JP2016129877A - Acid gas absorbent, acid gas removal method and acid gas removal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acid gas absorbent having a high acid gas (especially, CO) recovery amount (that is, the amount of absorption of the acid gas at a low temperature-the amount of desorption of the acid gas at a high temperature), particularly an acid gas absorbent where the desorption of the acid gas at a high temperature is easy and further which does not solidify at a low temperature, and to provide an acid gas removal device and an acid gas removal method using the same.SOLUTION: An acid gas absorbent containing tertiary alkanolamine represented as formula (1) (where, R, R, Rand Rare respectively independently a 1-4C substituted or unsubstituted alkyl group and Ris a 1-4C hydroxyalkyl group) and a reaction accelerator selected from the group consisting of a primary amine and a secondary amine and an acid gas removal device and an acid gas removal method using the absorbent are provided.SELECTED DRAWING: None

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 generation of carbon dioxide is largely due to industrial activities, and there is a growing momentum for reducing emissions.

  Development of energy-saving products, use of acid gas as a resource, sequestration storage technology, natural energy that does not emit acid gas, nuclear energy, etc. There is a conversion to alternative energy, and as one of them, separation and recovery technology of acid gas discharged is known.

  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 efficiently processing a large amount of gas, and its application to factories and power plants is being studied.

As a method mainly for thermal power plants that use fossil fuels, exhaust gas generated when burning fossil fuels (coal, oil, natural gas, etc.) is brought into contact with chemical absorbents, resulting in combustion exhaust gas. There are known methods for removing and recovering carbon dioxide, and methods for storing the recovered carbon dioxide. Further, it has been proposed to remove acidic gas such as hydrogen sulfide (H ₂ S) in addition to carbon dioxide 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 device can be easily increased in size.

  Examples of the alkanolamine used in the absorption method include 2-amino-2-methylpropanolamine, methylaminoethanol, ethylaminoethanol, propylaminoethanol, diethanolamine, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, and triethanolamine. There is.

  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.

  However, an amine having a large steric hindrance such as 2-amino-2-methyl-1-propanolamine has a relatively high melting point and has a problem that it is more likely to coagulate when absorbing carbon dioxide. Further, it is known to mix with other amines in order to enhance the absorption capacity, but when an amine that is solid at room temperature is mixed, it becomes easier to coagulate.

  In these techniques, the acid gas absorption capacity such as the acid gas absorption amount and the acid gas absorption rate is still insufficient, and further improvement of the gas absorption capacity is demanded.

JP 2008-307519 A Japanese Patent No. 2871334 U.S. Pat. No. 4,120,052 Korean open patent No. 2005-0007477 JP 2008-136989 A JP 7-246315 A Japanese Patent No. 3392609 Japanese Patent Laid-Open No. 10-249133 JP 7-258664 A JP-A-8-252430 Japanese Patent Laid-Open No. 7-130034

  The problem to be solved by the present invention is an acidic gas absorbent having a high recovery amount of acidic gas such as carbon dioxide (that is, absorption amount of acidic gas at low temperature−desorption amount of acidic gas at high temperature), particularly at high temperature. To provide an acidic gas absorbent that is easily desorbed of acidic gas and does not solidify even at low temperatures, and an acidic gas removing device and an acidic gas removing method using the same.

  The acidic gas absorbent according to the embodiment of the present invention includes a tertiary alkanolamine represented by the following general formula (1), a reaction accelerator selected from the group consisting of a primary amine and a secondary amine, It is characterized by containing.

（上記の一般式（１）において、Ｒ^１、Ｒ^２、Ｒ^４およびＲ^５は、それぞれ独立して、置換または非置換の炭素数１〜４のアルキル基を、Ｒ^３は炭素数１〜４のヒドロキシアルキル基を、表す。）

(In the above general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, and R ³ is 1 to 1 carbon atom. 4 represents a hydroxyalkyl group.)

  Then, the method for removing acidic gas according to the embodiment of the present invention is such that a gas containing acidic gas is brought into contact with the acidic gas absorbent according to the above-described embodiment of the present invention, and the acid gas is acidified from the gas containing the acidic gas. It is characterized by removing gas.

And the acidic gas removal apparatus of embodiment of this invention makes the acidic gas containing the acidic gas and the acidic gas absorbent of embodiment of the above-mentioned this invention contact, and makes this acidic gas absorbent absorb acidic gas. An absorber for removing the acid gas from the gas containing the acid gas,
A regenerator that regenerates the acidic gas absorbent by desorbing the acidic gas from the acidic gas absorbent that has absorbed the acidic gas,
The acidic gas absorbent regenerated by the regenerator is reused by the absorber.

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 contains a tertiary alkanolamine represented by the following general formula (1) and a reaction accelerator selected from the group consisting of a primary amine and a secondary amine. It is characterized by this.

（上記の一般式（１）において、Ｒ^１、Ｒ^２、Ｒ^４およびＲ^５は、それぞれ独立して、置換または非置換の炭素数１〜４のアルキル基を、Ｒ^３は炭素数１〜４のヒドロキシアルキル基を、表す。）

(In the above general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, and R ³ is 1 to 1 carbon atom. 4 represents a hydroxyalkyl group.)

<Tertiary alkanolamine>
Conventionally, it is known that the steric hindrance of an amine compound has a large influence on a product upon absorption of an acidic gas, 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. However, for example, an amine having a large steric hindrance such as 2-amino-2-methyl-1-propanolamine has a relatively high melting point and has a problem that it is more easily solidified when CO _{2 is} absorbed. It is known that one or more other amines are mixed in order to further increase the absorption capacity. However, if an amine that is a solid at room temperature is mixed at that time, the mixed absorbing solution is more easily solidified.

As a result of investigations by the present inventors, an absorption liquid containing a tertiary alkanolamine represented by the general formula (1), a compound, and at least one primary or secondary amine has been conventionally used. The acid compounds (for example, carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), carbonyl sulfide (COS), sulfur oxide (SOx), even though they are not solidified even at low temperatures, compared to amine compounds having a large steric hindrance. It has been found that it exhibits high absorption performance with respect to nitrogen oxide (NOx) and hydrogen chloride (HCl).

That is, in the tertiary alkanolamine represented by the general formula (1), the carbon to which two substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms (R ¹ and R ² ) are bonded is a nitrogen atom. And two substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms (R ⁴ and R ⁵ ) are directly bonded to the nitrogen atom.

R ¹ and R ² are substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms, for example, branched or straight chain such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, and s-butyl group. -Like alkyl groups. These alkyl groups may be substituted with a group containing a hetero atom such as Si, O, N, and S. When the carbon number of R ¹ or R ² exceeds 5, the tertiary alkanolamine represented by the above general formula (1) becomes highly hydrophobic, the solubility in the solvent decreases, and the acid gas Reactivity may be reduced. Among the above structures, a methyl group or an ethyl group is particularly preferable from the viewpoint of solubility in a solvent such as water.

R ³ is a hydroxyalkyl group. From the viewpoint of improving the reactivity with acidic gas, a hydroxyalkyl group having 1 to 4 carbon atoms is preferred. The hydroxyalkyl group is more preferably a 2-hydroxymethyl group.

R ⁴ and R ⁵ are substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms, such as a branched or straight chain such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, and s-butyl group. The alkyl group can be used, and these alkyl groups may be substituted with a group containing a hetero atom such as Si, O, N, and S. When the number of carbon atoms in R ⁴ or R ⁵ exceeds 5, the hydrophobicity of the tertiary alkanolamine represented by the general formula (1) increases, the solubility in the solvent decreases, and the reactivity with the acid gas is reduced. May decrease. Among the above structures, a methyl group or an ethyl group is preferable from the viewpoint of solubility in a solvent such as water and viscosity. Since R ⁴ and R ⁵ are bonded to an amino group, the solidification property of the absorbing solution is reduced, and although the steric hindrance is large, it does not solidify even at a low temperature and exhibits high acid gas absorption performance.

  Thus, the compound represented by the general formula (1) is a tertiary amine having a structure having a large steric hindrance. For this reason, in the reaction of the tertiary alkanolamine of the general formula (1) and the acidic gas (carbon dioxide), bicarbonate ions are generated, so that the reaction heat can also be reduced.

  By dissolving the tertiary alkanolamine represented by the general formula (1) in a solvent such as water, an acid gas absorbent having a high acid gas absorption ability 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 addition, since the volatility is suppressed by adopting a tertiary alkanolamine structure, an acidic gas absorbent in which the amount of amine component released into the atmosphere is reduced in the process of treating exhaust gas can be obtained. it can. In the acidic gas absorbent according to the embodiment, precipitation is suppressed.

Examples of the tertiary alkanolamine represented by the general formula (1) include 2- (dimethylamino) -2-methyl-1-propanol,
2- (dimethylamino) -2-ethyl-1-propanol,
2- (dimethylamino) -2-propyl-1-propanol,
2- (dimethylamino) -2-isopropyl-1-propanol,
2- (dimethylamino) -2-butyl-1-propanol,
2- (dimethylamino) -2-sec-butyl-1-propanol,
2- (dimethylamino) -2-tert-butyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-methyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-ethyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-propyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-isopropyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-butyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-sec-butyl-1-propanol,
2- (N-methyl-N-ethylamino) -2-tert-butyl-1-propanol,
2- (diethylamino) -2-methyl-1-propanol,
2- (diethylamino) -2-ethyl-1-propanol,
2- (diethylamino) -2-propyl-1-propanol 2- (diethylamino) -2-isopropyl-1-propanol,
2- (diethylamino) -2-butyl-1-propanol,
2- (diethylamino) -2-sec-butyl-1-propanol,
2- (diethylamino) -2-tert-butyl-1-propanol,
2- (N-methyl-N-propylamino) -2-methyl-1-propanol,
2- (N-methyl-N-propylamino) -2-ethyl-1-propanol,
2- (N-methyl-N-propylamino) -2-propyl-1-propanol,
2- (N-methyl-N-propylamino) -2-isopropyl-1-propanol,
2- (N-methyl-N-propylamino) -2-butyl-1-propanol,
2- (N-methyl-N-propylamino) -2-sec-butyl-1-propanol,
2- (N-methyl-N-propylamino) -2-tert-butyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-methyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-ethyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-propyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-isopropyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-butyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-sec-butyl-1-propanol,
2- (N-methyl-N-isopropylamino) -2-tert-butyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-methyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-ethyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-propyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-isopropyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-butyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-sec-butyl-1-propanol,
2- (N-ethyl-N-propylamino) -2-tert-butyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-methyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-ethyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-propyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-isopropyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-butyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-sec-butyl-1-propanol,
2- (N-ethyl-N-isopropylamino) -2-tert-butyl-1-propanol,
2- (N-propyl-N-propylamino) -2-methyl-1-propanol,
2- (N-propyl-N-propylamino) -2-ethyl-1-propanol,
2- (N-propyl-N-propylamino) -2-propyl-1-propanol,
2- (N-propyl-N-propylamino) -2-isopropyl-1-propanol,
2- (N-propyl-N-propylamino) -2-butyl-1-propanol,
2- (N-propyl-N-propylamino) -2-sec-butyl-1-propanol,
2- (N-propyl-N-propylamino) -2-tert-butyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-methyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-ethyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-propyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-isopropyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-butyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-sec-butyl-1-propanol,
2- (N-propyl-N-isopropylamino) -2-tert-butyl-1-propanol,
2- (dimethylamino) -2-methyl-1-butanol,
2- (dimethylamino) -2-ethyl-1-butanol,
2- (dimethylamino) -2-propyl-1-butanol,
2- (dimethylamino) -2-isopropyl-1-butanol,
2- (dimethylamino) -2-butyl-1-butanol,
2- (dimethylamino) -2-sec-butyl-1-butanol,
2- (dimethylamino) -2-tert-butyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-methyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-ethyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-propyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-isopropyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-butyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-sec-butyl-1-butanol,
2- (N-methyl-N-ethylamino) -2-tert-butyl-1-butanol,
2- (diethylamino) -2-methyl-1-butanol,
2- (diethylamino) -2-ethyl-1-butanol,
2- (diethylamino) -2-propyl-1-butanol 2- (diethylamino) -2-isopropyl-1-butanol,
2- (diethylamino) -2-butyl-1-butanol,
2- (diethylamino) -2-sec-butyl-butanol,
2- (diethylamino) -2-tert-butyl-1-butanol,
And so on.

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

  The content of the tertiary alkanolamine contained in the acid gas absorbent is preferably 20 to 55% by mass (the total amount of the acid gas absorbent is 100% by mass). In general, the higher the concentration of the amine component, the greater the amount of absorption and desorption of acidic gas (particularly carbon dioxide) per unit volume, and the higher the absorption rate and desorption rate of acidic gas. It is preferable in terms of the size of the plant equipment and the processing efficiency. However, if the concentration of the amine component in the absorption liquid is too high, the water contained in the absorption liquid cannot sufficiently exhibit the function as an activator for acid gas absorption. Moreover, if the concentration of the amine component in the absorbing solution is too high, defects such as an increase in the viscosity of the absorbing solution cannot be ignored. When the content of the tertiary alkanolamine is 55% by mass or less, phenomena such as an increase in the viscosity of the absorbing solution and a decrease in the function of water as an activator are not observed. Further, by setting the content of the tertiary alkanolamine to 20% by mass or more, it is possible to obtain a sufficient amount of absorption and absorption rate of acidic gas, and to obtain excellent processing efficiency.

  When the acid gas absorbent having a tertiary alkanolamine content in the range of 20 to 55% by mass is used for acid gas recovery (particularly carbon dioxide), the acid gas absorption amount and the acid gas absorption rate are high. In addition, the acid gas desorption amount and the acid gas desorption rate are high. For this reason, it is advantageous in that carbon dioxide can be efficiently recovered. The content of the tertiary alkanolamine is more preferably 30 to 50% by mass.

<Reaction accelerator>
The acidic gas absorbent according to the embodiment of the present invention further contains a reaction accelerator selected from the group consisting of a primary amine and a secondary amine.

  Preferable specific examples of such a reaction accelerator include, for example, a heterocyclic amine compound represented by the following general formula (2).

In the above general formula (2), R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁷ represents an alkyl group having 1 to 4 carbon atoms bonded to a carbon atom forming a heterocycle, Represent. p represents an integer of 1 to 3, q represents an integer of 1 to 4, and r represents an integer of 0 to 12. However, when r is 2 to 3, nitrogen atoms are not directly bonded to each other. 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 ⁷ are respectively substituted with a hydroxyl group and an amino group. Also good.

The other amine compound as the reaction accelerator is preferably a primary or secondary alkanolamine, such as monoethanolamine,
2-amino-2-methyl-1-propanol,
2-amino-2-methyl-1,3-dipropanol,
Diethanolamine,
2-methylaminoethanol,
2-ethylaminoethanol,
2-propylaminoethanol,
n-butylaminoethanol,
2- (isopropylamino) ethanol,
Examples include 3-ethylaminopropanol.

  Here, alkanolamine means a compound having an amino group and a hydroxyl group in one molecule.

  Among these, the alkanolamines are at least selected from the group consisting of monoethanolamine, 2-methylaminoethanol and 2-ethylaminoethanol from the viewpoint of further improving the reactivity between the tertiary amine and the acidic gas. One type is preferred.

In particular, examples of the heterocyclic amine compound (2) include azetidine,
2-methylazetidine,
2-ethylazetidine,
2-azetidylmethanol,
2- (2-aminoethyl) azetidine,
Pyrrolidine,
2-methylpyrrolidine,
2-ethylpyrrolidine,
2-pyrrolidylmethanol,
2- (2-aminoethyl) pyrrolidine,
Piperidine,
2-methylpiperidine,
2-ethylpiperidine,
3-methylpiperidine,
3-ethylpiperidine,
2-piperidinemethanol,
2-piperidine ethanol,
3-piperidinemethanol,
3-piperidine ethanol,
4-piperidine methanol,
4-piperidine ethanol,
2- (2-aminoethyl) pyrrolidine,
Hexahydro-1H-azepine,
Examples include piperazine and piperazine derivatives.

  By using a tertiary alkanolamine mixed with a primary or secondary amine, the amount of acidic gas absorbed per unit mole of tertiary alkanolamine and the amount of acidic gas absorbed per unit volume of the acidic gas absorbent The amount and the acid gas absorption rate can be further improved. Further, by using a tertiary alkanolamine mixed with a primary or secondary amine, the energy for separating the acidic gas after absorbing the acidic gas (acid gas desorption energy) is also reduced, and the acidic gas absorbent The energy at the time of regenerating can be reduced.

Among these, piperazine and piperazine derivatives are particularly desirable from the viewpoint of improving the carbon dioxide absorption amount and absorption rate of the acidic gas absorbent. Piperazine and piperazine derivatives are secondary amine compounds. In general, 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 an increase in the speed 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 contained in the acidic gas absorbent is preferably 1 to 10% by mass (the total amount of the acidic gas absorbent is 100% by mass). If the content of the reaction accelerator contained in the acidic gas absorbent 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 absorbent exceeds 10% by mass, the viscosity of the absorbent becomes excessively high, and the reactivity may be lowered.

<Other components (optional components)>
The acidic gas absorbent according to the embodiment of the present invention includes a tertiary alkanolamine represented by the general formula (1) and a reaction accelerator selected from the group consisting of a primary amine and a secondary amine. For example, after being mixed with a solvent such as water and various auxiliary materials as necessary, it is suitable as an acid gas absorption method or an acid gas absorbent for an acid gas absorber, for example. Here, specific examples of the auxiliary material include, for example, an antioxidant, a pH adjuster, an antifoaming agent, an anticorrosive and the like.

  When water is used as the solvent, the content thereof is preferably 35 to 79% by mass, particularly preferably 40 to 70% by mass (the total amount of the acid gas absorbent is 100% by mass). When the water content is within this range, it is preferable in terms of improving the acid gas absorption rate and reducing the viscosity of the absorbing solution.

  Preferable specific examples of the antioxidant include, for example, dibutylhydroxytoluene (BHT), butylhydroxyanisole (BHA), sodium erythorbate, sodium sulfite, sulfur dioxide, phenolic antioxidants, mercaptoimidazoles and mercaptobenzimidazoles. Can be mentioned. When using antioxidant, the content becomes like this. Preferably it is 0.01-10 mass%, Most preferably, it is 0.1-3 mass% (The total amount of an acidic gas absorber is 100 mass%). The antioxidant can prevent deterioration of the acid gas absorbent and improve durability.

  Preferable specific examples of the pH adjuster include citric acid, gluconic acid, sodium hydroxide, and sodium hydrogen carbonate. When using a pH adjuster, the content is preferably 0.1 to 10% by mass, particularly preferably 0.1 to 3% by mass (the total amount of the acid gas absorbent is 100% by mass).

  Preferable specific examples of the antifoaming agent include, for example, a silicone antifoaming agent and an organic antifoaming agent. When the antifoaming agent is used, the content is preferably 0.0001 to 0.1% by mass, particularly preferably 0.001 to 0.01% by mass (the total amount of the acid gas absorbent is 100% by mass). And). The antifoaming agent prevents foaming of the acidic gas absorbent, suppresses a decrease in the absorption efficiency and separation efficiency of the acidic gas, and prevents a decrease in fluidity or circulation efficiency of the acidic gas absorbent.

  Preferred specific examples of anticorrosives include, for example, nitrite anticorrosives, chromate anticorrosives, phosphonate anticorrosives, triazole anticorrosives, metal carbonates, alkali metal carbonates and metal oxides. Can do. When the anticorrosive agent is used, the content thereof is preferably 0.0001 to 1% by mass, particularly preferably 0.001 to 0.1% by mass (the total amount of the acid gas absorbent is 100% by mass). . Such an anticorrosive can prevent corrosion of plant equipment and improve durability.

<Method for removing acid gas>
The method for removing an acidic gas according to an embodiment of the present invention includes contacting a gas containing an acidic gas with the acidic gas absorbent according to the above-described embodiment to remove the acidic gas from the gas containing the acidic gas. , Is characterized by.

  The method for removing acid gas according to the embodiment of the present invention includes a step of absorbing the acid gas to the acid gas absorbent according to the above-described embodiment of the present invention (absorption step), and the above-described present invention that has absorbed the acid gas. The step of desorbing the acidic gas from the acidic gas absorbent according to the embodiment has a basic configuration.

  That is, the basic configuration of the acid gas removal method according to the embodiment of the present invention is to bring an acid gas absorbent into contact with a gas containing an acid gas (for example, exhaust gas), so that the acid gas absorbent is acidic. A step of absorbing the gas (acid gas absorption step) and a step of heating and removing the acid gas absorbed in the acid gas obtained in the acid gas absorption step to remove and remove the acid gas ( Acid gas separation step).

  The method of bringing the gas containing the acid gas into contact with the aqueous solution containing the acid gas absorbent is not particularly limited. For example, the gas containing the acid gas is bubbled into the acid gas absorbent to cause the absorbent to contain the acid gas. In a gas stream containing acid gas, a method of dropping the acid gas absorbent into a mist (spraying or spraying method), or in an absorber containing a magnetic, polymer, or metal mesh filler The gas containing acid gas and the acid gas absorbent can be countercurrently contacted with each other.

  The temperature of the acidic gas absorbent when the gas containing the acidic gas is absorbed in the aqueous solution can be usually from room temperature to 60 ° C. or less. Preferably it is 50 degrees C or less, More preferably, it can carry out at about 20-45 degreeC. The lower the temperature, the higher the amount of acid gas absorbed, but the lower limit of the processing temperature can be determined by the process gas temperature, heat recovery target, etc. Depending on the pressure inside, it is carried out at pressures from about atmospheric to higher. Although it is possible to pressurize to a higher pressure in order to enhance the absorption performance, it is preferable to carry out under atmospheric pressure or the pressure of the processing gas in order to suppress energy consumption required for compression.

  In the acidic gas absorption process, the acidic gas absorbent containing 20 to 55% by mass of the tertiary alkanolamine according to the above-described embodiment and 1 to 10% by mass of the reaction accelerator is carbon dioxide at the time of carbon dioxide absorption (40 ° C.). The amount of carbon absorption is about 0.3 to 0.8 mol per mol of amine contained in the absorbent.

  Here, the acid gas saturation absorption amount is a value obtained by measuring the amount of carbon dioxide in the acid gas absorbent with an infrared gas concentration measuring device.

  As a method of separating the acid gas from the acid gas absorbent that has absorbed the acid gas and recovering the pure or high-concentration acid gas, the acid gas absorbent is heated and bubbled in a kettle and desorbed as in distillation. Examples thereof include a method of heating the plate by spreading the liquid interface in a regenerator containing a shelf, a sprayer, a magnetic or polymer filler, or a metal mesh filler. Thereby, acidic gas is liberated and released from carbamate anions and bicarbonate ions.

  The temperature of the acidic gas absorbent during the acidic gas separation is usually 70 ° C. or higher, preferably 80 ° C. or higher, more preferably about 90 to 130 ° 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, so that the temperature can be determined by the process gas temperature, heat recovery target, etc. The pressure at the time of acid gas desorption is usually at atmospheric pressure or higher. In order to enhance the desorption performance, the pressure can be reduced to a pressure lower than the atmospheric pressure. However, it is preferable to carry out at an atmospheric pressure or higher in order to suppress energy consumption required for the pressure reduction.

  The acid gas desorption amount at the time of acid gas desorption (120 ° C.) of the acid gas absorbent containing 20 to 55% by mass of the tertiary alkanolamine and 1 to 10% by mass of the reaction accelerator according to the embodiment described above is The amount is about 0.3 to 0.70 mol per mol of amine contained in the absorbent.

  The acid gas absorbent after separating the acid gas can be sent to the acid gas absorption process again and recycled (recycled). In addition, the heat generated during acid gas absorption is generally cooled by heat exchange in a heat exchanger in order to preheat the aqueous solution injected into the regenerator during the aqueous solution recycling process.

  The purity of the acid gas recovered in this way is usually as high as about 95 to 99% by volume. This pure acid gas or high-concentration acid gas can be 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.

  Among the steps described above, the step of separating the acid gas from the acid gas absorbent and regenerating the acid gas absorbent is the portion that consumes the most amount of energy, and in this step, about 50 to 80% of the entire process. Some degree of energy may be consumed. Therefore, the cost of the acid gas absorption separation process can be reduced by reducing the energy consumption in the regeneration process of the acid gas absorbent. For this reason, acid gas removal from exhaust gas can be performed economically advantageously.

  According to this embodiment, by using the acid gas absorbent of the above embodiment, acid gas desorption at a high temperature is easy and a large acid gas recovery amount can be obtained, and acid gas desorption (regeneration step). The energy required for this can be reduced. For this reason, the acid gas absorption and separation step can be performed under economically advantageous conditions.

<Acid gas removal device>
The acidic gas removal apparatus according to the embodiment of the present invention makes a gas containing an acidic gas contact the acidic gas absorbent according to the specific embodiment of the present invention described above, and causes the acidic gas absorbent to absorb the acidic gas. An absorber that removes the acid gas from the gas containing the acid gas, and a regenerator that regenerates the acid gas absorbent by desorbing the acid gas from the acid gas absorbent that has absorbed the acid gas, And an acid gas removing device that reuses the acid gas absorbent regenerated by the regenerator in the absorber.

  FIG. 1 is a schematic view of an acidic gas removal apparatus according to an embodiment.

  This acid gas removal device absorbs an acid gas, and an absorber 2 for contacting the gas containing the acid gas (for example, exhaust gas) with an acid gas absorbent and absorbing and removing the acid gas from the exhaust gas. A regenerator 3 for separating the acidic gas from the acidic gas absorbent and regenerating the acidic gas absorbent. 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 or the like is guided to the lower part of the absorber 2 through a gas supply port 101. This exhaust gas is pushed into the absorber 2 and is supplied from the acidic gas absorbent supply port 102 above the absorber 2 and comes into contact with the acidic gas absorbent accommodated in the absorber 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 compound and a solvent such as water, the acidic gas absorbent may be any other compound such as a nitrogen-containing compound that improves the absorption performance of carbon dioxide, 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 from which carbon dioxide has been removed is discharged from the gas outlet 103 to the outside of the absorber 2.

  The acidic gas absorbent that has absorbed carbon dioxide is sent to the heat exchanger 4, heated, and then sent to the regenerator 3. The acidic gas absorbent sent to the inside of the regenerator 3 moves from the upper part to the lower part of the regenerator 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 by the regenerator 3 is sent to the heat exchanger 4 and the absorption liquid cooler 5 and returned to the absorber 2 from the acid gas absorbent supply port 102.

  On the other hand, the carbon dioxide separated from the acid gas absorbent is discharged from the top of the regenerator 3 to the outside of the regenerator 3.

  The gas containing carbon dioxide discharged from the regenerator 3 is cooled by the reflux cooler 7 and then separated from the liquid component in which water vapor and amine accompanied by carbon dioxide are condensed in the reflux drum 6, and the recovered carbon dioxide line 108. This leads to the carbon dioxide recovery process. On the other hand, the reflux water from which carbon dioxide has been separated is sent to the regenerator 3.

  According to the acidic gas removal device of this 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.

  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>
2- (dimethylamino) -2-methyl-1-propanol (DMAP) is dissolved in water so as to be 40% by mass and piperazine (PZ) is 3% by mass, and 50 ml of an aqueous solution (hereinafter referred to as an absorbing solution). ). The absorbent is filled in a test tube and heated to 40 ° C., and a mixed gas containing 10% by volume of carbon dioxide and 90% by volume of nitrogen (N ₂ ) gas is aerated at a flow rate of 500 mL / min for 3 hours, and at the test tube outlet. The carbon dioxide concentration in the gas was measured using an infrared gas concentration measuring device (manufactured by Shimadzu Corporation, trade name “CGT-7000”) 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.

  Also, 50 mL of the absorbing solution is filled into a test tube and heated to 120 ° C., and a mixed gas containing 10% by volume of carbon dioxide and 90% by volume of nitrogen gas is aerated at a flow rate of 100 mL / min for 1 hour, and the partial pressure of carbon dioxide in the test tube Was adjusted to about 10 kPa, the carbon dioxide concentration was measured using an infrared gas concentration measuring device, and the absorption performance was evaluated.

  As a result, the carbon dioxide absorption amount of the absorbing solution at 40 ° C. was 0.60 mol per mol of the amino compound in the absorbing solution. The amount of carbon dioxide absorbed by the absorbing solution at 120 ° C. was 0.10 mol per 1 mol of amino compound, and the amount of carbon dioxide recovered as the difference between 40 ° C. and 120 ° C. was 0.50 mol. The carbon dioxide absorption rate was 0.030 mol / L / min.

The coagulability is confirmed visually by placing 20 ml of the absorbing solution absorbed with CO ₂ at 40 ° C. before absorption of carbon dioxide and placing it in a glass vial, and placing it in a refrigerator having an internal temperature of about 5 to 8 ° C. for 12 hours. did.
As a result, neither the carbon dioxide-absorbed solution nor the absorbent absorbed at 40 ° C. solidified.

<Example 2>
An absorbing solution (aqueous solution) was prepared in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and piperazine was 5% by mass. Using the same apparatus as in Example 1, the carbon dioxide absorption, carbon dioxide absorption rate, and coagulability were measured under the same conditions.

The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution is 0.65 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.14 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.51 mol. The carbon dioxide absorption rate was 0.036 mol / L / min.
Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 3>
An absorbent solution (aqueous solution) was prepared in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and piperazine was 15% by mass. Using the same apparatus as in Example 1, the carbon dioxide absorption, carbon dioxide absorption rate, and coagulability were measured under the same conditions.

The absorption amount of carbon dioxide at 40 ° C. per 1 mol of amino compound in the absorption liquid is 0.70 mol, and the absorption amount of carbon dioxide in the absorption liquid at 120 ° C. is 0.23 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.47 mol. The carbon dioxide absorption rate was 0.040 mol / L / min.
Moreover, both the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption coagulated.

<Example 4>
An absorbent (aqueous solution) was prepared in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 30% by mass and piperazine was 5% by mass. Using the same apparatus as in Example 1, the carbon dioxide absorption, carbon dioxide absorption rate, and coagulability were measured under the same conditions.

The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution is 0.80 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.20 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.60 mol. The carbon dioxide absorption rate was 0.036 mol / L / min.
Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 5>
An absorbent solution was prepared in the same manner as in Example 1 except that 60% by mass of 2- (dimethylamino) -2-methyl-1-propanol and 5% by mass of piperazine were dissolved in water. Using the same apparatus as in No. 1, carbon dioxide absorption, carbon dioxide absorption rate, and coagulability were measured under the same conditions.

The amount of carbon dioxide absorbed at 40 ° C. per mol of amino compound in the absorbing solution is 0.44 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.10 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.34 mol. The CO ₂ absorption rate was 0.034 mol / L / min.
Further, the absorption liquid before CO ₂ absorption solidified, and the absorption liquid absorbed with carbon dioxide at 40 ° C. did not solidify.

<Example 6>
An absorption liquid (aqueous solution) was prepared in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 15 mass% and piperazine was 5 mass%. Using the same apparatus as in Example 1, the carbon dioxide absorption, carbon dioxide absorption rate, and coagulability were measured under the same conditions.

The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution is 0.85 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.30 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.55 mol. The carbon dioxide absorption rate was 0.033 mol / L / min.
Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 7>
Absorbent solution (aqueous solution) in the same manner as in Example 1 except that 2- (ethylmethylamino) -2-methyl-1-propanol (EMAMP) was dissolved in water so that 40% by mass and piperazine was 5% by mass. ), And using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The absorption amount of carbon dioxide at 40 ° C. per 1 mol of amino compound in the absorption liquid is 0.50 mol, and the absorption amount of carbon dioxide in the absorption liquid at 120 ° C. is 0.08 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.42 mol. The carbon dioxide absorption rate was 0.035 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 8>
Absorbent solution (aqueous solution) in the same manner as in Example 1 except that 2- (dimethylamino) -2-ethyl-1-propanol (DMAEP) was dissolved in water so that 40% by mass and piperazine was 5% by mass. Using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulability were measured under the same conditions.

  The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution is 0.59 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.12 mol per 1 mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.47 mol. The carbon dioxide absorption rate was 0.033 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 9>
An absorbent solution (aqueous solution) was prepared in the same manner as in Example 1 except that 2- (diethylamino) -2-methyl-1-propanol (DEAMP) was dissolved in water so that 40% by mass and piperazine was 5% by mass. Using the same apparatus as in Example 1, the carbon dioxide absorption amount, the carbon dioxide absorption rate, and the coagulability were measured under the same conditions.

  The amount of carbon dioxide absorbed at 40 ° C. per mol of amino compound in the absorbing solution is 0.45 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.05 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.40 mol. The carbon dioxide absorption rate was 0.030 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 10>
Absorbent in the same manner as in Example 1, except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and 1-methylpiperazine (1MPZ) was 5% by mass. (Aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The amount of carbon dioxide absorbed at 40 ° C. per mol of amino compound in the absorbing solution is 0.45 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.08 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.37 mol. The carbon dioxide absorption rate was 0.028 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 11>
Absorbent in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and 2-methylpiperazine (2MPZ) was 5% by mass. (Aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The absorption amount of carbon dioxide at 40 ° C. per 1 mol of amino compound in the absorption liquid is 0.50 mol, and the absorption amount of carbon dioxide in the absorption liquid at 120 ° C. is 0.08 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.42 mol. The carbon dioxide absorption rate was 0.029 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 12>
Except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water to 40% by mass and 2,5-dimethylpiperazine (25DMPZ) to 5% by mass, the same procedure as in Example 1 was performed. An absorption liquid (aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The absorption amount of carbon dioxide at 40 ° C. per mol of amino compound in the absorption liquid is 0.40 mol, and the absorption amount of carbon dioxide of the absorption liquid at 120 ° C. is 0.07 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.33 mol. The carbon dioxide absorption rate was 0.025 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 13>
Except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water at 40% by mass and 2,6-dimethylpiperazine (26DMPZ) was dissolved at 5% by mass in the same manner as in Example 1. An absorption liquid (aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The absorption amount of carbon dioxide at 40 ° C. per 1 mol of amino compound in the absorption liquid is 0.39 mol, and the absorption amount of carbon dioxide of the absorption liquid at 120 ° C. is 0.07 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.32 mol. The carbon dioxide absorption rate was 0.023 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 14>
An absorbent solution (as in Example 1) except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and monoethanolamine (MEA) were 5% by mass. An aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The absorption amount of carbon dioxide at 40 ° C. per 1 mol of amino compound in the absorption liquid is 0.60 mol, and the absorption amount of carbon dioxide in the absorption liquid at 120 ° C. is 0.15 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.45 mol. The carbon dioxide absorption rate was 0.036 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 15>
Absorbed in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and 2-methylaminoethanol (MAE) was 5% by mass. A liquid (aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution is 0.51 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.11 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.40 mol. The carbon dioxide absorption rate was 0.032 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Example 16>
Absorbed in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so that 40% by mass and 2-ethylaminoethanol (EAE) was 5% by mass. A liquid (aqueous solution) was prepared, and using the same apparatus as in Example 1, the carbon dioxide absorption, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

  The amount of carbon dioxide absorbed at 40 ° C. per mol of amino compound in the absorbing solution is 0.46 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.10 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.36 mol. The carbon dioxide absorption rate was 0.029 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

<Comparative Example 1>
An absorbing solution was prepared in the same manner as in Example 1 except that 2-amino-2-methyl-1-propanol was dissolved in water so that 40% by mass and piperazine was 5% by mass. The carbon dioxide absorption amount, the carbon dioxide absorption rate, and the coagulation property were measured under the same conditions.

The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution is 0.55 mol, and the amount of carbon dioxide absorbed in the absorbing solution at 120 ° C. is 0.08 mol per mol of amino compound, which is 40 ° C. The CO ₂ recovery amount with a difference of 120 ° C. was 0.47 mol. The carbon dioxide absorption rate was 0.036 mol / L / min.

  Moreover, although the absorption liquid before carbon dioxide absorption did not coagulate | solidify, the absorption liquid which absorbed carbon dioxide at 40 degreeC coagulated not only in the refrigerator but at room temperature (about 20 degreeC).

<Comparative example 2>
An absorbent solution was prepared in the same manner as in Example 1 except that 2- (dimethylamino) -2-methyl-1-propanol was dissolved in water so as to be 40% by mass. The carbon dioxide absorption, carbon dioxide absorption rate, and coagulability were measured under the same conditions.

The amount of carbon dioxide absorbed at 40 ° C. per mol of amino compound in the absorbing solution is 0.18 mol, and the amount of CO ₂ absorbed in the absorbing solution at 120 ° C. is 0.03 mol per mol of amino compound, which is 40 ° C. The amount of carbon dioxide recovered with a difference of 120 ° C. was 0.15 mol. The carbon dioxide absorption rate was 0.015 mol / L / min.

  Moreover, neither the absorption liquid which absorbed carbon dioxide at 40 degreeC before carbon dioxide absorption nor coagulated.

  In Table 1, about Examples 1-16 and Comparative Examples 1-2, together with the content of the amine compound and the reaction accelerator in the absorption liquid, the carbon dioxide absorption at 40 ° C., the carbon dioxide absorption at 120 ° C., and the carbon dioxide The carbon recovery amount and the measurement result of solidification are shown.

In Table 1, the CO ₂ recovery amount represents not only the absorption amount per 1 mol of amine compound contained in the absorption liquid and the recovery amount in terms of moles, but also the amount of carbon dioxide that can be recovered from 1 L of absorption liquid as NL (normal (Liter).

  As is clear from Table 1, in the absorbing liquids of Examples 1, 2, 4, and 7 to 16, both the carbon dioxide recovery amount and the carbon dioxide absorption rate were large, and the carbon dioxide absorption performance was excellent. Moreover, it did not solidify even after cooling before and after carbon dioxide absorption.

  On the other hand, in the absorption liquid of Comparative Example 1, both the amount of carbon dioxide recovered and the carbon dioxide absorption rate were large, but after carbon dioxide absorption, it solidified even at room temperature without cooling.

  Further, when the concentration of the reaction accelerator was increased as in the absorption liquid of Example 3, both the amount of carbon dioxide recovered and the carbon dioxide absorption rate were large, but solidified when cooled before and after carbon dioxide absorption.

  Further, when the DMAPM concentration was increased as in the absorption liquid of Example 5, both the amount of carbon dioxide recovered and the carbon dioxide absorption rate were large, but solidified when cooled before carbon dioxide absorption.

  Further, when the DMAPM concentration was reduced as in the absorption liquid of Example 6, the carbon dioxide recovery amount was reduced.

  In addition, when the heterocyclic amine compound was not added as in the absorption liquid of Comparative Example 2, both the carbon dioxide recovery amount and the carbon dioxide absorption rate were reduced.

  According to at least one embodiment described above, there is provided an acidic gas absorbent that has a high recovery amount of acidic gas such as carbon dioxide and does not solidify even at low temperatures, and an acidic gas removal device and an acidic gas removal method using the same. Can be provided.

  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 ... Absorber, 3 ... Regenerator, 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 (11)

Acid gas absorption characterized by containing a tertiary alkanolamine represented by the following general formula (1) and a reaction accelerator selected from the group consisting of a primary amine and a secondary amine Agent.

(In the above general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, and R ³ is 1 to 1 carbon atom. 4 represents a hydroxyalkyl group.) The acidic gas absorbent according to claim 1, wherein R ¹ and R ² are a methyl group or an ethyl group. The acidic gas absorbent according to claim 1 or 2, wherein R ⁴ and R ⁵ are a methyl group or an ethyl group.   The tertiary alkanolamine is 2- (dimethylamino) -2-methyl-1-propanol, 2- (ethylmethylamino) -2-methyl-1-propanol, 2- (dimethylamino) -2-ethyl The acidic gas absorbent according to claim 1, which is at least one selected from the group consisting of -1-propanol and 2- (diethylamino) -2-methyl-1-propanol. The acidic gas absorbent according to any one of claims 1 to 4, wherein the reaction accelerator is a heterocyclic amine compound represented by the following general formula (2).

(In the above general formula (2), R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁷ represents an alkyl group having 1 to 4 carbon atoms bonded to a carbon atom forming a heterocycle. P represents an integer of 1 to 3, q represents an integer of 1 to 4, and r represents an integer of 0 to 12. However, when r is 2 to 3, nitrogen atoms are directly bonded to each other. There is no case.)   The acidic gas absorbent according to claim 5, wherein the heterocyclic amine compound has a piperazine ring.   7. The heterocyclic amine compound according to claim 6, wherein the heterocyclic amine compound is at least one selected from the group consisting of piperazine, 1-methylpiperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, and 2,6-dimethylpiperazine. Acid gas absorbent.   The acidic gas absorbent according to any one of claims 1 to 4, wherein the reaction accelerator is at least one selected from the group consisting of monoethanolamine, 2-methylaminoethanol, and 2-ethylaminoethanol. .   The acidic gas according to any one of claims 1 to 8, wherein the content of the tertiary alkanolamine is 20 to 55% by mass and the content of the reaction accelerator is 1 to 10% by mass. Absorbent.   The gas containing acid gas and the acid gas absorbent according to any one of claims 1 to 9 are brought into contact with each other to remove the acid gas from the gas containing the acid gas. Gas removal method. A gas containing an acid gas is brought into contact with the acid gas absorbent according to any one of claims 1 to 9, and the acid gas is contained in the acid gas absorbent by absorbing the acid gas. An absorber to remove acid gas from the gas;
A regenerator that regenerates the acidic gas absorbent by desorbing the acidic gas from the acidic gas absorbent that has absorbed the acidic gas,
An acidic gas removing device, wherein the acidic gas absorbent regenerated by the regenerator is reused by the absorber.

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