Electrolysis system and electrolysis method

Abstract

According to the present embodiment, an electrolysis system includes an electrolysis cell stack, a power supply device, a gas supply device, an electrolyte supply device, supply pipes, and discharge pipes. The electrolysis cell stack electrolyzes a gas and an electrolyte. The gas supply device supplies the electrolyte to the other electrode. The supply pipes supply an anode fluid and a cathode fluid to the electrolysis cell stack. The discharge pipes discharge the anode fluid and the cathode fluid from the electrolysis cell stack. At least either one of the supply pipes and the discharge pipes include a plurality of insulator pipes inside of which is made of an electrical insulating material and a good conductor pipe made of a good conductor connected between the insulator pipes. The good conductor pipe is electrically connected to an object with a predetermined low potential.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2025-009304, filed on Jan. 22, 2025, the entire contents of which are incorporated herein by reference.FIELD

[0002] The embodiments of the present invention relate to an electrolysis system and an electrolysis method.BACKGROUND

[0003] An electrolysis system is a system that performs oxidation reaction by an anode in an electrolysis cell stack and reduction reaction by a cathode. When power is supplied to this electrolysis cell stack, a current leaks to a device away from an electrode through an electrolyte. Further, in a case where a wetted part of the device is a good conductor, there is a risk that the device is deteriorated by the leakage current and does not have long-term durability.

[0004] Therefore, there is known a double pipe formed by an inner pipe in which an electrolyte flows and an outer pipe provided outside the inner pipe with a space from the inner pipe, in order to prevent electrical leakage. The inner pipe is separated by an insulator pipe made of an insulating material in order to electrically insulate the electrolysis cell stack and the device from each other. With this configuration, insulation between the separated inner pipes is ensured.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a schematic diagram illustrating a configuration of a first embodiment of the present invention;

[0006] FIG. 2 is a flowchart illustrating a control example;

[0007] FIG. 3 is a schematic diagram illustrating a configuration example of a second embodiment;

[0008] FIG. 4 is a schematic diagram illustrating a configuration example of a third embodiment;

[0009] FIG. 5 is a schematic diagram illustrating a configuration example of a fourth embodiment; and

[0010] FIG. 6 is a schematic diagram illustrating a configuration example of a fifth embodiment.DETAILED DESCRIPTION

[0011] An electrolysis system according to the present embodiment includes an electrolysis cell stack, a power supply device, a gas supply device, an electrolyte supply device, supply pipes, and discharge pipes. The electrolysis cell stack performs electrolysis by causing a gas and an electrolyte to flow to corresponding electrodes of an anode and a cathode and applying a voltage. The power supply device applies a voltage between the electrode of the anode and the electrode of the cathode of the electrolysis cell stack. The gas supply device supplies the electrolyte to the other electrode. The supply pipes supply an anode fluid and a cathode fluid to the electrolysis cell stack. The discharge pipes discharge the anode fluid and the cathode fluid from the electrolysis cell stack. At least either one of the supply pipes and the discharge pipes include a plurality of insulator pipes inside of which is made of an electrical insulating material and a good conductor pipe made of a good conductor connected between the insulator pipes. The good conductor pipe is placed at a predetermined low potential.

[0012] Embodiments of the present invention will be explained below with reference to the drawings. The relation between the thickness and planar dimension of each constituent elements illustrated in the drawings, the ratio of thickness of each constituent elements, and the like do not necessarily match those of actual products. There are cases where the vertical direction is different from that according to gravitational acceleration. In the following embodiments, substantially the same constituent elements are denoted by like reference characters and explanations thereof will be omitted as appropriate. In the present specification, “connection” includes not only physical connection but also electrical connection, and also includes indirect connection as well as direct connection unless otherwise specified.First Embodiment[1-1 Configuration]

[0013] A configuration example of a first embodiment of the present invention is described with reference to a configuration diagram of FIG. 1. FIG. 1 is a schematic diagram illustrating a configuration example of an electrolysis system according to the first embodiment. An electrolysis system 1 according to the present embodiment includes an electrolysis cell stack 2, a carbon-dioxide-containing gas supply device 3, a carbon-dioxide-containing gas supply pipe 5, an electrolyte supply device 6, an electrolyte supply pipe 8, a carbon-dioxide-containing gas discharge pipe 9, an electrolyte discharge pipe 10, a pipe temperature adjuster 11, a humidifier 12, a DC power supply device 13, and a controller 20. Arrows in FIG. 1 represent flowing directions of corresponding fluids, respectively.

[0014] The electrolysis cell stack 2 is formed by stacking a plurality of electrolysis cells each including a cathode 4, an anode 7, and a separator (not illustrated) separating the cathode 4 and the anode 7 from each other. Although the electrolysis cell stack 2 according to the present embodiment is formed by stacking a plurality of electrolysis cells, the configuration is not limited thereto. For example, the electrolysis cell stack 2 may be formed by a single layer of electrolysis cell.

[0015] The cathode 4 includes a cathode catalyst for reducing an object of reduction such as carbon dioxide to produce a cathode product and a cathode electrode that applies a voltage. Examples of the cathode product include carbon compounds such as carbon monoxide.

[0016] The anode 7 includes an anode catalyst for oxidizing an object of oxidation such as water to produce an anode product and an anode electrode applying a voltage. Examples of the anode product include oxygen.

[0017] The separator is provided between the cathode 4 and the anode 7. The separator includes a porous membrane separating the cathode 4 and the anode 7 from each other. Examples of the porous membrane include a polyethersulfone (PES) filtration membrane and an ion exchange membrane. Although the electrolysis cell stack 2 according to the present embodiment is configured as described above, the configuration is not limited thereto. For example, the electrolysis cell stack may have any configuration as long as it performs electrolysis by causing a gas and an electrolyte to flow to corresponding electrodes of an anode and a cathode and applying a voltage.

[0018] The carbon-dioxide-containing gas supply device 3 supplies a gas. The gas is a carbon dioxide gas, for example. The carbon-dioxide-containing gas supply device 3 may have a gas cylinder accommodating a carbon dioxide gas and a pressure reducing valve controlling gas pressure.

[0019] The carbon-dioxide-containing gas supply pipe 5 connects the carbon-dioxide-containing gas supply device 3 and the humidifier 12, and an inlet of the cathode 4 to each other. In the carbon-dioxide-containing gas supply pipe 5, an insulator pipe 5a, a good conductor pipe 5b, and an insulator pipe 5c are connected.

[0020] The insulator pipe 5c is a pipe that is in contact with the electrolysis cell stack 2. On the carbon-dioxide-containing gas supply device 3 side of the insulator pipe 5c, a good conductor pipe and an insulator pipe may be further connected. The carbon-dioxide-containing gas supply pipe 5 supplies a carbon dioxide containing gas to the cathode 4 of the electrolysis cell stack 2 via the humidifier 12 in such a connection mode.

[0021] The electrolyte supply device 6 can supply an electrolyte. The electrolyte contains an ionic substance. As the ionic substance, at least one of hydroxide ions (OH−), hydrogen ions (H+), potassium ions (K+), lithium ions (Li+), and bicarbonate ions (HCO3−) is preferable, for example. The electrolyte contains water. The electrolyte supply device 6 may be provided with a pump.

[0022] The electrolyte supply pipe 8 connects the electrolyte supply device 6 and an inlet of the anode 7 to each other. In the electrolyte supply pipe 8, an insulator pipe 8a, a good conductor pipe 8b, and an insulator pipe 8c are connected.

[0023] The insulator pipe 8c is a pipe that is in contact with the electrolysis cell stack 2. On the electrolyte supply device 6 side of the insulator pipe 8c, at least either a good conductor pipe or an insulator pipe may be further connected. The electrolyte supply pipe 8 supplies an electrolyte to the cathode 4 of the electrolysis cell stack 2 in such a connection mode.

[0024] The carbon-dioxide-containing gas discharge pipe 9 is connected to an outlet of the cathode 4. In the carbon-dioxide-containing gas discharge pipe 9, an insulator pipe 9a, a good conductor pipe 9b, and an insulator pipe 9c are connected.

[0025] The insulator pipe 9a is a pipe that is in contact with the electrolysis cell stack 2. On a discharge end side of the insulator pipe 9c, at least either a good conductor pipe or an insulator pipe may be further connected. The carbon-dioxide-containing gas discharge pipe 9 discharges the carbon dioxide containing gas discharged from the cathode 4 in such a connection mode.

[0026] The electrolyte discharge pipe 10 is connected to an outlet of the anode 7. In the electrolyte discharge pipe 10, an insulator pipe 10a, a good conductor pipe 10b, and an insulator pipe 10c are connected.

[0027] The insulator pipe 10a is a pipe in contact with the electrolysis cell stack 2. On a discharge end side of the insulator pipe 10c, at least either a good conductor pipe or an insulator pipe may be further connected. The electrolyte discharge pipe 10 discharges an oxygen containing gas discharged from the anode 7 in such a connection mode.

[0028] Each of the insulator pipes 5a, 5c, 8a, 8c, 9a, 9c, 10a, and 10c is an insulator pipe inside of which is made of an electrical insulating material. The insulator pipe is made of an electrical insulating material, for example, by being coated with a resin such as Teflon at least inside the pipe. Alternatively, the entire pipe may be made of an electrical insulating material such as Teflon.

[0029] The good conductor pipe 5b, the good conductor pipe 8b, the good conductor pipe 9b, and the good conductor pipe 10b are metallic conductors. That is, each of the good conductor pipe 5b, the good conductor pipe 8b, the good conductor pipe 9b, and the good conductor pipe 10b is made of a conductive and durable metal.

[0030] The pipe temperature adjuster 11 is formed on the good conductor pipe 5b of the carbon-dioxide-containing gas supply pipe 5. The pipe temperature adjuster 11 is formed by at least a heater with insulation coating. In the pipe temperature adjuster 11, a structure that can turn on and off power supply and is made of a bimetal such as a thermostat is attached to the heater. Alternatively, it is permissible that a thermometer is fixed to the surface of the good conductor pipe 5b and that, in accordance with the temperature thereof, control is executed to turn on and off the heater or the heat generation amount of the heater may be controlled.

[0031] In the pipe temperature adjuster 11, a heater in which a semiconductor heating element 11a having a self-temperature control function is continuously arranged as a parallel circuit is wound around the surface of the good conductor pipe 5b. With this configuration, it is possible to increase the heat generation amount of the heater as the surface temperature of the good conductor pipe 5b becomes lower, so as to control the surface temperature of the good conductor pipe to a target temperature.

[0032] The humidifier 12 performs humidification in such a manner that the pressure of a water vapor entrained in a carbon dioxide containing gas becomes a saturated vapor pressure at the temperature of the carbon dioxide containing gas (full humidification). The humidifier 12 is formed by a water tank, an electric heater, a thermometer, and a hollow fiber membrane, for example.

[0033] To the DC power supply device 13, the anode electrode of the anode 7 is connected on its positive side and the cathode electrode of the cathode 4 is connected on its negative side. With this configuration, the DC power supply device 13 applies a positive voltage to the anode electrode of the anode 7. The negative side of the DC power supply device 13 is grounded.

[0034] All the good conductor pipes 5b, 8b, 9b, and 10b of the carbon-dioxide-containing gas supply pipe 5, the electrolyte supply pipe 8, the carbon-dioxide-containing gas discharge pipe 9, and the electrolyte discharge pipe 10 in which an electrolyte flows are connected to the ends of the cathode 4. Since the cathode 4 is connected to the ground, all the good conductor pipes 5b, 8b, 9b, and 10b are at a predetermined reference potential, for example, are placed at 0 volt being the ground potential. The ground potential may be called “earth potential”. Further, the reference potential can be set within a range in which the potentials of the good conductor pipes 5b, 8b, 9b, and 10b and the potential of a flowing material in a pipe near these pipes reduce a leakage current.

[0035] With this configuration, by including the DC power supply device 13 that applies a voltage between the electrodes of the anode 7 and the cathode 4 and supplying electricity to the electrolysis call stack, carbon dioxide CO2 supplied to the cathode 4 is reduced and a gas such as CO is produced. A reaction process in a case where carbon dioxide (CO2) is reduced to produce hydroxide ions (OH−) is described here.

[0036] When a current is supplied from a power controller 40 between the anode 7 and the cathode 4, water (H2O) and carbon dioxide (CO2) are reduced around the cathode 4 as represented by the following formula (1), and carbon monoxide (CO) and hydroxide ions (OH−) are produced. The hydroxide ions (OH−) are diffused around the anode 7 and are oxidized as represented by the following formula (2), so that oxygen (O2) is produced.2CO2+2H2O+4e−→2CO+4OH−  (1)4OH−→2H2O+O2+4e−  (2 )The electrolyte is a mixture of an ionic substance and a polar solvent. A configuration in which a gas is supplied to an anode and an electrolyte is supplied to a cathode may be employed.

[0038] The controller 20 functions as a control center controlling the operation of the electrolysis system 1. The controller 20 is a microcomputer provided with resources such as a CPU, a storage device, and an input / output device, for example. The controller 20 reads signals from various sensors (not illustrated) provided in the electrolysis system 1. The controller 20 sends an instruction to each of constituent elements of the electrolysis system 1 including the carbon-dioxide-containing gas supply device 3, the electrolyte supply device 6, the pipe temperature adjuster 11, the humidifier 12, and the DC power supply device 13, for example, based on the various signals that have been read and a control logic (a program) retained in advance in the controller 20. In this manner, the controller 20 performs overall management of the entire operations required for operating and stopping the electrolysis system 1 and controls the entire operations.

[0039] Even in a case where the carbon-dioxide-containing gas supply device 3 is formed by using a conductive stainless material, corrosion of the stainless material caused by a leakage current from the electrolysis cell stack 2 and leaching out of impurities do not occur, and there is no risk that impurities are mixed in the electrolysis cell stack 2 and cause deterioration of the electrolysis cell stack. Meanwhile, since there is liquid in the electrolyte supply device 6, the electrolyte supply pipe 8, and the electrolyte discharge pipe 9, the wetted parts are made of a resin material such as PP, PE, and PVC.

[0040] Since carbon monoxide CO, hydrogen, or the like, which is a combustible gas, flows in the carbon-dioxide-containing gas discharge pipe 9, an airtight pipe and another pipe or a device are connected to each other by a threaded fitting using a flange or a seal tape, a Swagelok fitting, or a Fujikin V-lok fitting, for example. Further, all the pipes are grounded in order to prevent generation of static electricity. Since a gasket of a flange, a seal tape, or the like of a sealing material of a connecting portion is not electrically conductive, crossover wiring is arranged between pipes and / or between a pipe and a device, and all pipes and devices through which hydrogen flows are configured to be connectable to the ground.

[0041] When a narrow pipe is connected to the center of a wide pipe, there is a risk that condensed water stays in the wide pipe to a level at which the narrow pipe is opened and flows irregularly, thus making gas supply irregular and causing generation of pipe corrosion due to convection. In a case where a narrow pipe is connected to a wide pipe, an eccentric reducer is used to cause condensed water generated on an upstream side to flow into the narrow pipe on a downstream side without staying.[1-2 Operations]

[0042] Operations according to the present embodiment are described. In order to prevent electrical leakage through an electrolyte flowing to the electrolysis cell stack 2 from the electrolyte supply pipe 8 when electrolysis is performed by applying a high voltage, the insulator pipe 8c of the electrolyte supply pipe 8, inside of which is made of an electrical insulating material, is connected to the electrolysis cell stack 2. The good conductor pipe 8b is further connected to the insulator pipe 8c, and is connected to the ground together with the negative side of the DC power supply device 13. With this process, the potential of the good conductor pipe 8b and the potential of the electrolyte near the good conductor pipe 8b approach 0 volt being a reference potential.

[0043] In order to prevent electrical leakage through the moisture in carbon dioxide gas flowing to the electrolysis cell stack 2 from the carbon-dioxide-containing gas supply pipe 5 when electrolysis is performed by applying a high voltage, the insulator pipe 5c of the carbon-dioxide-containing gas supply pipe 5, inside of which is made of an electrical insulating material, is connected to the electrolysis cell stack 2. The good conductor pipe 5b is further connected to that insulator pipe 5c, and is connected to the ground. Accordingly, the potential of the good conductor pipe 5b and the potential of carbon dioxide and the moisture near the good conductor pipe 5b approach 0 volt being a reference potential.

[0044] Parts that are in contact with the electrolysis cell stack 2 on the upstream side and the downstream side and in the cathode 4 and the anode 7 are the insulator pipes 5c, 8c, 9a, and 10a, are connected to the good conductor pipes 5b, 8b, 9b, and 10b, and are further connected to the insulator pipes 5a, 8a, 9c, and 10c. Accordingly, in a case where the potentials of the good conductor pipes 5b, 8b, 9b, and 10b and the electrolyte, the carbon dioxide gas, and the moisture near the good conductor pipes 5b, 8b, 9b, and 10b are not zero, transmission of electrical leakage from the electrolysis cell stack 2 to the insulator pipes 5a, 8a, 9c, and 10c that are not in contact with the electrolysis cell stack 2 is prevented by connection of the good conductor pipes 5b, 8b, 9b, and 10b to the ground.

[0045] By including the pipe temperature adjuster 11 on the good conductor pipe 5b between the insulator pipes 5a and 5c, the good conductor pipe 5b is heated.

[0046] FIG. 2 is a flowchart of a control example of the controller 20. The controller 20 drives the carbon-dioxide-containing gas supply device 3 and the electrolyte supply device 6 in a state where the good conductor pipes 5b, 8b, 9b, and 10b are at a predetermined reference potential (for example, the ground potential) (Step S100).

[0047] Subsequently, the controller 20 causes the DC power supply device 13 to start power supply (Step S102). In a state where the good conductor pipes 5b, 8b, 9b, and 10b are at the ground potential, the electrolysis cell stack 2 starts electrolysis (Step S104). The controller 20 ends the control process after a predetermined time elapses.

[0048] Accordingly, in a state where the potentials of the good conductor pipes 5b, 8b, 9b, and 10b and parts therearound are made closer to zero, the electrolysis cell stack 2 can perform electrolysis and a leakage current from the electrolysis cell stack 2 is reduced.[1-3 Effects]

[0049] Effects of the present embodiment are described. The insulator pipe 8c made of an electrical insulating material in the electrolyte supply pipe 8 is connected to the electrolysis cell stack 2. Further, the good conductor pipe 8b is connected to that insulator pipe 8c, and is connected to the ground via the negative side of the DC power supply device 13. Accordingly, it is possible to make the potential of the good conductor pipe 8b and the potential of the electrolyte near the good conductor pipe 8b closer to 0 volt as a reference potential, so that a leakage current can be reduced. Therefore, it is possible to prevent corrosion of the good conductor pipe 8b of the electrolyte supply pipe 8 caused by a leakage current and leaching out of impurities.

[0050] The insulator pipe 5c made of an electrical insulating material in the carbon-dioxide-containing gas supply pipe 5 is connected to the electrolysis cell stack 2. Further, the good conductor pipe 5b is connected to the insulator pipe 5c, and is connected to the ground via the negative side of the DC power supply device 13. Accordingly, it is possible to make the potential of the good conductor pipe 5b and the potential of carbon dioxide and the moisture near the good conductor pipe 5b closer to zero, so that a leakage current can be reduced. Therefore, it is possible to prevent corrosion of the good conductor pipe 5b of the carbon-dioxide-containing gas supply pipe 5 caused by a leakage current and leaching out of impurities.

[0051] Parts that are in contact with the electrolysis cell stack 2 on the upstream side and the downstream side and in the cathode 4 and the anode 7 are the insulator pipes 5c, 8c, 9a, and 10a, are connected to the good conductor pipes 5b, 8b, 9b, and 10b, and are further connected to the insulator pipes 5a, 8a, 9c, and 10c. Accordingly, the insulator pipes 5a, 5c, 8a, 8c, 9a, 9c, 10a, and 10c are prevented from being corroded by a leakage current from the electrolysis cell stack 2 and leaching out of impurities is reduced.

[0052] By including the pipe temperature adjuster 11 on the good conductor pipe 5b between the insulator pipes 5a and 5c and heating the good conductor pipe 5b, a humidification gas can be humidified, and condensation of the humidification gas can be prevented. That is, heating response is quick due to the good conductor pipe 5b, and it is easy to prevent condensation of the humidification gas. Further, since the heat dissipation amount from a pipe cannot be made zero even when a pipe is wrapped by a heat insulating material, the good conductor pipe 5b can be heated to a temperature of the humidification gas or higher.Second Embodiment

[0053] The electrolysis system 1 according to a second embodiment is different from the electrolysis system 1 according to the first embodiment in further including a ground fault detector 14. Differences from the electrolysis system 1 according to the first embodiment are described below.[2-1 Configuration]

[0054] A configuration of the second embodiment of the present invention is described with reference to FIG. 3. FIG. 3 is a diagram illustrating a configuration example of the electrolysis system 1 according to the second embodiment. As illustrated in FIG. 3, the ground fault detector 14 is provided between the ground and the negative side of the DC power supply device 13 to which an end of the cathode 4 of the electrolysis cell stack 2 is connected. The ground fault detector 14 is desirably a passive ground fault detector having high resistance so as to allow easy detection of a DC voltage leakage. For example, the ground fault detector 14 can detect a voltage change or a current change by grounding two high-resistance neutral points.[2-2 Operations]

[0055] Operations of the second embodiment of the present invention are described focusing on differences between the first embodiment and the second embodiment. When a ground fault occurs, a current value of a ground fault current is reduced by passing through the ground fault detector 14.[2-3 Effects]

[0056] Effects of the second embodiment of the present invention are described focusing on differences from the first embodiment. By using the ground fault detector 14, electrical leakage can be detected and troubles of an electrical device such as the DC power supply device 13 can be prevented. When a ground fault occurs, the current value of a ground fault current is reduced. Since Joule heat is a multiplication value of a voltage and a current, the heat generation amount when a ground fault occurs decreases as the current value becomes smaller and ignition can be further reduced.Third Embodiment

[0057] The electrolysis system 1 according to a third embodiment is different from the electrolysis system 1 according to the first embodiment in including an electrolyte cell-stack-entrance thermometer 15 that measures the temperature of an electrolyte before the electrolyte enters the electrolysis cell stack 2. Differences from the electrolysis system 1 according to the first embodiment are described below.[3-1 Configuration]

[0058] FIG. 4 is a diagram illustrating a configuration example of the electrolysis system 1 according to the third embodiment. As illustrated in FIG. 4, the electrolyte cell-stack-entrance thermometer 15 that measures the temperature of an electrolyte before the electrolyte enters the electrolysis cell stack 2 is provided.[3-2 Operations]

[0059] The controller 20 controls the pipe temperature adjuster 11 in accordance with the temperature measured by the electrolyte cell-stack-entrance thermometer 15. For example, the controller 20 controls the pipe temperature adjuster 11 in such a manner that the surface temperature of the good conductor pipe 5b becomes a temperature equal to or higher than the temperature measured by the electrolyte cell-stack-entrance thermometer 15.[3-3 Effects]

[0060] Since the temperature of an electrolyte before the electrolyte enters the electrolysis cell stack 2 measured by the electrolyte cell-stack-entrance thermometer 15 is dominant over the temperature of the electrolysis cell stack 2, and the good conductor pipe 5b is heated in accordance with the temperature of the electrolysis cell stack 2, it is possible to prevent a water vapor entrained in carbon dioxide gas entering the cell stack from being condensed in a pipe.Fourth Embodiment

[0061] The electrolysis system 1 according to a fourth embodiment is different from the electrolysis system 1 according to the third embodiment in that a pipe temperature adjuster 11c is installed also on the insulator pipe 5a. Differences from the electrolysis system 1 according to the third embodiment are described below.[4-1 Configuration]

[0062] FIG. 5 is a diagram illustrating a configuration example of the electrolysis system 1 according to the fourth embodiment. As illustrated in FIG. 5, the insulator pipe 5a includes a metallic part and the pipe temperature adjuster 11c also heats the metallic part. It is also permissible that the insulator pipe 5c further includes a metallic part and the pipe temperature adjuster 11c also heats the insulator pipe 5c. A heater in which a semiconductor heating element 11b having a self-temperature control function is continuously arranged to form a parallel circuit may be wound around the surface of the metallic part of the insulator pipe 5a or 5c. [4-2 Operations]

[0063] In the electrolysis system 1 according to the third embodiment, the pipe temperature adjuster 11 is installed only on the good conductor pipe 5b. However, by installing the pipe temperature adjuster 11c also on the insulator pipe 5a or 5c in which a metal with high thermal conductivity is arranged in the outer surface thereof and the inside thereof is made of an insulating material, the insulator pipe can also be heated.[4-3 Effects]

[0064] While the pipe temperature adjuster 11c is difficult to apply to the insulator pipes 5a and 5c entirely made of an insulating material for reasons of heat resistance, condensation caused by heat dissipation from carbon dioxide gas and the moisture entrained in the carbon dioxide gas can be prevented. Clogging with droplets in an electrolysis cell of the electrolysis cell stack 2 is prevented from occurring, and inhibition of electrochemical reaction of the electrolysis cell due to such clogging is also prevented. Since the degree of humidification of a gas is reduced by the amount corresponding to condensation, it is possible to prevent a diaphragm of the electrolysis cell from being dried locally.Fifth Embodiment

[0065] The electrolysis system 1 according to a fifth embodiment is different from the electrolysis system 1 according to the third embodiment in further including a carbon-containing-gas entrance thermometer 16 that measures the temperature of a carbon containing gas before the gas enters the electrolysis cell stack 2. Differences from the electrolysis system 1 according to the third embodiment are described below.[5-1 Configuration]

[0066] FIG. 6 is a diagram illustrating a configuration example of the electrolysis system 1 according to the fifth embodiment. As illustrated in FIG. 6, the electrolyte cell-stack-entrance thermometer 15 that measures the temperatures of an electrolyte before the electrolyte enters the electrolysis cell stack 2 and the carbon-containing-gas entrance thermometer 16 that measures the temperatures of a carbon containing gas before the gas enters the electrolysis cell stack 2 are provided. The entrance thermometers 15 and 16 can measure the surface temperatures of the good conductor pipes 5b and 8b, respectively.[5-2 Operations]

[0067] The controller 20 controls the pipe temperature adjuster 11 in accordance with the temperatures measured by the entrance thermometers 15 and 16. For example, the controller 20 executes control to make an entrance temperature of an electrolyte at the entrance of the electrolysis cell stack 2 and an entrance temperature of fully humidified CO2 at the entrance of the electrolysis cell stack 2 equal to each other.[5-3 Effects]

[0068] Heat dissipation cannot be made zero even by wrapping the pipe 5 with a heat insulating material. Therefore, even by controlling a humidification water temperature by the humidifier 12, for example, it is difficult to execute temperature control to make the entrance temperature of the electrolyte and the entrance temperature of fully humidified CO2 equal to each other. Meanwhile, the controller 20 controls the pipe temperature adjuster 11 in accordance with the temperatures measured by the electrolyte cell-stack-entrance thermometer 15 and the carbon-containing-gas entrance thermometer 16. Therefore, it is possible to execute control to make the entrance temperature of the electrolyte and the entrance temperature of fully humidified CO2 closer to each other.

[0069] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms and various omissions, substitutions, and changes may be made without departing from the spirit of the inventions. The embodiments and their modifications are intended to be included in the scope and the spirit of the invention and also in the scope of the invention and their equivalents described in the claims.

Claims

1. An electrolysis system comprising:an electrolysis cell stack configured to perform electrolysis by causing a gas and an electrolyte to flow to corresponding electrodes of an anode and a cathode and applying a voltage;a power supply device configured to apply a voltage between the electrode of the anode and the electrode of the cathode of the electrolysis cell stack;a gas supply device configured to supply the gas to one of the electrodes;an electrolyte supply device configured to supply the electrolyte to the other electrode;supply pipes configured to supply an anode fluid and a cathode fluid to the electrolysis cell stack; anddischarge pipes configured to discharge the anode fluid and the cathode fluid from the electrolysis cell stack, whereinat least one of the supply pipes and the discharge pipes include a plurality of insulator pipes inside of which is made of an electrical insulating material and a good conductor pipe made of a good conductor connected between the insulator pipes, the good conductor pipe being placed at a predetermined reference potential.

2. The system of claim 1, wherein the predetermined reference potential is a ground potential.

3. The system of claim 2, wherein the good conductor pipe is connected to the cathode of the electrolysis cell stack.

4. The system of claim 2, further comprising a passive ground fault detector connected to ground, whereinthe good conductor pipe is connected to the ground via the ground fault detector.

5. The system of claim 1, whereinone of the supply pipes that supplies the cathode fluid includes a plurality of insulator pipes inside of which is made of an electrical insulating material and a good conductor pipe made of a good conductor connected between the insulator pipes, andthe system further comprises a pipe temperature adjuster arranged on the good conductor pipe and coated to be insulated.

6. The system of claim 5, further comprising:a first entrance thermometer configured to measure a temperature of the electrolyte before the electrolyte enters the electrolysis cell stack; anda controller configured to control the pipe temperature adjuster in accordance with a temperature measured by the first entrance thermometer.

7. The system of claim 6, further comprising a second entrance thermometer configured to measure a temperature of the gas before the gas enters the electrolysis cell stack, whereinthe controller executes control based on a temperature of the first entrance thermometer and a temperature of the second entrance thermometer to make a temperature of the electrolyte before the electrolyte enters the electrolysis cell stack and a temperature of the gas before the gas enters the electrolysis cell stack match each other.

8. An electrolysis method of an electrolysis system, the electrolysis system comprising:an electrolysis cell stack configured to perform electrolysis by causing a gas and an electrolyte to flow to corresponding electrodes of an anode and a cathode and applying a voltage;a power supply device configured to apply a voltage between the electrode of the anode and the electrode of the cathode of the electrolysis cell stack;a gas supply device configured to supply the gas to one of the electrodes;an electrolyte supply device configured to supply the electrolyte to the other electrode;supply pipes configured to supply an anode fluid and a cathode fluid to the electrolysis cell stack; anddischarge pipes configured to discharge the anode fluid and the cathode fluid from the electrolysis cell stack, whereinat least one of the supply pipes and the discharge pipes include a plurality of insulator pipes inside of which is made of an electrical insulating material and a good conductor pipe made of a good conductor connected between the insulator pipes, the method comprisingdriving the power supply device, the gas supply device, and the electrolyte supply device in a state where the good conductor pipe is placed at a predetermined reference potential.

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