Carbon dioxide reforming methods and carbon dioxide reforming systems

Abstract

The disclosed carbon dioxide modification method includes: a carbon dioxide acquisition step for obtaining carbon dioxide, a carbon material acquisition step for obtaining carbon material for use in water or gas treatment, and a plasma treatment step for modifying the carbon dioxide into carbon monoxide by applying plasma treatment in the presence of the aforementioned carbon material; a carbon dioxide modification system (200) includes: a carbon dioxide acquisition unit (5) for obtaining carbon dioxide, a carbon material acquisition unit (6) for obtaining carbon material for use in water or gas treatment, and a plasma modification control unit (7) for modifying the carbon dioxide into carbon monoxide by applying plasma treatment in the presence of the aforementioned carbon material.

Description

Technical Field

[0001] This disclosure relates to carbon dioxide reforming methods and systems. Prior Technology

[0002] In order to achieve carbon neutrality, the demand for gas reforming technology that converts carbon dioxide (CO2) recovered from waste gas and the atmosphere into high-value-added substances is increasing. Currently, research is being conducted on a technology that uses electric discharge plasma to reduce carbon dioxide into carbon monoxide (CO).

[0003] Patent Document 1 discloses a method for converting CO2 into CO, which involves supplying CO2 gas to a plasma jet generator, igniting a plasma in the CO2 gas to generate a plasma jet containing CO and O, introducing the plasma jet into a carbon reaction chamber containing carbon precursor particles to combine O and C to generate CO, removing the generated gas composed of CO and CO2 from the carbon reaction chamber, recovering at least a portion of the generated gas, and supplying it to the aforementioned plasma jet generator or a second plasma jet generator. However, the efficient conversion of CO2 into CO via plasma necessitates the supply of an external carbon source, which raises concerns about increased processing costs and carbon source consumption.

[0004] On the other hand, with increasingly stringent PFAS regulations, the increase in waste activated carbon used for adsorbing and removing PFAS from water and waste gas, as well as its treatment methods, have become issues. Among organofluorine compounds, perfluoroalkyl compounds and polyfluoroalkyl compounds are collectively referred to as PFAS. [Preliminary Technology Documents] [Patent Literature]

[0005] [Patent Document 1] International Patent No. WO2023 / 222708 Summary of the Invention

[0006] [The problem the invention aims to solve] Carbon materials such as waste activated carbon used for water treatment and waste gas treatment to remove PFAS can decompose and render harmless the adsorbed substances by burning them at high temperatures. However, this process involves burning carbon to produce CO2, which is then released into the atmosphere.

[0007] This disclosure was made to solve the problems mentioned above, and its purpose is to provide a carbon dioxide reforming method and system that effectively reforms carbon dioxide into carbon monoxide while reforming the adsorbed substances on carbon materials used for water treatment and waste gas treatment to reduce their harmfulness, and further enables the carbon materials to be recycled. [Methods used to solve problems]

[0008] The carbon dioxide modification method disclosed herein is characterized by comprising the following steps: a carbon dioxide acquisition step for obtaining carbon dioxide; a carbon material acquisition step for obtaining carbon material for use in the treatment of water or gas; and a plasma treatment step for modifying the aforementioned carbon dioxide into carbon monoxide by subjecting the aforementioned carbon material to plasma treatment in the presence of the aforementioned carbon material.

[0009] The carbon dioxide reforming system disclosed herein is characterized by comprising: a carbon dioxide obtaining unit for obtaining carbon dioxide; A carbon material acquisition unit that acquires carbon materials for use in the treatment of water or gas; and a plasma modification control unit that modifies carbon dioxide into carbon monoxide by applying plasma treatment in the presence of the aforementioned carbon material. [Invention Benefits]

[0010] According to this disclosure, not only can carbon dioxide be effectively converted into carbon monoxide, but also the adsorbed substances on carbon materials used for water treatment and waste gas treatment can be converted to reduce their harmfulness, and further enable the carbon materials to be recycled. Simple Explanation of the Diagram

[0011] Figure 1 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus using the carbon dioxide reforming method of Embodiment 1. Figure 2 shows a flowchart of the carbon dioxide reforming steps in Embodiment 1. Figure 3 is a cross-sectional view of a carbon dioxide reforming apparatus used to illustrate the carbon dioxide reforming method of Embodiment 2. Figure 4 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus using the carbon dioxide reforming method of Embodiment 3. Figure 5 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus using the carbon dioxide reforming method of Embodiment 4. Figure 6 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus using the carbon dioxide reforming method of Embodiment 5. Figure 7 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus using the carbon dioxide reforming method of Embodiment 6. Figure 8 shows a block diagram of the structure of a carbon dioxide reforming system using the carbon dioxide reforming method of Embodiment 7. Implementation

[0012] [The form in which the invention is carried out] Implementation Form 1. Figure 1 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 1.

[0013] As shown in Figure 1, the carbon dioxide reforming device 100 of Embodiment 1 consists of a processing container 1 with a carbon material supply port 1a and a carbon monoxide discharge port 1b, and a plasma generating unit 2 with a carbon dioxide inlet 2a and electrodes 2b and 2c for generating discharge plasma P.

[0014] The processing container 1 is supplied with carbon material C through the carbon material supply port 1a. In the presence of carbon material C, CO2 is reduced, and the modified CO is discharged through the carbon monoxide discharge port 1b. The processing container 1 is equipped with a plasma generation unit 2 so that the supplied carbon material C comes into contact with the discharge plasma P.

[0015] Electrodes 2b and 2c of the plasma generating unit 2 are disposed on a frame 2d made of insulating material so that the carbon material C supplied to the processing container 1 comes into contact with the generated discharge plasma P, and a voltage is supplied between electrodes 2b and 2c by a power source 2e.

[0016] The plasma generation unit 2 is provided with a carbon dioxide inlet 2a for introducing CO2. In Figure 1, the carbon dioxide inlet 2a is provided so that the introduced CO2 forms a spiral shape, that is, a plasma flow rotating in a circumferential direction, but it is not limited to this. Furthermore, when the carbon dioxide inlet 2a is provided so that the introduced CO2 forms a spiral plasma flow, the plasma flow can be stably maintained on the inner wall of the frame away from the plasma generation unit, thus improving the contact efficiency between CO2 gas and plasma, and improving the conversion rate of CO2 to CO.

[0017] Next, the carbon dioxide reforming method of Embodiment 1 will be explained using Figure 2. Figure 2 shows a flowchart of the reforming steps of the carbon dioxide reforming method of Embodiment 1.

[0018] First, in the CO2 acquisition step (S201 in Figure 2), a CO2-containing gas for modification is obtained. The CO2 source is not limited; for example, waste gas from iron or chemical plants, boiler exhaust gas, exhaust gas from thermal power plants, or CO2 recovered from the atmosphere can be used.

[0019] A higher CO2 concentration is desirable, ideally above 80%. Low CO2 concentrations can hinder CO2 reforming and reduce efficiency due to the presence of other gases (e.g., O2, N2) in contact with the plasma. Furthermore, undesirable byproducts such as NOx may be generated.

[0020] Next, in the carbon material acquisition step (S202 in Figure 2), carbon material C is obtained for use in treatment facilities that process water or gas. For example, this relates to activated carbon used in drinking water treatment plants to adsorb and remove harmful substances (PFAS, pharmaceuticals, organohalogen compounds, etc.) from water. It also relates to activated carbon used to adsorb and remove VOCs (Volatile Organic Compounds) from factory exhaust gases.

[0021] Carbon material C can be any carbon-containing material that can be used for water or gas treatment, such as granular activated carbon, powdered activated carbon, graphite, charcoal, coal or biochar, etc.

[0022] Finally, in the plasma treatment step (S203 in Figure 2), a discharge plasma is formed in CO2 gas in the presence of carbon material C. Types of discharge plasma include, but are not limited to, DC arc, AC arc, slip arc discharge, inductively coupled plasma, and microwave plasma. The plasma must be capable of ionization in CO2 gas.

[0023] CO2 is converted into CO by discharge plasma through the following reaction (1). Where e is an electron. CO2 + e → CO + O + e ···(1)

[0024] Furthermore, CO2 in equation (1) is not necessarily in the ground state; it may also exist in an electronically excited state, a vibrationally excited state, or a rotationally excited state. Therefore, equation (1) includes not only the direct dissociation reaction of CO2 in the ground state but also the staged dissociation reaction via the excited state.

[0025] The O (oxygen atom) generated by formula (1) comes into contact with carbon material and is transformed into CO by the following formula (2). O + C → CO ···(2)

[0026] Furthermore, a portion of the O produced by equation (1) becomes oxygen molecules through the reaction of the following equation (3). O + O → O2 ···(3)

[0027] The O2 generated by formula (3) reacts with carbon materials at high temperature to produce CO through the following formula (4). O2 + 2C → 2CO ···(4)

[0028] Furthermore, at high temperature, CO2 reacts with carbon materials via the boudouard reaction to produce CO via the following equation (5). CO2 + C → 2CO ···(5)

[0029] According to the reactions in equations (1) to (5), CO2 can be efficiently reduced to CO by forming a CO2 plasma in the presence of carbon materials.

[0030] "Plasma treatment in the presence of carbon materials" refers to a state in which carbon materials are in direct contact with plasma, or a state in which active species (oxygen atoms, excited-state oxygen molecules, excited-state CO2, etc.) generated by plasma are in contact with carbon materials. The former involves placing carbon materials between the electrodes that generate the discharge plasma. The latter involves configuring the materials to form a torch-shaped discharge plasma, with the carbon materials in contact with the torch.

[0031] There are no restrictions on the type of electricity used to generate plasma, but electricity from natural energy sources such as sunlight and wind is preferred. It can operate by reducing CO2 to CO when generating surplus electricity, depending on weather conditions.

[0032] The generated CO can be used as a raw material for methanol, SAF (Sustainable Aviation Fuel), resin materials, and as a reducing agent in iron production. Its applications are not limited to these.

[0033] Substances adsorbed onto carbon materials are modified through contact with plasma, by reactions caused by charged particles, reactions with active species (free radicals), and the effects of heat and light. In this way, they become CO, CO2, inorganic substances, etc., thus reducing their harmfulness or rendering them harmless.

[0034] Thus, through the modification steps from S201 to S203, CO2 can be modified into CO. Plasma modification of CO2 in the presence of carbon materials not only increases the conversion rate to CO but also enables the resource recovery of used carbon materials that are typically subjected to combustion (C+O2→CO2) (C+O→CO, C+CO2→2CO), reducing CO2 emissions while allowing the carbon materials to be recycled as CO. Furthermore, the harmfulness of the adsorbed substances on the carbon materials is reduced through plasma modification.

[0035] As described above, the carbon dioxide modification method according to Embodiment 1 includes: a carbon dioxide acquisition step for obtaining carbon dioxide; a carbon material acquisition step for obtaining carbon material C for use in water or gas treatment; and a plasma treatment step for subjecting the aforementioned carbon dioxide to plasma treatment in the presence of carbon material C to modify it into carbon monoxide. Therefore, CO2 can be modified into CO. Performing plasma modification of CO2 in the presence of carbon material not only increases the conversion rate to CO, but also enables the resource recovery of used carbon material (C+O2→CO2) that is normally subjected to combustion treatment (C+O→CO, C+CO2→2CO), reducing CO2 emissions while allowing the carbon material to be recycled as CO. Furthermore, the harmfulness of the adsorbed substances on the carbon material is reduced through plasma modification.

[0036] Implementation Form 2. In Embodiment 2, the case of using activated carbon that adsorbs PFAS-containing organic fluorine compounds as carbon material C will be explained.

[0037] Figure 3 is a cross-sectional view of a carbon dioxide reforming apparatus 100 used to illustrate the carbon dioxide reforming method of Embodiment 2.

[0038] As shown in Figure 3, in the carbon dioxide modification method of embodiment 2, in the carbon material acquisition step (S202 in Figure 2), activated carbon that adsorbs PFAS-containing organic fluorine compounds is obtained. In the plasma treatment step (S203 in Figure 2), the supplied CO2 is mixed with water vapor (H2O) for plasma treatment.

[0039] Other methods for carbon dioxide reforming in Embodiment 2 and the basic structure of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method are the same as those for the carbon dioxide reforming method and the carbon dioxide reforming apparatus 100 using Embodiment 1. The corresponding parts are given the same symbols and their descriptions are omitted.

[0040] Therefore, when the adsorbed substance contains fluorine (F), PFAS can recover hydrogen fluoride (HF) through decomposition. The water vapor concentration can be arbitrarily determined based on the amount of adsorbed substance and the electricity generated by the plasma. If the water vapor concentration is too low, the conversion rate to HF decreases; conversely, if the water vapor concentration is too high, the conversion efficiency of CO2 to CO decreases. Generally speaking, adding 1-20% water vapor to CO2 gas is preferable.

[0041] As described above, according to the carbon dioxide reforming method of this embodiment 2, since the carbon material obtained in the carbon material acquisition step is activated carbon that adsorbs organic fluorine compounds, in the plasma treatment step, the aforementioned carbon dioxide is subjected to plasma treatment in the presence of water, so that the adsorbed organic fluorine compounds can be decomposed and F can be recovered as HF.

[0042] When PFAS adsorbs substances containing phosphorus (F), it decomposes upon contact with the discharge plasma (P). In the presence of water vapor, the F forms high-frequency electrical discharge (HF). This allows for the re-formation of cross-links (CF) bonds, preventing leakage to the outside. HF is soluble in water or reacts with calcium, making it easily recoverable.

[0043] Furthermore, in embodiment 2 described above, when the supplied CO2 is mixed with water vapor and supplied to plasma treatment, and the carbon material C to be treated is wet and contains moisture (e.g., activated carbon used for water treatment) and supplied in an undried state, the same effect can be obtained even if it is not mixed with water vapor.

[0044] Implementation Form 3. In Embodiment 3, the case of recovering F using a fluorine capture unit will be explained.

[0045] Figure 4 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 3.

[0046] As shown in Figure 4, the carbon dioxide reforming apparatus 100 of Embodiment 3 has a fluorine capture unit 3 at the carbon monoxide discharge outlet 1b. The fluorine capture unit 3 contains at least calcium (Ca), for example, calcium hydroxide (Ca(OH)2) can be used to capture F as calcium fluoride (CaF2).

[0047] The other components of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 3 are the same as those of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 1, and the corresponding parts are given the same symbols and their descriptions are omitted.

[0048] Thus, the gas converted to CO can be prevented from leaking to the outside by capturing the F contained in the adsorbed substance through the fluorine trapping section 3, which contains at least Ca. CaF2 is a valuable substance that can be used in optical lenses, etc. According to this embodiment, in addition to the conversion of CO2 and the recycling of carbon materials, it can remove harmful organic fluorine compounds and produce and recycle valuable substances such as CaF2.

[0049] Furthermore, upstream of the fluoride capture section 3, a gas containing at least water vapor can also be mixed. In this case, the fluoride compounds produced by the decomposition of the adsorbed substance are converted into HF, which increases the reactivity with Ca(OH)2, allowing for more reliable removal by the fluoride capture section 3.

[0050] As described above, according to the carbon dioxide reforming method of Embodiment 3, since carbon monoxide is passed through the Ca-containing fluorine capture unit 3 and discharged in the plasma treatment step, it is possible to capture the F contained in the adsorbed substance and suppress leakage to the outside. In addition, it can also remove harmful organic fluorine compounds and produce and recover valuable substances such as CaF2.

[0051] Implementation Form 4. In Embodiment 4, the case of using the heat generated by the modification reaction to preheat the carbon material C is explained.

[0052] Figure 5 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 4.

[0053] As shown in Figure 5, the carbon dioxide reforming apparatus 100 of Embodiment 4 includes a heat exchange section 4 that uses waste heat from the reforming reaction that produces CO to preheat the supplied carbon material C.

[0054] The other components of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 4 are the same as those of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 1, and the corresponding parts are given the same symbols and their descriptions are omitted.

[0055] This reduces the amount of electricity required for plasma treatment. Furthermore, in the case of activated carbon used in water treatment, preheating can reduce the moisture content, thus adjusting it to a suitable moisture level for water modification.

[0056] As described above, according to the carbon dioxide reforming method of Embodiment 4, since the waste heat from the reaction that reforms to carbon monoxide is used in the plasma treatment step to preheat the carbon material obtained in the carbon material acquisition step, the amount of electricity input to the plasma can be reduced. Furthermore, in the case of activated carbon used for water treatment, the water content can be reduced by preheating, thus adjusting it to a suitable water content for reforming.

[0057] Implementation Form 5. In Implementation Form 5, the case of using waste heat from the reforming reaction to preheat CO2 is explained.

[0058] Figure 6 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 5.

[0059] As shown in Figure 6, the carbon dioxide reforming apparatus 100 of Embodiment 5 includes a heat exchange section 4 that uses waste heat from the reforming reaction that produces CO to preheat the supplied CO2.

[0060] The other components of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 5 are the same as those of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 1, and the corresponding parts are given the same symbols and their descriptions are omitted.

[0061] This reduces the amount of electricity required to power the plasma.

[0062] As described above, according to the carbon dioxide reforming method of this embodiment 5, since the waste heat from the reaction of reforming into carbon monoxide is used in the plasma treatment step to preheat the carbon dioxide obtained in the carbon dioxide acquisition step, the amount of electricity input to the plasma can be reduced.

[0063] Implementation Form 6. In Embodiment 6, the case in which only a portion (surface layer) of carbon material C is reacted by the discharge plasma P, and only a portion (surface layer) of the reacted carbon material is recovered, will be explained.

[0064] Figure 7 shows a cross-sectional view of the structure of a carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 6.

[0065] As shown in Figure 7, the carbon dioxide reforming apparatus 100 of Embodiment 5 includes a carbon material discharge outlet 1c. A carbon monoxide discharge outlet 1b and a carbon material discharge control unit 9 are provided at the carbon material discharge outlet 1c. The carbon material discharge control unit 9 adjusts the discharge rate of the carbon material to ensure that the carbon material C remains in the processing container for a predetermined time.

[0066] The other components of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 6 are the same as those of the carbon dioxide reforming apparatus 100 using the carbon dioxide reforming method of Embodiment 1, and the corresponding parts are given the same symbols and their descriptions are omitted.

[0067] The carbon material C does not need to react entirely in the discharge plasma P; only a portion of it needs to react. Specifically, by appropriately setting the contact time with the discharge plasma P, only a portion (the surface layer) of the regenerated carbon material CR that has undergone reaction can be recovered. This decomposes and removes substances adsorbed near the surface of the carbon material C. Therefore, the amount of activated carbon is reduced, but the adsorption performance can be restored for reuse.

[0068] In most cases, the adsorbed substances in water or gas treatment are adsorbed near the surface of the carbon material. Therefore, by treating the area near the surface of the carbon material with plasma, the adsorbed substances can be modified. In this case, the carbon material with the surface removed can be reused for water or gas treatment. In this embodiment 6, by controlling the time the carbon material remains in the treatment container, that is, by controlling the time of contact and treatment with the plasma, only the necessary amount near the surface of the carbon material can be treated, thereby suppressing unnecessary carbon material consumption and simultaneously modifying the adsorbed substances.

[0069] Furthermore, by shutting off the carbon material discharge control unit 9, the waste activated carbon can be completely recycled. Therefore, the regeneration and recycling of waste activated carbon can be carried out arbitrarily within the same device.

[0070] As described above, according to the carbon dioxide reforming method of this embodiment 6, since the residence time of carbon material C is controlled by carbon material discharge control unit 9 in the plasma treatment step, carbon material CR that has reacted with the surface layer after plasma treatment is discharged, only the necessary amount near the surface of the carbon material can be treated, thereby suppressing unnecessary carbon material consumption and reforming the adsorbed substance at the same time.

[0071] Implementation Form 7. In Implementation Form 7, a carbon dioxide reforming system using a carbon dioxide reforming method is described.

[0072] Figure 8 shows a block diagram of the structure of a carbon dioxide reforming apparatus 200 using the carbon dioxide reforming method of Embodiment 7.

[0073] As shown in Figure 8, the carbon dioxide reforming system 200 of Embodiment 7 consists of a carbon dioxide acquisition unit 5, a carbon material acquisition unit 6, and a plasma reforming control unit 7.

[0074] The carbon dioxide acquisition unit 5 uses alkaline solutions such as amines to absorb CO2, separates CO2 using polymer membranes or porous membranes, or adsorbs CO2 using solid adsorbents such as zeolites or MOFs (Metal Organic Frameworks) to obtain CO2.

[0075] The carbon material acquisition unit 6 acquires carbon materials for use in water or gas treatment facilities for treating gases or water. The carbon material acquisition unit 6 may also have functions such as sorting the size of the carbon materials and adjusting the amount of water adsorbed.

[0076] The plasma modification control unit 7 comprises a carbon dioxide supply unit 71, a carbon material supply unit 72, a processing monitoring unit 73, a plasma processing unit 74, and a gas measurement unit 75. The plasma modification control unit 7 controls the carbon dioxide supply unit 71 and the carbon material supply unit 72 to achieve, for example, an optimal ratio between the CO2 supply and the carbon material supply.

[0077] The carbon dioxide supply unit 71 supplies CO2 obtained by the carbon dioxide acquisition unit 5 to the plasma processing unit 74 at a predetermined supply rate. The carbon material supply unit 72 supplies the necessary amount of carbon material to the plasma processing unit 74. The processing monitoring unit 73 monitors, for example, the gas temperature and carbon material temperature of the plasma processing unit 74. It can also monitor the residual amount of carbon material in the plasma processing unit 74. The plasma processing unit 74 reacts the CO2 supplied from the carbon dioxide supply unit 71 with the carbon material supplied from the carbon material supply unit 72 to generate CO. The gas measuring unit 75 measures at least one of the CO concentration, CO2 concentration, and O2 concentration in the gas discharged from the plasma processing unit 74. It also measures the concentration of trace components in the gas discharged from the plasma processing unit 74. The carbon monoxide utilization unit 8 utilizes the CO generated in the plasma processing unit 74.

[0078] Ideally, CO2 and C in the plasma treatment unit 74 are consumed in equal molar amounts (CO2 + C → 2CO ··· (5)). In this case, the carbon dioxide supply unit 71 and the carbon material supply unit 72 are controlled to supply CO2 and C in equal molar amounts.

[0079] On the other hand, in the plasma processing unit 74, there is no need to convert all CO2 into CO, and CO2 flows out directly. In this case, the consumption of carbon materials is calculated from the concentration of at least one of CO, CO2, and O2 measured by the gas measuring unit 75. By controlling at least one of the CO2 supply and the carbon material supply, the CO2 supply and the carbon material supply can be supplied in the most suitable ratio.

[0080] Specifically, in addition to the above equation (5), the reaction of equation (6) also occurs. 2CO2→2CO+O2 ···(6)

[0081] The proportion of CO2 consumed in Equation (6) is estimated from the O2 concentration. The amount of C consumed can also be estimated by measuring the decrease in CO2 concentration through the plasma treatment unit 74. Based on this estimation, the carbon material supply unit 72 can supply the necessary amount of carbon material to the plasma treatment unit 74.

[0082] Furthermore, the processing monitoring unit 73 monitors the residual amount of carbon material in the plasma processing unit 74, and can control the supply of carbon material from the carbon material supply unit 72 when the residual amount falls below a predetermined value. It also monitors the rate of carbon material reduction in the plasma processing unit 74 to adjust the carbon material supply rate of the carbon material supply unit 72 to avoid carbon material shortage. The residual amount and reduction rate of the carbon material can be measured using optical methods such as image analysis, light transmission, and reflection.

[0083] The processing monitoring unit 73 measures the gas temperature or carbon material temperature of the plasma processing unit 74, and the plasma modification control unit 7 controls these temperatures to keep them within a predetermined temperature range. For example, the plasma modification control unit 7 adjusts the power supplied to the plasma in the plasma processing unit 74. Alternatively, the plasma modification control unit 7 adjusts the temperature by regulating the amount of CO2 and carbon material supplied to the plasma processing unit 74.

[0084] The gas temperature and carbon material temperature are preferably above 850°C, and even more preferably above 1000°C. This corresponds to the decomposition temperature of PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid), representative substances of PFAS. Furthermore, most organic compounds are also decomposed at this temperature. In addition, the reaction of CO2 directly with carbon materials to produce CO (the Boudoir reaction) occurs significantly above around 1000°C. Therefore, by setting the temperature above 1000°C, not only can PFAS be decomposed, but the conversion from CO2 to CO can also be effectively carried out.

[0085] On the other hand, excessive temperature rise can cause unnecessary power consumption, material degradation in the plasma processing unit 74, and increased costs associated with the cooling system. Therefore, gas and carbon material temperatures are preferably below 3000°C, and even better below 2000°C.

[0086] Examples of temperature measurement methods include estimating the temperature using the emission spectrum of the plasma treatment unit 74, measuring the temperature of the carbon material using a radiation thermometer, or estimating the temperature of the reaction field from the ambient temperature. However, these methods are not limited to any method that can measure the temperature of the gas or the carbon material.

[0087] Furthermore, the carbon material does not need to be completely reacted in the plasma treatment unit 74; only a portion of it can be reacted. Specifically, by appropriately setting the residence time in the plasma treatment unit 74, only a portion (the surface layer) of the reacted carbon material can be recovered. This decomposes and removes substances adsorbed near the surface of the carbon material. Therefore, the amount of activated carbon is reduced, but the adsorption performance can be restored for reuse.

[0088] Additionally, a wet scrubber can be installed downstream of the plasma treatment unit 74 to treat the gas flowing out of the plasma treatment unit 74. Fluorine in the PFAS decomposed in the plasma treatment unit 74 is dissolved into the liquid by the wet scrubber and recovered as HF. Furthermore, it can remove nitrogen oxides and sulfur oxides, as well as impurities (nitrogen and sulfur components) contained in the CO2 supplied to the plasma treatment unit 74.

[0089] As described above, the carbon dioxide reforming system according to Embodiment 7, having a carbon dioxide acquisition unit 5 for acquiring carbon dioxide; a carbon material acquisition unit 6 for acquiring carbon materials used in water or gas treatment; and a plasma reforming control unit 7 for applying plasma treatment to the aforementioned carbon dioxide to reform it into carbon monoxide in the presence of the aforementioned carbon material, can reform CO2 into CO. Performing plasma reforming of CO2 in the presence of carbon material not only improves the conversion rate to CO but also enables the resource recovery of used carbon materials (C+O2→CO2) that are normally subjected to combustion treatment (C+O→CO, C+CO2→2CO), reducing CO2 emissions while allowing the carbon material to be recycled as CO. Furthermore, the harmfulness of the adsorbed substances adsorbed on the carbon material is reduced through plasma reforming.

[0090] Although this application describes various exemplary embodiments and examples, the various features, forms, and functions described in one or more embodiments are not limited to the application of a particular embodiment, and can be applied to the embodiment alone or in various combinations. Therefore, numerous variations not illustrated are also presupposed within the technical scope disclosed in this specification. For example, this includes variations, additions, or omissions of at least one constituent element; further, the extraction of at least one constituent element and its combination with constituent elements of other embodiments.

[0091] 5: Carbon Dioxide Acquisition Department 6: Carbon Materials Acquisition Department 7: Plasma Modification Control Department 200: Carbon Dioxide Reforming System

Claims

1. A method for carbon dioxide reforming, comprising: The carbon dioxide obtaining step; the carbon material obtaining step for obtaining carbon material for the treatment of water or gas; and the plasma treatment step for modifying the aforementioned carbon dioxide into carbon monoxide by subjecting it to plasma treatment in the presence of the aforementioned carbon material, wherein the aforementioned carbon material is activated carbon that adsorbs the adsorbed substance in the aforementioned treatment, and the aforementioned adsorbed substance is an organic fluorine compound.

2. The carbon dioxide modification method as described in claim 1, wherein the aforementioned plasma treatment step involves applying plasma treatment to the aforementioned carbon dioxide in the presence of water.

3. The carbon dioxide reforming method as described in claim 1, wherein the aforementioned plasma treatment step involves the aforementioned carbon monoxide being discharged through a fluorine capture unit.

4. The carbon dioxide reforming method as described in claim 2, wherein the aforementioned plasma treatment step involves the aforementioned carbon monoxide being discharged through a fluorine capture unit.

5. The carbon dioxide reforming method as described in claim 3, wherein the aforementioned fluorine capture section captures the fluorine of the aforementioned organofluorine compound by means of calcium.

6. The carbon dioxide reforming method as described in claim 4, wherein the aforementioned fluorine capture section captures the fluorine of the aforementioned organofluorine compound by means of calcium.

7. The carbon dioxide reforming method as described in claim 1, wherein the aforementioned plasma treatment step is performed by controlling the residence time of the aforementioned carbon material by a carbon material discharge control unit, and discharging the aforementioned carbon material that has undergone the aforementioned plasma treatment and surface reaction.

8. The carbon dioxide reforming method described in any one of claims 1 to 7, wherein the carbon material obtained in the aforementioned carbon material obtaining step is preheated by the waste heat from the aforementioned reforming reaction to carbon monoxide in the aforementioned plasma treatment step.

9. The carbon dioxide reforming method described in any one of claims 1 to 7, wherein the carbon dioxide obtained in the aforementioned carbon dioxide obtaining step is preheated by the waste heat from the aforementioned reaction that reforms the carbon dioxide into carbon monoxide in the aforementioned plasma treatment step.

10. The carbon dioxide reforming method as described in claim 8, wherein the carbon dioxide obtained in the aforementioned carbon dioxide obtaining step is preheated by the waste heat from the aforementioned reforming reaction to carbon monoxide in the aforementioned plasma treatment step.

11. A carbon dioxide modification system comprising: a carbon dioxide acquisition unit for acquiring carbon dioxide; a carbon material acquisition unit for acquiring carbon material for processing water or gas; and a plasma modification control unit for modifying the carbon dioxide into carbon monoxide by subjecting it to plasma treatment in the presence of the aforementioned carbon material, wherein the aforementioned carbon material is activated carbon that adsorbs an adsorbed substance in the aforementioned treatment, and the adsorbed substance is an organofluorine compound.

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