JP2012035169A - Carbon dioxide absorption method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover COin a simpler and easier way without spending much cost of energy such as electric power.SOLUTION: An adsorbent 103a which is produced by impregnating a porous body with an aqueous solution in which 2-aminoethanol is dissolved in water, is arranged in an atmosphere 104 where COis to be recovered. By using the adsorbent 103a constituted of the porous body in the pore of which 2-aminoethanol is carried, COentered in the pore is absorbed by 2-aminoethanol. Consequently COin the atmosphere 104 is absorbed by the adsorbent 103a.

Description

  The present invention relates to a carbon dioxide absorption method for absorbing carbon dioxide in a target atmosphere.

Carbon dioxide (CO ₂ ) is one of the causative gases for global warming, and reducing carbon dioxide in the atmosphere is an urgent problem and a long-term problem. The sources of CO ₂ cover various fields where carbon compounds are burning. For example, in a power generation facility such as a thermal power plant that uses a large amount of fossil fuel, a large amount of CO ₂ is generated. For this reason, techniques for recovering and storing discharged CO ₂ have been energetically studied.

For example, in the equipment as described above, a method for recovering CO ₂ in the combustion exhaust gas by bringing the combustion exhaust gas into contact with an alkanolamine aqueous solution has been studied. Examples of the alkanolamine that absorbs CO ₂ include monoethanolamine, triethanolamine, N-methyldiethanolamine, diisopropanolamine, and diglycolamine. Moreover, piperidine etc. are used for these alkanolamines as an absorption aid (refer patent document 1).

In addition, as a material of an absorbing solution that improves the removal efficiency by improving the removal rate of CO _{2 in} combustion exhaust gas, a linear or cyclic amine compound having a primary amino group, a linear chain having a secondary amino group Alternatively, those containing three or more kinds of amine compounds selected from cyclic amine compounds are used.

There is also a CO ₂ separation method for separating CO ₂ from factory process exhaust gas in a gaseous state. In this method, an absorption liquid containing hydrogen carbonate or metal ions constituting the carbonate is used. A supply gas containing CO ₂ is supplied to one side of the porous material impregnated with the absorbing solution, and the other side is decompressed. In this way, CO ₂ is absorbed from the supplied gas on one side, and CO ₂ is released on the other side where the pressure is reduced.

In addition, a CO ₂ recovery technique using a recovery liquid made of an ionic liquid has also been proposed (see Non-Patent Document 1). In this technique, using an ionic liquid is a salt which is a liquid at room temperature (20-25 ° C.), to absorb the CO ₂ in the ionic liquid, also so as to recover the CO ₂ absorbed in the ionic liquid.

Further, an efficient and low energy consumption, as a method for recovering CO ₂ to CO ₂ in the gas absorption and desorbed, the 2-amino-2-methyl-1-propanol, N- methyldiethanolamine, N- ethyl A method using 2-aminoethanol has been proposed (see Patent Document 2).

In addition, a method using a water-soluble phosphate compound as a material for absorbing CO _{2 in} combustion exhaust gas discharged from power generation equipment such as a thermal power plant has been proposed. This aqueous solution of a phosphoric acid compound is characterized by a large amount of CO ₂ absorption and absorption rate per unit volume, and low thermal energy required for regeneration.

Japanese Patent No. 3233809 JP 2008-168227 A

http://unit.aist.go.jp/tohoku/newsletter/newsletter22/2007_11_no22/newsletter_05.html, AIST Tohoku Newsletter, No 22, 2007.

However, in the above-described technique, the CO ₂ removal target gas is exhaust gas from the power generation facility, exhaust gas from the factory process, etc., and the amount of gas to be processed is very large, and the use of a bubbling device or an injection device is required. And power using electric power is required. However, the emission sources that emit CO ₂ are not limited to these large emission sources, and there are small distributed emission sources such as ordinary households and small-scale facilities. These dispersed emission sources have various CO ₂ concentrations to be discharged and also have a small emission amount. Therefore, in the recovery of CO ₂ from these dispersed emission sources, it is required that it can be easily performed at a lower cost without using energy such as electric power, and there is a problem that the above-described technique cannot meet this requirement.

The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to more easily collect CO ₂ without incurring energy costs such as electric power.

  The carbon dioxide absorption method according to the present invention includes a first step of impregnating a porous glass carrier with an aqueous solution of 2-aminoethanol, and carbon dioxide adsorption by drying the carrier impregnated with the aqueous solution in an inert gas. A second step of producing the material, and a third step of disposing the carbon dioxide adsorbing material in the target atmosphere and absorbing carbon dioxide in the atmosphere.

  In the carbon dioxide absorption method, the aqueous solution may have a volume concentration of 2-aminoethanol of 10% or more and less than 50%.

As described above, according to the present invention, since the carbon dioxide adsorbent produced by impregnating a carrier made of porous glass with an aqueous solution of 2-aminoethanol is used, energy costs such as electric power are applied. And an excellent effect that CO ₂ can be recovered more easily is obtained.

FIG. 1A is an explanatory diagram illustrating a carbon dioxide absorption method according to an embodiment of the present invention. FIG. 1B is an explanatory diagram illustrating a carbon dioxide absorption method according to an embodiment of the present invention. FIG. 1C is an explanatory diagram illustrating a carbon dioxide absorption method according to an embodiment of the present invention. FIG. 1D is an explanatory diagram illustrating a carbon dioxide absorption method according to an embodiment of the present invention. FIG. 2 is a characteristic diagram showing the state of CO ₂ reduction when an adsorbent sample produced using an aqueous solution with a 2-aminoethanol concentration of 40% is used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A to 1D are explanatory diagrams illustrating a carbon dioxide absorption method according to an embodiment of the present invention. First, the production of the adsorbent will be described. As shown in FIG. 1A, an aqueous solution 101 in which 2-aminoethanol is dissolved in water is produced in a container 102. For example, a 2-aminoethanol aqueous solution having a volume concentration of 20% may be used.

Next, as shown in FIG. 1B, a porous body (carrier) 103, which is porous glass having an average pore diameter of 4 nm, is immersed in the aqueous solution 101, and the porous body 103 is impregnated with the aqueous solution 101 (first step). The porous body 103 has, for example, an average pore diameter of 4 nm and a porosity of 28% with respect to the surface area, and is available from Giken Kagaku Co., Ltd. Alternatively, Baicol # 7930 manufactured by Corning may be used. The porous body 103 has a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm), for example. The porous body 103 must have an average pore size larger than that of the aqueous solution 101 or carbon dioxide (CO ₂ ) molecules. Therefore, the lower limit of the average pore diameter is about 2 nm at which the aqueous solution 101 and CO ₂ molecules can enter. In addition, the specific surface area of the porous body 103 in the present embodiment is 100 m ² or more per 1 g.

  After the porous body 103 described above is immersed in the aqueous solution 101 for 4 hours, for example, the pores of the porous body 103 are impregnated with the aqueous solution 101, and then the porous body 103 impregnated with the aqueous solution 101 is air-dried, as shown in FIG. The adsorbent (carbon dioxide adsorbent) 103a is produced by leaving it in a nitrogen gas stream for 24 hours to dry (second step). Here, since 2-aminoethanol has viscosity, the porous body 103 can be impregnated with the aqueous solution 101 having a concentration in a predetermined range.

  Therefore, the detection agent which consists of each component which comprises the aqueous solution 101 mentioned above is introduce | transduced into the adsorbent 103a, and 2-aminoethanol is carry | supported in the porous pore of the adsorbent 103a. As is well known, the porous body 103 includes a plurality of pores. These pores are through-holes connected from the opening on the surface of the porous body 103 to the inside.

  The term “support” refers to a state in which 2-aminoethanol is chemically, physically, or electrically bound to a carrier (base material). For example, the inner wall surface is covered with 2-aminoethanol. And / or a state in which 2-aminoethanol is deposited on the side wall in the hole.

Next, as shown in FIG. 1D, the adsorbent 103a is placed in an atmosphere 104 that is a CO ₂ recovery target. As described above, according to the adsorbent 103a composed of a porous body in which 2-aminoethanol is supported in the pores, CO ₂ that has entered the pores is absorbed by the 2-aminoethanol. Therefore, CO ₂ in the atmosphere 104 is absorbed by the adsorbent 103a (third step). Thus, according to the present embodiment, CO ₂ can be recovered more easily without incurring energy costs such as electric power.

  Next, the concentration of 2-aminoethanol in the aqueous solution impregnated in the porous body will be described.

  First, sample aqueous solutions (five types) with 2-aminoethanol concentrations of 10%, 20%, 30%, 40%, and 50% in volume fraction are prepared. Next, five pieces of chip-sized porous glass having an average pore diameter of 4 μm, 8 (mm) × 8 (mm) and a thickness of 1 (mm) are prepared. Next, the prepared porous glass is immersed in each sample aqueous solution for 4 hours, and then dried in a nitrogen stream for 24 hours to prepare five types of adsorbent samples.

Next, five containers (made of plastic) having an internal volume of 1.5 l are prepared, and the above-mentioned five kinds of adsorbent samples are accommodated in individual containers. A Vaisala infrared absorption CO ₂ meter is disposed inside each container. In addition, the initial concentration of CO ₂ in each container is 500 ppm. The internal temperature of each container is 20 ° C. and the humidity is 50%. This is equivalent to a general indoor environment.

As a result of this experiment, the amount of change in the concentration of CO ₂ after 18 hours in each container with respect to the use of each adsorbent sample is shown in Table 1 below.

Further, the adsorbent samples were prepared using an aqueous solution in which the concentration of 2-aminoethanol and 40%, as shown in FIG. 2, the concentration of CO ₂ in the container is reduced.

From the above results, it can be seen that an adsorbent sample prepared using an aqueous solution with a concentration of 50% has less change in CO ₂ concentration than other adsorbed samples. Moreover, evaporation of 2-aminoethanol was measured in an adsorbent sample prepared using an aqueous solution with a concentration of 50%. Therefore, it is understood that the aqueous solution should have a volume concentration of 2-aminoethanol of 10% or more and less than 50%.

  Next, as a comparative example with respect to the above-described embodiment, the result of the same experiment as described above using a porous glass chip impregnated with an aqueous solution of triethanolamine will be described.

  First, an aqueous sample solution having a triethanolamine concentration of 20% by volume is prepared. Next, a chip-sized porous glass having an average pore diameter of 4 μm, 8 (mm) × 8 (mm) and a thickness of 1 (mm) is prepared. Next, the prepared porous glass is immersed in the prepared sample aqueous solution for 4 hours, and then dried in a nitrogen stream for 24 hours to prepare a comparative sample.

Next, a container (made of plastic) having an internal volume of 1.5 l is prepared, and the above-described comparative sample is accommodated in the container. A Vaisala infrared absorption CO ₂ meter is arranged inside the container. The initial concentration of CO ₂ in the container is 500 ppm. Moreover, the internal temperature of a container is 20 degreeC and humidity is 50%. This is equivalent to a general indoor environment.

As a result of this experiment, there is no change in CO ₂ in the vessel after 18 hours. This result shows that porous glass impregnated with an aqueous solution of triethanolamine and dried does not absorb CO ₂ in the atmosphere. For example, if the target air is bubbled with triethanolamine, CO ₂ in the air is absorbed and reduced. However, it is considered that CO ₂ is hardly absorbed when triethanolamine is supported in the pores of the porous body.

As described above, CO ₂ recovery from a distributed emission source such as a general household requires that it can be performed at a lower cost without using energy such as electric power. Further, CO ₂ is also present in the atmosphere due to natural occurrence, and if there is a technique for recovering CO ₂ in the atmosphere without incurring costs such as electric power, it is considered that the utility value is high.

In order to meet these demands, the present invention has intensively studied a CO ₂ recovery method using an absorbent that absorbs CO ₂ without using power using electric power, and as a result, an aqueous solution of 2-aminoethanol is made porous. It was made by finding out that CO ₂ in the atmosphere can be adsorbed without using power by impregnating in the pores of the above. According to the present invention, CO ₂ existing in the atmosphere can be absorbed in a short time without using power.

  It should be noted that the present invention is not limited to the embodiment described above, and that many modifications can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above description, drying is performed in a nitrogen gas stream, but the present invention is not limited to this. For example, the drying is not limited to nitrogen gas, but may be performed in an inert gas such as argon.

  DESCRIPTION OF SYMBOLS 101 ... Aqueous solution, 102 ... Container, 103 ... Porous body, 103a ... Adsorbent (carbon dioxide adsorbent), 104 ... Atmosphere.

Claims (2)

A first step of impregnating a porous glass support with an aqueous solution of 2-aminoethanol;
A second step of preparing a carbon dioxide adsorbent by drying the carrier impregnated with the aqueous solution in an inert gas;
A carbon dioxide absorbing method, comprising: a third step of disposing the carbon dioxide adsorbent in a target atmosphere and absorbing carbon dioxide in the atmosphere. The carbon dioxide absorption method according to claim 1,
The method for absorbing carbon dioxide, wherein the aqueous solution has a volume concentration of 2-aminoethanol of 10% or more and less than 50%.

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