An absorption-transfer system for flue gas carbon dioxide capture

Abstract

The application discloses an absorption-delivery system for flue gas carbon dioxide capture, which is composed of a hydrophobic high-boiling point hydrophilic absorbent with a very high absorption rate and a high cycle load, and is used for absorbing and delivering carbon dioxide; the absorption-delivery process is that the hydrophobic absorbent directly contacts the flue gas, quickly absorbs CO2, and then reacts to generate a product, then the hydrophobic absorbent contacts the hydrophilic absorbent, the CO2 molecules in the product are delivered to the hydrophilic absorbent by using the strong interaction between the hydrophilic absorbent and the CO2 molecules or the strong proton acceptor characteristics of the hydrophilic absorbent, so that the hydrophobic absorbent is released and reduced, and then contacts the flue gas again to absorb CO2, thereby realizing the recycling of the absorbent. Compared with traditional hydrophilic absorbents, the CO2 absorption-delivery system has the advantages of a fast absorption rate, a low regeneration energy consumption and long-term stability.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, and more specifically to an absorption-transfer system for capturing carbon dioxide from flue gas. Background Technology

[0002] The significant increase in atmospheric carbon dioxide (CO2) is a major cause of global warming and climate change. Carbon dioxide capture, utilization, and storage (CCUS) technology is widely considered an important means to reduce CO2 emissions, ensure energy security, and achieve sustainable development in the future. Due to its reliability, mature technology, and ability to handle large quantities of gas, chemical absorption has become the most widely used CO2 capture technology.

[0003] Organic amine chemical absorption has become the most commonly used CO2 capture technology. For example, an aqueous solution of ethanolamine (MEA) with a mass fraction of 20%–30% has been applied to CO2 capture systems in the flue gas of million-ton / year coal-fired power plants. However, due to its high water content (70%–80%), the 20%–30% MEA aqueous solution has a low CO2 concentration in the liquid phase, resulting in a large amount of heat being consumed during CO2 desorption for water evaporation and heating, leading to high energy consumption in the system. Generally, absorbents with fast absorption rates have higher heats of reaction, i.e., higher heats of desorption. Correspondingly, absorbents composed of N-methyldiethanolamine have extremely high absorption capacity and low heats of desorption; however, the absorption rate of N-methyldiethanolamine is extremely slow. To achieve a high capture rate, the CO2 absorption tower needs to be large, resulting in high system investment costs and limiting the large-scale application of this technology. Therefore, traditional chemical absorbents cannot simultaneously possess the advantages of both fast absorption rate and low heat of desorption.

[0004] Chinese invention patent CN104958998A, published on October 7, 2015, discloses a CO2 capture system with rich liquid phase separation and tearing regeneration. This process system takes advantage of the large CO2 circulation capacity of aqueous phase, thereby reducing regeneration energy consumption, but the CO2 absorption rate of this process system is relatively slow.

[0005] Chinese invention patent CN113101786A, published on July 13, 2021, discloses a flue gas carbon dioxide capture system and method based on an organic solvent absorption-extraction regeneration cycle. This process uses a fast-absorbing aqueous solution to absorb CO2, and then regenerates this aqueous solution with an extractant, demonstrating that the two-phase absorption-extraction process is beneficial for increasing the absorption rate and reducing regeneration energy consumption. The organic solvent absorption-extraction regeneration cycle system described in this invention patent uses a diamine-type phase-change absorbent. The phase separation point of this type of absorbent is difficult to control, and the organic solvent N,N-diethylethanolamine (DEEA) is hygroscopic. As the number of absorption cycles increases, the absorbent will be unable to continue the absorption-extraction regeneration process. Furthermore, this type of absorbent continuously introduces moisture into the extractant during absorption, leading to increased energy consumption from water evaporation during the extractant regeneration process.

[0006] Therefore, there is an urgent need to develop a stable absorption-transfer system based on a fast absorption rate that can reduce desorption heat and water evaporation energy consumption. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an absorption-transfer system for capturing carbon dioxide in flue gas. This absorption-transfer system utilizes two types of absorbents with significant differences in hydrophilicity and hydrophobicity. Before absorbing CO2, the absorbents are in a liquid-liquid two-phase state. After absorbing CO2, they form one of the following: a liquid-liquid two-phase state, a liquid-liquid-liquid three-phase state, or a liquid-liquid-solid three-phase state. This avoids the problem of difficult-to-control phase separation point of diamine-type phase change absorbents.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: An absorption-transfer system for capturing carbon dioxide in flue gas is a ternary or higher mixture consisting of a hydrophobic absorbent with an extremely high absorption rate, a high-boiling-point hydrophilic absorbent with a high circulating load, and water.

[0009] The hydrophobic absorbent is composed of one or more of the following as solutes: n-butylamine, n-hexylamine, cyclohexylamine, 1,6-hexanediamine, n-octylamine, isophoronediamine, 1,3-cyclohexanedimethylamine, triethylamine, and N,N-dimethylcyclohexylamine, and one or more of the following as solvents: n-butanol, isobutanol, n-octanol, ethyl dodecanoate, and tributyl phosphate.

[0010] The hydrophilic absorbent is composed of one or more of the following as solutes: N-methyldiethanolamine, 3-amino-1,2-propanediol, 3-dimethylamino-1-propanol, 1,3-diamino-2-propanol, N-methylpiperazine, N-ethylpiperazine, triethylenediamine, diethylenetriamine, 1,4-butanediamine, hydroxyethylethylenediamine, piperazine, 3-dimethylaminopropylamine, 2-(methylamino)ethanol, 2-amino-2-methyl-1-propanol, 1-(2-aminoethyl)piperazine, and 1,3-cyclohexanedimethylamine, and two or more of the following as solvents: glycerol, sulfolane, N-methylformamide, N,N-dimethylacetamide, and water.

[0011] The flue gas comes into direct contact only with the hydrophobic absorbent.

[0012] The CO2 molecule transfer process is as follows: (1) By utilizing the interaction force between CO2 molecules and hydrophilic absorbents > the interaction force between CO2 molecules and hydrophobic absorbents, CO2 molecules are transferred from hydrophobic absorbents to hydrophilic absorbents, thereby regenerating the hydrophobic absorbents. (2) By utilizing the difference in reaction pathways between CO2 molecules and hydrophobic and hydrophilic absorbents, as well as the strong proton acceptor properties of hydrophilic absorbents, CO2 molecules can be transferred from hydrophobic absorbents to hydrophilic absorbents, thereby regenerating the hydrophobic absorbents.

[0013] The hydrophobic absorbent has the characteristics of high absorption rate and hydrophobicity, while the hydrophilic absorbent has the characteristics of high cyclic load, high boiling point, and hydrophilicity.

[0014] The hydrophobic absorbent rapidly absorbs CO2 and generates products upon contact with flue gas, then transfers these products to a hydrophilic absorbent with a larger circulation capacity. This allows the hydrophobic absorbent to be released from the products and reused in the rapid CO2 absorption process in the flue gas. The hydrophilic absorbent is then sent to the desorption unit for desorption and reuse.

[0015] In the ternary or higher hybrid system, the volume fraction of carbon dioxide absorbed from the flue gas is 10% to 20%.

[0016] Preferably, the mass ratio of the hydrophobic absorbent to the hydrophilic absorbent during the carbon dioxide absorption process is 1:1 to 5, the concentration of the hydrophobic absorbent is 2 to 5 mol / L, and the concentration of the hydrophilic absorbent is 2 to 5 mol / L.

[0017] Preferably, the absorption temperature of the carbon dioxide is 30~60℃, and the static absorption rate of the hydrophobic absorbent is 60~200×10⁻⁶. -3 mol s -1 m2 It is 10 to 15 times higher than that of a 30% ethanolamine aqueous solution, and the absorption load of the hydrophilic absorbent is 1.2 to 2.0 mol CO2 / mol hydrophilic absorbent.

[0018] Preferably, the hydrophilic absorbent is regenerated by thermal desorption at a temperature of 100–110°C for 120 min, with a regeneration efficiency of 80%–94%.

[0019] In the absorption-transfer system, the hydrophobic absorbent directly contacts the flue gas and rapidly absorbs CO2, reacting to form products. Then, the hydrophobic absorbent contacts a hydrophilic absorbent. Utilizing the strong interaction between the hydrophilic absorbent and the CO2 molecules in the products, or the strong proton acceptor properties of the hydrophilic absorbent, the CO2 molecules in the products are transferred to the hydrophilic absorbent. This causes the hydrophobic absorbent to release and reduce, then re-contact the flue gas and absorb CO2. 2，实现 Recycling of absorbents.

[0020] The beneficial effects of this invention are as follows: In the CO2 absorption process of this invention, the flue gas comes into direct contact with the hydrophobic absorbent, rather than the hydrophilic absorbent. Due to the hydrophobicity of the absorbent, water from the flue gas is prevented from being carried into it, thus blocking the path of water into the absorbent. Compared to traditional hydrophilic absorbents, this invention prevents water from the flue gas from entering the hydrophilic absorbent to be desorbed, significantly reducing the energy consumption for water evaporation during absorbent regeneration. The CO2 absorption-transfer method proposed in this invention combines the advantages of fast absorption rate, low regeneration energy consumption, and long-term stability. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] Example 1 This embodiment provides an absorption-transfer system for capturing carbon dioxide in flue gas, which is a multi-component mixed system consisting of a 3 mol / L hexylamine solution (hydrophobic absorbent) with n-octanol as the solvent and an aqueous solution of 4 mol / L N-methyldiethanolamine + 1 mol / L diethylenetriamine (hydrophilic absorbent).

[0023] Pour 50g of hydrophobic absorbent into a bubble absorption bottle, and pour 60g of hydrophilic absorbent into the absorption bottle and stir. Place both in a 30℃ water bath and keep them at a constant temperature. Introduce 20% CO2 into the hydrophobic absorption bottle to start the absorption test. Use a liquid pump to transfer the hydrophobic absorbent to the absorption bottle containing the hydrophilic absorbent for CO2 transfer until the hydrophilic absorbent reaches saturation. After saturation, thermally desorb the hydrophilic absorbent at 100℃ for 120 min.

[0024] During the absorption process, the absorption rate is 15 times that of a 30% MEA aqueous solution, the hydrophilic absorbent cyclic load is 1.6 mol CO2 / mol hydrophilic absorbent, and the regeneration energy consumption is as high as 2.0 GJ / tCO2.

[0025] Example 2 This embodiment provides an absorption-transfer system for capturing carbon dioxide in flue gas, which is a binary mixture consisting of a 2 mol / L n-hexylamine + 1 mol / L N,N-dimethylcyclohexylamine solution (hydrophobic absorbent) and a 4 mol / L N-methyldiethanolamine + 1 mol / L 3-dimethylamino-1-propanol aqueous solution (hydrophilic absorbent).

[0026] Pour 50 g of hydrophobic absorbent into a bubble absorption bottle and 60 g of hydrophilic absorbent into the absorption bottle and stir. Place both in a 30°C water bath and keep them at a constant temperature. Introduce 15% CO2 into the hydrophobic absorption bottle to start the absorption test. Use a liquid pump to transfer the hydrophobic absorbent to the absorption bottle containing the hydrophilic absorbent for CO2 transfer until the hydrophilic absorbent reaches saturation. After saturation, thermally desorb the hydrophilic absorbent at 100°C for 120 min.

[0027] During the absorption process, the absorption rate is 12 times that of a 30% MEA aqueous solution, the hydrophilic absorbent cyclic load is 1.2 mol CO2 / mol hydrophilic absorbent, and the regeneration energy consumption is as high as 2.1 GJ / tCO2.

[0028] Example 3 This embodiment provides an absorption-transfer system for capturing carbon dioxide in flue gas, which is a binary mixture consisting of a solution of 3 mol / L n-hexylamine + 1 mol / L N,N-diisopropylethanolamine (hydrophobic absorbent) in n-octanol and an aqueous solution of 3 mol / L N-methyldiethanolamine + 1 mol / L N-ethylpiperazine + 1 mol / L triethylenetetramine (hydrophilic absorbent).

[0029] Pour 50 g of hydrophobic absorbent into a bubble absorption bottle and 60 g of hydrophilic absorbent into the absorption bottle and stir. Place both in a 30°C water bath and keep them at a constant temperature. Introduce 15% CO2 into the hydrophobic absorption bottle to start the absorption test. Use a liquid pump to transfer the hydrophobic absorbent to the absorption bottle containing the hydrophilic absorbent for CO2 transfer until the hydrophilic absorbent reaches saturation. After saturation, thermally desorb the hydrophilic absorbent at 100°C for 120 min.

[0030] During the absorption process, the absorption rate is 10 times that of a 30% MEA aqueous solution; the cyclic load of the hydrophilic absorbent is 1.9 mol CO2 / mol hydrophilic absorbent, and the regeneration energy consumption is as high as 1.9 GJ / tCO2.

Claims

1. An absorption-transfer system for capturing carbon dioxide in flue gas, characterized in that: A ternary or higher mixture consisting of hydrophobic absorbents, hydrophilic absorbents, and water; The hydrophobic absorbent is composed of one or more of the following as solutes: n-butylamine, n-hexylamine, cyclohexylamine, 1,6-hexanediamine, n-octylamine, isophoronediamine, 1,3-cyclohexanedimethylamine, triethylamine, and N,N-dimethylcyclohexylamine, and one or more of the following as solvents: n-butanol, isobutanol, n-octanol, ethyl dodecanoate, and tributyl phosphate. The hydrophilic absorbent is composed of one or more of the following as solutes: N-methyldiethanolamine, 3-amino-1,2-propanediol, 3-dimethylamino-1-propanol, 1,3-diamino-2-propanol, N-methylpiperazine, N-ethylpiperazine, triethylenediamine, diethylenetriamine, 1,4-butanediamine, hydroxyethylethylenediamine, piperazine, 3-dimethylaminopropylamine, 2-(methylamino)ethanol, 2-amino-2-methyl-1-propanol, 1-(2-aminoethyl)piperazine, and 1,3-cyclohexanedimethylamine, and two or more of the following as solvents: glycerol, sulfolane, N-methylformamide, N,N-dimethylacetamide, and water.

2. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 1, characterized in that: In the absorption-transfer system, the hydrophobic absorbent and the hydrophilic absorbent constitute a liquid-liquid two-phase absorbent. After absorbing CO2, the liquid-liquid two-phase absorbent forms one of the following: liquid-liquid two-phase, liquid-solid two-phase, liquid-liquid-liquid three-phase, or liquid-liquid-solid three-phase. The transfer of CO2 molecules between the hydrophobic and hydrophilic absorbents is achieved by utilizing the differences in interaction forces or reaction pathways between CO2 molecules and the hydrophilic and hydrophobic absorbents.

3. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 2, characterized in that, The CO2 molecule transfer process utilizes the fact that the interaction force between CO2 molecules and the hydrophilic absorbent is greater than the interaction force between CO2 molecules and the hydrophobic absorbent, thereby enabling CO2 molecules to be transferred from the hydrophobic absorbent to the hydrophilic absorbent, and thus regenerating the hydrophobic absorbent.

4. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 2, characterized in that, The CO2 molecule transfer process utilizes the differences in reaction pathways between CO2 molecules and hydrophobic and hydrophilic absorbents, as well as the strong proton acceptor properties of hydrophilic absorbents, to transfer CO2 molecules from hydrophobic absorbents to hydrophilic absorbents, thereby regenerating the hydrophobic absorbents.

5. The absorption-transfer system for capturing carbon dioxide in flue gas according to any one of claims 2-4, characterized in that, During the CO2 molecule transfer process, the flue gas only comes into direct contact with the hydrophobic absorbent.

6. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 1, characterized in that, In the ternary or higher hybrid system, the volume fraction of carbon dioxide absorbed from the flue gas is 10% to 20%.

7. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 1, characterized in that, The mass ratio of the hydrophobic absorbent to the hydrophilic absorbent in the carbon dioxide absorption process is 1:1~5, the concentration of the hydrophobic absorbent is 2~5 mol / L, and the concentration of the hydrophilic absorbent is 2~5 mol / L.

8. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 1, characterized in that, The absorption temperature of the carbon dioxide is 30~60℃, and the static absorption rate of the hydrophobic absorbent is 60~200×10⁻⁶. -3 mol s -1 m 2 The absorption load of the hydrophilic absorbent is 1.2~2.0 mol CO2 / mol hydrophilic absorbent.

9. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 1, characterized in that, The hydrophilic absorbent is regenerated by thermal desorption at a temperature of 100-110°C for 120 minutes, with a regeneration efficiency of 80%-94%.

10. The absorption-transfer system for capturing carbon dioxide in flue gas according to claim 1, characterized in that, In the absorption-transfer system, the hydrophobic absorbent directly contacts the flue gas and rapidly absorbs CO2, then reacts to generate products. The hydrophobic absorbent then contacts a hydrophilic absorbent, utilizing the strong interaction between the hydrophilic absorbent and the CO2 molecules in the products, or the strong proton acceptor properties of the hydrophilic absorbent, to transfer the CO2 molecules in the products to the hydrophilic absorbent. This causes the hydrophobic absorbent to release and reduce, and then contact the flue gas again to absorb CO2, thus achieving the recycling of the absorbent.