Cell stack module, failure detection system of cell stack, and failure detection method of cell stack

Abstract

To appropriately detect the failure of a cell stack.SOLUTION: The cell stack module comprises a cell stack 1 including a plurality of unit electrolytic cells 10, a cooler 43, and a moisture detector 44. The feed gas to be fed into the cell stack is fed into a fuel chamber and includes first feed gas including fuel gas and specific gas and second feed gas to be fed into an air chamber. At least a steam generating condition which is a condition that at least one of conditions that hydrogen is generated by the electrolysis of fuel gas and specific gas includes hydrogen, and at least one of conditions that oxygen is generated by the electrolysis of fuel gas and the second feed gas includes oxygen, are satisfied, and a steam containing condition that the fuel das includes steam, are satisfied. The cooler is disposed on the downstream side of an object chamber out of the fuel chamber and the air chamber from which steam is not discharged during a normal operation, and the moisture detector is disposed on the inside or downstream side of the cooler.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cell stack module including a solid oxide electrolysis cell, a cell stack failure detection system, and a cell stack failure detection method. [Background technology]

[0002] Patent Document 1 describes a method for detecting a fault in a cell stack equipped with solid oxide fuel cells. Specifically, the open circuit voltage of the cell stack is monitored, and if a drop in the voltage value is detected, it is determined that the gas sealing performance of the cell stack has decreased, thereby detecting a fault. This fault detection method can also be applied to cell stacks equipped with solid oxide electrolysis cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 05791070 Summary of the Invention

[0004] However, the failure detection method of Patent Document 1 may not be able to properly detect cell stack failures. Specifically, the open-circuit voltage of a cell stack varies for each cell stack depending on its temperature, pressure, manufacturing variations, and deterioration level. Therefore, the open-circuit voltage of each cell stack is typically measured in advance in a certain evaluation environment to obtain an accurate open-circuit voltage. However, when a system including a cell stack is constructed, the evaluation environment changes compared to the case of a single cell stack, resulting in a change in the open-circuit voltage. Therefore, if control is performed within the system based on the open-circuit voltage, new measurements are required. Generally, the electrolytic cell included in a cell stack is composed of multiple electrolytic unit cells, and gas sealing is ensured for each electrolytic unit cell. Therefore, when a failure occurs around a single electrolytic unit cell, a decrease in the open-circuit voltage due to the failure can be detected by measuring the open-circuit voltage of each electrolytic unit cell to detect the decrease in voltage value. However, this requires connecting voltage wires to all of the electrolytic unit cells included in the cell stack, which significantly increases the number of steps required. On the other hand, in a method of measuring the open circuit voltages of a plurality of electrolytic single cells collectively (collectively), the amount (rate) of decrease in open circuit voltage due to the above-mentioned failure is relatively small, making it extremely difficult to distinguish it from fluctuations in open circuit voltage caused by the above-mentioned "temperature," "pressure," "variation in manufacturing," and "degree of deterioration" of the cell stack. Therefore, the failure detection method of Patent Document 1 can detect a type of failure in which the amount of decrease in open circuit voltage is relatively large (for example, a failure in which the gas sealing performance is reduced around the majority of the electrolytic single cells), but has the problem of not being able to appropriately detect a type of failure in which the amount of decrease in open circuit voltage is relatively small (for example, a failure in which the gas sealing performance is reduced around one or several electrolytic single cells).

[0005] The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide a technique that can appropriately detect a fault in a cell stack.

[0006] The cell stack module according to the present invention comprises: a cell stack (1) including a plurality of solid oxide electrolysis unit cells (10), each of which includes a solid electrolyte layer (12), an air electrode (14) stacked on the front side of the solid electrolyte layer, and a fuel electrode (16) stacked on the back side of the solid electrolyte layer; a cooler (133, 43) for cooling the gas passing through it; a moisture detector (134, 44) for detecting moisture; Equipped with. The supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber (Sf) which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber (Sa) which is a space on the air electrode side, the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that satisfy at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are defined as the steam production conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, the cooler is disposed downstream of a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; The moisture detector is located within or downstream of the cooler.

[0007] This cell stack module is configured to detect a cell stack failure when at least one of the water vapor containing condition and the water vapor generating condition is satisfied. Specifically, in this cell stack module, a cooler is disposed downstream of the target chamber (the fuel chamber or air chamber of the cell stack from which water vapor is not discharged during normal operation), and a moisture detector is disposed inside or downstream of the cooler. When the cell stack is not faulty, water vapor is not discharged from the target chamber (in other words, the exhaust gas discharged from the target chamber does not contain water vapor), so the moisture detector does not detect moisture. On the other hand, when the cell stack is faulty, gas leaks between the fuel chamber and the air chamber. Depending on the direction of the gas leak, water vapor may flow into the target chamber, or the gas that has flowed into the target chamber may react with existing gas in the target chamber to generate new water vapor. In these cases, the exhaust gas discharged from the target chamber contains water vapor. Therefore, when the exhaust gas is cooled by the cooler, some of the water vapor condenses inside the cooler to form water. If the moisture detector is disposed inside the cooler, it detects this condensed water. Furthermore, water vapor that did not condense in the cooler remains in the exhaust gas after passing through the cooler. When a moisture detector is disposed downstream of the cooler, the moisture detector detects this remaining moisture. With this configuration, the presence or absence of a cell stack failure can be determined based on whether the moisture detector detects moisture, and therefore even a failure in which the gas sealing performance around one or several electrolysis unit cells is reduced can be appropriately detected. In other words, it is possible to determine the presence or absence of a failure with a simple configuration without considering the temperature, pressure, manufacturing variations, and deterioration level of the cell stack. In addition, there is no need to connect voltage wires to all of the electrolysis unit cells, which prevents a significant increase in the number of steps. As a result, it is possible to appropriately detect a cell stack failure.

[0008] The cell stack failure detection system according to the present invention comprises: a cell stack (1) including a plurality of solid oxide electrolysis unit cells (10), each of which includes a solid electrolyte layer (12), an air electrode (14) stacked on the front side of the solid electrolyte layer, and a fuel electrode (16) stacked on the back side of the solid electrolyte layer; a cooler (133, 43) for cooling the gas passing through it; a moisture detector (134, 44) for detecting moisture; a failure detection unit (50, 150) that detects a failure in the cell stack; Equipped with. The supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber (Sf) which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber (Sa) which is a space on the air electrode side, the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that satisfy at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are defined as the steam production conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, the cooler is disposed downstream of a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; the moisture detector is located within or downstream of the cooler; The failure detection unit is configured to determine that the cell stack has failed when moisture is detected by the moisture detector.

[0009] This failure detection system includes a failure detection unit that detects a failure in the cell stack. The failure detection unit is configured to determine that the cell stack has failed when moisture is detected by the moisture detector. This configuration makes it possible to appropriately detect a failure in the cell stack based on the determination result of the failure detection unit.

[0010] In one aspect of the invention, Each of the plurality of electrolytic single cells (10) is used as either an electrolytic single cell for producing hydrogen, an electrolytic single cell for producing synthesis gas containing hydrogen and carbon monoxide, or an electrolytic single cell for producing carbon monoxide.

[0011] The cell stack failure detection method according to the present invention comprises the steps of: A method for detecting a fault in a cell stack (1) including a plurality of solid oxide electrolysis unit cells (10), each of which includes a solid electrolyte layer (12), an air electrode (14) stacked on a front side of the solid electrolyte layer, and a fuel electrode (16) stacked on a back side of the solid electrolyte layer, The supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber (Sf) which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber (Sa) which is a space on the air electrode side, the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that satisfy at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are defined as the steam production conditions, At least one of the water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied. This fault detection method is cooling exhaust gas discharged from a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; determining that the cell stack has failed if moisture is detected during cooling of the exhaust gas or if moisture is detected in the exhaust gas after cooling; Includes:

[0012] According to this failure detection method, it is possible to appropriately detect a failure in a cell stack.

[0013] In the above description, in order to facilitate understanding of the invention, the symbols used in the embodiments are added in parentheses to the constituent elements of the invention corresponding to the embodiments, but each constituent element of the invention is not limited to the embodiments defined by the symbols. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram of a cell stack failure detection system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a cell stack. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view in the thickness direction of a unit cell included in the electrolysis unit of FIG. [Figure 5] FIG. 10 is a block diagram of a cell stack failure detection system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] (First embodiment) A cell stack module M1, a cell stack fault detection system 100, and a cell stack fault detection method according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the fault detection system 100. As shown in FIG. 1, the fault detection system 100 includes a cell stack module M1 and a fault detection unit 50. The cell stack module M1 includes a cell stack 1, an external power supply 20, supply pipes 31 and 41, discharge pipes 32 and 42, a cooler 43, and a moisture meter 44.

[0016] The cell stack 1 will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view of the cell stack 1, and FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. As shown in FIGS. 2 and 3, the cell stack 1 includes an electrolysis unit group including a plurality of rectangular flat-plate-shaped electrolysis units Ue stacked in the thickness direction (vertical direction), and a pair of end plates 2, 3 disposed on the upper and lower surfaces of the electrolysis unit group, respectively. In the present embodiment, the upper side corresponds to an example of the "front side," and the lower side corresponds to an example of the "rear side." The cell stack 1 functions as an electrolysis device that electrolyzes fuel gas (described later) to produce a desired gas. The electrolysis units Ue are the smallest units of the electrolysis device. The end plates 2, 3 are rectangular flat-plate-shaped members having the same outer shape as the electrolysis units Ue, and each end plate has a rectangular opening formed in its center. The electrolysis unit group and the end plates 2, 3 are fastened to each other at their four corners by bolts B and nuts (not shown) that are inserted through the end plates 2, 3 in the thickness direction. The end plates 2 and 3 are made of metal (for example, stainless steel) and function as an anode and a cathode, respectively, when a voltage is applied. For ease of explanation, the proportions of the components in the drawings may differ from the actual proportions.

[0017] The electrolysis unit Ue will be described in detail with reference to Fig. 3. As shown in Fig. 3, the electrolysis unit Ue comprises a single cell 10, an interconnector 4, a separator 5, a cathode frame 6, a fuel electrode frame 7, and a current collector 8.

[0018] The unit cell 10 is the smallest unit of a solid oxide electrolysis cell (SOEC) (i.e., a solid oxide electrolysis unit cell), and includes a solid electrolyte layer 12, an air electrode 14 laminated on the upper surface of the solid electrolyte layer 12, and an anode 16 laminated on the lower surface of the solid electrolyte layer 12. The air electrode 14 has a smaller outer shape than the solid electrolyte layer 12 and the anode 16, and is located in the center of the upper surface of the solid electrolyte layer 12 when viewed from above. Therefore, the upper surface of the outer periphery of the solid electrolyte layer 12 is exposed to the outside.

[0019] The interconnector 4 is a rectangular metal (for example, stainless steel) member that has a rectangular current collecting part 4a that protrudes downward from the centre of its lower surface. A pair of interconnectors 4 is arranged on both sides of the unit cell 10 in the thickness direction. Two adjacent electrolysis units Ue share one interconnector 4. In other words, the interconnector 4 also functions as a separator that separates the two adjacent electrolysis units Ue. The lower surface of the current collecting part 4a is in contact with the upper surface of the air electrode 14 of the unit cell 10. The lower electrolysis unit Ue includes a pair of interconnectors 4, 9 instead of the pair of interconnectors 4, 4. The interconnector 9 is arranged at the bottom of the cell stack 1 and differs from the interconnector 4 in that it does not have a current collecting part 4a.

[0020] The separator 5 is a rectangular plate-shaped metal (e.g., stainless steel) member with a rectangular opening formed in the center. The periphery of the opening of the separator 5 is brazed to the upper surface of the outer periphery of the solid electrolyte layer 12 of the unit cell 10 with a brazing material (e.g., Ag brazing) (not shown). The separator 5 prevents the gas generated at the air electrode by electrolysis of the fuel gas from mixing with the gas generated at the fuel electrode.

[0021] The air electrode frame 6 is a rectangular plate-shaped insulating member and may be formed of, for example, a mica sheet. A rectangular opening is formed in the center of the air electrode frame 6. The air electrode frame 6 is disposed so as to be interposed between the interconnector 4 (strictly speaking, the upper interconnector in the electrolysis unit Ue) and the separator 5.

[0022] The fuel electrode frame 7 is a rectangular plate-shaped metal (for example, stainless steel) member with a square opening formed in its center. The fuel electrode frame 7 is disposed so as to be interposed between the separator 5 and the interconnector 4 (strictly speaking, the lower interconnector in the electrolysis unit Ue).

[0023] The internal space of the electrolysis unit Ue is partitioned into an air chamber Sa and a fuel chamber Sf. The air chamber Sa is a space on the air electrode 14 side and is composed of an upper interconnector 4, separator 5, air electrode frame 6, and unit cell 10. The fuel chamber Sf is a space on the fuel electrode 16 side and is composed of a separator 5, a lower interconnector 4, fuel electrode frame 7, and unit cell 10.

[0024] The current collector 8 is a rectangular porous member made of metal (for example, nickel) that is smaller than the fuel electrode 16 in a plan view. The current collector 8 is arranged in the fuel chamber Sf so as to contact the lower surface of the fuel electrode 16 and the upper surface of the lower interconnector 4. Two adjacent unit cells 10 are stacked in the thickness direction so as to share the interconnector 4 via the current collector 8, thereby electrically connecting the unit cells 10 in series.

[0025] 2 and 3, four paths Pfi, Pfo, Pai, and Pao are formed as gas flow paths on the outer periphery of the cell stack 1. These paths Pfi, Pfo, Pai, and Pao are each formed to penetrate members of the cell stack 1 in the thickness direction, excluding the "end plate 2" and the "interconnector 4 above the upper electrolysis unit Ue."

[0026] The path Pfi is formed along side E1, which is one of the four sides that make up the outer periphery of the cell stack 1, near one corner of side E1. The path Pfo is formed along side E2 that faces side E1, near the other corner of side E2 (the corner located diagonally from the one corner of side E1). As shown in FIG. 3 , the path Pfi communicates with the fuel chamber Sf via a horizontal hole 7a formed in the anode frame 7 of each electrolysis unit Ue. The path Pfo communicates with the fuel chamber Sf via a horizontal hole 7b formed in the anode frame 7 of each electrolysis unit Ue.

[0027] The path Pai is formed along the side E2 and near one corner of the side E2. The path Pao is formed along the side E1 and near the other corner of the side E1. The path Pai and the path Pao each communicate with the air chamber Sa via a horizontal hole (not shown) formed in the air electrode frame 6 of each electrolysis unit Ue.

[0028] Next, the configuration of the unit cell 10 will be described in more detail with reference to FIG. 4. FIG. 4 is a cross-sectional view of the unit cell 10 in the thickness direction. As shown in FIG. 4, the solid electrolyte layer 12 is a rectangular flat layer and is configured to contain YSZ (yttria-stabilized zirconia). The solid electrolyte layer 12 has high oxide ion conductivity. The solid electrolyte layer 12 can be formed to have, for example, a 150 mm square and a thickness of 3 μm to 30 μm.

[0029] The air electrode 14 is a rectangular flat layer containing a perovskite oxide such as lanthanum strontium cobalt iron oxide (LSCF). The air electrode 14 includes a functional layer and a current collecting layer. The current collecting layer is thicker than the functional layer and is disposed on top of the functional layer. The air electrode 14 has high electronic conductivity and effectively collects electrons from the current collecting layer. The air electrode 14 may be formed to a thickness of, for example, 5 to 200 μm. An intermediate layer may be disposed between the solid electrolyte layer 12 and the air electrode 14. The intermediate layer may be, for example, 1 μm to 20 μm thick and may contain a ceria-based oxide. The intermediate layer functions as a reaction prevention layer that prevents elements contained in the air electrode 14 from reacting with the solid electrolyte layer 12.

[0030] The anode 16 is a rectangular flat layer and is formed to have a thickness of, for example, 200 μm to 1000 μm, which is greater than the thicknesses of the solid electrolyte layer 12 and the air electrode 14. In other words, the unit cell 10 is an anode-supported cell in which the solid electrolyte layer 12 and the air electrode 14 are supported by the anode 16. The anode 16 has a support layer 18a and a functional layer 18b. The support layer 18a is significantly thicker than the functional layer 18b. The functional layer 18b is laminated between the upper surface of the support layer 18a and the lower surface of the solid electrolyte layer 12.

[0031] The support layer 18a is a cermet of nickel and YSZ, and is configured to be porous, including a plurality of micropores (not shown). The diameter of the micropores is on the order of several μm, which ensures the permeability of the fuel gas. The functional layer 18b is similar to the support layer 18a in that it is a cermet of nickel and YSZ, but differs from the support layer 18a in that it is formed more densely than the support layer 18a. The fuel electrode 16 has high electronic conductivity.

[0032] Continuing the explanation, returning to Figure 1, the external power supply 20 is electrically connected to the cell stack 1 by having its positive electrode connected to the end plate 2 (not shown in Figure 1) via wiring and its negative electrode connected to the end plate 3 (not shown in Figure 1) via wiring. The external power supply 20 is configured to apply a predetermined voltage to the cell stack 1.

[0033] The supply pipe 31 is connected to a path Pfi (not shown in FIG. 1) of the cell stack 1. During operation of the cell stack 1, a first supply gas is supplied from an inlet of the supply pipe 31. The first supply gas supplied from the inlet flows through the supply pipe 31 and flows into the fuel chamber Sf via the path Pfi. The first supply gas is a mixed gas containing a fuel gas and a reducing gas. The fuel gas is a gas that is subject to electrolysis. The reducing gas is a gas that suppresses oxidation of the catalyst contained in the fuel electrode 16, and is not electrolyzed (i.e., the reducing gas is not subject to electrolysis). By including a reducing gas in the first supply gas, the cell stack 1 can be used stably for a long period of time. The reducing gas is an example of a "specific gas."

[0034] The exhaust pipe 32 is connected to a path Pfo (not shown in FIG. 1) of the cell stack 1. During operation of the cell stack 1, a first exhaust gas is discharged from the fuel chamber Sf via the path Pfo to the exhaust pipe 32. The first exhaust gas flows through the exhaust pipe 32, is discharged from its outlet, and is recovered by a well-known method. The first exhaust gas contains a first product gas that is produced by electrolyzing the fuel gas at the fuel electrode 16.

[0035] The supply pipe 41 is connected to a path Pai (not shown in FIG. 1) of the cell stack 1. During operation of the cell stack 1, a second supply gas is supplied from an inlet of the supply pipe 41. The second supply gas supplied from the inlet flows through the supply pipe 41 and flows into the air chamber Sa via the path Pai. The second supply gas is a gas supplied to control the temperature of the cell stack 1, and air is usually used.

[0036] The exhaust pipe 42 is connected to a path Pao (not shown in FIG. 1) of the cell stack 1. During operation of the cell stack 1, a second exhaust gas is discharged from the air chamber Sa via the path Pao to the exhaust pipe 42. The second exhaust gas flows through the exhaust pipe 42, is discharged from its outlet, and is recovered by a well-known method. The second exhaust gas contains a second product gas that is generated by electrolyzing the fuel gas at the fuel electrode 16.

[0037] The cooler 43 is provided in the exhaust pipe 42. In other words, the cooler 43 is disposed downstream of the air chamber Sa. The cooler 43 cools the second exhaust gas passing through it to a predetermined set temperature (for example, 15 degrees). If the second exhaust gas contains water vapor, the cooler 43 condenses some of the water vapor into water.

[0038] The moisture meter 44 is provided in the discharge pipe 42 so as to be located downstream of the cooler 43. The moisture meter 44 detects moisture (water vapor) contained in the second exhaust gas after passing through the cooler 43. The moisture meter 44 may be, for example, a hygrometer, a dew point meter, an electrical resistance moisture meter, a laser moisture meter, or a combination of two or more of these. Note that, instead of the moisture meter 44, a mechanism capable of detecting moisture contained in the second exhaust gas may be used. For example, such a mechanism may be a moisture detection mechanism consisting of a desiccant (typically silica gel) and a mass meter. The moisture meter 44 or the moisture detection mechanism corresponds to an example of a "moisture detector." The cell stack 1 and the above-mentioned components 20, 31, 41, 32, 42, 43, and 44 constitute a cell stack module M1.

[0039] The fault detection unit 50 is electrically connected to the moisture meter 44 and acquires a measured value w1 from the moisture meter 44. If the moisture meter 44 is a hygrometer, the measured value w1 is humidity (relative humidity or absolute humidity); if the moisture meter 44 is a dew point meter, the measured value w1 is a dew point; and if the moisture meter 44 is a laser moisture meter, the measured value w1 is a volumetric moisture percentage or a weight moisture percentage. The fault detection unit 50 is configured to determine whether or not the cell stack 1 has failed based on the measured value w1 (details will be described later). Note that the term "failure" here refers to a failure that causes a deterioration in the gas sealing performance of the air chamber Sa and / or the fuel chamber Sf of each electrolysis unit Ue.

[0040] In order for the failure detection unit 50 to properly determine whether or not there is a failure in the cell stack 1, at least one of the water vapor containing condition and the water vapor generating condition must be met. Here, the water vapor containing condition is a condition in which the fuel gas contains water vapor. On the other hand, the water vapor generating condition is a condition in which at least one of the following conditions 1 and 2, and at least one of the following conditions 3 and 4, are met. (Condition 1) Hydrogen is produced by electrolysis of fuel gas. (Condition 2) The reducing gas contains hydrogen gas. (Condition 3) Oxygen is produced by electrolysis of fuel gas. (Condition 4) The second supply gas contains oxygen.

[0041] The cell stack 1 can be operated in different operation modes depending on the type of fuel gas. In this embodiment, two types of fuel gas are used: "water vapor" or "a mixed gas of water vapor and carbon dioxide." Hereinafter, the operation mode when the fuel gas is water vapor will be referred to as the "steam electrolysis mode," and the operation mode when the fuel gas is a mixed gas of water vapor and carbon dioxide will be referred to as the "co-electrolysis mode." In either operation mode, "hydrogen" or "carbon monoxide" is used as the reducing gas. In other words, the cell stack 1 can be operated in four different patterns.

[0042] The operation of the cell stack 1 will be described using an example in which it is operated in steam electrolysis mode using hydrogen as the reducing gas. First, a voltage is applied to the end plates 2, 3 of the cell stack 1 from the external power supply 20. Next, when a high-temperature mixed gas of steam (fuel gas) and hydrogen (reducing gas) is supplied from the supply pipe 31 as the first supply gas, the mixed gas flows into the fuel chamber Sf of each electrolysis unit Ue via the path Pfi and the horizontal hole 7a. Furthermore, when high-temperature air is supplied from the supply pipe 41 as the second supply gas, the air flows into the air chamber Sa of each electrolysis unit Ue via the path Pai and a horizontal hole (not shown).

[0043] The water vapor that flows into the fuel chamber Sf passes through the support layer 18a of the fuel electrode 16 and travels to the functional layer 18b. In the functional layer 18b, the water vapor reacts with electrons (electrons supplied from the end plate 3 via the current collector 8) and is electrolyzed into hydrogen (a first product gas) and oxide ions. The high-temperature mixed gas of "unreacted water vapor" and "hydrogen" diffuses within the fuel chamber Sf and is discharged to the exhaust pipe 32 as a first exhaust gas via the horizontal hole 7b and the path Pfo, where it is recovered by a known method. The hydrogen contained in the first exhaust gas consists of "hydrogen as the first product gas" and "hydrogen as a reducing gas." The oxide ions travel through the solid electrolyte layer 12 to the air electrode 14 in the air chamber Sa, where they release electrons at the functional layer of the air electrode 14 and become oxygen (a second product gas). The high-temperature mixed gas of "air that has flowed into the air chamber Sa" and "oxygen" diffuses within the air chamber Sa and is discharged as a second exhaust gas into the exhaust pipe 42 via a horizontal hole (not shown) and a path Pao, and is recovered by a well-known method. Electrons emitted from the functional layer are collected by the current collecting part 4a of the interconnector 4 via the current collecting layer, and circulate from the end plate 2 to the end plate 3 via the external power supply 20. As a result, a current corresponding to the applied voltage (applied current) flows through the cell stack 1.

[0044] On the other hand, when operating in steam electrolysis mode using carbon monoxide as the reducing gas, the first exhaust gas is a mixture of "unreacted steam," "hydrogen (first product gas)," and "carbon monoxide (reducing gas)." Other than that, it is the same as when hydrogen is used as the reducing gas.

[0045] Furthermore, when operating in the co-electrolysis mode using hydrogen as the reducing gas, a mixture of water vapor (fuel gas), carbon dioxide (fuel gas), and hydrogen (reducing gas) is used as the first supply gas, and air is used as the second supply gas. The electrolysis of water vapor produces hydrogen at the fuel electrode 16 and oxygen at the air electrode 14, while the electrolysis of carbon dioxide produces carbon monoxide at the fuel electrode 16 and oxygen at the air electrode 14. Therefore, the synthesis gas containing hydrogen and carbon monoxide corresponds to the first product gas, and oxygen corresponds to the second product gas. The first exhaust gas is a mixture of "unreacted water vapor" and "hydrogen," and "unreacted carbon dioxide" and "carbon monoxide." The hydrogen contained in this first exhaust gas consists of "hydrogen as the first product gas" and "hydrogen as the reducing gas." The types of the second exhaust gas are the same as when operating in the steam electrolysis mode.

[0046] On the other hand, when operating in co-electrolysis mode using carbon monoxide as the reducing gas, the first exhaust gas is a mixture of "unreacted water vapor" and "hydrogen" and "unreacted carbon dioxide" and "carbon monoxide." The carbon monoxide contained in this first exhaust gas consists of "carbon monoxide as the first product gas" and "carbon monoxide as the reducing gas." Other than that, it is the same as when hydrogen is used as the reducing gas.

[0047] As is clear from the above description, in this embodiment, both the water vapor content condition and the water vapor generation condition are met regardless of the type of reducing gas when the system is operated in any of the four patterns. Specifically, when the system is operated in the steam electrolysis mode, the fuel gas is water vapor, and therefore the water vapor content condition is met regardless of the type of reducing gas. Furthermore, when the system is operated in the steam electrolysis mode using hydrogen as the reducing gas, all of Conditions 1 to 4 are met, and therefore the water vapor generation condition is met. When the system is operated in the steam electrolysis mode using carbon monoxide as the reducing gas, all of Conditions 1, 3, and 4 are met, and therefore the water vapor generation condition is met. On the other hand, when the system is operated in the co-electrolysis mode, the fuel gas is water vapor and carbon dioxide, and therefore the water vapor content condition is met regardless of the type of reducing gas. Furthermore, when the system is operated in the co-electrolysis mode using hydrogen as the reducing gas, all of Conditions 1 to 4 are met, and therefore the water vapor generation condition is met. When the system is operated in the co-electrolysis mode using carbon monoxide as the reducing gas, all of Conditions 1, 3, and 4 are met, and therefore the water vapor generation condition is met.

[0048] Next, the failure detection unit 50 will be described in detail. While the cell stack 1 is operating normally, the first exhaust gas contains water vapor (strictly speaking, unreacted water vapor), while the second exhaust gas does not. However, if the cell stack 1 fails and gas leaks from the fuel chamber Sf toward the air chamber Sa while the water vapor inclusion condition is met, the water vapor in the fuel chamber Sf flows into the air chamber Sa, and the second exhaust gas contains water vapor that should not be present under normal conditions. Furthermore, if the cell stack 1 fails and gas leaks from the fuel chamber Sf toward the air chamber Sa while the water vapor generation condition is met, hydrogen in the fuel chamber Sf (strictly speaking, hydrogen as the first product gas and / or hydrogen as the reducing gas) flows into the air chamber Sa. The hydrogen that has flowed into the air chamber Sa reacts with the oxygen already present in the air chamber Sa (strictly speaking, oxygen as the second product gas and / or oxygen in the air), generating new water vapor. As a result, the second exhaust gas contains water vapor that should not be present under normal conditions. Therefore, when at least one of the water vapor containing condition and the water vapor generating condition is satisfied, water vapor that has not condensed in the cooler 43 remains in the second exhaust gas after passing through the cooler 43.

[0049] Therefore, in this embodiment, a moisture meter 44 is disposed downstream of the cooler 43. The failure detection unit 50 is configured to determine that the cell stack 1 has failed when the measurement value w1 of the moisture meter 44 is equal to or greater than a predetermined threshold value w1th. The threshold value w1th is a value such that the measurement value w1 under normal conditions is less than the threshold value w1th and the measurement value w1 under failure is equal to or greater than the threshold value w1th. Therefore, "the measurement value w1 being equal to or greater than the threshold value w1th" is synonymous with "water vapor that should not be detected under normal conditions is detected in the second exhaust gas." The threshold value w1th can be determined in advance according to the type of moisture meter 44 based on experiments or simulations.

[0050] That is, the fault detection unit 50 is configured to determine whether or not there is a fault in the cell stack 1 by determining whether or not water vapor is contained in the exhaust gas (second exhaust gas) discharged from a chamber from which water vapor is not discharged during normal operation (in this embodiment, the air chamber Sa). Hereinafter, the chamber from which water vapor is not discharged during normal operation will also be referred to as the "target chamber." The fault detection unit 50 and the above-mentioned cell stack module M1 constitute a fault detection system 100.

[0051] Next, a fault detection method for the cell stack 1 will be described. This fault detection method includes a second exhaust gas cooling step and a fault determination step. In the second exhaust gas cooling step, the cooler 43 cools the second exhaust gas (i.e., the gas discharged from the air chamber Sa, which is the target chamber) to a set temperature. In the fault determination step, the fault detection unit 50 determines whether the measured value w1 of the moisture meter 44 is equal to or greater than the threshold value w1th. If w1≧w1th (in other words, if water vapor is detected in the second exhaust gas after passing through the cooler 43), it is determined that the cell stack 1 has faulted.

[0052] As described above, in the cell stack module M1 according to the first embodiment, the cooler 43 is disposed downstream of the air chamber Sa, which is the target chamber, and the moisture meter 44 is disposed downstream of the cooler 43. When at least one of the water vapor content condition and the water vapor generation condition is satisfied, if the cell stack 1 fails and gas leaks from the fuel chamber Sf toward the air chamber Sa, water vapor that did not condense in the cooler 43 will remain in the second exhaust gas. As a result, w1 ≧ w1th is satisfied. Therefore, with this configuration, the presence or absence of a failure in the cell stack 1 can be determined based on whether the measured value w1 is equal to or greater than the threshold value w1th. Therefore, even a failure that reduces the gas sealing performance of one or several electrolysis units Ue can be appropriately detected. In other words, the presence or absence of a failure can be determined with a simple configuration without considering the temperature, pressure, manufacturing variations, and deterioration level of the cell stack 1. Additionally, since there is no need to connect voltage lines to all of the unit cells 10, a significant increase in labor costs can be prevented. As a result, a failure in the cell stack 1 (in this embodiment, a failure of the type in which gas leaks from the fuel chamber Sf toward the air chamber Sa) can be detected appropriately.

[0053] Furthermore, because the exhaust gas emitted from the cell stack module M1 is at a high temperature, it has been a common practice to cool the exhaust gas in order to recover the generated gas. For this reason, in the cell stack module M1, failure detection of the cell stack 1 can be achieved by the simple means of introducing a moisture meter 44, thereby reducing the costs associated with failure detection.

[0054] Furthermore, the fault detection system 100 according to the first embodiment includes a fault detection unit 50 in addition to the cell stack module M1. The fault detection unit 50 is configured to determine that the cell stack 1 has failed when w1≧w1th. With this configuration, a fault in the cell stack 1 can be appropriately detected based on the determination result of the fault detection unit 50.

[0055] Furthermore, the failure detection method according to the first embodiment includes a second exhaust gas cooling step and a failure determination step. With this configuration, a failure in the cell stack 1 can be detected appropriately.

[0056] (Second embodiment) A cell stack module M2, a cell stack fault detection system 200, and a cell stack fault detection method according to a second embodiment of the present invention will be described below with reference to the drawings. The second embodiment differs from the first embodiment in that the fault detection system 200 additionally includes a cooler 133 and a moisture meter 134, uses carbon dioxide as the fuel gas, and is capable of detecting a fault even when gas leaks from the air chamber Sa to the fuel chamber Sf. The following mainly describes the differences from the first embodiment. Elements identical to those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. FIG. 5 is a block diagram of the cell stack fault detection system 200. As shown in FIG. 5, the fault detection system 200 includes a cell stack module M2 and a fault detection unit 150. The cell stack module M2 includes a cell stack 1, an external power supply 20, supply pipes 31 and 41, discharge pipes 32 and 42, coolers 133 and 43, and moisture meters 134 and 44.

[0057] The cooler 133 is provided in the exhaust pipe 32. In other words, the cooler 133 is disposed downstream of the fuel chamber Sf. The cooler 133 cools the first exhaust gas passing through it to a predetermined set temperature (for example, 15 degrees). If the first exhaust gas contains water vapor, the cooler 133 condenses some of the water vapor into water.

[0058] The moisture meter 134 is provided in the discharge pipe 32 so as to be located downstream of the cooler 133. The moisture meter 134 detects moisture (water vapor) contained in the first exhaust gas after passing through the cooler 133. For example, a hygrometer, a dew point meter, an electrical resistance moisture meter, a laser moisture meter, or a combination of two or more of these may be used as the moisture meter 134. Note that instead of the moisture meter 134, a mechanism capable of detecting moisture contained in the first exhaust gas may be used. For example, the mechanism may be a moisture detection mechanism including a desiccant (typically, silica gel) and a mass meter. The moisture meter 134 or the moisture detection mechanism corresponds to an example of a "moisture detector."

[0059] The fault detection unit 150 is electrically connected to the moisture meters 134 and 44, and acquires a measurement value w2 from the moisture meter 134 and a measurement value w1 from the moisture meter 44. The fault detection unit 150 is configured to determine whether or not there is a fault in the cell stack 1 based on these measurement values ​​w1 and w2 (details will be described later).

[0060] In this embodiment, carbon dioxide is used as the fuel gas. Hereinafter, the operation mode when carbon dioxide is used as the fuel gas is referred to as the carbon dioxide electrolysis mode. Hydrogen is used as the reducing gas. In other words, the cell stack 1 can be operated in only one pattern.

[0061] When operating in carbon dioxide electrolysis mode using hydrogen as the reducing gas, a mixed gas of carbon dioxide (fuel gas) and hydrogen (reducing gas) is used as the first supply gas, and air is used as the second supply gas. Carbon dioxide electrolysis generates carbon monoxide (first product gas) at the fuel electrode 16 and oxygen (second product gas) at the air electrode 14. As a result, the first exhaust gas is a mixed gas of "unreacted carbon dioxide," "carbon monoxide," and "hydrogen." The type of the second exhaust gas is the same as when operating in the water vapor electrolysis mode of the first embodiment (i.e., a mixed gas of "air flowing into the air chamber Sa" and "oxygen"). Therefore, in this embodiment, the water vapor content condition is not met, but conditions 2 to 4 are met, so the water vapor generation condition is met.

[0062] While the cell stack 1 is operating normally, neither the second exhaust gas nor the first exhaust gas contains water vapor. Therefore, in this embodiment, both the air chamber Sa and the fuel chamber Sf correspond to the target chambers. In contrast, if the cell stack 1 fails and gas leaks from the fuel chamber Sf toward the air chamber Sa, hydrogen in the fuel chamber Sf (strictly speaking, hydrogen as a reducing gas) flows into the air chamber Sa. The hydrogen that flows into the air chamber Sa reacts with the existing oxygen in the air chamber Sa (strictly speaking, oxygen as the second product gas and / or oxygen in the air), thereby generating new water vapor. As a result, the second exhaust gas contains water vapor, which should not be present under normal conditions. On the other hand, if the cell stack 1 fails and gas leaks from the air chamber Sa toward the fuel chamber Sf, oxygen in the air chamber Sa (strictly speaking, oxygen as the second product gas and / or oxygen in the air) flows into the fuel chamber Sf. The oxygen that flows into the fuel chamber Sf reacts with the existing hydrogen (strictly speaking, hydrogen as a reducing gas) in the fuel chamber Sf to generate new water vapor. As a result, the first exhaust gas contains water vapor that should not be contained under normal conditions. Therefore, when the water vapor generation condition is met, depending on the gas leakage direction, water vapor that did not condense in the cooler 43 or 133 remains in the second exhaust gas or the first exhaust gas after passing through the cooler 43 or 133, respectively.

[0063] Therefore, in this embodiment, a moisture meter 134 is also disposed downstream of the cooler 133. The failure detection unit 150 is configured to determine that the cell stack 1 is faulty if the measurement value w1 of the moisture meter 44 is equal to or greater than a threshold value w1th or if the measurement value w2 of the moisture meter 134 is equal to or greater than a predetermined threshold value w2th. The threshold value w2th is a value such that the measurement value w2 under normal conditions is less than the threshold value w2th and the measurement value w2 under failure is equal to or greater than the threshold value w2th. Therefore, "the measurement value w2 being equal to or greater than the threshold value w2th" is synonymous with "water vapor that should not be detected under normal conditions is detected in the first exhaust gas." The threshold value w2th can be determined in advance based on experiments or simulations and depending on the type of moisture meter 134. The failure detection unit 150 and the above-described cell stack module M2 constitute a failure detection system 200. The gas leak direction is determined based on the relative pressures in the fuel chamber Sf and the air chamber Sa. In other words, bidirectional leaks do not occur.

[0064] Next, a method for detecting a fault in the cell stack 1 will be described. This fault detection method includes an exhaust gas cooling step and a fault determination step. In the exhaust gas cooling step, the cooler 43 cools the second exhaust gas to a set temperature, and the cooler 133 cools the first exhaust gas to a set temperature. In the fault determination step, the fault detection unit 150 determines whether the measurement value w1 of the moisture meter 44 is equal to or greater than a threshold value w1th, and whether the measurement value w2 of the moisture meter 134 is equal to or greater than a threshold value w2th. If either w1≧w1th or w2≧w2th is true, it is determined that the cell stack 1 has a fault.

[0065] As described above, in the cell stack module M2 according to the second embodiment, the fuel chamber Sf is also a target chamber in addition to the air chamber Sa. Therefore, a cooler 133 and a moisture meter 134 are also disposed downstream of the fuel chamber Sf. When at least one of the water vapor containing condition and the water vapor generating condition is satisfied, if the cell stack 1 fails and gas leaks between the fuel chamber Sf and the air chamber Sa, water vapor that did not condense in the cooler 43 or 133 will remain in the second exhaust gas or the first exhaust gas. As a result, either w1 ≧ w1th or w2 ≧ w2th is satisfied. Therefore, with this configuration, the presence or absence of a failure in the cell stack 1 can be determined based on whether the measured value w1 or w2 is equal to or greater than the threshold value w1th or w2th. Therefore, even a failure that reduces the gas sealing performance of one or several electrolysis units Ue can be appropriately detected. In other words, the presence or absence of a failure can be determined with a simple configuration without considering the temperature, pressure, manufacturing variations, or deterioration level of the cell stack 1. In addition, a significant increase in the number of steps can be prevented because there is no need to connect voltage lines to all of the unit cells 10. As a result, a fault in the cell stack 1 (in this embodiment, a fault in which gas leaks from one of the fuel chamber Sf and the air chamber Sa to the other) can be properly detected.

[0066] Furthermore, the fault detection system 200 according to the second embodiment includes a fault detection unit 150 in addition to the cell stack module M2. The fault detection unit 150 is configured to determine that the cell stack 1 has failed when either w1≧w1th or w2≧w2th is established. With this configuration, a fault in the cell stack 1 can be appropriately detected based on the determination result of the fault detection unit 150.

[0067] Furthermore, the failure detection method according to the second embodiment includes an exhaust gas cooling step and a failure determination step. With this configuration, a failure in the cell stack 1 can be detected appropriately.

[0068] The above describes the cell stack module, cell stack fault detection system, and cell stack fault detection method according to the embodiments, but the present invention is not limited to the above embodiments, and various modifications are possible as long as they do not deviate from the purpose of the present invention.

[0069] For example, the types of the first supply gas and the second supply gas are not limited to those exemplified in the above embodiment, as long as at least one of the water vapor containing condition and the water vapor generating condition is satisfied.

[0070] Furthermore, in the first embodiment, the moisture meter 44 may be disposed inside the cooler 43. When the second exhaust gas contains water vapor, some of the water vapor condenses into water inside the cooler 43 as the second exhaust gas is cooled by the cooler 43. The moisture meter 44 detects this condensed water. When the measurement value w1 of the moisture meter 44 is equal to or greater than a predetermined threshold value w1inth, the failure detection unit 50 may be configured to determine that water was detected during cooling of the second exhaust gas and that the cell stack 1 is faulty. The threshold value w1inth may be the same as or different from the threshold value w1th. Similarly, in the second embodiment, at least one of the moisture meter 134 and the moisture meter 44 may be disposed inside the corresponding cooler. For example, when the moisture meter 134 is disposed inside the cooler 133, the moisture meter 134 detects water condensed inside the cooler 133 as the first exhaust gas is cooled by the cooler 133. The failure detection unit 150 may be configured to determine that water has been detected during cooling of the first exhaust gas and that the cell stack 1 has failed when the measured value w2 of the moisture meter 134 is equal to or greater than a predetermined threshold value w2inth. The threshold value w2inth may be the same as or different from the threshold value w2th.

[0071] Furthermore, although the systems 100 and 200 are configured to operate (i.e., to perform fault determination) during practical operation of the cell stack 1, the situation in which fault determination is performed is not limited to this. For example, the systems 100 and 200 may be operated for the purpose of inspection before shipping the cell stack 1, or for the purpose of periodic inspection after shipping.

[0072] Furthermore, the cell stack 1 may be configured to be capable of reversibly performing an electrolysis reaction and a power generation reaction. The electrochemical unit cell when the cell stack 1 is performing an electrolysis reaction corresponds to the unit cell 10 of the above embodiment.

[0073] Furthermore, the present invention may include the following aspects. [1] a cell stack including a plurality of solid oxide electrolysis unit cells, each of which includes a solid electrolyte layer, an air electrode stacked on a front surface side of the solid electrolyte layer, and a fuel electrode stacked on a back surface side of the solid electrolyte layer; a cooler for cooling gas passing through the cooler; a moisture detector for detecting moisture; Equipped with the supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber, which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber, which is a space on the air electrode side; the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that satisfy at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are defined as the steam production conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, the cooler is disposed downstream of a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; The moisture detector is located inside or downstream of the cooler. Cell stack module. [2] a cell stack including a plurality of solid oxide electrolysis unit cells, each of which includes a solid electrolyte layer, an air electrode stacked on a front surface side of the solid electrolyte layer, and a fuel electrode stacked on a back surface side of the solid electrolyte layer; a cooler for cooling gas passing through the cooler; a moisture detector for detecting moisture; a failure detection unit that detects a failure in the cell stack; Equipped with the supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber, which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber, which is a space on the air electrode side; the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that satisfy at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are defined as the steam production conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, the cooler is disposed downstream of a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; the moisture detector is located within or downstream of the cooler; the failure detection unit is configured to determine that the cell stack has failed when moisture is detected by the moisture detector. Cell stack failure detection system. [3] [2] A cell stack failure detection system according to the present invention, each of the plurality of electrolytic single cells is used as either an electrolytic single cell for producing hydrogen, an electrolytic single cell for producing a synthesis gas containing hydrogen and carbon monoxide, or an electrolytic single cell for producing carbon monoxide; Cell stack failure detection system. [4] A cell stack failure detection method for detecting a failure in a cell stack including a plurality of solid oxide electrolysis unit cells, each of which includes a solid electrolyte layer, an air electrode stacked on a front surface side of the solid electrolyte layer, and a fuel electrode stacked on a back surface side of the solid electrolyte layer, the method comprising: the supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber, which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber, which is a space on the air electrode side; the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that satisfy at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are defined as the steam production conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, cooling exhaust gas discharged from a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; determining that the cell stack has failed if moisture is detected during cooling of the exhaust gas or if moisture is detected in the exhaust gas after cooling; Including, A method for detecting cell stack failures. [Explanation of symbols]

[0074] 1: cell stack, 2: end plate, 3: end plate, 4: interconnector, 5: separator, 6: air electrode frame, 7: fuel electrode frame, 8: current collector, 9: (lowest) interconnector, 10: solid oxide electrolysis unit cell, 12: solid electrolyte layer, 14: air electrode, 16: fuel electrode, 18a: support layer, 18b: functional layer, 20: external power supply, 31, 41: supply pipe, 32, 42: discharge pipe, 43, 133: cooler, 44, 134: moisture meter, 50, 150: failure detection unit, 100, 200: failure detection system

Claims

1. a cell stack including a plurality of solid oxide electrolysis unit cells, each of which includes a solid electrolyte layer, an air electrode stacked on a front surface side of the solid electrolyte layer, and a fuel electrode stacked on a back surface side of the solid electrolyte layer; a cooler for cooling gas passing through the cooler; a moisture detector for detecting moisture; Equipped with the supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber, which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber, which is a space on the air electrode side; the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are satisfied are defined as the steam generation conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, the cooler is disposed downstream of a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; The moisture detector is located inside or downstream of the cooler. Cell stack module.

2. a cell stack including a plurality of solid oxide electrolysis unit cells, each of which includes a solid electrolyte layer, an air electrode stacked on a front surface side of the solid electrolyte layer, and a fuel electrode stacked on a back surface side of the solid electrolyte layer; a cooler for cooling gas passing through the cooler; a moisture detector for detecting moisture; a failure detection unit that detects a failure in the cell stack; Equipped with the supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber, which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber, which is a space on the air electrode side; the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are satisfied are defined as the steam generation conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, the cooler is disposed downstream of a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; the moisture detector is located within or downstream of the cooler; the failure detection unit is configured to determine that the cell stack has failed when moisture is detected by the moisture detector. Cell stack failure detection system.

3. 3. The cell stack failure detection system according to claim 2, each of the plurality of electrolytic single cells is used as either an electrolytic single cell for producing hydrogen, an electrolytic single cell for producing a synthesis gas containing hydrogen and carbon monoxide, or an electrolytic single cell for producing carbon monoxide; Cell stack failure detection system.

4. A cell stack failure detection method for detecting a failure in a cell stack including a plurality of solid oxide electrolysis unit cells, each of which includes a solid electrolyte layer, an air electrode stacked on a front surface side of the solid electrolyte layer, and a fuel electrode stacked on a back surface side of the solid electrolyte layer, the method comprising: the supply gases supplied into the cell stack include a first supply gas supplied to a fuel chamber, which is a space on the fuel electrode side, and a second supply gas supplied to an air chamber, which is a space on the air electrode side; the first supply gas is a mixed gas containing a fuel gas to be electrolyzed and a specific gas that is not to be electrolyzed, If the conditions that at least one of a first condition that hydrogen is produced by electrolysis of the fuel gas and a second condition that the specific gas contains hydrogen, and at least one of a third condition that oxygen is produced by electrolysis of the fuel gas and a fourth condition that the second supply gas contains oxygen are satisfied are defined as the steam generation conditions, At least one of a water vapor containing condition that the fuel gas contains water vapor and the water vapor generating condition is satisfied, cooling exhaust gas discharged from a target chamber, which is one of the fuel chamber and the air chamber, from which water vapor is not discharged during normal operation; determining that the cell stack has failed if moisture is detected during cooling of the exhaust gas or if moisture is detected in the exhaust gas after cooling; Including, A method for detecting cell stack failures.

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