Electrolysis system
The electrolysis system addresses performance deterioration by controlling humidity and temperature during energized and unenergized periods, using a hollow fiber membrane and ion exchange devices to maintain efficiency and prevent impurity accumulation, thus extending component lifespan.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- KK TOSHIBA
- Filing Date
- 2023-03-22
- Publication Date
- 2026-07-01
AI Technical Summary
The deterioration of performance in electrolysis cells due to impurities, drying, and condensation during non-electrified periods is a challenge in existing electrolysis systems.
The system includes a control unit that switches between energized and unenergized periods, adjusting the absolute humidity and temperature of humidified gas and electrolyte to prevent impurity precipitation and condensation, using a hollow fiber membrane to filter particulates and ion exchange devices to purify the water, thereby maintaining electrolysis efficiency.
This approach effectively suppresses electrolysis cell deterioration, maintains efficiency, and extends the lifespan of components by preventing impurity accumulation and condensation, enhancing overall system performance.
Smart Images
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Abstract
Description
[Technical Field]
[0001] Embodiments of the present invention relate to an electrolysis system. [Background technology]
[0002] In recent years, electrolysis systems have become known. Electrolysis systems perform electrolysis by carrying out oxidation reactions at the anode and reduction reactions at the cathode. An electrolyte is passed through the anode, and a gas is passed through the cathode. [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Specification of Patent No. 5426990 [Overview of the project] [Problems that the invention aims to solve]
[0004] The problem that the embodiments of the present invention aim to solve is to suppress the deterioration of the performance of the electrolysis cell. [Means for solving the problem]
[0005] The electrolysis system of the embodiment comprises an electrolysis unit having an electrolysis cell having a cathode, an anode and a diaphragm between them; a gas supply device for supplying gas containing carbon dioxide; an electrolyte supply device for supplying electrolyte; and a humidifier for humidifying the gas from the gas supply device to generate humidified gas; a power supply unit for controlling the supply of power to the electrolysis cell, gas supply device, electrolyte supply device, and humidifier, respectively; and a control unit for controlling the electrolysis unit and the power supply unit. The control unit switches between an energizing period in which power is supplied to the electrolysis cell, electrolyte is supplied to the anode, and humidified gas is supplied to the cathode, and an unenergized period in which power is stopped from being supplied to the electrolysis cell, and humidified gas is supplied to the cathode or the cathode and anode. The humidifier is controlled so that the absolute humidity of the humidified gas during the unenergized period is lower than the absolute humidity of the humidified gas during the energized period. [Brief explanation of the drawing]
[0006] [Figure 1] This is a schematic diagram showing an example configuration of the electrolysis system of the first embodiment. [Figure 2] This is a flowchart illustrating an example of how electrolysis system 1 operates during the energization period. [Figure 3] This is a flowchart illustrating an example of how electrolysis system 1 operates during periods when it is not energized. [Figure 4] This is a flowchart illustrating an example of how the electrolysis system of the second embodiment operates. [Figure 5] This is a schematic diagram showing an example configuration of an electrolysis system according to the third embodiment. [Figure 6] This is a flowchart illustrating an example of how the electrolysis system of the third embodiment operates. [Figure 7] This is a schematic diagram showing an example configuration of the electrolysis system according to the fourth embodiment. [Figure 8] This is a schematic diagram showing an example configuration of the electrolysis system 1 of the fifth embodiment. [Modes for carrying out the invention]
[0007] The embodiments will be described below with reference to the drawings. The relationship between the thickness and planar dimensions of each component shown in the drawings, the ratio of the thicknesses of each component, etc., may differ from the actual objects. The vertical direction may differ from the vertical direction according to the acceleration due to gravity. In addition, in the embodiments, substantially identical components are denoted by the same reference numerals and their descriptions are omitted as appropriate.
[0008] In this specification, “connection” includes not only physical connections but also electrical connections, and unless otherwise specified, it includes not only direct connections but also indirect connections.
[0009] (First embodiment) Figure 1 is a schematic diagram showing an example configuration of an electrolysis system according to the first embodiment. The electrolysis system 1 includes an electrolysis unit 10, a power supply unit 20, and a control unit 30.
[0010] The electrolysis unit 10 is capable of performing electrolysis. The electrolysis unit 10 includes an electrolysis cell 101, a gas supply device 102, an electrolyte supply device 103, piping 104, piping 105, piping 106, piping 107, a humidifier 108, and a branch cutoff device 109. Each arrow shown in Figure 1 indicates the direction in which the corresponding fluid flows.
[0011] The electrolysis cell 101 has a cathode 111, an anode 112, and a diaphragm 113. The electrolysis unit 10 may have an electrolysis cell stack consisting of a stack of multiple electrolysis cells 101.
[0012] Cathode 111 has a cathode catalyst for reducing a target substance such as carbon dioxide to produce a cathode product. Examples of cathode products include carbon compounds such as carbon monoxide.
[0013] Anode 112 has an anode catalyst for oxidizing a target substance such as water to produce an anode product. Examples of anode products include oxygen.
[0014] The separator 113 is provided between the cathode 111 and the anode 112. The separator 113 separates the cathode 111 and the anode 112. The separator 113 has, for example, a porous membrane. Examples of the porous membrane include a polyethersulfone (PES) filtration membrane, an ion exchange membrane, and the like.
[0015] The gas supply device 102 can supply gas. The gas includes, for example, carbon dioxide. The gas supply device 102 may have a gas cylinder that stores carbon dioxide gas and a pressure reducing valve that controls the pressure of the gas.
[0016] The electrolyte supply device 103 can supply an electrolyte. The electrolyte contains an ionic substance. The ionic substance preferably includes at least one of, for example, hydroxide ions (OH - ), hydrogen ions (H + ), potassium ions (K + ), lithium ions (Li + ), and hydrogen carbonate ions (HCO3 - ). The electrolyte contains water. The electrolyte supply device 103 may have a pump. The electrolysis unit 10 may have a heater that heats the electrolyte.
[0017] The pipe 104 connects the gas supply device 102 and the inlet of the cathode 111.
[0018] The pipe 105 connects the electrolyte supply device 103 and the inlet of the anode 112. Since the ionic substance and water in the electrolyte are consumed by the electrolysis reaction, a pipe for supplying an electrolyte having a higher concentration than the electrolyte from the electrolyte supply device 103 or a pipe for supplying pure water may be connected to the pipe 105. A pipe for supplying an electrolyte having a higher concentration to the electrolyte supply device 103 or a pipe for supplying pure water may be connected.
[0019] The pipe 106 is connected to the outlet of the cathode 111. The pipe 106 is provided to discharge the cathode fluid discharged from the outlet of the cathode 111 to the outside. The cathode fluid contains substances such as, for example, carbon dioxide gas, water vapor, and cathode products.
[0020] The pipe 107 is connected to the outlet of the anode 112. The pipe 107 is provided to discharge the anode fluid discharged from the outlet of the anode 112 to the outside. The anode fluid includes substances such as electrolyte and anode products.
[0021] Pipes 104, 105, 106, and 107 can be formed using stainless steel materials such as SUS304 or SUS316.
[0022] The humidifier 108 can humidify the gas from the gas supply device 102 to produce humidified gas. Preferably, the humidified gas contains the same amount of water vapor as the saturated water vapor of the gas. The humidifier 108 is installed in the middle of the piping 104. An example of the humidifier 108 includes a hollow fiber membrane 180, a humidified water supply device 181, a temperature controller 182, and piping 183.
[0023] The hollow fiber membrane 180 is installed in the middle of the piping 104. For example, if a gas containing carbon dioxide flows inside the hollow fiber membrane 180 and humidifying water flows outside the hollow fiber membrane 180, a mixed gas of saturated water vapor at approximately the same temperature as the humidifying water and a gas containing carbon dioxide can be formed. Alternatively, a gas containing carbon dioxide may be flowed outside the hollow fiber membrane 180 and humidifying water may be flowed inside the hollow fiber membrane 180 to form a mixed gas of saturated water vapor at approximately the same temperature as the humidifying water and a gas containing carbon dioxide.
[0024] The humidifying water supply device 181 can supply humidifying water for humidifying the gas. The humidifying water supply device 181 can supply humidifying water to, for example, the outer inlet of the hollow fiber membrane 180. The humidifying water supply device 181 has, for example, a pump that can control the supply of humidifying water.
[0025] The temperature controller 182 can adjust the temperature of the humidifying water. The temperature controller 182 includes, for example, an electric heater that can heat the humidifying water and a thermometer that can measure the temperature of the humidifying water.
[0026] The piping 183 connects, for example, the inlet and outlet on the outside (humidifying water supply side) of the hollow fiber membrane 180. The piping 183 functions as a circulation channel for circulating the humidifying water. The humidifying water supply device 181 and the temperature controller 182 are installed in the middle of the piping 183. The piping 183 can be made using stainless steel material such as SUS304 or SUS316.
[0027] The branch shutoff device 109 can control the connection between pipe 104 and pipe 105. By connecting pipe 104 and pipe 105, the branch shutoff device 109 can supply humidified gas to cathode 111 and anode 112, respectively, via the humidifier 108. By disconnecting the connection between pipe 104 and pipe 105, the branch shutoff device 109 can supply humidified gas to cathode 111 without supplying humidified gas to anode 112. The branch shutoff device 109 has a solenoid valve or an electric valve.
[0028] The power supply unit 20 is connected to the electrolysis unit 10. The power supply unit 20 can, for example, supply power to the electrolysis cell 101, the gas supply device 102, the electrolyte supply device 103, the humidifier 108, and the branch circuit breaker 109. The power supply unit 20 has, for example, at least one power supply device. The power supply unit 20 may have multiple power supply devices for the electrolysis cell 101, the gas supply device 102, the electrolyte supply device 103, the humidifier 108, and the branch circuit breaker 109.
[0029] The control unit 30 is connected to the electrolysis unit 10 and the power supply unit 20, respectively. The control unit 30 can control the power supply to the electrolysis cell 101, the gas supply device 102, the electrolyte supply device 103, the humidifier 108, the branch circuit breaker 109, and the branch circuit breaker 109, for example, by controlling the power supply unit 20.
[0030] The control unit 30 may be configured using hardware such as a processor. Alternatively, each operation may be stored as an operation program on a computer-readable recording medium such as memory, and each operation may be executed by appropriately reading the operation program stored on the recording medium using hardware.
[0031] Next, an example of the operation method of the electrolysis system 1 will be described. The example of the operation method of the electrolysis system 1 includes an energizing period (when energized) in which power is supplied to the electrolysis cell 101, and an unenergized period (when unenergized) in which power is stopped from being supplied to the electrolysis cell 101. The energizing period is, for example, the period in which electrolysis is performed. The unenergized period is, for example, the period in which electrolysis is paused. The energizing period and the unenergized period can be switched by controlling the electrolysis unit 10 and the power supply unit 20 with the control unit 30.
[0032] Figure 2 is a flowchart illustrating an example of how the electrolysis system 1 operates during the energization period. Figure 2 shows steps S1, S2, S3, and S4. Steps S1 through S4 may be performed in order, for example, but are not limited to this order.
[0033] In step S1, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to close the branch circuit breaker 109 and disconnect the connection between pipe 104 and pipe 105.
[0034] In step S2, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20, thereby supplying humidified gas from the gas supply device 102 to the cathode 111 via the humidifier 108, and supplying electrolyte from the electrolyte supply device 103 to the anode 112.
[0035] In step S3, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to start supplying power to the electrolysis cell 101. Step S3 may be performed simultaneously with step S2.
[0036] In step S4, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to perform electrolysis by the electrolysis cell 101. Here, as an example, the case where the electrolytic solution contains water and the carbon compound contains carbon monoxide will be described.
[0037] The electrolysis cell 101 reduces carbon dioxide to produce carbon monoxide and oxidizes water to produce oxygen. Further, carbon dioxide may be reduced to produce hydroxide ions. Near the cathode 111, as shown in the following formula (1), water (H2O) and carbon dioxide (CO2) are reduced to produce carbon monoxide (CO) and hydroxide ions (OH - ). The hydroxide ions diffuse from the vicinity of the cathode 111 to the vicinity of the anode 112. The hydroxide ions are oxidized near the anode 112 to produce oxygen (O2) as shown in the following formula (2). The cathode fluid containing carbon dioxide, carbon monoxide, and hydroxide ions is discharged from the cathode 111 through the pipe 106. The anode fluid containing oxygen and the electrolytic solution is discharged through the pipe 107. 2CO2+2H2O+4e - →2CO+4OH - …(1) 4OH - →2H2O+O2+4e - …(2)
[0038] FIG. 3 is a flowchart for explaining an example of the operation method of the electrolysis system 1 during the non-electrified period. FIG. 3 shows step S11, step S12, step S13, and step S14. Steps S11 to S14 are performed, for example, in order, but are not limited to this order.
[0039] In step S11, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to stop the power supply to the electrolysis cell 101 and stop electrolysis. At this time, the supply of humidifying gas to the cathode 111 may be continued, and the supply of electrolyte to the anode 112 may be continued. The branch circuit breaker 109 remains closed and disconnects the connection between pipe 104 and pipe 105.
[0040] In step S12, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to lower the temperature of the humidified water to a level lower than the temperature of the humidified water during the energized period. The temperature of the humidified water can be lowered, for example, by lowering the heater output of the temperature controller 182. When the temperature of the humidified water decreases, the saturated water vapor decreases. As a result, the absolute humidity of the humidified gas during the non-energized period is lower than the absolute humidity of the humidified gas during the energized period. Note that the electrolysis unit 10 shown in Figure 1 does not have a bypass pipe connected in parallel to the hollow fiber membrane 180 that bypasses the hollow fiber membrane 180, nor a bypass shut-off valve that controls the opening and closing of the bypass pipe. However, by providing such a bypass pipe and shut-off valve, the absolute humidity of the gas can be lowered by not bypassing the hollow fiber membrane 180 during the energized period and bypassing the hollow fiber membrane 180 during the non-energized period. The branch cut-off device 109 remains closed and disconnects the connection between pipe 104 and pipe 105.
[0041] In step S13, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to open the branch circuit breaker 109 and connect the pipes 104 and 105.
[0042] In step S14, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to supply humidified gas with adjusted absolute humidity to the cathode 111 via piping 104 and to the anode 112 via piping 105. The branch cutoff device 109 is left open and connects piping 104 and piping 105. This allows, for example, the electrolyte in the anode 112 to be purged. Therefore, for example, deterioration of the anode 112 due to freezing can be suppressed.
[0043] When supplying gas to the electrolysis cell 101 during electrolysis, humidifying the gas can suppress the deposition of impurities and thus prevent a decrease in catalyst performance. Methods for humidifying the gas include bubbling by passing it through water in a tank heated by a heater, or humidifying it by passing the gas through a hollow fiber membrane through which hot water is flowing.
[0044] The bubbling method of humidification can cause droplets to flow downstream, potentially clogging the electrolysis cell 101. This can hinder the electrolysis of the electrolysis cell 101. To prevent droplet clogging, one option is to increase the tank volume to reduce the flow rate of droplets and gases, allowing gravity to settle the droplets. However, increasing the volume would increase the size of the humidifier 108.
[0045] One method of humidification using hollow fiber membranes involves, for example, flowing gas through the inside of a straw-shaped hollow fiber membrane and water through the outside. Since water vapor is supplied from the outside to the inside of the hollow fiber membrane solely through concentration diffusion, the gas can be humidified compactly within the small volume of the hollow fiber membrane space without the formation of liquid droplets. If the temperature of the humidifying water flowing through the hollow fiber membrane is higher than the gas temperature, the gas temperature can be raised. Similarly, if the temperature of the humidifying water flowing through the hollow fiber membrane is lower than the gas temperature, the gas temperature can be lowered. In the same way, with bubbling, the gas temperature can be raised or lowered depending on the temperature of the humidifying water.
[0046] If the electrolyte or humidifying water contains impurities, the performance of the electrolysis cell 101 may decrease. Impurities can be broadly classified into particulate matter that can be filtered and ionic substances such as metal ions that cannot be filtered and can only be adsorbed by ion exchange resin. For example, hollow fiber membranes can filter particulate matter, but they cannot adsorb ionic substances.
[0047] When the electrolysis cell 101 dries out, impurities contained in the electrolyte and humidified water precipitate inside the electrolysis cell 101, causing the electrolysis cell 101 to deteriorate and its performance to decline. Whether the impurities precipitate in the electrolysis cell 101 are particulate matter or ionic matter, the catalytic performance will decrease, and the porous membrane, which is the diaphragm 113 of the electrolysis cell 101, will harden, crack, and deteriorate. For example, if the humidifier 108 is not equipped with a hollow fiber membrane 180, particulate matter cannot be filtered, and particulate matter tends to accumulate in the electrolysis cell 101, making the diaphragm 113 of the electrolysis cell 101 more prone to hardening, cracking, and deterioration. For this reason, the electrolysis cell 101 needs to suppress drying and impurity precipitation even during periods when electrolysis is not being performed. The diaphragm 113 is susceptible to deterioration, such as rupture, due to the repeated wetting and drying cycles, which cause impurities to precipitate and put stress on it. When generating combustible gas by electrolysis in the electrolysis cell 101, the cell is purged with a non-combustible gas to prevent the combustible gas from accumulating in the electrolysis cell 101. In this case, it is preferable to purge with a moist non-combustible gas to suppress drying and thereby suppress the deposition of impurities in the electrolysis cell 101.
[0048] When electrolyte is supplied to the anode 112, if the diaphragm 113 is a porous membrane, even if the cathode 111 side is kept at high pressure to prevent electrolyte from seeping out to the cathode 111 side, if the gas on the cathode 111 side is dry, salt will precipitate on the cathode 111 side of the electrolyte, forming impurities and degrading the performance of the electrolysis cell 101.
[0049] When generating flammable gases by electrolysis, it is necessary to purge the electrolysis cell with a non-flammable gas during shutdown and storage to prevent the accumulation of flammable gases. This non-flammable gas also needs to be humidified to prevent impurities from precipitation in the electrolysis cell.
[0050] The electrolysis cell 101 performs electrolysis after raising the electrolyte temperature to an appropriate level, as this improves the efficiency of electrolysis. The appropriate temperature is, for example, between 40°C and 60°C. During electrolysis, the electrolyte temperature rises above the optimal level due to the heat generated by the electrolysis cell 101, so it is necessary to cool the electrolyte using a cooler such as a cooling tower or radiator. However, during periods when the power is not supplied, the electrolyte temperature will drop to room temperature or ambient temperature unless heated by a heater. Heating the electrolyte to the appropriate level by heating the heater during periods when the power is not supplied reduces the overall efficiency of the electrolysis system 1, so the heater output is reduced during periods when the power is not supplied.
[0051] During periods when the system is not powered, if a humidifying gas at a temperature higher than the temperature of the electrolysis cell 101 is supplied, the humidifying gas will condense inside the electrolysis cell 101. When the humidifying gas condenses, flooding occurs, inhibiting gas diffusion and reducing the electrolysis efficiency.
[0052] Therefore, by making the absolute humidity of the humidifying gas during the non-energized period lower than the absolute humidity of the humidifying gas during the energized period, condensation of the humidified water can be suppressed, thereby suppressing a decrease in electrolysis efficiency. When heating the electrolyte, heating the electrolyte to an appropriate temperature even during the non-energized period reduces the efficiency of the electrolysis system as a whole, so the output of the heater that heats the electrolyte may be reduced during the non-energized period. In the first embodiment, by using the hollow fiber membrane 180, particulate matter can be filtered, and the accumulation of particulate matter in the electrolysis cell 101 can be suppressed. This suppresses deterioration such as hardening and cracking of the diaphragm 113. In addition, the humidifier 108 using the hollow fiber membrane 180 can be made smaller than a bubbling-type humidifier.
[0053] The electrolysis unit 10 may have a structure in which the outlet of the anode 112 is connected to the electrolyte supply device 103, and the electrolyte circulates from the outlet of the anode 112 to the electrolyte supply device 103. Furthermore, a heater may be provided in the electrolyte supply device 103 to heat the electrolyte to a suitable temperature for electrolysis of the electrolysis cell 101, which is between 40°C and 60°C. In this case, when the supply of humidifying gas to the cathode 111 is stopped during the non-energized period, it is preferable to reduce or stop the output of the heater to lower the temperature of the electrolyte to ambient temperature, thereby suppressing the condensation of water vapor from the electrolyte supplied to the anode 112 at the cathode 111.
[0054] (Second embodiment) Figure 4 is a flowchart illustrating an example of the operation method of the electrolysis system of the second embodiment. The electrolysis system of the second embodiment differs from the electrolysis system of the first embodiment in that it continues to supply electrolyte to the anode 112 during the non-energized period, gradually lowering the absolute humidity of the humidified gas. The differences from the first embodiment will be described below, and the description of the first embodiment can be appropriately referenced for other parts.
[0055] Figure 4 shows steps S21, S22, and S23. Steps S21 through S23 can be performed in order, for example, but are not limited to this order.
[0056] In step S21, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to stop the power supply to the electrolysis cell 101 and stop the electrolysis. The branch circuit breaker 109 remains closed and disconnects the connection between pipe 104 and pipe 105.
[0057] In step S22, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to continue supplying electrolyte from the electrolyte supply device 103. At this time, the supply of humidifying gas to the cathode 111 is continued. The temperature of the electrolyte will decrease to the ambient temperature due to heat dissipation unless a heater is installed and the heater output is adjusted so that the temperature is higher than the temperature during the energization period. The branch circuit breaker 109 remains closed and disconnects the connection between pipe 104 and pipe 105.
[0058] In step S23, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to lower the temperature of the humidified water to a level lower than the temperature of the humidified water during the energization period. At this time, in order to gradually lower the temperature of the humidified water to the ambient temperature, the control unit 30 controls the output of the heater of the temperature controller 182 to gradually decrease. This allows the absolute humidity of the humidified gas to gradually decrease until it approaches the saturated water vapor at the ambient temperature. After lowering the absolute humidity of the humidified gas to the saturated water vapor at the ambient temperature, the supply of gas from the gas supply device 102 may be stopped. If there is a risk of the electrolysis cell 101 freezing due to an ambient temperature below freezing, it is preferable to control the temperature of the electrolyte and humidified water using the heater and temperature controller 182 so that they do not fall below, for example, 4°C. That is, it is preferable that the temperatures of the electrolyte and humidified water be adjusted to be above 4°C.
[0059] If the relative humidity of the gas is too low, the membrane 113 will dry out and deteriorate, so it is necessary to humidify the gas. When the electrolysis cell 101, which is performing an exothermic reaction called electrolysis, is stopped, the temperature of the electrolysis cell gradually decreases to the ambient temperature due to heat dissipation. In order to suppress the condensation of the humidified gas inside the electrolysis cell 101 during the non-energized period, it is preferable to gradually lower the temperature of the humidifying water, for example, until the absolute humidity of the humidified gas approaches the saturated water vapor at the ambient temperature, and then stop supplying the humidified gas. Furthermore, by continuing to supply the electrolyte to the anode 112 during the non-energized period, the evaporation of moisture from the anode 112 can be suppressed, thereby preventing the anode 112 from drying out and deteriorating.
[0060] (Third embodiment) Figure 5 is a schematic diagram showing an example configuration of the electrolysis system of the third embodiment. The electrolysis system 1 of the third embodiment differs from the electrolysis system 1 of the first embodiment in that it further includes a thermometer 160 and a thermometer 170. The parts that differ from the first embodiment will be described below, and for other parts, the description of the first embodiment can be appropriately referred to.
[0061] The thermometer 160 can measure the temperature of the cathode fluid discharged from the outlet of the cathode 111. The thermometer 160 is connected to the outlet of the cathode 111. The thermometer 160 may be installed, for example, in the middle of the piping 106.
[0062] The thermometer 170 can measure the temperature of the anode fluid discharged from the outlet of the anode 112. The thermometer 170 is connected to the outlet of the anode 112. The thermometer 170 may be installed, for example, in the middle of the piping 107.
[0063] Thermometers 160 and 170 may have, for example, a platinum resistance thermometer, a thermocouple, or a thermistor. Thermometers 160 and 170 may transmit, for example, a data signal indicating the measured temperature to the control unit 30. This allows the control unit 30 to generate a control signal based on the data signal, and to control the humidifier 108 based on the control signal from the control unit 30, for example, to adjust the temperature of the humidifying water.
[0064] Figure 6 is a flowchart illustrating an example of the operation method of the electrolysis system according to the third embodiment. Figure 6 shows steps S31, S32, and S33. Steps S31 through S33 can be performed in order, for example, but are not limited to this order.
[0065] In step S31, the control unit 30 controls the power supply unit 20 to stop the supply of power to the electrolysis cell 101 and stop the electrolysis. The branch circuit breaker 109 remains closed and disconnects the connection between pipe 104 and pipe 105.
[0066] In step S32, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to continue supplying electrolyte from the electrolyte supply device 103. At this time, the supply of humidifying gas to the cathode 111 is continued. The temperature of the electrolyte will decrease to the ambient temperature due to heat dissipation unless a heater is installed and the output of the heater is adjusted to be higher than the temperature during the energization period. The branch circuit breaker 109 remains closed and disconnects the connection between pipe 104 and pipe 105.
[0067] In step S33, the control unit 30 controls the electrolysis unit 10 and the power supply unit 20 to lower the temperature of the humidified water to a level lower than the temperature of the humidified water during the energized period. In step S33, humidified water at a temperature higher than the temperature measured by thermometers 160 and 170 is flowed through the hollow fiber membrane 180 to humidify the gas from the gas supply device 102. The temperature of the electrolysis cell 101, which has stopped the exothermic electrolysis reaction, gradually decreases to the ambient temperature due to heat dissipation. In order to suppress the condensation of the humidified gas inside the electrolysis cell 101 during the non-energized period, it is preferable, as in the second embodiment, to gradually lower the temperature of the humidified water until the absolute humidity of the humidified gas approaches the saturated water vapor at the ambient temperature, and then stop supplying the humidified gas.
[0068] If a humidifying gas at a temperature higher than the temperature of the electrolysis cell 101 is supplied, the humidifying gas will condense inside the electrolysis cell 101. When the humidifying gas condenses, flooding occurs, inhibiting gas diffusion and reducing the electrolysis efficiency. To suppress this, it is preferable to measure the temperature inside the electrolysis cell 101 by measuring the temperature of the cathode fluid or anode fluid discharged from the electrolysis cell 101, and to adjust the temperature of the humidifying water so that it is higher than the measured temperature. If the temperature of the humidifying water is not adjusted by the humidifying water temperature regulator based on the temperature of the cathode fluid or anode fluid, the humidifying gas remaining inside the electrolysis cell after purging (scavenging) the electrolysis cell with the humidifying gas after stopping electrolysis may condense, causing flooding of the electrolysis cell 101 and reducing the electrolysis efficiency when electrolysis is restarted.
[0069] The temperatures measured by thermometers 160 and 170 are greatly influenced by the internal temperature of the electrolysis cell 101, and will be, for example, equivalent to the temperature of the electrolysis cell 101. Therefore, by flowing humidified water at a temperature higher than that measured by thermometers 160 and 170 through the hollow fiber membrane 180 and humidifying the gas from the gas supply device 102, the inside of the electrolysis cell 101 becomes humid, and salt precipitation due to drying can be suppressed. In addition, by continuing to supply electrolyte to the anode 112 during periods when the power is not supplied, evaporation of moisture from the anode 112 can be suppressed, and the deterioration of the anode 112 due to drying can be prevented.
[0070] (Fourth embodiment) Figure 7 is a schematic diagram showing an example configuration of the electrolysis system of the fourth embodiment. The electrolysis system 1 of the fourth embodiment differs from the electrolysis system 1 of the third embodiment in that the humidifier 108 further includes a tank 184, an ion exchange device 185, piping 186, a flow regulator 187, piping 188, and an ion exchange device 189. The parts that differ from the third embodiment will be described below, and the description of the third embodiment can be appropriately referenced for other parts.
[0071] Tank 184 can hold humidified water. Tank 184 is located in the middle of piping 183, between the humidified water supply device 181 and the flow regulator 187. The temperature of the humidified water in tank 184 is controlled by a temperature regulator 182. The temperature regulator 182 may have an electric heater and a thermometer. Examples of electric heaters include a sheathed heater placed inside tank 184 and a jacket heater wrapped around the outer surface of tank 184. Jacket heaters can reduce the elution of impurities. A jacket heater, for example, has a heating element and an insulating material such as glass cloth covering the outer circumference of the heating element.
[0072] The ion exchange device 185 is installed in the middle of the piping 186. The piping 186 connects a water supply source (not shown) to the tank 184. The piping 186 can be made using stainless steel material such as SUS304 or SUS316.
[0073] The ion exchange device 185 can remove impurities from the makeup water flowing from the makeup water supply source through the piping 186 and supply it to the tank 184. The makeup water supplied to the tank 184 contains components equivalent to, for example, humidifying water. Examples of impurities include iron and silica. The ion exchange device 185 has an ion exchange resin that can remove ionic substances. Examples of makeup water supply sources include tap water. The makeup water supply source may have another tank that holds the makeup water and supply it to the tank 184 from the other tank using gravity. It is preferable that the makeup water supply source does not supply makeup water if the pressure is extremely low compared to the humidifying gas flowing through the hollow fiber membrane 180. If the pressure is extremely high, the hollow fiber membrane 180 may be damaged.
[0074] The flow regulator 187 connects the hollow fiber membrane 180 and the tank 184. The flow regulator 187 can adjust the flow rate of humidified water discharged from the outer outlet of the hollow fiber membrane 180 to the ion exchange device 189. The flow regulator 187 has, for example, an orifice.
[0075] The piping 188 is connected in parallel with the flow regulator 187 and connects the hollow fiber membrane 180 and the tank 184. The piping 188 can bypass the flow regulator 187. The piping 188 can be made from stainless steel material such as SUS304 or SUS316.
[0076] The ion exchange device 189 is installed in the middle of the piping 188. The ion exchange device 189 can remove impurities from the humidified water flowing through the piping 188. Examples of impurities include iron, silica, etc.
[0077] The electrolysis system 1 of the fourth embodiment can, for example, purify the supply water using an ion exchange device 185 before supplying it to the tank 184. The humidifying water supply device 181 supplies humidifying water from the tank 184. After the humidifying water passes through the hollow fiber membrane 180, a portion flows to the flow regulator 187 and returns to the tank 184, while the remainder flows through the piping 188, is purified by the ion exchange device 189, and then returns to the tank 184.
[0078] In the electrolysis system 1 of the fourth embodiment, the replenishment water purified by the ion exchange device 185 is stored in the tank 184, making it easier to adjust the temperature of the humidifying water with the temperature controller 182. For example, if the temperature controller 182 is stopped or its output is reduced during a period when the power is not supplied, the temperature of the humidifying water will decrease. However, by raising the temperature of only the humidifying water inside the tank 184 to the desired temperature and then restarting the humidifying water supply device 181, humidifying water at the desired temperature can be supplied to the hollow fiber membrane 180.
[0079] If the humidifier 108 has a tank 184, impurities will accumulate inside the tank 184. However, by providing an ion exchange device 189, the humidified water can be purified by the ion exchange device 189. When humidifying gas through a hollow fiber membrane 180, deterioration due to impurities in the hollow fiber membrane 180 can be suppressed, as well as deterioration of the electrolysis cell 101. By supplying humidified water to the hollow fiber membrane 180, branching the downstream flow of the hollow fiber membrane 180 to supply a portion to the tank 184 via the ion exchange device 189, and supplying the remainder directly to the tank 184, not all of the humidified water is supplied to the ion exchange device 189. This makes it possible to extend the lifespan of the ion exchange device 189, miniaturize it, and reduce costs by decreasing the frequency of replacement.
[0080] Furthermore, the humidified water used to humidify the gas in the hollow fiber membrane 180 can be replenished with purified supply water. The tank 184 is located downstream of the hollow fiber membrane 180 and stores the humidified water after it has passed through the hollow fiber membrane 180. Therefore, impurities dissolved in the supply water source, the hollow fiber membrane 180, and the humidified water supply device 181 tend to accumulate in the humidified water in the tank 184. In contrast, in the fourth embodiment, a portion of the humidified water after it has passed through the hollow fiber membrane 180 is purified by the ion exchange device 189, thereby suppressing the accumulation of impurities in the humidified water in the tank 184.
[0081] (Fifth embodiment) Figure 8 is a schematic diagram showing an example configuration of the electrolysis system 1 of the fifth embodiment. The electrolysis system 1 of the fifth embodiment differs from the electrolysis system 1 of the third embodiment in that the humidifier 108 further includes a tank 184, an ion exchange device 185, piping 186, and an ion exchange device 189, and does not have a hollow fiber membrane 180. The parts that differ from the third embodiment will be described below, and the description of the third embodiment can be appropriately referred to for other parts.
[0082] Tank 184 can hold humidifying water. Tank 184 is installed in the middle of piping 104 and in the middle of piping 183. The temperature of the humidifying water in tank 184 is controlled by a temperature controller 182. Further description of the temperature controller 182 can be appropriately referenced from the description of the fourth embodiment.
[0083] The ion exchange device 185 is installed in the middle of the piping 186. The piping 186 connects a makeup water supply source (not shown) to the tank 184. The ion exchange device 185 can remove impurities from the water flowing from the makeup water supply source through the piping 186 and supply it to the tank 184. Examples of impurities include iron and silica. The ion exchange device 185 has an ion exchange resin that can remove ionic substances. Examples of the makeup water supply source include tap water. The makeup water supply source may have another tank that holds the makeup water and supply it to the tank 184 from the other tank using gravity.
[0084] The ion exchange device 189 is installed in the middle of the piping 183. The ion exchange device 189 can remove impurities from the humidified water flowing through the piping 183. Examples of impurities include iron, silica, etc.
[0085] In the fifth embodiment, humidifying gas is generated by passing gas through the humidifying water inside the tank 184 to create a bubbling effect. The humidifying water is then supplied from the humidifying water supply device 181 to the ion exchange device 189 via the tank 184.
[0086] The humidified water used to humidify the gas in tank 184, which has decreased in volume, can be replenished with purified supply water. Impurities dissolved in the supply water source and humidified water supply device 181 tend to accumulate in the humidified water in tank 184. In contrast, in the fifth embodiment, a portion of the humidified water is purified by the ion exchange device 189, thereby suppressing the accumulation of impurities in the humidified water in tank 184.
[0087] The hollow fiber membrane 180 deteriorates due to impurities and other factors, requiring replacement at a frequency such as once a year, which incurs costs. As in the fifth embodiment, maintenance is unnecessary if a bubbling method is used. Furthermore, impurities in the makeup water can be removed by supplying makeup water to the tank 184 via the ion exchange device 185.
[0088] The first to fifth embodiments can be combined as appropriate.
[0089] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]
[0090] 1... Electrolysis system, 10... Electrolysis unit, 20... Power supply unit, 30... Control unit, 101... Electrolysis cell, 102... Gas supply device, 103... Electrolyte supply device, 104... Piping, 105... Piping, 106... Piping, 107... Piping, 108... Humidifier, 109... Branch cutoff device, 111... Cathode, 112... Anode, 113... Diaphragm, 160... Thermometer, 170... Thermometer, 180... Hollow fiber membrane, 181... Humidifying water supply device, 182... Temperature regulator, 183... Piping, 184... Tank, 185... Ion exchange device, 186... Piping, 187... Flow regulator, 188... Piping, 189... Ion exchange device.
Claims
1. An electrolysis unit comprising: an electrolysis cell having a cathode, an anode and a diaphragm between them; a gas supply device for supplying a gas containing carbon dioxide; an electrolyte supply device for supplying an electrolyte; and a humidifier device for humidifying the gas from the gas supply device to generate a humidified gas. A power supply unit that controls the supply of power to each of the electrolysis cell, the gas supply device, the electrolyte supply device, and the humidifier, A control unit that controls the electrolysis unit and the power supply unit, An electrolysis system comprising, The control unit, A period during which power is supplied to the electrolysis cell, the electrolyte is supplied to the anode, and the humidifying gas is supplied to the cathode, A period during which power is stopped from being supplied to the electrolysis cell and the humidifying gas is supplied to the cathode or the cathode and the anode, Switch, The humidifier is controlled such that the absolute humidity of the humidifying gas during the non-energized period is lower than the absolute humidity of the humidifying gas during the energized period. The electrolysis unit is A first pipe connecting the gas supply device and the cathode inlet, A second pipe connecting the electrolyte supply device and the anode inlet, A branch circuit breaker that controls the connection between the first pipe and the second pipe, It further possesses, During the period when no power is supplied, the electrolysis system stops supplying power to the electrolysis cell, stops supplying the electrolyte, and connects the first and second pipes using the branch circuit breaker to supply the humidifying gas to the cathode and anode. Electrolysis system.
2. The electrolysis unit is The system further comprises at least one thermometer selected from the group consisting of a first thermometer connected to the outlet of the cathode and measuring the temperature of a first fluid discharged from the outlet of the cathode, and a second thermometer connected to the outlet of the anode and measuring the temperature of a second fluid discharged from the outlet of the anode, The humidifier is, A hollow fiber membrane having an inner side through which the gas passes and an outer side through which humidifying water flows for humidifying the gas, A humidifying water supply device that supplies the humidifying water to the outside of the hollow fiber membrane, A temperature controller for adjusting the temperature of the humidifying water, It has, The electrolysis system according to claim 1, wherein the temperature controller is controlled such that, during the period when no power is supplied, the temperature of the humidified water is higher than the temperature measured by the at least one thermometer.
3. The humidifier is, A hollow fiber membrane having an inner side through which the gas passes and an outer side through which humidifying water flows for humidifying the gas, A humidifying water supply device that supplies the humidifying water to the outer inlet of the hollow fiber membrane, A tank for containing the humidified water discharged from the outer outlet of the hollow fiber membrane, A temperature regulator for adjusting the temperature of the humidifying water in the tank, A first ion exchange device for purifying the makeup water supplied to the tank, A third pipe connecting the outer outlet of the hollow fiber membrane to the tank, A flow regulator connected in parallel to the third pipe, which adjusts the flow rate of the humidifying water discharged from the outer outlet of the hollow fiber membrane to the tank, A second ion exchange device is provided in the middle of the third piping and purifies the humidified water discharged from the outer outlet of the hollow fiber membrane, The electrolysis system according to claim 1, comprising:
4. The humidifier is, A tank for containing humidifying water to humidify the gas from the gas supply device by bubbling, A temperature regulator for adjusting the temperature of the humidifying water in the tank, A humidifying water supply device that supplies the humidifying water to the tank, A first ion exchange device for purifying the makeup water supplied to the tank, A second ion exchange device for purifying the humidifying water supplied from the humidifying water supply device, The electrolysis system according to claim 1, comprising: