KR102096862B1 - Method for Regenerating of Absorbents for Acidic Gas Removal using Transition Metal oxide catalyst - Google Patents

Abstract

The present invention relates to the regeneration of an absorbent for removing acidic gas, and more particularly, to a method for absorbing acidic gas using an absorbent for removing acidic gas and regenerating the absorbent using a transition metal oxide as a catalyst. In the method for regenerating an absorbent for removing acidic gas using the transition metal oxide catalyst of the present invention, the location of the Bronzed acid and Lewis acid on the surface of the metal oxide absorbs acid gas, especially carbon dioxide. The carbon dioxide is removed by promoting the decomposition of the carbamate in which the absorbent and carbon dioxide are combined. It is possible to regenerate the absorbent with a regeneration heat lower than that of the conventional absorbent, thereby regenerating the absorbent and capturing carbon dioxide at a low cost with high efficiency.

Description

{Method for Regenerating of Absorbents for Acidic Gas Removal using Transition Metal oxide catalyst}

The present invention relates to the regeneration of an absorbent for removing acidic gas, and more particularly, to a method for absorbing acidic gas using an absorbent for removing acidic gas and regenerating the absorbent using a transition metal oxide as a catalyst.

As the industry is advanced and modern people are enriched in life, the problem of disposal of high-concentration organic waste such as livestock manure and food waste is emerging seriously. Many studies have been conducted to turn organic waste into resources, and among them, the use of biogas derived from organic waste has attracted attention. The main components of these organic waste biogas are methane (CH ₄ ) 50 ~ 75 vol.%, Carbon dioxide (CO ₂ ) 25 ~ 45 vol.%, Hydrogen sulfide (H ₂ S) 2,000 ~ 3,000 ppm, moisture and other 5 It contains a large amount of acid gas as vol.%. Methane (CH ₄ ) and carbon dioxide (CO ₂ ), which occupy most of the biogas composition, are representative greenhouse gases that need to be captured and resourced.

As a technique for separating acidic gases including carbon dioxide from organic waste resources, a chemical absorption method, a physical absorption method, or a membrane separation method is known, and a chemical absorption method with high absorption efficiency is mainly used in industrial sites. In the chemical absorption method, wet absorption technology and dry adsorption technology are commercialized and operated, and the efficiency of the wet absorption technology is high. Among the chemical absorption methods, the carbon dioxide absorption process by an amine-based absorbent is a chemical absorption process using an alkanolamine in which an amine and a hydroxyl group are combined as an absorbent as an absorbent, an absorption tower that selectively absorbs carbon dioxide from an inlet gas, and an absorbent that absorbs carbon dioxide. It consists of a regeneration tower (heated regeneration tower) and ancillary equipment for regeneration. It is known as a process that can effectively capture carbon dioxide generated in energy-consuming processes in use in various industries including power plants, alkanolamines, especially monoethanolamine (MEA), diethanolamine (DEA) and methyl Diethanolamine (methyldiethanolamine, MDEA) is a typical amine-based absorbent. In addition to amine-based absorbents, research is being conducted to develop various absorbents, but there are limitations in developing absorbers with higher efficiency than amine-based absorbers such as cost, operating equipment, and carbon dioxide absorption.

The amine absorbent can recover carbon dioxide with an efficiency of about 75-90%, but despite this high separation efficiency, this technology limits the amine concentration in solution due to problems such as high heat energy required for absorbent regeneration and corrosion of the device. , It has problems such as removal of moisture from the recovered gas, loss of absorbents due to volatility, deterioration of absorbents by additional substances or high heat, and oxidation of absorbents by bonding with oxygen. The energy required for the carbon dioxide absorption process is generally composed of renewable energy (about 75%) and other process energy (about 25%), of which renewable energy is composed of process heat and reaction heat. In order to reduce renewable energy, it is necessary to reduce process heat, which accounts for most of the renewable energy.

In order to solve this problem, studies for energy saving required for collecting acid gas and regenerating absorbents are being actively conducted. Korean Patent Publication No. 2013-0002828 discloses a technique for discharging carbon dioxide while maintaining a pressure inside the regeneration tower by supplying a circulating solvent having a lower evaporation heat and / or sensible heat than the solvent of the liquid carbon dioxide absorbent to the bottom of the regeneration tower. This promotes carbon dioxide emission using a circulating solvent with low evaporation heat and / or sensible heat, but has low thermal energy saving efficiency because it regenerates the absorbent using steam inside the regeneration tower. In addition, among them, solid acid catalysts H-ZSM-5 and γ-Al ₂ O ₃ are known as an absorbent regeneration method using a catalyst (idem et al.), And can reduce the heat of regeneration of the monoethanolamine absorbent. The process of regenerating absorbents using these catalysts is useful for reducing regeneration heat.

Therefore, it is required to develop a technology to reduce the energy required for the process of regenerating the absorbent for removing acid gas.

Korea Patent Publication 2013-0002828

The present invention has been devised to solve the above problems, and absorbs acid gas using an absorbent for removing acid gas, and uses an transition metal oxide catalyst to regenerate the absorbent, thereby reducing the energy required to collect the acid gas. It is intended to provide a method for regenerating an absorbent for removal.

In order to solve the above problems, the present inventors have completed the present invention by discovering that the transition metal oxide catalyst can be used to reduce the renewable energy by using it in the regeneration process of the acid gas removal absorbent.

The present invention comprises the steps of absorbing acid gas using an absorbent for removing acid gas to obtain an absorbent absorbing acid gas; And removing the acid gas by adding a transition metal oxide catalyst to the absorbent absorbing the acid gas to regenerate the absorbent, wherein the transition metal oxide is Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O and NiO. Provided is a method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst, which promotes the decomposition of carbamate in an absorbent solution for removing acidic gases and is selected from the group consisting of.

The present invention also the absorbent is monoethanolamine (monoethanolamine, MEA), diethanolamine (DEA), triethanolamine (TEA), tetraethylenepentamine (TEPA), triethylenetetramine, TETA), N-methyl diethanolamine (MDEA), 3-Isobutoxypropylamine, Dimethylaminoethylamine, Diglycolamine (DGA), Hexylamine ( Hexylamine), 2-Amino-2-methylpropanol (AMP, Hexamethylenediamine), Propylamine, Dipropylamine, Butylamine ( Butylamine, Isobutylamine, 2-Ethylhexylamine, 4-Aminobutanol, 3-Methoxypropylamine, Allylamine, Methyl Diallylamine (Methyldiallylamine), Pentylami ne), Isoamylamin, N-Methylethylamine, 2-Octylamine, and 2-Hydroxyethylaminopropylamine, Piperazine ) And triisopropanolamine (TIPA), wherein at least one selected from the group consisting of a transition metal oxide catalyst provides a method for regenerating an absorbent for removing acidic gases using a catalyst.

The present invention also provides a method for regenerating an absorbent for removing acidic gas using a transition metal oxide catalyst, wherein the absorbent is monoethanolamine (MEA).

The present invention also provides a method for regenerating an absorbent for removing acidic gas using a transition metal oxide catalyst, wherein the transition metal oxide catalyst is added at 0.1 wt% to 20 wt% based on the weight of the absorbent.

The present invention also provides a method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst, wherein the regeneration step is performed in a temperature range of 40 ° C to 85 ° C.

The present invention also provides a method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst, wherein the method further comprises reusing the regenerated absorbent for removing acidic gases.

The present invention also provides a method for regenerating an absorbent for removing acidic gas using a transition metal oxide catalyst, wherein the acidic gas is carbon dioxide.

In the method for regenerating an absorbent for removing acidic gas using the transition metal oxide catalyst of the present invention, the location of the Bronzed acid and Lewis acid on the surface of the metal oxide absorbs acid gas, especially carbon dioxide. The carbon dioxide is removed by promoting the decomposition of the carbamate in which the absorbent and carbon dioxide are combined. It is possible to regenerate the absorbent with a regeneration heat lower than that of the conventional absorbent, thereby regenerating the absorbent and capturing carbon dioxide at a low cost with high efficiency.

1 is a pyridine adsorption FT-IR spectrum showing the acid point of a transition metal oxide according to an embodiment of the present invention.
2 is a graph showing the desorption results of carbon dioxide over time and temperature using transition metal oxide Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O, or NiO as a catalyst according to one embodiment of the present invention, (a ) And (b) temperature range of 40-85 ° C, (c) and (d) temperature range of 40-80 ° C, (e) and (f) temperature range of 40-75 ° C, (g) It is a graph showing the results of regeneration of absorbents tested in a temperature range of 40-70 ° C, and (h) is a graph showing the amount of carbon dioxide released at each temperature for each catalyst.
3 (a) to (g) is a transition metal oxide Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O or NiO as a catalyst according to one embodiment of the present invention, the desorption rate over time of carbon dioxide It is a graph to show.
Figure 4 shows the carbon dioxide load of the lean solution obtained from the total solution at the end of the experiment according to an embodiment of the present invention.
5 is a graph evaluating the absorption capacity of regenerated carbon dioxide according to an embodiment of the present invention. (a) shows the carbon dioxide absorption capacity of the regenerated carbon dioxide absorbent using the catalyst of the present invention at a temperature condition of 40-85 ° C, and (b) is a graph showing the amount of carbon dioxide stripped during regeneration of the carbon dioxide absorbent using a transition metal catalyst. .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings, so that those skilled in the art to which they have ordinary knowledge can easily practice.

Prior to the detailed description of the present invention, terms or words used in the present specification and claims described below should not be interpreted as being limited to a conventional or dictionary meaning. Therefore, the configuration shown in the embodiments and drawings described in this specification is only one of the most preferred embodiments of the present invention and does not represent all of the technical spirit of the present invention. It should be understood that there may be equivalents and variations.

In one aspect, the present invention comprises the steps of absorbing acid gas using an absorbent for removing acid gas to obtain an absorbent absorbing acid gas; And adding the transition metal oxide catalyst to the absorbent absorbing the acid gas to remove the acid gas to regenerate the absorbent. In the present invention, the acid gas may be, for example, biogas among organic waste resources, preferably biogas containing carbon dioxide, and carbon dioxide is described herein as an example of acid gas, but is not limited thereto. .

The method for regenerating the absorbent of the present invention can be performed in a regeneration tower during a carbon dioxide capture process having an absorption tower and a regeneration tower. In the carbon dioxide capture process, the carbon dioxide contained in the exhaust gas injected into the absorption tower is chemically absorbed, and the absorbent solution absorbing the carbon dioxide is injected into the regeneration tower to be regenerated. The preferred temperature for absorbing carbon dioxide of the absorption tower is in the range of about 0 ° C to about 80 ° C, particularly in the range of about 20 ° C to about 60 ° C, and the preferred pressure is normal pressure to about 80 atmospheres, particularly normal pressure to 60 atmospheres. When absorbing acid gas, the lower the temperature and the higher the pressure, the higher the amount of acid gas absorbed. An amine-based compound may be used as the absorbent used in the absorption tower, and the amine-based compound is not limited to any one as long as it is an amine-based compound commonly used as a carbon dioxide absorbent. For example, the amine-based compound is at least one primary, secondary, tertiary or sterically hindered amine or amino acid salt-based compound, preferably monoethanolamine. When carbon dioxide and amine react in the absorption tower, carbon dioxide can be absorbed while forming carbamate (2RNH ₂ + CO ₂ = RNHCOO ^- .RNH ₃ ⁺ ). In one embodiment, the amine-based absorbent is noethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), tetraethylenepentamine (TEPA), triethylenetetraamine (TEPA) Triethylenetetramine, TETA), N-methyl diethanolamine (MDEA), 3-Isobutoxypropylamine, Dimethylaminoethylamine, Diglycolamine (DGA), Hexyl Hexylamine, 2-Amino-2-methylpropanol (AMP), Hexamethylenediamine (HMDA), Propylamine, Dipropylamine, Butyl Butylamine, Isobutylamine, 2-Ethylhexylamine, 4-Aminobutanol, 3-Methoxypropylamine, Allylamine , Methyldiallylamine, pentylamine (Pen tylamine, Isoamylamin, N-Methylethylamine, 2-Octylamine, and 2-Hydroxyethylaminopropylamine, Piperazine ) And triisopropanolamine (TIPA). It is preferably monoethanolamine (MEA).

The absorbent that absorbs carbon dioxide is desorbed (removed, degassed or separated) from the absorbent while the carbamate is decomposed in the regeneration tower, and the absorbent is regenerated. In the present invention, a catalyst for promoting the carbamate decomposition is used, and the catalyst Is a transition metal oxide, for example, Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O and NiO. Defect sites on the surface of the transition metal oxide can provide catalytic properties, and in the present invention, by using the position of an acid present on the surface of the transition metal oxide, for example, an unsaturated metal that can accept electron pairs When the position of Lewis acid generated by the coordination of atoms and the transition metal oxide contact with water, water molecules are adsorbed on the surface (MO _surf + H ₂ O → MO.H ₂ O _surf → MOH.OH _surf ), By converting the surface of the oxide to a hydroxyl group may act as the location of Bronsted acid. The position of Lewis acid and Brønsted acid can weaken the NC bond by directly attacking the N atom of carbamate, so that the carbon dioxide absorbed by the absorbent is stripped from the absorbent and discharged in the gas phase from the regeneration tower, and the absorbent is regenerated do.

In one embodiment of the present invention, the transition metal oxide catalyst is in one embodiment, the transition metal oxide catalyst may be added in an amount of 0.1 to 20% by weight based on the weight of the absorbent. If it is 0.1% by weight or less, the catalytic activity is insignificant, and when it is 20% by weight or more, the catalytic function may be deteriorated due to aggregation between catalysts in the absorption solution. In the carbon dioxide absorbent regeneration of the present invention, the regeneration of the absorbent is performed in a temperature range of 40 ° C to 90 ° C. When the transition metal oxide catalyst is used in an amount of less than 5% by weight based on the absorber, the required thermal energy increases, and when the amount of the catalyst used is more than 10% by weight based on the absorber, the amount of catalyst used is not very economical. Compared to a conventional monoethanol amine absorbent having a regeneration temperature of 120 ° C. or higher, the regeneration method of the present invention can reduce energy by reducing a regeneration temperature required for stripping of carbon dioxide, and can rapidly separate carbon dioxide. The carbon dioxide stripped absorbent can be reused by separating the transition metal oxide and supplying it to the absorption tower.

Hereinafter, examples are provided to help understanding of the present invention. However, the following examples are provided only for easier understanding of the present invention, and the present invention is not limited to the following examples.

Example

Example  1 Regeneration of carbon dioxide absorbent using transition metal oxide catalyst

In order to regenerate the carbon dioxide absorbent using the transition metal oxide, carbon dioxide was absorbed by using a continuous stirring-tank reactor in 100 mL of an amine compound 5M monoethanolamine (MEA, Acros) solution as an absorbent. Carbon dioxide was completely saturated, and the carbon dioxide-saturated absorbent solution was analyzed with a total organic carbon analyzer (Analytik Jena multi N / C 3100) to show 0.50 mol CO ₂ / mol MEA. In order to investigate the effect of regenerating the absorbent according to the temperature, a batch reactor connected to an oil circulator to maintain a desired temperature was used. For uniform heat distribution, a magnetic bar was used at 200 rpm to stir the solution, a thermocouple was inserted to measure the temperature of the amine solution, and condensation and recirculation of water vapor and amine solvent were performed using a condenser. The stripped CO ₂ discharged from the reactor was mixed with 50 cc / min of N2 gas, and the mixed gas was analyzed by gas chromatography (Agilent Technologies 7890A). Values were recorded in relation to time and temperature. As the absorbent regeneration catalyst, Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O, and NiO were used. 10 g of each catalyst was added to a solution of 100 mL and the experiment was performed under the same conditions. All experiments were repeated three times to confirm data reliability and reproducibility, and the average values obtained from the experiments were recorded. Experiments to investigate the effect of regenerating the MEA absorbent were performed in a set of four experiments within a temperature range of 40 ° C to 85 ° C, which is a mild temperature condition. The initial temperature of all experiments was 40 ° C and the temperature was raised at a constant rate up to four preset temperatures preset to a maximum of 85 ° C, 80 ° C, 75 ° C and 70 ° C. When the set temperature was reached, the temperature was kept constant for 2 hours. That is, a carbon dioxide absorbent regeneration experiment was performed at 40-85 ° C, 40-80 ° C, 40-75 ° C, and 40-70 ° C, and the experimental results are shown in FIGS. 1 to 5.

FIG. 1 is an FT-IR spectrum of the acid sites of Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O and NiO transition metal oxides in relation to the catalytically active positions of the transition metal oxides of the present invention. The transition metal oxide was used for acid location detection by pyridine adsorption. Transition metal oxide was introduced into a specially designed stainless steel IR cell for detection of Lewis acid location and Brønsted acid location, and pyridine gas was injected. The cells were injected until the inside reached 5 bar, and adsorbed at 100 ° C. for 2 hours. Thereafter, desorption of pyridine physically adsorbed at 150 ° C. for 15 minutes was performed. The IR cell after the pyridine adsorption and desorption reaction was connected to an infrared spectrometer, and the IR spectrum was measured. As a result, as shown in FIG. 1, all of the five catalysts have a Lewis acid position (L), and Ag ₂ O and Nb ₂ O _{5 also} have a Brønsted acid position (B). The Lewis mountain location (L) showed bands at 1420-1460 cm ^-1 and 1560-1620 cm ^-1 , and the Brønsted mountain location (B) showed bands at 1535-1540 cm ^-1 . The band around 1480 cm ^-1 is a mixture of Lewis and Brønsted mountain locations.

2 is a graph showing the desorption results of carbon dioxide according to time and temperature for each type of transition metal oxide catalyst by adding 10 g of Nb ₂ O ₅ , CuO, MnO ₂ , Ag ₂ O, and NiO catalysts to a carbon dioxide saturated absorbent solution. , (a) and (b) are temperature ranges of 40-85 ° C, (c) and (d) are temperature ranges of 40-80 ° C, (e) and (f) are temperature ranges of 40-75 ° C, ( g) is a graph of the results of absorbent regeneration tested in the temperature range of 40-70 ° C, respectively. In the case of using a catalyst, it was found that carbon dioxide stripping is performed efficiently under all conditions than the comparative example (MEA only). (A) and (b), which performed experiments in the temperature range of 40-85 ℃, showed the best carbon dioxide absorbent regeneration effect when Ag ₂ O and Nb ₂ O ₅ were used as catalysts. Compared, the total amount of desorbed CO ₂ increased by about 36 and 35%, respectively. When using a non-NiO, CuO and MnO ₂ as the catalyst was found to increase the amount of stripping of CO by about 20%. A similar amount of carbon dioxide desorption was observed in all types of catalysts at an initial temperature of 40-65 ° C, but after 65 ° C, desorption of carbon dioxide was significantly higher when Ag ₂ O and Nb ₂ O ₅ catalysts were used. This indicates that the higher the location of the Lewis acid and Brønsted acid, as shown in the IR analysis spectrum, the more the presence of a number of catalytically active sites capable of decomposing carbamate in the solution and the thermal energy added, resulting in a high efficiency carbon dioxide stripping effect.

In (c) and (d) experiments in the temperature range of 40-80 ° C., Ag ₂ O and Nb ₂ O ₅ catalysts adsorbed 48 and 46% increased carbon dioxide, respectively, than the MEA basic experiments. When NiO, CuO and MnO ₂ catalysts were used, it was found that the carbon dioxide emissions were increased by 23, 30 and 15%. The main reason for the further increase in the amount of carbon dioxide desorption by using the catalyst is not the increase in the amount of carbon dioxide desorption from the catalyst system, but the decrease in the amount of carbon dioxide desorbed from the MEA solution. This tendency is that in the MEA-only solution using only thermal energy for desorption of carbon dioxide, the desorption of carbon dioxide by heat energy alone is not sufficient under the set temperature conditions (c) and (d), which are lower than the set of (a) and (b). You can see that it is not. That is, since the desorption of carbon dioxide using a transition metal oxide catalyst is a combination of the acid concentration in the system and the thermal energy provided, due to the protonation and bonding of metal atoms to the carbamate, NC bonding is much weaker in the catalyst system, so that the removal of carbon dioxide is easier. It can be done. Although this is a lower temperature, it can be seen that the increased carbon dioxide is removed under the carbon dioxide stripping condition using the transition metal oxide of the present invention than when only heat energy was applied to the MEA.

In the same way, the temperature ranges (e) and (f) of the temperature range of 40-75 ° C showed an increase of up to 49% carbon dioxide stripping, especially Ag ₂ O and Nb ₂ O ₅ increased 42% and 49%, respectively. The amount of carbon dioxide stripping was shown. At the lowest experimental temperature (g) at 40-70 ° C, the maximum amount of CO2 stripping increased by 73%. 2 (h) is a graph showing the amount of carbon dioxide released at each temperature for each catalyst, and it can be seen that when the transition metal oxide catalyst of the present invention is used, the carbon dioxide stripping amount is higher at all temperatures than when only the MEA solvent is used. In addition, under most conditions, it showed a similar or higher stripping efficiency than that of the H-ZSM-5, a known catalyst. Regeneration of the carbon dioxide absorbent using the transition metal oxide of the present invention as a catalyst is capable of desorbing a considerable amount of carbon dioxide even at a temperature where the thermal energy is not sufficient, compared to the conventional carbon dioxide absorbent regeneration method using only thermal energy, thereby capturing and separating the existing carbon dioxide. It is believed that the amount of energy required for the recovery process can be reduced.

3 (a) to (g) are graphs showing the desorption rate over time of carbon dioxide, and are graphs consistent with FIGS. 2 (a) to (g). The desorption rate is the rate at which carbon dioxide is released from the liquid phase to the gas phase rather than the chemical reaction rate, which was calculated by comparing it with the desorption of carbon dioxide from the MEA solution. In addition to the fact that experiments with transition metal oxide catalysts emit more carbon dioxide, substantial changes in the amount of carbon dioxide desorbed from the isothermal stage to the ramp-up stage were recorded. This change was more pronounced when Ag ₂ O and Nb ₂ O ₅ were used as a catalyst, because the presence of carbamate increased due to the presence of a larger number of acid sites than other catalysts, so collision and protonation of carbamate was more possible. It is judged that the result is that the desorption rate of carbon dioxide at a low temperature is improved significantly.

Table 1 shows the temperature and time when the maximum amount of carbon dioxide was removed from the solution. a is the temperature and time recorded only during the experiment of the set of Figs. 3 (a) and (b), and b represents the amount of carbon dioxide released from the solution using all kinds of catalysts in all sets of ramp-up steps. The amount of carbon dioxide released from the MEA solution was taken as a baseline for each set. The total amount of carbon dioxide desorbed in the temperature rising step is shown in comparison with the MEA-only experiment. 3 (a) and (b), it can be seen that a solution using a transition metal oxide catalyst desorbs up to 2.53 and 2.19 times as much carbon dioxide as compared to a MEA-only experiment, in particular Ag ₂ O and Nb ₂ The results show that the absorbent regeneration performance of O ₅ is very excellent. When Ag ₂ O and Nb ₂ O ₅ were used, it was confirmed that the maximum amount of carbon dioxide was desorbed quickly for 3 to 5 minutes, and the maximum desorption amount could be performed at a temperature of 2 to 4 ° C. lower than the MEA alone test. NiO, CuO, MnO ₂ was confirmed that the removal amount of carbon dioxide in the ramp-up step increased 1.57 times, 1.45 times, and 1.26 times.

[Table 1]

3 (b) and (c), up to 3.18 times and 2.45 times more carbon dioxide was desorbed in the ramp-up step compared to the MEA alone experiment, and also 3.38 times in FIGS. 3 (d), (e) and (g). It was found that a carbon dioxide emission of 3.62 times higher was released. Significantly increased CO2 desorption rates can shorten the stripper column, especially at low temperatures, reducing process costs. In addition, it was observed that due to the high carbon dioxide desorption rate using the transition metal oxide catalyst, the pressure at the top of the reactor through which the desorbed carbon dioxide passes is twice as high as when the MEA solution is used alone. This is thought to reduce the pressure provided to discharge the stripped carbon dioxide.

The cyclic capacity of the solvent is an important factor indicating the efficiency of the solvent, and the chemical absorbent having a high circulating capacity is advantageous for the industrial field. Chemical solvents with high circulating capacity require less renewable thermal energy, ie absorbents that can be regenerated under mild temperature conditions can save cost and energy, which can be achieved by lowering lean loadings. have. Here, the repeat capacity of MEA is defined as the difference between the maximum carbon dioxide load at the start of the experiment (0.50 mol CO ₂ / mol MEA) and the minimum carbon dioxide load achieved at the end of the regeneration experiment, and was calculated using the following equation (1).

계산식 (1)

Formula (1)

The carbon dioxide absorbent regeneration process using the transition metal oxide catalyst of the present invention can be more effectively removed when only MEA is used alone, and thus high circulation capacity can be achieved. Figure 4 shows the carbon dioxide load of the lean solution obtained from the total solution at the end of the experiment. Ag ₂ O and Nb ₂ O ₅ solutions tested to 85 ° C. and 80 ° C. exhibited increased efficiency of about 32% compared to the case of regenerating the carbon dioxide absorbent using only MEA. The circulating capacity of the results of experiments at 75 ° C and 70 ° C showed an increased efficiency of about 15%. Increasing the circulating capacity means an additional cost reduction aspect of the catalytic process, and a higher circulating capacity requires a lower circulating speed, thus saving some of the capital and operating costs.

The process of using the amine-based absorbent in the carbon dioxide absorption process is a process of circulating absorption and stripping. In the absorption tower, carbon dioxide is absorbed by the absorbent in the form of carbamate, thermally stripped in the form of carbon dioxide in the regeneration tower, and recovered, and the regenerated absorbent is recycled to the absorption tower. In the case of using a carbon dioxide absorbent regeneration system using a catalyst, it is necessary to identify side effects caused by the catalyst during the absorption process. To this end, in the present invention, an experiment was conducted to determine the carbon dioxide absorption capacity of the regenerated absorbent. The results are shown in FIG. 5. The regenerated absorbent used here was a regenerated MEA in which the load of the regenerated absorbent in FIG. 4 was measured. 5 (a) shows a carbon dioxide reabsorption amount of the regenerated absorbent by performing a carbon dioxide stripping experiment using a transition metal catalyst as shown in FIG. 5 (b). A reabsorption experiment of MEA with carbon dioxide removed at a temperature of 40-85 ° C was performed. 5M MEA pure heat regeneration and 5M MEA solvent were added with 10 wt% catalyst. It is a comparison of absorption capacity.

Overall, it has been found that there are few side effects of the catalyst with respect to absorption and reabsorption of carbon dioxide in the MEA regenerated by using the catalyst. However, Ag ₂ O and CuO have a small amount of MEA and a metal complex, and it is believed that a slight decrease in the carbon dioxide absorption capacity occurred due to a decrease in the number of MEA molecules to absorb carbon dioxide. The carbon dioxide absorbent regeneration method using the transition metal catalyst of the present invention is carbon dioxide at a rapid rate even at a remarkably low 60 to 85 ° C. temperature condition compared to the conventional regeneration temperature of about 120 ° C. compared to the conventional amine absorbent regeneration method using only thermal energy. The absorbent can be regenerated. In addition, it does not damage the absorbent and retains the ability to absorb carbon dioxide when reused. This can reduce the required thermal energy and stripping time, which can represent a very good energy saving effect throughout the process.

Although the exemplary embodiments of the present application have been described in detail above, the scope of the present application is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present application defined in the following claims are also provided. It belongs to.

All technical terms used in the present invention, unless defined otherwise, are used in the sense as commonly understood by those skilled in the art in the relevant field of the present invention. The contents of all publications described by reference herein are incorporated into the present invention.

Claims (7)

Absorbing acid gas using an absorbent for removing acid gas to obtain an absorbent absorbing acid gas; And
And adding a transition metal oxide catalyst to the absorbent absorbing the acid gas to remove the acid gas to regenerate the absorbent,
The transition metal oxide is at least one selected from the group consisting of Nb ₂ O ₅ and Ag ₂ O and promotes the decomposition of carbamate in the absorbent solution for removing acid gases,
The regeneration step is performed in a temperature range of 40 ° C to 85 ° C,
The acid gas is carbon dioxide,
A method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst.
According to claim 1,
The absorbent is monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), tetraethylenepentamine (TEPA), triethylenetetramine (TETA), N -N-methyl diethanolamine (MDEA), 3-isobutoxypropylamine, Dimethylaminoethylamine, Diglycolamine (DGA), Hexylamine, 2 -Amino-2-methylpropanol (AMP, 2-Amino-2-methyl-propanol), hexamethylenediamine (HMDA), propylamine, dipropylamine, butylamine, butylamine Isobutylamine, 2-Ethylhexylamine, 4-Aminobutanol, 3-Methoxypropylamine, Allylamine, Methyldiallylamine ( Methyldiallylamine), pentylamine, isoamyl (Isoamylamin), N-Methylethylamine, 2-Octylamine, and 2-Hydroxyethylaminopropylamine, piperazine and triisopropanolamine ( triisopropanolamine (TIPA), one or more selected from the group consisting of:
A method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst.
According to claim 1,
The absorbent is monoethanolamine (MEA),
A method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst.
According to claim 1,
The transition metal oxide catalyst is added at 0.1 to 20% by weight based on the weight of the absorbent,
A method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst.
delete According to claim 1,
The method further comprises reusing the absorbent for removing the regenerated acid gas,
A method for regenerating an absorbent for removing acidic gases using a transition metal oxide catalyst.
delete

Images