JP2017196547A - Acidic gas absorbent, acidic gas removal method and acidic gas removal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acidic gas absorbent having the high absorption amount of an acidic gas and high absorption rate and being prevented with the diffusion of an absorbent component.SOLUTION: An acidic gas absorbent containing an amino acid salt expressed as formula 1 and an amine compound expressed as formula 2 is provided (where, Me is an alkali metal; Rand Rare each independently a 1-4C alkylene chain or direct coupling substituted or unsubstituted by a carboxylate group or a 1-4C alkyl; the sum of carbon in the alkylene chain in Rand Ris 1-4; Rand Rare each independently a 1-4C alkyl substituted or unsubstituted or a hydroalkyl group; at least one of Rand Ris a hydroxyalkyl group; Ris H or a 1-4C alkyl; and Ris a 2-4C hydroxyalkyl).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 CO ₂ is largely due to industrial activities, and the momentum for suppressing emissions to the environment is increasing.

Technology to suppress the increase in the concentration of acid gas including CO ₂ , development of energy saving products, technology to use and sequester acid gas as resources, natural energy and nuclear energy that does not emit acid gas, 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. how to recover by the CO ₂ removal are known further recovered method of storing CO _2. 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 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, triethanolamine, Examples include dimethylamino-1-methylethanol.

When these amines are used alone, the CO ₂ absorption rate is not sufficient, and usually a compound having a reaction promoting effect may be used in combination. However, a cyclic diamine is known as a compound having a reaction promoting effect, but it has a problem that it has a high vapor pressure and is easily dissipated. In addition, the use of an amino acid salt may improve the dispersibility, but as far as the present inventor knows, CO ₂ absorption characteristics cannot be said to be sufficient even when used in combination with the above-described amine.
For this reason, there is a demand for the development of a new absorbing solution that has excellent CO ₂ absorption characteristics and improved dispersibility.

JP 2011-194388 A JP 2012-143760 A Japanese Patent Laid-Open No. 07-246315 JP 2008-136989 A International Publication No. 2013-118819

  The problem to be solved by the present invention is to provide an acid gas absorbent that absorbs a large amount of acid gas and has a low diffusibility, and a method for removing acid gas and an acid gas removal apparatus using the same.

The acidic gas absorbent according to an embodiment of the present invention includes an amino acid salt represented by the following general formula (1) and an amine compound represented by the following general formula (2).

[In the above general formula (1), COOMe represents a carboxylate group, and Me represents an alkali metal. R ¹ and R ² each independently represents an alkylene chain having 0 to 4 carbon atoms, and any one of the carbon atoms is bonded to a carboxylate group or an alkyl group having 1 to 4 carbon atoms. Also good. However, the total carbon number of the alkylene chain of R ¹ and R ² is 1 or more and 4 or less. ]

[In the above general formula (2), R ³ and R ⁴ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group, and at least one of R ³ and R ⁴ Is a hydroxyalkyl group, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydroxyalkyl group having 2 to 4 carbon atoms. ]
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 consists of removing gas.

  And the acidic gas removal apparatus of embodiment of this invention contains the said acidic gas by making the acidic gas and the acidic gas absorbent contact the gas containing acidic gas, and making this acidic gas absorbent absorb acidic gas. An absorber that removes the acid gas from the 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. An acid gas removing device that reuses the regenerated acid gas absorbent in the absorber, wherein the acid gas absorbent according to the above-described embodiment of the present invention is used as the acid gas absorbent. .

  According to the acidic gas absorbent of the embodiment, the absorption amount of acidic gas such as carbon dioxide can be increased, and the dispersibility of the reaction accelerator can be decreased.

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 an embodiment of the present invention includes an amino acid salt represented by the following general formula (1) and an amine compound represented by the following general formula (2).

[In the above general formula (1), COOMe represents a carboxylate group, and Me represents an alkali metal. R ¹ and R ² each independently represents an alkylene chain having 0 to 4 carbon atoms, and any one of the carbon atoms is bonded to a carboxylate group or an alkyl group having 1 to 4 carbon atoms. Also good. However, the total carbon number of the alkylene chain of R ¹ and R ² is 1 or more and 4 or less. ]

[In the above general formula (2), R ³ and R ⁴ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group, and at least one of R ³ and R ⁴ Is a hydroxyalkyl group, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydroxyalkyl group having 2 to 4 carbon atoms. ]
The acidic gas absorbent according to the embodiment of the present invention includes an amino acid salt represented by the general formula (1) and an amine compound represented by the general formula (2), for example, a solvent such as water, and an antioxidant as necessary. After mixing auxiliary materials such as an agent and a pH adjuster, it can be used as an acid gas absorption method and an acid gas absorber of an acid gas absorber.

Furthermore, low reaction heat property can be obtained and the amount of carbon dioxide absorption can be increased. That is, in the amine compound of the general formula (2), a branched alkyl group in which a hydroxyl group is bonded to at least ^one of R ¹ and R ² is bonded to a nitrogen atom.

As described above, the amine compound of the above general formula (2) in which the branched alkyl group is directly bonded to the nitrogen atom has a structure having a large steric hindrance, and therefore, in the reaction with carbon dioxide (CO ₂ ), bicarbonate ions are generated. Produced and the reaction heat is reduced. Furthermore, it is difficult to dissipate due to its low vapor pressure.

<Amino acid salt>
Conventionally, it is known to use an amino acid salt as an absorbing solution. However, there is a need for further improvements in the amount of acid gas absorbed and the dispersibility.
The present inventors have found that an amino acid salt having a specific cyclic structure acts as a reaction accelerator for an absorption liquid mainly composed of amino alcohol.

  Since the specific amino acid salt represented by the general formula (1) has a vapor pressure that is negligibly small compared to a cyclic diamine such as piperazine, it was used as an acid gas absorber for an acid gas absorption method and an acid gas absorption device. In this case, it is possible to suppress the diffusion of the absorbent to the outside of the reaction apparatus.

The amino acid salt represented by the above general formula (1) is different in structure from a normal chain amino acid salt, and has an acidic gas (for example, carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), sulfide) Since it has high reactivity with carbonyl (COS) and is excellent in solubility in water, it is difficult to precipitate during absorption of acidic gas.

Therefore, the acid gas absorbent according to the embodiment of the present invention has a high amount of acid gas absorption, and precipitation during acid gas absorption is suppressed. At the same time, since the diffusibility of the amine that is the absorbent component is suppressed, the amount of amine released into the atmosphere can be significantly reduced. In particular, the cyclic α-amino acid salt of the general formula (1) (that is, when the total number of carbon atoms of the alkylene chain of R ¹ and R ² is 1) is particularly excellent in solubility, and thus precipitates upon absorption of acid gas. Hateful.

  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. The acidic gas absorbent according to the embodiment is particularly suitable for absorbing oxidizing gases such as carbon dioxide and hydrogen sulfide.

In the amino acid salt represented by the general formula (1), R ¹ and R ² are each independently an alkylene chain having 0 to 4 carbon atoms, and the total number of carbon atoms of the alkylene chain of R ¹ and R ² is It satisfies the requirement of 1 or more and 4 or less. Here, the alkylene chain having 0 carbons specifically means that R ¹ (or R ² ) does not exist, and a carbon atom of CH and a nitrogen atom of NH are bonded without any other atoms intervening. It means that For example, when R ¹ is an alkylene chain having 0 carbon atoms as described above, a carbon atom of CH and a nitrogen atom of NH are bonded without any other atoms, and R ² is a methylene group or an ethylene group. , A carbon atom of CH and a nitrogen atom of NH are bonded to each other through either a propylene group or a butylene group to form a ring.

In these alkylene chains R ² (that is, a methylene group, an ethylene group, a propylene group, and a butylene group), a part of hydrogen atoms may be substituted with an alkyl group having 1 to 3 carbon atoms.
From the viewpoint of the reaction promoting effect, it is preferable that the total number of carbon atoms of the alkylene chain R ¹ and the alkylene chain R ² is 3 or less than that of 4 or more.
From the viewpoint of solubility, those having a total of 1 to 3 carbon atoms of R ¹ and R ² are preferred, and those having 3 carbon atoms are particularly preferred.
Me is an alkali metal. Me can be any alkali metal such as lithium, sodium, potassium, rubidium, cesium, etc., but in the embodiments of the present invention, sodium and potassium are particularly preferred in that the molecular weight of the amino acid salt does not become too large.

  In the embodiment of the present invention, preferred examples of the amino acid salt include the following compounds. For example, ethyleneimine-2-carboxylic acid sodium salt, azetidine-2-carboxylic acid sodium salt, azetidine-3-carboxylic acid sodium salt, pyrrolidine-2-carboxylic acid sodium salt, pyrrolidine-3-carboxylic acid sodium salt, piperidine- Examples thereof include 2-carboxylic acid sodium salt, piperidine-3-carboxylic acid sodium salt, piperidine-4-carboxylic acid sodium salt, and potassium salts of these carboxylic acids. One of these compounds can be used alone, or two or more can be used in combination.

Among these, pyrrolidine derivatives and piperidine derivatives are particularly desirable from the viewpoint of improving the carbon dioxide absorption amount and absorption rate of the acidic gas absorbent.
The acidic gas absorbent according to an embodiment of the present invention comprises at least one amino acid salt represented by the above general formula (1).

  The amount of the amino acid salt compound represented by the general formula (1) contained in the acid gas absorbent is preferably 0.1 to 20% by mass, particularly preferably 5 to 15% by mass (acid gas absorbent Of 100% by mass). If the content of the amino acid salt of the general formula (1) contained in the acid gas absorbent is less than 0.1% by mass, the effect of improving the acid gas absorption rate may not be sufficiently obtained. When content of said specific amine acid exceeds 20 mass%, there exists a possibility that the viscosity of an absorber may become high too much and the reactivity may fall on the contrary.

  As described above, the acidic gas absorbent according to the embodiment of the present invention including the amino acid salt compound of the general formula (1) and the amine compound of the general formula (2) (detailed below) is an acidic gas (particularly, dioxide dioxide) per unit mole. Carbon) absorption amount, acid gas absorption amount per unit volume of the acid gas absorbent, and acid gas absorption rate are further improved. And since the energy (desorption energy of acidic gas) which isolate | separates acidic gas is reduced, the energy at the time of regenerating an acidic gas absorbent can be reduced.

<Amine compound>
The acidic gas absorbent according to the embodiment of the present invention includes an amine compound represented by the following general formula (2) as one of essential components.

[In the above general formula (2), R ³ and R ⁴ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group, and at least one of R ³ and R ⁴ Is a hydroxyalkyl group, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydroxyalkyl group having 2 to 4 carbon atoms. ]
In the general formula (2), R ³ and R ⁴ are substituted or unsubstituted, preferably a chain alkyl group having 1 to 4 carbon atoms, and a hydroxyl group is included in at least one of R ³ and R ⁴ . As the substituted or unsubstituted chain alkyl group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, or a butyl group can be preferably used. Particularly preferred is a methyl group or an ethyl group.

The alkyl group having a hydroxyl group of R ³ or R ⁴ is preferably, for example, a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, or a 1-hydroxy group. A butyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group and the like can be mentioned. These chain alkyl groups may contain heteroatoms such as Si, O, N, and S.

By having a hydroxyl group in at least one of R ³ and R ⁴ , the volatility of the amine compound of the general formula (2) is suppressed, so that an acidic gas is used compared to a general chain alkanolamine. The acid gas absorbent is reduced in the amount of amine component released into the atmosphere during the treatment. And, mainly, R ³ and R ⁴ become part of a branched alkyl group having these as branched chains, so that the heat of reaction during the reaction of the amine compound of the general formula (2) with the acidic gas is reduced. Has been.

R ⁵ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (specifically, a methyl group, an ethyl group, a propyl group, or a butyl group).
R ⁶ is a hydroxyalkyl group having 2 to 4 carbon atoms. This improves the reactivity with carbon dioxide. More preferred are a 2-hydroxyethyl group and a 2-hydroxypropyl group.
Since such an amine compound has a structure having a large steric hindrance, a bicarbonate ion exhibiting a low heat of reaction is generated in the reaction with carbon dioxide (CO ₂ ). For this reason, there is little calorie | heat amount generated at the time of reaction with acidic gas, and the absorbed amount of acidic gas is high. And the amine compound which such an alkyl group couple | bonded directly with the nitrogen atom is a thing with very low volatility. For this reason, leakage of the amine compound out of the apparatus is extremely small.

  Preferable specific examples of the amine compound of the general formula (2) include, for example, N- (1-hydroxy-2-propyl) ethanolamine, N- (4-hydroxy-2-butyl) ethanolamine, N- ( 5-hydroxy-2-pentyl) ethanolamine, N- (1-hydroxy-2-butyl) ethanolamine, bis (2-propanol) amine, N- (1-hydroxy-2-propyl) -2-propanolamine, N- (4-hydroxy-2-butyl) -2-propanolamine, N- (5-hydroxy-2-pentyl) -2-propanolamine, N- (1-hydroxy-2-butyl) -2-propanolamine And so on. One of these compounds can be used alone, or two or more can be used in combination.

  The content of the amine compound represented by the general formula (2) contained in the acid gas absorbent is preferably 10 to 60% by mass, particularly preferably 20 to 50% by mass (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 acid gas absorbed and desorbed per unit volume, and the higher the rate of absorption and desorption of carbon dioxide. For this reason, it is advantageous in that carbon dioxide can be efficiently recovered, which is preferable in terms of energy consumption, size of plant equipment, and 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. In addition, if the concentration of the amine component in the absorbing solution is too high, the viscosity of the absorbing solution increases and cannot be ignored.

  When the content of the amine compound represented by the general formula (2) is 60% by mass or less, phenomena such as an increase in the viscosity of the absorbing liquid are not observed. In addition, by setting the content of the specific amine compound to 10% by mass or more, a sufficient amount of carbon dioxide absorbed and absorption rate can be obtained, and excellent processing efficiency can be obtained.

<Other components (optional components)>
An acidic gas absorbent according to an embodiment of the present invention includes an amino acid salt compound represented by the general formula (1) and an amine represented by the general formula (2), for example, a solvent such as water, and the like. Accordingly, after being mixed with various auxiliary materials and the like, it is suitable as an acid gas absorbent for an acid gas absorption method or 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 is preferably 20 to 60% by mass, particularly preferably 30 to 60% by mass (the total amount of the acid gas absorbent is 100% by mass). When the content of water is within this range, it is preferable from the viewpoint of suppressing an increase in the viscosity of the absorbing solution and suppressing foaming when absorbing carbon dioxide.

  Specific examples of preferred antioxidants include, for example, dibutylhydroxytoluene (BHT), butylhydroxyanisole (BHA), sodium erythorbate, sodium nitrite, sulfur dioxide, 2-mercaptoimidazole, 2-mercaptobenzimidazole and the like. Can do. When the antioxidant is used, the content is preferably 0.01 to 1% by mass, particularly preferably 0.1 to 0.5% by mass (the total amount of the acid gas absorbent is 100% by mass). ). The antioxidant can prevent deterioration of the acid gas absorbent and improve durability.

  Preferable specific examples of the antifoaming agent include, for example, a silicone antifoaming agent and an organic antifoaming agent. When using an antifoamer, the content is preferably 0.00001 to 0.001% by mass, particularly preferably 0.0005 to 0.001% 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.

  Preferable specific examples of the anticorrosive include, for example, phosphate esters, tolyltriazoles, and benzotriazoles. When the anticorrosive agent is used, the content thereof is preferably 0.00003 to 0.0008 mass%, particularly preferably 0.00005 to 0.005 mass% (the total amount of the acid gas absorbent is 100 mass%). To do). Such an anticorrosive can prevent the plant equipment from decaying and improve durability.

  Moreover, in the acidic gas absorbent according to the embodiment of the present invention, amino alcohol can be appropriately mixed and used as necessary. By using amino alcohol, it is possible to improve or improve the absorption amount, release amount, absorption rate, etc. of the acidic gas absorbent.

  Suitable amino alcohols include, for example, monoethanolamine, 2-amino-2-methylpropanolamine, 2-amino-2-methyl-1,3-dipropanolamine, methylaminoethanol, 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, diethanolamine and the like. It is. One of these compounds can be used alone, or two or more can be used in combination.

Among these, alkanolamines include 2- (isopropylamino) ethanol, 2-amino-2-methyl-1-, from the viewpoint of further improving the reactivity between the amine compound of the general formula (2) and the acidic gas. It is preferably at least one selected from the group consisting of propanol.
When these amino alcohols are used, the amount used is preferably 1 to 30% by volume with respect to 100% by volume of the amine compound represented by the general formula (2).

As described above, according to the acidic gas absorbent of the present embodiment, the absorption amount of acidic gas such as carbon dioxide can be increased, and the dispersibility of the reaction accelerator can be reduced. And less energy is required to recover the acid gas. Furthermore, since the amine compound which has multiple hydroxyl groups which are polar groups in a molecule | numerator is used and the dispersibility is suppressed, the emission to the exterior of a reactor is suppressed. Therefore, even when a reaction accelerator having a low vapor pressure is used in combination, the acidic gas can be stably treated over a long period of time. And it has high reactivity with respect to acidic gas (for example, carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), carbonyl sulfide (COS), and is excellent in solubility in water. In addition, it is difficult to precipitate when absorbing acid gas.

<Method for removing acid gas>
An acid gas removal method according to an embodiment of the present invention is a method in which an acid gas is removed from a gas containing the acid gas by bringing the gas containing the acid gas into contact with the acid gas absorbent according to the above-described embodiment. .

  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. The method of absorbing acid, the method of dropping the acid gas absorbent into a gas stream containing acid gas (a spray or spray method), or the acid gas in an absorber containing a magnetic or metal mesh filler It can be carried out by a method in which the gas to be contained and the acidic gas absorbent are brought into countercurrent contact.

  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 greater the amount of acid gas absorbed, but the lower limit of the treatment temperature can be determined by the process gas temperature, the heat recovery target, and the like. The pressure at the time of acid gas absorption is usually about atmospheric pressure. 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 in order to suppress energy consumption required for compression.

  The method of separating acid gas from the acid gas absorbent that has absorbed the acid gas and recovering pure or high-concentration carbon dioxide is the same as distillation, in which the acid gas absorbent is heated and bubbled in a kettle and desorbed. And a heating method in which a liquid interface is expanded in a regenerator tower containing a plate tower, a spray tower, or a magnetic or 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 120 ° C. The higher the temperature, the greater the amount of acid gas desorption, but the higher the temperature, the greater the energy required to heat the absorbent, so 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 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 acidic gas absorbent after separating the acidic gas can be sent again to the acidic gas absorption step 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 store the collected acid gas in the basement where technology is currently being developed.

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

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

  In addition, the amine compound according to the above-described embodiment is significantly higher in corrosion prevention than metal materials such as carbon steel as compared with alkanolamines such as 2-aminoethanol that have been conventionally used as an acid gas absorbent. It has sex. 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.

<Acid gas removal device>
The acidic gas removing device according to the embodiment of the present invention is configured to contact the gas containing the acidic gas with the acidic gas absorbent, and absorb the acidic gas in the acidic gas absorbent from the gas containing the acidic gas. An absorber that removes 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 regenerates with the regenerator. An acidic gas removal apparatus that reuses the acidic gas absorbent that has been used in the absorber, wherein the acidic gas absorbent according to the specific embodiment of the present invention described above is used as the acidic gas absorbent. It will be.

FIG. 1 is a schematic view of an acidic gas removal apparatus according to an embodiment.
The acidic gas removing device 1 includes a gas absorber (for example, exhaust gas) containing an acidic gas and an acidic gas absorbent, an absorber 2 that absorbs and removes the acidic gas from the acidic gas, and an acidic gas. A regenerator 3 that separates the acid gas from the acid gas absorbent that has absorbed the gas and regenerates the acid 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 4. The exhaust gas is pushed into the absorber 2 and comes into contact with the acidic gas absorbent supplied from the acidic gas absorbent supply port 5 at the top of 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 acid gas absorbent may be adjusted to at least 9 or more, but the optimum conditions may be appropriately selected 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 after the carbon dioxide is removed is discharged from the gas discharge port 6 to the outside of the absorber 2.

  The acidic gas absorbent that has absorbed carbon dioxide is fed to the heat exchanger 7 and the heater 8, heated, and then fed to the regenerator 3. The acidic gas absorbent sent into the regenerator 3 moves from the upper part to the lower part of the regenerator 3, and during this time, the acidic gas 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 7 and the absorption liquid cooler 10 by the pump 9 and returned to the absorber 2 from the acid gas absorbent supply port 5.
On the other hand, the acidic gas separated from the acidic gas absorbent comes into contact with the reflux water supplied from the reflux drum 11 at the top of the regenerator 3 and is discharged to the outside of the regenerator 3.
The reflux water in which carbon dioxide is dissolved is cooled by the reflux cooler 12 and then separated from the liquid component in which the water vapor accompanied with carbon dioxide is condensed in the reflux drum 11. This liquid component is guided to the acid gas recovery step by the recovery acid gas line 13. On the other hand, the reflux water from which the acid gas has been separated is sent to the regenerator 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 acidic gas by using an acidic gas absorbent excellent in acidic gas absorption characteristics and desorption characteristics.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples and comparative examples.
<Example 1>
N- (1-hydroxy-2-propyl) ethanolamine is dissolved in water to 45% by mass and pyrrolidine-2-carboxylic acid sodium salt to 5% by mass, and 50 ml of an 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 400 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.

  The heat of reaction was measured as follows. The reaction heat of carbon dioxide absorption by the absorption liquid is measured using a differential thermal reaction calorimeter “DRC Evolution” (product name, manufactured by SETARAM) consisting of a glass reaction tank of the same shape and a reference tank installed in a thermostat. It was measured.

  Each of the reaction tank and the reference tank is filled with 140 mL of absorbing solution, and constant temperature water at 40 ° C. is circulated through the jacket 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 dispersibility of the absorbing solution was evaluated as follows. That is, after the absorbent was put into a flask with a cooling tube, the flask was heated in an oil bath to reflux the absorbent. During this time, nitrogen gas was passed through the absorbing solution at a rate of 100 ml / min. Then, the test was stopped when 100 ml of the liquid cooled and recovered by the cooling pipe was obtained, and the amount of amine contained in 100 ml of the recovered liquid was measured (dissipative test).

The amount of carbon dioxide absorbed by the absorbing solution at 40 ° C. was 0.53 mol per mol of amine compound in the absorbing solution, and the reaction heat was 77 kJ / mol-CO ₂ . The dispersibility was 0.1% by weight or less.

<Example 2>
An absorbent solution was prepared in the same manner as in Example 1 except that piperidine-2-carboxylic acid sodium salt was used instead of pyrrolidine-2-carboxylic acid sodium salt, and the same apparatus as in Example 1 was used. Under the conditions, the carbon dioxide absorption amount, the carbon dioxide absorption rate, the heat of reaction, and the recovery amount of the amine compound were measured.
The amount of carbon dioxide absorbed at 40 ° C. was 0.52 mol and the heat of reaction was 76 kJ / mol-CO ₂ per mol of amine compound in the absorbing solution. The dispersibility was 0.1% by weight or less.

<Example 3>
An absorbent solution was prepared in the same manner as in Example 1 except that bis (2-propanol) amine was used instead of N- (1-hydroxy-2-propyl) ethanolamine. The carbon dioxide absorption amount, the carbon dioxide absorption rate, the reaction heat, and the recovery amount of the amine compound were measured under the same conditions.
The amount of carbon dioxide absorbed at 40 ° C. was 0.53 mol and the heat of reaction was 76 kJ / mol-CO ₂ per mol of amine compound in the absorbing solution. The dispersibility was 0.1% by weight or less.

<Example 4>
An absorbent solution was prepared in the same manner as in Example 3 except that piperidine-2-carboxylic acid sodium salt was used instead of pyrrolidine-2-carboxylic acid sodium salt, and the same apparatus as in Example 1 was used. Under the conditions, the carbon dioxide absorption amount, the carbon dioxide absorption rate, the heat of reaction, and the recovery amount of the amine compound were measured.
The amount of carbon dioxide absorbed at 40 ° C. was 0.52 mol and the heat of reaction was 76 kJ / mol-CO ₂ per mol of amine compound in the absorbing solution. The dispersibility was 0.1% by weight or less.

<Example 5>
Using the same apparatus as in Example 1 except that 1% by weight of piperazine was added to the absorption liquid in Example 1, the carbon dioxide absorption amount, the carbon dioxide absorption rate, the reaction heat, and the recovery amount of the amine compound were measured under the same conditions. did.
The amount of carbon dioxide absorbed at 40 ° C. was 0.56 mol and the heat of reaction was 78 kJ / mol-CO ₂ per mol of amine compound in the collected liquid. The dispersibility was 0.1% by weight.

<Comparative Example 1>
N-butylethanolamine was dissolved in water at 45 mass% and piperazine at 5 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 amount, the carbon dioxide absorption rate, the reaction heat, and the recovery amount of the amine compound were measured under the same conditions as in Example 1.
The amount of carbon dioxide absorbed at 40 ° C. was 0.35 mol and the heat of reaction was 75 kJ / mol-CO ₂ per mol of amine compound in the absorbing solution. The dispersibility was 0.9% by weight.

Table 1 shows the measurement results of the amount of carbon dioxide absorbed at 40 ° C., the heat of reaction, and the recovery amount of the amine compound in the emission test for Examples 1 to 5 and Comparative Example 1.

  As is clear from Table 1, in the absorbing liquids of Examples 1 to 5 using the cyclic amino acid salt according to the embodiment of the present invention, the carbon dioxide absorption amount is high, the reaction heat at the time of carbon dioxide absorption is low, Excellent carbon absorption performance. On the other hand, in the case of the absorption liquid of the comparative example using an amine compound having an alkyl group having a small steric hindrance, the amount of carbon dioxide absorbed was small although the reaction heat was relatively small.

  In addition, in the absorbing liquids of Examples 1 to 5 using the amino acid salt according to the embodiment of the present invention, almost no amine compound released from the absorbing liquid was confirmed in the dispersibility test. On the other hand, in Comparative Example 1 using piperazine, about 0.5% by mass of the amine compound was recovered in the radiation test.

  According to the acidic gas absorbent, the acidic gas removal method, and the acidic gas removal device of at least one embodiment described above, the amount of absorption of acidic gas such as carbon dioxide can be increased, and the dispersibility of the reaction accelerator is increased. Can be reduced.

  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 acid gas carbon line, 14 ... Reflux water pump

Claims (7)

An acidic gas absorbent comprising an amino acid salt represented by the following general formula (1) and an amine compound represented by the following general formula (2).

[In the above general formula (1), COOMe represents a carboxylate group, and Me represents an alkali metal. R ¹ and R ² each independently represents an alkylene chain having 0 to 4 carbon atoms, and any one of the carbon atoms is bonded to a carboxylate group or an alkyl group having 1 to 4 carbon atoms. Also good. However, the total carbon number of the alkylene chain of R ¹ and R ² is 1 or more and 4 or less. ]

[In the above general formula (2), R ³ and R ⁴ are each independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group, and at least one of R ³ and R ⁴ Is a hydroxyalkyl group, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydroxyalkyl group having 2 to 4 carbon atoms. ] The acidic gas absorbent according to claim 1, wherein in the general formula (1), R ¹ and R ² are methylene groups.   The acidic gas absorbent according to claim 1 or 2, wherein the amine compound of the general formula (2) is N- (1-hydroxy-2-propyl) ethanolamine.   The acidic gas absorbent according to any one of claims 1 to 3, wherein the amine compound of the general formula (2) is bis (2-propanol) amine.   The content of the amino acid salt of the general formula (1) is 0.1 to 20% by mass, and the content of the amine compound of the general formula (2) is 10 to 60% by mass. The acidic gas absorbent according to Item 1.   A gas containing acid gas is brought into contact with the acid gas absorbent according to any one of claims 1 to 5, and the acid gas is removed from the gas containing the acid gas. Removal method. An absorber that removes the acid gas from the gas containing the acid gas by contacting the gas containing the acid gas with the acid gas absorbent and absorbing the acid gas in the acid gas absorbent;
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 acid gas removing device that reuses the acid gas absorbent regenerated by the regenerator in the absorber,
The acidic gas removal apparatus which uses the acidic gas absorbent of any one of Claims 1-5 as said acidic gas absorbent.

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