JP6173817B2 - Acid gas absorbent, acid gas removal method, and acid gas removal apparatus - Google Patents

Description

  Embodiments described herein relate generally to an acid gas absorbent, an acid gas removal method, and an acid gas removal apparatus.

In recent years, the greenhouse effect due to an increase in carbon dioxide (CO ₂ ) concentration has been pointed out as a cause of global warming, and international measures to protect the environment on a global scale are urgently needed. The source of CO ₂ is largely due to industrial activities, and the momentum for controlling emissions is increasing.

Techniques for suppressing the increase in the concentration of acid gases, including CO _2, the development of energy-saving products, separation and recovery techniques acid gas to be discharged, a technique for utilizing and capture and storage as a resource acid gas, acid gases There is a shift to alternative energy such as natural energy and nuclear energy that does not emit energy.

  Acid gas separation techniques that have been studied to date include absorption methods, adsorption methods, membrane separation methods, and cryogenic methods. In particular, the absorption method is suitable for processing a large amount of gas, and its application to factories and power plants is being studied.

Therefore, for facilities such as thermal power plants that use fossil fuel, the exhaust gas generated when burning fossil fuel (coal, petroleum, natural gas, etc.) is brought into contact with the chemical absorbent, and CO ₂ in the combustion exhaust gas A method for removing and recovering CO ₂ and a method for storing the recovered CO ₂ are performed all over the world. Further, it has been proposed to remove an acidic gas such as hydrogen sulfide (H ₂ S) in addition to CO ₂ using a chemical absorbent.

  In general, alkanolamines typified by monoethanolamine (MEA) have been developed since the 1930s as chemical absorbents used in the absorption method and are still in use. This method is economical and the removal apparatus can be easily increased in size.

  Alkanolamines widely used in the past include monoethanolamine, 2-amino-2-methylpropanolamine, methylaminoethanol, ethylaminoethanol, propylaminoethanol, diethanolamine, bis (2-hydroxy-1-methylethyl) Examples include amine, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triethanolamine, and dimethylamino-1-methylethanol.

  In particular, ethanolamine, which is a primary amine, has been widely used because of its high reaction rate. However, this compound has a problem that it is corrosive, easily deteriorates, and requires high energy for regeneration. On the other hand, methyldiethanolamine has a drawback of low absorption rate although it has low corrosivity and low energy required for regeneration. Therefore, development of a new adsorbent that improves these points is required.

  In recent years, research has been actively conducted on alkanolamines having structurally steric hindrance, among amine compounds, as acid gas absorbents. The alkanolamine having steric hindrance has the advantages that the selectivity of the acid gas is very high and the energy required for regeneration is small.

  The reaction rate of an amine compound having steric hindrance depends on the degree of reaction hindrance determined by its steric structure. The reaction rate of amine compounds having steric hindrance is lower than that of secondary amines such as methylethanolamine and diethanolamine, but is higher than that of tertiary amines such as methyldiethanolamine.

  On the other hand, as an amine compound having a structure different from that of alkanolamines, a method using a cyclic amine as an absorbent is also known.

JP 2008-307519 A Japanese Patent No. 2871334 U.S. Pat. No. 4,120,052

  However, even in these techniques, the acid gas absorption capacity, the acid gas absorption rate, the acid gas absorption capacity such as the reaction heat at the time of acid gas absorption are still insufficient, and further improvement of the gas absorption capacity is required. Further, in these techniques, when absorbing the acid gas in the absorption tower, or when regenerating the absorbent in the regeneration tower, the absorbent is easily dissipated from the absorption tower or the regeneration tower. Absorbent recovery efficiency may be reduced. For this reason, there is a demand for an absorbent that has reduced dispersibility even under the environment of use in actual equipment.

  The problem to be solved by the present invention is that the absorption amount and absorption rate of acidic gas such as carbon dioxide are high, the reaction heat at the time of acid gas absorption is low, further, the dispersibility is suppressed, and the absorption capacity of acid gas is reduced. An excellent acid gas absorbent, and an acid gas removing device and an acid gas removing method using the same are provided.

・・・（１）
（上記式（１）中、Ｒ^１、Ｒ^３は炭素数２〜４のヒドロキシアルキル基を表し、それぞれ同一であっても異なっていてもよい。但し、Ｒ^１、Ｒ^３は、直鎖状又は分岐鎖状の炭素原子数２〜４個のアルキル基の水素原子のうち、窒素原子に結合する炭素原子以外の炭素原子に結合する水素原子の少なくとも一つが、ヒドロキシル基で置換された基である。Ｒ^２、Ｒ^４は水素原子又は炭素数１〜４のアルキル基を表す。但し、Ｒ^２、Ｒ^４のうちの少なくとも一つは水素原子を表す。ｘ、ｙは、それぞれ窒素原子に直接結合した２つの炭素原子間の結合に介在する炭素原子の数であり、ｘは、１〜６の整数を表し、１≦ｘ＋ｙ≦６であり、ｙは、０である。） The acidic gas absorbent of the embodiment contains at least one diamine compound having a carbocyclic structure represented by the following general formula (1).

... (1)
(In said formula (1), R < ¹ >, R < ³ > represents a C2-C4 hydroxyalkyl group, and may respectively be same or different, However, R < ¹ >, R < ³ > is linear Or, among the hydrogen atoms of a branched alkyl group having 2 to 4 carbon atoms, a group in which at least one hydrogen atom bonded to a carbon atom other than a carbon atom bonded to a nitrogen atom is substituted with a hydroxyl group R ² and R ^{4 each} represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that at least one of R ² and R ⁴ represents a hydrogen atom, and x and y each represents a nitrogen atom. the number of carbon atoms interposed coupling between directly bonded to two carbon atoms, x is, represents 1-6 integer, Ri 1 ≦ x + y ≦ 6 der, y is Ru 0 der.)

It is the schematic of the acidic gas removal apparatus of embodiment.

Hereinafter, embodiments of the present invention will be described in detail.
The acidic gas absorbent according to the embodiment is characterized by containing at least one diamine compound represented by the following general formula (1).

・・・（１）
（上記式（１）中、Ｒ^１、Ｒ^３は炭素数２〜４のヒドロキシアルキル基を表し、それぞれ同一であっても異なっていてもよい。但し、Ｒ^１、Ｒ^３は、直鎖状又は分岐鎖状の炭素原子数２〜４個のアルキル基の水素原子のうち、窒素原子に結合する炭素原子以外の炭素原子に結合する水素原子の少なくとも一つが、ヒドロキシル基で置換された基である。Ｒ^２、Ｒ^４は水素原子又は炭素数１〜４のアルキル基を表す。但し、Ｒ^２、Ｒ^４のうちの少なくとも一つは水素原子を表す。ｘ、ｙは、それぞれ独立に０〜６の整数を表し、１≦ｘ＋ｙ≦６である。）

... (1)
(In said formula (1), R < ¹ >, R < ³ > represents a C2-C4 hydroxyalkyl group, and may respectively be same or different, However, R < ¹ >, R < ³ > is linear Or, among the hydrogen atoms of a branched alkyl group having 2 to 4 carbon atoms, a group in which at least one hydrogen atom bonded to a carbon atom other than a carbon atom bonded to a nitrogen atom is substituted with a hydroxyl group R ² and R ^{4 each} represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that at least one of R ² and R ⁴ represents a hydrogen atom, and x and y each independently represents 0. Represents an integer of ˜6, and 1 ≦ x + y ≦ 6.)

  Conventionally, it is known that the steric hindrance of an amino compound has a large influence on a product upon absorption of carbon dioxide, and works favorably for the production of bicarbonate ions exhibiting a low heat of reaction. For example, it has been reported that N-isopropylaminoethanol having a branched structure exhibits a low reaction heat property for an absorption reaction of carbon dioxide. Based on such knowledge, the inventors of the present application have studied to obtain a greater effect of steric hindrance. As a result, the compound represented by the above general formula (1) (for example, 1,2-cyclopentanediamine-N, N′-diethanol) However, it has been found that a lower heat of reaction can be obtained than an amino compound having a conventional branched structure.

That is, in the diamine compound of the general formula (1), two nitrogen atoms are bonded to two carbon atoms among the carbon atoms constituting the ring structure having 3 to 8 carbon atoms, and these Each of the nitrogen atoms has a structure in which a hydroxyalkyl group having 2 to 4 carbon atoms (R ¹ and R ³ ) is bonded.

Thus, the diamine compound of the above general formula (1) in which a ring structure having 3 to 8 carbon atoms is directly bonded to two nitrogen atoms has a structure with large steric hindrance. For this reason, it is considered that bicarbonate ions are mainly generated in the reaction of the diamine compound of the general formula (1) and carbon dioxide (CO ₂ ), and the heat of reaction is reduced.

  By dissolving the diamine compound represented by the above general formula (1) (hereinafter referred to as the diamine compound (1)) in a solvent such as water, an acidic gas absorbent having a high acidic gas absorption ability is obtained. Can be obtained. In the following embodiments, the case where the acidic gas is carbon dioxide will be described as an example. However, the acidic gas absorbent according to the embodiment of the present invention obtains the same effect with respect to other acidic gases such as hydrogen sulfide. Can do.

In the above formula ^{(1), R 1, R} 3 is a group bonded to the nitrogen atom bonded to the ring structure of 3 to 8 carbon atoms, a hydroxyalkyl group having 2 to 4 carbon atoms. Here, the hydroxyalkyl group having 2 to 4 carbon atoms means a linear or branched alkyl group having 2 to 4 carbon atoms in which at least one hydrogen atom is substituted with a hydroxyl group.

However, R ^1, R ³ is a straight chain or of the hydrogen atoms of the branched chain alkyl group having 2 to 4 carbon atoms, hydrogen atoms bonded to carbon atoms other than carbon atom bonded to the nitrogen atom At least one is a group substituted with a hydroxyl group. That is, the hydroxyl group of R ^1, R ^3, among the carbon atoms constituting R ^1, R ^3, attached to a carbon atom other than a carbon atom bonded to the nitrogen atom. Hydroxyl group of R ^1, R ³ is, when attached to a carbon atom bonded to the nitrogen atom of the carbon atoms constituting R ^1, R ^3, stability of the entire diamine compound is reduced, stable acid gases Absorption performance may not be obtained.

R ¹ and R ³ may be the same or different from each other, but R ¹ and R ³ are preferably the same group from the viewpoint of enhancing the absorption performance for acidic gas.

R ¹ and R ³ are, for example, straight chain alkyl groups such as ethyl group, propyl group, and butyl group, and hydrogen atoms of branched alkyl groups such as isopropyl group, isobutyl group, and s-butyl group, A group in which at least one hydrogen atom bonded to a carbon atom other than the carbon atom bonded to the nitrogen atom is substituted with a hydroxyl group is exemplified.

When the number of carbon atoms of R ¹ and R ³ exceeds 4, the diamine compound (1) becomes highly hydrophobic, the solubility in a solvent such as water is lowered, and the reactivity with acidic gas may be lowered. . On the other hand, when the carbon number of R ¹ and R ³ is 1, stability as the diamine compound (1) is lowered, and there is a possibility that stable acid gas absorption performance cannot be obtained in the acid gas absorbent. Among these, it is preferable that the carbon number of R ¹ and R ³ is 2 from the viewpoint of reduction of heat of reaction and solubility in a solvent such as water.

Each of R ¹ and R ³ preferably has 2 or less hydroxyl groups. If the number of hydroxyl groups possessed by R ¹ and R ³ is 3 or more, the resulting acid gas absorbent may have an excessively high viscosity, and a sufficient amount of CO ₂ recovered may not be obtained. From the viewpoint of enhancing the absorption performance of CO ₂ , the number of hydroxyl groups each of R ¹ and R ³ preferably has is one.

Specific examples of R ¹ and R ³ include 2-hydroxyethyl group, 1-ethyl 2-hydroxyethyl group, 1,2-dimethyl-2-hydroxyethyl group, 2-hydroxy-2,2- Dimethylethyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 3-hydroxy-2-methylpropyl group, 2-hydroxyisopropyl group, 2,3-dihydroxypropyl group, 2,3-dihydroxyisopropyl group, 3- Hydroxy-2-methylpropyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group, 2,3-dihydroxybutyl group, 2,4-dihydroxybutyl group, 3,4-dihydroxybutyl group, Examples include 2,3,4-trihydroxybutyl group.

Among these, by making R ¹ and / or R ³ a 2-hydroxyethyl group, the reaction heat in the acid gas absorption reaction is reduced, the hydrophilicity is enhanced, and the solubility in a solvent such as water is also maintained. Is done. For this reason, high acid gas absorption performance can be obtained. In particular, both R ¹ and R ³ are preferably 2-hydroxyethyl groups.

R ² and R ⁴ are groups bonded to a nitrogen atom bonded to a ring structure having 3 to 8 carbon atoms, and represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

However, at least one of R ² and R ⁴ represents a hydrogen atom. When both of R ^2, R ⁴ is an alkyl group having 1 to 4 carbon atoms, reduced reactivity with an acidic gas, it does not provide sufficient acid gas absorption performance.

When the carbon number of R ² and R ⁴ exceeds 4, the hydrophobicity of the diamine compound (1) is increased, the solubility in a solvent is lowered, and the reactivity with acidic gas may be lowered. As R ² and R ⁴ , for example, hydrogen, methyl group, ethyl group, propyl group, or butyl group can be used. Among these, by making both R ² and R ⁴ hydrogen atoms, the heat of reaction between the diamine compound (1) and the acidic gas can be reduced, and the reactivity of the acidic gas absorbent with the acidic gas can be improved. Is preferable. In the alkyl group of R ² and R ⁴ , a part of hydrogen atoms may be substituted with a group containing atoms such as Si, O, N, and S. Specific examples of the group containing atoms such as Si, O, N, and S include a silanol group, a hydroxyl group, an amino group, and a mercapto group.

  x and y each independently represents an integer of 0 to 6 and 1 ≦ x + y ≦ 6. When x or y exceeds 6, or when x + y exceeds 6, the hydrophobicity of the diamine compound (1) increases, and the reactivity with acidic gas may decrease. On the other hand, when x + y is 0, a cyclic structure is not formed. Therefore, in the diamine compound (1), the steric hindrance of the whole molecule is small, and the effect of reducing the reaction heat in the acid gas absorption reaction cannot be sufficiently obtained. . x and y are each preferably 0 or more and 4 or less, and x + y is preferably 3 or more and 4 or less.

  As x and y are larger in the difference between the two values, the positions of the nitrogen atoms bonded to the ring structure having 3 to 8 carbon atoms are closer to each other, so that the solubility of the diamine compound (1) is enhanced and excellent acid gas absorption is achieved. It is preferable because performance can be obtained. That is, it is preferable that the smaller value of x and y is a value closer to 0. For example, when x + y = 4 (that is, when the ring structure is a cyclohexylene group), x = 4 and y = 0, the diamine compound (1) has x = 3, y = 1, or x = 2 Compared with the diamine compound (1) in which y = 2, the positions of the nitrogen atoms bonded to the ring structure having 3 to 8 carbon atoms are close, and high solubility can be obtained in the diamine compound (1). It is preferable because an acidic gas absorbent excellent in absorption performance for acidic gas can be obtained.

  Examples of the ring structure having 3 to 8 carbon atoms include cycloalkylene groups having 3 to 8 carbon atoms. Specific examples include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, and a cyclooctylene group. Among the above ring structures, a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, and a cyclohexylene group are preferable from the viewpoint of solubility in a solvent such as water. In particular, the cyclopentylene group and the cyclohexylene group can obtain high steric hindrance as a whole of the diamine compound (1) while maintaining good solubility, and have an effect of reducing the heat of reaction when absorbing the acidic gas. It is preferable because it can be enhanced and an excellent acid gas absorption capacity can be obtained.

  Moreover, the volatility of a diamine compound (1) is suppressed by having the above cyclic structures. For this reason, in the process which processes exhaust gas, it can be set as the acidic gas absorber with which the quantity of the amine component discharge | released in air | atmosphere was reduced.

  Examples of the diamine compound represented by the general formula (1) include 1,2-diaminocyclopropane-N, N′-diethanol, 1,2-diaminocyclopropane-N, N′-dipropanol, and 1,2-diamino. Cyclopropane-N, N′-dibutanol, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclopropane-1,2-diamine, N- (2-hydroxyethyl) -N′- (4-hydroxybutyl) cyclopropane-1,2-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclopropane-1,2-diamine, 1,2-diaminocyclobutane-N, N '-Diethanol, 1,2-diaminocyclobutane-N, N'-dipropanol, 1,2-diaminocyclobutane-N, N'-dibutanol, 1, -Diaminocyclobutane-N, N'-diethanol, 1,3-diaminocyclobutane-N, N'-dipropanol, 1,3-diaminocyclobutane-N, N'-dibutanol, N- (2-hydroxyethyl)- N ′-(3-hydroxypropyl) cyclobutane-1,2-diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxybutyl) cyclobutane-1,2-diamine, N-methyl-N, N '-Bis (2-hydroxyethyl) cyclobutane-1,2-diamine, N- (2-hydroxyethyl) -N'-(3-hydroxypropyl) cyclobutane-1,3-diamine, N- (2-hydroxyethyl) ) -N ′-(4-hydroxybutyl) cyclobutane-1,3-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) silane Such as Robutan-1,3-diamine.

  Examples of the diamine compound represented by the general formula (1) include 1,2-diaminocyclopentane-N, N′-diethanol, 1,2-diaminocyclopentane-N, N′-dipropanol, 1,2 -Diaminocyclopentane-N, N'-dibutanol, 1,3-diaminocyclopentane-N, N'-diethanol, 1,3-diaminocyclopentane-N, N'-dipropanol, 1,3-diaminocyclo Pentane-N, N′-dibutanol, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclopentane-1,2-diamine, N- (2-hydroxyethyl) -N ′-( 4-hydroxybutyl) cyclopentane-1,2-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclopentane-1,2-di Min, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclopentane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxybutyl) cyclopentane- 1,3-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclopentane-1,3-diamine and the like can be mentioned.

  Examples of the diamine compound represented by the general formula (1) include 1,2-diaminocyclohexane-N, N′-diethanol, 1,2-diaminocyclohexane-N, N′-dipropanol, and 1,2-diamino. Cyclohexane-N, N′-dibutanol, 1,3-diaminocyclohexane-N, N′-diethanol, 1,3-diaminocyclohexane-N, N′-dipropanol, 1,3-diaminocyclohexane-N, N ′ -Dibutanol, 1,4-diaminocyclohexane-N, N'-diethanol, 1,4-diaminocyclohexane-N, N'-dipropanol, 1,4-diaminocyclohexane-N, N'-dibutanol, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclohexane-1,2-diamine, -(2-hydroxyethyl) -N '-(2,3-dihydroxypropyl) cyclohexane-1,2-diamine, N- (2-hydroxyethyl) -N'-(4-hydroxybutyl) cyclohexane-1,2 -Diamine, N- (2-hydroxyethyl) -N '-(2,4-dihydroxybutyl) cyclohexane-1,2-diamine, N- (2-hydroxyethyl) -N'-(3,4-dihydroxybutyl ) Cyclohexane-1,2-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclohexane-1,2-diamine, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) ) Cyclohexane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(2,3-dihydroxypropyl) cyclohexane-1,3 Diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxybutyl) cyclohexane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(2,4-dihydroxybutyl) cyclohexane 1,3-diamine, N- (2-hydroxyethyl) -N ′-(3,4-dihydroxybutyl) cyclohexane-1,3-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) Cyclohexane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclohexane-1,4-diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxy Butyl) cyclohexane-1,4-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclohexane-1,4-diamine, etc. Can be mentioned.

  Examples of the diamine compound represented by the general formula (1) include 1,2-diaminocycloheptane-N, N′-diethanol, 1,2-diaminocycloheptane-N, N′-dipropanol, 1,2 -Diaminocycloheptane-N, N'-dibutanol, 1,3-diaminocycloheptane-N, N'-diethanol, 1,3-diaminocycloheptane-N, N'-dipropanol, 1,3-diaminocyclo Heptane-N, N′-dibutanol, 1,4-diaminocycloheptane-N, N′-diethanol, 1,4-diaminocycloheptane-N, N′-dipropanol, 1,4-diaminocycloheptane-N , N′-dibutanol, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cycloheptane-1,2-diamine, -(2-hydroxyethyl) -N '-(2,3-dihydroxypropyl) cycloheptane-1,2-diamine, N- (2-hydroxyethyl) -N'-(4-hydroxybutyl) cycloheptane-1 , 2-diamine, N- (2-hydroxyethyl) -N ′-(2,4-dihydroxybutyl) cycloheptane-1,2-diamine, N- (2-hydroxyethyl) -N ′-(3,4) -Dihydroxybutyl) cycloheptane-1,2-diamine, N-methyl-N, N'-bis (2-hydroxyethyl) cycloheptane-1,2-diamine, N- (2-hydroxyethyl) -N'- (3-hydroxypropyl) cycloheptane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxybutyl) cycloheptane-1,3-diamidine N-methyl-N, N′-bis (2-hydroxyethyl) cycloheptane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cycloheptane-1,4 -Diamine, N- (2-hydroxyethyl) -N '-(4-hydroxybutyl) cycloheptane-1,4-diamine, N-methyl-N, N'-bis (2-hydroxyethyl) cycloheptane-1 , 4-diamine and the like.

  Examples of the diamine compound represented by the general formula (1) include 1,2-diaminocyclooctane-N, N′-diethanol, 1,2-diaminocyclooctane-N, N′-dipropanol, 1,2 -Diaminocyclooctane-N, N'-dibutanol, 1,3-diaminocyclooctane-N, N'-diethanol, 1,3-diaminocyclooctane-N, N'-dipropanol, 1,3-diaminocyclo Octane-N, N′-dibutanol, 1,4-diaminocyclooctane-N, N′-diethanol, 1,4-diaminocyclooctane-N, N′-dipropanol, 1,4-diaminocyclooctane-N , N′-dibutanol, 1,5-diaminocyclooctane-N, N′-diethanol, 1,5-diaminocyclooctane-N, N ′ Dipropanol, 1,5-diaminocyclooctane-N, N′-dibutanol, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclooctane-1,2-diamine, N- (2 -Hydroxyethyl) -N '-(2,3-dihydroxypropyl) cyclooctane-1,2-diamine, N- (2-hydroxyethyl) -N'-(4-hydroxybutyl) cyclooctane-1,2- Diamine, N- (2-hydroxyethyl) -N ′-(2,4-dihydroxybutyl) cyclooctane-1,2-diamine, N- (2-hydroxyethyl) -N ′-(3,4-dihydroxybutyl ) Cyclooctane-1,2-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclooctane-1,2-diamine, N- (2-hydro) Siethyl) -N ′-(3-hydroxypropyl) cyclooctane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxybutyl) cyclooctane-1,3-diamine, N— Methyl-N, N′-bis (2-hydroxyethyl) cyclooctane-1,3-diamine, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclooctane-1,4-diamine, N- (2-hydroxyethyl) -N ′-(4-hydroxybutyl) cyclooctane-1,4-diamine, N-methyl-N, N′-bis (2-hydroxyethyl) cyclooctane-1,4- Diamine, N- (2-hydroxyethyl) -N ′-(3-hydroxypropyl) cyclooctane-1,5-diamine, N- (2-hydroxyethyl) -N ′-(4 -Hydroxybutyl) cyclooctane-1,5-diamine, N-methyl-N, N'-bis (2-hydroxyethyl) cyclooctane-1,5-diamine and the like.

  In addition, as a diamine compound (1), 1 type of compounds selected from said group can be used. Or as diamine compound (1), it is also possible to use what mixed 2 or more types of compounds selected from said group.

The content of the diamine compound (1) contained in the acid gas adsorbent is preferably 15 to 50% by mass. In general, the higher the concentration of the amine component, the greater the amount of carbon dioxide absorbed and desorbed per unit volume, and the higher the carbon dioxide absorption rate and desorption rate. In terms of processing efficiency, it is preferable.
However, if the concentration of the amine component in the absorption liquid is too high, the water contained in the absorbent cannot sufficiently exhibit the function as an activator for carbon dioxide absorption. On the other hand, when the concentration of the amine component in the absorbent is too high, defects such as an increase in the viscosity of the absorbent cannot be ignored. When the content of the diamine compound (1) is 50% by mass or less, phenomena such as an increase in the viscosity of the absorbent and a decrease in the function of water as an activator are not observed. Further, by setting the content of the diamine compound (1) to 15% by mass or more, a sufficient amount of carbon dioxide absorbed and absorption rate can be obtained, and excellent processing efficiency can be obtained.

  When the acid gas absorbent having a diamine compound (1) content in the range of 15 to 50% by mass is used for carbon dioxide recovery, it not only has high carbon dioxide absorption and carbon dioxide absorption rate, but also carbon dioxide. Desorption amount and carbon dioxide desorption rate are also high. For this reason, it is advantageous in that carbon dioxide can be efficiently recovered. The content of the diamine compound (1) is more preferably 20 to 50% by mass.

  The diamine compound (1) is mixed with a reaction accelerator composed of alkanolamines and / or a heterocyclic amine compound represented by the following general formula (2) (hereinafter referred to as a heterocyclic amine compound (2)). It is preferable to use it.

・・・（２）

... (2)

In the formula (2), ^{R 5} represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ⁶ represents an alkyl group having 1 to 4 carbon atoms bonded to a carbon atom. r represents an integer of 1 to 3, q represents an integer of 1 to 4, and p represents an integer of 0 to 12. When r is 2 to 3, nitrogen atoms are not directly bonded to each other. When q is 2, r is an integer of 1 or 2. Further, a part of hydrogen atoms of the alkyl group having 1 to 4 carbon atoms of R ⁵ and a part of hydrogen atoms of the alkyl group having 1 to 4 carbon atoms of R ⁶ are respectively substituted with a hydroxyl group and an amino group. Also good.

  In this embodiment, for example, a diamine compound (1) and a reaction accelerator composed of alkanolamines and / or a heterocyclic amine compound (2) can be mixed. And what made the mixture of diamine compound (1) and alkanolamines and / or heterocyclic amine compound (2) into aqueous solution, for example can be used as an acidic gas absorbent. By using the diamine compound (1) mixed with the alkanolamines and / or the heterocyclic amine compound (2), the amount of carbon dioxide absorbed per unit mole of the diamine compound (1) and the unit of the acid gas absorbent The amount of carbon dioxide absorbed per volume and the carbon dioxide absorption rate can be further improved. Moreover, the energy (acid gas desorption energy) which isolate | separates acidic gas after carbon dioxide absorption by using diamine compound (1) with alkanolamines and / or a heterocyclic amine compound (2) is also reduced. The energy for regenerating the acidic gas absorbent can be reduced.

  As the alkanolamine as the reaction accelerator, for example, an alkanolamine having no steric hindrance due to a cyclic structure as shown below can be used. Here, alkanolamine means a compound having an amino group and a hydroxyl group in one molecule. Specific examples of the alkanolamine as the reaction accelerator include monoethanolamine, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-dipropanolamine, and methylamino. Ethanol, ethylaminoethanol, propylaminoethanol, diethanolamine, bis (2-hydroxy-1-methylethyl) amine, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triethanolamine, dimethylamino-1-methylethanol, 2- Methylaminoethanol, 2-ethylaminoethanol, 2-propylaminoethanol, n-butylaminoethanol, 2- (isopropylamino) ethanol, 3-ethylaminopropanol, triethanolamine, diethano Triethanolamine and the like.

  Among these, alkanolamines include 2- (isopropylamino) ethanol, 2- (ethylamino) ethanol and 2-amino-2 from the viewpoint of further improving the reactivity between the diamine compound (1) and the acidic gas. It is preferably at least one selected from the group consisting of -methyl-1-propanol.

  Examples of the heterocyclic amine compound (2) include azetidine, 1-methylazetidine, 1-ethylazetidine, 2-methylazetidine, 2-azetidylmethanol, 2- (2-aminoethyl) azetidine, pyrrolidine, 1- Methylpyrrolidine, 2-methylpyrrolidine, 2-butylpyrrolidine, 2-pyrrolidylmethanol, 2- (2-aminoethyl) pyrrolidine, piperidine, 1-methylpiperidine, 2-ethylpiperidine, 3-propylpiperidine, 4-ethylpiperidine 2-piperidylmethanol, 3-piperidylethanol, 2- (2-aminoethyl) pyrrolidine, hexahydro-1H-azepine, hexamethylenetetramine, piperazine, piperazine derivatives and the like.

Among these, piperazine derivatives are particularly desirable from the viewpoint of improving the carbon dioxide absorption amount and absorption rate of the acidic gas absorbent. A piperazine derivative is a secondary amine compound, and generally, a nitrogen atom of a secondary amino group is bonded to carbon dioxide to form a carbamate ion, thereby contributing to an improvement in the absorption rate in the initial stage of the reaction. Further, the nitrogen atom of the secondary amino group plays a role of converting carbon dioxide bonded thereto to bicarbonate ion (HCO ₃ ⁻ ), and contributes to the speed increase in the latter half of the reaction.

  As piperazine derivatives, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, 1-methylpiperazine, 1- (2-hydroxyethyl) piperazine, 1- (2-aminoethyl) piperazine Of these, at least one of them is more preferable.

  The content of the reaction accelerator (alkanolamines and / or heterocyclic amine compound (2)) contained in the acidic gas adsorbent is preferably 1 to 15% by mass. If the content of the reaction accelerator contained in the acidic gas adsorbent is less than 1% by mass, the effect of improving the carbon dioxide absorption rate may not be sufficiently obtained. When the content of the reaction accelerator contained in the acidic gas adsorbent exceeds 15% by mass, the viscosity of the absorbent becomes excessively high, and the reactivity may be lowered.

  In addition to the above diamine compounds and reaction accelerators, acid gas absorbents include anticorrosives such as phosphoric acid to prevent corrosion of plant equipment, antifoaming agents such as silicone to prevent foaming, Further, an antioxidant for preventing deterioration of the acid gas absorbent may be contained.

  The method for removing acidic gas according to the present embodiment comprises contacting the exhaust gas containing acidic gas with the acidic gas absorbent obtained by dissolving the diamine compound described in the above embodiment in a solvent, and exhausting the gas containing acidic gas. The acid gas is absorbed and separated from the gas and removed.

  The basic structure of the carbon dioxide absorption and separation step is a step of bringing an acid gas absorbent into contact with an exhaust gas containing carbon dioxide and causing the acid gas absorbent to absorb carbon dioxide (carbon dioxide absorption step); Heating the acidic gas absorbent in which carbon dioxide has been absorbed obtained in the carbon dioxide absorption step, and desorbing and collecting carbon dioxide (carbon dioxide separation step).

  A method of bringing a gas containing carbon dioxide into contact with the aqueous solution containing the acid gas absorbent is not particularly limited. For example, a method of absorbing gas by bubbling a gas containing carbon dioxide in the acid gas absorbent; A method of dropping an acid gas absorbent into a gas stream containing gas (spraying or spraying), or in an absorption tower containing a magnetic filler or a metal mesh filler and gas containing carbon dioxide and acidity It is performed by a method of bringing the gas absorbent into countercurrent contact.

  The temperature of the acidic gas absorbent when the gas containing carbon dioxide is absorbed in the aqueous solution is usually from room temperature to 60 ° C. or less. Preferably it is 50 degrees C or less, More preferably, it is performed at about 20-45 degreeC. As the temperature is lowered, the amount of acid gas absorbed increases, but the lower limit of the processing temperature is determined by the gas temperature in the process, the heat recovery target, and the like. The pressure during carbon dioxide absorption is usually about atmospheric pressure. In order to enhance the absorption performance, the pressure can be increased to a higher pressure, but it is preferably performed under atmospheric pressure in order to suppress energy consumption required for compression.

  In the carbon dioxide absorption step, the amount of carbon dioxide absorbed at the time of carbon dioxide absorption (40 ° C.) of the acidic gas absorbent containing 15 to 50% by mass of the diamine compound according to the embodiment described above is 1 mol of amine contained in the absorbent. It is about 0.30 to 1.2 mol per unit. In addition, in the carbon dioxide absorption step, the acid gas absorbent containing 10 to 55% by mass of the diamine compound according to the above-described embodiment has a carbon dioxide absorption rate of 0. 0 minutes after the start of carbon dioxide absorption. It is about 32 to 0.38 mol / min.

  Here, the carbon dioxide saturated absorption amount is a value obtained by measuring the amount of inorganic carbon in the acidic gas absorbent with an infrared gas concentration measuring device. Further, the carbon dioxide absorption rate is a value measured using an infrared carbon dioxide meter when a few minutes have elapsed since the start of carbon dioxide absorption.

  As a method of separating carbon dioxide from the acid gas absorbent that has absorbed carbon dioxide and recovering pure or high-concentration carbon dioxide, the acid gas absorbent is heated and bubbled in a kettle and desorbed as in distillation. Examples thereof include a method, a plate tower, a spray tower, or a method in which a liquid interface is expanded and heated in a regeneration tower containing a magnetic filler or a metal mesh filler. Thereby, carbon dioxide is liberated and released from the carbamate anion and bicarbonate ion.

  The temperature of the acidic gas absorbent during carbon dioxide separation is usually 70 ° C or higher. The temperature of the acidic gas absorbent at the time of carbon dioxide separation is preferably 80 ° C. or higher, more preferably about 90 to 120 ° C. The higher the temperature, the greater the amount of desorption, but the higher the temperature, the greater the energy required to heat the absorbent. For this reason, the acidic gas absorbent temperature at the time of carbon dioxide separation is determined by the gas temperature in the process, the heat recovery target, and the like. The pressure during carbon dioxide desorption is usually about atmospheric pressure. Although the pressure can be reduced to a lower pressure in order to enhance the desorption performance, it is preferably performed under atmospheric pressure in order to suppress energy consumption required for the pressure reduction.

  The amount of carbon dioxide desorbed at the time of carbon dioxide desorption (70 ° C.) of the aqueous solution containing 15 to 50% by mass of the diamine compound according to the embodiment described above is 0.23 to 0.70 mol per mol of amine contained in the absorbent. Degree.

  The acidic gas absorbent after separating the carbon dioxide is sent again to the carbon dioxide absorption step and recycled (recycled). In addition, heat generated during carbon dioxide absorption is generally cooled by heat exchange in a heat exchanger in order to preheat the aqueous solution injected into the regeneration tower in the aqueous solution recycling process.

  The purity of the carbon dioxide recovered in this manner is usually as high as about 95 to 99% by volume. This pure carbon dioxide or high-concentration carbon dioxide is used as a chemical, a synthetic raw material for a polymer substance, a cooling agent for freezing foods, or the like. In addition, it is possible to sequester and store the recovered carbon dioxide in the underground, where technology is currently being developed.

  Of the steps described above, the step of separating the carbon dioxide from the acid gas absorbent to regenerate the acid gas absorbent is the portion that consumes the most amount of energy. In this step, about 50 to 80% of the entire process is consumed. A certain amount of energy is consumed. Therefore, the cost of the carbon dioxide absorption separation process can be reduced by reducing the energy consumption in the regeneration process of the acidic gas absorbent. For this reason, acid gas removal from exhaust gas can be performed economically advantageously.

  According to this embodiment, the energy required for carbon dioxide desorption (regeneration process) can be reduced by using the acidic gas absorbent of the above embodiment. For this reason, the absorption separation process of carbon dioxide can be performed on economically advantageous conditions.

  In addition, the diamine compound according to the above-described embodiment is remarkably high in corrosion resistance with respect to a metal material such as carbon steel as compared with alkanolamines such as 2-aminoethanol which has been conventionally used as an acid gas absorbent. have. Therefore, the acid gas removal method using such an acid gas absorbent eliminates the need to use high-cost high-grade corrosion-resistant steel in, for example, plant construction, which is advantageous in terms of cost.

  The acidic gas removal device according to the present embodiment is an acidic gas removal device that removes acidic gas from a gas containing acidic gas, and contains the acidic gas absorbent according to the above embodiment and contains acidic gas. An absorption tower that removes acidic gas from the gas by bringing a gas into contact with the acidic gas adsorbent, and an acidic gas absorbent having acidic gas absorbed by the absorption tower are housed, and the acidic gas adsorbent contains acidic gas. A regeneration tower that removes gas and regenerates the acid gas adsorbent that is reused in the absorption tower.

  FIG. 1 is a schematic view of an acidic gas removal apparatus according to an embodiment. The acidic gas removing device 1 includes an absorption tower 2 for contacting a gas containing acidic gas (hereinafter referred to as exhaust gas) with an acidic gas adsorbent and absorbing and removing the acidic gas from the exhaust gas, and an acidic gas. A regenerating tower 3 for separating the acid gas from the acid gas adsorbent that has absorbed the gas and regenerating the acid gas adsorbent. Hereinafter, the case where the acidic gas is carbon dioxide will be described as an example.

  As shown in FIG. 1, exhaust gas containing carbon dioxide, such as combustion exhaust gas discharged from a thermal power plant, is guided to the lower part of the absorption tower 2 through a gas supply port 4. The exhaust gas is pushed into the absorption tower 2 and is brought into contact with the acidic gas absorbent that is supplied from the acidic gas absorbent supply port 5 at the top of the absorption tower 2 and accommodated inside the absorption tower 2. As the acidic gas absorbent, the acidic gas absorbent according to the above-described embodiment is used.

  The pH value of the acidic gas absorbent may be adjusted to at least 9 or more. As for the pH value of the acidic gas absorbent, it is preferable to appropriately select the optimum condition depending on the type, concentration, flow rate, etc. of harmful gas contained in the exhaust gas. In addition to the above amine compounds and water and other solvents, the acidic gas absorbent may be any other compound such as a nitrogen-containing compound that improves carbon dioxide absorption performance, an antioxidant, and a pH adjuster. You may contain in the ratio.

  Thus, when the exhaust gas comes into contact with the acidic gas absorbent, carbon dioxide in the exhaust gas is absorbed by the acidic gas absorbent and removed. The exhaust gas after the carbon dioxide is removed is discharged from the gas outlet 6 to the outside of the absorption tower 2.

  The acidic gas absorbent that has absorbed carbon dioxide is sent to the heat exchanger 7 and the heater 8, heated, and then sent to the regeneration tower 3. The acidic gas absorbent sent to the inside of the regeneration tower 3 moves from the upper part to the lower part of the regeneration tower 3, and during this time, carbon dioxide in the acidic gas absorbent is desorbed and the acidic gas absorbent is regenerated.

  The acid gas absorbent regenerated in the regeneration tower 3 is sent to the heat exchanger 7 and the absorption liquid cooler 10 by the pump 9 and returned to the absorption tower 2 from the acid gas absorbent supply port 5.

  On the other hand, the carbon dioxide separated from the acidic gas absorbent comes into contact with the reflux water supplied from the reflux drum 11 at the top of the regeneration tower 3 and is discharged to the outside of the regeneration tower 3. The reflux water in which the carbon dioxide is dissolved is cooled by the reflux cooler 12 and then separated from the liquid component in which the water vapor accompanying the carbon dioxide is condensed in the reflux drum 11. Guided to carbon capture process. On the other hand, the reflux water from which carbon dioxide has been separated is sent to the regeneration tower 3 by the reflux water pump 14.

  According to the acidic gas removal device 1 of the present embodiment, it is possible to perform highly efficient absorption and removal of carbon dioxide by using an acidic gas absorbent excellent in carbon dioxide absorption characteristics and desorption characteristics.

As mentioned above, although embodiment of this invention was described referring a specific example, said Example is mentioned as an example of this invention and does not limit this invention.
In addition, in the description of each of the above embodiments, in the acidic gas absorbent, the acidic gas removal device, and the acidic gas removal method, the description of the portions that are not directly required for the explanation of the present invention is omitted. Each element to be used can be appropriately selected and used.

  In addition, all acid gas absorbents, acid gas removal devices, and acid gas removal methods that include elements of the present invention and that can be appropriately modified by those skilled in the art without departing from the spirit of the present invention are within the scope of the present invention. Is included. The scope of the present invention is defined by the appended claims and equivalents thereof.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1
1,2-Diaminocyclobutane-N, N′-diethanol was dissolved in water so as to be 45% by mass and piperazine was 5% by mass to obtain a 50 ml aqueous solution (hereinafter referred to as an absorbing solution). The absorption liquid is filled in a test tube and heated to 40 ° C., and a mixed gas containing 10% by volume of carbon dioxide (CO ₂ ) and 90% by volume of nitrogen (N ₂ ) gas is vented at a flow rate of 500 mL / min. The carbon dioxide (CO ₂ ) concentration in the gas at the outlet was measured using an infrared gas concentration measuring apparatus (manufactured by Shimadzu Corporation, trade name “CGT-700”) to evaluate the absorption performance. A 1/8 inch Teflon (registered trademark) tube (inner diameter: 1.59 mm, outer diameter: 3.17 mm) was used as a gas inlet to the amine aqueous solution in the test tube. Further, the aqueous solution after absorbing the mixed gas at 40 ° C. as described above is heated to 80 ° C., 100% nitrogen (N ₂ ) gas is vented at a flow rate of 500 mL / min, and the CO ₂ concentration in the absorbing solution is reduced. The emission performance was evaluated by measurement using an infrared gas concentration measuring device. The carbon dioxide absorption rate of the absorbing solution was the rate measured at a point two minutes after the start of carbon dioxide absorption.
The amount of carbon dioxide absorbed by the absorbing solution at 40 ° C. was 0.62 mol per mol of amine compound in the absorbing solution. The amount of carbon dioxide (CO ₂ ) absorbed by the absorbing solution at 80 ° C. was 0.14 mol per 1 mol of the amine compound. In the process of absorbing carbon dioxide (CO ₂ ) at 40 ° C. and desorbing carbon dioxide (CO ₂ ) at 80 ° C., 0.48 mol of CO ₂ was recovered per 1 mol of the amine compound. The CO ₂ absorption rate was 0.036 mol / L / min.

  The heat of reaction was measured as follows. Measure the reaction heat of carbon dioxide absorption by the absorbing solution using a differential thermal reaction calorimeter “DRC” (product name, manufactured by SETARAM) consisting of a glass reaction tank and a reference tank of the same shape installed in a thermostat did. Each of the reaction tank and the reference tank is filled with 150 mL of absorption liquid, and constant temperature water at 40 ° C. is circulated in the jacket portion of the tank. In this state, 100% carbon dioxide gas was blown into the absorption liquid in the reaction tank at 200 ml / min, and the temperature rise of the liquid was continuously recorded with a temperature recorder until the carbon dioxide absorption was completed, and measured in advance. The reaction heat was calculated using the overall heat transfer coefficient between the reaction vessel and the jacket water. The reaction heat of carbon dioxide absorption was 65 kJ / mol. In Examples 1 to 4 and Comparative Example 1, the heat of reaction indicates the heat of reaction per 1 mol of carbon dioxide contained in the absorbing solution.

(Example 2)
Absorbing solution (aqueous solution) in the same manner as in Example 1 except that 1,2-diaminocyclopentane-N, N′-diethanol was used instead of 1,2-diaminocyclobutane-N, N′-diethanol. Using the same apparatus as in Example 1, the carbon dioxide absorption amount, the carbon dioxide absorption rate, and the heat of reaction were measured under the same conditions.
The amount of carbon dioxide absorbed at 40 ° C. per mol of amine compound in the absorbing solution is 0.63 mol, the amount of carbon dioxide absorbed at 80 ° C. is 0.13 mol, and 0.50 mol per mol of amine compound in the absorbing solution. Of carbon dioxide was recovered. The CO ₂ absorption rate was 0.040 mol / L / min. The reaction heat of carbon dioxide absorption was 64 kJ / mol.

(Example 3)
An absorbing solution (aqueous solution) was prepared in the same manner as in Example 1 except that 1,2-diaminocyclobutane-N, N′-diethanol was used instead of 1,2-diaminocyclobutane-N, N′-diethanol. Using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the heat of reaction were measured under the same conditions.
The amount of carbon dioxide absorbed at 40 ° C. per mol of amine compound in the absorbing solution is 0.64 mol, the amount of carbon dioxide absorbed at 80 ° C. is 0.12 mol, and 0.52 mol per mol of amine compound in the absorbing solution. Of carbon dioxide was recovered. The CO ₂ absorption rate was 0.038 mol / L / min. The reaction heat of carbon dioxide absorption was 63 kJ / mol.

Example 4
50 ml of 1,2-diaminocyclobutane-N, N′-diethanol was dissolved in water so that 40% by mass, 2-amino-2-methyl-1-propanol was 5% by weight, and piperazine was 5% by mass. An absorption liquid was prepared, and the carbon dioxide absorption amount, the carbon dioxide absorption rate, and the reaction heat were measured using the same apparatus as in Example 1 under the same conditions as in Example 1.
The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amine compound in the absorbing solution is 0.65 mol, the amount of carbon dioxide absorbed at 80 ° C. is 0.15 mol, and 0.50 mol per mol of amine compound in the absorbing solution. Of carbon dioxide was recovered. The CO ₂ absorption rate was 0.039 mol / L / min. The reaction heat of carbon dioxide absorption was 66 kJ / mol.

(Comparative Example 1)
n-Butyldiethanolamine was dissolved in water so as to be 50% by mass and piperazine was 5% by mass to obtain 50 ml of an aqueous solution (hereinafter referred to as an absorbing solution). Thereafter, using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the reaction heat were measured under the same conditions as in Example 1.
The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amine compound in the absorbing solution is 0.20 mol, the amount of carbon dioxide absorbed at 80 ° C. is 0.08 mol, and 0.12 mol per mol of amine compound in the absorbing solution. Of carbon dioxide was recovered. The CO ₂ absorption rate was 0.023 mol / L / min. The reaction heat of carbon dioxide absorption was 64 kJ / mol.

In Table 1, with respect to Examples 1 to 4 and Comparative Example 1, together with the contents of the amine compound and reaction accelerator in the absorption liquid, the carbon dioxide absorption at 40 ° C., the carbon dioxide absorption at 80 ° C., carbon dioxide The recovery amount, carbon dioxide absorption rate, and reaction heat measurement results are shown.
In Table 1, the carbon dioxide absorption amount and the carbon dioxide recovery amount indicate the absorption amount and recovery amount per mole of the amine compound contained in the absorption liquid in terms of moles.

As is clear from Table 1, in the absorbing liquids of Examples 1 to 4 using a diamine compound having a cyclic alkyl group, both the carbon dioxide recovery amount and the carbon dioxide absorption rate are high, and the reaction at the time of carbon dioxide absorption. Low heat and excellent carbon dioxide absorption performance.
On the other hand, in Comparative Example 1 using butyldiethanolamine (BDEA) having a chain alkyl group as the amine compound, the amount of carbon dioxide recovered was as low as 0.12 mol and the carbon dioxide absorption rate was low. Moreover, the heat of reaction per 1 mol of carbon dioxide of the absorbing liquids of Examples 1 to 4 was substantially the same as that of the absorbing liquid of Comparative Example 1.

According to the acid gas absorbent, the acid gas removal method, and the acid gas removal device of at least one embodiment described above, the absorption amount and absorption rate of acid gas such as carbon dioxide can be increased, and the acid gas absorption The reaction heat at the time can be lowered.
Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Acid gas removal apparatus, 2 ... Absorption tower, 3 ... Regeneration tower, 4 ... Gas supply port, 5 ... Acid gas absorbent supply port, 6 ... Gas discharge port, 7 ... Heat exchanger, 8 ... Heater, 9 ... Pump, 10 ... Absorbent liquid cooler, 11 ... Reflux drum, 12 ... Reflux cooler, 13 ... Recovered carbon dioxide line, 14 ... Reflux water pump

Claims (9)

An acidic gas absorbent comprising at least one diamine compound having a carbocyclic structure represented by the following general formula (1).

... (1)
(In said formula (1), R < ¹ >, R < ³ > represents a C2-C4 hydroxyalkyl group, and may respectively be same or different, However, R < ¹ >, R < ³ > is linear Or, among the hydrogen atoms of a branched alkyl group having 2 to 4 carbon atoms, a group in which at least one hydrogen atom bonded to a carbon atom other than a carbon atom bonded to a nitrogen atom is substituted with a hydroxyl group R ² and R ^{4 each} represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that at least one of R ² and R ⁴ represents a hydrogen atom, and x and y each represents a nitrogen atom. the number of carbon atoms interposed coupling between directly bonded to two carbon atoms, x is an integer from 1 to 6, Ri 1 ≦ x + y ≦ 6 der, y is Ru 0 der.) The acidic gas absorbent according to claim ¹ , wherein in the diamine compound represented by the general formula (1), R ¹ and R ³ are 2-hydroxyethyl groups.   The acid gas adsorbent according to claim 1 or 2, wherein the content of the diamine compound represented by the general formula (1) is 15 to 50% by mass. A reaction accelerator comprising an alkanolamine and / or a heterocyclic amine compound represented by the following general formula (2) is further contained, and the content of the reaction accelerator is 1 to 15% by mass. The acid gas absorbent according to any one of the above.

... (2)
(In the above formula (2), ^{R 5} represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, ^{R 6} is a 1-3 .r represents an alkyl group having 1 to 4 carbon atoms bonded to carbon atoms Represents an integer, q represents an integer of 1 to 4, and p represents an integer of 0 to 12. When r is 2 to 3, nitrogen atoms are not directly bonded to each other.   The acidic gas absorption according to claim 4, wherein the alkanolamines are at least one selected from the group consisting of 2- (isopropylamino) ethanol, 2- (ethylamino) ethanol and 2-amino-2-methyl-1-propanol. Agent.   The acidic gas absorbent according to claim 4 or 5, wherein the heterocyclic amine compound includes at least one selected from the group consisting of piperazines.   The acidic gas absorbent according to claim 6, wherein the piperazine is at least one selected from the group consisting of piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, and 2,6-dimethylpiperazine.   An acid gas removal comprising: contacting a gas containing an acid gas with the acid gas adsorbent according to any one of claims 1 to 7 to remove the acid gas from the gas containing the acid gas. Method. An acid gas removing device for removing acid gas from gas containing acid gas,
An absorption tower for containing the acidic gas absorbent according to any one of claims 1 to 7, and contacting the acidic gas adsorbent with a gas containing an acidic gas to remove the acidic gas from the gas;
A regeneration tower that contains an acid gas absorbent having an acid gas absorbed in the absorption tower, removes the acid gas from the acid gas adsorbent, and regenerates the acid gas adsorbent that is reused in the absorption tower; An acid gas removing device having

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