 1 further comprises another heat exchanger 7 at lower temperature (LV exchanger in Figure 2). This exchanger 7 is adapted to preheat the gases coming from the hydrogen reservoir and / or gas-liquid phase separator 3 from the heat generated by the gases leaving the high exchanger at the inlet of the methanation reactor 4. temperature.
    [0027] An air compressor 8 is also provided for supplying air as an oxidant to the fuel cell 2. The air supplying the battery 2 is heated by depleted air at the cell outlet 2 by means of a other exchanger 9.
    [0028] Finally, in the closed-loop circuit, a circulation pump 10 is arranged to circulate the gas mixtures of the fuel cell 2 to the methanation reactor 4. Alternatively, as illustrated in FIG. provide a mixture between the dry gas mixture (H2 + CO + CO2) from the condenser 3 and the hydrogen H2 delivered by the tank 5 upstream of the inlet of the methanation reactor 4. Such a mixture can be produced by any known gas mixer 11. The embodiment of the battery according to the invention and the nominal operating conditions are as follows. The SOFC 2 fuel cell comprises a stack of a number equal to 50 cells of 100 cm 2 each. Each cell comprises an anode consisting of a Ni-YSZ cermet at least 5001.1m thick allowing total internal reforming from 700 ° C. The inlet temperature of the cell 2 is 700 ° C. (Example 1) or 800 ° C. (Example 2).
    [0029] The maximum temperature at the outlet of the cell 2 is 850 ° C., regardless of the inlet temperature. The output flow rate of the hydrogen storage tank 5 is 1 Nm 2 / h for a current density coming out of the cell 2 of the order of 0.5 A / cm 2. At this hydrogen flow rate of 1 Nm 2 / h, the heat to be supplied to the tank 5 is of the order of 1kW.
    [0030] The air supply rate of the cell 2 is of the order of 12 to 30 Nml / min / cm 2. According to the invention, the flow rate of CO2 circulating in the closed loop between the cell 2 and the methanation reactor 4 is adjusted to the flow rate of circulating hydrogen. Thus, the CO2 flow rate is equal to the H2 flow divided by 4 times the fuel utilization rate from the methanation reactor.
    [0031] 3034570 17 The cold power is available without electricity, that is to say that the cooling is carried out only with industrial water available and therefore without having to use a source of cold production supplied with electricity. The yields of the auxiliaries of the system are as follows: 5 - efficiency of the electric converter of the current produced by the battery 2: 95% - efficiency of the compressors 9, 10: 50% - losses of loads on the supply air sweep of stack 2 estimated at 10.8mb ar / nml / min / cm2. Comparative Example: An SOFC 2 fuel cell fed directly by a hydrogen reservoir 5 according to the state of the art is considered. In other words, a SOFC 2 cell conventionally operates with pure hydrogen as a fuel supplied directly from a tank 5. The air as an oxidant is also compressed by the same type of air compressor 9. The conditions are the same as those of the examples according to the invention, with the exception of the air supply rate of the stack 2 which is of the order of 48 Nmliminicm2 for a current of 0.5A / cm 2 if the battery is in H2 pure. The balance sheet of the calculations is shown in Table 2 below.
    [0032] EXAMPLE 2 System Example Example 1 According to Example 2 According to Comparative Conditions the invention the invention (Temperature in (inlet stack input temperature equal to 700 ° C.) equal to 800 ° C.) Flow rate H2 (m 3 / s) 1 1 1 Air flow (NmUmin / cmm2) 48 30 30 Number of cells 50 50 50 of stack 2 Power of air compressor 9 (W) 375 160 160 Air compressor overpressure 9 (mbar) 500 325 325 Utilization rate 60 53 53 fuel (%) CO2 flow (mol / s) 0 5.85 * 10-3 5.85 * 10-3 Desorption power H2 1000 0 0 of the tank 5 (W) Lower heating value (HP), 3000 3000 3000 H2 (W) Lack of electrical overheating (W) 0 0 227 Condenser cold power 3 825 1020.77 768 (W) Power delivered equal to U * I (W) 2011 1727 1966 Output temperature (° C) 846 747 792 Yield 0.46 0.55 0.58 It can be seen from Table 2 that the efficiency of a SOFC 2 cell directly supplied with pure hydrogen according to the state of the art is 46%. There is also an electrical consumption for the air compressors 9 and for the hydrogen desorption of the tank 5 which is higher for a SOFC battery system according to the state of the art (comparative example) compared to a system according to the invention (Examples 1 and 2).
    [0033] In addition, the nominal operating mode in a system according to the state of the art requires a temperature difference between the input and the output of the battery 2 of the order of 150 ° C. In the case of the battery mode according to the invention, the efficiency of the system according to the invention is 55% at 700 ° C. and 58% at 800 ° C., ie a yield gain of more than 10% compared with a conventional system according to the state of the art with direct supply of a SOFC pure hydrogen cell from a hydride storage tank. The heat generated by the methanation reactor 4 is then sufficient to desorb the hydrogen from the tank 5. The cell 2 undergoes only a gradient of 50 ° C. to 700 ° C. and its operation is almost autothermal at 800 ° C. . The inventors have also made an analysis on the EHT electrolyser mode to produce and store hydrogen at high temperature. Thus, in this mode, the stack of cells according to the invention is used as an electrolysis cell (s) by constituting a high temperature electrolyser (EHT) 2, as illustrated in FIG. the electrolyser EHT 2 is connected to the hydrogen storage tank 5. The realization of the electrolyser EHT according to the invention and the nominal operating conditions are as follows.
    [0034] The electrolyser EHT 2 comprises a stack of a number equal to 50 cells of 100 cm 2 each. Each cell comprises a cathode consisting of a Ni-YSZ cermet at least 5001.1m thick. The operation of the electrolyser 2 is autothermal at around 700 ° C. The rate of use of the water vapor injected into the electrolyser 2 is of the order of 75%. The heat delivered by the tank 5 and supplied to the electrolyser 2 is of the order of 1 kW for a hydrogen flow rate of the order of 1 Nm 2 / h of hydrogen. The cold power is here also available without electricity. The yields of the auxiliaries of the system are as follows: efficiency of the electrical converter of the current supplied the electrolyser 2: 95% efficiency of the compressors 9, 10: 50%.
    [0035] TABLE 3 System Example according to the invention Conditions (Electrolyser operating temperature equal to 700 ° C.) Flow rate H2 (m3 / s) 2.91 Number of cells 50 electrolyser 2 Compressor power 15 from H2 to 12 bars (W ) 683 Water vapor utilization rate (%) 75 Required power for superheating of water vapor 155 (W) Hydride adsorption power (W) 2907 Lower heating value (HHV) of Hz (W) 8720 Lack of electrical overheating (W) 0 Condenser cold power 3 949 (W) Power to be supplied equal to U * I (W) 9798 Efficiency 0.82 With the above data, a system according to the invention whose operation is reversible in SOFC fuel cell mode and in electrolyser mode 5 EHT from a reversible storage tank / destocking of hydrogen has a complete yield, ie with return to available electricity, of the order of 48% (equal at Table 2 yield of 0.58 multiplied by the performance of Table 3 gal to 82%), which to the inventors' knowledge is unmatched. The invention is not limited to the examples which have just been described; in particular, characteristics of the illustrated examples can be combined with non-illustrated variants. Other variants and improvements of the invention may be made without departing from the scope of the invention.
    [0036] In particular, the variation of the outlet flow rate of the reversible hydrogen storage tank allowing a power flexibility of the SOFC fuel cell according to the invention has not been illustrated. Also, if the storage tank studied in the examples illustrated according to the invention is of the type containing MgH 2 magnesium hydrides, it is quite possible to envisage other types of hydride or more generally all types of storage under solid form, in liquid or gaseous form. As already mentioned, the largely hydrogenation reaction of CO2 and closed loop CO within the methanation reactor is exothermic and takes place in a temperature range of about 400 to 500 ° C. This heat thus advantageously makes it possible to preheat the inlet gases of the methanation reactor at around 400 ° C., that is to say either the hydrogen (H2) coming from the tank or the mixture of H2 + CO gas. + CO2 from the phase separator that allows condensation. It goes without saying that one can seek to recover the rest of the heat released by the methanation reactor.
    [0037] With regard to the methanation reactions within the reactor, the catalysts used may be based on nickel supported by a zirconium oxide (ZrO 2), or based on nickel (Ni) supported by an aluminum oxide (Al 2 O 3 ). The publication [1] has highlighted the important catalytic activity for a nickel-based catalyst (Ni) supported by mixed cerium (Ce) and zirconium oxides of the formula Ceo 72Zr0 2802. Similarly, the publication [ 2] has shown, for a methanation under pressure of 30 bars, the excellent catalytic activity of a nickel-based (Ni) and iron (Fe) supported bimetallic catalyst supported by an aluminum oxide (Al 2 O 3) of formula Ni -Fe / y-A1203. Several types of reactors already tested can be considered to implement methanation.
    [0038] First of all, fixed bed reactors in which the solid catalyst is integrated in the form of grains or pellets. The disadvantage of this type of reactor is the thermal management difficult to achieve for exothermic reactions such as methanation. There are also reactors with structured channels such as multitubular reactors, monolithic reactors and plate reactors in which the solid catalyst is generally deposited as a coating in the reactive channels. These reactors are well suited for a methanation reaction that requires good thermal management. They are usually more expensive. Finally, the fluidized bed or driven type reactors in which the catalyst to be fluidized is in powder form. These reactors are well suited for reactions with very large reagent volumes. In addition, the fluidization of the catalyst allows a very good thermal homogenization of the reagent mixture in the reactor and therefore better thermal control.
    [0039] References cited [1]: Fabien Ocampo et al, "Methanation of carbon dioxide over nickel-based Ce0.72Zr0.2802 mixed oxide catalysts prepared by sol-gel method", Journal of Applied Catalysis A: General 369 (2009) 90-96; [2]: Dayan Tiang et al, "Bimetallic Ni-Fe total-methanation catalyst for the production of natural gas substitutes under high pressure", Journal of Fuel 104 (2013) 224-229. 10
    权利要求:
    Claims (13)
    [0001]
    REVENDICATIONS1. A reversible solid oxide type fuel cell (SOFC) power generation system (1) comprising: - a fuel cell (SOFC) (2) comprising at least one elementary solid oxide electrochemical cell each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode; a gas-liquid phase separator (3) connected to the output of the fuel cell; - A methanation reactor (4), adapted to implement a methanation reaction, whose input is connected to the output of the phase separator and whose output is connected to the fuel cell inlet; a reversible hydrogen storage tank (5) adapted to store hydrogen, the outlet of which is connected to the inlet of the methanation reactor.
    [0002]
    2. System (1) reversible according to claim 1, the cell being a stacked reactor of elementary electrochemical cells SOFC type each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode , and a plurality of electrical and fluidic interconnectors each arranged between two adjacent elementary cells with one of its faces in electrical contact with the cathode of one of the two elementary cells and the other of its faces in electrical contact with the anode of the other of the two elementary cells
    [0003]
    3. System (1) reversible according to claim 1 or 2, each anode of the stack consisting of an yttria-stabilized nickel-zirconia cermet (Ni-YSZ).
    [0004]
    4. System (1) reversible according to one of the preceding claims, the methanation reactor comprising a solid methanation catalyst being based on nickel (Ni) supported by a zirconium oxide (Zr02), or nickel-based (Ni ) supported by an aluminum oxide (Al 2 O 3), or bimetallic base based on nickel (Ni) and iron (Fe) supported by an aluminum oxide (Al 2 O 3), preferably Ni-Fe / Al 2 O 3, or nickel base (Ni) supported by mixed oxides of cerium (Ce) and zirconium, preferably Ce0.72Zr0.2802. 3034570 25
    [0005]
    5. System (1) reversible according to one of the preceding claims, the hydrogen reservoir (5) being a storage tank in solid form, preferably containing metal hydrides, preferably magnesium hydrides (MgH2) or a reservoir storage medium in the form of hydrogen gas, preferably compressed between 350 and 700 bar.
    [0006]
    6. System (1) reversible according to one of the preceding claims, comprising at least a first heat exchanger (6), adapted to preheat fuel cell input gases from the methanation reactor from the heat released by the gases leaving the fuel cell. 10
    [0007]
    7. System (1) reversible according to one of the preceding claims, comprising at least a second heat exchanger (7), adapted to preheat at the inlet of the methanation reactor gases from the hydrogen reservoir and / or phase separator gas-liquid, from the heat released by the gases leaving the stack after the exchanger (6). 15
    [0008]
    8. Process for continuous operation of the reversible system according to one of the preceding claims, comprising the following simultaneous steps: desorption of hydrogen from the tank (5) to feed the inlet of the methanation reactor; operation of the methanation reactor (4); Operation of the fuel cell (2) in an input temperature range of 700 ° C to 800 ° C; operation of the gas-liquid separator (3) so as to separate the water from the gas mixture constituted by hydrogen (H2) of carbon monoxide (CO) and carbon dioxide (CO2), at the exit of the fuel cell, in which the molar flow rate of hydrogen at the outlet of the tank which feeds the inlet of the methanation reactor is substantially equal to that oxidized in water in the fuel cell and condensed in the separator.
    [0009]
    9. Operating method according to claim 8, wherein the hydrogen (1) from the reservoir is mixed with the mixture of gas mixture consisting of hydrogen (2) (H 2) of carbon monoxide (CO). and carbon dioxide (CO2) from the fuel cell prior to injection into the methanation reactor. 3034570 26
    [0010]
    10. The operating method according to claim 8 or 9, wherein the flow rate of methane (CH4) is adjusted at the outlet of the methanation reactor and the nominal running-voltage operating point (I, U) of the fuel cell is selected. (SOFC) so as to obtain an autothermal operating mode of the fuel cell (SOFC). 5
    [0011]
    11. The method of operation according to one of claims 8 to 10, wherein is recovered at least a portion of the heat generated by the methanation reactor and is supplied to the hydrogen reservoir to desorb hydrogen.
    [0012]
    12. Use of a part of the reversible system according to one of claims 1 to 7 for producing and storing hydrogen at high temperature, wherein: - the cell (s) is (are) set operates as an electrolysis cell (s) by constituting a high temperature electrolyser (EHT); the output of the electrolyser EHT is connected to the hydrogen storage tank. 15
    [0013]
    13. Use according to claim 12 in combination with claim 7 of the system, the second heat exchanger being adapted to preheat water vapor from the heat released by hydrogen and / or the water entering the electrolyser EHT. water vapor at the outlet of the electrolyser EHT.
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    同族专利:
    公开号 | 公开日
    EP3278391A1|2018-02-07|
    WO2016156374A1|2016-10-06|
    FR3034570B1|2019-06-28|
    US10608271B2|2020-03-31|
    JP6615220B2|2019-12-04|
    CA2980664A1|2016-10-06|
    US20180115003A1|2018-04-26|
    JP2018519617A|2018-07-19|
    CA2980664C|2019-05-28|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1552685A|FR3034570B1|2015-03-30|2015-03-30|SOFC FUEL CELL ELECTRICITY GENERATION SYSTEM WITH CIRCULATION OF CLOSED LOOP CARBON SPECIES|
    FR1552685|2015-03-30|FR1552685A| FR3034570B1|2015-03-30|2015-03-30|SOFC FUEL CELL ELECTRICITY GENERATION SYSTEM WITH CIRCULATION OF CLOSED LOOP CARBON SPECIES|
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    CA2980664A| CA2980664C|2015-03-30|2016-03-30|Sofc-based system for generating electricity with closed-loop circulation of carbonated species|
    EP16715271.9A| EP3278391A1|2015-03-30|2016-03-30|Sofc-based system for generating electricity with closed-loop circulation of carbonated species|
    JP2017551257A| JP6615220B2|2015-03-30|2016-03-30|SOFC system for power generation by closed-loop circulation of carbonate species|
    US15/562,614| US10608271B2|2015-03-30|2016-03-30|SOFC-based system for generating electricity with closed-loop circulation of carbonated species|
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