Carbon dioxide reforming method

Abstract

The carbon dioxide reforming method of the present disclosure includes a carbon dioxide acquisition step of acquiring carbon dioxide, a carbon material acquisition step of acquiring a carbon material used in the treatment of water or gas, and a plasma treatment step of reforming the carbon dioxide into carbon monoxide by subjecting the carbon dioxide to plasma treatment in the presence of the carbon material, and the carbon dioxide reforming system (200) includes a carbon dioxide acquisition unit (5) that acquires carbon dioxide, a carbon material acquisition unit (6) that acquires the carbon material used in the treatment of water or gas, and a plasma reforming control unit (7) that reforms the carbon dioxide into carbon monoxide by subjecting the carbon dioxide to plasma treatment in the presence of the carbon material.

Description

[Technical Field]

[0001] The present disclosure relates to a carbon dioxide reforming method. law It is related to. [Background technology]

[0002] In order to achieve carbon neutrality, there is a growing demand for gas reforming technology that reforms carbon dioxide (CO2) captured from exhaust gases and the atmosphere into high-value-added substances, and research is underway into technology that reduces carbon dioxide to carbon monoxide (CO) using discharge plasma.

[0003] Patent Document 1 discloses a method for reforming CO2 into CO, which involves supplying CO2 gas to a plasma jet generator and igniting 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 donor particles to combine O and C to generate CO, extracting a product gas consisting of CO and CO2 from the carbon reaction chamber, and recycling at least a portion of the product gas to supply to the plasma jet generator or a second plasma jet generator. In order to convert CO2 to CO efficiently using plasma, it is necessary to supply a carbon source from an external source, which poses issues of increased processing costs and carbon source consumption.

[0004] On the other hand, with the strengthening of PFAS regulations, the increase in waste activated carbon used to adsorb and remove PFAS from water and exhaust gases and its disposal method have become issues. Among organic fluorine compounds, perfluoroalkyl compounds and polyfluoroalkyl compounds are collectively referred to as PFAS. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Patent Publication No. WO2023 / 222708 Summary of the Invention [Problem to be solved by the invention]

[0006] Carbon materials such as waste activated carbon used in water treatment and exhaust gas treatment, including PFAS removal, are incinerated at high temperatures to decompose and neutralize the adsorbed substances, but this process causes the carbon to burn and be released into the atmosphere as CO2, which is a problem.

[0007] The present disclosure has been made to solve the above-mentioned problems, and provides a carbon dioxide reforming method that efficiently reforms carbon dioxide into carbon monoxide, reforms adsorbates adsorbed on carbon materials used in water treatment and exhaust gas treatment to reduce their harmfulness, and further recycles the carbon materials. law The purpose is to provide the following. [Means for solving the problem]

[0008] The carbon dioxide reforming method according to the present disclosure is characterized by comprising a carbon dioxide obtaining step of obtaining carbon dioxide, a carbon material obtaining step of obtaining a carbon material used in the treatment of water or gas, and a plasma treatment step of reforming the carbon dioxide into carbon monoxide by subjecting the carbon dioxide to plasma treatment in the presence of the carbon material. [Effects of the Invention]

[0010] According to the present disclosure, not only can carbon dioxide be efficiently reformed into carbon monoxide, but also adsorbates adsorbed onto carbon materials used in water treatment and exhaust gas treatment can be reformed to reduce their harmfulness, and the carbon materials can be recycled. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing the configuration of a carbon dioxide reforming device that uses a carbon dioxide reforming method according to a first embodiment. [Figure 2] FIG. 3 is a flowchart showing the reforming steps of the carbon dioxide reforming method according to the first embodiment. [Figure 3]FIG. 10 is a cross-sectional view illustrating a carbon dioxide reforming device that uses a carbon dioxide reforming method according to a second embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing the configuration of a carbon dioxide reforming device that uses a carbon dioxide reforming method according to a third embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing the configuration of a carbon dioxide reforming device that uses a carbon dioxide reforming method according to a fourth embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing the configuration of a carbon dioxide reforming device that uses a carbon dioxide reforming method according to a fifth embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration of a carbon dioxide reforming device that uses a carbon dioxide reforming method according to a sixth embodiment. [Figure 8] FIG. 11 is a block diagram showing the configuration of a carbon dioxide reforming system that uses a carbon dioxide reforming method according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 FIG. 1 is a cross-sectional view showing the configuration of a carbon dioxide reforming device 100 that uses a carbon dioxide reforming method according to the first embodiment.

[0013] As shown in FIG. 1, the carbon dioxide reforming apparatus 100 of the first embodiment comprises a processing vessel 1 provided with a carbon material supply port 1a and a carbon monoxide discharge port 1b, and a plasma generating unit 2 that generates a discharge plasma P provided with a carbon dioxide inlet 2a and electrodes 2b and 2c.

[0014] A carbon material C is supplied to the treatment vessel 1 through a carbon material supply port 1a, CO2 is reduced in the presence of the carbon material C, and the reformed CO is discharged through a carbon monoxide discharge port 1b. A plasma generation unit 2 is disposed in the treatment vessel 1 so that a discharge plasma P contacts the supplied carbon material C.

[0015] The plasma generating unit 2 has electrodes 2b and 2c mounted in a housing 2d made of an insulating material so that the generated discharge plasma P comes into contact with the carbon material C supplied to the processing vessel 1, and a voltage is supplied between the electrodes 2b and 2c by a power source 2e.

[0016] The plasma generating unit 2 is provided with a carbon dioxide inlet 2a for introducing CO2. In Fig. 1, the carbon dioxide inlet 2a is provided so that the introduced CO2 forms a spiral plasma flow, i.e., a plasma flow that swirls in the circumferential direction, but this is not limited to this. Note that if the carbon dioxide inlet 2a is provided so that the introduced CO2 forms a spiral plasma flow, the plasma flow is maintained stably away from the inner wall of the housing of the plasma generating unit, which increases the contact efficiency between the CO2 gas and plasma and has the effect of improving the conversion rate of reforming CO2 to CO.

[0017] Next, the carbon dioxide reforming method according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a flow chart showing the reforming steps of the carbon dioxide reforming method according to the first embodiment.

[0018] First, in the CO2 acquisition step (S201 in Figure 2), a gas containing CO2 to be reformed is acquired. There are no restrictions on the CO2 source, but it can be, for example, exhaust gas from steel or chemical plants, boiler exhaust gas, exhaust gas from thermal power plants, or CO2 captured from the atmosphere.

[0019] The higher the CO2 concentration, the more desirable it is, with 80% or more being preferable. If the CO2 concentration is low, the mixed gases (e.g., O2, N2) will come into contact with the plasma and inhibit the CO2 reforming reaction, reducing efficiency. X This produces undesirable by-products such as

[0020] Next, in the carbon material acquisition step (S202 in Figure 2), carbon material C used in a treatment facility that treats water or gas is acquired. For example, activated carbon used to adsorb and remove harmful substances in water (PFAS, pharmaceuticals, organohalogen compounds, etc.) at a water treatment plant is an example. Also, activated carbon used to adsorb and remove VOCs (volatile organic compounds) from factory exhaust gas is an example.

[0021] The carbon material C may 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.

[0022] Finally, in the plasma treatment step (S203 in FIG. 2), discharge plasma is formed in CO gas in the presence of carbon material C. Types of discharge plasma include, but are not limited to, DC arc, AC arc, gliding arc discharge, inductively coupled plasma, and microwave plasma. Any type of discharge plasma may be used as long as it can cause ionization in CO gas.

[0023] CO2 is reformed into CO by the discharge plasma through the reaction shown in formula (1) below, where e is an electron. CO2+ e → CO + O + e ···(1)

[0024] Note that the CO2 in equation (1) is not necessarily in the ground state; CO2 can also exist in electronically excited, vibrationally excited, or rotationally excited states. Therefore, equation (1) includes not only the direct dissociation reaction of CO2 in the ground state, but also stepwise dissociation reactions via excited states.

[0025] The O (oxygen atom) produced in formula (1) is reformed into CO by the reaction of formula (2) below when it comes into contact with a carbon material. O + C → CO (2)

[0026] In addition, a portion of the O produced in formula (1) becomes oxygen molecules in the reaction of formula (3) below. O + O → O2 (3)

[0027] The O2 produced in equation (3) reacts with the carbon material at high temperatures to produce CO in the reaction of equation (4) below. O2+ 2C → 2CO (4)

[0028] Furthermore, at high temperatures, CO2 reacts with the carbon material through the Boudouard reaction, producing CO in the reaction shown in equation (5) below. CO2 + C → 2CO (5)

[0029] By forming CO2 plasma in the presence of a carbon material through the reactions of formulas (1) to (5), CO2 can be efficiently reduced to CO.

[0030] "Plasma treatment in the presence of a carbon material" refers to a state in which the carbon material is in direct contact with the plasma, or a state in which activated species generated by the plasma (oxygen atoms, excited oxygen molecules, excited CO2, etc.) come into contact with the carbon material. In the former case, the carbon material is placed between electrodes that generate discharge plasma. In the latter case, the discharge plasma is formed in the shape of a torch, and the carbon material is placed so that it comes into contact with the torch.

[0031] Although there are no restrictions on the type of electricity used to generate plasma, it is preferable to use electricity derived from natural energy sources such as solar and wind power. When surplus electricity is generated due to weather conditions, the system can be operated to reduce CO2 to CO.

[0032] The generated CO can be used as a raw material for methanol, SAF (Sustainable Aviation Fuel), resin materials, etc., or as a reducing agent in steelmaking. Applications are not limited to these.

[0033] When substances adsorbed onto carbon materials come into contact with plasma, they are modified by reactions with charged particles, reactions with active species (radicals), heat, light, etc. This results in them becoming CO, CO2, inorganic substances, etc., and their harmfulness is reduced or rendered harmless.

[0034] In this way, the reforming steps from S201 to S203 can reform CO2 into CO, and by performing plasma reforming of CO2 in the presence of a carbon material, not only can the conversion rate to CO be improved, but used carbon materials that are normally incinerated (C + O2 → CO2) can be recycled (C + O → CO, C + CO2 → 2CO), reducing CO2 emissions and recycling the carbon material as CO. In addition, by reforming adsorbates adsorbed to the carbon material with plasma, their harmfulness is reduced.

[0035] As described above, the carbon dioxide reforming method according to the first embodiment includes a carbon dioxide obtaining step of obtaining carbon dioxide, a carbon material obtaining step of obtaining carbon material C used in the treatment of water or gas, and a plasma treatment step of reforming the carbon dioxide into carbon monoxide by performing plasma treatment on the carbon dioxide in the presence of carbon material C. This allows CO2 to be reformed into CO, and by performing plasma reforming of CO2 in the presence of the carbon material, not only can the conversion rate to CO be improved, but also used carbon material that is normally incinerated (C + O2 → CO2) can be recycled (C + O → CO, C + CO2 → 2CO), reducing CO2 emissions and recycling the carbon material as CO. Furthermore, by reforming adsorbates adsorbed to the carbon material by plasma, harmfulness is reduced.

[0036] Embodiment 2 In the second embodiment, a case will be described in which activated carbon having organic fluorine compounds including PFAS adsorbed thereon is used as the carbon material C.

[0037] FIG. 3 is a cross-sectional view illustrating a carbon dioxide reforming apparatus 100 that uses a carbon dioxide reforming method according to the second embodiment.

[0038] As shown in Figure 3, in the carbon dioxide reforming method of embodiment 2, when activated carbon that has adsorbed organic fluorine compounds including PFAS is obtained in the carbon material acquisition step (S202 in Figure 2), water vapor (H2O) is mixed with the supplied CO2 and subjected to plasma treatment in the plasma treatment step (S203 in Figure 2).

[0039] The basic configurations of other methods of the carbon dioxide reforming method of embodiment 2 and the carbon dioxide reforming device 100 using the carbon dioxide reforming method are the same as those of the carbon dioxide reforming device 100 using the carbon dioxide reforming method and carbon dioxide reforming device 100 of embodiment 1, and corresponding parts are given the same symbols and their descriptions are omitted.

[0040] As a result, when the adsorbed substance contains fluorine (F), such as PFAS, it is decomposed and recovered as hydrogen fluoride (HF). The water vapor concentration can be determined arbitrarily depending on the amount of adsorbed substance and the power required to generate plasma. If the water vapor concentration is too low, the conversion rate to HF decreases, while if the water vapor concentration is too high, the conversion efficiency of CO2 to CO decreases. Generally, it is appropriate to add 1 to 20% water vapor to CO2 gas.

[0041] As described above, according to the carbon dioxide reforming method of the second embodiment, if the carbon material obtained in the carbon material obtaining step is activated carbon that has adsorbed an organic fluorine compound, the carbon dioxide is subjected to plasma treatment in the presence of water in the plasma treatment step, and therefore the adsorbed organic fluorine compound can be decomposed, and F can be recovered as HF.

[0042] When the adsorbed substance contains F, such as PFAS, it comes into contact with the discharge plasma P and decomposes, and in the presence of water vapor, the F forms HF. This reforms the C—F bond, preventing leakage to the outside. HF can be easily recovered by dissolving it in water or reacting it with calcium.

[0043] In the above-mentioned second embodiment, water vapor is mixed with the supplied CO2 before the plasma treatment. However, if the carbon material C to be treated is wet and contains moisture (for example, activated carbon used in water treatment), the same effect can be obtained by providing it in an undried state, without mixing with water vapor.

[0044] Embodiment 3 In the third embodiment, a case where F is recovered using a fluorine trap unit will be described.

[0045] FIG. 4 is a cross-sectional view showing the configuration of a carbon dioxide reforming device 100 that uses a carbon dioxide reforming method according to the third embodiment.

[0046] 4, the carbon dioxide reformer 100 of the third embodiment is provided with a fluorine trapping unit 3 at the carbon monoxide outlet 1b. The fluorine trapping unit 3 contains at least calcium (Ca), for example, calcium hydroxide (Ca(OH)2), and traps F as calcium fluoride (CaF2).

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

[0048] In this way, the gas reformed into CO passes through the fluorine trap 3 containing at least Ca, thereby capturing F contained in the adsorbates and preventing leakage to the outside. CaF2 is a valuable material used in optical lenses and the like, and this embodiment not only converts CO2 and recycles carbon materials, but also has the effects of detoxifying harmful organic fluorine compounds and generating and recovering the valuable material CaF2.

[0049] It is also possible to mix a gas containing at least water vapor upstream of the fluorine trap section 3. In this case, the fluorine compounds produced by decomposition of the adsorbate are converted to HF, which improves the reactivity with Ca(OH)2 and allows them to be more reliably removed by the fluorine trap section 3.

[0050] As described above, according to the carbon dioxide reforming method of the third embodiment, in the plasma treatment step, carbon monoxide is discharged through the fluorine trap section 3 containing Ca, so that F contained in the adsorbed substance can be captured and its leakage to the outside can be suppressed. In addition, harmful organic fluorine compounds can be removed, and a valuable resource, CaF2, can be generated and recovered.

[0051] Embodiment 4 In the fourth embodiment, a case will be described in which the carbon material C is preheated using heat generated in the reforming reaction.

[0052] FIG. 5 is a cross-sectional view showing the configuration of a carbon dioxide reforming device 100 that uses a carbon dioxide reforming method according to the fourth embodiment.

[0053] As shown in FIG. 5, the carbon dioxide reformer 100 of the fourth embodiment includes a heat exchanger 4 that preheats the carbon material C to be supplied by using exhaust heat from the reforming reaction to CO.

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

[0055] This reduces the amount of power input to the plasma. Also, in the case of activated carbon used in water treatment, preheating can reduce the moisture content and adjust the moisture content to a level suitable for reforming.

[0056] As described above, according to the carbon dioxide reforming method of the fourth embodiment, in the plasma treatment step, the carbon material obtained in the carbon material obtaining step is preheated using the exhaust heat from the reforming reaction to carbon monoxide, so the power input to the plasma can be reduced. Also, in the case of activated carbon used in water treatment, the moisture content can be reduced by preheating, and the moisture content can be adjusted to a level suitable for reforming.

[0057] Embodiment 5. In the fifth embodiment, a case will be described in which CO2 is preheated using waste heat from the reforming reaction.

[0058] FIG. 6 is a cross-sectional view showing the configuration of a carbon dioxide reforming device 100 that uses a carbon dioxide reforming method according to a fifth embodiment.

[0059] As shown in FIG. 6, the carbon dioxide reformer 100 of the fifth embodiment includes a heat exchanger 4 that preheats the CO2 to be supplied using waste heat from the reforming reaction to CO.

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

[0061] This allows the power input to the plasma to be reduced.

[0062] As described above, according to the carbon dioxide reforming method of this fifth embodiment, the carbon dioxide acquired in the carbon dioxide acquisition step is preheated using the exhaust heat from the reforming reaction to carbon monoxide in the plasma treatment step, thereby making it possible to reduce the power input to the plasma.

[0063] Embodiment 6 In the sixth embodiment, a case will be described in which only a part (surface layer) of the carbon material C is reacted with the discharge plasma P, and the carbon material whose only part (surface layer) has reacted is recovered.

[0064] FIG. 7 is a cross-sectional view showing the configuration of a carbon dioxide reforming device 100 that uses a carbon dioxide reforming method according to a sixth embodiment.

[0065] 7, the carbon dioxide reforming apparatus 100 of the fifth embodiment includes a carbon material outlet 1c. The carbon material outlet 1c is provided with a carbon monoxide outlet 1b and a carbon material discharge control unit 9. The carbon material discharge control unit 9 adjusts the discharge rate of the carbon material C so that the carbon material C remains in the treatment vessel for a predetermined time.

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

[0067] The carbon material C does not necessarily have to be completely reacted with the discharge plasma P, and only a portion of it can be reacted. Specifically, by appropriately setting the contact time with the discharge plasma P, only a portion (surface layer) of the carbon material C can be reacted. R This allows the substances adsorbed near the surface of the carbon material C to be decomposed and removed. Although the amount of activated carbon decreases, the adsorption performance is restored and the carbon material can be reused.

[0068] In many cases, adsorbates are adsorbed near the surface of carbon materials during water or gas treatment. Therefore, by treating the surface area of ​​the carbon material with plasma, the adsorbates can be modified. In this case, the carbon material except for the surface area can be reused for water or gas treatment. In this sixth embodiment, by controlling the time the carbon material remains in the treatment vessel, i.e., the time it is treated in contact with plasma, it is possible to treat only the required amount of the surface area of ​​the carbon material, thereby suppressing the consumption of more carbon material than necessary and modifying the adsorbates.

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

[0070] As described above, according to the carbon dioxide reforming method of the sixth embodiment, in the plasma treatment step, the carbon material discharge control unit 9 controls the residence time of the carbon material C, and the carbon material C whose surface layer has been reacted by the plasma treatment is discharged. R Since the amount of carbon material discharged is limited to the amount required, it is possible to treat only the surface layer of the carbon material, suppress the consumption of carbon material more than necessary, and modify the adsorbed substance.

[0071] Embodiment 7 In the seventh embodiment, a carbon dioxide reforming system using a carbon dioxide reforming method will be described.

[0072] FIG. 8 is a block diagram showing the configuration of a carbon dioxide reforming system 200 that uses a carbon dioxide reforming method according to the seventh embodiment.

[0073] As shown in FIG. 8, the carbon dioxide reforming system 200 of the seventh embodiment comprises a carbon dioxide obtaining unit 5, a carbon material obtaining unit 6, and a plasma reforming control unit .

[0074] The carbon dioxide capture unit 5 captures CO2 by, for example, absorbing CO2 in an alkaline solution such as an amine, separating CO2 using a polymer membrane or a porous membrane, or adsorbing CO2 using a solid adsorbent such as zeolite or MOF (Metal Organic Frameworks).

[0075] The carbon material acquisition unit 6 acquires carbon materials used in the treatment of gas or water to be treated at a water or gas treatment facility. The carbon material acquisition unit 6 may have a function of sorting the size of the carbon material or adjusting the amount of adsorbed water, for example.

[0076] The plasma reforming control unit 7 is composed of a carbon dioxide supply unit 71, a carbon material supply unit 72, a process monitoring unit 73, a plasma processing unit 74, and a gas measurement unit 75. The plasma reforming control unit 7 controls the carbon dioxide supply unit 71 and the carbon material supply unit 72 so that the ratio of the CO2 supply amount to the carbon material supply amount is optimal, for example.

[0077] The carbon dioxide supply unit 71 supplies CO2 acquired by the carbon dioxide acquisition unit 5 to the plasma treatment unit 74 at a predetermined supply rate. The carbon material supply unit 72 supplies the required amount of carbon material to the plasma treatment unit 74. The process monitoring unit 73 monitors, for example, the gas temperature and the carbon material temperature in the plasma treatment unit 74. It may also monitor the remaining amount of carbon material in the plasma treatment unit 74. The plasma treatment 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 measurement unit 75 measures at least one of the CO concentration, CO2 concentration, and O2 concentration of the gas output from the plasma treatment unit 74. It also measures the concentrations of trace components in the gas output from the plasma treatment unit 74. The carbon monoxide utilization unit 8 utilizes the CO generated in the plasma treatment unit 74.

[0078] Under ideal conditions, equimolar amounts of CO2 and C are consumed in the plasma treatment unit 74 (CO2 + C → 2CO (5)). In this case, the carbon dioxide supply unit 71 and the carbon material supply unit 72 are controlled so that equimolar amounts of CO2 and C are supplied.

[0079] On the other hand, in the plasma treatment unit 74, not all of the CO2 is necessarily converted to CO, and some CO2 may escape as is. In this case, the consumption amount of the carbon material is calculated from the concentration of at least one of CO, CO2, and O2 measured by the gas measurement unit 75, and at least one of the CO2 supply amount and the carbon material supply amount is controlled to supply the CO2 supply amount and the carbon material supply amount at an optimal ratio.

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

[0081] Therefore, the consumption amount of C can be estimated by estimating the proportion of CO2 consumed from the O2 concentration using equation (6) and measuring the decrease in CO2 concentration passing through the plasma treatment unit 74. Based on this estimation, the carbon material supply unit 72 can supply the required amount of carbon material to the plasma treatment unit 74.

[0082] The process monitoring unit 73 can also monitor the remaining amount of carbon material in the plasma processing unit 74, and when the remaining amount falls below a predetermined value, control the supply of carbon material from the carbon material supply unit 72. Alternatively, the process monitoring unit 73 can monitor the rate at which the carbon material in the plasma processing unit 74 decreases, and adjust the rate at which the carbon material is supplied from the carbon material supply unit 72 so that the carbon material does not run short. The remaining amount and rate at which the carbon material decreases can be measured using optical techniques such as image analysis, light transmission, and reflection.

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

[0084] The gas temperature and carbon material temperature are preferably 850°C or higher, and more preferably 1000°C or higher. This corresponds to the temperature at which PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid), representative PFAS substances, decompose. Most organic compounds also decompose at this temperature. Furthermore, the Boudouard reaction (reaction shown in equation (5)), in which CO2 reacts directly with carbon materials to produce CO, occurs significantly at temperatures above 1000°C. Therefore, by raising the temperature to 1000°C or higher, not only can PFAS and other substances be decomposed, but CO2 can also be effectively converted to CO.

[0085] On the other hand, excessively high temperatures can result in unnecessary power consumption, problems with material deterioration in the plasma processing unit 74, and increased costs for cooling the components. For this reason, the gas temperature and carbon material temperature are preferably 3000°C or less, and more preferably 2000°C or less.

[0086] Examples of temperature measurement methods include a method of estimating the temperature from the emission spectrum of the plasma processing unit 74, a method of measuring the temperature of the carbon material with a radiation thermometer, and a method of estimating the temperature of the reaction site from the ambient temperature, but the method is not limited to these as long as it is possible to measure the gas temperature or the carbon material temperature.

[0087] It is not necessary to react all of the carbon material 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, it is possible to recover carbon material in which only a portion (surface layer) has reacted. This decomposes and removes substances adsorbed near the surface of the carbon material. Although this reduces the amount of activated carbon, its adsorption performance is restored, allowing it to be reused.

[0088] Furthermore, a wet scrubber can be installed downstream of the plasma treatment unit 74 to treat the gas flowing out from the plasma treatment unit 74. The fluorine in the PFAS decomposed in the plasma treatment unit 74 can be dissolved in liquid by the wet scrubber and recovered as HF. Furthermore, nitrogen oxides and sulfur oxides derived from impurities (nitrogen components and sulfur components) contained in the CO2 and carbon material supplied to the plasma treatment unit 74 can be removed.

[0089] As described above, the carbon dioxide reforming system according to the seventh embodiment includes a carbon dioxide acquisition unit 5 that acquires carbon dioxide, a carbon material acquisition unit 6 that acquires the carbon material used in water or gas treatment, and a plasma reforming control unit 7 that reforms the carbon dioxide into carbon monoxide by performing plasma treatment on the carbon dioxide in the presence of the carbon material. This allows CO2 to be reformed into CO, and by performing plasma reforming of CO2 in the presence of the carbon material, not only can the conversion rate to CO be improved, but also used carbon material that is normally incinerated (C + O2 → CO2) can be recycled (C + O → CO, C + CO2 → 2CO), reducing CO2 emissions and recycling the carbon material as CO. Furthermore, by reforming adsorbates adsorbed to the carbon material by plasma, harmfulness is reduced.

[0090] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment. [Explanation of symbols]

[0091] 5 carbon dioxide acquisition unit, 6 carbon material acquisition unit, 7 plasma reforming control unit, 200 carbon dioxide reforming system.

Claims

1. a carbon dioxide acquisition step of acquiring carbon dioxide; a carbon material obtaining step of obtaining the carbon material used in the treatment of water or gas; a plasma treatment step of reforming the carbon dioxide into carbon monoxide by subjecting the carbon dioxide to plasma treatment in the presence of the carbon material; A carbon dioxide reforming method comprising the steps of:

2. 2. The carbon dioxide reforming method according to claim 1, wherein the carbon material is activated carbon that has adsorbed an adsorbate in the treatment.

3. 3. The carbon dioxide reforming method according to claim 2, wherein the adsorbed substance is an organic fluorine compound.

4. 4. The carbon dioxide reforming method according to claim 3, wherein the plasma treatment step performs the plasma treatment on the carbon dioxide in the presence of water.

5. 4. The carbon dioxide reforming method according to claim 3, wherein in the plasma treatment step, the carbon monoxide is discharged through a fluorine trap portion.

6. 5. The carbon dioxide reforming method according to claim 4, wherein in the plasma treatment step, the carbon monoxide is discharged through a fluorine trap portion.

7. 6. The carbon dioxide reforming method according to claim 5, wherein the fluorine trap section traps fluorine from the organic fluorine compound with calcium.

8. The carbon dioxide reforming method according to claim 1, characterized in that the plasma treatment step controls the residence time of the carbon material by a carbon material discharge control unit, and discharges the carbon material whose surface portion has been reacted by the plasma treatment.

9. 2. The carbon dioxide reforming method according to claim 1, wherein the carbon material obtained in the carbon material obtaining step is preheated with exhaust heat from the reforming reaction to carbon monoxide in the plasma treatment step.

10. 10. The carbon dioxide reforming method according to claim 1, wherein the carbon dioxide obtained in the carbon dioxide obtaining step is preheated by exhaust heat from a reforming reaction to carbon monoxide in the plasma treatment step.

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