JP2018122278A - 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 with a large amount of recovery of acidic gas such as carbon dioxide, and an acidic gas removal device and an acidic gas removal method using the same.SOLUTION: An acidic gas absorbent according to an embodiment contains compounds of the following formula (1) and formula (2) and a cyclic amine compound. NRRR(1) [Rrepresents a C3-8 cyclic alkyl group, optionally substituted with a C1-4 alkyl group. Ris a hydrogen atom, a C1-4 alkyl group or a C2-6 hydroxyalkyl group. Ris a C2-6 hydroxyalkyl group]. RRN(CH)NRR(2) [R, R, Rand Reach represent a methyl group or an ethyl group. m is an integer of 2-8].SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an acidic gas absorbent, and an acidic gas removing device and an acidic gas removing method using the same.

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

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

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

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

  In general, alkanolamines typified by monoethanolamine (MEA) have been developed since the 1930s as chemical absorbents used in the absorption method and are still used (see, for example, Patent Document 1). This method is economical, and the removal device can be easily increased in size.

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

  However, MEA is corrosive, easily deteriorates, and has a problem of high energy required for regeneration, and therefore, development of a new absorbent is required.

  In recent years, researches on alkanolamines having structurally steric hindrance, among amine compounds, have been actively attempted as acid gas absorbents (see, for example, Patent Document 2). 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.

  On the other hand, as an amine compound having a structure different from that of alkanolamines, a method of using a cyclic amine as an absorbent or as a reaction accelerator in combination with an amino alcohol is known, but the vapor pressure is higher than that of an amino alcohol. Since it is high, it is easy to dissipate from the absorption tower (see Patent Document 1 and Patent Document 3).

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

  However, even with these techniques, the acid gas absorption capacity such as the acid gas absorption amount and the acid gas recovery amount is still insufficient, and further improvement of the gas absorption capacity is demanded.

  The problem to be solved by the present invention is to provide an acidic gas absorbent that has a high recovery amount of acidic gas such as carbon dioxide and has low diffusibility, and an acidic gas removing device and an acidic gas removing method using the same. .

〔上記式（１）中、Ｒ^１は、炭素数１〜４のアルキル基で置換されているか置換されていない、炭素数３〜８の環状アルキル基を表す。Ｒ^２は、水素原子、炭素数１〜４のアルキル基または炭素数２〜６のヒドロキシアルキル基を表す。Ｒ^３は、炭素数が２〜６のヒドロキシアルキル基を表す。〕

〔上記式（２）中、Ｒ^４、Ｒ^５、Ｒ^６およびＲ^７は、それぞれ独立して、メチル基あるいはエチル基を表す。ｍは、２〜８の整数を表す。〕
実施形態の酸性ガス除去方法は、酸性ガスを含有するガスと、上記した実施形態に係る酸性ガス吸収剤とを接触させて、前記酸性ガスを含むガスから酸性ガスを除去するものである。 The acidic gas absorbent according to the embodiment includes an amine compound represented by the following general formula (1), a diamine compound represented by the following general formula (2), and a cyclic amine compound.

[In formula (1), R ¹ is unsubstituted or substituted with an alkyl group having 1 to 4 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms. R ² represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxyalkyl group having 2 to 6 carbon atoms. R ³ represents a hydroxyalkyl group having 2 to 6 carbon atoms. ]

[In the above formula (2), R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents a methyl group or an ethyl group. m represents an integer of 2 to 8. ]
The acidic gas removal method of the embodiment is configured to remove the acidic gas from the gas containing the acidic gas by bringing the gas containing the acidic gas into contact with the acidic gas absorbent according to the above-described embodiment.

The acidic gas removal device of the embodiment includes the above acidic gas absorbent, an absorption tower that removes the acidic gas from the gas by bringing the gas containing the acidic gas into contact with the acidic gas absorbent,
A regeneration tower that regenerates the acid gas absorbent by removing the acid gas from the acid gas absorbent that has absorbed the acid gas, and regenerates the acid gas absorbent regenerated in the regeneration tower in the absorption tower. It is characterized by being comprised so that it may utilize.

  According to the present invention of the embodiment, an acid gas absorbent having improved acid gas absorption amount, acid gas recovery amount and the like is obtained.

  And this acidic gas absorbent requires little energy when isolate | separating acidic gas. Therefore, according to this invention of embodiment, the method and apparatus which can remove acidic gas efficiently with low energy are provided.

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

〔上記式（１）中、Ｒ^１は、炭素数１〜４のアルキル基で置換されているか置換されていない、炭素数３〜８の環状アルキル基を表す。Ｒ^２は、水素原子、炭素数１〜４のアルキル基または炭素数２〜６のヒドロキシアルキル基を表す。Ｒ^３は、炭素数が２〜６のヒドロキシアルキル基を表す。〕

〔上記式（２）中、Ｒ^４、Ｒ^５、Ｒ^６およびＲ^７は、それぞれ独立して、メチル基あるいはエチル基を表す。ｍは、２〜８の整数を表す。〕
従来より、アミン化合物が立体障害を有すると、二酸化炭素吸収反応に大きく影響し、反応熱の低い重炭酸イオン生成反応が優勢となることが知られている。例えば、分岐構造を有するＮ−イソプロピルアミノエタノールは、二酸化炭素の吸収反応において反応熱の生成が少ないことが報告されている。 Hereinafter, embodiments will be described in detail.
<Acid gas absorbent>
The acidic gas absorbent according to the embodiment includes an amine compound represented by the following general formula (1)), a diamine compound represented by the following general formula (2), and a cyclic amine compound. .

[In formula (1), R ¹ is unsubstituted or substituted with an alkyl group having 1 to 4 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms. R ² represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxyalkyl group having 2 to 6 carbon atoms. R ³ represents a hydroxyalkyl group having 2 to 6 carbon atoms. ]

[In the above formula (2), R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents a methyl group or an ethyl group. m represents an integer of 2 to 8. ]
Conventionally, it is known that when an amine compound has steric hindrance, a carbon dioxide absorption reaction is greatly affected, and a bicarbonate ion generation reaction having a low heat of reaction becomes dominant. For example, it has been reported that N-isopropylaminoethanol having a branched structure generates little reaction heat in the carbon dioxide absorption reaction.

  Based on such findings, the present inventors have studied to further increase the effect of steric hindrance. As a result, the compound represented by the general formula (1) (for example, N-cyclopentylaminoethanol) has a conventional branched structure. It has been found that lower reaction thermal properties can be obtained than amino compounds.

Thus, since the amine compound of the above general formula (1) in which the cyclic alkyl group is directly bonded to the nitrogen atom has a structure having a large steric hindrance, a bicarbonate ion is generated in the reaction with carbon dioxide (CO ₂ ). The reaction heat is considered to be reduced.

  By dissolving the amine compound represented by the general formula (1) in a solvent such as water, an acidic gas absorbent having a high acidic gas absorbing 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 said formula (1), R < ¹ > is a C3-C8 cyclic alkyl group, and some of the hydrogen atoms may be substituted by the C1-C4 alkyl group. Examples of the cyclic alkyl group having 3 to 8 carbon atoms include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. These hydrocarbon groups include Si, O, N, S Or a hetero atom such as C1-C4 alkyl group. The cyclic alkyl group having 3 to 8 carbon atoms is more preferably a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group. Among the above cyclic structures, a cyclopentyl group and a cyclohexyl group are more preferable from the viewpoint of solubility.

R ² represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxyalkyl group having 2 to 6 carbon atoms. R ³ represents a hydroxyalkyl group having 2 to 6 carbon atoms.

R ² is a hydrogen atom, a methyl group or an ethyl group. R ² is more preferably a hydrogen atom or a methyl group. Particularly preferred is a hydrogen atom.

R ³ is a hydroxyalkyl group. From the viewpoint of improving the reactivity with carbon dioxide, a hydroxyalkyl group having 2 to 4 carbon atoms is preferred. The hydroxyalkyl group for R ³ is, for example, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 2-hydroxypropyl group, a 4-hydroxybutyl group, a 3-hydroxybutyl group, or a 2-hydroxybutyl group. Particularly preferred are 2-hydroxyethyl group, 2-hydroxypropyl group and 3-hydroxybutyl group.

  The amine compound of formula (1) is preferably, for example, 2- (cyclobutylamino) ethanol, 2- (cyclopentylamino) ethanol, 2- (cyclohexylamino) ethanol, 2- (cycloheptylamino) ethanol, 2 -(Cyclooctylamino) ethanol, 1- (cyclobutylamino) -2-propanol, 1- (cyclopentylamino) -2-propanol, 1- (cyclohexylamino) -2-propanol, 1- (cycloheptylamino)- 2-propanol, 1- (cyclooctylamino) -2-propanol, 4- (cyclobutylamino) -2-butanol, 4- (cyclopentylamino) -2-butanol, 4- (cyclohexylamino) -2-butanol, 4- (Cycloheptylamino) -2-butanol , 4 (cyclooctyl) -2-butanol.

  As the amine compound (1), one type of compound selected from the above group can be used, or a mixture of two or more types of compounds selected from the above group can be used. is there.

  The content of the amine compound (1) contained in the acidic gas absorbent is preferably 10 to 55% by mass.

  In general, the higher the concentration of the amine component, the greater the amount of carbon dioxide absorbed and desorbed per unit volume, and the higher the carbon dioxide absorption rate and desorption rate. In terms of processing efficiency, it is preferable.

  However, when the concentration of the amine component is too high, an increase in the viscosity of the absorbing solution may occur. Such a tendency is not observed when the content of the amine compound (1) is 55% by mass or less. In addition, by setting the content of the amine compound (1) 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.

  When the acid gas absorbent having an amine compound (1) content in the range of 10 to 55% by mass is used for carbon dioxide recovery, it not only has a high carbon dioxide absorption and carbon dioxide absorption rate, but also carbon dioxide. Since the desorption amount and the carbon dioxide desorption rate are also high, it is advantageous in that carbon dioxide can be efficiently recovered. The content of the amine compound (1) is more preferably 20 to 50% by mass.

上記式（２）中、ｍは２〜８の整数である。Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７は、メチル基あるいはエチル基を表し、同一であっても異なっていてもよい。より好ましくはメチル基である。 The diamine compound (2) acts as an absorption improver, and an aqueous solution obtained by mixing with the amine compound (1) can be used as the acidic gas absorbent.

In said formula (2), m is an integer of 2-8. R ⁴ , R ⁵ , R ⁶ and R ⁷ represent a methyl group or an ethyl group, and may be the same or different. More preferably, it is a methyl group.

  By mixing and using the amine compound (1) with the diamine compound (2), the amount of carbon dioxide absorbed per unit mole, the amount of carbon dioxide absorbed per unit volume of the acidic gas absorbent, and the amount of carbon dioxide recovered can be further increased. This can be further improved. Further, when the amine compound (1) is mixed with the diamine compound (2) and used, the energy (acid gas desorption energy) for separating the acid gas after carbon dioxide absorption is reduced, and the acid gas absorbent is regenerated. Energy can be reduced.

  The diamine compound represented by the general formula (2) is preferably N, N, N ′, N′-tetramethyl-1,4-butanediamine, N, N, N ′, N′-tetramethyl, for example. -1,5-pentanediamine, N, N, N ′, N′-tetramethyl-1,6-hexanediamine, N, N, N ′, N′-tetramethyl-1,8-octanediamine, N, N, N ′, N′-tetraethyl-1,4-butanediamine, N, N, N ′, N′-tetraethyl-1,5-pentanediamine, N, N, N ′, N′-tetraethyl-1, Examples include 6-hexanediamine, N, N, N ′, N′-tetraethyl-1,8-octanediamine, and the like.

  The diamine compound can be used as an absorption enhancer, but it has a lower vapor pressure than a commonly used absorption enhancer (a cyclic amino compound typified by piperazine), so that volatility is suppressed. For this reason, in the process which processes exhaust gas, it can be set as the acidic gas removal agent by which the quantity of the amine component discharge | released in air | atmosphere was reduced. Moreover, since the usage-amount of an amine compound can be suppressed by using together with a diamine compound and an amino compound, it becomes an absorption liquid by which emission was suppressed.

  Among these, as the diamine compound, N, N, N ′, N′-tetramethyl-1,6-hexanediamine (TMHA), N, N, N is used from the viewpoint of further improving the reactivity with acidic gas. It is preferably at least one selected from the group consisting of ', N'-tetramethyl-1,4-butanediamine (TMBA).

  It is preferable that content of the diamine compound (2) contained in an acidic gas absorbent is 1-50 mass%. If the content of the absorption improver contained in the acid gas absorbent is less than 1% by mass, the effect of improving the carbon dioxide absorption and recovery may not be sufficiently obtained. If the content of the absorption improver contained in the acidic gas absorbent exceeds 50% by mass, the viscosity of the absorbent becomes excessively high, and the reactivity may be lowered. The content of the diamine compound (2) is more preferably 1 to 40% by mass.

The acidic gas absorbent comprising the amine compound (1) and the diamine compound (2) can be used by mixing with a heterocyclic amine compound represented by the following general formula (3).

In [the formula (3), ^{R 8} represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. p represents an integer of 1 or 2. ]
The compound of the above formula (3) has a heterocycle comprising 1 or 2 nitrogen atoms and 4 to 8 carbon atoms. Here, when the heterocycle contains two nitrogen atoms, these nitrogen atoms are bonded via an alkylene group having 2 or more carbon atoms. And the hydrogen atom, the C1-C8 alkyl group or hydroxyalkyl group, the aminoalkyl group, the ester group, and the alkoxycarbonyl group may couple | bond with the carbon atom which has formed the heterocyclic ring, respectively. In addition to the nitrogen and carbon atoms described above, the heterocycle can contain an oxygen atom in the ring.

  In the present embodiment, preferably, an absorption improver composed of, for example, an amine compound (1), a diamine compound (2), and a cyclic amine compound (3) is mixed, and the mixture is converted into, for example, an aqueous solution. It can be used as an absorbent.

  By using the absorbent comprising the amine compound (1) and the diamine compound (2) mixed with the cyclic amine compound (3), the amount of carbon dioxide absorbed per unit mole and the amount of carbon dioxide absorbed per unit volume of the acidic gas absorbent The amount of carbon absorption and the amount of carbon dioxide recovered can be further improved. Further, by using a mixture of an amine compound (1) and a diamine compound (2) with a cyclic amine compound, preferably a cyclic amine compound represented by the general formula (3), an acidic gas after carbon dioxide absorption. The energy for separating the gas (acid gas desorption energy) is also reduced, and the energy for regenerating the acid gas absorbent can be reduced.

Among the cyclic amine compounds represented by the general formula (3), azetidine, 1-methylazetidine, 1-ethylazetidine, 2-methylazetidine, 2-azetidylmethanol, 2- (2-aminoethyl) azetidine Pyrrolidine, 1-methylpyrrolidine, 2-methylpyrrolidine, 2-butylpyrrolidine, 2-pyrrolidylmethanol, 2- (2-aminoethyl) pyrrolidine, piperidine, 1-methylpiperidine, 2-ethylpiperidine, 3-propylpiperidine 4-ethylpiperidine, 2-piperidylmethanol, 3-piperidylethanol, 2- (2-aminoethyl) pyrrolidine, hexahydro-1H-azepine, piperazine, piperazine derivatives and the like are particularly preferable.
Among these, piperazine derivatives are particularly desirable from the viewpoint of improving the carbon dioxide absorption amount and absorption rate of the acidic gas absorbent.

A piperazine derivative is a secondary amine compound, and generally, a nitrogen atom of a secondary amino group is bonded to carbon dioxide to form a carbamate ion, thereby contributing to an improvement in the absorption rate in the initial stage of the reaction. Further, the nitrogen atom of the secondary amino group plays a role of converting carbon dioxide bonded thereto to bicarbonate ion (HCO ₃ ⁻ ), and contributes to the speed improvement in the latter half of the reaction.

  The piperazine derivative is more preferably at least one of 2-methylpiperazine, 2,5-dimethylpiperazine, and 2,6-dimethylpiperazine. Hexamethylenetetramine can also be used in the same manner as the cyclic amine compound of the formula (3).

  The content of the absorption improver (cyclic amine compound (3)) contained in the acidic gas absorbent is preferably 1 to 20% by mass. If the content of the absorption improver 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 absorption improver contained in the acidic gas absorbent exceeds 20% by mass, the viscosity of the absorbent becomes excessively high, and the reactivity may be lowered. The content of the absorption improver cyclic amine compound (3)) is more preferably 1 to 15% by mass.

  Moreover, as an acidic gas absorbent which concerns on embodiment, the following alkanolamine can also be used.

  Examples of the alkanolamine include 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- And propylaminoethanol, n-butylaminoethanol, 2- (isopropylamino) ethanol, 3-ethylaminopropanol, triethanolamine, diethanolamine and the like. .

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

  In addition to the above amine compounds and absorption amount improvers, the acid gas absorbents include anticorrosives such as phosphoric acid to prevent corrosion of plant equipment, and antifoaming agents such as silicone to prevent foaming. Alternatively, it may contain an antioxidant or the like for preventing deterioration of the acid gas absorbent.

<Acid gas removal method>
The acid gas removal method according to the present embodiment is an exhaust gas containing an acid gas by bringing an exhaust gas containing the acid gas into contact with an acid gas absorbent obtained by dissolving the amine compound described in the above embodiment in a solvent. The acid gas is absorbed and separated from the gas and removed.

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

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

  The temperature of the acidic gas absorbent when the gas containing carbon dioxide is absorbed in the aqueous solution is usually from room temperature to 60 ° C. or less. Preferably it is 50 degrees C or less, More preferably, it is performed at 20-45 degreeC grade.

  As the temperature is lowered, the amount of acid gas absorbed increases, but the lower limit of the processing temperature is determined by the gas temperature in the process, the heat recovery target, and the like. The pressure during carbon dioxide absorption is usually about atmospheric pressure. 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 carbon dioxide from the acid gas absorbent that has absorbed carbon dioxide 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, carbon dioxide is liberated and released from the carbamate anion and bicarbonate ion.

  The acidic gas absorbent temperature at the time of carbon dioxide 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 absorption, but the higher the temperature, the greater the energy required to heat the absorbent, so the temperature is determined by the process gas temperature, heat recovery target, etc. The pressure during carbon dioxide desorption is usually about atmospheric pressure. Although the pressure can be reduced to a lower pressure in order to enhance the desorption performance, it is preferably performed under atmospheric pressure in order to suppress energy consumption required for the pressure reduction.

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

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

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

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

<Acid gas removal device>
The acidic gas removal device according to the present embodiment includes the acidic gas absorbent, and an absorption tower that removes the acidic gas from the gas by bringing the acidic gas absorbent into contact with the acidic gas absorbent. A regenerating tower that regenerates the acidic gas absorbent by removing the acidic gas from the acidic gas absorbent that has absorbed the acidic gas, and the regenerating tower regenerates the acidic gas absorbent regenerated by the regenerating tower. It is configured to be reused.

FIG. 1 is a schematic view of an acidic gas removal apparatus according to an embodiment.
The acidic gas removing device 1 includes an absorption tower 2 for contacting a gas containing an acidic gas (hereinafter referred to as exhaust gas) with an acidic gas absorbent and absorbing and removing the acidic gas from the exhaust gas, and an acidic gas. A regenerating tower 3 for separating the acid gas from the acid gas absorbent that has absorbed the gas and regenerating 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, is guided to the lower part of the absorption tower 2 through a gas supply port 4. This exhaust gas is pushed into the absorption tower 2 and comes into contact with the acidic gas absorbent supplied from the acidic gas absorbent supply port 5 at the top of the absorption tower 2. As the acidic gas absorbent, the acidic gas absorbent according to the above-described embodiment is used.

  The pH value of the acid gas absorbent is preferably 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 outlet 6 to the outside of the absorption tower 2.

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

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

  On the other hand, the carbon dioxide separated from the acidic gas absorbent comes into contact with the reflux water supplied from the reflux drum 11 at the top of the regeneration tower 3 and is discharged to the outside of the regeneration tower 3.

  The reflux water in which the carbon dioxide is dissolved is cooled by the reflux cooler 12 and then separated from the liquid component in which the water vapor accompanying the carbon dioxide is condensed in the reflux drum 11. Guided to carbon capture process. On the other hand, the reflux water from which carbon dioxide has been separated is sent to the regeneration tower 3 by the reflux water pump 14.

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

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

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

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

<Example 1>
2- (cyclopentylamino) ethanol in 40% by mass, N, N, N ′, N′-tetramethyl-1,6-hexanediamine (TMHA) in 7% by mass, and piperazine in 3% by weight in water. It was made to melt | dissolve and it was set as 50 ml aqueous solution (henceforth an absorption liquid). The absorption liquid is filled in a test tube and heated to 40 ° C., and a mixed gas containing 10% by volume of carbon dioxide (CO ₂ ) and 90% by volume of nitrogen (N ₂ ) gas is vented at a flow rate of 500 mL / min. The carbon dioxide (CO ₂ ) concentration in the gas at the outlet was measured using an infrared gas concentration measuring apparatus (manufactured by Shimadzu Corporation, trade name “CGT-700”) to evaluate the absorption performance.
Further, the aqueous solution after absorbing the mixed gas at 40 ° C. as described above is heated to 70 ° C., and the same gas is passed through, and the CO ₂ concentration in the absorbing solution is measured using an infrared gas concentration measuring device. The release performance was evaluated. In addition, the dissipative property measured the amount of amine released when the absorbing solution was heated to reflux at 100 ° C.
The amount of carbon dioxide absorbed by the absorbing solution at 40 ° C. was 0.62 mol per mol of amino compound in the absorbing solution. The release of carbon dioxide (CO ₂ ) in the absorbing solution at 70 ° C. was 0.34 mol per 1 mol of amino compound. The emitted amount was 0.4%.

<Example 2>
An absorbing solution (aqueous solution) was prepared in the same manner as in Example 1 except that 2- (cyclohexylamino) ethanol was used instead of 2- (cyclopentylamino) ethanol, and the same apparatus as in Example 1 was used. The carbon dioxide absorption and carbon dioxide absorption rate 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 was 0.60 mol, and the amount of carbon dioxide (CO ₂ ) released from the absorbing solution at 70 ° C. was 0.34 mol per mol of amino compound. It was. The emitted amount was 0.4%.

<Example 3>
Instead of N, N, N ′, N′-tetramethyl-1,6-hexanediamine (TMHA), N, N, N ′, N′-tetramethyl-1,4-butanediamine (TMBA) is used. Except that, the absorption liquid was prepared in the same manner as in Example 1, and the carbon dioxide absorption amount and the carbon dioxide absorption rate were measured under the same conditions using the same apparatus as in Example 1.
The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution was 0.64 mol, and the release of carbon dioxide (CO ₂ ) in the absorbing solution at 70 ° C. was 0.32 mol per mol of amino compound. It was. The emitted amount was 0.3%.

<Comparative Example 1>
An absorption liquid (aqueous solution) was prepared in the same manner as in Example 1 except that isopropylaminoethanol was used instead of 2- (cyclopentylamino) ethanol, and the same conditions were used under the same conditions as in Example 1. The carbon dioxide absorption and the carbon dioxide absorption rate were measured by The amount of carbon dioxide absorbed at 40 ° C. per 1 mol of amino compound in the absorbing solution was 0.64 mol, and the release of carbon dioxide (CO ₂ ) in the absorbing solution at 70 ° C. was 0.31 mol per mol of amino compound. It was. The emitted amount was 1.6%.

<Comparative example 2>
An absorbent (aqueous solution) was prepared in the same manner as in Example 1 except that N-methyldiethanolamine was used instead of N, N, N ′, N′-tetramethyl-1,6-hexanediamine (TMHA). The amount of carbon dioxide absorbed and the carbon dioxide absorption rate were measured using the same apparatus as in Example 1 under the same conditions.
The amount of carbon dioxide absorbed at 40 ° C. per mol of amino compound in the absorbing solution was 0.54 mol, and the amount of carbon dioxide (CO ₂ ) released from the absorbing solution at 70 ° C. was 0.29 mol per mol of amino compound. It was. The emitted amount was 1.0%.

  Is the amount of carbon dioxide absorption at 40 ° C. of Examples 1 to 3 containing an amino alcohol having a cyclic alkyl group comparable to that of Comparative Example 1 of amino alcohol containing an isopropyl group that is a branched alkyl group? Although it was a little, the recovered amount at 70 ° C. was large and excellent. In addition, the diffusibility was less and superior in the Examples.

  The carbon dioxide absorption amount at 40 ° C. of Examples 1 to 3 containing a diamine is that the absorption amount at 40 ° C. and the recovery amount at 70 ° C. are both compared to Comparative Example 2 containing methyldiethanolamine, which is a diol type tertiary amine. Many were excellent.

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

Claims (11)

An acidic gas absorbent comprising an amine compound represented by the following general formula (1), a diamine compound represented by the following general formula (2), and a cyclic amine compound.

[In formula (1), R ¹ is unsubstituted or substituted with an alkyl group having 1 to 4 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms. R ² represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxyalkyl group having 2 to 6 carbon atoms. R ³ represents a hydroxyalkyl group having 2 to 6 carbon atoms. ]

[In said formula (2), R < ⁴ >, R < ⁵ >, R < ⁶ > and R < ⁷ > represent a methyl group or an ethyl group each independently. m represents an integer of 2 to 8. ] 2. The acidic gas absorbent according to claim 1, wherein in the amine compound represented by the general formula (1), R ¹ is a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group. The acidic gas absorbent according to claim 1 or 2, wherein in the amine compound represented by the general formula (1), R ² is a hydrogen atom, a methyl group or an ethyl group. In the amine compound represented by the general formula (1), R ³ represents 2-hydroxyethyl group, 3-hydroxypropyl group, 2-hydroxypropyl group, 4-hydroxybutyl group, 3-hydroxybutyl group, or 2-hydroxy. The acidic gas absorbent according to any one of claims 1 to 3, which is a butyl group.   The acidic gas absorbent according to any one of claims 1 to 4, wherein the content of the amine compound represented by the general formula (1) is 10 to 55 mass%.   The diamine compound represented by the following general formula (2) is N, N, N ′, N′-tetramethyl-1,6-hexanediamine or N, N, N ′, N′-tetramethyl-1,4. The acidic gas absorbent according to any one of claims 1 to 5, which is -butanediamine.   The acidic gas absorbent according to any one of claims 1 to 6, wherein the content of the diamine compound (2) is 1 to 50% by mass. The acidic amine absorbent according to any one of claims 1 to 7, wherein the cyclic amine compound is a heterocyclic amine compound represented by the following general formula (3).

In [the formula (3), ^{R 8} represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. p represents an integer of 1 or 2. ]   The acidic gas absorbent according to claim 8, wherein the cyclic amine compound is at least one selected from the group consisting of piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, and 2,6-dimethylpiperazine.   An acid gas, wherein an acid gas is removed from a gas containing the acid gas by contacting the gas containing the acid gas with the acid gas absorbent according to any one of claims 1 to 9. Removal method. An absorption tower comprising the acidic gas absorbent according to any one of claims 1 to 9, and contacting the acidic gas absorbent with a gas containing an acidic gas to remove the acidic gas from the gas;
A regenerating tower that removes the acid gas from the acid gas absorbent that has absorbed the acid gas and regenerates the acid gas absorbent;
An acidic gas removing device, wherein the acidic gas absorbent regenerated in the regeneration tower is reused in the absorption tower.

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