WO2011071150A1

WO2011071150A1 - Carbon dioxide absorbent for use under high pressure, and method for absorption and collection of carbon dioxide under high pressure

Info

Publication number: WO2011071150A1
Application number: PCT/JP2010/072242
Authority: WO
Inventors: 洋町田; 信山本; 弘道岡部; 祐一藤岡
Original assignee: 財団法人地球環境産業技術研究機構
Priority date: 2009-12-11
Filing date: 2010-12-10
Publication date: 2011-06-16
Also published as: AU2010328990B2; JPWO2011071150A1; JP5812867B2; AU2010328990A1

Abstract

A water-containing liquid absorbent for absorbing and collecting carbon dioxide from a gas flow having a carbon dioxide partial pressure of 2 bar or more, the absorbent being characterized by containing 60 to 90 wt% of a tertiary aliphatic amine represented by general formula [1]; and a method for absorbing and collecting carbon dioxide using the water-containing liquid absorbent.

Description

High pressure carbon dioxide absorbent and high pressure carbon dioxide absorption and recovery method

The present invention is directed to removing carbon dioxide from a gas stream having a high carbon dioxide partial pressure (indicating above 2 bar), in particular to remove carbon dioxide from exhaust gas from a coal gasification process, and absorption and absorption It relates to a collection method.

In recent years, a rapid increase in greenhouse gas emissions such as carbon dioxide and methane accompanying human social activities has been cited as one of the causes of global warming. In particular, carbon dioxide is the most important greenhouse gas, and in accordance with the Kyoto Protocol issued in 2005, measures to reduce carbon dioxide emissions are urgently needed.

Today, CO2 contained in mixed gas is targeted for mixed gas discharged from thermal power plants, boilers in steelworks, kilns in cement factories, etc. that use coal, heavy oil, natural gas, etc., which are the sources of carbon dioxide as fuel. A series of carbon dioxide capture and storage (CCS) technologies, including carbon capture, compression, transportation, and injection, are attracting attention as bridging technologies to develop alternative energy alternatives to fossil fuels.

¡In order to put this storage technology into practical use, the lowest possible cost reduction is required. In the series of processes of carbon dioxide separation and recovery, compression, transportation, and press-fitting, the cost required for the previous stage separation and recovery and compression accounts for more than 70% of the total storage cost. Technology development is important. For this reason, the development of carbon dioxide separation and recovery technology by chemical absorption method mainly composed of alkanolamine aqueous solution has been energetically promoted for atmospheric pressure exhaust gas from power plants and steelworks.

Patent Document 1 discloses a method for removing carbon dioxide from a gas stream in which the partial pressure of carbon dioxide in the gas stream is less than 0.2 bar, and this gas stream is (A) at least 2 in the molecule. A method for removing carbon dioxide from a gas stream in contact with a liquid absorbent comprising an aqueous solution of an amine compound having three tertiary amino groups and an active agent selected from (B) a primary amine and a secondary amine is described. Has been.

In contrast, carbon dioxide separation and recovery technology using chemical absorption from high-pressure gas such as coal gasification product gas and mined natural gas has relatively few research examples compared to separation and recovery technology from atmospheric pressure exhaust gas. . However, since the pressure energy of the gas itself can be utilized for carbon dioxide separation recovery and compression, the cost during the carbon dioxide storage process, particularly in the separation recovery + compression process, may be significantly reduced. Therefore, the focus is on the development of chemical absorbents applicable to carbon dioxide separation from high pressure gas.

So far, the physical absorption method has attracted attention as a method for removing acidic gas containing carbon dioxide from gas having pressure. In the physical absorption method, it is known that the higher the partial pressure of the target gas component, the greater the amount of acid gas absorbed per unit absorption liquid compared to the chemical absorption method. Typical absorbents include cyclotetramethylene sulfone (sulfolane) and derivatives thereof, and absorbents composed of aliphatic amides, methanol, and polyethylene glycol dialkyl ethers (SELEXOL, Union Carbide). However, since any of the absorption liquids requires a reduced pressure in the process of desorbing the absorbed carbon dioxide and regenerating the absorption liquid, the effect of reducing the compression cost in the subsequent compression process is extremely low.

On the other hand, Patent Document 2 relates to an acid gas regeneration method performed under a pressure exceeding 3.5 bar absolute pressure and not exceeding 20 bar absolute pressure, and the separated gas stream generated from the regenerator is compressed and underground. It is described that it is press-fitted during storage. Moreover, triethanolamine etc. are mentioned as an acidic gas absorptive chemical agent. The absorbent illustrated in the examples consists of 43% by weight N-methyldiethanolamine and 57% by weight water.

The amine compounds having at least two tertiary amino groups in the molecule proposed in Patent Documents 1 and 2 above, an aqueous solution of N-methyldiethanolamine (MDEA) and an aqueous solution of triethanolamine are generally used. At concentrations up to 50% by weight, in the region where the partial pressure of carbon dioxide assumed by IGCC (Coal Gasification Combined Cycle) is high, the dispersibility is poor, and the efficiency of carbon dioxide recovery and amine regeneration becomes poor, and carbon dioxide recovery. Increased energy and cost. Furthermore, when MDEA is used in an amount of 60% by weight or more, it is difficult to put it to practical use because the handling property deteriorates due to the increase in viscosity and the absorption rate decreases.

On the other hand, Patent Document 3 describes a method for removing acid gas from a gas supply stream including a regeneration method in which an absorbing liquid containing acid gas at a high concentration is heated at a pressure higher than atmospheric pressure. . The absorbing liquid is a tertiary alkylamine selected from diamines, triamines and tetramines. It is described that it can be regenerated at a high pressure by using an aqueous amine solution at a high concentration (60 to 90% by weight).

However, in order to design a compact separation device that removes carbon dioxide from a gas stream, an amine having a high absorption rate and a high emission rate is important. Until now, in the field of absorption of carbon dioxide at a pressure higher than atmospheric pressure, no examination has been made on the absorption rate and the emission rate.

Special table 2007-527790 gazette International Publication No. 2005/009592 International Publication No. 2004/082809

The present invention provides a high-efficiency carbon dioxide absorbent and absorption and recovery method capable of achieving separation of carbon dioxide in a gas at a higher carbon dioxide absorption rate and emission rate than in the past in a region where the carbon dioxide partial pressure is high. The purpose is to do.

As described above, Patent Document 3 describes that in a region where the partial pressure of carbon dioxide is high, the amount of carbon dioxide recovered is improved by using an aqueous amine solution at a high concentration of 60% by weight or more.

Furthermore, when the present inventors use a tertiary aliphatic amine aqueous solution having no hydrogen bonding group and having an ether group at a high concentration, the absorption rate and the emission rate may be improved as well as the carbon dioxide recovery amount. I understood.

Therefore, the present inventors use a tertiary aliphatic amine aqueous solution that does not have a hydrogen bond group and has an ether group at a high concentration, thereby enabling a high absorption rate and high in a region where the partial pressure of carbon dioxide is high. It was possible to obtain an amine solution having a diffusion rate and a high carbon dioxide recovery amount, and obtained the knowledge that the above object could be achieved. The present invention has been completed based on these findings, and has been completed. The present invention provides the following carbon dioxide absorbent and absorption and recovery method.

Item 1. A hydrous liquid absorbent for absorbing and recovering carbon dioxide from a gas stream having a partial pressure of carbon dioxide in the gas stream of 2 bar or more, comprising a tertiary aliphatic amine represented by the general formula [1] A hydrous liquid absorbent comprising -90% by weight.
General formula [1]:

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and represent an alkyl group, R ⁵ and R ⁶ are the same or different and represent an alkylene group, and n = 1 to 5 is there. ]

Item 2. Item 5. The water-containing liquid absorbent according to Item 1, wherein the tertiary aliphatic amine is bis (2-dimethylaminoethyl) ether.

Item 3. (1) A step of absorbing the carbon dioxide from the gas flow by contacting the water-containing liquid absorbent according to Item 1 or 2 with a gas flow having a carbon dioxide partial pressure of 2 bar or more, and (2) the above step ( Heating the water-containing liquid absorbent that has absorbed carbon dioxide obtained in 1) to desorb and recover carbon dioxide;
Carbon dioxide absorption and recovery method comprising:

Item 4. Item 4. The step (1) is performed at a carbon dioxide partial pressure of 2 to 40 bar, and the step (2) is performed at a carbon dioxide partial pressure of 2 bar or more. Carbon dioxide absorption and recovery method.

Item 5. Item 5. The method for absorbing and recovering carbon dioxide according to Item 3 or 4, wherein the step (1) is performed at a temperature of 25 to 60 ° C, and the step (2) is performed at a temperature of 70 to 120 ° C. .

According to the absorbent of the present invention, since the absorption rate and the emission rate of carbon dioxide are high in an environment where the partial pressure of carbon dioxide is high, a more compact separation device can be designed and an economical device can be obtained. Moreover, since the amount of carbon dioxide recovered increases in an environment where the carbon dioxide partial pressure is high, separation with low energy becomes possible.

6 is a graph showing the results of carbon dioxide absorption in Test Example 2. 7 is a graph showing the results of carbon dioxide absorption rate, emission rate, and CO ₂ recovery amount in Test Example 3.

Hereinafter, the water-containing liquid absorbent and the carbon dioxide absorption and recovery method for absorbing and recovering carbon dioxide according to the present invention will be described in detail.

Water-containing liquid absorbent for absorbing and recovering carbon dioxide The water-containing liquid absorbent of the present invention absorbs and recovers carbon dioxide from a gas stream in which the partial pressure of carbon dioxide in the gas stream is 2 bar or more, and in general 60 to 90% by weight of a tertiary aliphatic amine represented by the formula [1] is contained.
General formula [1]:

R ¹ , R ² , R ³ and R ⁴ in the general formula [1] are the same or different and are an alkyl group, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. It is a group.

Specific examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, and hexyl.

Specific examples of the alkyl group having 1 to 3 carbon atoms include methyl, ethyl, n-propyl, and isopropyl.

R ⁵ and R ^{6 in} the general formula [1] are the same or different and are an alkylene group, preferably an alkylene group having 1 to 6 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms.

Specific examples of the alkylene group having 1 to 6 carbon atoms include methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, and hexylene.

Specific examples of the alkylene group having 1 to 3 carbon atoms include methylene, ethylene, n-propylene, and isopropylene.

In the general formula [1], n is an integer selected from 1 to 5, preferably 1 to 4, more preferably 1 to 2.

Examples of the tertiary aliphatic amine represented by the general formula [1] include bis (2-dimethylaminoethyl) ether.

The above-mentioned tertiary aliphatic amine can be produced as a known method according to the description in References 1 to 4 below, or is commercially available because it is commercially available.

Specifically, the tertiary aliphatic amine can be synthesized based on the following formula using diethylene glycol or polyethylene glycol as a raw material as described in the following documents 1 to 4.
Me ₂ NH + HO-CH _2- (CH ₂ -O-CH ₂ ) _n -CH ₂ -OH → Me ₂ N-CH _2- (CH ₂ -O-CH ₂ ) _n -CH ₂ -NMe ₂
Document 1: International Publication No. 2005/110969 Document 2: Japanese Patent Laid-Open No. 9-20735 Document 3: European Patent Application Publication No. 300323 Document 4: West German Patent Application Publication No. 3422610

The heat of reaction of the tertiary aliphatic amine is desirably 40 to 70 kJ / mol-CO _2, particularly 45 to 60 kJ / mol-CO ₂ . Here, the reaction heat is used to mean the amount of heat generated when 1 mol of CO ₂ is absorbed at 40 ° C. and atmospheric pressure.

It is desirable that the tertiary aliphatic amine has an absorption rate of 2 to 5 times, an emission rate of 2 to 5 times, and a carbon dioxide recovery amount of 2 to 3 times that of MDEA.

The water-containing liquid absorbent according to the present invention contains 60 to 90% by weight of the tertiary aliphatic amine. If it is this range, it will be excellent in the absorption rate and emission rate of a carbon dioxide. Preferably 60 to 80% by weight, more preferably 60 to 70% by weight.

The water-containing liquid absorbent of the present invention may also contain an antioxidant, a corrosion inhibitor, a physical absorbent and the like as components other than the tertiary aliphatic amine.

Examples of the antioxidant include BHT (dibutylhydroxytoluene), BHA (butylhydroxyanisole), sodium erythorbate, sodium sulfite, sulfur dioxide and the like.

Examples of the physical absorbent include cyclotetramethylene sulfone (sulfolane) and derivatives thereof, aliphatic acid amide (acetylmorpholine, N-formylmorpholine), N-alkylated pyrrolidone and a corresponding piperidone such as N-methylpyrrolidone (NMP), And dialkyl ethers such as propylene carbonate, methanol, and polyethylene glycol.

The partial pressure of carbon dioxide in the gas stream in which the water-containing liquid absorbent of the present invention absorbs and recovers carbon dioxide is 2 bar or more. If it is this range, it will be excellent in the absorption rate and emission rate of a carbon dioxide. It is preferably 10 bar or more, more preferably 10 to 40 bar.

Examples of the gas flow include exhaust gas from a coal gasification process, mined natural gas, and the like, and the concentration of carbon dioxide in the gas is usually about 20 to 50% by volume, particularly about 30 to 40% by volume. That's fine. In such a carbon dioxide concentration range, the effects of the present invention are suitably exhibited. The gas stream may contain gas such as water vapor, CO, H ₂ S, COS, and H _{2 in} addition to carbon dioxide.

Carbon dioxide absorption and recovery method The carbon dioxide absorption and recovery method of the present invention comprises: (1) contacting the above-mentioned hydrated liquid absorbent with a gas stream having a partial pressure of carbon dioxide of 2 bar or more, thereby And (2) heating the hydrated liquid absorbent that has absorbed carbon dioxide obtained in the above step (1) to desorb and recover the carbon dioxide.

Process (1)
In step (1), carbon dioxide is absorbed from the gas stream by contacting the hydrated liquid absorbent with a gas stream having a carbon dioxide partial pressure of 2 bar or more.

There is no particular limitation on the method for bringing the gas flow into contact with the above-mentioned water-containing liquid absorbent. For example, a method of bubbling a gas flow into the absorbent and absorbing it, a method of dropping the absorbent into a gas stream (a spray or spray method), or a magnetic or metal mesh filler This is performed by a method in which the gas flow and the absorbent are brought into countercurrent contact in the absorption tower.

Step (1) is preferably performed at a partial pressure of carbon dioxide of 2 to 40 bar, particularly 2 to 20 bar. Step (1) is preferably performed at a temperature of 25 to 60 ° C., particularly 40 to 60 ° C.

Step (2)
In the step (2), the water-containing liquid absorbent that has absorbed the carbon dioxide obtained in the step (1) is heated to desorb and recover the carbon dioxide.

As a method of desorbing carbon dioxide from a water-containing liquid absorbent that has absorbed carbon dioxide and recovering pure or high-concentration carbon dioxide, a method of heating the absorbent and bubbling it in a kettle as in distillation, a shelf Examples thereof include a method in which a liquid interface is expanded and heated in a plate tower, a spray tower, a desorption tower containing a magnetic or metal mesh filler. Thereby, carbon dioxide is released from the absorbent and released.

Step (2) is preferably performed at a carbon dioxide partial pressure of 2 to 8 bar or more, particularly 2 to 80 bar. Step (2) is preferably performed at a temperature of 70 to 120 ° C., particularly 90 to 120 ° C. The upper temperature limit is not limited to 120 ° C., and it can be used even at a temperature higher than 120 ° C.

The absorbent after desorbing carbon dioxide is sent again to step (1) and recycled. During this time, the heat applied in the step (2) is effectively used for raising the temperature of the absorbent by heat exchange with the absorbent in the circulation process, and the energy of the entire recovery process is reduced.

The purity of carbon dioxide recovered in this way is usually extremely high, about 95 to 99.9% by volume. This pure carbon dioxide or high-concentration carbon dioxide is used as a chemical, a raw material for synthesizing a high-molecular substance, or a cooling agent for freezing food. In addition, it is possible to sequester and store the recovered carbon dioxide in the underground, where technology is currently being developed. At that time, the higher the pressure of the carbon dioxide recovered in the step (2), the lower the energy required for compression to 100 to 150 bar, which is required for storage.

Hereinafter, examples will be given to explain the present invention in more detail. However, the present invention is not limited to these examples.

Reagents and gas types used in the reagent examples and comparative examples are as follows.

Experimental method Measurement of carbon dioxide absorption rate, emission rate and recovery amount for water-containing liquid absorbent is carbon dioxide cylinder, nitrogen cylinder, carbon dioxide flow controller, nitrogen gas flow controller, high pressure vessel (600 cc), condenser, pressure regulating valve This was performed using a device in which a flow meter and a CO ₂ concentration meter were sequentially connected. Two oil baths with temperatures controlled at 40 ° C and 120 ° C were connected around the high-pressure vessel.

After adding the water-containing liquid absorbent (300 cc) into the high-pressure vessel, the air in the high-pressure vessel was replaced with nitrogen under the atmospheric pressure of the vessel.

The pressure adjustment valve was adjusted so that the pressure in the high-pressure vessel reached the specified pressure (0.2 to 40 bar), and the nitrogen gas flow rate controller was set to 3 minL / min and pressure increase was started. A 40 ° C. oil bath was circulated around the high pressure vessel to maintain the temperature of the high pressure vessel at 40 ° C. The temperature of the condenser is kept at 5 ° C, and it plays the role of returning the volatilized water-containing liquid absorbent into the high-pressure vessel.

After the temperature and pressure were stabilized, carbon dioxide was absorbed by setting the carbon dioxide flow rate controller to 0.3 to 2.7 L / min and the nitrogen gas flow rate controller to 0.3 to 2.7 L / min. The amount of carbon dioxide absorbed by the water-containing liquid absorbent was calculated from the difference between the flow rate at the inlet, the gas composition and the flow meter at the outlet, and the CO ₂ concentration meter.

After the carbon dioxide absorption process is completed, the temperature of the high-pressure vessel is raised to 120 ° C by switching the oil bath at 40 ° C circulating around the high-pressure vessel to an oil bath at 120 ° C. went. The amount of carbon dioxide released from the water-containing liquid absorbent was calculated from the difference between the inlet flow rate, gas composition, outlet flow meter, and CO ₂ concentration meter.

The absorption rate of carbon dioxide with respect to the water-containing liquid absorbent was defined as the amount of absorption per unit time at the start of carbon dioxide absorption.

The emission rate of carbon dioxide with respect to the water-containing liquid absorbent was defined as the amount of absorption per unit time at the start of carbon dioxide emission.

The amount of carbon dioxide recovered with respect to the water-containing liquid absorbent was defined as a value obtained by subtracting the amount of carbon dioxide absorbed at 120 ° C. from the amount of carbon dioxide absorbed at 40 ° C.

Test example 1
An absorption / dissipation test of carbon dioxide was performed using an absorption device (not shown). The composition of the water-containing liquid absorbent used in this test example was 30% by weight and 60% by weight of Bis (2DMAE) ER, and 35% by weight of MDEA. Absorption conditions and emission conditions in this test example are absorption conditions of 40 ° C., 16 bar (CO ₂ partial pressure), emission conditions of 120 ° C., 16 bar (CO ₂ partial pressure), and absorption conditions of 40 ° C., 0.2 bar (CO ₂ Partial pressure) and emission conditions were 120 ° C. and 0.2 bar (CO ₂ partial pressure).

Table 3 shows the results of carbon dioxide absorption rate, emission rate, and CO ₂ recovery in this test example.

As shown in Table 3, Bis (2DMAE) ER had a low absorption rate and a high release rate at 0.2 bar, and the amount of carbon dioxide recovered was small. However, the absorption rate and the emission rate improved at 16 bar, and the absorption rate and the emission rate were large when the amine concentration was 60% by weight, and the CO ₂ recovery was also large. For MDEA, the higher the partial pressure of CO ₂ , the higher the absorption rate, the emission rate and the CO ₂ recovery, but no significant increase was observed as much as 60% by weight of Bis (2DMAE) ER.

Test example 2
An absorption / dissipation test of carbon dioxide was performed using an absorption device (not shown). The composition of the water-containing liquid absorbent used in this test example was 30% and 60% by weight of Bis (2DMAE) ER, 35% and 60% by weight of MDEA, and 30% and 60% by weight of PMDETA. Absorption conditions and emission conditions in this test example were absorption conditions of 40 ° C. and 16 bar (CO ₂ partial pressure), and emission conditions of 120 ° C. and 16 bar (CO ₂ partial pressure).

MDEA corresponds to the absorbent of the invention of Patent Document 2 (International Publication No. 2005/009692), and PMDETA corresponds to the absorbent of the invention of Patent Document 3 (International Publication No. 2004/082809).

The results of carbon dioxide absorption in this test example are shown in FIG. 1, and the results of carbon dioxide absorption rate, emission rate, and CO ₂ recovery are shown in Table 4.

In FIG. 1, the value obtained by subtracting the carbon dioxide concentration in liquid at 120 ° C. from the carbon dioxide concentration in liquid at 40 ° C. indicates the amount of carbon dioxide recovered.

As shown in Figure 1, MDEA showed no significant change in carbon dioxide recovery at 35 wt% and 60 wt%, while Bis (2DMAE) ER recovered carbon dioxide at 60 wt% compared to 30 wt%. The amount increased.

Also, as shown in Table 4, Bis (2DMAE) ER has a higher absorption rate and emission rate at 60% by weight than that of PMDETA and MDEA, and also shows a large value for carbon dioxide recovery. From this, it can be seen that the absorbent of the present invention has particularly high absorption rate and emission rate as compared with the absorbents of Patent Documents 2 and 3.

Test example 3
An absorption / dissipation test of carbon dioxide was performed using an absorption device (not shown). The composition of the water-containing liquid absorbent used in this test example was Bis (2DMAE)

ER

30, 50, 60, 70, 80 and 90% by weight. Absorption conditions and emission conditions in this test example were absorption conditions of 40 ° C. and 16 bar (CO ₂ partial pressure), and emission conditions of 120 ° C. and 16 bar (CO ₂ partial pressure).

Table 5 and FIG. 2 show the results of carbon dioxide absorption rate, emission rate, and CO ₂ recovery amount according to this test example.

As shown in FIG. 2, the absorption rate increased greatly from 60 to 90% by weight compared to 30 to 50% by weight. Further, the emission rate and the carbon dioxide recovery amount reached the maximum at 60% by weight. From the above results, it was found that the Bis (2DMAE) ER concentration showed high performance at 60 to 90% by weight.

Test example 4
An absorption / dissipation test of carbon dioxide was performed using an absorption device (not shown). The composition of the water-containing liquid absorbent used in this test example was Bis (2DMAE) ER 60% by weight. Absorption conditions and emission conditions in this test example were absorption conditions of 40 ° C., emission conditions of 120 ° C., and pressures during absorption and emission were 0.2, _2, 16, and 40 bar (CO ₂ partial pressure).

Table 6 shows the results of the carbon dioxide absorption rate, the emission rate, and the CO ₂ recovery amount according to this test example.

As shown in Table 6, the absorption rate and the release rate were 100 g / L hr or more at 2 bar or more, and showed larger values as the CO ₂ partial pressure increased. The amount of carbon dioxide recovered was 100 g / L or more at 2 bar or more. From the above results, it was found that the CO ₂ partial pressure was 2 bar or more and high performance was exhibited. Further, it was confirmed that the carbon dioxide recovery amount was 100 g / L or more under the absorption conditions of 40 ° C., the CO ₂ partial pressure of 40 bar, the emission conditions of 120 ° C., the CO ₂ partial pressure of 80 bar.

From these results, when using Bis (2DMAE) ER 60-90 wt% hydrous liquid absorbent, when removing carbon dioxide from a gas stream where the partial pressure of carbon dioxide in the gas stream is 2 bar or more, It has been found that carbon dioxide in a gas can be absorbed and released more efficiently and with lower energy consumption than before.

In addition, the water-containing liquid absorbent having two or more ether groups has the same absorption rate, emission rate, and recovery amount as bis (2-dimethylaminoethyl) ether, but the vapor pressure is reduced, so that the volatilization amount can be reduced.

Claims

A hydrous liquid absorbent for absorbing and recovering carbon dioxide from a gas stream having a partial pressure of carbon dioxide in the gas stream of 2 bar or more, comprising a tertiary aliphatic amine represented by the general formula [1] A hydrous liquid absorbent comprising -90% by weight.
General formula [1]:

[Wherein R 1 , R 2 , R 3 and R 4 are the same or different and represent an alkyl group, R 5 and R 6 are the same or different and represent an alkylene group, and n = 1 to 5 is there. ]
The water-containing liquid absorbent according to claim 1, wherein the tertiary aliphatic amine is bis (2-dimethylaminoethyl) ether.
(1) A step of absorbing carbon dioxide from a gas flow by contacting the water-containing liquid absorbent according to claim 1 with a gas flow having a carbon dioxide partial pressure of 2 bar or more, and (2) the step (1) Heating the water-containing liquid absorbent that has absorbed carbon dioxide obtained in step 2) to desorb and recover carbon dioxide,
Carbon dioxide absorption and recovery method comprising:
The step (1) is performed at a carbon dioxide partial pressure of 2 to 40 bar, and the step (2) is performed at a carbon dioxide partial pressure of 2 bar or more. Of carbon dioxide absorption and recovery.
The method for absorbing and recovering carbon dioxide according to claim 3, wherein the step (1) is performed at a temperature of 25 to 60 ° C, and the step (2) is performed at a temperature of 70 to 120 ° C.