Gas treatment method and gas treatment device

Abstract

One aspect of the present invention relates to a gas treatment method comprising: a step for absorbing a gas to be treated containing an acidic compound in a treatment liquid phase-separated by absorbing the acidic compound; a step for separating the treatment liquid, which absorbs the acidic compound and is phase-separated into a first phase fraction in which the acidic compound content is relatively high and a second phase fraction in which the acidic compound content is relatively low, into a first liquid mainly containing the first phase fraction and a second liquid mainly containing the second phase fraction; a step for deoxidizing the separated second liquid; and a step for releasing the acidic compound from the first liquid and the second liquid by heating the first liquid together with the deoxygenated second liquid.

Description

Technical Field

[0001] The invention relates to a gas processing method and a gas processing device. Background Art

[0002] Various methods are known as methods for recovering carbon dioxide (CO2) from large-volume gases (CO2-containing gases) such as exhaust gas from power plants and byproduct gases in blast furnaces. Examples of such methods include chemical absorption methods such as amine absorption methods. Chemical absorption methods are methods in which an alkaline aqueous solution such as an aqueous amine solution is used as an absorption liquid (treatment liquid), CO2-containing gas is brought into contact with the absorption liquid to absorb CO2, and then the absorption liquid that has absorbed CO2 is heated to release CO2 from the absorption liquid, thereby recovering the released CO2.

[0003] In the chemical absorption method, a large amount of heat energy is required in the step of heating the absorption liquid that has absorbed CO2 and releasing CO2 from the absorption liquid, i.e., the so-called absorption liquid regeneration step. Therefore, the method of recovering CO2 by the chemical absorption method increases the cost (operating cost) for separating and recovering CO2. In order to reduce the operating cost, research is being conducted on technologies such as reducing the energy required for separating and recovering acidic compounds such as CO2.

[0004] As a chemical absorption method capable of reducing the running cost, for example, the method described in Patent Document 1 can be cited. Patent Document 1 describes a gas treatment method, which includes: an absorption step, in which a gas to be treated containing an acidic compound that generates an acid by dissolving in water is brought into contact with a treatment liquid that undergoes phase separation by absorbing the acidic compound in an absorber, and the treatment liquid absorbs the acidic compound contained in the gas to be treated; a liquid feeding step, in which the treatment liquid that has absorbed the acidic compound contained in the gas to be treated is fed from the absorber to a regenerator; and a regeneration step, in which the treatment liquid is heated in the regenerator to separate the acidic compound from the treatment liquid, wherein in the absorption step, the treatment liquid that has come into contact with the acidic compound in the gas to be treated is phase-separated into a first phase portion having a high acidic compound content and a second phase portion having a low acidic compound content, and in the liquid feeding step, the treatment liquid in a mixed state of the phase-separated first phase portion and the second phase portion is introduced into the regenerator.

[0005] In order to further reduce the cost (operating cost) for separating and recovering acidic compounds such as CO 2 , it is required to suppress the deterioration of the treatment liquid.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 2018-187553 Summary of the invention

[0009] An object of the present invention is to provide a gas treatment method and a gas treatment apparatus capable of suppressing the deterioration of a treatment liquid used and capable of separating and recovering acidic compounds over a long period of time.

[0010] A gas treatment method according to one aspect of the present invention comprises: a step of bringing a treated gas containing an acidic compound that generates an acid by dissolving in water into contact with a treatment liquid that undergoes phase separation by absorbing the acidic compound, thereby allowing the treatment liquid to absorb the acidic compound; a step of separating the treatment liquid that undergoes phase separation by absorbing the acidic compound into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound, into a first liquid that mainly comprises the first phase portion and a second liquid that mainly comprises the second phase portion; a step of deoxygenating the separated second liquid; and a step of releasing the acidic compound from the first liquid and the second liquid by heating the first liquid together with the deoxygenated second liquid.

[0011] In addition, a gas treatment device according to another aspect of the present invention includes: an absorber for bringing a treated gas containing an acidic compound that generates an acid by dissolving in water into contact with a treatment liquid that undergoes phase separation by absorbing the acidic compound, thereby allowing the treatment liquid to absorb the acidic compound; a separator for separating the treatment liquid, which has been subjected to phase separation into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound by absorbing the acidic compound in the absorber, into a first liquid mainly containing the first phase portion and a second liquid mainly containing the second phase portion; a deoxygenation treatment section for deoxygenating the separated second liquid; and a releaser for releasing the acidic compound from the first liquid and the second liquid by heating the first liquid together with the deoxygenated second liquid.

[0012] The above and other objects, features and advantages of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram showing an example of a gas processing device according to an embodiment of the present invention.

[0014] Figure 2 It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention.

[0015] Figure 3It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention.

[0016] Figure 4 It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention.

[0017] Figure 5 It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention.

[0018] Figure 6 It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention.

[0019] Figure 7 It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention.

[0020] Figure 8 It is a schematic diagram showing another example of the gas processing device according to the embodiment of the present invention. DETAILED DESCRIPTION

[0021] In the invention described in Patent Document 1, a treatment liquid that undergoes phase separation by absorbing an acidic compound such as CO2 is used as described above. Examples of the treatment liquid include treatment liquids containing water, amine compounds that can function as chemical absorbents, and organic solvents that can function as physical absorbents (representative components are ether compounds). The treatment liquid is a uniform single phase when no acidic compound is absorbed, but if an acidic compound is absorbed, the phase is separated into two phases. Specifically, the phase is separated into two phases, namely, a first phase portion (amine phase) having a relatively high acidic compound content and a second phase portion (organic solvent phase, ether phase) having a relatively low acidic compound content. If a treatment liquid that undergoes phase separation by absorbing an acidic compound, such as the treatment liquid described in Patent Document 1, is used, the regeneration temperature of the treatment liquid in the regeneration step (for example, below 100°C) will be lower than the regeneration temperature (for example, above 120°C) when a general treatment liquid that does not undergo phase separation by absorbing an acidic compound is used. In addition, according to Patent Document 1, when the second phase portion is introduced into the regenerator together with the first phase portion, the energy required for separating the acidic compound can be reduced compared to the case where the second phase portion having a low acidic compound content is removed. The reason for this is believed to be that in the regeneration step, the amine compound that does not interact (bond) with the acidic compound is transferred from the first phase portion to the second phase portion, and therefore, the acidic compound is easily released from the first phase portion.

[0022] However, the treatment liquid contains: a component that gradually undergoes chemical changes during long-term use in the recovery of acidic compounds. The component that undergoes chemical changes is a component that constitutes the first phase portion after the treatment liquid undergoes phase separation (a component mainly contained in the first phase portion). Specifically, if the treatment liquid contains an amine compound and an organic solvent, the component is the amine compound. Due to this change, the performance of the treatment liquid decreases, so in order to maintain the performance of the treatment liquid, it is necessary to supplement (or replace) the components that constitute the first phase portion, such as the amine compound. In order to reduce the cost (operating cost) for separating and recovering acidic compounds such as CO2, it is required to suppress the degradation of the treatment liquid, that is, to suppress the degradation of the components that constitute the first phase portion, such as the amine compound.

[0023] The present inventors have conducted various studies and have found that the above-mentioned object can be achieved by the following present invention, that is, to provide a gas treatment method and a gas treatment apparatus capable of suppressing the degradation of the treatment liquid used and separating and recovering the acidic compounds for a long period of time.

[0024] Hereinafter, embodiments according to the present invention will be described, but the present invention is not limited to these embodiments.

[0025] A gas treatment method according to an embodiment of the present invention is a method for separating and recovering an acidic compound from a gas to be treated containing the acidic compound, using a treatment liquid that undergoes phase separation by absorbing the acidic compound that generates an acid when dissolved in water.

[0026] The gas treatment method first brings the treated gas containing the acidic compound into contact with the treatment liquid. As a result, the acidic compound is absorbed in the treatment liquid. The treatment liquid that has absorbed the acidic compound is phase-separated into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound. In addition, the step of bringing the treated gas into contact with the treatment liquid to absorb the acidic compound is also referred to as an absorption step.

[0027] In the gas treatment method, after the absorption step, the gas is separated into a first liquid mainly containing the first phase part and a second liquid mainly containing the second phase part. As this separation, it is preferred to separate into a first liquid formed by the first phase part and a second liquid formed by the second phase part, but the first liquid can mainly contain the first phase part or the second phase part. In addition, the second liquid can mainly contain the second phase part or the first phase part. Mainly containing means that its phase part contains, for example, 80% by mass or more, preferably 100% by mass. In addition, the step of separating the first liquid and the second liquid is also referred to as a separation step below.

[0028] The gas treatment method performs a deoxygenation treatment on the second liquid separated in the separation step. By performing the deoxygenation treatment, the amount of oxygen (dissolved oxygen) dissolved in the second liquid can be reduced. In addition, the step of deoxygenating the second liquid is also referred to as a deoxygenation treatment step.

[0029] The gas treatment method heats the first liquid together with the second liquid that has been subjected to the deoxidation treatment. The heating may be, for example, heating a mixed liquid obtained by mixing the first liquid and the second liquid that has been subjected to the deoxidation treatment. By heating, if the mixed liquid (the first liquid and the second liquid) reaches a temperature above a specified temperature, the acidic compound can be released from the first liquid and the second liquid. In addition, the step of heating the mixed liquid (the first liquid and the second liquid) is also referred to as a release step.

[0030] In the gas treatment method, the components contained in the treated gas that are not absorbed by the treatment liquid will not be absorbed by the treatment liquid in the absorption step, and therefore will not be released from the treatment liquid in the release step. In addition, the components that are difficult to be absorbed by the treatment liquid are difficult to be absorbed by the treatment liquid in the absorption step, and therefore, the amount released from the treatment liquid in the release step is small. In addition, the components contained in the treated gas that are absorbed by the treatment liquid and will not be released from the treatment liquid even if the treatment liquid is heated will not be released from the treatment liquid in the release step. For these reasons and others, the gas treatment method can recover high-concentration (concentration higher than the concentration of the acidic compound in the treated gas) acidic compounds by allowing the treatment liquid to absorb the acidic compounds and release them from the treatment liquid as described above. In addition, the gas treatment method can appropriately remove dissolved oxygen from the second liquid by deoxygenating the second liquid in the deoxygenation step. Therefore, the gas treatment method can appropriately suppress the occurrence of degradation (oxidative degradation) of the treatment liquid due to dissolved oxygen, and can separate and recover the acidic compounds over a long period of time.

[0031] The gas to be treated may contain any gas containing the acidic compound, or may contain any gas other than the acidic compound. As the gas other than the acidic compound, for example, nitrogen and other gases that are difficult to be absorbed by the treatment liquid may be cited. As the gas to be treated, specifically, exhaust gas from a power plant and byproduct gas in a blast furnace may be cited. As in the exemplified gas to be treated, generally speaking, the gas to be treated contains not only the acidic compound, but also gases other than the acidic compound. In addition, in many cases, gases other than the acidic compound are more difficult to be absorbed by the treatment liquid than the acidic compound. In the case where the gas other than the acidic compound is difficult to be absorbed by the treatment liquid, in the absorption step, the acidic compound is absorbed in the treatment liquid, and the components other than the acidic compound are difficult to be absorbed by the treatment liquid. Therefore, in the gas treatment method, acidic compounds with a high concentration (concentration higher than the concentration of the acidic compound in the gas to be treated) can be recovered.

[0032] The acidic compound is not particularly limited as long as it is a compound that generates an acid by dissolving in water. Examples of the acidic compound include acidic compounds contained in exhaust gas from power plants and byproduct gases in blast furnaces. More specifically, examples of the acidic compound include carbon dioxide and sulfur oxides (SO X ) and sulfur compounds such as hydrogen sulfide, etc.

[0033] As described above, the treatment liquid is a treatment liquid that is phase-separated into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound by absorbing the acidic compound. As the treatment liquid, for example, an aqueous solution of an amine compound can be cited. The aqueous solution of the amine compound may also contain an organic solvent. As the treatment liquid, it is preferred to use, for example, a treatment liquid containing water, an amine compound and an organic solvent. That is, as the treatment liquid, it is preferably a treatment liquid containing water, an amine compound and an organic solvent, and phase-separated into the first phase portion and the second phase portion. The treatment liquid is preferably phase-separated by absorbing the acidic compound, and the temperature (regeneration temperature) of the treatment liquid that can release the acidic compound from the treatment liquid can be appropriately reduced. In addition, the first phase portion is a phase in which the amine compound content is higher than the amine compound content in the second phase portion, and is hereinafter also referred to as an amine phase. The second phase portion is a phase in which the organic solvent content is higher than the organic solvent content in the first phase portion. Therefore, since a typical component of the organic solvent is an ether compound, the second phase portion is hereinafter also referred to as an ether phase or an organic phase.

[0034] The amine compound is not limited to a primary amine, and secondary amines and tertiary amines may also be mentioned. The primary amine may be, for example, 2-aminoethanol [MEA: solubility parameter = 14.3 (cal / cm 3 ) 1 / 2 ], and 2-(2-aminoethoxy)ethanol [AEE: solubility parameter = 12.7 (cal / cm 3 ) 1 / 2 ] etc. Examples of the secondary amine include 2-(methylamino)ethanol [MAE: solubility parameter = 12.5 (cal / cm 3 ) 1 / 2 ], and 2-(ethylamino)ethanol [EAE: solubility parameter = 12.0 (cal / cm 3 ) 1 / 2 ], etc. As the tertiary amine, for example, triethanolamine (TEA), N-methyldiethanolamine (MDEA), tetramethylethylenediamine (TEMED), pentamethyldiethylenetriamine (PMDETA), hexamethyltriethylenetetramine, and bis(2-dimethylaminoethyl)ether, etc. can be mentioned. The amine compound can be used alone or in combination of two or more.

[0035] Examples of the organic solvent include 1-butanol [solubility parameter = 11.3 (cal / cm 3 ) 1 / 2 ], 1-pentanol [solubility parameter = 11.0 (cal / cm 3 ) 1 / 2 ], octanol, diethylene glycol diethyl ether [DEGDEE: solubility parameter = 8.2 (cal / cm 3 ) 1 / 2 ], and diethylene glycol dimethyl ether (DEGDME), etc. These organic solvents may be used alone or in combination of two or more.

[0036] In the case where the treatment liquid is a treatment liquid containing the amine compound, the organic solvent and water, the amine compound content is preferably 20% by mass or more and less than 40% by mass. In addition, the organic solvent content is preferably 40% by mass or more and 60% by mass or less. In addition, in the treatment liquid, water is the remainder, and the water content is preferably more than 0% by mass and less than 20% by mass. As the treatment liquid, for example, a treatment liquid in which the amine compound is 30% by mass, the organic solvent is 60% by mass, and the water is 10% by mass can be cited. In addition, in addition to the amine compound, the organic solvent and water, the treatment liquid may also contain other components such as ionic liquids.

[0037] When the treatment liquid contains the amine compound, the organic solvent, and water, the value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound (solubility parameter difference) is preferably 1.1 (cal / cm 3 ) 1 / 2 Above and 4.2 (cal / cm 3 ) 1 / 2 In addition, the solubility parameter was calculated by the following formula (1).

[0038] δ= [(ΔH -RT) / V] 1 / 2 (1)

[0039] In formula (1), δ represents the solubility parameter, ΔH represents the molar latent heat of vaporization, R represents the gas constant, T represents the absolute temperature, and V represents the molar volume.

[0040] The following description is given: When the treatment liquid contains an amine compound, an organic solvent and water, it is in a state after absorbing carbon dioxide. As the treatment liquid, a treatment liquid containing 30% by mass of an amine compound, 60% by mass of an organic solvent, and 10% by mass of water was used, and the combination of the amine compound and the organic solvent was changed, and the state of the treatment liquid under each combination was observed. The results are shown in Table 1. It should be noted that Table 1 shows the solubility parameter of the amine compound, the solubility parameter of the organic solvent, the value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound (solubility parameter difference), and the state of the treatment liquid after absorbing carbon dioxide. "Good" in Table 1 means: before absorbing carbon dioxide, it is a liquid phase, and it is separated into two liquid phases by absorbing carbon dioxide. In addition, "immiscible" in Table 1 means: before absorbing carbon dioxide, it is a two-liquid phase state, and no liquid phase is formed. In addition, "non-separation" in Table 1 means: after absorbing carbon dioxide, it is also a liquid phase. In addition, "-" in Table 1 means: the treatment liquid under this combination is not observed, and there is no result. It should be noted that the solubility parameter of the amine compound and the solubility parameter of the organic solvent shown in Table 1 are recorded only to one decimal place due to the relationship between significant figures. Therefore, the value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound may have rounding errors and may not be the difference in solubility parameters recorded in Table 1.

[0041] Table 1

[0042]

[0043] As can be seen from Table 1, when the treatment liquid contains an amine compound, an organic solvent, and water, the value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound (solubility parameter difference) is preferably within a specified range. Specifically, the solubility parameter difference is preferably 1.1 (cal / cm 3 ) 1 / 2 Above and 4.2 (cal / cm 3 ) 1 / 2 Below, more preferably 1.2 (cal / cm 3 ) 1 / 2 Above and 3.8 (cal / cm 3 ) 1 / 2 As follows. By selecting the amine compound and the organic solvent in such a manner that the solubility parameter difference is within the above range, the treatment liquid can absorb carbon dioxide, and is in a one-phase state before absorbing carbon dioxide, and becomes a two-phase state after absorbing carbon dioxide. That is, the treatment liquid becomes phase-separated by absorbing carbon dioxide. If the solubility parameter difference is too small, there is a tendency that phase separation will not occur even if carbon dioxide is absorbed by the resulting liquid. In addition, if the solubility parameter difference is too large, there is a tendency that the resulting liquid is in a two-phase state before absorbing carbon dioxide. In this two-phase state, the organic solvent is not fully miscible with water, and the amine compound is contained more in one of the phases, such as the aqueous phase. Even if the treated gas is brought into contact with the liquid in this state, the contact state between the liquid and the treated gas becomes uneven, and there is a risk of reduced absorption efficiency.

[0044] If the treatment liquid is used for a long time to recover the acidic compound as described above, it will gradually deteriorate. That is, if it is used for a long time to recover the acidic compound, the treatment liquid contains components that gradually deteriorate chemically. The representative component of the deterioration is the component constituting the first phase part, which is the amine compound in the case of the treatment liquid containing the amine compound, the organic solvent and water.

[0045] As degradation of the amine compound, the degradation due to heating, i.e., thermal degradation, can be cited first. In the gas treatment method, since a treatment liquid that performs phase separation by absorbing an acidic compound is used, the regeneration temperature can be lowered compared to the case where other treatment liquids (treatment liquids that do not perform phase separation) are used. Therefore, it is considered that the degradation of the amine compound is sufficiently suppressed.

[0046] As the degradation, in addition to the thermal degradation, there can be cited degradation caused by oxidation of the amine compound by oxygen (dissolved oxygen) dissolved in the treatment liquid, that is, oxidation degradation. In the gas treatment method, it is believed that the influence of the oxidation degradation is large because the thermal degradation is suppressed. In order to suppress the oxidation degradation that is considered to have a large influence, the present inventors focused on reducing the dissolved oxygen in the treatment liquid by deoxygenating the treatment liquid. At this time, the present inventors also studied the position where the deoxygenation treatment was performed. As a result, it was found that the composition of the first phase part and the second phase part became the following composition. The amine phase as the first phase part has a relatively high content of the amine compound (the organic solvent: the ether compound content is relatively low), so the polarity becomes relatively high. Therefore, the water content of the amine phase as the first phase part is relatively high, and the dissolved oxygen content is relatively low. On the other hand, the ether phase as the second phase part has a relatively low polarity because the ether compound content is relatively high (the amine compound content is relatively low). Therefore, the water content of the ether phase as the second phase is relatively low, and the dissolved oxygen content is relatively high. When the treatment liquid is subjected to deoxygenation treatment, in order to minimize the dissolved oxygen in the treatment liquid, it is considered to deoxygenate the entire treatment liquid. In addition, it is also possible to consider deoxygenating the first liquid mainly containing an amine phase, which is the first phase part that contains more amine compounds that are the object of oxidative degradation. The present inventors have found that as the location for deoxygenation treatment, instead of deoxygenating these (the entire treatment liquid or the first liquid), or adding a second liquid mainly containing the second phase part on the basis of them, it is possible to effectively inhibit the oxidative degradation of the amine compound. That is, it was found that deoxygenating the second liquid mainly containing the second phase part can effectively inhibit the oxidative degradation of the components constituting the first phase part (components mainly contained in the first phase part: amine compounds). Based on these, the present inventors have found that, instead of performing the deoxidation treatment on the first liquid mainly containing the first phase portion (containing a large amount of components to be oxidatively degraded), performing the deoxidation treatment on the second liquid can effectively suppress the oxidative degradation of the components constituting the first phase portion (the components mainly contained in the first phase portion). In addition, in general, when treating an oxidizing atmosphere gas such as exhaust gas, oxidative degradation is more problematic than thermal degradation. From this point of view, it is also believed that being able to effectively suppress oxidative degradation appropriately contributes to effectively suppressing the degradation of the treatment liquid used.

[0047] Furthermore, in the gas treatment method, the deoxidation treatment is performed on the second liquid before the first liquid and the second liquid are mixed. Therefore, the deoxidation treatment is performed on the second liquid which is a part of the treatment liquid before the treatment liquid is heated to release the acidic compounds from the treatment liquid. Therefore, when the treatment liquid is heated to release the acidic compounds from the treatment liquid, the treatment liquid has become a treatment liquid that has been deoxidized. The higher the temperature, the more likely it is to cause oxidative degradation. Therefore, it is believed that by performing the deoxidation treatment on the treatment liquid before mixing with the first liquid, that is, the second liquid, and thus performing the deoxidation treatment before heating to release the acidic compounds from the treatment liquid, oxidative degradation can be effectively suppressed.

[0048] Based on the above reasons, the thermal degradation of the treatment liquid can be suppressed, and the oxidative degradation of the treatment liquid can also be effectively suppressed. Therefore, the degradation of the treatment liquid used can be suppressed, and the acidic compounds can be separated and recovered continuously for a long time. That is, the acidic compounds can be separated and recovered continuously for a long time without replenishing or replacing the treatment liquid.

[0049] In order to confirm the effectiveness of the gas treatment method, that is, whether the deterioration of the treatment liquid used can be suppressed and the acidic compounds can be separated and recovered continuously for a long period of time, the following study was conducted.

[0050] As the treatment liquid, the solvent oxygen concentration in a representative treatment liquid, that is, a treatment liquid containing 30 mass% of EAE as an amine compound, 60 mass% of DEGDEE as an organic solvent, and 10 mass% of water was calculated. The dissolved oxygen concentration is calculated by "assuming that each component (EAE, DEGDEE and water) is a pure substance, and the sum of the dissolved oxygen concentrations calculated according to the Henry constant × the molar fraction of each component". In addition, the Henry constant is calculated by fitting the dissolved oxygen concentration predicted by the PSRK model. As the calculation conditions at this time, a temperature of 50°C, a carbon dioxide partial pressure of 15kPa, an oxygen partial pressure of 5kPa, a Henry constant of EAE of 66690kPa, a Henry constant of DEGDEE of 63406kPa, and a Henry constant of water of 5314267kPa were used. The calculation results are shown in Table 2.

[0051] Table 2

[0052]

[0053] In the average value of the amine phase as the first phase and the ether phase as the second phase (i.e., the mixed phase of the amine phase and the ether phase), the concentration of EAE was calculated to be 26.7 mol%, and the concentration of dissolved oxygen was 44 ppm. On the other hand, in the ether phase, the concentration of EAE was calculated to be 5.9 mol%, and the concentration of dissolved oxygen was 64 ppm. Although the reaction mechanism of the oxidative degradation of EAE is unclear, assuming that the reaction rate is linearly proportional to the concentration of EAE and the concentration of dissolved oxygen, it is calculated that at the same temperature, the mixed phase is oxidized about 3.1 times [= (26.7) × 44 / (5.9 × 64)] faster than the second phase. Based on this result, it can be confirmed that compared with heating the amine phase and the ether phase after mixing to a specified temperature, heating only the ether phase and deoxygenating it, mixing it with the amine phase, and then heating it to a specified temperature can inhibit oxidative degradation.

[0054] The deoxygenation treatment is not particularly limited as long as it is performed on the second liquid and can remove dissolved oxygen from the second liquid. Examples of the deoxygenation treatment include: a treatment of heating the second liquid (heating treatment), a treatment of contacting the second liquid with a deoxidizer (deoxidizer contact treatment), a treatment of decompressing the second liquid (decompression treatment), a treatment of irradiating the second liquid with ultrasound (ultrasonic irradiation treatment), a treatment of supplying hydrogen to the second liquid (hydrogen supply treatment), and a treatment of contacting the second liquid with a precious metal catalyst while supplying hydrogen to the second liquid (catalyst contact treatment). The deoxygenation treatment may be performed by any of these treatments alone or in combination of two or more.

[0055] The heating treatment is not particularly limited as long as it is a treatment that heats the second liquid and can remove dissolved oxygen from the second liquid. As the heating treatment, it is not particularly limited as long as the temperature of the second liquid (heating temperature) is a temperature that can remove dissolved oxygen from the second liquid. In addition, the conditions of the heating treatment can be appropriately specified, for example, the following conditions are preferred. As the heating treatment, more specifically, it is preferred that the temperature of the second liquid (heating temperature) is a heating treatment that is above the temperature that can remove dissolved oxygen from the second liquid and is lower than the temperature of the treatment liquid (regeneration temperature) that can release the acidic compound from the treatment liquid. If the heating temperature is too low, there is a tendency that the second dissolved oxygen cannot be fully removed. In addition, if the heating temperature is too high, there is a tendency that the treatment agent (the components contained therein) evaporates.

[0056] The deoxidizing agent contact treatment is not particularly limited as long as it is a treatment that can remove dissolved oxygen from the second liquid by bringing the second liquid into contact with the deoxidizing agent. The deoxidizing agent is not particularly limited as long as it is a deoxidizing agent that can remove dissolved oxygen from the second liquid by contacting with a liquid containing dissolved oxygen.

[0057] The decompression treatment is not particularly limited as long as it is a treatment that can remove dissolved oxygen from the second liquid by decompressing the second liquid. As the decompression treatment, for example, a treatment of decompressing the atmosphere in which the second liquid exists can be cited. In addition, the conditions of the decompression treatment can be appropriately specified. For example, as long as the pressure (degree of decompression) during the decompression treatment is a pressure lower than the pressure (absorption pressure) when oxygen is absorbed by the second liquid, it is not particularly limited. In addition, the decompression treatment is preferably carried out at a pressure at which the second liquid does not boil. That is, the decompression treatment is preferably carried out at a pressure higher than the vapor pressure of water, which is the most easily boiling component among the components of the treatment liquid. If the decompression is too low, there is a tendency that the second dissolved oxygen cannot be fully removed. In addition, if the decompression is too high, there is a tendency that the treatment liquid (the components contained therein) evaporates (boils).

[0058] The ultrasonic irradiation treatment is not particularly limited as long as it is a treatment that can remove dissolved oxygen from the second liquid by irradiating the second liquid with ultrasonic waves. In addition, the conditions for irradiating ultrasonic waves can be appropriately specified, for example, the irradiation time of the ultrasonic waves is preferably, for example, less than 30 minutes. If the irradiation time of the ultrasonic waves is too short, there is a tendency that the second dissolved oxygen cannot be fully removed. In addition, if the irradiation time of the ultrasonic waves is too long, there is a tendency that the effect obtained by irradiating ultrasonic waves is saturated.

[0059] The hydrogen supply treatment is not particularly limited as long as it is a treatment that supplies hydrogen to the second liquid and can remove dissolved oxygen from the second liquid. In addition, the catalyst contact treatment is not particularly limited as long as it is a treatment that supplies hydrogen to the second liquid and brings the second liquid into contact with a precious metal catalyst, thereby removing dissolved oxygen from the second liquid.

[0060] In the hydrogen supply process and the catalyst contact process, as a method of supplying hydrogen to the second liquid, for example, a method of supplying hydrogen to the second liquid via a gas permeable membrane, a method of supplying hydrogen to the second liquid using a gas nozzle, etc. By supplying hydrogen via a gas permeable membrane or using a gas nozzle, hydrogen can be dissolved in the second liquid.

[0061] The breathable membrane is a membrane whose permeability to gases such as hydrogen is higher than that to liquids such as water. Specifically, a membrane that does not allow liquid to pass through but can pass through gas can be cited. As the breathable membrane, for example, a membrane made of fluororesin such as polytetrafluoroethylene, a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (PFA) and polytetrafluoroethylene (PTFE) can be cited. In addition, the shape of the breathable membrane is not limited, for example, it can be a flat membrane or a hollow fiber membrane, preferably a hollow fiber membrane. In addition, the gas nozzle is not particularly limited as long as it can supply hydrogen to the second liquid.

[0062] The catalyst contact treatment is not particularly limited as long as it is a treatment that allows the second liquid to contact with a precious metal catalyst while supplying hydrogen to the second liquid, thereby removing dissolved oxygen from the second liquid. The method for contacting the second liquid with a precious metal catalyst is not particularly limited, as long as the second liquid supplied with hydrogen contacts with a precious metal catalyst and can remove dissolved oxygen from the second liquid, it is not particularly limited. Specifically, the method is a method for removing dissolved oxygen from the second liquid by reacting the dissolved oxygen contained in the second liquid with the hydrogen supplied to the second liquid in the presence of the precious metal catalyst. The precious metal catalyst is not particularly limited as long as it is a catalyst that can promote the reaction of the dissolved oxygen contained in the second liquid with the hydrogen supplied to the second liquid. As the precious metal catalyst, for example, a palladium catalyst can be cited, and more specifically, a catalyst that supports metal palladium on various carriers is preferred. As the carrier, for example, ion exchange resins, activated carbon, synthetic adsorbents, and inorganic exchangers can be cited. In addition, a specific method for bringing the second liquid into contact with the noble metal catalyst includes, for example, a method in which the second liquid supplied with hydrogen gas is continuously flowed into a tower filled with a noble metal catalyst such as the palladium catalyst to bring the second liquid into contact with the noble metal catalyst.

[0063] The release step is not particularly limited as long as the first liquid and the second liquid subjected to the deoxygenation treatment are heated together so that the acidic compound can be released from the first liquid and the second liquid. The released acidic compound is preferably carbon dioxide. Therefore, the temperature of the first liquid and the second liquid in the release step is preferably above the temperature at which the carbon dioxide absorbed by the first liquid and the second liquid is released from the first liquid and the second liquid (the treatment liquid). Specifically, the temperature (heating temperature) is preferably above 80°C and preferably below 100°C.

[0064] The release step preferably involves bringing a gas that is hardly soluble in the treatment liquid into contact with the mixed liquid when releasing the acidic compound from the mixed liquid (the first liquid and the second liquid). The gas that is hardly soluble in the treatment liquid is preferably hydrogen. That is, the release step preferably involves bringing hydrogen into contact with the mixed liquid when releasing the acidic compound from the mixed liquid. By bringing hydrogen into contact in this way, the temperature at which carbon dioxide is released from the treatment liquid is lowered, so that acidic compounds such as carbon dioxide can be separated and recovered from the treated gas with lower energy. In the case where hydrogen is supplied in this way, the heating temperature in the release step is, specifically, preferably above 50°C and preferably below 90°C. In addition, as the deoxygenation treatment, in the case of a deoxygenation treatment using hydrogen such as the hydrogen supply treatment or the catalyst contact treatment, the hydrogen supplied in the release step can also be supplied from the supply section that supplies hydrogen in the deoxygenation treatment.

[0065] The device (gas treatment device) for implementing the gas treatment method is not particularly limited as long as it can implement the absorption step, the separation step, the deoxygenation treatment step and the release step. The gas treatment device may include the following gas treatment devices, etc., which include: an absorber, which allows the gas to be treated containing the acidic compound to contact with the treatment liquid that has been phase-separated by absorbing the acidic compound, so that the treatment liquid absorbs the acidic compound; a separator, which separates the treatment liquid that has been phase-separated into the first phase part and the second phase part by allowing the treatment liquid to absorb the acidic compound in the absorber, into a first liquid mainly containing the first phase part and a second liquid mainly containing the second phase part; a deoxygenation treatment section, which deoxygenates the separated second liquid; and a releaser, which releases the acidic compound from the first liquid and the second liquid by heating the first liquid together with the second liquid that has been deoxygenated. The gas treatment device implements the absorption step in the absorber, the separation step in the separator, the deoxygenation treatment step in the deoxygenation treatment section, and the release step in the releaser, thereby suppressing the deterioration of the treatment liquid used and separating and recovering the acidic compounds for a long period of time.

[0066] The gas treatment device is used to recover high-concentration acidic compounds from a treated gas containing acidic compounds using the treatment liquid. As the gas treatment device 100, specifically, Figure 1 As shown, the device including an absorber 11, a separator 12, a heater (deoxidation treatment unit) 13, a releaser 14, a circulation channel 15 and a heat exchanger 16 can be cited. In addition, Figure 1 It is a schematic diagram showing an example of the gas processing device according to the present embodiment.

[0067] The circulation passage 15 includes a first flow path 21 for extracting the treated liquid from the absorber 11 and introducing it into the discharger 14, and a second flow path 22 for extracting the treated liquid from the discharger 14 and returning it to the absorber 11. In addition, the heat exchanger 16 may be omitted.

[0068] The absorber 11 is connected with: a gas supply channel 24 for supplying a treated gas; a gas exhaust channel 25 for exhausting the gas treated in the absorber 11; a first flow path 21 for conveying an absorption liquid to the releaser 14; and a second flow path 22 for returning the treatment liquid from the releaser 14 to the absorber 11. The gas supply channel 24 can supply the treated gas into the absorber 11. The gas exhaust channel 25 can exhaust from the absorber 11 the gas that is not absorbed even if the treated gas is brought into contact with the treatment liquid. The first flow path 21 can extract the treatment liquid accumulated in the absorber 11. The second flow path 22 can allow the treatment liquid refluxed from the releaser 14 to flow from top to bottom.

[0069] The absorber 11 allows the treated gas to contact with the treatment liquid, so that the treatment liquid absorbs acidic compounds such as carbon dioxide in the treated gas, and discharges the gas after the acidic compounds are removed. The absorber 11 can be any absorber as long as it allows the treated gas to contact the treatment liquid continuously. As the absorber 11, for example: an absorber that sprays the treatment liquid into the flow path of the treated gas in the form of mist; an absorber that allows the treatment liquid to flow along a filler arranged in the flow path of the treated gas; and an absorber that introduces the treated gas and the treatment liquid into a large number of fine flow paths respectively, and makes the fine flow paths of the treated gas and the fine flow paths of the treatment liquid merge respectively. In addition, the reaction in which the acidic compound is absorbed into the treatment liquid is an exothermic reaction.

[0070] The first flow path 21 and the second flow path 22 are connected to the discharger 14. The first flow path 21 can introduce the treatment liquid discharged from the absorber 11 into the discharger 14. The second flow path 22 can discharge the treatment liquid stored in the discharger 14.

[0071] The releaser 14 stores treatment solution and releases the acidic compound by heating the stored treatment solution to a temperature above that at which the acidic compound can be released. The release of the acidic compound from the treatment solution, i.e., the separation of the acidic compound from the components contained in the treatment solution, is an endothermic reaction. In addition, in the releaser 14, if the treatment solution is heated as described above, not only the acidic compound is released, but also the water contained in the treatment solution evaporates. That is, in the releaser 14, the acidic compound and water vapor are released from the treatment solution.

[0072] The separator 12 is provided on the first flow path 21. The separator 12 is divided into a first region 32 and a second region 33 by a partition wall 31. The treatment liquid discharged from the absorber 11 is stored in the first region 32. At this time, the treatment liquid is phase-separated into the first phase portion and the second phase portion, and the second phase portion is located above the first phase portion. Therefore, if the amount of the treatment liquid stored in the first region 32 increases, the second phase portion preferentially flows over the partition wall 31 into the second region 33 and is stored in the second region 33. The treatment liquid stored in the first region 32 is discharged from the first liquid flow path 35 connected to the lower portion of the first region 32. In addition, the treatment liquid stored in the second region 33 is discharged from the second liquid flow path 36 connected to the lower portion of the second region 33. By discharging in this way, the first liquid mainly composed of the first phase part flows through the first liquid flow path 35, and the second liquid mainly composed of the second phase part flows through the second liquid flow path 36. The separator 12 separates the first liquid and the second liquid in this way. In addition, a pump 37 and a pump 38 are provided in the first liquid flow path 35 and the second liquid flow path 36, respectively.

[0073] The heater 13 is connected to the second liquid flow path 36. The second liquid supplied from the second liquid flow path 36 is heated by the heater 13, thereby removing dissolved oxygen from the second liquid. That is, the second liquid is subjected to the heating treatment as the deoxidation treatment. The heater 13 is a treatment unit that heats the second liquid. As the heater 13, a heater that directly or indirectly heats the treatment liquid using any heat source such as electricity, steam, and a burner can be used. The oxygen (oxygen derived from dissolved oxygen) removed from the second liquid by the deoxidation treatment flows to the release channel 51 via the oxygen exhaust channel 41. In addition, the second liquid after the deoxidation treatment is mixed with the first liquid flowing in the first liquid flow path 35 via the second liquid supply channel 42. The mixed liquid in which the first liquid and the second liquid after the deoxidation treatment are mixed is introduced into the releaser 14 via the first flow path 21.

[0074] The releaser 14 is connected to a release channel 51 and a heating flow path 52. An acid compound separator 53 is provided in the release channel 51. The acid compound separator 53 cools the mixed gas of the acid compound and water vapor released from the treatment liquid, thereby condensing the water vapor and separating it into condensed water and acid compounds. The acid compound separator 53 is connected to a supply channel 54 and a circulation path 55. The supply channel 54 supplies the acid compound separated in the acid compound separator 53 to the supply object. The water separated in the acid compound separator 53 flows back to the releaser 14 via the circulation path 55. In addition, the acid compound separator 53 and the circulation path 55 can also be omitted.

[0075] A first heating section 56 is provided on the heating flow path 52. The first heating section 56 heats the treatment liquid, returns a portion of the treatment liquid to the releaser 14 via the loop flow path 57, and returns the remaining portion of the treatment liquid to the absorber 11 via the second flow path 22. A pump 59 is provided on the second flow path 22. The first heating section 56 can be configured to heat the treatment liquid inside the releaser 14, but as shown in the figure, it can also heat the treatment liquid extracted from the releaser 14 to the outside. In addition, as the first heating section 56, a heating section that directly or indirectly heats the treatment liquid using any heat source such as electricity, steam, and a burner can be used.

[0076] The heat exchanger 16 is connected to the first flow path 21 and the second flow path 22, so that heat exchange is performed between the treatment liquid flowing through the first flow path 21 and the treatment liquid flowing through the second flow path 22. The heat exchanger 16 is composed of, for example, a plate heat exchanger, but may also be composed of a microchannel heat exchanger capable of performing heat exchange between fluids with a small temperature difference. Thus, energy efficiency can be improved.

[0077] The gas treatment device 100 performs the absorption step in the absorber 11, performs the separation step in the separator 12, performs the deoxidation step in the heater 13, and performs the release step in the releaser 14, thereby recovering high-concentration acidic compounds from the treated gas containing the acidic compounds. In addition, the gas treatment device 100 can suppress the deterioration of the used treatment liquid by performing the deoxidation step in the heater 13, and can use the treatment liquid for the recovery of the acidic compounds for a long time.

[0078] As other devices for implementing the gas treatment method, for example, Figure 2 The gas processing device 200 and Figure 3As in the gas processing device 300 shown in the figure, the separation step is performed in the separator 12 provided in the absorber 11.

[0079] The gas processing device 200 is as follows Figure 2 As shown, the absorber 11 is provided with a separator 12. The separator 12 is provided at the lower portion of the absorber 11 and is divided into a first region 32 and a second region 33 by a partition wall 31. In addition, a partition wall 34 is provided in the separator 12 so as to cover the upper portion of the second region. The treatment liquid in the absorber 11 is stored in the first region 32. At this time, the treatment liquid is phase-separated into the first phase portion and the second phase portion, and the second phase portion is located above the first phase portion. Therefore, if the amount of the treatment liquid stored in the first region 32 increases, the second phase portion preferentially flows over the partition wall 31 and flows into the second region 33, and is stored in the second region 33. In addition, since the partition wall 34 is provided in the second region 33, the treatment liquid other than the portion flowing over the partition wall 31 will not flow in. The treatment liquid stored in the first region 32 is discharged from the first liquid flow path 35 connected to the lower portion of the first region 32. In addition, the treatment liquid stored in the second area 33 is discharged from the second liquid flow path 36 connected to the lower part of the second area 33. By discharging in this way, the first liquid mainly composed of the first phase part flows in the first liquid flow path 35, and the second liquid mainly composed of the second phase part flows in the second liquid flow path 36. The separator 12 separates the first liquid and the second liquid in this way. In addition to the separator 12, the gas treatment device 200 is also provided with Figure 1 The gas processing device 100 shown is the same.

[0080] like Figure 3As shown, in the gas treatment device 300, the treatment liquid stored in the absorber 11 is phase-separated into the first phase part and the second phase part by absorbing the acidic compound, and the second phase part is located above the first phase part. In addition, a first liquid flow path 35 is connected to the lower part of the absorber 11, and a second liquid flow path 36 is connected to a position higher than the first liquid flow path 35. Specifically, the second liquid flow path 36 is connected in a manner that is located at the lower part relative to the liquid surface 27 of the second phase part and is located at the upper part relative to the interface 28 between the first phase part and the second phase part. In addition, the first liquid flow path 35 is connected in a manner that is located at the lower part relative to the interface 28 between the first phase part and the second phase part. By discharging the treatment liquid from the first liquid flow path 35 connected in this way, the first liquid mainly composed of the first phase part circulates in the first liquid flow path 35. Furthermore, by discharging the treated liquid from the second liquid flow path 36 connected as described above, the second liquid mainly composed of the second phase part flows through the second liquid flow path 36. The separator 12 separates the first liquid and the second liquid in this way. The gas treatment device 300 includes the separator 12 and the second liquid. Figure 1 The gas processing device 100 shown is the same.

[0081] The gas treatment device 200 and the gas treatment device 300 can recover high-concentration acidic compounds from the treated gas containing acidic compounds, similar to the gas treatment device 100. In addition, the degradation of the used treatment liquid can be suppressed, and the treatment liquid can be used for a long time to recover the acidic compounds.

[0082] As other devices for implementing the gas treatment method, for example, Figures 4 to 8 The gas treatment device shown uses a device other than the heater 13 to carry out the deoxidation step.

[0083] Gas processing device 400 Figure 4As shown, a pressure reducer 17 is provided. The pressure reducer 17 is connected to the second liquid flow path 36. A valve 45 is provided at a position upstream of the pressure reducer 17 in the second liquid flow path 36. An oxygen discharge passage 41 for discharging oxygen (oxygen derived from dissolved oxygen) removed from the second liquid in the pressure reducer 17 is connected to the pressure reducer 17. A compressor 46 is provided at a position downstream of the pressure reducer 17 in the oxygen discharge passage 41. By reducing the opening of the valve 45 and decompressing the pressure in the pressure reducer 17 by the compressor 46, dissolved oxygen is removed from the second liquid supplied to the second liquid flow path 36. That is, the decompression treatment as the deoxygenation treatment is performed on the second liquid. The pressure reducer 17 is a processing unit for decompressing the second liquid. The compressor 46 is not particularly limited, and a centrifugal compressor or the like can be used. The oxygen (oxygen derived from dissolved oxygen) removed from the second liquid by the deoxygenation treatment flows to the release passage 51 via the oxygen discharge passage 41. In addition, the second liquid after the deoxygenation treatment is mixed with the first liquid flowing in the first liquid flow path 35 through the second liquid supply channel 42. A pump 43 is provided on the first liquid flow path 35. The mixed liquid of the first liquid and the second liquid after the deoxygenation treatment is introduced into the releaser 14 through the first flow path 21. In addition to performing the deoxygenation treatment in the pressure reducer 17, the gas treatment device 400 is also Figure 1 The gas processing device 100 shown is the same.

[0084] Gas processing device 500 Figure 5 The ultrasonic irradiator 18 is shown. The ultrasonic irradiator 18 is connected to the second liquid flow path 36. By irradiating the second liquid with ultrasonic waves using the ultrasonic irradiator 18, dissolved oxygen is removed from the second liquid supplied to the second liquid flow path 36. That is, the second liquid is subjected to the ultrasonic irradiation treatment as the deoxygenation treatment. The ultrasonic irradiator 18 is a treatment unit that irradiates ultrasonic waves to the second liquid. The ultrasonic irradiator 18 can use a general ultrasonic generator or the like. The oxygen (oxygen derived from dissolved oxygen) removed from the second liquid by the deoxygenation treatment flows to the release channel 51 via the oxygen exhaust channel 41. In addition, the second liquid after the deoxygenation treatment is mixed with the first liquid flowing in the first liquid flow path 35 via the second liquid supply channel 42. The mixed liquid of the first liquid and the second liquid after the deoxygenation treatment is introduced into the releaser 14 via the first flow path 21. In addition to performing the deoxygenation treatment using the ultrasonic irradiator 18, the gas treatment device 500 also has the following features: Figure 1 The gas processing device 100 shown is the same.

[0085] Gas processing device 600 Figure 6As shown, the absorber 11 is provided with a gas-liquid contact part 19. The gas-liquid contact part 19 is connected to the second liquid flow path 36. A functional material 61 is provided inside the gas-liquid contact part 19. The second liquid flowing in the gas-liquid contact part 19 contacts the functional material 61. In addition, the gas-liquid contact part 19 is provided with a first hydrogen supply part 62. The first hydrogen supply part 62 can supply hydrogen to the second liquid in the gas-liquid contact part 19 by supplying hydrogen to the gas-liquid contact part 19. As the functional material 61, for example, a filling material (the same filling material as the filling material arranged in the absorber 11, etc.) and a precious metal catalyst can be cited. In addition, the functional material 61 may not be provided. When a precious metal catalyst is used as the functional material 61, the second liquid is contacted with the precious metal catalyst while the first hydrogen supply part 62 supplies hydrogen to the second liquid. That is, the catalyst contact treatment as the deoxidation treatment is performed on the second liquid. By this operation, dissolved oxygen is removed from the second liquid supplied by the second liquid flow path 36. That is, the catalyst contact treatment as the deoxygenation treatment is performed on the second liquid. In addition, even in the case where a material other than a precious metal catalyst (e.g., a filling material) is used as the functional material 61 and in the case where the functional material 61 is not provided (even in the case where a precious metal catalyst is used as the functional material 61), dissolved oxygen is removed from the second liquid supplied by the second liquid flow path 36 by supplying hydrogen to the second liquid by the first hydrogen supply unit 62. That is, the hydrogen supply treatment as the deoxygenation treatment is performed on the second liquid. Compared with the hydrogen supply treatment, the catalyst contact treatment removes dissolved oxygen from the second liquid better. The precious metal catalyst can use the above-mentioned precious metal catalyst, etc. The first hydrogen supply unit 62 is not particularly limited as long as it can supply hydrogen.

[0086] In addition, the releaser 14 is provided with a second hydrogen supply unit 64 and a second heating unit 65. The second hydrogen supply unit 64 can supply hydrogen to the treatment liquid in the releaser 14 by supplying hydrogen to the releaser 14. The second heating unit 65 can release the acidic compound from the treatment liquid by heating the treatment liquid in the releaser 14. By supplying hydrogen to the treatment liquid in the releaser 14 by the second hydrogen supply unit 64, the temperature (regeneration temperature) of the treatment liquid that can release the acidic compound from the treatment liquid (the first liquid and the second liquid) can be lowered. Since the regeneration temperature can be lowered in this way, the heating temperature of the treatment liquid by the second heating unit 65 can be lowered. In addition, in the case of adopting a treatment unit that supplies hydrogen to the second liquid while bringing the second liquid into contact with a precious metal catalyst, the hydrogen supplied to the releaser 14 can also be supplied from the first hydrogen supply unit 62 that supplies hydrogen in the hydrogen supply treatment or the catalyst contact treatment. That is, the first hydrogen gas supply unit 62 and the second hydrogen gas supply unit 64 may be the same.

[0087] Furthermore, since hydrogen is also supplied to the releaser 14, it is also possible to provide not only the noble metal catalyst in the gas-liquid contact section 19 but also Figure 7 Like the gas treatment device 700 shown in the figure, the emitter 14 is also provided with a precious metal catalyst 66 .

[0088] In the gas treatment device 600 and the gas treatment device 700, the oxygen (oxygen derived from dissolved oxygen) removed from the second liquid by the deoxygenation treatment flows to the release channel 51 through the oxygen exhaust channel 41. In addition, the second liquid after the deoxygenation treatment is mixed with the first liquid flowing in the first liquid flow path 35 through the second liquid supply channel 42. The mixed liquid of the first liquid and the second liquid after the deoxygenation treatment is introduced into the releaser 14 through the first flow path 21. The gas treatment device 600 and the gas treatment device 700 are similar to the gas treatment device 600 and the gas treatment device 700 except that the deoxygenation treatment is performed in the gas-liquid contact part 19 and the releaser 14 is changed to the above-mentioned structure. Figure 1 The second hydrogen gas supply unit 64 is not limited to Figure 6 The gas processing device 600 and Figure 7 The gas treatment device 700 shown in the figure can also be provided in the releaser 14 in other gas treatment devices. By providing the second hydrogen supply unit 64, as described above, hydrogen is supplied from the second hydrogen supply unit 64 to the treatment liquid in the releaser 14, thereby lowering the temperature (regeneration temperature) of the treatment liquid that can release the acidic compound from the treatment liquid (the first liquid and the second liquid).

[0089] Gas processing device 800 Figure 8 The deoxidizer contact section 20 is shown. The deoxidizer contact section 20 is connected to the second liquid flow path 36. By bringing the second liquid into contact with the deoxidizer contact section 20, dissolved oxygen is removed from the second liquid supplied from the second liquid flow path 36. That is, the second liquid is subjected to the deoxidizer contact treatment as the deoxidation treatment. The deoxidizer contact section 20 is a treatment section that brings the second liquid into contact with a deoxidizer. After the second liquid is subjected to the deoxidation treatment, a mixed liquid of the first liquid and the second liquid subjected to the deoxidation treatment is introduced into the releaser 14. In addition, in the deoxidizer contact treatment, the amount of oxygen (oxygen derived from dissolved oxygen) removed from the second liquid is small, so it does not need to flow out to the release channel through the oxygen exhaust channel. In addition, the gas treatment device 800 and Figure 1 The gas treatment device 800 is similar to the gas treatment device 100 shown in FIG. 1 , and may also be provided with an oxygen exhaust passage. The gas treatment device 800 is similar to the gas treatment device 100 shown in FIG. 1 , except that the gas treatment device 800 does not have the oxygen exhaust passage and performs the deoxidation treatment in the deoxidizer contact portion 20. Figure 1 The gas processing device 100 shown is the same.

[0090] Each of the gas treatment devices 200, 300, 400, 500, 600, 700 and 800 can recover high-concentration acidic compounds from the treated gas containing acidic compounds, similar to the gas treatment device 100. In addition, the degradation of the used treatment liquid can be suppressed, and the treatment liquid can be used for the recovery of the acidic compounds for a long time.

[0091] As described above, this specification discloses the technologies of various embodiments, and the main technologies are summarized as follows.

[0092] A gas treatment method according to one aspect of the present invention comprises: a step of bringing a treated gas containing an acidic compound that generates an acid by dissolving in water into contact with a treatment liquid that undergoes phase separation by absorbing the acidic compound, thereby allowing the treatment liquid to absorb the acidic compound; a step of separating the treatment liquid that undergoes phase separation by absorbing the acidic compound into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound, into a first liquid that mainly comprises the first phase portion and a second liquid that mainly comprises the second phase portion; a step of deoxygenating the separated second liquid; and a step of releasing the acidic compound from the first liquid and the second liquid by heating the first liquid together with the deoxygenated second liquid.

[0093] According to this configuration, it is possible to suppress the degradation of the treatment liquid used, and to separate and recover the acidic compound over a long period of time. This is considered to be due to the following reasons.

[0094] It is considered that the deterioration of the treatment liquid caused by long-term separation and recovery of the acidic compound is the deterioration of the components constituting the first phase (the components mainly included in the first phase) as described above.

[0095] As the degradation, firstly, there can be cited degradation caused by the components constituting the first phase portion (the components mainly contained in the first phase portion, such as amine compounds) being heated and deteriorating, that is, thermal degradation. As the treatment liquid, if a treatment liquid that is phase-separated into the first phase portion and the second phase portion by absorbing an acidic compound as described above is used, the regeneration temperature of the treatment liquid can be lowered compared to the case of using other treatment liquids (treatment liquids that are not phase-separated). That is, even if the heating temperature of the treatment liquid that absorbs the acidic compound is lowered, the acidic compound can be released from the treatment liquid. Based on this, it is believed that the thermal degradation of the components constituting the first phase portion (the components mainly contained in the first phase portion) can be suppressed. Therefore, it is believed that the degradation caused by the heating of the treatment liquid, that is, thermal degradation, can be suppressed.

[0096] As the degradation, in addition to the thermal degradation, there can be cited degradation in which the components constituting the first phase portion (the components mainly contained in the first phase portion) are oxidized and deteriorated by oxygen (dissolved oxygen) dissolved in the treatment liquid, that is, oxidative degradation. In the case of using a treatment liquid that is phase-separated into the first phase portion and the second phase portion by absorbing an acidic compound, as described above, since thermal degradation is suppressed, it is believed that the oxidative degradation has a great influence on the degradation of the treatment liquid. In order to suppress the oxidative degradation that is believed to have a great influence, the present inventors focused on reducing the dissolved oxygen in the treatment liquid by deoxygenating the treatment liquid. At this time, deoxygenation of the entire treatment liquid and deoxygenation of the first liquid mainly containing the first phase portion (containing a large amount of components that are the object of oxidative degradation) are also studied. The present inventors have further conducted various studies and found that the second phase portion having a relatively low acid compound content has a lower polarity than the first phase portion, and therefore, the amount of oxygen (dissolved oxygen) dissolved in the second phase portion is greater than that in the first phase portion. Based on this, the present inventors found that the oxidative degradation of the components constituting the first phase portion (the components mainly contained in the first phase portion) can be effectively suppressed by performing the deoxidation treatment on the second liquid mainly containing the second phase portion. That is, the present inventors found that the oxidative degradation of the components constituting the first phase portion (the components mainly contained in the first phase portion) can be effectively suppressed by performing the deoxidation treatment on the second liquid instead of performing the deoxidation treatment on the first liquid mainly containing the components that are subject to oxidative degradation in large quantities.

[0097] As described above, by performing the deoxidation treatment on the second liquid mainly including the second phase portion, it is considered that the oxidative degradation of the components constituting the first phase portion (the components mainly included in the first phase portion) can be suppressed. Therefore, it is considered that the degradation (oxidative degradation) caused by the oxidation of the treatment liquid can be suppressed. It is considered that the oxidative degradation can be effectively suppressed by performing the deoxidation treatment on the second liquid mainly including the second phase portion instead of performing the deoxidation treatment on the entire treatment liquid.

[0098] In addition, generally speaking, when treating an oxidizing atmosphere gas such as exhaust gas, oxidative degradation is more problematic than thermal degradation. From this point of view, it is believed that being able to effectively suppress oxidative degradation is conducive to effectively suppressing degradation of the treatment liquid used.

[0099] Furthermore, in the gas treatment method, the deoxidation treatment is performed on the second liquid before the first liquid and the second liquid are mixed. Therefore, the deoxidation treatment is performed on the second liquid which is a part of the treatment liquid before the treatment liquid is heated to release the acidic compounds from the treatment liquid. Therefore, when the treatment liquid is heated to release the acidic compounds from the treatment liquid, the treatment liquid has become a treatment liquid that has been deoxidized. The higher the temperature, the more likely it is to cause oxidative degradation. Therefore, it is believed that by performing the deoxidation treatment on the treatment liquid before mixing with the first liquid, that is, the second liquid, and thus performing the deoxidation treatment before heating to release the acidic compounds from the treatment liquid, oxidative degradation can be effectively suppressed.

[0100] Based on the above reasons, it is believed that the thermal degradation of the treatment liquid can be suppressed, and the oxidative degradation of the treatment liquid can also be effectively suppressed. Therefore, it is believed that the degradation of the treatment liquid used can be suppressed, and the acidic compounds can be separated and recovered continuously for a long time. In other words, it is believed that the acidic compounds can be separated and recovered continuously for a long time without replenishing or replacing the treatment liquid.

[0101] Furthermore, in the gas treatment method, preferably, the treatment liquid comprises water, an amine compound and an organic solvent, the content of the amine compound in the first phase portion is higher than the content of the amine compound in the second phase portion, and the content of the organic solvent in the second phase portion is higher than the content of the organic solvent in the first phase portion.

[0102] According to this configuration, the degradation of the treatment liquid used can be further suppressed, and the acidic compound can be separated and recovered for a longer period of time.

[0103] Furthermore, in the gas treatment method, preferably, the deoxidation treatment is at least one selected from the group consisting of a treatment of heating the second liquid, a treatment of contacting the second liquid with a deoxidizing agent, a treatment of decompressing the second liquid, and a treatment of irradiating the second liquid with ultrasonic waves.

[0104] According to this configuration, the dissolved oxygen can be removed well from the second liquid by the deoxygenation treatment, and the degradation of the treatment liquid used can be further suppressed. Therefore, the acidic compound can be separated and recovered continuously for a longer period of time.

[0105] Furthermore, in the gas treatment method, it is preferable that the deoxidation treatment is a hydrogen supply treatment of supplying hydrogen gas to the second liquid.

[0106] According to this configuration, the deoxygenation treatment can effectively remove dissolved oxygen from the second liquid. The reason is believed to be that the oxygen partial pressure decreases by supplying hydrogen to the second liquid, and deoxygenation is performed based on the decrease in the oxygen partial pressure. By effectively removing dissolved oxygen from the second liquid, the deterioration of the treatment liquid used can be further suppressed. Therefore, the acidic compounds can be further separated and recovered continuously for a long time.

[0107] Furthermore, in the gas treatment method, it is more preferable that the deoxidation treatment is a treatment of bringing the second liquid into contact with a noble metal catalyst while supplying hydrogen gas to the second liquid in the hydrogen supply treatment.

[0108] According to this configuration, the deoxygenation treatment can better remove dissolved oxygen from the second liquid. The reason is believed to be that deoxygenation is not only performed by the above-mentioned decrease in oxygen partial pressure, but also the presence of the noble metal catalyst promotes the reaction of reducing oxygen with hydrogen (the reaction of generating water from hydrogen and oxygen). In addition to deoxygenation by the hydrogen supply treatment, the second liquid supplied with hydrogen is brought into contact with the noble metal catalyst for deoxygenation, thereby being able to better remove dissolved oxygen from the second liquid, and being able to further suppress the deterioration of the treatment liquid used. Therefore, it is possible to further separate and recover the acidic compounds continuously for a long time.

[0109] Furthermore, in the gas treatment method, it is preferable that hydrogen gas is brought into contact with the first liquid and the second liquid when the acidic compound is released from the first liquid and the second liquid.

[0110] According to this configuration, the degradation of the treatment liquid used can be further suppressed, the acidic compound can be separated and recovered for a longer period of time, and the energy required for separating and recovering the acidic compound can be reduced. This is considered to be due to the following reasons.

[0111] When the acidic compound is released from the first liquid and the second liquid, the temperature (regeneration temperature) of the treatment liquid at which the acidic compound can be released from the treatment liquid (the first liquid and the second liquid) can be lowered by bringing the first liquid and the second liquid into contact with hydrogen. Therefore, it is considered that not only the thermal degradation of the treatment liquid can be further suppressed, but also the energy required for separating and recovering the acidic compound can be reduced.

[0112] In addition, as the deoxidation treatment, in the case of a deoxidation treatment using hydrogen such as the hydrogen supply treatment, the gas supplied during the treatment and the gas used when releasing the acidic compound are both hydrogen. Therefore, their supply can be easily performed. For example, the hydrogen used in the deoxidation treatment and the hydrogen used when releasing the acidic compound can also be supplied from the same hydrogen supply unit.

[0113] In addition, a gas treatment device according to another aspect of the present invention includes: an absorber for bringing a treated gas containing an acidic compound that generates an acid by dissolving in water into contact with a treatment liquid that undergoes phase separation by absorbing the acidic compound, thereby allowing the treatment liquid to absorb the acidic compound; a separator for separating the treatment liquid, which has been subjected to phase separation into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound by absorbing the acidic compound in the absorber, into a first liquid mainly containing the first phase portion and a second liquid mainly containing the second phase portion; a deoxygenation treatment section for deoxygenating the separated second liquid; and a releaser for releasing the acidic compound from the first liquid and the second liquid by heating the first liquid together with the deoxygenated second liquid.

[0114] According to this configuration, as described above, since the regeneration temperature of the treatment liquid can be lowered, it is considered that the thermal degradation of the components constituting the first phase portion in the releaser (the components mainly contained in the first phase portion, such as amine compounds) can be suppressed. In addition, by the deoxidation treatment of the deoxidation treatment section, the oxidative degradation of the components constituting the first phase portion can also be effectively suppressed as described above. Therefore, according to the gas treatment device, the degradation of the treatment liquid used can be suppressed, and the acidic compounds can be separated and recovered for a long time.

[0115] Furthermore, in the gas treatment device, preferably, the treatment liquid comprises water, an amine compound and an organic solvent, the content of the amine compound in the first phase portion is higher than the content of the amine compound in the second phase portion, and the content of the organic solvent in the second phase portion is higher than the content of the organic solvent in the first phase portion.

[0116] According to this configuration, the degradation of the treatment liquid used can be further suppressed, and the acidic compound can be separated and recovered for a longer period of time.

[0117] Furthermore, in the gas treatment device, preferably, the deoxidation treatment section is at least one selected from the group consisting of a treatment section for heating the second liquid, a treatment section for bringing the second liquid into contact with a deoxidizer, a treatment section for decompressing the second liquid, and a treatment section for irradiating the second liquid with ultrasonic waves.

[0118] According to this configuration, the deoxygenation treatment in the deoxygenation treatment section can effectively remove dissolved oxygen from the second liquid, and deterioration of the treatment liquid used can be further suppressed. Therefore, the acidic compound can be separated and recovered continuously for a long period of time.

[0119] Furthermore, in the gas treatment device, preferably, the deoxidation treatment section includes a hydrogen gas supply section that supplies hydrogen gas to the second liquid.

[0120] According to this configuration, the deoxygenation treatment in the deoxygenation treatment section can effectively remove dissolved oxygen from the second liquid, and deterioration of the treatment liquid used can be further suppressed. Therefore, the acidic compound can be separated and recovered continuously for a long period of time.

[0121] Furthermore, in the gas treatment device, it is more preferable that the deoxidation treatment section further includes a noble metal catalyst, and the deoxidation treatment section brings the second liquid into contact with the noble metal catalyst while supplying hydrogen gas from the hydrogen gas supply section to the second liquid.

[0122] According to this configuration, in addition to deoxygenation by supplying hydrogen to the second liquid, deoxygenation is also performed by bringing the second liquid supplied with hydrogen into contact with a noble metal catalyst, thereby enabling dissolved oxygen to be removed more effectively from the second liquid. Therefore, deterioration of the treatment liquid used can be further suppressed, and acidic compounds can be separated and recovered continuously for a longer period of time.

[0123] Furthermore, the gas processing device preferably further includes a hydrogen gas supply unit configured to supply hydrogen gas to the release device so that the hydrogen gas contacts the first liquid and the second liquid.

[0124] According to this formation, in the releaser, the temperature (regeneration temperature) of the treatment liquid that can release the acidic compound from the treatment liquid (the first liquid and the second liquid) can be reduced. Therefore, it is believed that not only the thermal degradation of the treatment liquid can be further suppressed, but also the energy required for separation and recovery of the acidic compound can be reduced. Therefore, the degradation of the treatment liquid used can be further suppressed, the acidic compound can be separated and recovered for a longer period of time, and in addition, the energy required for separation and recovery of the acidic compound can be reduced. In addition, if the hydrogen supply unit is used as the deoxidation treatment unit, these hydrogens can be easily supplied. For example, the hydrogen used in the deoxidation treatment unit and the hydrogen used in the releaser can also be supplied from the same hydrogen supply unit.

[0125] According to the present invention, it is possible to provide a gas treatment method and a gas treatment apparatus capable of suppressing the deterioration of a treatment liquid used and capable of separating and recovering acidic compounds over a long period of time.

[0126] This application is based on Japanese invention patent application No. 2022-140628 filed on September 5, 2022, and the contents are included in this application.

[0127] In order to describe the present invention, the present invention has been appropriately and fully described above through the embodiments, but it should be recognized that those skilled in the art can easily change and / or improve the above embodiments. Therefore, the changed embodiments or improved embodiments implemented by those skilled in the art, as long as they do not deviate from the protection scope of the claims recorded in the claims, the changed embodiments or the improved embodiments can be interpreted as being included in the protection scope of the claims.

[0128] Industrial Applicability

[0129] According to the present invention, it is possible to provide a gas treatment method and a gas treatment apparatus capable of suppressing the deterioration of a treatment liquid used and capable of separating and recovering acidic compounds over a long period of time.

Claims

1. A gas treatment method, characterized in that include: A step of bringing a gas to be treated containing an acidic compound that generates an acid by dissolving in water into contact with a treatment liquid that undergoes phase separation by absorbing the acidic compound, thereby allowing the treatment liquid to absorb the acidic compound; The step of separating the treatment liquid, which is subjected to phase separation into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound by allowing the treatment liquid to absorb the acidic compound, into a first liquid mainly containing the first phase portion and a second liquid mainly containing the second phase portion; The step of deoxygenating the separated second liquid; as well as A step of releasing the acidic compound from the first liquid and the second liquid by heating the first liquid together with the second liquid subjected to the deoxidation treatment.

2. The gas treatment method according to claim 1, characterized in that: The treatment liquid comprises water, an amine compound and an organic solvent. The content of the amine compound in the first phase is higher than the content of the amine compound in the second phase, The content of the organic solvent in the second phase is higher than the content of the organic solvent in the first phase.

3. The gas treatment method according to claim 1 or 2, characterized in that: The deoxidation treatment is at least one selected from the group consisting of a treatment of heating the second liquid, a treatment of bringing the second liquid into contact with a deoxidizing agent, a treatment of decompressing the second liquid, and a treatment of irradiating the second liquid with ultrasonic waves.

4. The gas treatment method according to claim 1 or 2, characterized in that: The deoxidation treatment is a hydrogen supply treatment of supplying hydrogen gas to the second liquid.

5. The gas processing method according to claim 4, characterized in that: The deoxidation treatment is a treatment of bringing the second liquid into contact with a precious metal catalyst while supplying hydrogen gas to the second liquid in the hydrogen gas supplying treatment.

6. The gas processing method according to claim 3, characterized in that: When the acidic compound is released from the first liquid and the second liquid, hydrogen gas is brought into contact with the first liquid and the second liquid.

7. The gas processing method according to claim 4, characterized in that: When the acidic compound is released from the first liquid and the second liquid, hydrogen gas is brought into contact with the first liquid and the second liquid.

8. The gas processing method according to claim 5, characterized in that: When the acidic compound is released from the first liquid and the second liquid, hydrogen gas is brought into contact with the first liquid and the second liquid.

9. A gas processing device, characterized in that include: an absorber for contacting a gas to be treated containing an acidic compound that generates an acid by dissolving in water with a treatment liquid that undergoes phase separation by absorbing the acidic compound, thereby allowing the treatment liquid to absorb the acidic compound; a separator for separating the treated liquid, which is phase-separated into a first phase portion having a relatively high content of the acidic compound and a second phase portion having a relatively low content of the acidic compound by allowing the treated liquid to absorb the acidic compound in the absorber, into a first liquid mainly containing the first phase portion and a second liquid mainly containing the second phase portion; A deoxygenation treatment unit, which performs deoxygenation treatment on the separated second liquid; as well as The releaser releases the acidic compound from the first liquid and the second liquid by heating the first liquid together with the second liquid subjected to the deoxidation treatment.

10. The gas processing device according to claim 9, characterized in that: The treatment liquid comprises water, an amine compound and an organic solvent. The content of the amine compound in the first phase is higher than the content of the amine compound in the second phase, The content of the organic solvent in the second phase is higher than the content of the organic solvent in the first phase.

11. The gas processing device according to claim 9 or 10, characterized in that: The deoxidation treatment section is at least one selected from the group consisting of a treatment section that heats the second liquid, a treatment section that brings the second liquid into contact with a deoxidizer, a treatment section that decompresses the second liquid, and a treatment section that irradiates the second liquid with ultrasonic waves.

12. The gas processing device according to claim 9 or 10, characterized in that: The deoxidation treatment unit includes a hydrogen gas supply unit that supplies hydrogen gas to the second liquid.

13. The gas processing device according to claim 12, characterized in that: The deoxidation treatment unit further includes a noble metal catalyst, The deoxidation treatment section brings the second liquid into contact with the precious metal catalyst while supplying hydrogen gas from the hydrogen gas supplying section to the second liquid.

14. The gas processing device according to claim 11, characterized in that Also includes: The hydrogen gas supply unit supplies hydrogen gas to the release device so that the hydrogen gas contacts the first liquid and the second liquid.

15. The gas processing device according to claim 12, characterized in that Also includes: The hydrogen gas supply unit supplies hydrogen gas to the release device so that the hydrogen gas contacts the first liquid and the second liquid.

16. The gas processing device according to claim 13, characterized in that Also includes: The hydrogen gas supply unit supplies hydrogen gas to the release device so that the hydrogen gas contacts the first liquid and the second liquid.

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