Carbon dioxide conversion device and carbon dioxide conversion method

Abstract

To provide a carbon dioxide conversion device which promotes effective utilization of CO2, and can efficiently produce CO which is a reduction product of the CO2.SOLUTION: A carbon dioxide conversion device 1 includes: a carbon dioxide electrolytic part 3 including a cathode chamber 11 for producing first gas containing carbon monoxide and hydrogen, and an anode chamber 12 for producing second gas containing oxygen and carbon dioxide; a direct current power source 14; an organic matter synthesis part 4 for synthesizing an organic matter from the raw material gas containing the first gas; an oxygen removal chamber 22 to which the second gas is supplied; an oxygen permeable film type partial oxidation part 5 having a partial oxidation chamber 21 for partially oxidizing residual synthesis gas discharged from the organic matter synthesis part 4, and producing third gas containing carbon monoxide and hydrogen; and a first measurement control part 33 for controlling a supply amount of the second gas to the oxygen removal chamber 22 from the anode chamber 12 so that an amount of carbon monoxide in the third gas produced by the partial oxidation chamber is increased.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a carbon dioxide conversion device and a carbon dioxide conversion method.

Background Art

[0002] Carbon dioxide (CO2) generated by burning fossil fuels such as natural gas, coal, and oil is considered to be a major cause of global warming due to the greenhouse effect, and reduction of fossil fuel use is demanded. In addition to removing CO2 from the exhaust gas discharged from the CO2 source and suppressing its release into the atmosphere, chemical synthesis using the CO2 removed from the exhaust gas as a raw material is being carried out. As part of this, development of a technology for reducing CO2 to produce carbon monoxide (CO) and synthesizing organic substances from the produced CO and hydrogen (H2) is in progress. A part of the purge gas after CO generation is supplied to an electrolysis device for CO2, and the remainder is burned in air to be detoxified and released into the atmosphere. The CO2 supplied to purge the oxygen generated from the CO2 electrolysis device and the CO2 released from the combustion device are released into the atmosphere without being effectively utilized among the CO2 supplied to the CO2 electrolysis device. For this reason, there is a demand for a carbon dioxide conversion device and a carbon dioxide conversion method that enable effective utilization of the supplied CO2, reduce the release of CO2 into the atmosphere, and efficiently produce CO, which is a reduction product of CO2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0004] The problem that this invention aims to solve is to provide a carbon dioxide conversion device and a carbon dioxide conversion method that promote the effective utilization of CO2, reduce the release of CO2 into the atmosphere, and enable the efficient generation of CO, which is a reduction product of CO2. [Means for solving the problem]

[0005] The carbon dioxide conversion apparatus of the embodiment includes a carbon dioxide recovery unit that recovers carbon dioxide from a carbon dioxide-containing gas; a carbon dioxide electrolysis unit to which the carbon dioxide recovered in the carbon dioxide recovery unit is supplied and which reduces the carbon dioxide and / or water to produce a first gas containing carbon monoxide and / or hydrogen; an anode chamber to which an oxide is oxidized to produce a second gas containing oxygen and carbon dioxide; a DC power supply that supplies a DC current to the carbon dioxide electrolysis unit; an organic matter synthesis unit to which the first gas is supplied from the cathode chamber of the carbon dioxide electrolysis unit and which synthesizes organic matter from a raw material gas containing the first gas; and a second gas supplied from the anode chamber, the The oxygen permeable membrane type partial oxidation unit comprises an oxygen removal chamber that ionizes oxygen in a gas to generate oxygen ions, a partial oxidation chamber to which the residual synthesis gas of the organic matter discharged from the organic matter synthesis unit is supplied, the residual synthesis gas is partially oxidized by the oxygen ions generated in the oxygen removal chamber to generate a third gas containing carbon monoxide and hydrogen, and the third gas is supplied to the organic matter synthesis unit as part of the raw material gas, and an oxygen permeable membrane disposed between the oxygen removal chamber and the partial oxidation chamber, and a first measurement and control unit that controls the amount of the second gas supplied from the anode chamber to the oxygen removal chamber to increase the amount of carbon monoxide in the third gas generated in the partial oxidation chamber. [Brief explanation of the drawing]

[0006] [Figure 1] This is a diagram showing a carbon dioxide conversion device according to an embodiment. [Figure 2]Figure 1 is a flow chart showing how to control the amount of carbon monoxide in the third gas in the carbon dioxide conversion device. [Figure 3] Figure 1 is a flow chart showing how to control the carbon monoxide / hydrogen ratio in the third gas of the carbon dioxide conversion device. [Figure 4] This is a flow chart showing the control of the flow rate of the first gas in the carbon dioxide conversion device shown in Figure 1. [Figure 5] This is a flow chart showing how to control the flow rate of carbon dioxide-containing gas in the carbon dioxide conversion device shown in Figure 1. [Modes for carrying out the invention]

[0007] The carbon dioxide conversion apparatus of the embodiment will be described below with reference to the drawings. In each embodiment shown below, substantially identical components are denoted by the same reference numerals, and their descriptions may be partially omitted. The drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of the thickness of each part, etc., may differ from reality. In the following description, the symbol "~" indicates the range between the upper and lower limits of each numerical value. In this case, each numerical range includes both the upper and lower limits.

[0008] Figure 1 shows a carbon dioxide conversion device according to an embodiment. The carbon dioxide conversion device 1 shown in Figure 1 comprises a CO2 recovery unit 2 that recovers CO2 from a carbon dioxide (CO2)-containing gas, a CO2 electrolysis unit 3 that electrolyzes and reduces CO2 to convert it into carbon monoxide (CO), an organic matter synthesis unit 4 that synthesizes organic matter using a gas containing carbon monoxide (CO) and hydrogen (H2) supplied from the CO2 electrolysis unit 3 as raw material gas, and an oxygen permeable membrane type partial oxidation unit 5 that partially oxidizes the residual gas from the organic matter synthesis discharged from the organic matter synthesis unit 4 to produce CO and H2.

[0009] The CO2 recovery unit 2 is configured to separate and recover CO2 from exhaust gas (CO2-containing gas) G1 emitted from thermal power plants, waste incineration plants, steel mills, etc., and to supply the CO2 gas G2 with increased CO2 concentration to the CO2 electrolysis unit 3. The CO2 recovery unit 2 can be fitted with various CO2 recovery methods, such as chemical absorption using a chemical absorbent such as an amine aqueous solution, physical absorption using a physical absorbent such as methanol or polyethylene glycol solution, solid absorption using a solid absorbent such as an amine compound, membrane separation using a CO2 separation membrane, physical adsorption using inorganic materials such as zeolite as adsorbents, PSA (Pressure Swing Adsorption), TSA (Thermal Swing Adsorption), etc. For example, in a chemical absorption method and apparatus using an amine aqueous solution, exhaust gas G1 is supplied to an absorption tower into which the amine aqueous solution is sprayed, and the amine aqueous solution that has absorbed CO2 is heated in a regeneration tower to recover the CO2 released from the amine aqueous solution. The CO2 recovery method and apparatus applied to the CO2 recovery unit 2 are not particularly limited, and various methods and apparatus capable of recovering CO2 from exhaust gas G1 can be applied.

[0010] CO2-containing gas G1 is supplied to the CO2 recovery unit 2 via a first flow rate adjustment valve 6 and a gas mixer 7. The CO2 recovery unit 2 is connected to the cathode chamber (reduction unit) 11 of the CO2 electrolysis unit 3 via a first flow meter 8, a first buffer tank 9, and a second flow rate adjustment valve 10. The CO2 recovery unit 2 is configured to supply CO2 gas G2 to the cathode chamber 11 via these components (8, 9, 10).

[0011] The CO₂ electrolysis unit 3 is a CO₂ electrolyzer having an electrolytic cell, and includes a cathode chamber (reduction section) 11 and an anode chamber (oxidation section) 12. The cathode chamber 11 includes a reduction electrode (cathode), and the anode chamber 12 includes an oxidation electrode (anode). At least an electrolytic solution flows through the anode chamber 12. CO₂ gas is circulated through the cathode chamber 11. In the anode chamber 12, a solution using water (H₂O), for example, an aqueous solution containing an arbitrary electrolyte, is used as the electrolytic solution. As the aqueous solution containing an electrolyte, an aqueous solution containing phosphate ions (PO₄ 2- ), borate ions (BO₃ 3- ), sodium ions (Na + ), potassium ions (K + ), calcium ions (Ca 2+ ), lithium ions (Li + ), cesium ions (Cs + ), magnesium ions (Mg 2+ ), chloride ions (Cl - ), hydrogen carbonate ions (HCO₃ - ), carbonate ions (CO₃ 2- ), hydroxide ions (OH - ), etc. can be mentioned. Specific examples of the electrolytic solution include an alkaline aqueous solution in which KOH, KHCO₃, K₂CO₃, etc. are dissolved.

[0012] The CO₂ gas G2 recovered by the CO₂ recovery unit 2 is supplied to the cathode chamber 11. The cathode chamber 11 has a gas flow path facing the reduction electrode (not shown), and CO₂ gas is supplied to such a gas flow path. The anode chamber 12 has, for example, a liquid flow path facing the oxidation electrode (not shown), and an electrolytic solution is supplied to such a liquid flow path. The cathode chamber 11 and the anode chamber 12 are separated by hydrogen ions (H + ), hydroxide ions (OH - ), carbonate ions (CO₃ 2- ), hydrogen carbonate ions (HCO₃ -The ions are separated by a diaphragm 13, such as an ion exchange membrane, which is capable of moving ions such as ions. The CO2 electrolysis unit 3 (CO2 electrolysis apparatus having an electrolytic cell) may have a single electrolytic cell or a structure in which they are connected in the planar direction, or it may have a stack structure in which multiple electrolytic cells are stacked and integrated.

[0013] A DC power supply 14 is connected to the reduction electrode and oxidation electrode of the CO2 electrolysis unit 3. In the CO2 electrolysis unit 3, the following electrolytic reactions occur when a DC current is supplied from the DC power supply 14 to the reduction electrode and oxidation electrode. That is, the following reactions occur in the cathode chamber 11 and anode chamber 12 of the CO2 electrolysis unit 3. In the cathode chamber 11, the electrolytic and reduction reactions of CO2 occur as shown in equation (1) below. In the cathode chamber 11, the reduction reaction of CO2 produces CO and carbonate ions (CO3). 2- ) is generated. 2CO2 + 2e - → CO+CO3 2- …(1) Carbonate ions (CO3) are generated in cathode chamber 11. 2- The carbonate ions (CO3) generated in the cathode chamber 11 and moved through the membrane 13 move to the anode chamber 12. In the anode chamber 12, as shown in equation (2) below, the carbonate ions (CO3) generated in the cathode chamber 11 and moved through the membrane 13 move to the anode chamber 12. 2- An oxidation reaction occurs, producing CO2 and O2. CO3 2- → CO2 + 0.5O2 + 2e - …(2)

[0014] Furthermore, in the cathode chamber 11, an electrolytic reaction occurs with H2O in the electrolyte, and as shown in equation (3) below, hydrogen (H2) and hydroxide ions (OH) are produced. - ) and are generated. 2H2O + 2e - → H2 + 2OH - …(3) hydroxide ions (OH) generated in cathode chamber 11 -The ) moves to the anode chamber 12 via the diaphragm 13. Then, as shown in equation (4) below, water (H2O) and oxygen (O2) are produced in the anode chamber 12. 2OH - → 0.5O2 + H2O + 2e - …(4)

[0015] Furthermore, in the anode chamber 12, as shown in equation (5) below, water (H2O) in the electrolyte is electrolyzed to produce oxygen (O2) and hydrogen ions (H + ) and are generated. 2H2O → 4H + +O2+4e - …(5) The generated hydrogen ions (H + The hydrogen ions (H) move to the cathode chamber 11 via the diaphragm 13. + ) reaches, and electrons (e - In the cathode chamber 11, where the hydrogen gas reaches, hydrogen is generated by the reaction shown in equation (6) below. 4H + +4e - → 2H2…(6)

[0016] In the cathode chamber 11, CO is generated by the reduction reaction of CO2 shown in equation (1), and H2 is generated by the electrolytic reaction of H2O shown in equation (3) and the reaction shown in equation (6). The CO and / or H2 generated in the cathode chamber 11 are discharged from the cathode chamber 11 along with unreacted CO2 and saturated water vapor. The mixed gas (first gas) G3 containing CO and / or H2 and / or CO2, which is discharged from the cathode chamber 11, is cooled (not shown) to separate condensed water, and then supplied to the organic synthesis unit 4 as part of the raw material gas for the organic synthesis reaction. The cathode chamber 11 is connected to the organic synthesis unit 4 via a mixer 15, a CO / H2 concentration meter 16, a second flow meter 17, a second buffer tank 18, and a compressor 19. The mixed gas G3 is sent to the second buffer tank 18, pressurized to a predetermined pressure by the compressor 19, and then sent to the organic synthesis unit 4. Although not shown in the diagram, a CO2 separation unit for separating and recovering CO2 from the mixed gas G3 may be provided between the cathode chamber 11 and the organic matter synthesis unit 4 (for example, between the cathode chamber 11 and the mixer 15). The CO2 separated and recovered here is then sent back to the cathode chamber 11.

[0017] In the organic synthesis unit 4, to which a mixed gas containing CO and / or H2 is supplied, organic synthesis reactions, such as the Fischer-Tropsch synthesis reaction, are carried out to synthesize organic substances, such as hydrocarbons, alcohols, and other organic substances. Specific examples of organic substances synthesized in the organic synthesis unit 4 include carbon-containing liquid fuels. The products (organic substances) from the organic synthesis unit 4 are discharged and sent to a storage facility (not shown), such as a separately installed tank. The organic synthesis residue gas G4 is discharged from the organic synthesis unit 4. The synthesis residue gas G4 contains unwanted products such as residual CO, H2, CO2, and lower hydrocarbons such as methane (CH4). This synthesis residue gas G4 discharged from the organic synthesis unit 4 is heated in the regenerative heat exchanger 20 and then sent to the partial oxidation chamber 21 of the oxygen permeable membrane type partial oxidation unit 5. The oxygen permeable membrane type partial oxidation unit 5 consists of a partial oxidation chamber 21, an oxygen removal chamber 22, and an oxygen permeable membrane 23 placed between them.

[0018] On the other hand, in the anode chamber 12 of the CO2 electrolysis unit 3, as shown in equations (2) and (4) above, carbonate ions (CO3 2- ) and hydroxide ions (OH - Oxidation of ) produces oxygen (O2) and carbon dioxide (CO2). The gas containing O2 and CO2 (O2-CO2 containing gas / second gas) generated in the anode chamber 12 is discharged from the anode chamber 12 together with the electrolyte. The electrolyte containing the O2-CO2 containing gas is sent to the gas-liquid separator 24, where the O2-CO2 containing gas is separated from the electrolyte. The electrolyte separated in the gas-liquid separator 24 is cooled to a predetermined temperature in the cooler 25 and then returned to the anode chamber 12.

[0019] The O2-CO2-containing gas G5 separated in the gas-liquid separator 24 contains a relatively high concentration of CO2, 30-60% by volume. If released directly into the atmosphere, it would hinder the effective utilization of CO2 and would not help prevent global warming caused by CO2. Furthermore, because the O2-CO2-containing gas G5 contains a relatively large amount of O2, sending it directly to the cathode chamber 11 would degrade the operation and function of the CO2 electrolysis unit 3. Therefore, the O2-CO2-containing gas G5 discharged from the anode chamber 12 of the CO2 electrolysis unit 3 and separated and recovered in the gas-liquid separator 24 is sent to the oxygen removal chamber 22 of the oxygen-permeable membrane type partial oxidation unit 5. The O2-CO2-containing gas G5 is sent to the oxygen removal chamber 22 via the cooler 26, gas-liquid separator 27, third flow rate adjustment valve 28, and regenerative heat exchanger 29. The O2-CO2-containing gas G5 is cooled to a predetermined temperature in the cooler 26, condensed water is separated in the gas-liquid separator 27, and after being heated in the regenerative heat exchanger 29, it is sent to the oxygen removal chamber 22.

[0020] The oxygen permeable membrane type partial oxidation section 5 comprises a partial oxidation chamber 21, an oxygen removal chamber 22, and an oxygen permeable membrane 23 arranged to separate them. A dense solid oxide electrolyte layer is used as the oxygen permeable membrane 23. The solid oxide electrolyte layer is an ion conductor that allows ions such as oxygen ions to pass through but does not allow gases to pass through. As the solid oxide electrolyte layer, for example, stabilized zirconia in which oxides of rare earth elements such as Y, Sc, Ce, Gd, and Sm are solid-solved as stabilizers, typically yttria-stabilized zirconia (YSZ) or ceria-stabilized zirconia (CSZ), or composites thereof are used.

[0021] The oxygen permeable membrane type partial oxidation section 5 has a structure in which a partial oxidation chamber 21, which serves as a first electrode chamber having a first electrode, and an oxygen removal chamber 22, which serves as a second electrode chamber having a second electrode, are separated by an oxygen permeable membrane 23 made of a solid oxide electrolyte layer or the like. The two electrodes are, for example, directly connected and short-circuited. The oxygen removal chamber 22, which serves as the second electrode chamber, removes oxygen molecules (O2) and oxygen ions (O2). 2- It is responsible for the conversion to ). The partial oxidation chamber 21, which serves as the first electrode chamber, is responsible for the conversion of oxygen ions (O 2- It is responsible for the conversion of ) to oxygen molecules (O2) and for the partial oxidation of lower hydrocarbons such as methane (CH4). When a mixed conductor is used as the oxygen permeable membrane 23, short circuits due to direct connection between electrodes (catalyst layers) are unnecessary. As a mixed conductor, (La 1-x Sr x )(Co 1-y Fe y )O3, (Ba 1-x Sr x )(Co 1-y Fe y )O3, (Pr 1-x Sr x )(Fe 1-y Al y )O3, (La 1-x-y Ba x Sr y )(Fe 1-z In z ) Perovskites such as O3, (Ce 1-x RE x)O2-MnFe2O4(RE=La, Pr, Sm, Gd), or a complex of these, is used.

[0022] In the oxygen permeable membrane type partial oxidation section 5 described above, the O2-CO2-containing gas G5 discharged from the anode chamber 12 of the CO2 electrolysis section 3 is supplied to the oxygen removal chamber 22. In the oxygen removal chamber 22, the O2 in the O2-CO2-containing gas G5 is converted into oxygen ions (O) as shown in equation (7) below. 2- It will be converted to ). O2+4e - → 2O 2- …(7) Oxygen ions converted in oxygen removal chamber 22 (O 2- The oxygen ions (O) sent to the partial oxidation chamber 21 are delivered via the oxygen permeable membrane 23. 2- ) is converted to oxygen molecules (O2) as shown in equation (8) below. 20 2- → O2+4e - …(8)

[0023] In the partial oxidation chamber 21, as shown in equation (9) below, methane (CH4) and other compounds contained in the synthesis residue gas G4 are partially oxidized and converted to CO and H2. In the partial oxidation chamber 21, a gas containing CO and H2 (CO-H2-containing gas / third gas) is produced. Partial oxidation refers to a reaction in which, for example, in the oxidation of lower hydrocarbons such as methane (CH4), C is partially oxidized without being oxidized to stable CO2, as shown in equation (9), to produce H2-rich CO (a partially oxidized state of C). 2CH4 + O2 → 2CO + 4H2…(9) Furthermore, as shown in equation (10) below, CO2 and H2 are converted to CO and H2O by a reverse aqueous shift reaction. CO2 + H2 → CO + H2O …(10)

[0024] As the oxygen-permeable membrane type partial oxidation unit 5, an oxygen ion-conducting electrolytic device or an oxygen ion-conducting fuel cell may be used. As an oxygen ion-conducting electrolytic device, for example, a solid oxide electrolysis cell (SOEC) is used. The SOEC comprises a hydrogen electrode chamber, an oxygen electrode chamber, and an oxygen-permeable membrane arranged to separate them. The hydrogen electrode (cathode) located in the hydrogen electrode chamber and the oxygen electrode (anode) located in the oxygen electrode chamber are connected to a power source. As an oxygen ion-conducting fuel cell, for example, a solid oxide fuel cell (SOFC) is used. The SOFC comprises a fuel electrode chamber, an air electrode chamber, and an oxygen-permeable membrane arranged to separate them.

[0025] In this case, the entire amount of O2-CO2-containing gas released from the anode chamber 12 of the CO2 electrolysis unit 3 is supplied to the reducing electrode of the SOFC or SOEC. The amount of oxygen transferred from the reducing electrode of the SOFC or SOEC to the oxidizing electrode of the SOFC or SOEC can be controlled by the current value to adjust the CO concentration of the gas released from the oxidizing electrode of the SOFC or SOEC. At the reducing electrode of the SOFC or SOEC, the reaction shown in equation (11) below occurs. At the oxidizing electrode of the SOFC or SOEC, the reactions shown in equations (12) and (13) below occur. Reduction electrode: O2+2e - → 2O 2- …(11) Oxidation electrode: 2O 2- → O2 + 2e - …(12) CH4 + O2 → CO + 2H2…(13)

[0026] From the partial oxidation chamber 21 of the oxygen permeable membrane type partial oxidation section 5, a gas containing CO and H2 (CO-H2-containing gas (third gas) G6) is discharged. Since the CO-H2-containing gas G6 is used as part of the raw material gas in the organic synthesis section 4, it is sent to the mixer 15 via the regenerative heat exchanger 20, cooler 30, gas-liquid separator 31, and CO concentration meter 32. The CO-H2-containing gas G6 is cooled in the regenerative heat exchanger 20 and cooler 30, and after condensate water is removed in the gas-liquid separator 31, it is sent to the second buffer tank 18 via the mixer 15. The CO-H2-containing gas G6, mixed with CO-H2-containing gas G3, is sent from the second buffer tank 18 to the compressor 19, where it is pressurized to a predetermined pressure before being sent to the organic synthesis section 4.

[0027] From the oxygen removal chamber 22 of the oxygen-permeable membrane type partial oxidation unit 5, O2-CO2-containing gas (low-concentration O2-CO2-containing gas) G7 with reduced oxygen concentration is discharged. Since the low-concentration O2-CO2-containing gas G7 contains a relatively high concentration of CO2, it is heated in the regenerative heat exchanger 29 and then returned to the CO2 recovery unit 2 for reuse. Even though the oxygen concentration of the low-concentration O2-CO2-containing gas G7 has been reduced, it still contains a certain amount of O2. For this reason, the low-concentration O2-CO2-containing gas G7 is returned to the CO2 recovery unit 2, where the CO2 is separated and recovered, and the CO2-concentrated CO2 gas G2 is sent to the cathode chamber 11 of the CO2 electrolysis unit 3 for reuse. Because the O2 concentration of the O2-CO2-containing gas G7 is low, it can reduce the oxygen degradation of, for example, the amine aqueous solution (amine absorbent) used in the CO2 recovery unit 2.

[0028] As described above, the synthesis residual gas G4 containing unnecessary products such as methane (CH4) is sent to the partial oxidation chamber 21 of the oxygen permeable membrane type partial oxidation unit 5, and methane (CH4) etc. are partially oxidized to resynthesize CO and H2, whereby the synthesis residual gas G4 can be effectively utilized as part of the raw material gas of the organic substance synthesis unit 4. Further, the O2-CO2 containing gas G5 discharged from the anode chamber 12 of the CO2 electrolysis unit 3 is supplied to the oxygen removal chamber 22, and after contributing to the regeneration of the above-mentioned CO and H2, the oxygen concentration in the O2-CO2 containing gas G5 is reduced. Thereby, the low-concentration O2-CO2 containing gas G7 with an increased CO2 concentration can be returned to the CO2 recovery unit 2 to promote the reuse of CO2.

[0029] The CO concentration in the CO-H2 containing gas G6 generated in the partial oxidation chamber 21 of the oxygen permeable membrane type partial oxidation unit 5 varies depending on the flow rate etc. of the O2-CO2 containing gas G5 supplied to the oxygen removal chamber 22. Therefore, the CO concentration in the CO-H2 containing gas G6 is measured by the CO concentration meter 32 provided downstream of the partial oxidation chamber 21 and the gas-liquid separator 31, and based on the measured CO concentration, the flow rate of the O2-CO2 containing gas G5 is adjusted by the third flow rate adjustment valve 28. Thereby, it becomes possible to increase the CO concentration in the gas G6 and increase the amount of CO in the raw material gas of the organic substance synthesis unit 4. The specific method for adjusting the flow rate of the CO concentration in the CO-H2 containing gas G6 is as shown in FIG. 2, for example.

[0030] As shown in FIG. 2, first, the CO concentration 1 in the CO-H2 containing gas G6 is measured (S101), and the measurement data of the CO concentration 1 is sent to the first measurement control unit 33. Next, an opening signal 1 for increasing the opening degree of the third flow rate adjustment valve 28 is sent from the first measurement control unit 33 to the third flow rate adjustment valve 28 (S102). After increasing the opening degree of the third flow rate adjustment valve 28, the CO concentration 2 in the gas G6 is measured (S103), and it is determined whether the CO concentration 2 is greater than the CO concentration 1 (CO concentration 1 < CO concentration 2) (S104). If the CO concentration 2 is greater than the CO concentration 1 (yes), the opening signal 1 of the third flow rate adjustment valve 28 is increased (S102).

[0031] Similarly, the measurement of the CO concentration 2 in the gas G6 (S103) and the determination of whether the CO concentration 2 is greater than the CO concentration 1 (S104) are carried out. When the CO concentration 2 is greater than the CO concentration 1 (yes), the above-described steps are carried out. When it is not greater (no), it is determined whether the CO concentration 2 is approximately equal to the CO concentration 1 (CO concentration 1 = CO concentration 2) (S105). When the CO concentration 2 is approximately equal to the CO concentration 1 (yes), the opening degree signal 1 of the third flow rate adjustment valve 28 is maintained (S106). When the CO concentration 2 is not approximately equal to the CO concentration 1 (no), an opening degree signal 1 for decreasing the opening degree of the third flow rate adjustment valve 28 is sent from the first measurement control unit 33 to the third flow rate adjustment valve 28 (S107).

[0032] Next, the CO concentration 2 in the gas G6 is measured (S108), and it is determined whether the CO concentration 2 is greater than the CO concentration 1 (CO concentration 1 < CO concentration 2) (S109). When the CO concentration 2 is greater than the CO concentration 1 (yes), the opening degree signal 1 of the third flow rate adjustment valve 28 is decreased (S107). Similarly, the measurement of the CO concentration 2 in the gas G6 (S108) and the determination of whether the CO concentration 2 is greater than the CO concentration 1 (S109) are carried out. When the CO concentration 2 is greater than the CO concentration 1 (yes), the above-described steps are carried out. When it is not greater (no), it is determined whether the CO concentration 2 is approximately equal to the CO concentration 1 (CO concentration 1 = CO concentration 2) (S110). When the CO concentration 2 is approximately equal to the CO concentration 1 (yes), the opening degree signal 1 of the third flow rate adjustment valve 28 is maintained (S111). When the CO concentration 2 is not approximately equal to the CO concentration 1 (no), an opening degree signal 1 for increasing the opening degree of the third flow rate adjustment valve 28 is sent from the first measurement control unit 33 to the third flow rate adjustment valve 28 (S102). In this way, by increasing the CO concentration in the gas G7, it becomes possible to increase the amount of CO in the raw material gas of the organic substance synthesis unit 4.

[0033] As described above, increasing the CO concentration in the CO-H2-containing gas G6 produced in the partial oxidation chamber 21 may lead to a shortage of H2 in the raw material gas, potentially lowering the CO / H2 ratio. Therefore, an H2 supply unit (H2 source) 35 is connected to the mixer 15 via a fourth flow rate adjustment valve 34. By supplying H2 from the H2 source 35 to the CO-H2-containing gas, the CO / H2 ratio of the CO-H2-containing gas supplied to the organic synthesis unit 4 as a raw material gas can be adjusted. However, uniformly adding H2 from the H2 source 35 to the CO-H2-containing gas does not maintain the set CO / H2 ratio. Therefore, the CO concentration and H2 concentration are measured using a CO / H2 concentration meter 16 installed downstream of the second buffer tank 18, and the amount of H2 added from the H2 source 35 is adjusted by the fourth flow rate adjustment valve 34 based on the measured CO concentration and H2 concentration. This allows the CO / H2 ratio of the CO-H2-containing gas to be brought closer to the set value, thereby increasing the yield and synthesis efficiency of the organic synthesis unit 4. A specific method for adjusting the flow rate of the CO / H2 ratio in the CO-H2-containing gas is shown in Figure 3, for example.

[0034] As shown in Figure 3, first, the CO concentration (S201) and H2 concentration (S202) in the CO-H2-containing gas are measured, and these measurement data are sent to the second measurement control unit 36. The second measurement control unit 36 ​​calculates the CO / H2 ratio from the measurement data (S203). Furthermore, it calculates the value of [CO / H2 ratio - set value] and determines whether the value of [CO / H2 ratio - set value] is greater than 0 (S204). If the value of [CO / H2 ratio - set value] is greater than 0, the opening signal 2 of the fourth flow control valve 34 is increased (S102). If the value of [CO / H2 ratio - set value] is less than 0, the opening signal 2 of the fourth flow control valve 34 is decreased (S102). If the value of [CO / H2 ratio - set value] is 0, the opening signal 2 of the fourth flow control valve 34 is maintained. By repeating these steps, it becomes possible to bring the CO / H2 ratio of the CO-H2-containing gas closer to the set value.

[0035] The flow rate of the CO-H2-containing gas supplied as a raw material gas to the organic synthesis unit 4 is also affected by the flow rate of the CO-H2-containing gas G3 produced in the cathode chamber 11. The yield and synthesis efficiency of organic matter in the organic synthesis unit 4 are also affected by the amount of raw material gas supplied. Therefore, the flow rate of the CO-H2-containing gas is measured using a second flow meter 17 installed upstream of the second buffer tank 18, and the flow rate of the CO2 gas G2 supplied to the cathode chamber 11 is adjusted based on the measured gas flow rate, as well as the current value supplied to the CO2 electrolysis unit 3 from the DC power supply 14. This makes it possible to bring the amount of raw material gas supplied to the organic synthesis unit 4 closer to the set value. A specific method for adjusting the flow rate of the CO-H2-containing gas G3 is shown in Figure 4, for example.

[0036] As shown in Figure 4, first the flow rate 1 of the CO-H2-containing gas supplied to the organic synthesis unit 4 is measured by the second flow meter 17 (S301), and this measurement data is sent to the third measurement control unit 37. The third measurement control unit 37 calculates the value of [flow rate 1 - set value] from the measurement data and determines whether the value of [flow rate 1 - set value] is greater than 0 (S302). If the value of [flow rate 1 - set value] is greater than 0, the opening signal 3 of the second flow control valve 10 and the current value signal supplied from the DC power supply 14 are increased (S303). If the value of [flow rate 1 - set value] is less than 0, the opening signal 3 of the second flow control valve 10 and the current value signal supplied from the DC power supply 14 are decreased (S304). If the value of [flow rate 1 - set value] is 0, the opening signal 3 of the second flow control valve 10 and the current value signal supplied from the DC power supply 14 are maintained. By repeating this process, it becomes possible to bring the flow rate 1 of the CO-H2-containing gas closer to the set value.

[0037] Furthermore, the flow rate of the CO-H2-containing gas supplied as a raw material gas to the organic synthesis unit 4 is also affected by the flow rate of the CO2 gas G2 supplied to the cathode chamber 11. Therefore, the flow rate of the CO2 gas G2 is measured by the first flow meter 8 installed upstream of the first buffer tank 18, and the flow rate of the CO2-containing gas G1 supplied to the CO2 recovery unit 2 is adjusted by the first flow rate adjustment valve 6 based on the measured gas flow rate. This makes it possible to bring the amount of raw material gas supplied to the organic synthesis unit 4 closer to the set value. A specific method for adjusting the flow rate of the CO2-containing gas G2 is shown in Figure 5, for example.

[0038] As shown in Figure 5, first the flow rate 2 of the CO2 gas G2 supplied to the cathode chamber 11 is measured by the first flow meter 8 (S401), and this measurement data is sent to the fourth measurement control unit 38. The fourth measurement control unit 38 calculates the value of [flow rate 2 - set value] from the measurement data and determines whether the value of [flow rate 2 - set value] is greater than 0 (S402). If the value of [flow rate 2 - set value] is greater than 0, the opening signal 4 of the first flow control valve 6 is increased (S403). If the value of [flow rate 2 - set value] is less than 0, the opening signal 4 of the first flow control valve 6 is decreased (S404). If the value of [flow rate 2 - set value] is 0, the opening signal 4 of the first flow control valve 6 is maintained. By repeating this process, it becomes possible to bring the flow rate 2 of the CO2 gas G2 supplied to the cathode chamber 11 closer to the set value.

[0039] In addition to adjusting gas concentration and gas flow rate as described above, the methane flow rate may be calculated from the flow rate of the residual organic synthesis gas G4 discharged from the organic synthesis unit 4 and the methane (CH4) concentration, and the flow rate of the O2-CO2-containing gas G5 discharged from the anode chamber 12 may be controlled based on this. The required flow rate of the O2-CO2-containing gas G5 can also be effectively corrected by adjusting the amount of water vapor based on the gas temperature or by adjusting the oxygen concentration. The required amount of oxygen can be calculated using the characteristics of the oxygen-permeable partial oxidation unit 5. Furthermore, the hydrogen flow rate required for a predetermined CO / H2 ratio may be calculated and supplied from the flow rate, CO concentration, and H2 concentration after mixing the CO and H2-containing gas G3 discharged from the cathode chamber 11 of the CO2 electrolysis unit 3 and the CO and H2-containing gas G6 discharged from the partial oxidation unit 21 of the oxygen-permeable membrane type partial oxidation unit 5.

[0040] The amount of CO2-containing gas supplied may be controlled based on the flow rate, CO2 concentration, and CO2 concentration of the CO2-containing gas after mixing the bypass flow of O2-CO2-containing gas released from the anode chamber 12 of the CO2 electrolysis unit 3 with the low-concentration O2-CO2-containing gas released from the oxygen removal chamber of the oxygen permeable membrane type partial oxidation unit 5.

[0041] Although not shown in the above-described embodiment and Figure 1, blowers, pumps, compressors, etc., may be appropriately arranged to assist the fluid flow. Furthermore, a portion of the gas released from the CO2 recovery unit may be provided for other uses such as underground storage, EOR (End-Oil Recovery), and CO2 fixation (mineralization).

[0042] The configurations of the embodiments described above can be applied in combination or partially substituted. While several embodiments of the present invention have been described here, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as described in the claims. [Explanation of symbols]

[0043] 1...CO2 conversion device, 2...CO2 recovery unit, 3...CO2 electrolysis unit, 4...Organic material synthesis unit, 5...Oxygen permeable membrane type partial oxidation unit, 6...First flow rate adjustment valve, 8...First flow meter, 10...Second flow rate adjustment valve, 11...Cathode chamber, 12...Anode chamber, 13...Diaphragm, 16...CO / H2 concentration meter, 17...Second flow meter, 21...Partial oxidation chamber, 22...Oxygen removal chamber, 23...Oxygen permeable membrane, 28...Third flow rate adjustment valve, 32...CO concentration meter, 33...First measurement control unit, 34...Fourth flow rate adjustment valve, 35...H2 source, 36...Second measurement control unit, 37...Third measurement control unit, 38...Fourth measurement control unit.

Claims

1. A carbon dioxide recovery unit that recovers carbon dioxide from carbon dioxide-containing gas, A carbon dioxide electrolysis unit comprising a cathode chamber to which carbon dioxide recovered in the carbon dioxide recovery unit is supplied, and which reduces the carbon dioxide and / or water to produce a first gas containing carbon monoxide and / or hydrogen, and an anode chamber to which an oxide is oxidized to produce a second gas containing oxygen and carbon dioxide, A DC power supply that supplies DC current to the carbon dioxide electrolysis unit, The first gas is supplied from the cathode chamber of the carbon dioxide electrolysis unit, and an organic matter synthesis unit synthesizes organic matter from a raw material gas containing the first gas, An oxygen permeable membrane type partial oxidation unit comprising: an oxygen removal chamber to which the second gas is supplied from the anode chamber and the oxygen in the second gas is ionized to generate oxygen ions; a partial oxidation chamber to which the residual synthesis gas of the organic matter discharged from the organic matter synthesis unit is supplied, the residual synthesis gas is partially oxidized by the oxygen ions generated in the oxygen removal chamber to generate a third gas containing carbon monoxide and hydrogen, and the third gas is supplied to the organic matter synthesis unit as part of the raw material gas; and an oxygen permeable membrane disposed between the oxygen removal chamber and the partial oxidation chamber, A first measurement and control unit controls the amount of the second gas supplied from the anode chamber to the oxygen removal chamber to increase the amount of carbon monoxide in the third gas generated in the partial oxidation chamber. A carbon dioxide conversion device equipped with the following features.

2. Furthermore, a hydrogen supply unit that supplies hydrogen gas to the raw material gas, A second measurement and control unit controls the amount of hydrogen gas supplied by the hydrogen supply unit to adjust the ratio of carbon monoxide to hydrogen in the raw material gas. A carbon dioxide conversion apparatus according to claim 1, comprising the following:

3. Furthermore, a third measurement and control unit controls the amount of carbon dioxide supplied to the cathode chamber and the value of the DC current supplied from the DC power supply to the carbon dioxide electrolysis unit, in order to adjust the amount of the raw material gas supplied to the organic synthesis unit. A carbon dioxide conversion apparatus according to claim 1, comprising the following:

4. Furthermore, a fourth measurement and control unit controls the amount of carbon dioxide-containing gas supplied to the carbon dioxide recovery unit in order to adjust the amount of carbon dioxide supplied from the carbon dioxide recovery unit to the cathode chamber. A carbon dioxide conversion apparatus according to claim 1, comprising the following:

5. The carbon dioxide conversion apparatus according to claim 1, wherein the oxygen permeable membrane type partial oxidation unit is configured to discharge carbon dioxide-containing residual gas with reduced oxygen concentration from the oxygen removal chamber and to supply the carbon dioxide-containing residual gas to the carbon dioxide recovery unit.

6. The carbon dioxide conversion apparatus according to claim 1, wherein the oxygen permeable membrane type partial oxidation unit is equipped with an oxygen ion conducting type electrolytic device.

7. The carbon dioxide conversion apparatus according to claim 1, wherein the oxygen permeable membrane type partial oxidation unit comprises an oxygen ion conducting fuel cell.

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