Highly efficient ternary liquid-liquid phase change absorbent for carbon dioxide capture

Abstract

This invention discloses a highly efficient ternary liquid-liquid phase change absorbent for capturing carbon dioxide, relating to the field of carbon dioxide capture, utilization, and storage technology. The solution comprises a main absorbent, an amine absorption aid, a phase separation promoter, and water. The molar concentration per liter of solution is: main absorbent: 2M-4M; absorption aid: 1M-2M; phase separation promoter: 5M. During CO2 absorption, the phase change absorbent provided by this invention, under the action of the phase separation promoter, gradually separates into an organic amine-rich liquid phase and a physical solvent-poor liquid phase due to the salting-out effect as CO2 absorption accumulates. The rich liquid phase is the upper layer, accounting for 45%-60% of the volume. At absorption phase equilibrium, the CO2 occupancy of the rich liquid phase is consistently above 92%, demonstrating good absorption performance. During regeneration, the desorption rate can reach approximately 90%, and desorption energy consumption can be reduced by more than 50%, fully demonstrating the excellent CO2 capture performance of the solvent described in this invention.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture, utilization and storage technology, and more specifically to a highly efficient ternary liquid-liquid phase change absorbent for capturing carbon dioxide. Background Technology

[0002] Carbon dioxide capture and storage (CCS) has received widespread attention and research as an important means of mitigating climate change. Among them, chemical absorption has attracted much attention due to its great potential. Compared with other methods, chemical absorption has advantages such as higher carbon dioxide absorption rate, relatively mature and reliable equipment technology, and wide application in industrial fields.

[0003] Traditional chemical absorption methods utilize one or more organic amine absorbents to capture carbon dioxide from flue gas, while simultaneously regenerating and recycling the solution through a desorption process. However, the absorbent recovery process requires significant energy to heat and evaporate moisture, and organic amines react with carbon dioxide and water to form bicarbonates, which not only reduces absorption efficiency but also increases energy consumption in subsequent absorbent regeneration. In recent years, phase change absorption solvents have become a research hotspot in carbon dioxide capture due to their significant advantage in reducing absorbent regeneration energy consumption. Compared to traditional MEA processes, phase change absorption solvent regeneration only requires feeding a carbon dioxide-rich liquid phase into the desorption tower, resulting in lower regeneration energy consumption. Process evaluation has shown that this type of phase change absorption process can save more than 50% of energy costs. Using phase change absorbents not only effectively solves the problem of excessive energy consumption during absorbent regeneration but also helps improve the efficiency of carbon dioxide absorption, bringing a new research perspective to the field of carbon capture.

[0004] In existing research, researchers have used organic amine absorbents as a base and experimentally screened solvents with phase change capabilities, such as ionic liquids, alcohols, ethers, and other physical solvents, to replace water as phase separation promoters. These solvents are then compounded in appropriate proportions, achieving significant results in this direction. However, compounding a single amine with a phase separation agent cannot effectively balance the requirements of high absorption rate, high absorption capacity, high desorption rate, and low energy consumption. Therefore, further optimization of the absorption solvent is needed.

[0005] Therefore, it is necessary to propose a highly efficient ternary liquid-liquid phase change absorbent for capturing carbon dioxide to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a ternary liquid-liquid phase change absorbent with low energy consumption and good carbon dioxide capture performance.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0008] A highly efficient ternary liquid-liquid phase change absorbent for capturing carbon dioxide, wherein the solution comprises a main absorbent, an amine-based absorption aid, a phase separation promoter, and water, wherein per liter of solution:

[0009] The molar concentration of the main absorbent is 2M-4M;

[0010] The molar concentration of the absorption aid is 1M-2M;

[0011] The molar concentration of the phase separation promoter is 5M.

[0012] Furthermore, the primary absorbent is either a primary amine or a secondary amine.

[0013] Furthermore, the primary amine is preferably ethanolamine, and the secondary amine is preferably diethanolamine.

[0014] Furthermore, the absorption aid is one of a tertiary amine, a polyamine, or a piperazine.

[0015] Furthermore, the phase separation promoter is sulfolane or dimethyl sulfoxide.

[0016] Further, the tertiary amine includes 3-dimethylamino-1,2-propanediol, 3-diethylamino-1,2-propanediol, 1-dimethylamino-2-propanol, 1-diethylamino-2-propanol, 3-dimethylaminopropylamine, and 3-diethylaminopropylamine;

[0017] The polyamines include diethylenetriamine, triethanolamine, and N-methyldiethanolamine;

[0018] The piperazines include N-ethylpiperazine, 2-methylpiperazine, piperazine, 1-(2-aminoethyl)piperazine, and N-(2-hydroxyethyl)piperazine.

[0019] Furthermore, the molar concentration ratio of the main absorbent, absorption aid, and phase separation promoter is 3:1:5.

[0020] Furthermore, the molar concentration ratio of the main absorbent, absorption aid, and phase separation promoter is 2:2:5.

[0021] Furthermore, the molar concentration ratio of the main absorbent, absorption aid, and phase separation promoter is 4:1:5.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. During the CO2 absorption process, the phase change absorbent provided by this invention, under the action of a phase separation promoter, gradually separates into an organic amine-rich liquid phase and a physical solvent-poor liquid phase due to the salting-out effect as the CO2 absorption accumulates. The rich liquid phase is the upper layer, accounting for 45%-60% of the volume. At absorption phase equilibrium, the CO2 occupancy of the rich liquid phase is above 92%, demonstrating good absorption performance. During regeneration, the desorption rate can reach about 90%, and the desorption energy consumption can be reduced by more than 50%, fully demonstrating the excellent CO2 capture performance of the solvent described in this invention.

[0024] 2. In the phase change absorbent provided by this invention, the phase separation agent is sulfolane and dimethyl sulfoxide, preferably sulfolane. Sulfolane is a non-volatile, inert, and neutral solvent with properties similar to water, exhibiting a strong physical binding force to CO2. By compounding it to replace part of the water in an amine aqueous solution for CO2 absorption, it not only promotes liquid-liquid phase separation but also further increases the CO2 absorption loading (compared to water). The addition of sulfolane alters the gas-liquid equilibrium of the original amine solvent-CO2 absorption system and reduces the latent heat consumed by water evaporation during desorption.

[0025] 3. This invention, by combining primary and secondary amines with fast absorption rates with tertiary amines or polyamines with large absorption capacity or low desorption energy consumption, can significantly improve the shortcomings of single amine solvent absorption performance, and can simultaneously achieve high absorption rate, large absorption capacity and low desorption energy consumption, thereby achieving complementary advantages.

[0026] 4. The absorbent provided by this invention uses an aqueous solution of organic amines as the main absorbent, and a phase separation promoter is added to achieve liquid-liquid phase separation. After absorbing carbon dioxide, this type of absorbent separates into upper and lower liquid phases. The upper liquid phase is a rich liquid phase, in which the amine concentration is high and the carbon dioxide content is high. In addition, the absorbent of this invention also has a high desorption rate and low regeneration energy consumption. Attached Figure Description

[0027] Figure 1 This is a comparison diagram of the phase separation volumes of Embodiments 1-8 and Comparative Example 1 of the present invention;

[0028] Figure 2 This is a comparison chart of absorption rates in the gas-liquid phase equilibrium absorption experiment of Test Example 1 of the present invention;

[0029] Figure 3 This is a comparison chart of the occupancy rate of CO2 in the liquid-rich phase after the gas-liquid phase equilibrium absorption experiment in Test Example 1 of this invention;

[0030] Figure 4 This is a comparison chart of CO2 loading and desorption rate in the absorbent in Test Examples 1 and 2 of this invention;

[0031] Figure 5This is a comparison diagram of the phase separation characteristics and absorption / desorption performance of three MEA / DMAPA / TMS ternary phase change absorbent systems with different molar ratios in Test Example 3 of this invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figure 1-5 For ease of statistics and comparison, the main absorbent is denoted as A, of which ethanolamine (MEA) is denoted as A1 and diethanolamine (DEA) is denoted as A2.

[0034] The absorption aid is designated as B, and the following are designated as B1-B14 respectively: 3-dimethylamino-1,2-propanediol (DMAP), 3-diethylamino-1,2-propanediol (DEAP), 1-dimethylamino-2-propanol (DMIPA), 1-diethylamino-2-propanol (DEIPA), triethanolamine (TEA), N-methyldiethanolamine (MDEA), 3-dimethylaminopropylamine (DMAPA), 3-diethylaminopropylamine (DEAPA), diethylenetriamine (DETA), N-ethylpiperazine (NEPZ), 2-methylpiperazine (MP), piperazine (PZ), 1-(2-aminoethyl)piperazine (AEP), and N-(2-hydroxyethyl)piperazine (NHPEZ).

[0035] Phase separation promoters are denoted as C, of ​​which sulfolane (TMS) is denoted as C1 and dimethyl sulfoxide (DMSO) is denoted as C2.

[0036] The specific implementation methods and solutions are as follows:

[0037] Example 1

[0038] Weigh out A1 (MEA), B1 (DMAP), and C1 (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1 / B1 / C1 / H2O. The solution volume is 50 ml. Place the absorbent in a constant temperature bath and heat it to 40°C. Introduce pure CO2 gas at a flow rate of 100 mL / min and allow it to absorb for 60 min. Observe the phase separation after standing. After complete separation, record the phase volume, titrate the amine concentrations of the upper and lower liquid phases using the hydrochloric acid method, and calculate the CO2 loading.

[0039] Example 2

[0040] Weigh out A1 (MEA), B2 (DEAP), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1 / B2 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0041] Example 3

[0042] Weigh out A1 (MEA), B3 (DMIPA), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1 / B3 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0043] Example 4

[0044] Weigh out A1 (MEA), B6 ​​(MDEA), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1 / B6 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0045] Example 5

[0046] Weigh out A1 (MEA), B7 (DMAPA), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1 / B7 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0047] Example 6

[0048] Weigh out A1 (MEA), B9 (DETA), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1 / B9 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0049] Example 7

[0050] Weigh out Al (MEA), B10 (NEPZ), and Cl (TMS) respectively according to the molar concentration ratio A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as Al / B10 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0051] Example 8

[0052] Weigh out Al (MEA), B11 (MP), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 3:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as Al / B11 / Cl / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0053] Example 9

[0054] Weigh out A1 (MEA), B7 (DMAPA), and C1 (TMS) respectively, using a molar concentration ratio of A:B:C = 4:1:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A14 / B71 / C1 / H2O. The solution volume and experimental conditions are the same as in Example 1.

[0055] Example 10

[0056] Weigh out A1 (MEA), B7 (DMAPA), and Cl (TMS) respectively, using a molar concentration ratio of A:B:C = 2:2:5, and mix them with an appropriate amount of water to obtain a homogeneous solution, denoted as A1² / B7² / Cl / H₂O. The solution volume and experimental conditions are the same as in Example 1.

[0057] Comparative Example 1

[0058] Weigh out A1 (MEA) and C1 (TMS) at a molar concentration ratio of 4:5, respectively, and mix them with an appropriate amount of water to obtain a homogeneous MEA / TMS solution. The solution volume and experimental conditions are the same as in Example 1.

[0059] Comparative Example 2

[0060] Prepare a 5M MEA solution. The solution volume and experimental conditions are the same as in Example 1.

[0061] Figure 1 The figures show a comparison of the phase separation volumes of Examples 1-8 and Comparative Example 1 provided by this invention. As can be seen from the figures, the phase separation volume ratio of all solutions is approximately 1:1, with little difference in volume between the upper and lower liquid phases. Therefore, the amount of rich liquid used for desorption can be effectively reduced, thereby lowering desorption energy consumption.

[0062] Test Example 1. Absorption Performance of Phase Change Absorbents

[0063] 500 mL of each absorbent solution was prepared according to the concentrations described in Examples 1-8 and Comparative Examples 1-2. Simulated flue gas (a mixture of CO2 and N2, total flow rate 1000 mL / min, CO2 partial pressure 15%) was introduced into the solutions at 40°C and normal pressure for absorption experiments. The CO2 concentration in the outlet gas after absorption was recorded using a CO2 analyzer. The entire experiment lasted approximately 240 min until gas-liquid phase equilibrium was reached. The variation of the absorption rate over time was obtained, and the results are shown in […]. Figure 2 .from Figure 2It can be seen that all solutions have the same initial absorption rate, but as the absorption process proceeds, the absorption rate shows different trends due to the different reaction mechanisms between different types of solvents and CO2, as well as the influence of solution viscosity, etc. The absorption rates of Examples 5, 6, and 8 decrease more slowly than those of Examples 1-4, 7, and Comparative Example 1, indicating that Examples 5, 6, and 8 can maintain a relatively fast absorption rate overall. However, the overall absorption rate of all examples is lower than that of the 5MMEA solution in Comparative Example 2, mainly due to the phase enrichment of the phase change solvent and its higher viscosity before and after phase separation. In addition, the occupancy of CO2 in the rich liquid phase was calculated based on the experimental results, and the results are shown in […]. Figure 3 In all the solvent-rich solutions after phase separation, the CO2 content was above 92%, with Example 6 showing a CO2 content as high as 99.3%, which fully demonstrates the excellent phase separation characteristics of the ternary phase change solvent.

[0064] Test Example 2. Desorption Performance of Phase Change Absorbents

[0065] After the solution in Test 1 that had absorbed CO2 was allowed to stand for 20 hours until complete phase separation, the lean and rich liquid phases were separated using a separatory funnel, and the rich liquid was desorbed. The reactor containing the rich liquid was placed in a constant-temperature oil bath at 120℃. When the solution temperature reached 70℃, N2 was introduced at a rate of 500 mL / min. The CO2 concentration in the outlet gas after absorption was recorded using a CO2 analyzer, and the electricity consumption was recorded using an electric meter. The desorption experiment lasted 180-260 min. The CO2 loading and desorption rate of the upper rich liquid phase after CO2 absorption and the desorbed solution are shown in [reference needed]. Figure 4 As can be seen from the figure, the CO2 loading values ​​of all ternary phase change solvent systems are greater than 5 MMEA, with Example 6 having the highest loading value at 4.71 mol / L. However, Example 6 also had the highest loading value of the regenerated desorbent, resulting in the lowest desorption rate, indicating that the cyclic loading of this absorbent is poor.

[0066] Test Example 3. Performance Analysis of Solutions with Different Molar Concentration Ratios

[0067] Taking the MEA / DMAPA / TMS ternary phase change solution selected in Example 5 as an example, the phase separation characteristics and absorption / desorption performance of three absorbent systems with different molar ratios of 3:1:5, 4:1:5, and 2:2:5 were compared and analyzed. The experimental schemes used in the phase separation experiments are shown in Examples 5, 9, and 10, respectively. The experimental schemes used in the absorption / desorption experiments were the same as those in Test Examples 1 and 2. The results are shown in... Figure 5 As can be seen from the figure, the phase separation volume ratios of the three different solutions are not significantly different, but the solution with the higher total amine concentration has the highest absorption rate and equilibrium load value; the increase of DMAPA content in the solution is beneficial to the enrichment of CO2 in the rich solution.

[0068] This invention, through the study of phase separation characteristics of solutions with various concentration ratios, obtained the types and ratios of absorbents capable of liquid-liquid phase transition, and systematically studied their phase transition characteristics. The absorbent is homogeneous before absorbing carbon dioxide, but begins to separate into two phases upon contact with CO2-containing gas. As the absorption process proceeds, the amine solvent and its carbon dioxide absorption products gradually accumulate, eventually forming stable upper and lower liquid phases. The upper liquid phase is rich in liquid, and the lower liquid phase is lean in liquid.

[0069] Taking a solvent system with a solvent molar ratio of 3:1:5 as an example, at phase equilibrium, the CO2 occupancy of the rich liquid phase in each absorbent system is above 92%, and the absorption loading value is between 3.04 mol / L and 4.71 mol / L. After absorption, the upper and lower liquid phases are separated, and the upper liquid phase is sent to a desorption tower for desorption. The desorption temperature is 100-120℃, and the desorption time is between 180-260 min. The CO2 desorption rate reaches over 70%, and the desorption energy consumption is reduced by approximately 10-55% compared to a 5M MEA.

[0070] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A highly efficient ternary liquid-liquid phase change absorbent for capturing carbon dioxide, characterized in that: The solution comprises the main absorbent, amine absorption aid, phase separation promoter, and water, with each liter of solution containing: The molar concentration of the main absorbent is 2M-4M; The molar concentration of the absorption aid is 1M-2M; The molar concentration of the phase separation promoter is 5M; The main absorbent is one of a primary amine or a secondary amine; The primary amine is ethanolamine, and the secondary amine is diethanolamine; The phase separation promoter is sulfolane or dimethyl sulfoxide; The molar concentration ratio of the main absorbent, absorption aid, and phase separation promoter is 3:1:5, 2:2:5, or 4:1:

5. The absorption aid is one of tertiary amines, polyamines, or piperazines; The tertiary amines include 3-dimethylamino-1,2-propanediol, 3-diethylamino-1,2-propanediol, 1-dimethylamino-2-propanol, 1-diethylamino-2-propanol, 3-dimethylaminopropylamine, and 3-diethylaminopropylamine. The polyamines include diethylenetriamine, triethanolamine, and N-methyldiethanolamine; The piperazines include N-ethylpiperazine, 2-methylpiperazine, piperazine, 1-(2-aminoethyl)piperazine, and N-(2-hydroxyethyl)piperazine.

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