KR102176439B1 - Amine adsorbent for co2 capture process - Google Patents

Abstract

The present invention relates to an amine adsorbent that can be used at the rear end of an absorption tower and a stripping tower (regeneration tower) of a carbon dioxide capture process. The amine adsorbent of the present invention is a porous support; And metal ions of alkali metal or alkaline earth metal impregnated in the porous support. According to the present invention, there is an effect of suppressing the generation of secondary amines, which may be starting materials for toxic substances such as nitrosamine in the carbon dioxide capture process. In addition, the present invention improves the performance of a filter by simultaneously removing various harmful gases, extends the filter replacement cycle, and removes amines with excellent performance, thereby enabling high purity carbon dioxide to be collected.

Description

Amine adsorbent for carbon dioxide capture process {AMINE ADSORBENT FOR CO2 CAPTURE PROCESS}

The present invention relates to a possible amine adsorbent for use at the rear end of an absorption tower and a stripping tower (regeneration tower) that are finally discharged through a carbon dioxide capture process, and to an amine adsorbent for a carbon dioxide capture process including a porous support and metal ions.

In order to highly efficiently separate carbon dioxide discharged from industrial facilities, the chemical reactivity of bicarbonate or carbamate ions in the state in which carbon dioxide is dissolved in water is the best, and it is best to use a liquid absorption method because it is economical as it becomes larger. It is advantageous.

The chemical substance mainly used in the liquid phase absorption method for the mass treatment of carbon dioxide is an absorbent containing an amine component.

Since the amine component is corrosive, use water to dilute the concentration to 20-40 wt%. When water is used, carbon dioxide is ionized in water and converted into bicarbonate or carbamate, which has the effect of activating the mobility of molecules. For carbon dioxide capture, when an amine diluted with water is used in a liquid absorption method, the absorbent absorbs carbon dioxide and is gradually saturated, and the absorbent saturated with carbon dioxide can be heated and regenerated. As amines are naturally volatile substances, they can be discharged to the top of the absorption tower and the top of the stripping tower by the diffusion coefficient depending on the temperature.

The carbon dioxide-containing gas flowing into the absorption tower is selectively absorbed and removed by the absorbent by the absorbent, and substances having an equilibrium relationship between the temperature and pressure of the gas are discharged together to the top of the absorption tower. That is, combustion flue gas components and amine-based absorbent components may be mixed and discharged at the top of the absorption tower. Usually, most of the components are nitrogen, and oxygen, water vapor, and unrecovered carbon dioxide are the main components, but the amine component of the absorbent can be discharged in ppm units.

The stripping tower, which is operated for the purpose of regenerating the carbon dioxide absorbent, is a place where the reaction of removing the carbon dioxide dissolved in the absorbent by heating the aqueous amine absorbent absorbing carbon dioxide proceeds. Since the stripping tower is operated at a temperature higher than 100 degrees Celsius, which is higher than that of the absorption tower, water vapor, amines, and high concentration carbon dioxide (more than 99.9%) are more violently generated. The water vapor, amine, and high-concentration carbon dioxide reaching the top of the stripping tower go through a condenser, and the steam and amine are liquefied and recovered back to the stripping column to prevent loss of the absorbent. However, since tens of ppm of amine in equilibrium with the temperature of the condenser continues to be consumed in a series of absorbent regeneration processes, when the carbon dioxide capture process is continuously operated, the concentration of the absorbent must be checked and adjusted to a certain amount.

Nitrosamine, a secondary amine, may be generated at the top of the absorption tower through a radical reaction between nitrogen oxides and amines contained in the flue gas. Nitrosamine is a type of nitroso compound and is known to cause liver cancer. Nitrosamine produced through the reaction with amine is mainly produced in the absorption tower, but when NO ₂ , a water-soluble substance among nitrogen oxides, is regenerated in the stripping tower and reacts with the amine, it can also be produced in the stripping column. As a result, trace amounts of amines and nitrosamines, which are environmentally hazardous substances, may be generated in the absorption tower and stripping tower.

Among various amines, secondary amines have been reported to have a higher rate of production of nitrosamines than primary amines. In particular, PZ (Piperazine) and 2-MPZ (2-Methylpiperazine), which are widely used as carbon dioxide absorbents, correspond to secondary amines, and this may increase the production rate of harmful nitrosamines. In addition, 2-MPZ and PZ have the property of sublimation, so there is a possibility of being discharged into the atmosphere.

A small amount of discharged amine gas may cause odor, and some secondary amines are harmful to the human body, and amines act as impurities in the process of conversion, direct use, and compression to convert the collected high-purity carbon dioxide into other substances. There is a need for a more efficient environmentally friendly deamine adsorbent.

Korean Patent Publication No. 10-2011-0134926

An object of the present invention is to control adsorption of a trace amount of amine discharged from the rear end of the carbon dioxide capture process using an adsorbent. That is, when the process gas containing carbon dioxide is separated and discharged to the top of the absorption tower and the stripping tower after passing through the carbon dioxide capture process, it controls the emission of a trace amount of amine contained in the gas flow flowing to the top of the absorption tower or stripping tower. It is to present the preparation method of adsorbent and its effect.

In order to achieve the above object, the present invention is a porous support; And it is an aspect of the present invention to provide an amine adsorbent for a carbon dioxide trapping process comprising alkali metal or alkaline earth metal ions impregnated in the porous support.

The porous support may be activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, or metal-organic framework (MOF).

The metal ions may be K or Ca ions, and may include 0.78 to 2.44% by weight of metal ions based on 100% by weight of the total amine adsorbent.

The pore size of the amine adsorbent may be 400 to 600 ㅕ, and the specific surface area of the amine adsorbent may be 1130 to 1620 m ² /g.

In addition, the present invention comprises the steps of: (a) preparing a metal salt solution in which a metal ion precursor is dissolved; (b) impregnating the metal salt solution with a porous support; It is another aspect of the present invention to provide a method for producing an amine adsorbent for a carbon dioxide capture process comprising the step of (c) drying the impregnated porous support.

The metal ion in step (a) may be K or Ca, and the concentration of the metal salt solution in step (a) may be 0.5 to 2 M.

In step (b), the porous support may be activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, or metal-organic framework (MOF).

The step (c) may be performed at 90° C. at a speed of 10 to 20 RPM and under a vacuum of 150 to 200 torr.

According to the present invention as described above, by providing an amine adsorbent containing a porous support and metal ions, the effect of suppressing the generation of secondary amines, which can be starting materials for toxic substances such as nitrosamine in the carbon dioxide capture process There is.

In addition, by simultaneously removing various harmful gases, the performance of the filter can be improved, the filter replacement cycle can be extended, and amines can be removed with excellent performance, so that high-purity carbon dioxide can be collected.

1 shows a carbon dioxide capture process chart.
Figure 2 shows the concentration of 2-MPZ discharged in the carbon dioxide capture process to which the amine adsorbent is applied according to an embodiment of the present invention.
3 to 6 show the adsorption capacity and void volume for amine adsorption according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

FIG. 1 shows a carbon dioxide capture process. Referring to FIG. 1, in the carbon dioxide capture process, after cleaning the combustion exhaust gas including carbon dioxide in the washing tower 101, the cleaned combustion exhaust gas is transferred to the absorption tower 102. Thus, carbon dioxide (CO ₂ ) is primarily separated from the combustion exhaust gas through contact with an amine-based carbon dioxide absorbent in the absorption tower 102. At this time, the combustion exhaust gas from which carbon dioxide is separated from the absorption tower 102 may be discharged to the outside of the absorption tower 102, and the discharged combustion exhaust gas is PZ (Piperazine) and 2-MPZ ( It may include a secondary amine component of 2-Methylpiperazine). Thereafter, the absorbent to which carbon dioxide has been adsorbed is transferred to the stripping tower 105 through the first heat exchanger 104 by the first pump 103. After separating carbon dioxide from the absorbent to which carbon dioxide is adsorbed in the stripping tower 105, the absorbent is passed through the reheater 107, the second pump 108, the first heat exchanger 104, and the second heat exchanger 105. It is resupplied to the absorption tower 102. The stripping tower 105 transfers the carbon dioxide separated from the absorbent to the reflux tower 111 through the condenser 110, and discharges carbon dioxide gas from the reflux tower 111 to the outside to collect carbon dioxide. At this time, the carbon dioxide gas discharged from the reflux tower 111 may include a secondary amine component of PZ (Piperazine) and 2-MPZ (2-Methylpiperazine) capable of generating nitrosamine.

In order to remove the secondary amine component of PZ (Piperazine) and 2-MPZ (2-Methylpiperazine), the adsorbent according to one embodiment of the present invention is after the condensation tower 111 or the absorption tower 102 in the above-described carbon dioxide capture process. ) Can be applied after.

The amine adsorbent for a carbon dioxide capture process according to an embodiment of the present invention includes a porous support; And metal ions of alkali metals or alkaline earth metals. Preferably, the amine adsorbent for the carbon dioxide capture process of the present invention may include a carbon-based compound, an oxide, a silicon-based material, and a metal ion.

The porous support may be one or more materials selected from the group consisting of activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, and metal-organic framework (MOF).

The amine adsorbent may be a metal impregnated adsorbent containing metal ions, and the metal ions may contain 0.78 to 2.44 wt% of metal ions relative to a total of 100 wt%, and the metal ions are inorganic of K or Ca It may be a metal ion or contain both K and Ca.

Among the metal ions, K (potassium) may be provided from potassium carbonate (K ₂ CO ₃ ) as a precursor. Potassium carbonate has only 1,870 mg/kg of toxicity, which is about 0.1 times more than 26700 ppm of toluene. In addition, since it does not correspond to a secondary amine and does not react with an amine, the incidence of nitrosamine, a harmful substance, can be reduced.

The pore size of the amine adsorbent is meso pores, and preferably may be 400 to 600 Å in order to improve amine adsorption ability and facilitate entry and exit of amine molecules.

The specific surface area of the amine adsorbent may be 1130 to 1620 m ² /g. Since the adsorption amount tends to be proportional to the total specific surface area, the higher the specific surface area of the adsorbent is, the more advantageous it is, but the specific surface area of the amine adsorbent is preferably 1130 to 1620 m ² /g.

A method of preparing an amine adsorbent for a carbon dioxide capture process according to an embodiment of the present invention includes the steps of: (a) preparing a metal salt solution in which a metal ion precursor is dissolved; (b) impregnating the metal salt solution with a porous support; And (c) drying the impregnated porous support.

The metal salt solution in step (a) may be a K (potassium) precursor metal salt solution and a Ca (calcium) precursor metal salt solution.

The K (potassium) precursor solution can be used by dissolving KNO ₃ , K ₂ CO ₃ , KHCO ₃ , KOH, KCl or K ₂ (PO ₄ ) in water as a precursor for the supply of K, preferably K ₂ It can be used by dissolving CO ₃ in water.

The Ca (calcium) precursor solution may be used by dissolving Ca(NO ₃ ) ₂ , CaCl _2, or Ca ₃ (PO ₄ ) ₂ in water as a precursor for the supply of Ca.

The concentration of each of the K (potassium) precursor solution or the Ca (calcium) precursor solution may be prepared in 0.5 to 2 M (mol/l), and may be adjusted according to the solubility and impregnation amount of each precursor solution.

In the step (b), the porous support may be at least one material selected from the group consisting of activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, and metal-organic framework (MOF).

In the step (b), the porous support may be impregnated in each of the K (potassium) precursor metal salt solution and the Ca (calcium) precursor metal salt solution using a vacuum rotary evaporator to increase the content of K and Ca, and preferably , The porous support adsorbing moisture in the atmosphere is maintained at a speed of 10 to 20 RPM and a vacuum degree of 150 to 200 torr at 90°C and heated for 2 hours using a vacuum rotary evaporator to remove the adsorbed moisture from the atmosphere. The K (potassium) precursor metal salt solution and the Ca (calcium) precursor metal salt solution are injected into the porous support for at least 1 hour to impregnate.

The step (c) is to volatilize the moisture component of the injected metal salt solution after the impregnation is complete, and may be performed under a vacuum of 150 to 200 torr at a speed of 10 to 20 RPM at 90° C. for 4 hours. .

Hereinafter, the present invention will be described in more detail through examples. These examples are for illustrative purposes only, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not construed as being limited by these examples.

Preparation Example 1. Preparation of metal salt solution

As K (potassium) precursor into water (H ₂ O) as a solvent, _{KNO 3, K 2 CO 3,} KHCO 3, KOH, KCl or K ₂ (PO ₄₎ is dissolved K precursor metal salt solution 0.5 ~ 2M (mol / Prepare at the concentration of l).

Concentration of 0.5-2M (mol/l) of a Ca precursor metal salt solution in which Ca(NO ₃ ) ₂ , CaCl _2, or Ca ₃ (PO ₄ ) ₂ is dissolved as a Ca(calcium) precursor in water (H ₂ O) as a solvent Prepare with.

Preparation Example 2. Porous support

Activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, or a metal-organic framework (MOF) can be used as various candidate porous support groups. In this preparation example, activated carbon was prepared as a porous support.

Using a vacuum rotary evaporator, the adsorbent is heated at 90°C, a speed of 10 to 20 RPM, and a vacuum degree of 150 to 200 torr and heated for 2 hours to remove moisture from the atmosphere present in the adsorbent.

Example. Preparation of amine adsorbent

The adsorbent prepared in Preparation Example 2 was sequentially impregnated with the adsorbent prepared in Preparation Example 2 for the K precursor metal salt solution and the Ca precursor metal salt solution prepared in Preparation Example 1, respectively, and thus four samples with different impregnation amounts (Examples 1 to 4, (See Table 1 below) was prepared. Actually, if you want to change the impregnation amount, it can be adjusted by changing the concentration of the metal salt solution.

After the impregnation is complete, an amine adsorbent is prepared by removing moisture under a vacuum of 150 to 200 torr at a speed of 10 to 20 RPM at 90° C. for 4 hours to volatilize the moisture component of the metal salt solution.

Measurement Example 1.

The element content ratio (wt%) of EDS (Energy Dispersive X-ray) and EA (Elementary Analysis-CACL lab) analysis was analyzed for the samples (Examples 1 to 4) prepared in the above examples, and the results are as follows. It is summarized in Table 1.

Example 1
(NGB10408) Example 2
(NCG10408) Example 3
(SGA-100) Example 4
(SGP-100) EDS EA EDS EA EDS EA EDS EA N - 0.51 - 0.55 - 0.42 - 0.31 C 89.29 91.41 84.43 86.88 88.94 86.20 88.65 83.93 O 9.50 - 12.80 - 10.13 - 9.59 - Mg - - - - - - 0.16 - Na 0.11 - - - - - - - Al 0.11 - - - - - 0.28 - P 0.64 - - - - - - - Si - - 0.33 - 0.15 - 0.65 - S - 0.06 - 0.21 - 0.50 0.18 0.51 K 0.59 - 1.93 - 0.62 - - - Ca 0.08 - 0.51 - 0.16 - 0.33 - Fe - - - - - - 0.15 - H - - - - - - - - total
(wt%) 100 91.98 100 87.64 100 87.12 100 84.75 Specific surface area (m ² /g) 1115.1733 1137.9366 1611.1539 1061.4750

Measurement Example 2. Evaluation of amine adsorption performance

In order to evaluate the adsorption performance of the above embodiments, in the carbon dioxide capture process shown in FIG. 1, in order to evaluate the performance of the amine adsorbent prepared in the embodiment, with respect to the gas discharged after the condensation tower 111 or the absorption tower 102 Applied. The content of 2-MPZ, a secondary amine, was set to 55 ppm and injected into the adsorption tower, and the concentration of 2-MPZ discharged to the outside of the adsorption tower was measured over time. The results are shown in FIG. 2.

Referring to FIG. 2, since the amine adsorbent of Example 2 (NCG10408) has the best reactivity, a low concentration of 2-MPZ was maintained for a long time. In the case of Example 2, although the specific surface area of the adsorbent was lower than that of Example 3, it showed the ability to adsorb amines for a long time. This is considered to be because inorganic metals of K and Ca contained in the adsorbent chemically adsorb amines.

Measurement Example 3. Influence of pore volume

Examples 1 to 4 The adsorption performance according to the pore volume was evaluated for adsorbents, and the results are shown in Figs. 3 (Example 1), 4 (Example 2), 5 (Example 3) and Fig. 6 (Example 4). In Figures 3 to 6, ADS means adsorption and DES means desorption.

3 to 6, Example 1, Example 2, and Example 4 show the Langmuir isotherm, and Example 2 has a pore size distributed in 400 to 600 Å, preferably It can be seen that 500 Å of meso pores are present, and the adsorption capacity is higher than that of Example 1.

Example 3 shows the shape of a hysteresis curve. The hysteresis curve mainly occurs in an adsorbent having a multilayer structure, and it can be seen that in Example 3, multilayer adsorption occurs. It can be seen that formation of meso pores similar to that of Example 2 is observed, which has a better adsorption ability, and the pore size of the adsorbent is preferably 470 to 530 Å, more preferably 500 Å.

Such an adsorbent can be applied equally to not only activated carbon, but also zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, metal organic framework, and the like.

As described above, specific parts of the present invention have been described in detail, and for those of ordinary skill in the art, it is obvious that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereby. something to do. Therefore, it will be said that the practical scope of the present invention is defined by the appended claims and their equivalents.

101: washing tower 102: absorption tower
103: first pump 104: first heat exchanger
105: second heat exchanger 106: stripping tower
107: reheater 108: second pump
109: third pump 110: condenser
111: reflux tower

Claims (11)

Porous support; And
An amine adsorbent for a carbon dioxide capture process comprising metal ions of an alkali metal or alkaline earth metal impregnated in the porous support.
The method of claim 1,
The porous support is activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, or metal-organic framework (MOF) amine adsorbent for carbon dioxide capture process, characterized in that.
The method of claim 1,
The amine adsorbent for carbon dioxide capture process, characterized in that the metal ion is a K or Ca ion.
The method of claim 1,
The amine adsorbent for carbon dioxide capture process, characterized in that the amine adsorbent comprises 0.78 to 2.44% by weight of metal ions relative to a total of 100% by weight.
The method of claim 1,
The amine adsorbent for carbon dioxide capture process, characterized in that the pore size of the amine adsorbent is 400 to 600 Å.
The method of claim 1,
The amine adsorbent for carbon dioxide capture process, characterized in that the specific surface area of the amine adsorbent is 1130 to 1620 m ² /g.
(a) preparing a metal salt solution in which a precursor of a metal ion is dissolved;
(b) impregnating the metal salt solution with a porous support; And
(c) drying the impregnated porous support
Including,
The method of manufacturing an amine adsorbent for carbon dioxide capture process, wherein the metal ion is an ion of an alkali metal or an alkaline earth metal.
◈ Claim 8 was abandoned upon payment of the set registration fee. The method of claim 7,
The method for producing an amine adsorbent for a carbon dioxide capture process, wherein the metal ion is K or Ca.
◈ Claim 9 was abandoned upon payment of the set registration fee. The method of claim 7,
The method for producing an amine adsorbent for a carbon dioxide capture process, characterized in that the concentration of the metal salt solution is 0.5 to 2 M.
◈ Claim 10 was abandoned upon payment of the set registration fee. The method of claim 7,
The porous support is at least one of activated carbon, zeolite, silica gel, activated alumina, carbon molecular sieve, activated carbon fiber, and metal-organic framework (MOF).
◈ Claim 11 was abandoned upon payment of the set registration fee. The method of claim 7,
The drying step is a method of producing an amine adsorbent for a carbon dioxide capture process, characterized in that it is carried out under a vacuum of 150 to 200 torr at a speed of 10 to 20 RPM at 90 ℃.

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