Electrolytic apparatus and electrolysis method

Abstract

To suppress a decline in an electrolytic efficiency.SOLUTION: An electrolytic apparatus comprises: an electrolysis cell; a cathode supply flow path in which a cathode supply fluid including a carbon dioxide gas flows; an anode supply flow path in which an anode supply fluid including water flows; a cathode discharge flow path in which a cathode discharge fluid including a carbon compound and a carbon dioxide flows; an anode discharge flow path in which an anode discharge fluid including oxygen and water flows; a cathode flow rate adjuster for adjusting the flow rate A of the cathode supply fluid; an anode flow rate adjuster for adjusting the flow rate B of the anode supply fluid; a first flow rate meter for measuring the flow rate C of the cathode discharge fluid; a second flow rate meter for measuring the flow rate D of the anode discharge fluid; and a control device. The control device estimates a Faraday efficiency value according to a relational expression that approximates a Faraday efficiency value of the carbon compound as a function including the flow rate C and the flow rate D, and controls the flow rate A by controlling the cathode flow rate adjuster according to the estimated Faraday efficiency value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to an electrolysis apparatus and an electrolysis method. [Background technology]

[0002] In recent years, concerns have arisen about the depletion of fossil fuels such as oil and coal, and expectations are growing for sustainable renewable energy sources. Examples of renewable energy sources include solar cells and wind power generation. However, these have the challenge of making it difficult to provide a stable supply of electricity because the amount of power they generate depends on weather and natural conditions. For this reason, attempts have been made to stabilize the power supply by storing the electricity generated by renewable energy sources in storage batteries. However, storing electricity comes with problems such as the cost of storage batteries and the occurrence of losses during storage.

[0003] In response to these issues, electrolysis devices using renewable energy-generated electricity to electrolyze water (HO) to produce hydrogen (H) from water, or electrochemically reduce carbon dioxide (CO) to convert it into chemical substances (chemical energy) such as carbon compounds like carbon monoxide (CO), formic acid (HCOOH), methanol (CHOH), methane (CH), acetic acid (CHCOOH), ethanol (CHOH), ethane (CH), and ethylene (CH). Storing these chemical substances in cylinders or tanks offers the advantages of lower energy storage costs and less storage loss compared to storing electricity (electrical energy) in batteries. One example of a carbon dioxide electrolysis device under development is one that uses a silver nanoparticle catalyst at the cathode to reduce carbon dioxide and convert it to carbon monoxide. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Zengcal Liu et al., Journal of CO2 Utilization, 15, p.50-56(2015) [Non-patent document 2] Sinchao Ma et al., Journal of The Electrochemical Society, 161(10), F1124-F1131(2014) Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to suppress the decrease in electrolysis efficiency. [Means for solving the problem]

[0006] The electrolysis device of the embodiment includes an electrolysis cell having a cathode that reduces carbon dioxide to produce carbon compounds, an anode that oxidizes water to produce oxygen, a cathode flow path facing the cathode, and an anode flow path facing the anode; a cathode supply flow path connected to an inlet of the cathode flow path and through which a cathode supply fluid containing carbon dioxide gas flows, the cathode supply flow path being connected to the inlet of the anode flow path and through which the anode supply fluid containing water flows, and a cathode discharge flow path connected to an outlet of the cathode flow path and through which a cathode discharge fluid that is discharged from the cathode flow path and contains the carbon compounds and the carbon dioxide flows. an anode discharge flow path connected to the outlet of the anode flow path, through which an anode discharge fluid discharged from the anode flow path and containing the oxygen and the water flows; a cathode flow rate regulator that adjusts a flow rate A of the cathode supply fluid supplied to the cathode flow path; an anode flow rate regulator that adjusts a flow rate B of the anode supply fluid supplied to the anode flow path; a first flow meter that measures a flow rate C of the cathode discharge fluid discharged from the cathode flow path; a second flow meter that measures a flow rate D of the anode discharge fluid discharged from the anode flow path; and a control device that receives measurement data of the flow rate C from the first flow meter and measurement data of the flow rate D from the second flow meter. The control device uses the measurement data of the flow rate C and the measurement data of the flow rate D to estimate the value of the Faraday efficiency of the carbon compound according to a relational expression that approximates the value of the Faraday efficiency to a function including the flow rates C and D, and controls the flow rate A by controlling the cathode flow rate regulator in accordance with the estimated value of the Faraday efficiency. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration example of an electrolysis device according to an embodiment. [Figure 2] FIG. 10 is a schematic diagram showing a modified example of the electrolysis device of the embodiment. [Figure 3] FIG. 10 is a schematic diagram showing a modified example of the electrolysis device of the embodiment. [Figure 4] FIG. 1 is a diagram showing the relationship between FECO and x. [Figure 5] FIG. 10 is a diagram showing the relationship between FECH4 and x. [Figure 6] FIG. 1 is a diagram showing the relationship between FEC2H4 and x. [Figure 7] FIG. 1 is a diagram showing the relationship between FEC2H6 and x. [Figure 8] FIG. 1 is a diagram showing the relationship between FECO and x. [Figure 9] FIG. 10 is a diagram showing the relationship between FECH4 and x. [Figure 10] FIG. 1 is a diagram showing the relationship between FEC2H4 and x. [Figure 11] FIG. 1 is a diagram showing the relationship between FEC2H6 and x. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, electrolysis devices according to embodiments will be described with reference to the drawings. In each of the following embodiments, substantially identical components are denoted by the same reference numerals, and some of their descriptions may be omitted. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each component, etc. may differ from the actual ones.

[0009] In this specification, unless otherwise specified, "connect" may include not only direct connection but also indirect connection.

[0010] Fig. 1 is a schematic diagram illustrating an example of the configuration of an electrolysis device according to an embodiment. Fig. 1 shows an electrolysis device 1. The electrolysis device 1 includes an electrolysis unit 100, an anode supply unit 200, a cathode supply unit 300, a cathode discharge unit 400, and a control unit 500.

[0011] The electrolysis unit 100 includes an anode 111, an anode flow path 112, an anode current collector 113, a cathode 121, a cathode flow path 122, a cathode current collector 123, and a separator 131. The anode 111, the anode flow path 112, the cathode 121, the cathode flow path 122, and the separator 131 constitute an electrolysis cell. An example of an electrolysis cell is a carbon dioxide electrolysis cell. The electrolysis unit 100 may also include a cell stack formed by stacking multiple electrolysis cells. The multiple electrolysis cells may be sandwiched between a pair of support plates, for example, and further fastened with bolts or the like.

[0012] The anode supply section 200 includes an anode collector 201 , an anode flow rate regulator 202 , and an anode pressure regulator 203 .

[0013] The cathode supply unit 300 includes a supply source 301 , a cathode flow regulator 302 , and a cathode pressure regulator 303 .

[0014] The cathode exhaust section 400 includes a cathode collector 401 .

[0015] The control unit 500 includes a control device 501 .

[0016] The anode 111 is in contact with the separator 131. The anode 111 is an electrode for oxidizing an object to be oxidized (a substance to be oxidized) to generate an oxidation product. The anode 111 oxidizes, for example, water to be oxidized to generate oxygen (O) and hydrogen ions (H + ) or hydroxide ions (OH - ) to produce oxygen and water.

[0017] The anode 111 preferably contains a catalytic material (anode catalytic material) capable of reducing the overvoltage of the oxidation reaction. Examples of such catalytic materials include metals such as platinum (Pt), palladium (Pd), and nickel (Ni), alloys and intermetallic compounds containing these metals, binary metal oxides such as manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), ruthenium oxide (Ru-O), lithium oxide (Li-O), and lanthanum oxide (La-O), ternary metal oxides such as Ni-Co-O, Ni-Fe-O, La-Co-O, Ni-La-O, and Sr-Fe-O, quaternary metal oxides such as Pb-Ru-Ir-O and La-Sr-Co-O, and metal complexes such as Ru complexes and Fe complexes.

[0018] The anode 111 includes a substrate having a porous structure, such as a mesh material, punched material, porous material, or sintered metal fiber material, that allows for the transfer of liquid or ions between the separator 131 and the anode flow path 112. The substrate may be made of a metal material such as titanium (Ti), nickel (Ni), or iron (Fe), or an alloy containing at least one of these metals (e.g., SUS), or may be made of the above-mentioned anode catalyst material. When an oxide is used as the anode catalyst material, it is preferable to form a catalyst layer by adhering or laminating the anode catalyst material to the surface of a substrate made of the above-mentioned metal material. The anode catalyst material preferably contains nanoparticles, nanostructures, nanowires, or the like to enhance the oxidation reaction. A nanostructure is a structure in which nanoscale irregularities are formed on the surface of a catalyst material.

[0019] The cathode 121 is in contact with the separator 131. The cathode 121 is an electrode (reduction electrode) for causing a reduction reaction of a reduction target (a substance to be reduced) and generating a reduction product. Examples of the reduction target include carbon dioxide. Examples of the reduction product include carbon compounds and ammonia. Examples of carbon compounds include carbon monoxide, formic acid (HCOOH), ethane, ethylene, methanol, acetic acid (CHCOOH), ethanol, propanol (CHOH), and ethylene glycol (CHO). The reduction reaction at the cathode 121 may include a side reaction of causing a reduction reaction of water to generate hydrogen (H) in addition to the reduction reaction of the reduction target.

[0020] The cathode 121 has a gas diffusion layer and a cathode catalyst layer provided on the gas diffusion layer. A porous layer denser than the gas diffusion layer may be disposed between the gas diffusion layer and the cathode catalyst layer. The gas diffusion layer is disposed on the cathode flow channel 122 side, and the cathode catalyst layer is disposed on the separator 131 side. The cathode catalyst layer may be embedded in the gas diffusion layer. The cathode catalyst layer preferably contains catalyst nanoparticles or catalyst nanostructures. The gas diffusion layer is made of, for example, carbon paper or carbon cloth, and may be treated to be water-repellent. The porous layer is made of a porous material with a smaller pore size than the carbon paper or carbon cloth.

[0021] By applying an appropriate water-repellent treatment to the gas diffusion layer, the target gas reaches the cathode catalyst layer mainly by gas diffusion. The reduction reaction of the target gas and the resulting carbon compound occurs near the boundary between the gas diffusion layer and the cathode catalyst layer, or near the cathode catalyst layer that has penetrated into the gas diffusion layer.

[0022] The cathode catalyst layer is preferably made of a catalyst material (cathode catalyst material) capable of reducing the overvoltage of the reduction reaction when reducing carbon dioxide. Examples of such materials include metals such as gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), titanium (Ti), cadmium (Cd), zinc (Zn), indium (In), gallium (Ga), lead (Pb), and tin (Sn), metal materials such as alloys and intermetallic compounds containing at least one of these metals, carbon materials such as carbon (C), graphene, carbon nanotubes (CNTs), fullerenes, and ketjen black, and metal complexes such as Ru complexes and Re complexes. The cathode catalyst layer can be in various shapes, such as a plate, mesh, wire, particle, porous, thin film, or island shape.

[0023] The cathode catalyst material constituting the cathode catalyst layer preferably comprises nanoparticles of the above-mentioned metal material, nanostructures of the metal material, nanowires of the metal material, or a composite in which nanoparticles of the above-mentioned metal material are supported on a carbon material such as carbon particles, carbon nanotubes, graphene, etc. By using catalyst nanoparticles, catalyst nanostructures, catalyst nanowires, catalyst nanosupport structures, etc. as the cathode catalyst material, the reaction efficiency of the reduction reaction of the target substance to be reduced in the cathode 121 can be increased.

[0024] The anode flow channel 112 faces the anode 111. The anode flow channel 112 has a function of supplying the anode 111 with the object to be oxidized by allowing an anode solution containing the object to be oxidized to flow therethrough.

[0025] The anode solution is preferably a solution containing at least water (H2O) to be oxidized. The substance to be reduced is supplied from the cathode flow channel 122, so the anode solution may or may not contain the substance to be reduced.

[0026] The anode solution may be an electrolytic solution containing an electrolyte, such as hydroxide ions (OH - ), hydrogen ions (H+ ), potassium ions (K + ), sodium ions (Na + ), lithium ion (Li + ), chloride ions (Cl - ), bromide ion (Br - ), iodide ion (I - ), nitrate ions (NO3 - ), sulfate ions (SO4 2- ), phosphate ions (PO4 2- ), borate ion (BO3 3- ), and bicarbonate ions (HCO3 - ) is an example of an aqueous solution containing at least one selected from the group consisting of: a) anode solution (anode solution containing at least one of the following electrolytes): ...

[0027] The anode flow path 112 is provided on the surface of a flow path plate 114. The material of the flow path plate 114 includes, for example, a material that has low chemical reactivity and no electrical conductivity. Examples of such materials include insulating resin materials such as acrylic resin, polyether ether ketone (PEEK), and fluororesin. The flow path plate 114 has screw holes for fastening (not shown).

[0028] The cathode flow channel 122 faces the cathode 121. The cathode flow channel 122 has a function of supplying the cathode 121 with the substance to be reduced by allowing a cathode gas containing the substance to be reduced to flow therethrough.

[0029] The cathode flow path 122 is provided on the surface of a flow path plate 124. The flow path plate 124 is preferably made of a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as Ti and SUS, and carbon. The flow path plate 124 has an inlet and outlet for the cathode flow path 122, not shown, as well as screw holes for fastening. Furthermore, packing not shown may be inserted in front of and behind each flow path plate as needed.

[0030] The separator 131 includes an ion exchange membrane that allows ions to move between the anode 111 and the cathode 121 and that can separate the anode 111 and the cathode 121. Examples of ion exchange membranes include cation exchange membranes such as Nafion and Flemion, and anion exchange membranes such as Neosepta and Selemion. In addition to ion exchange membranes, any material that allows ions to move between the anode 111 and the cathode 121, such as a glass filter, a porous polymer membrane, or a porous insulating material, may be used for the separator 131.

[0031] The anode 111 and the cathode 121 can be connected to a power source 150. Examples of the power source 150 are not limited to a normal power grid or a battery, and may include a power source that supplies power generated by renewable energy such as solar cells or wind power. The power source 150 may further include a power controller that adjusts the output of the power source to control the voltage between the anode 111 and the cathode 121. The power source 150 may be provided outside the electrolysis device 1.

[0032] The inlet of the anode flow channel 112 is connected to the anode supply flow channel P1. The outlet of the anode flow channel 112 is connected to the anode discharge flow channel P2. The anode supply flow channel P1 and the anode discharge flow channel P2 are formed of, for example, piping.

[0033] An inlet of the cathode flow channel 122 is connected to a cathode supply flow channel P3. An outlet of the cathode flow channel 122 is connected to a cathode discharge flow channel P4. The cathode supply flow channel P3 and the cathode discharge flow channel P4 are formed of, for example, piping.

[0034] The temperature of the electrolysis unit 100 can be measured using a temperature regulator 153 provided in the electrolysis device 1. The temperature regulator 153 may measure the external temperature of the electrolysis cell. The temperature regulator 153 may be provided in contact with the electrolysis cell, or may be connected to the electrolysis cell.

[0035] As the reaction progresses, the electrolysis unit 100 generates heat and the temperature rises. The temperature rise needs to be controlled within a certain range so as not to deviate from the optimal operating conditions of the electrolyte membrane and cell components. For this reason, a cooling device for cooling the electrolysis unit 100 may be provided in the temperature regulator 153. The cooling device can cool the electrolysis unit 100 by being controlled by the control unit 500 in accordance with the temperature detected by the temperature regulator 153, for example. The temperature regulator 153 may also have a heater that can heat the electrolysis unit 100 by being controlled by the control unit 500 in accordance with the detected temperature.

[0036] The anode collector 201 is connected to the anode discharge flow path P2. The anode collector 201 includes an anode tank that can store the anode fluid discharged from the anode flow path 112 and flowing through the anode discharge flow path P2, and an anode gas-liquid separator that separates the anode fluid into an anode effluent and an anode exhaust. The anode effluent contains an anode solution. The anode effluent is returned to the anode supply flow path P1 via a circulation flow path P5 that connects the anode supply flow path P1 and the anode exhaust flow path P2, and is reused as the anode solution. The anode exhaust contains oxidation products and water vapor. The anode exhaust may also contain unreacted substances to be oxidized.

[0037] The anode flow rate regulator 202 is provided midway along the anode supply flow path P1. The anode flow rate regulator 202 has, for example, a pump, and controls the flow rate (anode inlet flow rate: flow rate B) of the anode supply fluid supplied to the anode flow path 112 via the anode supply flow path P1.

[0038] The anode pressure regulator 203 is provided in the anode exhaust flow path P2. The anode pressure regulator 203 controls the pressure in the anode flow path 112 by controlling the pressure in the anode exhaust flow path P2.

[0039] The flow rate of the anode discharge fluid discharged from the anode flow channel 112 can be measured using a flow meter 151 provided in the electrolysis device 1. The flow meter 151 can measure the flow rate of the anode discharge fluid discharged from the anode flow channel 112 (anode outlet flow rate: flow rate D). The flow meter 151 may be provided downstream of the anode flow channel 112 and upstream of the anode pressure regulator 203. The flow meter 151 may be provided midway along the anode discharge flow channel P2, or may be connected to the anode discharge flow channel P2.

[0040] The supply source 301 includes, for example, a cylinder cabinet that can accommodate a cathode supply fluid containing a substance to be reduced. The cathode supply fluid includes, for example, carbon dioxide gas. The cathode supply fluid may also include water vapor by humidifying the carbon dioxide gas.

[0041] The cathode flow rate regulator 302 is provided midway along the cathode supply flow path P3. The cathode flow rate regulator 302 has, for example, a pump, and can control the flow rate of the cathode supply fluid supplied to the cathode flow path 122 (cathode inlet flow rate: flow rate A).

[0042] The cathode pressure regulator 303 is provided midway through the cathode exhaust flow path P4. The cathode pressure regulator 303 can control the pressure in the cathode flow path 122 by controlling the pressure in the cathode exhaust flow path P4.

[0043] The flow rate of the cathode discharge fluid discharged from the cathode flow channel 122 can be measured using a flow meter 152 provided in the electrolysis device 1. The flow meter 152 can measure the flow rate of the cathode discharge fluid discharged from the cathode flow channel 122 (cathode outlet flow rate: flow rate C). The flow meter 152 may be provided downstream of the cathode flow channel 122 and upstream of the cathode pressure regulator 303. The flow meter 152 may be provided midway along the cathode discharge flow channel P4, or may be connected to the cathode discharge flow channel P4.

[0044] The cathode collector 401 is connected to the cathode discharge flow path P4. The cathode collector 401 includes a tank that can store the cathode fluid discharged from the cathode flow path 122 and flowing through the cathode discharge flow path P4, and a gas-liquid separator that separates the cathode fluid into a cathode effluent and a cathode exhaust. The cathode exhaust contains reduction products and hydrogen gas and water vapor resulting from side reactions. The cathode effluent may contain an anode solution. The cathode effluent may also contain unreacted substances to be reduced.

[0045] The cathode exhaust may be supplied from the cathode collector 401 to a subsequent stage 600, as shown in Fig. 2. Fig. 2 is a schematic diagram showing a modified example of the electrolysis device of the embodiment. The electrolysis device 1 shown in Fig. 2 differs from the electrolysis device 1 shown in Fig. 1 in that it includes a subsequent stage 600; for other parts, the description of the electrolysis device 1 shown in Fig. 1 can be used as appropriate. The subsequent stage 600 includes a subsequent device 601 and a hydrogen supply source 602.

[0046] The downstream device 601 is provided downstream of the electrolysis device 1. The downstream device 601 can generate compounds through a chemical reaction using carbon compounds and hydrogen contained in the cathode discharge fluid. Examples of the downstream device 601 include chemical synthesis reaction devices such as water electrolysis devices and hydrogen generators.

[0047] The control device 501 receives detection signals from, for example, the flow meter 151, the flow meter 152, and the temperature regulator 153, and transmits a control signal to the anode flow regulator 202. The control device 501 is electrically connected to each component via bidirectional signal lines, some of which are not shown, and controls these components collectively. Note that each pipe is provided with a valve or a pump (not shown), and the opening and closing operations of the valve or pump may be controlled by a signal from the control device 501. The control device 501 may be connected to a subsequent device 601. The control device 501 may be connected to at least one device of the power supply 150, the anode pressure regulator 203, the cathode pressure regulator 303, and the temperature regulator 153.

[0048] The control device 501 may be connected to, for example, an anode pressure regulator 203, an anode flow rate regulator 202, a hydrogen supply source 602, etc., as shown in Fig. 3. Fig. 3 is a schematic diagram showing a modified example of the electrolysis device of the embodiment. For other parts, the description of Fig. 2 can be used as appropriate.

[0049] The controller 501 may collect data indicative of at least one of electrical cell outputs, such as cell voltage, cell current, cathode potential, anode potential, pressure and pressure drop in the cathode flow channel 122, and pressure and pressure drop in the anode flow channel 112, for example.

[0050] The control device 501 may be configured using hardware that uses, for example, a processor, etc. Each operation may be stored as an operation program in a computer-readable recording medium such as a memory, and each operation may be executed by the hardware by appropriately reading out the operation program stored in the recording medium.

[0051] The electrolysis device 1 may have an energy converter 701 and an energy converter 702, as shown in Fig. 3. Fig. 3 is a schematic diagram showing a modified example of the electrolysis device. For other parts, the description of the electrolysis device 1 shown in Fig. 2 can be used as appropriate.

[0052] The energy converter 701 is provided midway through the anode discharge flow path P2. The energy converter 701 may be provided upstream or downstream of the anode flow rate regulator 202. The energy converter 701 includes, for example, a gear. The energy converter 701 can acquire kinetic energy from the anode discharge fluid flowing through the anode discharge flow path P2 and convert the kinetic energy into electrical energy or rotational energy.

[0053] The energy converter 702 is provided midway through the cathode discharge flow path P4. The energy converter 702 may be provided upstream or downstream of the cathode flow rate regulator 302. The energy converter 702 includes, for example, a gear. The energy converter 702 can acquire kinetic energy from the cathode discharge fluid flowing through the cathode discharge flow path P4 and convert the kinetic energy into electrical energy or rotational energy.

[0054] Next, a description will be given of an example of an electrolysis method using the electrolysis device 1. In this example of the electrolysis method, the anode flow rate regulator 202 and the anode pressure regulator 203 are controlled to supply an anode supply fluid to the anode flow path 112 via the anode supply flow path P1, the cathode flow rate regulator 302 and the cathode pressure regulator 303 are controlled to supply a cathode supply fluid from a supply source 301 to the cathode flow path 122 via the cathode supply flow path P3, and a voltage is applied between the anode current collector 113 and the cathode current collector 123 from the power source 150 to supply a current to the electrolysis cell via the anode 111 and the cathode 121.

[0055] When a current is passed through the anode 111 and the cathode 121, an oxidation reaction occurs near the anode 111 and a reduction reaction occurs near the cathode 121, as shown below. Here, a case where carbon dioxide, which is the object of reduction, is reduced to produce the reduction product carbon monoxide (CO), is described. However, the reduction product is not limited to carbon monoxide, and may be other carbon compounds such as the organic compounds mentioned above. In addition, the reaction process in the electrolytic cell mainly produces hydrogen ions (H + ) or mainly hydroxide ions (OH -), but the reaction is not limited to any of these reactions.

[0056] It mainly oxidizes water (H2O) to produce hydrogen ions (H + When a current is supplied between the anode 111 and the cathode 121, an oxidation reaction of water (H2O) occurs at the anode 111, which is in contact with the anode solution flowing through the anode flow path 112. Specifically, as shown in the following formula (1), the H2O contained in the anode solution is oxidized to produce oxygen (O2) and hydrogen ions (H + ) is generated. 2H2O → 4H + +O2+4e - …(1)

[0057] H generated at anode 111 + The electrons move through the cathode gas in the cathode flow channel 122 via the anode 111 and the separator 131 and reach the vicinity of the cathode 121. - ) and H that has moved to the vicinity of cathode 121 + This causes a reduction reaction of carbon dioxide (CO2). Specifically, as shown in the following formula (2), CO2 contained in the cathode gas supplied from the cathode flow channel 122 to the cathode 121 is reduced to produce CO. 2CO2+4H + +4e - → 2CO+2H2O …(2)

[0058] Next, carbon dioxide (CO2) is mainly reduced to hydroxide ions (OH - When a current is supplied between the anode 111 and the cathode 121, water (HO) and carbon dioxide (CO) are reduced near the cathode 121 to produce carbon monoxide (CO) and hydroxide ions (OH), as shown in the following formula (3): - ) and hydroxide ions (OH - ) diffuses to the vicinity of the anode 111 and converts into hydroxide ions (OH- ) is oxidized to produce oxygen (O2). 2CO2+2H2O+4e - → 2CO+4OH - …(3) 4OH - → 2H2O+O2+4e - …(4)

[0059] As described above, when an electrolysis device is operated for a long period of time, hydrogen is generated due to a side reaction. The amount of hydrogen may increase depending on operating conditions such as the temperature of the electrolysis cell, the amount of current flowing through the electrolysis cell, operating time, and start / stop timing. Therefore, it is necessary to change the operating conditions of the electrolysis cell according to changes in the Faraday efficiency.

[0060] Furthermore, it is necessary to adjust the flow rates of the carbon compounds and hydrogen supplied to the equipment installed in the downstream equipment 601 depending on the flow rates of the hydrogen and carbon compounds produced by the electrolytic cell. For this reason, it is conceivable to measure the composition of the produced gas in order to measure the Faraday efficiency of each component, but this poses the problem that the measuring equipment is expensive, which increases the cost of the entire system.

[0061] Furthermore, the pump for supplying the fluid to the electrolysis cell requires energy for its operation, which reduces the efficiency of the pump as an energy conversion device.

[0062] In response to this, the electrolysis device 1 uses the control device 501 to estimate parameters such as the Faraday efficiency using measurement data of the flow rate D (anode outlet flow rate) from the flow meter 151 and measurement data of the flow rate C (cathode outlet flow rate) from the flow meter 152, and if the estimated values ​​of these parameters do not satisfy the required standards for operating the electrolysis device 1, the control device 501 performs an operation to change the operating conditions of the electrolysis device 1. Examples of the operation to change the operating conditions include control of the cathode flow rate regulator 302 to change the flow rate A. Controlling the operating conditions can, for example, restore the output of the electrolysis cell. Furthermore, controlling the operating conditions can detect an abnormality in the electrolysis reaction in the electrolysis cell and stop the operation of the electrolysis cell. This can suppress a decrease in electrolysis efficiency.

[0063] Faraday efficiency of carbon monoxide FE CO and the Faraday efficiency of hydrogen, FE H2 The Faraday efficiency of the electrolytic cell can be calculated by gas chromatography or infrared spectroscopy, or by mixing the electrolytic cell with an oxygen-containing gas, burning it over a catalyst such as platinum, and measuring the temperature. It can also be calculated using parameters such as the voltage and current supplied to the electrolytic cell, the temperature of the electrolytic cell, and the performance of gas-liquid separation between the anode flow channel 112 and the cathode flow channel 122, i.e., the amount of fluid (liquid, gas, etc.) moving between the anode flow channel 112 and the cathode flow channel 122, the amount of product gas, and the voltage difference with a reference electrode. While it is possible to comprehensively predict the Faraday efficiency using these parameters, it is difficult to make an accurate judgment.

[0064] When carbon dioxide is reduced to produce carbon monoxide in the electrolysis unit 100, it is assumed that the same molar amount of carbon dioxide as the amount of carbon monoxide produced moves from the cathode flow channel 122 to the anode flow channel 112.

[0065] For example, when carbon monoxide is produced, a two-electron reaction causes the same molar amount of carbon dioxide to move to the anode flow channel 112. When methane or ethylene is produced, a six-electron reaction causes three moles of carbon dioxide to move to the anode flow channel 112. When ethane is produced, an eight-electron reaction causes half the number of electrons in the reduction reaction of four moles of carbon dioxide to move to the anode flow channel 112.

[0066] The total current value (total reaction current value) I flowing through the electrolysis cells and cell stacks in the electrolysis unit 100 can be calculated by multiplying the current density by the electrode area by the number of stacked cells.

[0067] The amount of carbon monoxide produced (flow rate) is calculated by: Total current (total reaction current) I (A) × 60 (s) / 96500 (c / mol) / 2 (number of reaction electrons) × 22400 (cc / mol) × FE COThe value 60 (s) is used to calculate coulombs from the current value x time (s (seconds)), and is included for unit conversion since the amount produced is calculated in flow rate (ccm). 22400 (cc / mol) represents the volume of gas per mole.

[0068] The amount of hydrogen produced (flow rate) is I(A) × 60(s) / 96500(c / mol) / 2(number of reaction electrons) × 22400(cc / mol) × (1-FE CO ) can be calculated as follows.

[0069] The amount (flow rate) of carbon dioxide moving to the anode flow channel 112 is the same as the amount of carbon monoxide produced, and is calculated as follows: I(A)×60(s) / 96500(c / mol) / 2(number of reaction electrons)×22400(cc / mol)×FE CO It can be calculated as follows.

[0070] The amount (flow rate) of oxygen generated by the anode 111 can be calculated by the total current value (A)×60 (s) / 96500 (c / mol) / 22400 (cc / mol).

[0071] The amount (flow rate) of carbon dioxide supplied to the cathode flow path 122 must be twice the amount converted to carbon monoxide, and can be calculated by total current value (A) × 60 (s) / 96,500 (c / mol) / 2 (number of reaction electrons) × 22,400 (cc / mol) × 2.

[0072] The flow rate of carbon dioxide contained in the cathode supply fluid supplied to the cathode flow channel 122 minus the flow rate of carbon dioxide required for conversion to monocarbon dioxide is defined as the flow rate a of excess carbon dioxide.

[0073] The operation based on the flow rates C and D can be determined from the ratio of these flow rates. When the value obtained by subtracting the flow rate a from the flow rate C and dividing the flow rate D by the result is defined as x, x can be calculated as x = D / (Ca).

[0074] At this time, the Faraday efficiency of carbon monoxide, FE CO is as follows, FE COcan be estimated according to a relational expression that approximates a quadratic function involving x. FE CO =14.778x 2 -99.006x+205.41

[0075] The theoretical value of the flow rate of carbon dioxide required for the reduction reaction can be calculated by multiplying the total current value by 13.93. CO When the flow rate A decreases, the control device 501 controls the cathode flow regulator 302 to reduce the flow rate A in accordance with the amount of the product. In the gas components containing carbon monoxide and hydrogen, a reduced amount of carbon dioxide is preferable for the hydrocarbon generator in the downstream device 601.

[0076] However, if the flow rate A is reduced, the reaction conditions become more severe, and the FE CO Therefore, FE CO When the flow rate A decreases, the reaction is made milder by increasing the flow rate A. CO It is possible to maintain

[0077] FE CO When is 1.0 (100%), x is 1.33, and FE CO As x decreases, as shown in Figure 4, if the electrolytic cell is operated under the condition that a constant multiple of (x-1.33) is added to the theoretical amount of carbon dioxide, FE CO It is preferable to maintain the FE. Adding one time (x-1.33) produces an effect, but if it is less than that, almost no effect is obtained. On the other hand, adding more than 10 times (x-1.33) is not preferable because the cathode discharge fluid is too diluted, which requires a carbon dioxide separation step for use in the reaction in the subsequent device 601, or the reaction efficiency of the subsequent device 601 decreases. For this reason, the control device 501 COIt is preferable to control the flow rate A so as to satisfy the formula I×13.93+(x−1.33)×1≦A≦I×13.93+(x−1.33)×10 by controlling the cathode flow rate regulator 302 in accordance with the estimated value of I×13.93+(x−1.33)×10. 13.93 is a value calculated by 60(s) / 96500(c / mol) / 2(number of reaction electrons)×22400(cc / mol)×2.

[0078] This relationship holds when the reduction product is carbon monoxide gas from a two-electron reaction. However, this relationship may no longer hold when a liquid product is produced as a reduction product, or when multiple reaction products are produced in large proportions. This is the case when the reduction reaction is primarily gaseous and produces a single reduction product. Furthermore, this relationship is prone to large errors unless the Faraday efficiency of the single reduction product is 90% or higher.

[0079] Next, the Faraday efficiency FE when the reduction product is methane in an 8-electron reaction CH4 When the reduction product is methane, CO2 + 8H + +8e - → A reaction based on the reaction formula CH4 + 2H2O occurs. Eight electrons are required for one molecule of carbon dioxide, and one molecule of methane is produced, and four molecules of carbon dioxide move from the cathode flow path 122 to the anode flow path 112. At this time, FE CH4 is as follows, FE CH4 can be estimated according to a relational expression that approximates a quadratic function involving x. FE CH4 =12.053x 2 -73.921x+152.92

[0080] FE CH4 When is 1.0 (100%), x is 0.83, and FE CH4 As x decreases, as shown in Figure 5, if the constant multiple of (x-0.83) is added to the theoretical amount of carbon dioxide, FE CH4 Therefore, the control device 501 is CH4It is preferable to control the flow rate A so as to satisfy the equation expressed by I×13.93+(x−0.83)×1≦A≦I×13.93+(x−0.83)×12 by controlling the cathode flow rate regulator 302 in accordance with the estimated value of I×13.93+(x−0.83)×12.

[0081] In the case of carbon monoxide, which undergoes a two-electron reaction, the ratio was 10 times (x-1.33). However, in the case of methane, which undergoes an eight-electron reaction, the change in the Faraday efficiency and the rate of increase of x are different compared to carbon monoxide. Therefore, adding more than 12 times (x-1.33) is undesirable because the cathode discharge fluid becomes too diluted. This ratio is higher than the 10 times ratio for the two-electron reaction, but because separating methane and carbon dioxide is easier than separating carbon monoxide and carbon dioxide, a ratio of up to 12 times is preferable. Methane is easily liquefied and can be easily separated by liquefaction, such as by cryogenic methods. A ratio exceeding this ratio is undesirable because the cathode discharge fluid becomes too diluted, requiring a carbon dioxide separation process for use in the reaction in downstream device 601 or reducing the reaction efficiency of downstream device 601.

[0082] Next, the faradaic efficiency FE when the reduction product is ethylene, a six-electron reaction C2H4 When the reduction product is ethylene, 2CO2 + 12H + +12e - → A reaction based on the reaction formula C2H4 + 4H2O occurs. Six electrons are required for one molecule of carbon dioxide, and one molecule of ethylene is produced, and three molecules of carbon dioxide move from the cathode flow channel 122 to the anode flow channel 112. At this time, FE C2H4 is as follows, FE C2H4 can be estimated according to a relational expression that approximates a quadratic function involving x. FE C2H4 =12.317x 2 -73.313x+157.79

[0083] FE C2H4 When is 1.0 (100%), x is 0.89, and FE C2H4As x decreases, as shown in Figure 6, if the constant multiple of (x-0.89) is added to the theoretical amount of carbon dioxide, FE C2H4 Therefore, the control device 501 is C2H4 It is preferable to control the flow rate A so as to satisfy the equation expressed by I×13.93+(x−0.89)×1≦A≦I×13.93+(x−0.89)×12 by controlling the cathode flow rate regulator 302 in accordance with the estimated value of I×13.93+(x−0.89)×12.

[0084] In the case of ethylene, which is a six-electron reaction, the change in the Faraday efficiency and the rate of increase of x are different from those of carbon monoxide, so adding more than 12 times (x - 0.89) is undesirable because the cathode discharge fluid becomes too diluted. Because it is easier to separate ethylene and carbon dioxide than carbon monoxide and carbon dioxide, a maximum of 12 times is preferable rather than 10 times. A factor exceeding this is undesirable because the cathode discharge fluid becomes diluted, which requires a carbon dioxide separation step for use in a reaction in the downstream device 601, or reduces the reaction efficiency of the downstream device 601.

[0085] Next, the Faraday efficiency FE when the reduction product is ethane in an eight-electron reaction C2H6 When the reduction product is ethane, 2CO2 + 16H + +16e - → A reaction based on the reaction formula C2H6 + 4H2O occurs. Eight electrons are required for one molecule of carbon dioxide, and one molecule of ethane is produced, and four molecules of carbon dioxide move from the cathode flow channel 122 to the anode flow channel 112. At this time, FE C2H6 is as follows, FE C2H6 can be estimated according to a relational expression that approximates a quadratic function involving x. FE C2H6 =12.053x 2 -73.921x+152.91

[0086] FE C2H6 When is 1.0 (100%), x is 0.83, and FE C2H6As x decreases, as shown in Figure 7, if the constant multiple of (x-0.83) is added to the theoretical amount of carbon dioxide, FE C2H6 Therefore, the control device 501 is C2H4 It is preferable to control the flow rate A so as to satisfy the equation expressed by I×13.93+(x−0.83)×1≦A≦I×13.93+(x−0.83)×12 by controlling the cathode flow regulator 302 in accordance with the estimated value of I×13.93+(x−0.83)×12.

[0087] In the case of ethane, which undergoes an eight-electron reaction, the change in the Faraday efficiency and the rate of increase of x are different from those of carbon monoxide. Therefore, adding more than 12 times (x - 0.83) is undesirable because the cathode exhaust fluid becomes too diluted. Because it is easier to separate ethane and carbon dioxide than carbon monoxide and carbon dioxide, a maximum of 12 times is preferable rather than 10 times. A factor exceeding this is undesirable because the cathode exhaust fluid becomes diluted, which, for example, requires a carbon dioxide separation step for use in a reaction in the downstream device 601, or reduces the reaction efficiency of the downstream device 601.

[0088] In order to measure the flow rates C and D more accurately, it is preferable to measure the volumetric flow rate of the substance (substance flow rate, in other words, molar flow rate). It is difficult to measure the flow rate of a fluid that contains a mixture of carbon compounds such as carbon monoxide, hydrogen, carbon dioxide, and oxygen, and the ratio of each component is not fixed.

[0089] Fluid flow rates can typically be measured using measuring devices such as soap film flow meters or cylinder-type volumetric flow meters, but these devices are difficult to implement due to issues such as their large size, high cost, complex operation, and difficulty in automated measurement. Because the anode flow path 112 forms a two-layer gas-liquid flow of gas and electrolyte, the volumetric flow rate of the fluid can be calculated by detecting the large amounts of gas and liquid flowing through the path and determining their flow velocities. In this case, it is preferable to install a flow meter upstream of the anode collector 201, such as a trap tank, which separates the anode discharge fluid into gas and liquid.

[0090] On the other hand, the cathode discharge fluid may contain water vapor at the same temperature as the electrolysis cell. Because the cell temperature is higher than the ambient temperature due to the heat of reaction, water vapor will condense and turn into liquid inside the piping unless it is kept warm. Therefore, the volumetric flow rate can be calculated by detecting the liquid flowing in the large amount of gas flowing through the piping along the anode 111 and determining its flow rate. In this case, it is necessary to calculate the amount of saturated water vapor from the piping temperature and subtract the water vapor flow rate from the flow rate of the cathode discharge fluid. In this case, it is preferable to install a flow meter upstream of the cathode collector 401, which has a trap tank or the like that separates the gas and liquid of the cathode discharge fluid discharged from the cathode flow path 122.

[0091] However, determining the volumetric flow rate of a fluid is difficult. Thermal mass flow meters, on the other hand, offer a simple way to measure flow rate. Thermal mass flow meters have an internal thermal mass sensor. They measure the temperature before or after a heater installed in at least one of the flow paths or bypass sections. The temperature difference generated by the fluid's flow rate determines the flow rate, and from that temperature difference, the flow rate can be calculated. Thermal mass flow meters typically use an element whose electrical resistance changes with temperature, detecting the difference in resistance before and after the element in a bridge circuit. In the case of a bypass, the total flow rate can be calculated by calculating the split flow ratio. However, this method has issues, such as its inability to be used with different gases; therefore, it is manufactured based on nitrogen. For different gases, the conversion factor (CF), which represents the difference in flow rate depending on the gas type, can be adjusted. The CF for hydrogen and carbon monoxide is 1.0, the same as for nitrogen, while the CF for carbon dioxide is 0.74.

[0092] Although thermal mass flow meters can measure gases of different types, they have the drawback of being unable to measure gases containing multiple components in different ratios. Therefore, they cannot be directly applied to gases discharged from the cathode, such as carbon dioxide electrolysis cells, where the ratio of components in the cathode discharge fluid changes.

[0093] The electrolysis device 1 satisfies the conditions that the amount of carbon monoxide produced is the same as the amount of carbon dioxide that moves to the anode flow channel 112, that the CF of the other products (hydrogen and oxygen) is 1.0, that carbon dioxide is the only gas species with a different CF, and that all products are gases. Therefore, thermal mass flow meters are used for the flow meters 151 and 152, and the flow rates C and D are measured using the thermal mass flow meters, and the Faraday efficiency of the carbon compound can be estimated using the measurement data for flow rate C and flow rate D.

[0094] When the carbon compound is carbon monoxide, a nitrogen-based thermal mass flow meter is used, and the flow rate CA of carbon dioxide contained in the cathode discharge fluid is calculated by the following formula: CA = (total current (A) × 60 (s) / 96500 (c / mol) / 2 × 22400 (cc / mol) × FE CO +a)×0.74

[0095] When a nitrogen-based thermal mass flow meter is used, the flow rate CB of carbon dioxide moving from the cathode flow channel 122 to the anode flow channel 112 is calculated by the following formula. CB = (total current value (A) × 60 (s) / 96500 (c / mol) / 2 × 22400 (cc / mol) × FE CO +a)×0.74

[0096] At this time, FE CO is as follows, FE CO can be estimated according to a relational expression that approximates a quadratic function involving x. FE CO =16.857x 2 -113.03x+225.17

[0097] In this way, the faradaic efficiency of the carbon compound can be estimated even when using a thermal mass flow meter. The theoretical amount of carbon dioxide required for the reduction reaction can be calculated by multiplying I by 13.93. When the faradaic efficiency decreases, the control device 501 controls the cathode flow regulator 302 to increase the amount of carbon dioxide in accordance with the amount of carbon compound. This allows the faradaic efficiency of the carbon compound to be maintained. Therefore, a decrease in electrolysis efficiency can be suppressed.

[0098] FE CO When is 1.0 (100%), the x obtained by calculating the flow rate measured by the thermal mass flow meter with CF is 1.40, and FE CO As x decreases, x increases as shown in Figure 8. Therefore, when operating under the condition that a constant multiple of x-1.40 is added to the theoretical amount of carbon dioxide, FE CO It is preferable to maintain the FE. Adding 1 times x-1.40 will produce an effect, and adding less than that will produce almost no effect. On the other hand, adding more than 7 times (x-1.40) is not preferable because the cathode discharge fluid will be too diluted, which may require a carbon dioxide separation step for use in the reaction in the downstream device 601 or may reduce the reaction efficiency of the downstream device 601. For this reason, the control device 501 CO It is preferable to control the flow rate A so as to satisfy I×13.93+(x−1.40)×1≦A≦I×13.93+(x−1.40)×7 by controlling the cathode flow rate regulator 302 in accordance with the estimated value of I×13.93+(x−1.40)×1≦A≦I×13.93+(x−1.40)×7.

[0099] Next, the FE when the carbon compound is methane CH4 When the carbon compound is methane, CO2 + 8H + +8e - → A reaction occurs based on the reaction formula expressed by CH4 + 2H2O. Eight electrons are required for one molecule of carbon dioxide, and one molecule of methane is generated, and four molecules of carbon dioxide move from the cathode flow channel 122 to the anode flow channel 112. The CF of methane is 0.74. At this time, the FE CH4 is as follows, FE CH4can be estimated according to a relational expression that approximates a quadratic function involving x. FE CH4 =46.722x 2 -220.93x+296.9

[0100] FE CH4 When is 1.0 (100%), x is 1.19, and FE CH4 As x decreases, as shown in Figure 9, if the constant multiple of (x-1.19) is added to the theoretical amount of carbon dioxide, FE CH4 Therefore, the control device 501 is CH4 It is preferable to control the flow rate A so as to satisfy the equation I×13.93+(x−1.19)×1≦A≦I×13.93+(x−1.19)×12 by controlling the cathode flow rate regulator 302 in accordance with the estimated value of I×13.93+(x−1.19)×1.

[0101] In the case of methane, which has an eight-electron reaction, the change in the Faraday efficiency and the rate of increase of x are different from those of carbon monoxide. Therefore, adding more than 12 times (x-0.83) is not desirable because the cathode discharge fluid becomes too diluted. For example, methane is easily liquefied and can be easily separated by liquefaction using methods such as cryogenics. A multiplication factor exceeding this is undesirable because it dilutes the cathode discharge fluid, necessitating a carbon dioxide separation process for use in the reaction in downstream device 601, or because it reduces the reaction efficiency of downstream device 601.

[0102] Next, FE when the carbon compound is ethylene C2H4 In the case of ethylene, a six-electron reaction, if the carbon compound is ethylene, then 2CO2 + 12H + +12e - → A reaction occurs based on the reaction formula expressed by C2H4 + 4H2O. Six electrons are required for one molecule of carbon dioxide, and one molecule of ethylene is generated, and three molecules of carbon dioxide move from the cathode flow channel 122 to the anode flow channel 112. The CF of ethylene is 0.64. At this time, FE C2H4 is as follows, FE C2H4can be estimated according to a relational expression that approximates a quadratic function involving x. FE C2H4 =27.031x 2 -167.8x+296.12

[0103] FE C2H4 When is 1.0 (100%), x is 1.56, and FE C2H4 As the amount of carbon dioxide decreases, x increases as shown in FIG. 10. Therefore, it is preferable to operate the device under the condition that a constant multiple of (x-1.56) is added to the amount of carbon dioxide, which is the theoretical amount, in order to maintain the Faraday efficiency. C2H4 It is preferable to control the flow rate A so as to satisfy the equation I×13.93+(x−1.56)×1≦A≦I×13.93+(x−1.56)×8 by controlling the cathode flow rate regulator 302 in accordance with the estimated value of I×13.93+(x−1.56)×8.

[0104] In the case of ethylene, which is a six-electron reaction, the change in the Faraday efficiency and the rate of increase of x are different from those of carbon monoxide, so adding more than eight times (x-1.56) is not recommended because the cathode exhaust fluid will become too diluted. Because it is easier to separate ethylene and carbon dioxide than carbon monoxide and carbon dioxide, it is preferable to add up to eight times, rather than seven times.

[0105] Next, the Faraday efficiency FE when the carbon compound is ethane C2H6 If the carbon compound is ethane, then 2CO2 + 16H + +16e - → A reaction occurs based on the reaction formula expressed by C2H6 + 4H2O. Eight electrons are required for one molecule of carbon dioxide, and one molecule of ethane is produced, and four molecules of carbon dioxide move from the cathode flow channel 122 to the anode flow channel 112. The CF of ethane is 0.51. At this time, the FE C2H6 is as follows, FE C2H6 can be estimated according to a relational expression that approximates a quadratic function involving x. FE C2H6 =49.875x 2 -227.47x+295.07

[0106] FE C2H6 When is 1.0 (100%), x is 1.15, and FE C2H6 As x decreases, as shown in Figure 11, if the constant multiple of (x-1.15) is added to the theoretical amount of carbon dioxide, FE C2H6 It is preferable to control it in the range of I×13.93+(x−1.15)×1 to I×13.93+(x−1.15)×8.

[0107] In the case of ethane, which is an eight-electron reaction, the change in the Faraday efficiency and the rate of increase in x are different from those of carbon monoxide, so adding more than eight times (x-1.15) is not recommended because the cathode exhaust fluid will become too diluted. Since it is easier to separate ethane and carbon dioxide than carbon monoxide and carbon dioxide, it is preferable to add up to eight times, rather than seven times.

[0108] As described above, the Faraday efficiency can be estimated using the measurement data for flow rate C and flow rate D. Therefore, if the side reaction is mainly hydrogen and the total Faraday efficiency, including the hydrogen from the main reaction and the hydrogen from the side reaction, is 0.8 (80%) or less, it can be determined that there is an abnormality in the electrolysis reaction or in the electrolysis device 1. Possible causes of a drop to 80% or less include the generation of unexpected hydrogen and substances other than the main product as side reactions, electrical corrosion (galvanic corrosion) of the anode 111 or cathode 121, and crossover of substances between the anode flow path 112 and the cathode flow path 122. Crossover occurs, for example, when the generated hydrogen gas moves back to the anode flow path 112, where the transferred hydrogen is oxidized at the anode 111 and converted back into water. The current consumed by this reaction reduces the total Faraday efficiency.

[0109] When the carbon compound is carbon monoxide, the amount (flow rate) of carbon monoxide produced can be calculated using the following formula. Amount of carbon monoxide produced = total current (A) x 60 (s) / 96,500 (c / mol) / 2 (number of reaction electrons) x 22,400 (cc / mol) x FE CO

[0110] The amount of hydrogen produced (flow rate) can be calculated using the following formula: Amount of hydrogen produced = Total current (A) × 60 (s) / 96500 (cc / mol) / 2 (number of reaction electrons) × 22400 (cc / mol) × (1-FE CO )

[0111] Flow rate C = Flow rate A - Flow rate of carbon dioxide converted to carbon monoxide + Flow rate of generated carbon monoxide - Flow rate of carbon dioxide transferred to the anode flow channel 112 + Flow rate of generated hydrogen The flow rate C can be calculated using the formula:

[0112] The flow rate of the generated carbon monoxide is equal to the flow rate of the carbon dioxide that has moved to the anode flow channel 112. The flow rate of the carbon dioxide that has been converted into carbon monoxide is equal to the flow rate of the generated carbon monoxide. From these relationships, Flow rate C = Flow rate A - Flow rate of carbon dioxide transferred to the anode flow channel 112 + Flow rate of hydrogen produced The flow rate C can be calculated using the formula:

[0113] On the other hand, the flow rate D can be calculated by adding the flow rate of the carbon dioxide that has moved to the anode flow channel 112 to the flow rate of the generated oxygen. The flow rate of the generated oxygen is half the flow rate of the generated carbon monoxide.

[0114] Since the flow rate of the generated carbon monoxide is equal to the flow rate of the carbon dioxide that moved to the anode flow channel 112 and the flow rate of the generated oxygen is half the flow rate of the generated carbon monoxide, the flow rate D can be calculated by adding half the flow rate of the generated hydrogen, that is, the flow rate of oxygen for hydrogen generation, to the flow rate calculated by multiplying the flow rate of the carbon dioxide that moved to the anode flow channel 112 by 1.5. Furthermore, the difference between the cathode supply fluid and the cathode discharge fluid (cathode flow rate increase) can be calculated by subtracting the flow rate of the carbon dioxide that moved to the anode flow channel 112.

[0115] However, the total faradaic efficiency FE of the reduction products produced by the electrolytic cell TOTALWhen the carbon dioxide concentration is 80%, the flow rate CB of carbon dioxide transferred to the anode flow channel 112 can be calculated by the following formula. CB = total current (A) × 60 (s) / 96,500 (c / mol) / 2 (number of reaction electrons) × 22,400 (cc / mol) × FE TOTAL ×0.8

[0116] The flow rate of the generated hydrogen, HA, can be calculated using the following formula: RP is the faradaic efficiency of the carbon compound. HA = total current (A) × 60 (s) / 96500 (c / mol) / 2 (number of reaction electrons) × 22400 (cc / mol) × (1-FE RP )×0.8

[0117] Since the flow rate of the generated carbon monoxide is equal to the flow rate of the carbon dioxide that has moved to the anode flow channel 112, the flow rate C can be calculated by the following formula. Flow rate C = Flow rate A - Flow rate of carbon dioxide converted to carbon monoxide + Flow rate of generated carbon monoxide - Flow rate of carbon dioxide transferred to the anode flow channel 112 + Amount of generated hydrogen

[0118] The increase in flow rate of the cathode discharge fluid relative to the cathode supply fluid (cathode flow rate increase Cinout) can be calculated by subtracting the flow rate of the carbon dioxide that has moved to the anode flow channel 112 from the flow rate of the produced hydrogen.

[0119] Furthermore, 60 (s) / 96500 (c / mol) / 2 (number of reaction electrons) × 22400 (cc / mol) = 6.9637 (cc / min × c) Therefore, Cinout can be calculated by the following formula: Cinout = (total current value I (A) × 6.9637 (cc / min × c) × FE H2 )-(Total current value I(A)×6.9637(cc / min×c)×FE CO )=I(A)×6.9637(cc / min×c)×(FE H2 -FE CO )

[0120] On the other hand, the flow rate D can be calculated using the following formula. D = (Total current value I (A) × 6.9637 (cc / min × c) × (1 / 2) × (FE H2 +FE CO )) + (Total current value I (A) × 6.9637 (cc / min × c) × FE CO ) = Total current value I (A) × 6.9637 (cc / min × c) × (1 / 2) × (FE H2 +(3 / 2×FE CO )))

[0121] From the above relationship, the F E (Faraday efficiency) is the sum of the Faraday efficiency of hydrogen and the Faraday efficiency of carbon monoxide. TOTAL can be calculated using the following formula: FE TOTAL =FE H2 +FE CO =(((Cinout+A×2) / 2×I(A)×6.9637(cc / min×c)

[0122] In this way, the control device 501 uses the measurement data of the flow rate C and the measurement data of the flow rate D to calculate the FE TOTAL Therefore, for example, FE TOTAL If the value is 0.8 (80%) or less, it is determined that an abnormal reaction has occurred, and, for example, the control device 501 can take action to stop the operation of the electrolytic cell.

[0123] For example, the control device 501 (Cathode flow rate increase + D) / Total reaction current value in the electrolytic cell / 60 (s) / 96500 (c / mol) / 2 (number of reaction electrons) × 22400 (cc / mol) / 1.5 It is preferable to stop the operation of the electrolytic cell when the value calculated by FE is 0.8 or less. TOTAL is equivalent to

[0124] Next, consider the case of using a normal mass flow controller that can measure nitrogen, air, etc. Since the CF of the mass flow controller for hydrogen is 1.0 and the CF of carbon dioxide is 0.74, the Faraday efficiency can be estimated by taking only these factors into consideration.

[0125] When considering the inlet of an electrolytic cell or electrolysis device (system) in terms of volumetric flow rate, calculations can be made taking into account that the CF of the carbon dioxide at the outlet of the electrolytic cell or electrolysis device (system) is 0.74. When considering the inlet flow rate of a nitrogen or air-based thermal mass flow controller with a CF of 1.0, it is possible to consider the volumetric flow rate taking into account that the CF of the carbon dioxide at the outlet is 0.74, since it is a single-component gas. However, since the outlet gas is a mixture of gas components with different CFs, it must be considered for each component.

[0126] The flow rate C can be calculated using the following formula: Flow rate C = Flow rate A - Flow rate of carbon dioxide converted to carbon monoxide + Flow rate of generated carbon monoxide - Flow rate of carbon dioxide transferred to the anode flow channel 112 + Flow rate of generated hydrogen

[0127] Cinout can be calculated using the following formula: Cinout = flow rate of produced hydrogen - flow rate of carbon dioxide transferred to the anode flow channel 112

[0128] Here, the measurement value of the thermal mass flow controller must take into account the CF in terms of the reduced carbon dioxide gas flow rate. Therefore, Cinout can be calculated by the following formula. Cinout=(I(A)×6.9637(cc / min×c)×FE H2 )-(CF×I(A)×6.9637(cc / min×c)×FE CO )=I(A)×6.9637(cc / min×c)×(FE H2 -(CF×FE CO ))

[0129] Meanwhile, calculate the flow rate D. The CF of oxygen is 1.0.

[0130] The flow rate of the generated oxygen can be calculated using the following formula: Generated oxygen flow rate = I (A) x 6.9637 (cc / min x c) x (1 / 2) x (FE H2 +FE CO) )

[0131] The flow rate of carbon dioxide transferred from the cathode flow channel 122 can be calculated by the following formula. Flow rate of carbon dioxide transferred from cathode flow channel 122=I(A)×6.9637(cc / min×c)×FE CO

[0132] Furthermore, the flow rate of carbon dioxide transferred from the cathode flow channel 122 measured by the thermal mass flow controller can be calculated by the following formula. Flow rate of carbon dioxide transferred from cathode flow channel 122=I(A)×6.9637(cc / min×c)×CF×FE CO

[0133] From these relationships, the flow rate D can be calculated using the following formula: D = (Total current value I (A) × 6.9637 (cc / min × c) × (1 / 2) × (FE H2 +FE CO) )) + (Total current value I (A) × 6.9637 (cc / min × c) × CF × FE CO )=(I(A)×6.9637(cc / min×c)×((1 / 2)×FE H2 +((1 / 2)+CF)×FE CO )

[0134] (Measurement value of flow rate C measured by thermal mass flow meter × 2) - (Volumetric flow rate of cathode supply fluid minus measurement value of flow rate C measured by thermal mass flow meter) can be calculated using the following formula. I(A)×6.9637(cc / min×c)×(1+3×CF)×FE CO

[0135] On the other hand, the value obtained by subtracting the measured value of the thermal mass flow meter for flow rate C from the measured value of the thermal mass flow meter for flow rate D - the volumetric flow rate of the cathode supply fluid (flow path A) × (0.5 + CF) can be calculated using the following formula. I(A)×6.9637(cc / min×c)×(2 / 3+CF)×FE H2 )

[0136] From these relationships, the following relational expression holds: FE TOTAL =FE CO +FE H2 (Measurement value of thermal mass flow meter for flow rate D × 2 – volumetric flow rate of cathode supply fluid minus measurement value of thermal mass flow meter for flow rate C) / I(A) × 6.9637(cc / min × c) × (2 / 3 + CF) + measurement value of thermal mass flow meter for flow rate D – volumetric flow rate of cathode supply fluid minus measurement value of thermal mass flow meter for flow rate C / I(A) × 6.9637(cc / min × c) × (1.5 + CF)

[0137] If the CF of carbon dioxide is 0.74, then the FE TOTAL can be calculated using the following formula: FE TOTAL = (measured value of flow rate D measured by the thermal mass flow meter × 6.22) - (volumetric flow rate of cathode supply fluid minus measured value of flow rate C measured by the thermal mass flow meter × 0.0824 / total reaction current value in electrolytic cell / 60 (s) / 96,500 (c / mol) / 2 (number of reaction electrons) × 22,400 (cc / mol) × 3.898)

[0138] As described above, the control device 501 uses the measurement data of the flow rate C and the measurement data of the flow rate D to calculate the FE TOTAL can be estimated, for example, FE TOTAL If the estimated value is 0.8 or less, it is determined that an abnormal reaction has occurred, and the control device 501 can take action such as stopping the operation of the electrolytic cell.

[0139] When the carbon compound is methane, the flow rate of the produced methane can be calculated by the following formula based on the relationship: flow rate of produced methane×4=flow rate of carbon dioxide transferred to the anode flow channel 112. Flow rate of methane produced = total current I (A) × 60 (s) / 96,500 (c / mol) / 8 (number of reaction electrons) × 22,400 (cc / mol) × FE CH4

[0140] When the carbon compound is ethylene, the flow rate of the produced ethylene×3=the flow rate of the carbon dioxide that has moved to the anode flow channel 112, so the flow rate of the produced ethylene can be calculated by the following formula. Flow rate of ethylene produced = Total current I (A) × 60 (s) / 96,500 (cc / mol) / 6 (number of reaction electrons) × 22,400 (cc / mol) × FE C2H4

[0141] When the carbon compound is ethane, the flow rate of the produced ethane can be calculated by the following formula based on the relationship: flow rate of produced ethane×4=flow rate of carbon dioxide transferred to the anode flow channel 112. Flow rate of ethane produced = I (A) × 60 (s) / 96500 (c / mol) / 8 (number of reaction electrons) × 22400 (cc / mol) × FE C2H6

[0142] Furthermore, if the number of reaction electrons is N, the flow rate of the produced carbon compounds can be calculated using the following formula: Carbon compound flow rate = total current I (A) × 60 (s) / 96500 (c / mol) / N (number of reaction electrons) × FE RP

[0143] In a two-electron reaction, the flow rate of hydrogen produced can be calculated using the following formula: Flow rate of hydrogen produced = Total current value I (A) × 6.9637 (cc / min × c) × (1-FE H2 )

[0144] In the case of methane, the flow rate C can be calculated using the following formula: Flow rate C = Flow rate A - Flow rate of carbon dioxide converted to methane + Flow rate of methane produced - Flow rate of carbon dioxide transferred to the anode flow channel 112 + Flow rate of hydrogen produced

[0145] Furthermore, the flow rate of the produced methane×4=the amount of carbon dioxide that has moved to the anode flow channel 112, and the flow rate of the carbon dioxide that has been converted into methane=the flow rate of the produced methane.

[0146] Furthermore, the flow rate of the produced ethylene×3=the flow rate of the carbon dioxide that has moved to the anode flow channel 112, and the flow rate of the carbon dioxide that has been converted into ethylene=the flow rate of the produced ethylene.

[0147] In the case of ethylene, the flow rate C can be calculated using the following formula: It can be calculated by C=A-flow rate of carbon dioxide converted into ethylene+flow rate of ethylene produced-flow rate of carbon dioxide transferred to the anode flow channel 112+flow rate of hydrogen produced.

[0148] Furthermore, the flow rate of the produced ethane×4=the flow rate of the carbon dioxide that has moved to the anode flow channel 112, and the flow rate of the carbon dioxide that has been converted into ethane=the flow rate of the produced ethane.

[0149] The flow rate C can be calculated using the following formula: C = A - flow rate of carbon dioxide converted to methane + flow rate of methane produced - flow rate of carbon dioxide transferred to the anode flow channel 112 + flow rate of hydrogen produced

[0150] On the other hand, in the case of methane, the flow rate D can be calculated as the sum of the flow rate of carbon dioxide that has moved to the anode flow channel 112 and the flow rate of the oxygen that has been generated. Here, the flow rate of the generated methane × 4 = the flow rate of carbon dioxide that has moved to the anode flow channel 112, and because the reaction of the generated methane produces twice the amount of oxygen, the flow rate D can be calculated as the amount of carbon dioxide that has moved to the anode flow channel 112 × 1.5. Therefore, the following relational expression holds true. Flow rate D = total current value I (A) × 13.9278 (cc / min × c) / 2 (number of reaction electrons) × ((1 / 2)FEH2 +((1 / 2)(number of reaction electrons)FE CH4 ) + (8 (number of reaction electrons) / 2 × FE CH4 )

[0151] In the case of ethylene, the flow rate of the produced ethylene × 3 = the flow rate of the carbon dioxide that moved to the anode flow channel 112, and because the reaction of the produced ethylene produces three times the amount of oxygen, the flow rate A can be calculated by multiplying the amount of carbon dioxide that moved to the anode flow channel 112 by 2. Therefore, the following formula is established.

[0152] Flow rate D = total current value I (A) × 13.9278 (cc / min × c) / 2 (number of reaction electrons) × ((1 / 2)FE H2 +(1 / 2)FE C2H4 +6 (number of reaction electrons) / 2 x FE C2H4 )

[0153] In the case of ethane, the flow rate of the produced ethane × 4 = the flow rate of the carbon dioxide that moved to the anode flow channel 112. Because the reaction of the produced ethane produces twice the amount of oxygen, the flow rate D is the amount of carbon dioxide that moved to the anode flow channel 112 × 1.5, and the following formula holds true. Flow rate D = total current value I (A) × 13.9278 (cc / min × c) / 2 (number of reaction electrons) × ((1 / 2)FE H2 +(1 / 2)FE C2H6 +8 (number of reaction electrons) / 2 x FE C2H6 )

[0154] When the number of reactive electrons of the carbon compound (RP) of carbon dioxide is N (N is a natural number), the flow rate D can be calculated using the following formula. Flow rate D = total current value I (A) × 13.9278 (cc / min × c) / 2 (number of reaction electrons) × ((1 / 2)FE H2 +(1 / 2)FE RP +N (number of reaction electrons) / 2×FE RP )

[0155] Cinout can be calculated by subtracting the flow rate of the produced hydrogen from the flow rate of the carbon dioxide that has moved to the anode flow channel 112. TOTALWhen the Faraday efficiency (here, the sum of the Faraday efficiency of hydrogen and the Faraday efficiency of the carbon compound) is 0.8, the flow rate of carbon dioxide that has moved to the anode flow channel 112 can be calculated by the following formula. Flow rate of carbon dioxide transferred to the anode flow channel 112=I(A)×60(s) / 96500(c / mol) / N(number of reaction electrons)×22400(cc / mol)×FE RP ×0.8

[0156] The amount of hydrogen produced can be calculated using the following formula: Amount of hydrogen produced = Total current value I (A) × 60 (s) / 96500 (c / mol) / N (number of reaction electrons) × 22400 (cc / mol) × (1-FE RP )×0.8

[0157] Since the flow rate of the produced carbon compounds is equal to the flow rate of carbon dioxide that has moved to the anode flow channel 112, the flow rate C can be calculated by the following formula. C=A−flow rate of carbon dioxide converted into carbon compounds+flow rate of generated carbon compounds−flow rate of carbon dioxide transferred to the anode flow channel 112+flow rate of generated hydrogen

[0158] Cinout can be calculated using the following formula: Cinout = Total current (A) x 13.9275 / 2 x FE H2 -I(A)×13.9275 / N(number of reaction electrons)×FE RP

[0159] In the case of carbon compounds, the flow rate D can be calculated using the following formula: D = total current value (A) × 13.9275 / 2 × ((1 / 2)FE H2 + (1 / 2)FE (Faraday efficiency of carbon compound) + N (number of reaction electrons) / 2 × FE RP

[0160] In the case of a thermal mass flow controller, Cinout can be calculated using the following formula: Cinout=(I(A)×13.9275 / 2×FE H2)-(I(A)×13.9275 / N(number of reaction electrons)×FE RP ×CF)

[0161] In the case of a thermal mass flow controller, the flow rate D can be calculated using the following formula: D=I(A)×13.9275 / 2×((1 / 2)FE H2 +(1 / 2)FE RP +N (number of reaction electrons) / 2×FE RP ×CF

[0162] For a thermal mass flow controller, the following equation holds: D-(1 / 2)×Cinout=Total current value (A)×13.9275 / 2×((1 / 2)×FE RP +N (number of reaction electrons) / 2×FE RP ×CF+(1 / 2)×N(number of reaction electrons)FE RP ×CF=Total current value (A)×13.9275×1 / 4×FE RP × (1-N(number of reactive electrons) × CF + 1 / N(number of reactive electrons) × CF

[0163] From this relationship, FE RP can be calculated using the following formula: FE RP = 4 × (D-(1 / 2) × Cinout) / total current value (A) × 13.9275 × (1-N (number of reaction electrons) × CF + 1 / N (number of reaction electrons) × CF) = 4 × (D-(1 / 2) × Cinout) / total current value (A) × 13.9275 × α α = (1-N(number of reactive electrons) × CF + 1 / N(number of reactive electrons) × CF)

[0164] In the case of methane, which is an 8-electron reaction, α = 9.125. In the case of a thermal mass flow controller, CF = 0.74, so α MFC =7.0125. In the case of ethylene, a six-electron reaction, α MFC = 7.1666. In the case of a thermal mass flow controller, CF = 0.64, so α MFC = 4.9466. In the case of ethane, which is an eight-electron reaction, α MFC= 9.125. In the case of a mass flow controller, CF = 0.51, so α MFC =5.14375.

[0165] In addition, in the case of a thermal mass flow controller, FE H2 can be calculated using the following formula: FE H2 = Cinout × 2 / total current value (A) × 13.9275 + CF / N (number of reaction electrons) × FE RP

[0166] From this relationship, FE H2 and FE CO FE consisting of the sum of TOTAL can be calculated using the following formula: FE TOTAL =FE H2 +FE CO = Cinout × 2 / total current value (A) × 13.9275 + CF / N (number of reaction electrons) × FE RP +4×(D-(1 / 2)×Cinout) / Total current value (A)×13.9275×α

[0167] As described above, the control device 501 uses the measurement data of the flow rate C and the measurement data of the flow rate D to calculate the FE TOTAL Therefore, for example, FE TOTAL If the value is 0.8 (80%) or less, it is determined that an abnormal reaction has occurred in the electrolysis device 1, and the control device 501 can take action such as stopping the operation of the electrolysis cell.

[0168] Furthermore, as shown in Fig. 3, by providing energy converters 701 and 702, the kinetic energy of the anode discharge fluid and the kinetic energy of the cathode discharge fluid can be used to drive anode flow rate regulator 202 to supply anode supply fluid, and to drive cathode flow rate regulator 302 to supply cathode supply fluid. This reduces the energy consumption of the entire electrolysis device and improves efficiency. Specifically, gears or the like can be provided as energy converters 701 and 702 to obtain kinetic energy.

[0169] At this time, the kinetic energy may be converted into electrical energy once, and then the electrical energy may be converted back into kinetic energy to drive the anode flow rate regulator 202 and the cathode flow rate regulator 302 .

[0170] Furthermore, not all of the kinetic energy can be used to drive the anode flow regulator 202 or the cathode flow regulator 302; it is reduced by the change efficiency. This value reduces the kinetic energy used for drive by a certain percentage. When kinetic energy is used to supply the anode supply fluid, a sufficient flow rate of the anode supply fluid can be supplied for the reaction, so a change in the ratio has very little impact and is not a problem. A decrease in the flow rate of the anode supply fluid, even if it is stoichiometrically excessive, can cause a performance degradation problem due to a decrease in the contact area of ​​the catalyst surface caused by the generated oxygen gas. However, this can be solved by taking measures such as increasing the specific surface area of ​​the catalyst. For example, titanium nonwoven fabric or titanium granules stacked and solidified by sintering or other methods can be used.

[0171] On the other hand, changes in the amount of gas used for the cathode supply fluid have a significant impact on performance. If the Faraday efficiency drops, increasing flow rate A can stabilize it. Table 1 shows examples of calculation results for flow rate A and flow rate C + flow rate D, assuming that the cathode supply fluid is supplied with a flow rate A that can be calculated by multiplying the total flow rate of flow rates C and D by 0.7.

[0172] [Table 1]

[0173] As shown in Table 1, when the Faraday efficiency decreases, reducing flow rate A to match the sum of flow rates C and D reduces the carbon dioxide flow rate in the cathode discharge fluid. This reduces the carbon dioxide flow rate as a carbon monoxide and hydrogen gas component, which is desirable for the hydrocarbon generator used in the downstream device 601. However, reducing flow rate A creates harsh reaction conditions, causing the reaction to proceed in a direction that further reduces the Faraday efficiency. Therefore, by increasing flow rate A when the Faraday efficiency decreases, the reaction conditions can be controlled to be milder, thereby maintaining the Faraday efficiency. This suppresses the decrease in electrolysis efficiency. Note that the use of 70% of the kinetic energy of the anode discharge fluid and cathode discharge fluid to supply the cathode supply fluid is the result of considering the decrease in efficiency.

[0174] In this way, the flow rate A can be controlled without measuring the Faraday efficiency using an analytical instrument such as a gas chromatograph. Furthermore, the control device 501 can estimate the Faraday efficiency using the measurement data of the flow rate C and the measurement data of the flow rate D. This is preferable because it eliminates the need for an instrument to measure the Faraday efficiency and also eliminates the need to provide a separate instrument to control the flow rate A.

[0175] The control device 501, for example, I×6.964×(100-14.778x 2 -99.006x+205.41) It is preferable to calculate the flow rate of hydrogen generated by the electrolysis device 1 from the value calculated by the above formula, control the hydrogen supply source 602, and reduce the flow rate of the hydrogen-containing fluid supplied from the hydrogen supply source 602 to the downstream device 601 in accordance with the calculated flow rate of hydrogen. H2 For example, the FE at the start of operation initially assumed for the hydrogen supply source 602 corresponds to the estimated value of TOTAL The flow rate of the hydrogen-containing fluid supplied to the downstream device 601 is reduced by the amount of flow rate reduced from 100%. In other words, I (total current value) × 6.964 × 100 − FE RP Since the flow rate of hydrogen is increased, it is preferable to correct for this increase. [Example]

[0176] (Comparative Example 1, Example 1 (Carbon Monoxide)) An electrolysis device with the structure shown in Figure 1 was assembled and its electrolysis performance was investigated. The electrolysis cell used a cathode in which carbon particles carrying gold nanoparticles were coated on carbon paper with a porous layer. The cathode was fabricated using the following procedure. First, a coating solution was prepared by mixing carbon particles carrying gold nanoparticles with pure water, Nafion solution, and ethylene glycol. The average diameter of the gold nanoparticles was 8.7 nm, and the loading amount was 18.9 mass%. This coating solution was filled into an airbrush and spray-coated onto carbon paper with a porous layer using nitrogen gas. After coating, the paper was washed with running pure water for 30 minutes and then immersed in hydrogen peroxide to oxidize and remove organic substances such as ethylene glycol. This was cut into a 2 cm x 2 cm piece to form the cathode 121. The amount of gold coated was approximately 0.4 mg / cm, based on the amount of gold nanoparticles and carbon particles mixed in the coating solution. 2 It was estimated that the anode 111 was an electrode made of Ti mesh coated with IrO2 nanoparticles as an anode catalyst. The IrO2 / Ti mesh electrode was cut into a 10cm x 10cm size and used as the anode 111.

[0177] The catalyst area of ​​the electrolysis cell is 100 cm 2 The depth of the anode flow channel 112 and the cathode flow channel 122 was set to 1.0 mm.

[0178] The flow rate of carbon dioxide supplied as the cathode feed fluid was kept constant at 11.5 ccm per unit cell. The electrolysis cell was operated with a slightly higher amount of carbon dioxide supplied than the theoretical amount. The anode feed fluid was a 0.1 M KHCO3 aqueous solution at a flow rate of 0.4 ccm.

[0179] The structure was fabricated by stacking a clamping plate, an insulating plate, a current collector, a cell, a current collector, an insulating plate, and a clamping plate in that order. Current density: 200 mA / cm 2 , cell area 4cm 2A total current of 0.8 A was passed through the cell. Heat was generated during operation, but because the cell's heat capacity and heat dissipation were large, operation was carried out at approximately room temperature.

[0180] All data during the reaction, such as voltage and flow rate, was acquired by the control unit 500. The flow rate of the cathode discharge fluid from the cathode discharge flow path was designated as flow rate C, and the flow rate of the anode discharge fluid from the anode discharge flow path was designated as flow rate D. Flow rates C and D were measured using a volumetric flow rate and a nitrogen-based thermal mass flow meter. For confirmation, the flow rates of carbon monoxide and hydrogen produced by the carbon dioxide reduction reaction and the water reduction reaction were analyzed by gas chromatography (GC). For confirmation, the partial current density of carbon monoxide and the partial current density of hydrogen, as well as the Faraday efficiency, which is the ratio of the total current density to the partial current density, were calculated from the amounts of products analyzed by the control unit 501.

[0181] Table 2 shows the cell voltage and carbon monoxide Faraday efficiency (FE(GC)) initially and 50 hours after the start of operation. Table 2 also shows the value of x(D / (Ca)) measured by the volumetric flow meter and the x(MFC) calculated from the flow rates C and D measured by the thermal mass flow meter. Table 2 also shows the Faraday efficiencies of carbon compounds (estimated FE, estimated FE(MFC)) estimated from this x value using the following formula. Other conditions and results are also shown in Table 2. For volumetric flow rate, FE=14.778x 2 -99.006x+205.1 FE=16.857x for thermal mass flow meters 2 -113.03x+225.17

[0182] (Example 1 (x1, x5, x10, x12)) The flow rate was controlled to be 1, 5, 10, and 12 times the theoretical flow rate (x-1.33) at all times, and the operation was continued for 50 hours. The conditions and results for this operation are shown in Table 2.

[0183] (Comparative Example 1 (x 0.5, x 15)) The theoretical flow rate was constantly controlled by adding 0.5 and 15 times (x-1.33) to the flow rate, and the operation was continued for 50 hours. The conditions and results for this operation are shown in Table 2.

[0184] [Table 2]

[0185] From Table 2, it can be seen that Example 1 (x1, x5, x10, x12) had a lower cell voltage and higher Faraday efficiency after 50 hours of operation compared to Comparative Example 1 (x0.5). This can be attributed to the increase in flow rate A as the estimated value of Faraday efficiency decreased. On the other hand, in Comparative Example 1 (x15), although the cell voltage decreased, the Faraday efficiency also decreased.

[0186] (Comparative Example 2, Example 2 (Ethylene)) The cathode catalyst was changed to a Cu alloy nanocatalyst specialized for ethylene production, and the reaction was carried out. The flow rate A was initially set to 11.5 ccm, and x was calculated from flow rates C and D. The Faraday efficiencies were estimated from the value of x according to the above formula for ethylene. The rest of the experiment was the same as in Comparative Example 1 and Example 1. The conditions and results are shown in Table 3.

[0187] (Comparative Example 2 (x 0.5, x 15) The theoretical flow rate was constantly controlled by adding 0.5 and 15 times (x-0.89) to the flow rate, and the operation was continued for 50 hours. The conditions and results for this operation are shown in Table 3.

[0188] (Example 2 (x1, x5, x10, x12)) The flow rate was controlled to be 1, 5, 10, or 12 times the theoretical flow rate (x-0.89), and the operation was continued for 50 hours. The conditions and results are shown in Table 3.

[0189] [Table 3]

[0190] From Table 3, it can be seen that in Comparative Example 2 (x0.5), the flow rate A was reduced compared to Comparative Example 2 (ethylene), but the faradaic efficiency and cell voltage were the same as those of Comparative Example 2 (ethylene). This means that, although the conditions are more severe for the reaction, adjusting the flow rate A according to the estimated faradaic efficiency resulted in more stable operation. However, the performance was similar to that of Comparative Example 2 (ethylene), and no improvement in the overall cell performance was achieved.

[0191] From Table 3, it can be seen that Example 2 (x1, x5, x10, x12) had a lower cell voltage and higher Faraday efficiency after 50 hours of operation compared to Comparative Example 2 (x0.5). This can be attributed to the increase in flow rate A as the estimated value of Faraday efficiency decreased. On the other hand, in Comparative Example 2 (x15), although the cell voltage decreased, the Faraday efficiency also decreased.

[0192] (Comparative Example 3, Example 3 (Methane)) The cathode catalyst was changed to a Cu alloy nanocatalyst specialized for methane production, and the reaction was carried out. The flow rate A was initially set to 11.5 ccm, and x was calculated from flow rates C and D. The Faraday efficiencies were estimated from the value of x according to the above formula for methane. The rest of the experiment was carried out in the same manner as in Comparative Example 1 and Example 1. The conditions and results are shown in Table 4.

[0193] (Comparative Example 3 (x 0.5, x 15) The theoretical flow rate was constantly controlled by adding 0.5 and 15 times (x-0.83) to the flow rate, and the operation was continued for 50 hours. The conditions and results for this operation are shown in Table 4.

[0194] (Example 3 (x1, x5, x10, x12) The theoretical flow rate was constantly controlled by adding 1, 5, 10, and 12 times (x-0.83), and the operation was continued for 50 hours. The rest of the procedure was the same as in Comparative Example 3. The conditions and results for this case are shown in Table 4.

[0195] [Table 4]

[0196] From Table 4, it can be seen that in Comparative Example 3 (×0.5), the flow rate A was reduced compared to Comparative Example 3 (methane), but the faradaic efficiency and cell voltage were the same as those of Comparative Example 3 (methane). This means that, although the conditions are more severe for the reaction, adjusting the flow rate A according to the estimated faradaic efficiency resulted in more stable operation. However, the performance was similar to that of Comparative Example 3 (methane), and no improvement in the overall performance of the cell was achieved.

[0197] From Table 4, it can be seen that Example 3 (x1, x5, x10, x12) had a lower cell voltage and higher Faraday efficiency after 50 hours of operation compared to Comparative Example 3 (x0.5). This can be attributed to the increase in flow rate A as the estimated value of Faraday efficiency decreased. On the other hand, in Comparative Example 3 (x15), although the cell voltage decreased, the Faraday efficiency also decreased.

[0198] (Comparative Example 4, Example 4 (Ethane)) The cathode catalyst was changed to a Cu alloy nanocatalyst specialized for ethane production, and the reaction was carried out. The flow rate A was initially set to 11.5 ccm, and x was calculated from flow rates C and D. The Faraday efficiency was estimated from the value of x according to the above formula for ethane. The rest of the experiment was carried out in the same manner as in Comparative Example 1 and Example 1. Other conditions and results are shown in Table 5.

[0199] (Comparative Example 4 (x 0.5, x 15) The flow rate A was initially set to 11.5 ccm, and x was calculated from flow rates C and D. 0.5 and 15 times (x-0.83) were added to the theoretical flow rate under constant control, and the operation was continued for 50 hours. The conditions and results for this case are shown in Table 5.

[0200] (Example 4 (x1.0, x5.0, x10, x12)) The flow rate A was initially set to 11.5 ccm, and x was calculated from flow rates C and D. The theoretical flow rate was then adjusted by adding 1, 5, 10, or 12 times (x-0.83) to the flow rate. The operation was continued for 50 hours. The conditions and results are shown in Table 5.

[0201] [Table 5]

[0202] From Table 5, it can be seen that in Comparative Example 4 (×0.5), the flow rate A was reduced compared to Comparative Example 4 (ethane), but the faradaic efficiency and cell voltage were the same as those of Comparative Example 4 (ethane). This means that, although the conditions are more severe for the reaction, adjusting the flow rate A according to the estimated faradaic efficiency resulted in more stable operation. However, the performance was similar to that of Comparative Example 4 (ethane), and no improvement in the overall performance of the cell was achieved.

[0203] From Table 5, it can be seen that Example 4 (x1, x5, x10, x12) had a lower cell voltage and higher Faraday efficiency after 50 hours of operation compared to Comparative Example 4 (x0.5). This can be attributed to the increase in flow rate A as the estimated value of Faraday efficiency decreased. On the other hand, in Comparative Example 4 (x15), although the cell voltage decreased, the Faraday efficiency also decreased.

[0204] Increasing the flow rate A too much, as in the case of 15x, reduces the Faraday efficiency due to factors such as drying of the catalyst surface, drying of the separator, and pressure and temperature distributions within the cell. Humidification may be used to prevent drying of the separator or catalyst layer, or measures such as heating water to the same temperature as the cell temperature to form water vapor may be taken. However, to increase the purity of the generated gas, it is necessary to remove water vapor after the reaction. Furthermore, the large energy required to generate water vapor reduces overall efficiency. In particular, increasing the flow rate increases the energy required to generate water vapor, preheat the reactant gas, and remove water vapor from the heated cathode exhaust fluid, resulting in greater heat energy loss. Furthermore, even if the Faraday efficiency is maintained, the concentration of the generated gas in the cathode exhaust fluid decreases, necessitating subsequent purification steps, which reduces the overall system efficiency. Because of this reduction in efficiency as well as the overall system efficiency, excessively high flow rates are undesirable.

[0205] As described above, by controlling the flow rate A in accordance with the estimated value of the Faraday efficiency, it is possible to suppress a decrease in the electrolysis efficiency.

[0206] The configurations of the above-described embodiments can be applied in combination with each other, and some of them can be replaced with other configurations. Although several embodiments of the present invention have been described herein, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0207] The above embodiments can be summarized in the following technical solutions. (Technical proposal 1) an electrolysis cell having a cathode that reduces carbon dioxide to produce carbon compounds, an anode that oxidizes water to produce oxygen, a cathode flow channel facing the cathode, and an anode flow channel facing the anode; a cathode supply flow path connected to an inlet of the cathode flow path, through which a cathode supply fluid containing the carbon dioxide gas flows and which is supplied to the cathode flow path; an anode supply flow path connected to an inlet of the anode flow path, the anode supply flow path being supplied to the anode flow path and through which the anode supply fluid containing water flows; a cathode discharge flow path connected to an outlet of the cathode flow path, through which a cathode discharge fluid discharged from the cathode flow path and containing the carbon compound and the carbon dioxide flows; an anode discharge flow path connected to an outlet of the anode flow path, through which an anode discharge fluid discharged from the anode flow path and containing the oxygen and the water flows; a cathode flow rate regulator that regulates a flow rate A of the cathode supply fluid supplied to the cathode flow path; an anode flow rate regulator that regulates the flow rate B of the anode supply fluid supplied to the anode flow path; a first flow meter that measures a flow rate C of the cathode discharge fluid discharged from the cathode flow channel; a second flow meter that measures a flow rate D of the anode exhaust fluid discharged from the anode flow channel; a control device that receives measurement data of the flow rate C from the first flow meter and measurement data of the flow rate D from the second flow meter; Equipped with The control device Using the measurement data of the flow rate C and the measurement data of the flow rate D, estimating the value of the Faraday efficiency of the carbon compound according to a relational expression that approximates the value of the Faraday efficiency to a function including the flow rate C and the flow rate D; controlling the cathode flow regulator in accordance with the estimated value of the Faraday efficiency to control the flow rate A; Electrolyzer. (Technical proposal 2) The control device controls the cathode flow rate regulator in accordance with the estimated value of the Faraday efficiency, I×13.93+(x-1.33)×1≦A≦I×13.93+(x-1.33)×10 (I represents the total reaction current value in the electrolytic cell, x satisfies x=D / (Ca), and a represents the flow rate of the carbon dioxide gas contained in the cathode discharge fluid.) The flow rate A is controlled so as to satisfy The electrolysis device described in Technical Proposal 1. (Technical proposal 3) the first flow meter is a first thermal mass flow meter; the second flow meter is a second thermal mass flow meter; The control device controls the cathode flow rate regulator in accordance with the estimated value of the Faraday efficiency, I×13.93+(x-1.40)×1≦A≦I×13.93+(x-1.40)×7 (I represents the total reaction current value, x satisfies x=D / (Ca), and a represents the flow rate of excess carbon dioxide that is not reduced among the carbon dioxide contained in the cathode supply fluid.) The flow rate A is controlled so as to satisfy The electrolysis device described in Technical Proposal 1. (Technical proposal 4) the control device is connected to at least one device selected from the group consisting of a power supply that supplies current or voltage between the anode and the cathode, a cathode pressure regulator that controls the pressure in the cathode flow path, an anode pressure regulator that controls the pressure in the anode flow path, and a temperature regulator that adjusts the temperature of the electrolysis cell; An electrolysis device according to any one of technical solutions 1 to 3. (Technical proposal 5) The control device (Cathode flow rate increase + D) / Total reaction current value in the electrolytic cell / 60 (s) / 96500 (c / mol) / 2 (number of reaction electrons) × 22400 (cc / mol) / 1.5 When the value calculated by is 0.8 or less, the operation of the electrolytic cell is stopped. The electrolysis device described in Technical Proposal 1. (Technical proposal 6) the first flow meter is a first thermal mass flow meter; the second flow meter is a second thermal mass flow meter; The control device When the total faradaic efficiency of the reduction products by the electrolytic cell is 0.8 or less, the operation of the electrolytic cell is stopped. The electrolysis device described in Technical Proposal 1. (Technical proposal 7) the control device is connected to a hydrogen supply source that supplies the hydrogen-containing fluid to a chemical synthesis reaction device that is provided downstream of the electrolysis device and that generates a compound by a chemical reaction using the carbon compound and hydrogen; An electrolysis device according to any one of technical solutions 1 to 6. (Technical proposal 8) the first flow meter is a first thermal mass flow meter; the second flow meter is a second thermal mass flow meter; The control device I×6.964×(100-14.778x 2 -99.006x+205.41) Calculating the flow rate of hydrogen generated by the electrolysis device from the value calculated by reducing the flow rate of the hydrogen-containing fluid supplied to the chemical synthesis reactor in accordance with the calculated flow rate of hydrogen by controlling the hydrogen supply source; Electrolysis device described in Technical Proposal 7. (Technical proposal 9) a first energy converter provided in the anode exhaust flow path and configured to convert a first energy of the anode exhaust fluid flowing through the anode exhaust flow path into a first electrical energy or a first rotational energy; the anode flow regulator is driven using the first electrical energy or the first rotational energy; An electrolysis device according to any one of technical solutions 1 to 8. (Technical proposal 10) a second energy converter provided in the cathode discharge flow path and configured to convert a second energy of the cathode discharge fluid flowing through the cathode discharge flow path into a second electrical energy or a second rotational energy; the cathode flow regulator is driven using the second electrical energy or the second rotational energy; An electrolysis device according to any one of technical solutions 1 to 8. (Technical proposal 11) An electrolysis method using an electrolysis device, The electrolysis device comprises: an electrolysis cell having a cathode that reduces carbon dioxide to produce carbon compounds, an anode that oxidizes water to produce oxygen, a cathode flow channel facing the cathode, and an anode flow channel facing the anode; a cathode supply flow path connected to an inlet of the cathode flow path, through which a cathode supply fluid containing the carbon dioxide gas flows and which is supplied to the cathode flow path; an anode supply flow path connected to an inlet of the anode flow path, the anode supply flow path being supplied to the anode flow path and through which the anode supply fluid containing water flows; a cathode discharge flow path connected to an outlet of the cathode flow path, through which a cathode discharge fluid discharged from the cathode flow path and containing the carbon compound and the carbon dioxide flows; an anode discharge flow path connected to an outlet of the anode flow path, through which an anode discharge fluid discharged from the anode flow path and containing the oxygen and the water flows; a cathode flow rate regulator that regulates a flow rate A of the cathode supply fluid supplied to the cathode flow path; an anode flow rate regulator that regulates the flow rate B of the anode supply fluid supplied to the anode flow path; a first flow meter that measures a flow rate C of the cathode discharge fluid discharged from the cathode flow channel; a second flow meter that measures a flow rate D of the anode exhaust fluid discharged from the anode flow channel; Equipped with The electrolysis method comprises: using measurement data of the flow rate C from the first flow meter and measurement data of the flow rate D from the second flow meter, estimating a value of the Faraday efficiency of the carbon compound according to a relational expression that approximates the value of the Faraday efficiency to a function including the flow rates C and D; controlling the cathode flow regulator in accordance with the estimated value of the Faraday efficiency to control the flow rate A; Electrolysis method. [Explanation of symbols]

[0208] 1...electrolysis device, 100...electrolysis section, 111...anode, 112...anode flow path, 113...anode current collector, 114...flow path plate, 121...cathode, 122...cathode flow path, 123...cathode current collector, 124...flow path plate, 131...separator, 150...power supply, 151...flow meter, 152...flow meter, 153...temperature detector, 200...anode supply section, 201...anode collector, 202...anode flow rate regulator, 203...anode pressure Power regulator, 300...cathode supply unit, 301...supply source, 302...cathode flow regulator, 303...cathode pressure regulator, 400...cathode exhaust unit, 401...cathode collector, 500...control unit, 501...control device, 600...post-stage unit, 601...post-stage device, 602...hydrogen supply source, 701...energy converter, 702...energy converter, A...flow rate, B...flow rate, C...flow rate, CA...flow rate, CB...flow rate, D...flow rate, HA...flow rate.

Claims

1. an electrolysis cell having a cathode that reduces carbon dioxide to produce carbon compounds, an anode that oxidizes water to produce oxygen, a cathode flow channel facing the cathode, and an anode flow channel facing the anode; a cathode supply flow path connected to an inlet of the cathode flow path, through which a cathode supply fluid containing the carbon dioxide gas flows and which is supplied to the cathode flow path; an anode supply flow path connected to an inlet of the anode flow path, the anode supply flow path being supplied to the anode flow path and through which the anode supply fluid containing water flows; a cathode discharge flow path connected to an outlet of the cathode flow path, through which a cathode discharge fluid discharged from the cathode flow path and containing the carbon compound and the carbon dioxide flows; an anode discharge flow path connected to an outlet of the anode flow path, through which an anode discharge fluid discharged from the anode flow path and containing the oxygen and the water flows; a cathode flow rate regulator that regulates a flow rate A of the cathode supply fluid supplied to the cathode flow path; an anode flow rate regulator that regulates the flow rate B of the anode supply fluid that is supplied to the anode flow path; a first flow meter that measures a flow rate C of the cathode discharge fluid discharged from the cathode flow channel; a second flow meter that measures a flow rate D of the anode exhaust fluid discharged from the anode flow channel; a control device that receives measurement data of the flow rate C from the first flow meter and measurement data of the flow rate D from the second flow meter; Equipped with The control device using the measurement data of the flow rate C and the measurement data of the flow rate D, estimating the value of the Faraday efficiency of the carbon compound in accordance with a relational expression that approximates the value of the Faraday efficiency to a function including the flow rate C and the flow rate D; controlling the cathode flow regulator in accordance with the estimated value of the Faraday efficiency to control the flow rate A; Electrolyzer.

2. The control device controls the cathode flow rate regulator in accordance with the estimated value of the Faraday efficiency, I×13.93+(x-1.33)×1≦A≦I×13.93+(x-1.33)×10 (I represents the total reaction current value in the electrolytic cell, x satisfies x=D / (C−a), and a represents the flow rate of the carbon dioxide gas contained in the cathode discharge fluid.) The flow rate A is controlled so as to satisfy 2. The electrolysis device according to claim 1.

3. the first flow meter is a first thermal mass flow meter; the second flow meter is a second thermal mass flow meter; The control device controls the cathode flow rate regulator in accordance with the estimated value of the Faraday efficiency, I×13.93+(x-1.40)×1≦A≦I×13.93+(x-1.40)×7 (I represents the total reaction current value, x satisfies x=D / (C−a), and a represents the flow rate of excess carbon dioxide that is not reduced among the carbon dioxide contained in the cathode supply fluid.) The flow rate A is controlled so as to satisfy 2. The electrolysis device according to claim 1.

4. the control device is connected to at least one device selected from the group consisting of a power supply that supplies current or voltage between the anode and the cathode, a cathode pressure regulator that controls the pressure in the cathode flow path, an anode pressure regulator that controls the pressure in the anode flow path, and a temperature regulator that adjusts the temperature of the electrolysis cell; 2. The electrolysis device according to claim 1.

5. The control device (Cathode flow rate increase + D) / Total reaction current value in the electrolysis cell / 60 (s) / 96500 (c / mol) / 2 (number of reaction electrons)×22400 (cc / mol) / 1.5 When the value calculated by is 0.8 or less, the operation of the electrolytic cell is stopped.

2. The electrolysis device according to claim 1.

6. the first flow meter is a first thermal mass flow meter; the second flow meter is a second thermal mass flow meter; The control device When the total faradaic efficiency of the reduction products by the electrolytic cell is 0.8 or less, the operation of the electrolytic cell is stopped.

2. The electrolysis device according to claim 1.

7. the control device is connected to a hydrogen supply source that supplies the hydrogen-containing fluid to a chemical synthesis reaction device that is provided downstream of the electrolysis device and that generates a compound by a chemical reaction using the carbon compound and hydrogen; 7. The electrolysis device according to claim 1.

8. the first flow meter is a first thermal mass flow meter; the second flow meter is a second thermal mass flow meter; The control device I×6.964×(100-14.778x ２ -99.006x+205.41) Calculating the flow rate of hydrogen generated by the electrolysis device from the value calculated by reducing the flow rate of the hydrogen-containing fluid supplied to the chemical synthesis reactor in accordance with the calculated flow rate of hydrogen by controlling the hydrogen supply source; 8. The electrolysis device according to claim 7.

9. a first energy converter provided in the anode exhaust flow path and configured to convert a first energy of the anode exhaust fluid flowing through the anode exhaust flow path into a first electrical energy or a first rotational energy; the anode flow regulator is driven using the first electrical energy or the first rotational energy; 7. The electrolysis device according to claim 1.

10. a second energy converter provided in the cathode discharge flow path and configured to convert second energy of the cathode discharge fluid flowing through the cathode discharge flow path into second electrical energy or second rotational energy; the cathode flow regulator is driven using the second electrical energy or the second rotational energy; 7. The electrolysis device according to claim 1.

11. An electrolysis method using an electrolysis device, The electrolysis device comprises: an electrolysis cell having a cathode that reduces carbon dioxide to produce carbon compounds, an anode that oxidizes water to produce oxygen, a cathode flow channel facing the cathode, and an anode flow channel facing the anode; a cathode supply flow path connected to an inlet of the cathode flow path, through which a cathode supply fluid containing the carbon dioxide gas flows and which is supplied to the cathode flow path; an anode supply flow path connected to an inlet of the anode flow path, the anode supply flow path being supplied to the anode flow path and through which the anode supply fluid containing water flows; a cathode discharge flow path connected to an outlet of the cathode flow path, through which a cathode discharge fluid discharged from the cathode flow path and containing the carbon compound and the carbon dioxide flows; an anode discharge flow path connected to an outlet of the anode flow path, through which an anode discharge fluid discharged from the anode flow path and containing the oxygen and the water flows; a cathode flow rate regulator that regulates a flow rate A of the cathode supply fluid supplied to the cathode flow path; an anode flow rate regulator that regulates the flow rate B of the anode supply fluid that is supplied to the anode flow path; a first flow meter that measures a flow rate C of the cathode discharge fluid discharged from the cathode flow channel; a second flow meter that measures a flow rate D of the anode exhaust fluid discharged from the anode flow channel; Equipped with The electrolysis method comprises: using measurement data of the flow rate C from the first flow meter and measurement data of the flow rate D from the second flow meter, estimating a value of the Faraday efficiency of the carbon compound according to a relational expression that approximates the value of the Faraday efficiency to a function including the flow rates C and D; controlling the cathode flow regulator in accordance with the estimated value of the Faraday efficiency to control the flow rate A; Electrolysis method.

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