Carbon dioxide recovery method using gaseous amine

Abstract

To provide a method of recovering CO2 gas from CO2 containing gas by using gaseous amine.SOLUTION: A method of recovering CO2 by using amine existing as gas at an atmospheric temperature includes: a suction step of mixing amine A(g) existing as gas and gas containing CO2 and forming an absorbent of amine and CO2 to generate CO2-amine absorbent s existing as a solid; a separation step of imparting energy to the CO2-amine absorbent to separate CO2 and amine; and an individually recovering step of individually recovering the separated CO2 and the amine.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering carbon dioxide (CO2) gas, and more particularly to a method for recovering CO2 gas by adsorbing it onto an amine. [Background technology]

[0002] Various techniques (amine processes) have been proposed that utilize the reversible CO2 adsorption properties of amines to selectively capture CO2 gas from CO2-containing gases. For example, Patent Document 1 proposes a CO2 capture device and method that brings CO2-containing flue gas into gas-liquid contact with a lean solution containing an amino group-containing compound, absorbs CO2 into the lean solution, and then electrolyzes the rich solution to separate it into the lean solution and CO2. Patent Document 2 discloses a technique for separating and capturing CO2 by contacting CO2-containing flue gas with an amine-based CO2 capture solvent and irradiating the amine-based CO2 capture solvent with light having a transmission band wavelength in the 190-450 nm range. Patent Document 3 discloses a technique for absorbing carbon dioxide from a carbon dioxide-containing gas into an aqueous solution containing 2-isopropylaminoethanol and at least one selected from the group consisting of piperazines and alkanolamines, and then heating the aqueous solution to desorb and capture the carbon dioxide. Patent Document 4 describes a solid absorbent called RNH(CH2) that can not only absorb carbon dioxide in gas with high efficiency, but also desorb carbon dioxide from the absorbed solid absorbent with high efficiency and at low temperatures, and can recover high-purity carbon dioxide. n A solid absorbent material for separating and capturing carbon dioxide is disclosed, which contains an alkanolamine represented by the formula: OH [R represents an alkyl group having 1 to 6 carbon atoms, and n=2 to 5]. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2015-199042 [Patent Document 2] Patent Publication No. 2013-519513 [Patent Document 3] International Publication 2009 / 1804 [Patent Document 4] Patent Publication No. 2012-139622 Summary of the Invention [Problem to be solved by the invention]

[0004] In previous technologies for capturing CO2 gas using amines, the amines that absorb CO2 gas were typically used in a solution or solvent (amine solution) or coated on a solid substrate (amine-supported solid). In these cases, contacting the CO2 gas with the amine solution or amine-supported solid required the transport of a gas containing the CO2 gas to be captured (CO2-containing gas) to the amine solution or amine-supported solid using a fan or other means, which required energy and configuration. Furthermore, separating CO2 and amine from the CO2 and amine adsorbent requires the application of energy such as heat or pressure. However, if CO2 is bound to the amine in the amine solution or amine-supported solid, energy must also be applied to the solution or solid substrate, resulting in reduced energy efficiency. Some amines that adsorb CO2 gas exist as gases at room temperature and transform into solids when they form an adsorbent with CO2. The CO2 and amine are then separated from the adsorbent by the application of energy. If such amines that exist as gases at room temperature (gaseous amines) are used to capture CO2 gas, the gaseous amine molecules will diffuse through space, eliminating the need for energy to transport CO2-containing gas to an amine solution or an amine-supported solid, as was previously required.Furthermore, when desorbing CO2 gas from the CO2 and amine adsorbent, no solution or solid substrate is required, so energy to be applied to them is also unnecessary, thereby improving energy efficiency.

[0005] Thus, a primary object of the present invention is to provide a method for recovering CO2 gas from a CO2-containing gas using a gaseous amine. [Means for solving the problem]

[0006] According to the present invention, the above problem is solved by a method for recovering CO2 from a gas containing CO2 gas using an amine that exists as a gas at room temperature, the method comprising: an adsorption step of mixing the amine present as a gas with a gas containing CO2 to form an adsorbent of the amine and CO2, thereby producing a CO2-amine adsorbent present as a solid; a separation step of applying energy to the CO2-amine adsorbent to separate the CO2-amine adsorbent into CO2 and amine; a separate recovery step of separately recovering the separated CO2 and the amine; This is achieved by a method comprising:

[0007] In the above configuration, the amine may be a primary amine, a secondary amine, or even a tertiary amine, as long as it is capable of adsorbing CO, exists as a gas at room temperature, and adsorbs CO to form a solid CO2-amine adsorbent. Furthermore, the amine used in the present invention may exist as a liquid or solid in a sealed storage container and vaporize when placed in a large space at room temperature (15°C or higher). More specifically, amines with a vapor pressure of 10 Pa or higher at 30°C are suitable for use. Examples of such amines include, but are not limited to, butylamine, isoindoline, and piperidine. The CO2-containing gas may be any gas containing CO2 gas to be recovered, such as air or exhaust gas.

[0008] In the adsorption step of the above method, the amine and CO2 are adsorbed by one of the reactions represented by the following reaction formulas (1) and (2). 2nd Round 1 R 2 NH+CO2→(R 1 R 2 NCOO - )·(R 1 R 2 NH2 + ) …(1) R1 R 2 R 3 N + CO2 + H2O → (HCO3 - )·(R 1 R 2 R 3 NH + ) …(2) [R 1 , R 2 , R 3 is a hydrocarbon group, an aromatic group, or hydrogen. H2O is the water in the CO2-containing gas. These reactions precipitate carbamates or bicarbonates (the right-hand side of the reaction equation), which are solid at room temperature, as CO2-amine adsorbents, allowing CO2 to be concentrated as a solid. Meanwhile, in the separation process, the precipitated CO2-amine adsorbent is separated into CO2 and amine by applying energy such as heat or pressure, allowing the amine and CO2 to be recovered separately.

[0009] According to the above configuration, when a CO2-containing gas is mixed with a gaseous amine, the gaseous amine molecules associate with CO2 molecules (gas) by diffusion to form a solid CO2-amine adsorbent. Therefore, unlike the case where an amine solution or an amine-supported solid is used, energy is not required to transport or agitate the CO2-containing gas to the amine. Furthermore, since no solution or solid substrate is present when desorbing CO2 from the CO2-amine adsorbent, no energy is required, thereby improving energy efficiency.

[0010] In the above-described embodiment of the present invention, in the adsorption step, an amine present as a gas in a sealed container is mixed with a gas containing CO2 gas, and the mixed gas may be allowed to stand under conditions that prevent desorption of CO2 adsorbed by the amine. Because the amine is also a gas, simply placing a gas containing CO2 gas together with the amine in a sealed container automatically concentrates and recovers CO2 gas as a solid CO2-amine adsorbent without stirring or other processes. In this process, the container is allowed to stand under conditions that prevent desorption of CO2 adsorbed by the amine so that the formed CO2-amine adsorbent does not reseparate into CO2 and the amine. If the temperature of the container is high, it may be appropriately cooled to achieve conditions that prevent desorption of CO2 adsorbed by the amine. The conditions that prevent desorption of CO2 adsorbed by the amine vary depending on the solid CO2-amine adsorbent formed, but are typically 50°C or less at atmospheric pressure. The mixed gas may be allowed to stand for a period of time that is typically longer than the time required for the concentration of CO2 gas in the mixed gas to become undetectable (for this purpose, a means for detecting the concentration of CO2 gas in the container may be provided).

[0011] In the method of the present invention, the CO2-amine adsorbent produced in the adsorption step may be recovered, and in the separation step, energy may be applied to the recovered CO2-amine adsorbent until it separates into CO2 gas and gaseous amine and disappears. In the present invention, the CO2-amine adsorbent is not contained in an amine solution or an amine-supported solid, but is recovered essentially as is. Therefore, once the CO2-amine adsorbent disappears in the separation step, no further energy application is required, thereby making it possible to reduce the amount of energy used as much as possible. Regarding the gaseous amine remaining in the vessel after the adsorption step, the gas in the vessel after the adsorption step may be cooled to liquefy the gaseous amine, and the amine may be recovered as a liquid.

[0012] Furthermore, in the separation step of the method of the present invention, the CO2-amine adsorbent may be separated into CO2 gas and gaseous amine. In this case, in the separate recovery step, the mixed gas of CO2 gas and gaseous amine may be cooled to liquefy the gaseous amine, thereby allowing CO2 and the amine to be recovered separately. This allows the liquefied and recovered amine to be reused for recovering CO2 gas from a gas containing CO2 gas. Meanwhile, the CO2 recovered in the separate recovery step may be appropriately treated by any method. In order to quickly recover CO2 gas and the amine separately from the mixed gas of CO2 gas and gaseous amine separated from the CO2-amine adsorbent in the separate recovery step, an inert gas flow (typically, N2 gas flow) or air flow toward a condenser that liquefies the gaseous amine may be introduced into a vessel that separates the CO2-amine adsorbent into CO2 gas and gaseous amine, thereby transporting the mixed gas of CO2 gas and gaseous amine to the condenser. In this case, the flow rate of the inert gas or air is preferably adjusted so that the gaseous amine can be liquefied in the cooler and the CO2 gas and the gaseous amine are not re-adsorbed. [Effects of the Invention]

[0013] Thus, in the method of the present invention, when recovering CO2 gas from a CO2-containing gas, a gaseous amine is used instead of an amine dissolved in a solution or an amine supported on a solid, and the amine molecules and CO2 gas associate by diffusion in a state where the gaseous amine is mixed with the CO2-containing gas, thereby precipitating a solid CO2-amine adsorbent. This configuration eliminates the need for energy to transport the CO2-containing gas to the amine solution or amine-supported solid in the adsorption step, and energy to be applied to the solution or solid substrate when desorbing CO2 gas from the CO2-amine adsorbent in the separation step, as in the conventional method, thereby improving energy efficiency.

[0014] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1(A) is a schematic diagram of the adsorption process in the method for recovering CO2 using gaseous amines according to this embodiment, and FIG. 1(B) is a schematic diagram of the separation process and individual recovery process in the method for recovering CO2 using gaseous amines according to this embodiment. [Figure 2] Figures 2(A) and (B) are schematic diagrams of the experimental process showing the reduction of CO2 gas in air in the presence of gaseous amine in a sealed container. Figure 1(C) is a graph showing the time change in the amount (moles) of CO2 gas in air (simulated air) in the presence of gaseous amine in a sealed container (for reference, time changes in the absence of amine and in the presence of liquid amine are also shown). [Figure 3] FIG. 3 is a photograph of the liquefied amine recovered by the separation step and the individual recovery step according to this embodiment. [Explanation of symbols]

[0016] 1...container (adsorption process), 2...container (separation process), 2a...heater, 3...cooler, 4...liquid amine recovery container, 5...CO2 recovery container (bag), 10...almost sealed container, 12...CO2 concentration meter, 14...petri dish, 16...lid, A(g)...gaseous amine, A(l)...liquid amine s...CO2-amine adsorbent (carbamate or bicarbonate), W(g)...CO2-containing gas, P(g)...gas other than CO2 BEST MODE FOR CARRYING OUT THE INVENTION

[0017] The present invention will now be described in detail with reference to some preferred embodiments thereof with reference to the accompanying drawings, in which like reference numerals indicate like parts.

[0018] CO 2 Overview of gas recovery methods In the method for recovering CO2 gas using gaseous amine according to this embodiment, generally speaking, the following steps are carried out in order: an adsorption step in which a gas containing the CO2 gas to be recovered (CO2-containing gas) is mixed with the gaseous amine to precipitate the CO2 gas as a solid CO2-amine adsorbent; a separation step in which energy such as heat or pressure is applied to the resulting solid CO2-amine adsorbent to decompose the CO2-amine adsorbent into CO2 gas and gaseous amine; and an individual recovery step in which the CO2 gas and gaseous amine obtained in the separation step are separately recovered. Each step will be described in detail below.

[0019] Adsorption process In the adsorption process of this embodiment, as shown in FIG. 1(A), a CO2-containing gas W(g) containing CO2 gas and other components P(g) and a gaseous amine A(g) are introduced into a vessel 1 at room temperature by any method. Because both the CO2 gas and the gaseous amine are gases, they automatically mix and associate through diffusion. As a result, CO2 molecules bond with amine molecules through the reaction represented by reaction formula (1) or (2) above, producing a CO2-amine adsorbent, which is then precipitated as a solid s in the vessel. As a result, the CO2 dispersed as a gas is concentrated in the solid CO2-amine adsorbent.

[0020] In the above adsorption process, the CO2-containing gas may be any gas containing CO2 gas to be recovered, such as air or exhaust gas. Experiments have shown that if the CO2 gas concentration in the CO2-containing gas is about 100 ppm or more, the method of this embodiment can recover CO2 gas. Note that the CO2 gas concentration in normal air is about 400 ppm, so the method of this embodiment can also be used to recover CO2 gas from air.

[0021] On the other hand, the amine used in this embodiment may be any of primary amines, secondary amines, and tertiary amines that can exist as a gas at room temperature (15°C to 35°C). (In the case of tertiary amines, moisture in the gas is utilized. Note that moisture may be actively added to the container.) More specifically, since any amine with a vapor pressure of 10 [Pa] or more at 30°C can exist as a gas, such an amine may be selected in this embodiment. Furthermore, if the amine is a liquid A(l) in the storage container and vaporizes when placed in a large space at room temperature, handling will be easier. Furthermore, since it is preferable that the amine can be recovered in a liquefied state in the subsequent separation step and individual recovery step, an amine that liquefies at the temperature of a water-cooled condenser (approximately 1 to 8°C) is preferably selected. Specifically, butylamine, isoindoline, piperidine, etc. are advantageously used.

[0022] For the adsorption step, either the CO2-containing gas or the gaseous amine can be introduced into vessel 1 first. To minimize leakage of the gaseous amine, one possible approach is to place the amine in a liquid state in a petri dish with a lid in an amount sufficient to prevent vaporization, and then place the liquid in vessel 1. After the CO2-containing gas is introduced into vessel 1, the lid of the petri dish is removed and the amine is vaporized, thereby diffusing the amine within vessel 1. In the adsorption reaction between the amine and CO2, the amine and CO2 form a CO2-amine adsorbent at a molar ratio of 2:1. Therefore, the amount of amine introduced is preferably at least twice the molar ratio of the CO2 gas. This theoretically allows substantially all of the CO2 gas in vessel 1 to be recovered within the solid CO2-amine adsorbent.

[0023] After the CO2-containing gas and gaseous amine are introduced into vessel 1, vessel 1 is left stationary for a time sufficient for the CO2 gas and gaseous amine in vessel 1 to precipitate as a CO2-amine adsorbent. The specific stationary time may be determined experimentally, or, if a CO2 concentration sensor (not shown) is provided in vessel 1, it may be the time until the sensor's reading no longer decreases. In this regard, the adsorption reaction between amine and CO2 is a reversible reaction. If the temperature inside vessel 1 is high, a reaction in which the CO2-amine adsorbent decomposes into amine and CO2 also occurs. Therefore, vessel 1 is left stationary under conditions that do not cause such a decomposition reaction (conditions under which CO2 adsorbed by the amine does not desorb). The specific conditions are determined depending on the characteristics of the amine used. Typically, vessel 1 is preferably kept at atmospheric pressure and at a temperature of 50°C or less. For this purpose, a mechanism (not shown) for cooling vessel 1 may be provided as appropriate. For example, when a heat exchange system is used as the cooling mechanism, the heat recovered in vessel 1 may be used as energy to be provided to the CO2-amine adsorbent in the separation process described below. After the CO2 gas is adsorbed, the gaseous amine remaining in the container 1 may be recovered by any method (for example, the gaseous amine can be recovered by liquefying it by cooling it using a Liebig condenser, which will be described later).

[0024] Thus, in the above adsorption process, as already mentioned, CO2 gas molecules are mixed with gaseous amine molecules. Since the association occurs through diffusion, the energy required to transport CO2 gas to the amine solution or amine-supported solid is no longer required, resulting in energy savings. Furthermore, CO2 is concentrated and recovered as a solid CO2-amine adsorbent, so it can be obtained in a more highly concentrated state than when recovered in an amine solution or amine-supported solid.

[0025] Separation process and individual collection process In the method of this embodiment, the CO2-amine adsorbent obtained in the adsorption step is recovered and then separated into amine and CO2 by applying energy such as heat or pressure, and the separated amine and CO2 may be recovered separately.

[0026] More specifically, as shown in Fig. 1(B), in one embodiment of the separation step, the CO2-amine adsorbent s is placed in a vessel 2 and heated by a heater 2a or the like to provide energy, thereby separating the CO2-amine adsorbent s into CO2 gas and gaseous amines. Here, energy is provided to the CO2-amine adsorbent itself, rather than to a solution containing the CO2-amine adsorbent or a solid support, as in the past, thereby enabling energy savings. Furthermore, since the CO2 gas is generated in a concentrated state in the solid CO2-amine adsorbent, the CO2 gas concentration in vessel 2 is significantly higher than when the CO2-containing gas was introduced into vessel 1.

[0027] Thereafter, the CO2 gas and gaseous amine generated from the CO2-amine adsorbent in vessel 2 are sent to cooler 3. As shown in the figure, a mechanism for introducing an inert gas flow such as N2 gas or an air flow into vessel 2 to guide the mixed gas of CO2 gas and gaseous amine to cooler 3 may be provided. In cooler 3, the gaseous amine is cooled and liquefied, and the liquefied amine A(l) is collected in a liquid state by a gas-liquid separator 4 of any type, while the CO2 gas may be recovered in a gaseous state in a container (bag) 5 or the like. As shown in the figure, cooler 3 may be a Liebig condenser or the like that cools the mixed gas using a refrigerant C such as cold water. Furthermore, as described above, when an inert gas stream or air stream is introduced to guide the mixed gas of CO2 gas and gaseous amine into the condenser 3, the flow rate of the inert gas stream or air stream is adjusted so that the gaseous amine is liquefied without being adsorbed with CO2 gas, lower than the flow rate that pushes the gaseous amine out of the condenser 3 before it is liquefied in the condenser 3, but higher than the flow rate that re-adsorbs the CO2 gas and the gaseous amine. As a specific example, the flow rate of the inert gas stream or air stream may be such that, when 1 g of the CO2-amine adsorbent is placed in a 300 ml container and heated to about 100°C, the gas in the container can be replaced in about 1 minute.

[0028] Experimental example The effectiveness of this embodiment was confirmed by the following experimental examples. It should be understood that the following experimental examples are merely illustrative of the effectiveness of this embodiment and do not limit the scope of the present invention.

[0029] (1) Adsorption process According to the teachings of this embodiment, CO2-containing gas and gaseous amine were mixed in a sealed container using the following procedure, and it was confirmed that the CO2 gas concentration decreased. The CO2-containing gas used was simulated air, which was prepared by mixing CO2 gas with N2 gas to a concentration of 4000 ppm or 400 ppm. In the experiment, as shown in Figure 2(A), a 3 cm diameter petri dish 14 with a lid containing liquid amine A(l) in an amount equivalent to 0.00232 mol of nitrogen was placed in a 5 liter container 10, and simulated air was introduced into the container. Then, as shown in Figure 2(B), the lid 16 of the petri dish 14 was removed, and the amine was vaporized (A(g)). In the case of vaporizing liquid amine, the liquid disappeared due to evaporation within a few seconds. The CO2 concentration in the container 10 was then measured using a sensor 12.

[0030] Figure 2(C) shows the change in the amount (mol) of CO2 gas over time when the above adsorption process was carried out using various amines (the amount (mol) of CO2 was calculated as 22.4 mol per liter). In the same figure, the amount of CO2 vaporized in the vessel was 22.4 mol, and the amount of CO2 vaporized in the vessel was 22.4 mol. 11The graph shows the results for the cases where amines such as butylamine (DEA) and isoindoline (N) were placed in the container, the cases where non-vaporizable liquid amines PEI (polyethylamine) and DEA (diethanolamine) were placed in the container, and the case where no amine was placed (con.). (The results shown are for the case where 4000 ppm of CO2 gas was used as simulated air.) As can be seen from the graph, in the case of isoindoline and butylamine, which are vaporizable amines, a significant decrease in CO2 gas concentration was observed over time compared to the cases where non-vaporizable amines were placed in the container and the case where no amine was placed in the container. (In the case of butylamine, the CO2 gas amount initially decreased and then increased because the excess solidified and then settled into an equilibrium state.) Furthermore, although not shown, a solid that is thought to be a CO2-amine adsorbent precipitated in the container. These results demonstrate that when CO2-containing gas and gaseous amine are mixed according to the teachings of this embodiment, CO2 gas can be adsorbed by the amine and recovered as a solid without requiring any special energy for stirring or the like in the container.

[0031] (2) Separation process and individual collection process The solid (CO2-amine adsorbent) precipitated during the adsorption process was collected in a small container and subjected to heat as energy to confirm that CO2 gas and amine could be separately collected. The solid obtained using 1 g (1.35 mol) of butylamine was used as the CO2-amine adsorbent. It was collected in a 300 ml container and heated to approximately 100 °C using a heater. As shown in Figure 1(B), the container was configured so that N2 gas was introduced through one port and the gas inside the container was sent through another port to a 30 cm Liebig condenser with a cooling temperature set at 5 °C. The liquefied material in the Liebig condenser was collected in an Erlenmeyer flask, while the gas that passed through the Liebig condenser was collected using a gas bag.

[0032] As a result, a liquid L, which is believed to be butylamine, was collected in the Erlenmeyer flask, as shown in Figure 3. The CO2 concentration of the gas that passed through the Liebig condenser and was collected in the gas bag was as shown in Table 1 below. [Table 1] In the table above, "N2 gas flow rate" refers to the flow rate of N2 gas introduced into the container, and "gas bag volume" refers to the volume of the gas bag used to collect the gas that passed through the Liebig condenser. The gas that passed through the Liebig condenser was collected at the time indicated in "Sample Date." "Before heating" refers to the volume of gas collected in the gas bag when N2 gas was introduced without heating the heater. "Heating Start 1" and "Heating Start 2" refer to the first and subsequent volumes of gas collected in the gas bag when heating the heater was started while introducing N2 gas. "Control" refers to the results for argon gas collected from a gas cylinder through factory piping.

[0033] Referring to Table 1, it was observed that in all cases where a CO2-amine adsorbent was placed in the container, the CO2 concentration of the gas that passed through the Liebig condenser and was collected in the gas bag was significantly higher, even in the control case. (The reason the CO2 concentration "before heating" was higher in the case of the N2 gas flow rate was because the N2 gas hit the solid directly. In other words, this suggests that CO2 desorbs not only through heat as an energy source, but also through mechanical effects such as pressure.) This demonstrated that CO2 gas can be collected at high concentrations from the CO2-amine adsorbent using the above process.

[0034] Thus, according to the method of this embodiment, it is possible to selectively capture CO2 gas in air, exhaust gas, etc. by using gaseous amine. It is expected that the configuration according to the teachings of this embodiment can be used to capture CO2 gas in a variety of situations.

[0035] The above description has been made in relation to the embodiments of the present invention, but it will be apparent that many modifications and changes will be readily apparent to those skilled in the art, and the present invention is not limited to the above-described exemplary embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. CO using amines that exist as gases at room temperature ２ from gas containing CO ２ A method for recovering Amine and CO present as gases ２ and mixing the gas containing the amine and CO ２ CO2 exists as a solid adsorbent ２ - an adsorption step to produce an amine adsorbent; The CO ２ - Energy is applied to the amine adsorbent to ２ -amine adsorbent CO ２ and a separation step of separating the amine. The separated CO ２ and a separate recovery step of separately recovering the amine. A method comprising:

2. 2. The method of claim 1, wherein the adsorption step comprises adsorbing the amine and the CO 2 gas in a sealed vessel. ２ and mixing the mixed gas with a gas containing CO2 adsorbed by the amine. ２ A method of leaving the material to stand under conditions that do not cause it to be desorbed.

3. 2. The method of claim 1, wherein in the adsorption step, the produced CO ２ - recovering the amine adsorbent, and in the separation step, ２ -Amine adsorbent CO ２ The method of providing the energy until it dissociates into a gas and a gaseous amine and disappears.

4. 2. The method of claim 1, wherein in the separation step, ２ -Amine adsorbent CO ２ The gas and the gaseous amine are separated, and in the separate recovery step, ２ The mixture of gas and gaseous amine is cooled to liquefy the gaseous amine, thereby ２ and the amine are separately recovered.

5. 5. The method of claim 4, wherein in the separate recovery step, ２ -amine adsorbent CO ２ The CO 2 is separated into a gas and a gaseous amine by introducing a stream of inert gas or air into a vessel which separates the gas and the gaseous amine and then into a condenser which liquefies the gaseous amine. ２ A method of conveying a mixture of gas and gaseous amine to the cooler.

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