阅读说明：本技术 气体处理方法以及气体处理装置 (Gas processing method and gas processing apparatus ) 是由 前田基秀 岸本启 中西健 町田洋 山口毅 则永行庸 于 2020-04-10 设计创作，主要内容包括：本发明一个方面涉及气体处理方法,其包括以下步骤：吸收步骤,通过使含有二氧化碳和硫化合物的被处理气体与通过吸收二氧化碳而进行相分离的吸收液接触,从而使所述吸收液吸收所述二氧化碳和所述硫化合物；以及第一释放步骤,通过将与所述被处理气体接触后的吸收液加热至被吸收到所述吸收液中的二氧化碳从所述吸收液释放的温度以上且低于被吸收到所述吸收液中的硫化合物从所述吸收液释放的温度,从而使所述二氧化碳从所述吸收液释放出来。(One aspect of the present invention relates to a gas treatment method comprising the steps of: an absorption step of bringing a gas to be treated containing carbon dioxide and a sulfur compound into contact with an absorption liquid that is phase-separated by absorbing carbon dioxide, thereby causing the absorption liquid to absorb the carbon dioxide and the sulfur compound; and a first release step of heating the absorbent that has been brought into contact with the gas to be treated to a temperature that is equal to or higher than a temperature at which carbon dioxide absorbed in the absorbent is released from the absorbent and lower than a temperature at which sulfur compounds absorbed in the absorbent are released from the absorbent, thereby releasing the carbon dioxide from the absorbent.)

1. A method of gas treatment, comprising the steps of:

an absorption step of bringing a gas to be treated containing carbon dioxide and a sulfur compound into contact with an absorption liquid that is phase-separated by absorbing carbon dioxide, thereby causing the absorption liquid to absorb the carbon dioxide and the sulfur compound; and

a first release step of heating the absorbent that has been brought into contact with the gas to be treated to a temperature that is equal to or higher than a temperature at which carbon dioxide absorbed in the absorbent is released from the absorbent and lower than a temperature at which sulfur compounds absorbed in the absorbent are released from the absorbent, thereby releasing the carbon dioxide from the absorbent.

2. The gas treatment method according to claim 1, further comprising:

a first recovery step of adsorbing and recovering the sulfur compound from the absorbent after the first release step after the carbon dioxide is released from the absorbent in the first release step.

3. The gas treatment method according to claim 1, further comprising:

a second releasing step of heating the absorbent after the first releasing step to a temperature equal to or higher than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent after the carbon dioxide is released from the absorbent in the first releasing step, thereby releasing the sulfur compound from the absorbent.

4. The gas treatment method according to claim 3, further comprising:

a second recovery step of adsorbing and recovering the sulfur compounds, which are not released in the second release step, from the absorbent liquid after the second release step, after the sulfur compounds are released from the absorbent liquid in the second release step.

5. The gas treatment method according to claim 3,

the absorption liquid is an absorption liquid that also undergoes phase separation by absorbing the sulfur compounds,

in the absorption step, the absorption liquid phase is separated into a first phase portion and a second phase portion by absorbing the carbon dioxide and the sulfur compound,

the content ratio of the carbon dioxide and the sulfur compound in the first phase portion is higher than the content ratio of the carbon dioxide and the sulfur compound in the second phase portion,

the second release step is a step of heating the first phase portion after the carbon dioxide is released from the absorbing liquid in the first release step.

6. The gas treatment method according to claim 1,

the absorption liquid is an absorption liquid that also undergoes phase separation by absorbing the sulfur compounds,

in the absorption step, the absorption liquid phase is separated into a first phase portion and a second phase portion by absorbing the carbon dioxide and the sulfur compound,

the content ratio of the carbon dioxide and the sulfur compound in the first phase portion is higher than the content ratio of the carbon dioxide and the sulfur compound in the second phase portion,

the gas treatment method further comprises: a step of discarding at least a part of the first phase portion after the first releasing step, and using the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is brought into contact with the gas to be treated in the absorbing step.

7. A gas processing apparatus characterized by comprising:

an absorber that causes an absorption liquid, which is phase-separated by absorbing carbon dioxide, to absorb carbon dioxide and a sulfur compound by bringing a gas to be treated containing the carbon dioxide and the sulfur compound into contact with the absorption liquid; and

a first releaser that releases the carbon dioxide from the absorbing liquid by heating the absorbing liquid that has been contacted with the gas to be treated to a temperature that is equal to or higher than a temperature at which the carbon dioxide absorbed into the absorbing liquid is released from the absorbing liquid and lower than a temperature at which the sulfur compound absorbed into the absorbing liquid is released from the absorbing liquid.

8. The gas processing apparatus of claim 7, further comprising:

a first regenerator that adsorbs and recovers the sulfur compound from the absorbing liquid after the carbon dioxide is released in the first releaser.

9. The gas processing apparatus according to claim 8,

the first reclaimer is provided with an adsorbent capable of adsorbing the sulfur compound,

the adsorbent includes at least one selected from the group consisting of a metal adsorbent, a resin adsorbent, an inorganic adsorbent, and a physical adsorbent.

10. The gas processing apparatus according to claim 8,

the first retractor is a horizontal type in which the longitudinal direction is horizontal, or a vertical type in which the longitudinal direction is vertical.

11. The gas processing apparatus of claim 7, further comprising:

a second releaser for releasing the sulfur compound from the absorbent by heating the absorbent having released the carbon dioxide from the first releaser to a temperature equal to or higher than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent.

12. The gas processing apparatus of claim 11, further comprising:

a second recoverer that adsorbs and recovers the sulfur compound that is not released in the second releaser from the absorbent after the sulfur compound is released in the second releaser.

13. The gas processing apparatus according to claim 11,

the absorption liquid is an absorption liquid that also undergoes phase separation by absorbing the sulfur compounds,

in the absorber, by absorbing the carbon dioxide and the sulfur compounds, whereby the absorption liquid phase separates into a first phase portion and a second phase portion,

the content ratio of the carbon dioxide and the sulfur compound in the first phase portion is higher than the content ratio of the carbon dioxide and the sulfur compound in the second phase portion,

the second releaser heats the first phase portion after the carbon dioxide is released from the absorbing liquid in the first releaser.

14. The gas processing apparatus according to claim 12,

the second recovery device is provided with an adsorbent capable of adsorbing the sulfur compound,

the adsorbent includes at least one selected from the group consisting of a metal adsorbent, a resin adsorbent, an inorganic adsorbent, and a physical adsorbent.

15. The gas processing apparatus according to claim 12,

the second recovery unit is a horizontal type mounted so that the longitudinal direction thereof is the horizontal direction, or a vertical type mounted so that the longitudinal direction thereof is the plumb direction.

16. The gas processing apparatus according to claim 7,

the absorption liquid is an absorption liquid that also undergoes phase separation by absorbing the sulfur compounds,

in the absorber, by absorbing the carbon dioxide and the sulfur compounds, whereby the absorption liquid phase separates into a first phase portion and a second phase portion,

the content ratio of the carbon dioxide and the sulfur compound in the first phase portion is higher than the content ratio of the carbon dioxide and the sulfur compound in the second phase portion,

the gas processing apparatus further includes: a mechanism that discards at least a part of the first phase portion after the carbon dioxide is released from the absorbing liquid in the first releaser, and uses the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is in contact with the gas to be treated in the absorber.

Technical Field

The present invention relates to a gas processing method and a gas processing apparatus.

Background

Carbon dioxide (CO) contained in exhaust gas from power stations, by-product gas from blast furnaces, and the like₂) Large volume gas (containing CO)₂Gas) recovery of CO₂There are various methods of (2), and examples thereof include a chemical absorption method such as an amine absorption method. The chemical absorption method comprises using an alkaline aqueous solution such as an amine aqueous solution as an absorption liquid to make CO contained₂The gas is contacted with the absorption liquid to absorb CO₂Then, heating absorbs CO₂To release CO from the absorption liquid₂Thereby recovering the released CO₂The method of (1).

On the other hand, the absorption liquid in the chemical absorption method usually also absorbs CO₂Other acidic components. Specifically, the absorption liquid absorbs not only CO₂In addition, it is absorbed in the CO-containing gas₂SO contained as an impurity in a gas_xAnd H₂S, and the like. Thus, absorbing CO₂CO in gas₂CO released from the absorption liquid₂Sulfur compounds are mixed in. Further, in the chemical absorption method, the CO is removed from the gas containing CO as the treatment target gas₂Among the components contained in the gas, only the components absorbed by the absorbing liquid are recovered, and the components not absorbed by the absorbing liquid are not recovered. Therefore, in the chemical absorption method, although CO is present₂But the sulfur compounds absorbed by the absorbing liquid are also preferentially recovered, and the concentration of the sulfur compounds in the recovered gas is higher than the concentration of the sulfur compounds in the treated gas.

CO being recovered₂The method is used in various fields such as synthesis of chemicals such as urea, production of dry ice, Recovery and Storage of Carbon dioxide (CCS), and Enhanced Oil Recovery (EOR). As recovered CO₂In any of the methods, it is required to reduce the CO to be recovered as much as possible₂May cause various problems such as corrosion of the pipe and deactivation of the catalyst. In addition, the sulfur compound promotes an irreversible deterioration reaction of components contained in the absorbing liquid, for example, amines and the like. Therefore, if CO is recovered by the chemical absorption method for a long period of time₂The components contained in the absorption liquid are deteriorated to a great extent, and the amount of the absorption liquid to be discarded increases. Accordingly, the amount of the additional absorbent, that is, the amount of the so-called amine supplement, increases. To reduce the amount of amine make-up, it is also desirable to recover CO by chemical absorption₂Gas processing apparatus (CO)₂Recovery unit) is small.

To meet these requirements, for example, CO is absorbed chemically₂The recovery device is provided with a desulfurization device at the front stage thereof. I.e. by using in the desulfurization unitThe gas from which sulfur oxides are removed is introduced as the CO₂The treated gas of the apparatus is recovered, thereby solving the problems associated with sulfur compounds. Examples of such a technique include a desulfurization and decarbonation method described in patent document 1.

Patent document 1 describes a desulfurization and decarbonation method comprising the following steps: a desulfurization step of contacting a gas containing sulfur oxide and carbon dioxide with an absorption liquid containing an alkaline calcium compound to remove sulfur oxide from the gas; a highly desulfurized gas cooling step of bringing the gas subjected to the desulfurization treatment in the desulfurization step into contact with an alkaline absorbent to further remove sulfur oxides so that the concentration of sulfur oxides in the gas becomes 5ppm or less, and cooling the gas to a temperature of 50 ℃ or less; and a decarbonation step of bringing the gas subjected to the high-desulfurization-gas cooling treatment in the high-desulfurization-gas cooling step into contact with an absorbent containing a basic amine compound, thereby removing carbon dioxide from the gas. Patent document 1 discloses that sulfur oxides contained in a gas after desulfurization treatment are removed to suppress accumulation of sulfur oxides in a decarbonation absorbent, and the amount of amine compounds in the absorbent due to exhaust gas in the decarbonation step can be reduced.

As described above, even in the case of CO produced by the chemical absorption method₂The front stage of the recovery device is provided with a desulfurization device so as to reduce the recovered CO₂The concentration of sulfur compounds in the sulfur-containing compound, but the provision of a desulfurization unit leads to an increase in cost. Therefore, CO is preferred₂The recovery device can recover CO mixed with low concentration of sulfur compounds without using a desulfurization device or the like to remove sulfur compounds such as sulfur oxides from the gas to be treated in advance₂. That is, in the chemical absorption method, it is required that the CO-containing gas containing the sulfur compound or the like is introduced₂The gas is directly treated as the gas to be treated, and high concentration CO can be recovered₂The method of (1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-87828.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a gas treatment method and a gas treatment apparatus capable of recovering carbon dioxide at a high concentration.

One aspect of the present invention relates to a gas treatment method comprising the steps of: an absorption step of bringing a gas to be treated containing carbon dioxide and a sulfur compound into contact with an absorption liquid that is phase-separated by absorbing carbon dioxide, thereby causing the absorption liquid to absorb the carbon dioxide and the sulfur compound; and a first release step of heating the absorbent that has been brought into contact with the gas to be treated to a temperature that is equal to or higher than a temperature at which carbon dioxide absorbed in the absorbent is released from the absorbent and lower than a temperature at which sulfur compounds absorbed in the absorbent are released from the absorbent, thereby releasing the carbon dioxide from the absorbent.

Another aspect of the invention relates to a gas treatment apparatus comprising: an absorber that causes an absorption liquid, which is phase-separated by absorbing carbon dioxide, to absorb carbon dioxide and a sulfur compound by bringing a gas to be treated containing the carbon dioxide and the sulfur compound into contact with the absorption liquid; and a first releaser that releases the carbon dioxide from the absorbent by heating the absorbent that has been contacted with the gas to be treated to a temperature that is equal to or higher than a temperature at which the carbon dioxide absorbed in the absorbent is released from the absorbent and lower than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent.

Drawings

Fig. 1 is a schematic diagram for explaining a gas treatment method according to an embodiment of the present invention.

Fig. 2 is a schematic diagram showing an example of a gas processing apparatus according to an embodiment of the present invention.

Fig. 3 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Fig. 4 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Fig. 5 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Fig. 6 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Fig. 7 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Fig. 8 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Fig. 9 is a schematic view showing another example of the gas processing apparatus according to the embodiment of the present invention.

Detailed Description

The present inventors have conducted various studies and as a result have found that the above object can be achieved by the following invention.

The embodiments according to the present invention will be described below, but the present invention is not limited to these embodiments.

As shown in FIG. 1, the gas treatment method according to the embodiment of the present invention uses carbon dioxide (CO)₂) The absorbing liquid which is subjected to the phase separation by the absorption of (3), and a method for separating and recovering the carbon dioxide from a gas to be treated containing carbon dioxide and a sulfur compound. Fig. 1 is a schematic diagram for explaining a gas treatment method according to the present embodiment. In addition, although Sulfur Oxide (SO) is shown in FIG. 1_x) The sulfur compound is not particularly limited as long as it is a gaseous sulfur compound, and may be, for example, hydrogen sulfide (H)₂S）。

As shown in fig. 1 (a), the gas treatment method brings a gas to be treated containing carbon dioxide and sulfur compounds into contact with an absorbent 11 that undergoes phase separation by absorption of carbon dioxide. Thereby, as shown in fig. 1 (b), the carbon dioxide and the sulfur compound are absorbed by the absorbing liquid 11. The absorption liquid 11 that has absorbed the carbon dioxide and the sulfur compound is phase-separated into a first phase portion 12 and a second phase portion 13. As described above, the carbon dioxide and the sulfur compound are absorbed by bringing the gas to be treated into contact with the absorbing liquid 11The step (2) corresponds to the absorption step. As shown in fig. 1 (b), in the first phase portion 12 and the second phase portion 13 which are phase-separated as described above, carbon dioxide and sulfur compounds may be absorbed in different forms in the respective phases. In FIG. 1A, a primary amine (R-NH) is shown as a component contained in the absorbent 11₂) However, the component is not particularly limited as long as it is a component constituting the absorbing liquid that undergoes phase separation by absorption of carbon dioxide, that is, a component that associates with carbon dioxide and contributes to phase separation of the absorbing liquid. The component is not limited to primary amines, and secondary amines and tertiary amines may be mentioned. In addition, in FIG. 1 (b) and FIG. 1 (c), a primary amine (R-NH) is used₂) The sulfur compound is Sulfur Oxide (SO) as a component contained in the absorbing liquid 11_x) In the case of (2), carbon dioxide and a primary amine (R-NH) are described as an example in each of the first phase portion 12 and the second phase portion 13₂) And sulfur compound and primary amine (R-NH)₂) The association state of (3) is not limited to these.

The gas treatment method is configured to heat the absorbent 11 (the first phase portion 12 and the second phase portion 13) after contact with the gas to be treated after the absorption step to a temperature equal to or higher than a temperature at which carbon dioxide absorbed by the absorbent 11 is released from the absorbent 11 and lower than a temperature at which sulfur compounds absorbed by the absorbent 11 are released from the absorbent 11. By heating as described above, the carbon dioxide is released from the absorbent 11 as shown in fig. 1 (c). As described above, the step of releasing the carbon dioxide from the absorbent 11 by heating the absorbent 11 corresponds to the first release step. Further, as described above, this heating is heating at a temperature lower than the temperature at which the sulfur compounds absorbed by the absorbent 11 are released from the absorbent 11, and therefore, as shown in fig. 1 (c), the sulfur compounds absorbed by the absorbent 11 are kept in a state of being absorbed by the absorbent 11. Even if the gas to be treated contains a gas other than carbon dioxide and sulfur compounds, the gas is not released in the first release step as long as the gas is not absorbed in the absorbing liquid 11 in the absorption step. Therefore, in the first release step, the release of the gas and the sulfur compound which are difficult to be absorbed by the absorbent 11 is sufficiently suppressed. Therefore, the gas treatment method can recover carbon dioxide at a high concentration.

In the gas treatment method, after the first desorption step, the absorbent 11 after the first desorption step may be heated to a temperature equal to or higher than a temperature at which the sulfur compounds absorbed in the absorbent 11 are desorbed from the absorbent 11. Thereby, as shown in fig. 1 (d), sulfur compounds are also released from the absorbent liquid 11. As described above, the step of releasing the sulfur compounds from the absorbent liquid 11 by heating the absorbent liquid 11 corresponds to the second release step. Carbon dioxide and sulfur compounds can be separately recovered by this gas treatment process.

The gas to be treated may be any gas containing carbon dioxide and sulfur compounds, and the gas to be treated may be treated by the gas treatment method, whereby carbon dioxide having a high concentration can be recovered as described above. The gas to be treated may contain a gas other than carbon dioxide and sulfur compounds, and examples of the gas other than carbon oxide and sulfur compounds include a gas such as nitrogen that is difficult to be absorbed by the absorbing liquid 11. Specific examples of the gas to be treated include power station waste gas and blast furnace by-product gas.

The absorbing liquid is an absorbing liquid that undergoes phase separation by absorption of carbon dioxide as described above. The absorbing liquid may be an absorbing liquid that is phase-separated not only by absorption of carbon dioxide but also by absorption of sulfur compounds. Examples of the absorbing liquid include an aqueous solution of an amine compound, which may further contain an organic solvent. That is, the absorbing liquid may be, for example, an alkaline liquid containing an amine compound, an organic solvent, and water.

The amine compound is not limited to the primary amine as described above, and secondary and tertiary amines may be mentioned. Examples of the primary amine include 1, 3-diaminopropane (DAP: solubility reference)Number =14.6 (cal/cm)³）^1/2) 2-aminoethanol (MEA: solubility parameter =14.3 (cal/cm)³）^1/2) DL-2-amino-1-propanol (AP: solubility parameter =13.3 (cal/cm)³）^1/2) 2- (2-aminoethoxy) ethanol (AEE: solubility parameter) =12.7 (cal/cm)³）^1/2) And (R) -4-amino-2-methyl-1-butanol (AMB). Examples of the secondary amine include 2- (methylamino) ethanol (MAE), 2- (ethylamino) ethanol (EAE), and 2- (butylamino) ethanol (BAE). Examples of the tertiary amine include Triethanolamine (TEA), N-Methyldiethanolamine (MDEA), Tetramethylethylenediamine (TEMED), Pentamethyldiethylenetriamine (PMDETA), hexamethyltriethylenetetramine, and bis (2-dimethylaminoethyl) ether. These amine compounds may be used alone or in combination of two or more.

As the organic solvent, there may be mentioned: for example, 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), diethylene glycol dimethyl ether (DEGDME), and the like. These organic solvents may be used alone or in combination of two or more.

The absorbing liquid may contain an ionic liquid or the like in addition to the amine compound, the organic solvent, and water.

When the absorbing liquid is an alkaline liquid containing an amine compound, an organic solvent, and water, the content of the amine compound is preferably 20 to 40% by mass. The content of the organic solvent is preferably 40 to 60% by mass. Preferably, the absorbing liquid contains water. Examples of the absorbing liquid include a liquid containing 30 mass% of the amine compound, 60 mass% of the organic solvent, and 10 mass% of water.

When the absorbing liquid is a basic liquid containing the amine compound, the organic solvent, and water, the solubility parameter of the amine compound and the solubility parameter of the organic solvent preferably satisfy the relationship described later. The solubility parameter was determined by the following formula (1).

δ ＝ ［（ΔH － RT）/V］^1/2 （1）

In the formula (1), δ represents a solubility parameter, Δ H represents a molar latent heat of vaporization, R represents a gas constant, T represents an absolute temperature, and V represents a molar volume. For example, if the solubility parameters of EAE, MAE as amine compounds and DEGDME as an organic solvent are calculated according to formula (1), they are 10.94, 11.58 and 7.75, respectively.

The following description: when the absorbing liquid contains the amine compound, the organic solvent, and the alkaline liquid of water, the absorbing liquid is in a state after absorbing carbon dioxide. As the absorbing liquid, a liquid containing 30 mass% of the amine compound, 60 mass% of the organic solvent, and 10 mass% of water was used, and the state of the absorbing liquid was observed in each combination by changing the combination of the amine compound and the organic solvent. The results are shown in table 1. Table 1 shows the solubility parameter of the amine compound, the solubility parameter of the organic solvent, a value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound, and the state of the absorption liquid after carbon dioxide absorption. "good" in table 1 means: before absorbing carbon dioxide, the liquid phase is separated into two liquid phases by absorbing carbon dioxide. In addition, "immiscible" in table 1 means: the liquid phase is in a liquid state before the absorption of carbon dioxide, and a liquid phase is not formed. In addition, "not to separate" in table 1 means: also a liquid phase after absorption of carbon dioxide. In addition, since the solubility parameter of the amine compound and the solubility parameter of the organic solvent shown in table 1 are only counted one decimal place after the decimal point due to the relation of the significant figures, a value obtained by subtracting the solubility parameter of the organic solvent from the solubility parameter of the amine compound may cause a rounding error and may not be a difference in the solubility parameters shown in table 1.

TABLE 1

As can be seen from table 1, when the absorbing liquid is an alkaline liquid containing an amine compound, an organic solvent, and water, a value (solubility parameter difference) obtained by subtracting a solubility parameter of the organic solvent from a solubility parameter of the amine compound is preferably 1.1 (cal/cm)³）^1/2) Above and 4.2 (cal/cm)³）^1/2) The following. By selecting the amine compound and the organic solvent so that the values fall within the above ranges, the absorbing liquid can absorb carbon dioxide, and become a one-phase state before absorbing carbon dioxide and become a two-phase state after absorbing carbon dioxide. That is, the carbon dioxide is absorbed to form a phase-separated absorption liquid. If the solubility parameter difference is too small, there is a tendency that phase separation does not occur even if carbon dioxide is absorbed by the resulting liquid. Further, if the solubility parameter difference is too large, the resulting liquid tends to be in a two-phase state before absorbing carbon dioxide. In this two-phase state, the organic solvent is not sufficiently miscible with water, and the amine compound is contained more in one phase thereof, for example, an aqueous phase. Even if the gas to be treated is brought into contact with the liquid in such a state, the contact state between the liquid and the gas to be treated becomes uneven, and the absorption efficiency may decrease.

With respect to the absorbing liquid, the minimum temperature (sulfur compound releasable temperature) at which the sulfur compounds absorbed into the absorbing liquid are released from the absorbing liquid is higher than the minimum temperature (CO) at which the carbon dioxide absorbed into the absorbing liquid is released from the absorbing liquid₂Releasable temperature). Further, with respect to the absorbing liquid, the maximum temperature (absorbable temperature) at which the carbon dioxide and the sulfur compound are absorbed by the absorbing liquid is lower than the CO₂The temperature may be released.

For example, it is assumed that an absorption liquid containing 10 mass% of water, and EAE30 mass% of the amine compound and DEGDEE60 mass% of the organic solvent is used, and carbon dioxide (CO) is used₂) And doIs Sulfur Oxide (SO) of the sulfur compound_x) Can absorb temperature and CO when used as the gas to be treated₂The releasable temperature and the sulfur compound releasable temperature are about 60 ℃, about 70 ℃ and about 120 ℃, respectively. Note that these temperatures are values assumed at low pressures close to atmospheric pressure, and these temperatures become higher as the pressure becomes higher. In this case, in the state where the absorbing liquid and the gas to be treated coexist, if the temperature is 60 ℃ or lower, for example, 0 to 60 ℃, carbon dioxide and sulfur oxide are absorbed by the absorbing liquid. That is, the temperature of the absorption liquid in the absorption step is preferably 0 to 60 ℃. Further, if the absorbing liquid that has absorbed carbon dioxide and sulfur oxide is heated to 70 ℃ or higher, carbon dioxide is released, and if it is heated to 120 ℃ or higher, sulfur oxide is also released. Thus, the temperature of the absorbent in the first release step is preferably 70 ℃ or higher and lower than 120 ℃, and the temperature of the absorbent in the second release step is preferably 120 ℃ or higher.

As described above, the absorbing liquid 11 may be an absorbing liquid that is phase-separated not only by the absorption of carbon dioxide but also by the absorption of sulfur compounds. In this case, as shown in fig. 1 (b), the absorption liquid 11 absorbs the carbon dioxide and the sulfur compound to phase-separate into: a first phase portion 12 in which the content of the carbon dioxide and the sulfur compound is relatively high, and a second phase portion 13 in which the content of the carbon dioxide and the sulfur compound is relatively low.

In the second release step, as described above, the absorbing liquid after the carbon dioxide is released from the absorbing liquid in the first release step may be heated. In the second release step, the whole of the absorbing liquid may be heated, but it is preferable to heat the first phase portion after the carbon dioxide is released from the absorbing liquid in the first release step. This step may be, for example, a method of releasing the sulfur compound from the absorbent 11 as shown in fig. 1 (d) by preferentially heating the first phase portion 12 shown in fig. 1 (c) after releasing the carbon dioxide from the absorbent in the first release step. As a method other than this method (another method), there may be mentioned a method in which after the carbon dioxide is released from the absorbent in the first release step, at least a part of the first phase portion 12 shown in fig. 1 (c) is taken out, and the taken-out first phase portion 12 is heated, whereby the first phase portion 12 releases a sulfur compound. As described above, in the second release step, the sulfur compound is released from the absorbing liquid by heating the first phase portion having a relatively high content of the sulfur compound, and therefore, the sulfur compound can be efficiently released from the absorbing liquid.

The gas treatment method may further include a first recovery step of adsorbing and recovering the sulfur compound from the absorbing liquid after the first release step after the carbon dioxide is released from the absorbing liquid in the first release step.

The first recovery step is not particularly limited as long as the sulfur compound can be adsorbed and recovered from the absorbent after the first release step. The first recovery step may include, for example, a step of passing the absorbent solution after the first release step through a recovery unit containing an adsorbent capable of adsorbing the sulfur compounds. In this step, since the absorbent after the first release step passes through the recovery unit while contacting the absorbent stored in the recovery unit, the sulfur compounds contained in the absorbent after the first release step are adsorbed by the absorbent. Recovering the sulfur compound from the absorbent after the first release step by recovering the adsorbent having adsorbed the sulfur compound. The recycler used in the first recycling step is also referred to as a first recycler.

The recovery unit is not particularly limited as long as it can adsorb and recover the sulfur compound from the absorbing liquid. The recovery unit includes, for example, a container through which the absorption liquid can flow and an adsorbent accommodated in the container. The recovery device may be a horizontal type in which the recovery device is mounted so that the longitudinal direction thereof is horizontal, or a vertical type in which the recovery device is mounted so that the longitudinal direction thereof is vertical, and the mounting direction is not particularly limited.

The adsorbent is not particularly limited as long as it is an adsorbent capable of adsorbing the sulfur compound from the absorbing liquid by contacting with the absorbing liquid. Examples of the adsorbent include a metal adsorbent, a resin adsorbent, an inorganic adsorbent, and a physical adsorbent. As the adsorbent, in addition to these, any adsorbent used for desulfurization, for example, a desulfurization adsorbent can be used. Examples of the metal adsorbent include Ca-based adsorbents, Mg-based adsorbents, Zn-based adsorbents, Fe-based adsorbents, and Ba-based adsorbents. The form of the metal adsorbent may be, for example, a metal monomer, or may be a carbonate, a hydroxide, an oxide, or the like. Examples of the resin adsorbent include ion exchange resins. Examples of the inorganic adsorbent include zeolite and silica gel. Examples of the physical adsorbent include activated carbon. The adsorbent may be used alone, or two or more kinds thereof may be used in combination.

The gas treatment method may further include the first recovery step, and the sulfur compound may be adsorbed and recovered from the absorbing liquid after the first release step, that is, the absorbing liquid after releasing carbon dioxide, in the first recovery step. This gas treatment method can recover high-concentration carbon dioxide and remove sulfur compounds from the absorbing solution after carbon dioxide recovery. That is, this gas treatment method can not only recover carbon dioxide at a high concentration but also suppress the accumulation of sulfur compounds contained in the absorbing liquid.

In the second release step, the entire sulfur compound may not be released from the absorbent solution after the first release step. In this case, in the gas treatment method, the sulfur compound is removed from the absorbent having undergone the second desorption step, and thus, for example, the accumulation of the sulfur compound contained in the absorbent in the apparatus for performing the gas treatment method can be further suppressed by the following configuration. Specifically, the gas treatment method further includes: a second recovery step of adsorbing and recovering the sulfur compounds, which have not been released in the second release step, from the absorbent liquid after the second release step after the sulfur compounds are released from the absorbent liquid in the second release step.

The second recovery step is not particularly limited as long as the sulfur compound that has not been released in the second release step can be adsorbed from the absorbent solution after the second release step and recovered. The second recovery step is the same as the first recovery step except that the absorbent solution after the second release step is used instead of the absorbent solution after the first release step. The reclaimer used in the second recovery step is also referred to as a second reclaimer. The second recovery device is not particularly limited as long as it can recover the sulfur compound from the absorbent solution after the second desorption step, and examples thereof include the same recovery device as the first recovery device.

By further including the second recovery step, the gas treatment method can adsorb and recover the sulfur compounds that have not been released in the second release step from the absorbing liquid after the second release step, i.e., the absorbing liquid after the release of the sulfur compounds, in the second recovery step. This gas treatment method can recover high-concentration carbon dioxide and remove sulfur compounds from the absorbing solution after carbon dioxide recovery. That is, this gas treatment method can not only recover carbon dioxide at a high concentration but also suppress the accumulation of sulfur compounds contained in the absorbing liquid.

The reason why the gas treatment method includes the second recovery step is that: as described above, the sulfur compound can be further removed from the absorbing liquid after the recovery of carbon dioxide. More specifically, there is a tendency that the cost required for removal in the second release step is lower than that for removal of sulfur compounds from the absorbing liquid in the second recovery step. Therefore, the removal of the sulfur compounds from the absorbing liquid in the second releasing step and then the removal of the sulfur compounds remaining in the absorbing liquid in the second recovering step can not only further remove the sulfur compounds from the absorbing liquid but also have an advantage in terms of cost. Further, if the sulfur compounds contained in the absorbent are removed in advance in the first recovery step before the sulfur compounds are removed from the absorbent in the second release step, the amount of the sulfur compounds contained in the absorbent supplied to the second release step is reduced, and therefore the sulfur compounds can be further removed from the absorbent.

The gas treatment method may not include the first recovery step and the second recovery step, and may include one or both of the first recovery step and the second recovery step. If both the first recovery step and the second recovery step are included, sulfur compounds can be further removed from the absorbent. In addition, in the first recovery step and the second recovery step, depending on the adsorbent used, a deteriorated product of an absorbing liquid component such as amine contained in the absorbing liquid, metal ions generated by corrosion, or the like may be removed in some cases. Specifically, if an adsorbent capable of adsorbing not only the sulfur compound but also a deteriorated substance of an absorbing liquid component from the absorbing liquid is used as the adsorbent, not only the sulfur compound but also the deteriorated substance of the absorbing liquid component can be removed from the absorbing liquid.

The gas treatment method may further comprise a circulating step of circulating the absorbing liquid. Examples of the circulation step include the following steps: it includes: a discarding step of discarding at least a part of the first phase portion after the first releasing step; and a reuse step of using the absorption liquid other than the discarded first phase portion as the absorption liquid that is brought into contact with the gas to be treated in the absorption step. By discarding at least a part of the first phase portion having a relatively high content of the sulfur compound in the discarding step, the sulfur compound can be discarded with high efficiency.

As described above, the sulfur compound promotes an irreversible deterioration reaction of components contained in the absorbing liquid, for example, amines and the like. That is, the sulfur compound degrades components contained in the absorbing liquid, and a degradation product of the absorbing liquid components, for example, a degradation product of amine, is generated. Therefore, if the absorbing liquid after releasing carbon dioxide is used for recovering carbon dioxide for a long period of time by reusing the absorbing liquid in the absorbing step, the amount of the degradation product of the absorbing liquid component generated in the absorbing liquid increases. Further, if the absorbent is used for the recovery of carbon dioxide for a long period of time, not only the amount of the deteriorated substance of the absorbent component increases, but also acids such as glycolic acid, oxalic acid, and formic acid are generated. The deteriorated product of the absorbing liquid component and the acid do not absorb carbon dioxide, that is, do not contribute to recovery of carbon dioxide, and therefore, the amount thereof is preferably small. Therefore, at least a part of the absorption liquid that has been used is discarded and replaced with new absorption liquid.

As described above, the absorption liquid is phase-separated into the first phase portion in which the content of the carbon dioxide and the sulfur compound is relatively high and the second phase portion in which the content of the carbon dioxide and the sulfur oxide is relatively low by absorption of the carbon dioxide and the sulfur compound. In the first phase portion, not only the carbon dioxide and the sulfur compound but also the deterioration product and acid content of the absorbing liquid component are relatively high. The reason is considered to be: since the first phase portion is an aqueous phase in which the amine is dissolved, the first phase portion is an amine phase rich in amine and the second phase portion is an organic phase rich in organic solvent. Thus, the polarity of the first phase portion is relatively high. Further, since most of the deteriorated product and the acid of the absorbing liquid component have polarity in the molecule, they are considered to be preferentially present in the first phase portion having relatively high polarity. Therefore, by discarding the first phase portion having a relatively high content of the sulfur compound, the sulfur compound can be efficiently discarded, and the deteriorated product thereof can be efficiently discarded.

Examples of the reuse step include a method in which the absorbing liquid other than the first phase portion discarded in the discarding step is introduced into the absorbing liquid shown in fig. 1 (a). In addition, the absorption liquid other than the discarded first-phase portion is an absorption liquid including the second-phase portion and the first-phase portion that is not discarded. As a method other than this method (another method), there is a method in which at least a part of the first phase portion is discarded after the first release step, and the absorbent solution other than the discarded first phase portion is introduced into the absorbent solution shown in fig. 1 (a) after the second release step.

By thus including the recycling step, the absorbing liquid other than the waste first phase portion can be used as the absorbing liquid that is brought into contact with the gas to be treated in the absorbing step, and the carbon dioxide can be recovered using the absorbing liquid having a low content of the sulfur compound and the deteriorated substance. Further, even if the absorbing liquid after releasing carbon dioxide is used again in the absorbing step or the like, and the absorbing liquid is used for recovering carbon dioxide for a long period of time, the amounts of the sulfur compound and the degradation product remaining in the absorbing liquid can be maintained in a small state. This can reduce the frequency of replacement of the absorbent and also reduce the amount of new absorbent added. Therefore, the amount of the absorbing liquid used can be reduced. Specifically, when the absorbing liquid is used for the recovery of carbon dioxide for a long period of time, the amount of the absorbing liquid to be used can be reduced by discarding the first phase portion having a relatively high content of sulfur compounds and adding a new absorbing liquid in an amount corresponding to the discarded amount.

The apparatus for carrying out the gas treatment method is not particularly limited as long as the absorption step and the first release step can be carried out, and examples thereof include a gas treatment apparatus including an absorber for absorbing carbon dioxide and a sulfur compound in an absorbing liquid by bringing a gas to be treated containing the carbon dioxide and the sulfur compound into contact with the absorbing liquid, the gas being separated by absorbing the carbon dioxide, and a first release device for releasing the carbon dioxide from the absorbing liquid by heating the absorbing liquid in contact with the gas to be treated to a temperature not lower than a temperature at which the carbon dioxide absorbed in the absorbing liquid is released from the absorbing liquid and lower than a temperature at which the sulfur compound absorbed in the absorbing liquid is released from the absorbing liquid. Such a gas processing apparatus performs the absorption step in the absorber and the first release step in the first releaser, whereby carbon dioxide having a high concentration can be recovered from the gas to be processed containing carbon dioxide and sulfur compounds.

The gas treatment apparatus is used for recovering high-concentration carbon dioxide from a gas to be treated containing carbon dioxide and sulfur compounds by using the absorption liquid. Specifically, as shown in fig. 2, the gas treatment device 21 includes an absorber 22, a first releaser 23, a circulation path 24, and a heat exchanger 25. Fig. 2 is a schematic diagram showing an example of the gas processing apparatus according to the present embodiment.

The circulation passage 24 includes: a first flow path 26 for drawing out the absorption liquid from the absorber 22 and introducing the absorption liquid into the first releaser 23; and a second flow path 27 for withdrawing the absorption liquid from the first releaser 23 and returning the absorption liquid to the absorber 22. The heat exchanger 25 may be omitted.

To the absorber 22, there are connected: a gas supply path 32 for supplying a gas to be processed; a gas discharge passage 33 through which the gas treated in the absorber 22 is discharged; a first flow path 26 for conveying the absorbent to the first releaser 23; and a second flow path 27 for returning the absorbing liquid from the first releaser 23 to the absorber 22. The gas supply channel 32 may supply a gas to be treated into the absorber 22. The gas discharge passage 33 can discharge gas that is not absorbed even if the gas to be treated is brought into contact with the absorbing liquid from the absorber 22. The first flow path 26 can draw out the absorption liquid accumulated in the absorber 22. The second channel 27 allows the absorption liquid returned from the first releaser 23 to flow downward from above.

The absorber 22 absorbs acidic compounds such as carbon dioxide and sulfur compounds in the gas to be treated into the absorbing liquid by bringing the gas to be treated into contact with the absorbing liquid, and removes the gas from which the acidic compounds have been removed. The absorber 22 may be any absorber that continuously brings the gas to be treated into contact with the absorbing liquid. As the absorber 22, for example: an absorber for spraying the absorbing liquid in the form of mist into a flow path of the gas to be treated; an absorber for allowing the absorption liquid to flow down along the filler disposed in the flow path of the gas to be treated; and an absorber for introducing the gas to be treated and the absorbing liquid into the plurality of minute flow paths, respectively, and for merging the minute flow paths of the gas to be treated and the minute flow paths of the absorbing liquid, respectively. In addition, the reaction in which carbon dioxide and sulfur compounds are absorbed into the absorbing liquid is an exothermic reaction.

The first flow path 26 and the second flow path 27 are connected to the first releaser 23. The first flow path 26 may introduce the absorption liquid led out from the absorber 22 into the first releaser 23. The second channel 27 can lead out the absorbent stored in the first releaser 23.

The first releaser 23 stores the absorption liquid and heats the stored absorption liquid to CO₂A releasable temperature above and below the sulfur compound releasable temperature, thereby releasing carbon dioxide. The release of carbon dioxide from the absorption liquid, i.e. the desorption of carbon dioxide from the components contained in the absorption liquid, is an endothermic reaction. In the first releaser 23, if the absorbent is heated as described above, not only carbon dioxide is released but also water contained in the absorbent evaporates. That is, in the first releaser 23, carbon dioxide and water vapor are released from the absorbent.

A supply passage 35 and a heating flow passage 36 are connected to the first discharger 23.

The supply passage 35 supplies the carbon dioxide obtained in the first releaser 23 to the supply target. The supply passage 35 is provided with a cooler 37 and a carbon dioxide separator 38. The cooler 37 condenses the water vapor by cooling the mixed gas of the carbon dioxide and the water vapor released from the absorbing liquid. The carbon dioxide separator 38 separates water and carbon dioxide condensed in the cooler 37. The separated water vapour is returned to the first releaser 23. As the cooler 37, a heat exchanger using inexpensive cooling water such as river water can be used. The cooler 37 and the carbon dioxide separator 38 may be omitted.

One end of the heating flow path 36 is connected to the second flow path 27, but may be connected to the first releaser 23. The other end of the heating flow path 36 is connected to the first releaser 23. The heating flow path 36 is provided with a heater 42 that heats the absorbent stored in the first discharger 23. The heater 42 may be configured to heat the absorbent inside the first discharger 23, but may heat the absorbent drawn out from the first discharger 23 to the outside as shown in the figure. In this case, the heater 42 may be disposed in the heating flow path 36 for returning the heated absorption liquid to the first discharger 23. As the heater 42, for example, a heater that directly or indirectly heats the absorbent using any heat source such as electricity, steam, or a burner may be used.

The heat exchanger 25 is connected to the first flow path 26 and the second flow path 27, and performs heat exchange between the absorption liquid flowing through the first flow path 26 and the absorption liquid flowing through the second flow path 27. The heat exchanger 25 is constituted by, for example, a plate heat exchanger, but may be constituted by a microchannel heat exchanger capable of exchanging heat between fluids having small temperature differences. Thereby, energy efficiency can be improved.

A pump 43 is provided in the second flow path 27. The second flow path 27 is provided with an absorbent discharge passage 44, a cooler 45, and an absorbent supply passage 46. The absorption liquid discharge passage 44 discharges the absorption liquid from the gas treatment device 21 when the absorption liquid is replaced or the like. The cooler 45 cools the absorption liquid returned to the absorber 22. The absorbent supply path 46 supplies the absorbent to the second channel 27 when the absorbent is replaced or the like. In addition, the cooler 45 may be omitted.

The gas processing apparatus 21 performs the absorption step in the absorber 22 and performs the first release step in the first releaser 23, so that carbon dioxide with a high concentration can be recovered from the gas to be processed containing carbon dioxide and sulfur compounds. In addition, the gas treatment device 21 can use the absorption liquid for the recovery of the carbon dioxide for a long period of time by circulating the absorption liquid through the circulation passage 24.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 3, there may be mentioned a gas treatment apparatus 31 similar to the gas treatment apparatus 21 except that at least a part of the first phase portion is separated from the absorption liquid discharged from the first discharger 23. That is, the gas treatment apparatus 31 may be similar to the gas treatment apparatus 21 except that the gas treatment apparatus further includes a circulation mechanism for discarding at least a part of the first phase portion after the carbon dioxide gas is released from the absorbing liquid by the first releaser 23 and using the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is brought into contact with the gas to be treated in the absorber 22.

Specifically, the gas processing apparatus 31 is provided with a phase separator 52 in the second flow path. The phase separator 52 separates at least a part of the first phase portion of the absorption liquid led out from the first releaser 23. A lead-out passage 53 is provided in the phase separator 52. The lead-out passage 53 leads out the first phase portion separated at the phase separator 52. The first phase portion thus extracted may be discarded, or may be supplied to another device, for example, a second releaser described later, as described later. Further, the absorption liquid separated by the phase separator 52 and led out to the lead-out passage 53 except the first phase portion is returned to the absorber 22 through the second flow path 27. The phase separator 52 is not particularly limited as long as at least a part of the first phase portion can be extracted from the absorption liquid that is phase-separated into the first phase portion and the second phase portion by absorption of the sulfur compound, and since the first phase portion becomes a lower layer, a container or the like connected to the lead-out passage 53 so as to lead out only the lower layer can be exemplified. Fig. 3 is a schematic diagram showing another example of the gas processing apparatus 31 according to the present embodiment.

The gas processing apparatus 31 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, and the circulation step in the phase separator 52 and the circulation path 24. Therefore, the gas processing apparatus 31 can not only recover carbon dioxide from the gas to be processed at a high concentration, but also efficiently discard the sulfur compound, the deteriorated product, and the acid. Further, even when the absorbing solution is used for the recovery of carbon dioxide for a long period of time, the contents of the deteriorated product and the acid can be kept low. This can reduce the frequency of replacement of the absorbent and reduce the amount of absorbent to be resupplied.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 4, there can be mentioned a gas treatment apparatus 41 similar to the gas treatment apparatus 31 except that a second discharger 62 for heating the absorbing liquid, which has been discharged with carbon dioxide in the first discharger 23, to a temperature equal to or higher than the sulfur compound release temperature is provided. Fig. 4 is a schematic diagram showing another example of the gas processing apparatus 41 according to the present embodiment.

The gas processing device 41 is provided with the second releaser 62 in the lead-out passage 53. The lead-out passage 53 and a third flow path 68 are connected to the second releaser 62. The lead-out passage 53 may lead the absorption liquid led out from the phase separator 52 into the second discharger 62. A pump 86 is provided in the lead-out passage 53. The third flow path 68 can lead out the absorbent stored in the second releaser 62. Further, a pump may be provided in the third flow path 68. The third channel 68 supplies the absorbent led out from the second releaser 62 to the second channel 27. A cooler may be provided in the third flow path 68.

The second releaser 62 stores the absorbing liquid and releases the sulfur compounds by heating the stored absorbing liquid to a temperature above the release temperature of the sulfur compounds. The liberation of the sulphur compounds from the absorption liquid, i.e. the dissociation of the sulphur compounds from the components contained in the absorption liquid, is an endothermic reaction. In addition, in the second releaser 62, if the absorbent is heated as described above, not only the sulfur compounds are released but also the water contained in the absorbent evaporates. That is, in the second releaser 62, sulfur compounds and water vapor are released from the absorbent liquid.

A release passage 63 and a heating flow path 66 are connected to the second release 62.

The release passage 63 releases the sulfur compounds generated from the absorbing liquid in the second releaser 62 and conveys them to a recovery device or the like. A cooler 64 and a sulfur compound separator 65 are provided in the release passage 63. The cooler 64 condenses the water vapor by cooling the mixed gas of the sulfur compounds and the water vapor released from the absorbing liquid. The sulfur compound separator 65 separates water and sulfur compounds condensed in the cooler 64. The separated water vapor is returned to the second releaser 62. As the cooler 64, a heat exchanger using inexpensive cooling water such as river water can be used. The cooler 64 and the sulfur compound separator 65 may be omitted.

One end of the heating flow path 66 is connected to the third flow path 68, but may be connected to the second releaser 62. The other end of the heating flow path 66 is connected to the second releaser 62. A heater 67 for heating the absorbent stored in the second discharger 62 is provided in the heating flow path 66. The heater 67 may be configured to heat the absorbent liquid inside the second discharger 62, but as shown in the figure, the absorbent liquid drawn out from the second discharger 62 to the outside may be heated. In this case, the heater 67 may be disposed in the heating flow path 66 for returning the heated absorbing liquid to the second discharger 62. As the heater 67, for example, a heater that directly or indirectly heats the absorbent using any heat source such as electricity, steam, or a burner may be used.

The gas processing apparatus 41 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, and the second release step in the second releaser 62. Thereby, the gas treatment device 41 can separately recover carbon dioxide and sulfur compounds from the gas to be treated.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 5, there may be mentioned a gas treatment apparatus 51 similar to the gas treatment apparatus 41 except that not only the second discharger 62 but also the absorbing liquid discharge path 70 are provided in the lead-out path 53. Fig. 5 is a schematic diagram showing another example of the gas processing apparatus 51 according to the present embodiment.

The gas processing apparatus 51 includes an absorbing liquid discharge passage 70 for discarding at least a part of the first phase portion of the absorbing liquid discharged from the phase separator 52 in the discharge passage 53. The absorbent that is not discarded at the absorbent discharge passage 70 is delivered to the second releaser 62.

The gas processing apparatus 51 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, the second release step in the second releaser 62, and the circulation step in the phase separator 52, the circulation path 24, and the third flow path 68. Thereby, the gas treatment device 51 can separately recover carbon dioxide and sulfur compounds from the gas to be treated. Further, even if the absorbing liquid is used for recovering the carbon dioxide and the sulfur compound for a long period of time, the frequency of replacement of the absorbing liquid can be reduced, and the amount of the absorbing liquid to be newly supplied can be reduced.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 6, there can be mentioned a gas treatment apparatus 61 similar to the gas treatment apparatus 31 except that a first recovery unit 83 for adsorbing and recovering the sulfur compound from the absorbing liquid after releasing carbon dioxide in the first releaser 23 is provided. Fig. 6 is a schematic diagram showing another example of the gas processing apparatus 61 according to the present embodiment.

The gas processing device 61 is provided with the first recovery device 83 specifically in the lead-out passage 53. The lead-out passage 53 and the fourth flow path 82 are connected to the first trap 83. A pump 86 is disposed in the discharge passage 53. The lead-out passage 53 may lead the absorption liquid led out from the phase separator 52 into the first recovery unit 83. The fourth channel 82 supplies the absorbent having passed through the first receiver 83 to the second channel 27.

The first reclaimer 83 is the first reclaimer used in the first recovery step described above, and is a reclaimer that adsorbs and recovers the sulfur compound from the absorption liquid discharged from the first releaser 23. In the gas processing apparatus 61, the first recovery unit 83 is provided in a vertical position.

The gas processing apparatus 61 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, and the first recovery step in the first reclaimer 83. Thereby, the gas processing apparatus 61 can separately recover carbon dioxide and sulfur compounds from the gas to be processed.

The first retractor 83 may be a vertically disposed first retractor as described above, or may be a horizontally disposed first retractor as described below.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 7, there can be mentioned a gas treatment apparatus 71 similar to the gas treatment apparatus 61 except that a first regenerator 83 is provided as the first regenerator in a horizontal manner instead of the first regenerator 83 in a vertical manner. Fig. 7 is a schematic diagram showing another example of the gas processing apparatus 71 according to the present embodiment.

The gas processing apparatus 71 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, and the first recovery step in the first reclaimer 83. Thereby, the gas treatment device 71 can separately recover carbon dioxide and sulfur compounds from the gas to be treated.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 8, there is a gas treatment apparatus 81 similar to the gas treatment apparatus 41 except that a second recovery unit 84 for adsorbing and recovering the sulfur compounds that are not released in the second releaser 62 from the absorbing liquid after the release of the sulfur compounds in the second releaser 62 is provided. Fig. 8 is a schematic diagram showing another example of the gas processing apparatus 81 according to the present embodiment.

Specifically, the gas treatment device 81 is provided with the second recovery unit 84 in the third flow path 68. The third flow path 68 and the fifth flow path 85 are connected to the second recovery unit 84. The third flow path 68 allows the absorbent discharged from the second discharger 62 to be introduced into the second recovery unit 84. The fifth channel 85 can supply the absorbent that has passed through the second recovery unit 84 to the second channel 27.

The second recovery unit 84 is the second recovery unit used in the second recovery step described above, and is a recovery unit that adsorbs and recovers the sulfur compounds from the absorption liquid discharged from the second releaser 62. Specifically, the second recovery unit 84 may be the same as the first recovery unit used in the first recovery step. In the gas treatment device 81, the second recovery unit 84 is disposed in a horizontal position, but may be disposed in a vertical position.

The gas processing apparatus 81 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, the second release step in the second releaser 62, the circulation step in the phase separator 52, the circulation path 24, and the third flow path 68, and the second recovery step in the second recovery unit 84. Thereby, the gas processing apparatus 81 can separately recover carbon dioxide and sulfur compounds from the gas to be processed. Further, even if the absorbing liquid is used for recovering the carbon dioxide and the sulfur compound for a long period of time, the frequency of replacement of the absorbing liquid can be reduced, and the amount of the absorbing liquid to be newly supplied can be reduced.

As described above, the gas treatment device may include either the first recovery unit or the second recovery unit, but as described later, may include both the first recovery unit and the second recovery unit.

As another apparatus for carrying out the gas treatment method, for example, as shown in fig. 9, there is a gas treatment apparatus 91 similar to the gas treatment apparatus 81 except that a first recovery unit 83 for adsorbing and recovering the sulfur compound from the absorbing liquid after releasing carbon dioxide in the first releaser 23 is provided. The third flow path 68 may be provided with a pump as described above, and the gas processing apparatus shown in fig. 9 may be provided with a pump 69 in the third flow path 68. Fig. 9 is a schematic diagram showing another example of the gas processing apparatus 91 according to the present embodiment.

The gas processing apparatus 91 may perform the absorption step in the absorber 22, the first release step in the first releaser 23, the second release step in the second releaser 62, the circulation step in the phase separator 52, the circulation path 24, and the third flow path 68, the first recovery step in the first recovery unit 83, and the second recovery step in the second recovery unit 84. Thereby, the gas processing apparatus 91 can separately recover carbon dioxide and sulfur compounds from the gas to be processed. Further, even if the absorbing liquid is used for recovering the carbon dioxide and the sulfur compound for a long period of time, the frequency of replacement of the absorbing liquid can be reduced, and the amount of the absorbing liquid to be newly supplied can be reduced.

The present specification discloses various technical aspects as described above, and the main technical aspects thereof are summarized as follows.

One aspect of the present invention relates to a gas treatment method comprising the steps of: an absorption step of bringing a gas to be treated containing carbon dioxide and a sulfur compound into contact with an absorption liquid that is phase-separated by absorbing carbon dioxide, thereby causing the absorption liquid to absorb the carbon dioxide and the sulfur compound; and a first release step of heating the absorbent that has been brought into contact with the gas to be treated to a temperature that is equal to or higher than a temperature at which carbon dioxide absorbed in the absorbent is released from the absorbent and lower than a temperature at which sulfur compounds absorbed in the absorbent are released from the absorbent, thereby releasing the carbon dioxide from the absorbent.

According to this configuration, in the absorption step, the gas to be treated is brought into contact with the absorbing liquid, whereby carbon dioxide contained in the gas to be treated is absorbed by the absorbing liquid and sulfur compounds contained in the gas to be treated are also absorbed.

The carbon dioxide is released from the absorbing liquid by heating the absorbing liquid that has absorbed the carbon dioxide and the sulfur compound in the first releasing step. In this first release step, the absorbing liquid is heated to a temperature equal to or higher than a temperature at which the carbon dioxide absorbed in the absorbing liquid is released from the absorbing liquid, and therefore, the carbon dioxide can be released from the absorbing liquid. The carbon dioxide released from the absorbing liquid is separated from the absorbing liquid and can be recovered.

In addition, there is a gas that is difficult to be absorbed by the absorbing liquid that undergoes phase separation by absorption of carbon dioxide, such as nitrogen, among the gases to be treated. The gas that is not absorbed by the absorbent liquid is not released even if the absorbent liquid is heated in the first release step.

Further, since the heating in the first release step is heating at a temperature lower than the temperature at which the sulfur compounds absorbed by the absorbing liquid are released from the absorbing liquid, the release of the sulfur compounds is sufficiently suppressed even if the gas to be treated contains the sulfur compounds.

Thereby, in the first release step, not only the release of the gas that is difficult to be absorbed by the absorbent liquid is sufficiently suppressed, but also the release of the sulfur compound absorbed by the absorbent liquid is sufficiently suppressed.

Through the above steps, the gas treatment method preferentially releases carbon dioxide from a gas to be treated containing not only carbon dioxide but also sulfur compounds. That is, in the gas treatment method, it is possible to sufficiently suppress mixing of the gas that is difficult to be absorbed by the absorbing liquid and the sulfur compound into the gas released from the absorbing liquid. Therefore, the gas treatment method can recover carbon dioxide at a high concentration even if the gas to be treated contains sulfur compounds and even if the sulfur compounds are not removed from the gas to be treated in advance by using a desulfurization device or the like.

In addition, CO can be recovered by chemical absorption₂Gas processing apparatus (CO)₂Recovery apparatus), as described above, it is also required that the sulfur compounds accumulated in the apparatus be small even if the gas to be treated containing the sulfur compounds is treated. In the gas treatment method, the sulfur compound is removed from the absorbing liquid after the recovery of carbon dioxide, and thus, for example, the accumulation of the sulfur compound contained in the absorbing liquid in the apparatus for carrying out the gas treatment method can be suppressed by the following configuration.

Further, the gas treatment method may further include: a first recovery step of adsorbing and recovering the sulfur compound from the absorbent after the first release step after the carbon dioxide is released from the absorbent in the first release step.

According to this configuration, in the first recovery step, the sulfur compound can be adsorbed and recovered from the absorbing liquid after the first release step, that is, the absorbing liquid after release of carbon dioxide. Therefore, according to this gas treatment method, not only carbon dioxide having a high concentration can be recovered, but also sulfur compounds can be removed from the absorbing liquid after carbon dioxide recovery. This can also suppress accumulation of sulfur compounds contained in the absorbing liquid.

Further, the gas treatment method may further include: a second releasing step of heating the absorbent after the first releasing step to a temperature equal to or higher than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent after the carbon dioxide is released from the absorbent in the first releasing step, thereby releasing the sulfur compound from the absorbent.

According to this configuration, the sulfur compound can be released from the absorbent in the second release step by heating the absorbent after the first release step, that is, the absorbent after the release of carbon dioxide, to a temperature equal to or higher than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent. Therefore, according to this gas treatment method, not only carbon dioxide having a high concentration can be recovered, but also sulfur compounds can be removed from the absorbing liquid after carbon dioxide recovery. This can also suppress accumulation of sulfur compounds contained in the absorbing liquid.

In the second release step, the entire sulfur compound may not be released from the absorbent solution after the first release step. In this case, in the gas treatment method, the sulfur compound is removed from the absorbent having undergone the second desorption step, and thus, for example, the accumulation of the sulfur compound contained in the absorbent in the apparatus for carrying out the gas treatment method is further suppressed by the following configuration.

Further, the gas treatment method may further include: a second recovery step of adsorbing and recovering the sulfur compounds, which are not released in the second release step, from the absorbent liquid after the second release step, after the sulfur compounds are released from the absorbent liquid in the second release step.

According to this configuration, in the second recovery step, the sulfur compound that has not been released in the second release step can be adsorbed and recovered from the absorbing liquid after the second release step, that is, the absorbing liquid after the release of the sulfur compound. Therefore, according to this gas treatment method, not only carbon dioxide having a high concentration can be recovered, but also sulfur compounds can be further removed from the absorbing solution after carbon dioxide recovery. This can further suppress the accumulation of sulfur compounds contained in the absorbing liquid.

The reason why the second recovery step is provided in the gas treatment method is as described above, and sulfur compounds can be further removed from the absorbing solution after recovery of carbon dioxide. More specifically, there is a tendency that the cost required for removal in the second release step is lower than that for removal of sulfur compounds from the absorbing liquid in the second recovery step. Therefore, the removal of the sulfur compounds from the absorbing liquid in the second releasing step and then the removal of the sulfur compounds remaining in the absorbing liquid in the second recovering step can not only further remove the sulfur compounds from the absorbing liquid but also have an advantage in terms of cost. Further, the sulfur compounds contained in the absorbent may be removed in advance in the first recovery step before the sulfur compounds are removed from the absorbent in the second release step, and the sulfur compounds may be further removed from the absorbent.

In addition, in the first recovery step and the second recovery step, a deteriorated substance of an absorbing liquid component such as amine contained in the absorbing liquid, metal ions generated by corrosion, or the like may be removed.

In the gas treatment method, the gas treatment method may further include: the absorbing liquid is an absorbing liquid that also undergoes phase separation by absorbing the sulfur compound, and in the absorbing step, the absorbing liquid phase separates into a first phase portion and a second phase portion by absorbing the carbon dioxide and the sulfur compound, and the content ratio of the carbon dioxide and the sulfur compound in the first phase portion is higher than the content ratio of the carbon dioxide and the sulfur compound in the second phase portion, and the second releasing step is a step of heating the first phase portion after the carbon dioxide is released from the absorbing liquid in the first releasing step.

According to this configuration, in the absorption step, the absorption liquid phase is separated into: a first phase portion in which the content of the carbon dioxide and the sulfur compound is relatively high, and a second phase portion in which the content of the carbon dioxide and the sulfur compound is relatively low. In addition, even in the first phase portion after the carbon dioxide is released from the absorbent in the first release step, the content of the sulfur compound in the first phase portion is higher than the content of the sulfur compound in the second phase portion. In the second release step, the sulfur compound is released from the absorbing liquid by heating the first phase portion having a relatively high content of the sulfur compound, and therefore, the sulfur compound can be efficiently released from the absorbing liquid.

Further, the gas treatment method may further include: a step of discarding at least a part of the first phase portion after the first releasing step, and using the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is brought into contact with the gas to be treated in the absorbing step.

According to this configuration, by discarding at least a part of the first phase portion having a relatively high content of the sulfur compound, the sulfur compound can be efficiently discarded.

Further, the sulfur compound promotes irreversible deterioration reaction of components contained in the absorbing liquid, such as amine, as described above. That is, the sulfur compound degrades components contained in the absorbent, and a degraded product of the absorbent component is generated. Therefore, if the absorbing liquid after releasing carbon dioxide is reused in the absorption step and the like, and the absorbing liquid is used for recovering carbon dioxide for a long period of time, the amount of the degradation product of the absorbing liquid component generated in the absorbing liquid increases. Therefore, at least a part of the absorption liquid that has been used is discarded and replaced with new absorption liquid. By discarding the first phase portion having a relatively high content of the sulfur compound, the sulfur compound can be efficiently discarded, and the deteriorated product can be efficiently discarded.

Further, by using the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is brought into contact with the gas to be treated in the absorbing step, it is possible to recover carbon dioxide using the absorbing liquid having a low content of the sulfur compound and the deteriorated substance.

Further, even if the absorbing liquid after releasing carbon dioxide is reused in the absorbing step and the like, and the absorbing liquid is used for recovering carbon dioxide for a long period of time, the amounts of the sulfur compound and the degradation product remaining in the absorbing liquid can be maintained in a small state. This makes it possible to reduce the frequency of replacement of the absorbent, and to reduce the amount of absorbent to be added and the amount of absorbent to be used. Specifically, when the absorbing liquid is used for the recovery of carbon dioxide for a long period of time, the first phase portion having a relatively high content of sulfur compounds is discarded, and a new absorbing liquid corresponding to the discarded amount is added, whereby the amount of the absorbing liquid used can be reduced.

Another aspect of the invention relates to a gas treatment apparatus comprising: an absorber that causes an absorption liquid, which is phase-separated by absorbing carbon dioxide, to absorb carbon dioxide and a sulfur compound by bringing a gas to be treated containing the carbon dioxide and the sulfur compound into contact with the absorption liquid; and a first releaser that releases the carbon dioxide from the absorbent by heating the absorbent that has been contacted with the gas to be treated to a temperature that is equal to or higher than a temperature at which the carbon dioxide absorbed in the absorbent is released from the absorbent and lower than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent.

According to this configuration, even if not only carbon dioxide but also sulfur compounds are absorbed by the absorbing liquid in the absorber, carbon dioxide can be preferentially released from the absorbing liquid in the first absorber. Further, the gas that is not absorbed by the absorbent is not released even if the absorbent is heated in the first releaser. Therefore, in the first releaser, not only the release of the gas that is difficult to be absorbed by the absorbing liquid is sufficiently suppressed, but also the release of the sulfur compounds absorbed by the absorbing liquid is sufficiently suppressed. That is, in the gas treatment apparatus, carbon dioxide is preferentially released from the gas to be treated which does not contain only carbon dioxide but also sulfur compounds. Therefore, carbon dioxide of high concentration can be recovered from the gas to be treated.

Thus, the gas processing apparatus can recover carbon dioxide at a high concentration even if the gas to be processed contains sulfur compounds and even if the sulfur compounds are not removed from the gas to be processed in advance by a desulfurization apparatus or the like. In the gas treatment apparatus, the sulfur compound is removed from the absorbing liquid after the recovery of carbon dioxide, and thus, for example, the accumulation of the sulfur compound contained in the absorbing liquid in the gas treatment apparatus can be suppressed by the following configuration.

Further, the gas processing apparatus may further include: a first regenerator that adsorbs and recovers the sulfur compound from the absorbing liquid after the carbon dioxide is released in the first releaser.

According to this configuration, the sulfur compound can be adsorbed and recovered from the absorbent after the carbon dioxide is released in the first releaser in the first reclaimer. Therefore, according to this gas processing apparatus, not only carbon dioxide having a high concentration can be recovered, but also sulfur compounds can be removed from the absorbing liquid after carbon dioxide recovery. This can also suppress accumulation of sulfur compounds contained in the absorbing liquid.

Further, in the gas treatment apparatus, when the first recovery device is included, it is preferable that: the first regenerator includes an adsorbent capable of adsorbing the sulfur compound, and the adsorbent includes at least one selected from the group consisting of a metal adsorbent, a resin adsorbent, an inorganic adsorbent, and a physical adsorbent.

With this configuration, the sulfur compound can be adsorbed and recovered more efficiently from the absorbent after the carbon dioxide is released in the first releaser. Therefore, the accumulation of the sulfur compounds contained in the absorbing liquid can be further suppressed.

In the gas treatment apparatus, the first recovery unit may be a horizontal type in which the longitudinal direction is horizontal, or a vertical type in which the longitudinal direction is vertical.

Further, the gas processing apparatus may further include: a second releaser for releasing the sulfur compound from the absorbent by heating the absorbent having released the carbon dioxide from the first releaser to a temperature equal to or higher than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent.

According to this configuration, the second releaser heats the absorbent having released the carbon dioxide gas in the first releaser to a temperature equal to or higher than a temperature at which the sulfur compound absorbed in the absorbent is released from the absorbent, thereby enabling the release of the sulfur compound from the absorbent. Therefore, according to this gas processing apparatus, not only carbon dioxide having a high concentration can be recovered, but also sulfur compounds can be removed from the absorbing liquid after carbon dioxide recovery. This can also suppress accumulation of sulfur compounds contained in the absorbing liquid.

In the second releaser, the entire sulfur compound may not be released from the absorbent after the carbon dioxide is released in the first releaser. In this case, in the gas treatment apparatus, the sulfur compound is removed from the absorbent after the sulfur compound is released from the second releaser, and thus, for example, the accumulation of the sulfur compound contained in the absorbent in the gas treatment apparatus can be further suppressed by the following configuration.

Further, the gas processing apparatus may further include: a second recoverer that adsorbs and recovers the sulfur compound that is not released in the second releaser from the absorbent after the sulfur compound is released in the second releaser.

According to this configuration, the sulfur compounds that have not been released in the second releaser can be adsorbed and recovered in the second recoverer from the absorbent after the sulfur compounds have been released in the second releaser. Therefore, according to this gas processing apparatus, not only carbon dioxide having a high concentration can be recovered, but also sulfur compounds can be further removed from the absorbing liquid after carbon dioxide recovery. This can further suppress the accumulation of sulfur compounds contained in the absorbing liquid.

The reason why the gas processing apparatus is provided with the second recovery unit is as described above, and sulfur compounds can be further removed from the absorbing liquid after the recovery of carbon dioxide. More specifically, the cost required for the removal in the second releaser tends to be lower than the cost required for the removal of the sulfur compounds from the absorbing liquid in the second reclaimer. Therefore, removing sulfur compounds from the absorbing liquid in the second releaser and then removing the sulfur compounds remaining in the absorbing liquid in the second recoverer makes it possible to remove not only sulfur compounds from the absorbing liquid but also cost-effectively. Further, the sulfur compounds contained in the absorbing liquid are removed in advance in the first reclaimer before the sulfur compounds are removed from the absorbing liquid in the second releaser, which can further remove the sulfur compounds from the absorbing liquid.

In addition, in the treatment in the first recovery unit and the treatment in the second recovery unit, a deterioration product of an absorbing liquid component such as amine contained in the absorbing liquid, metal ions generated by corrosion, or the like may be removed.

Further, the gas processing apparatus may be configured such that: the absorbing liquid is an absorbing liquid that also undergoes phase separation by absorbing the sulfur compound, the absorbing liquid phase separates into a first phase portion and a second phase portion by absorbing the carbon dioxide and the sulfur compound in the absorber, the content rate of the carbon dioxide and the sulfur compound in the first phase portion is higher than the content rate of the carbon dioxide and the sulfur compound in the second phase portion, and the second releaser heats the first phase portion after the carbon dioxide is released from the absorbing liquid in the first releaser.

According to this configuration, even in the first phase portion after the carbon dioxide is released from the absorbent in the first releaser, the content of the sulfur compound in the first phase portion is higher than the content of the sulfur compound in the second phase portion. The sulfur compound is released from the absorbent by heating the first phase portion having a relatively high content of the sulfur compound in the second releaser, and therefore, the sulfur compound can be released from the absorbent with high efficiency.

Further, in the gas treatment device, when the second recovery unit is included, it is preferable that: the second recovery device includes an adsorbent capable of adsorbing the sulfur compound, and the adsorbent includes at least one selected from the group consisting of a metal adsorbent, a resin adsorbent, an inorganic adsorbent, and a physical adsorbent.

With this configuration, the sulfur compound can be adsorbed and recovered more efficiently from the absorbent after the sulfur compound is released in the second releaser. Therefore, the accumulation of the sulfur compounds contained in the absorbing liquid can be further suppressed.

In the gas treatment apparatus, the first recovery unit and the second recovery unit may be of a horizontal type in which the longitudinal direction is horizontal, or of a vertical type in which the longitudinal direction is vertical.

Further, the gas processing apparatus may further include: a mechanism that discards at least a part of the first phase portion after the carbon dioxide is released from the absorbing liquid in the first releaser, and uses the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is in contact with the gas to be treated in the absorber.

According to this configuration, by discarding at least a part of the first phase portion having a relatively high content of the sulfur compound, not only the sulfur compound but also the deteriorated product can be efficiently discarded. Further, by using the absorbing liquid other than the discarded first phase portion as the absorbing liquid that is brought into contact with the gas to be treated in the absorber, it is possible to recover carbon dioxide using the absorbing liquid having a low content of the sulfur compound and the deteriorated substance. Further, even if the absorbing liquid after releasing carbon dioxide is reused in the absorbing step and the like, and the absorbing liquid is used for recovering carbon dioxide for a long period of time, the amounts of the sulfur compound and the degradation product remaining in the absorbing liquid can be maintained in a small state. This makes it possible to reduce the frequency of replacement of the absorbent, and to reduce the amount of new absorbent to be added, thereby reducing the amount of absorbent used. Specifically, when the absorbing liquid is used for the recovery of carbon dioxide for a long period of time, the first phase portion having a relatively high content of sulfur compounds is discarded, and a new absorbing liquid corresponding to the discarded amount is added, whereby the amount of the absorbing liquid used can be reduced.

According to the present invention, a gas treatment method and a gas treatment apparatus capable of recovering carbon dioxide at a high concentration can be provided.

The application is based on Japanese patent application special application 2019-099533 applied on 5/28/2019 and Japanese patent application special application 2020-001034 applied on 1/7/2020, and the contents of the application are included in the application.

In order to describe the present invention, the present invention has been described appropriately and sufficiently by the embodiments with reference to the drawings, but it should be understood that the modifications and/or improvements of the above embodiments can be easily made by those skilled in the art. Therefore, the modified embodiments or modified embodiments that can be implemented by those skilled in the art are intended to be included in the scope of the claims as long as they do not depart from the scope of the claims set forth in the claims.

Industrial applicability

According to the present invention, a gas treatment method and a gas treatment apparatus capable of recovering carbon dioxide at a high concentration are provided.