Carbon dioxide collection and absorption liquid, its use, and carbon dioxide collection method.

Abstract

This invention discloses a carbon dioxide collection absorbent, its use, and a method for collecting carbon dioxide, relating to the technical field of carbon dioxide collection. The absorbent comprises an absorbent, an activator, an auxiliary agent, and / or a non-aqueous solvent, wherein the absorbent is at least one selected from 3-amino-1-propanol, monoethanolamine, and diethanolamine. Compared to conventional phase-change absorbents, the absorbent has significant advantages such as low viscosity, high carbon dioxide absorption capacity, and low regeneration temperature, which have positive significance in reducing energy consumption and costs in the process of collecting carbon dioxide from exhaust gas.

Description

Detailed Description of the Invention

[0001] [Cross - reference to Related Applications] This application claims the benefit of Chinese Patent Application No. 202310649622.6, filed on June 2, 2023, the content of which is incorporated herein by reference.

[0002] [Technical Field] The present invention belongs to the technical field of carbon dioxide capture, and specifically relates to a carbon dioxide capture absorbent, its use, and a carbon dioxide capture method.

[0003] [Background Art] Existing mature chemical absorption methods for removing carbon dioxide used in pilot - scale and industrialization capture carbon dioxide using ethanolamine (MEA) as an absorbent. However, the energy consumption required for the regeneration of MEA (3.7 - 4.2 GJ / tCO2) is high, and the capture cost is also high, so its subsequent development is restricted.

[0004] Currently, in order to improve the absorption and desorption performance of the absorbent, effectively reduce the energy consumption for desorption, and save the capture cost, it mainly focuses on two aspects: the development of new absorbents and the improvement of processes or the research of new processes.

[0005] Absorbents that cause phase separation during / after CO2 absorption are usually called phase - change absorbents. In a phase - change absorption system, a CO2 - lean phase and a CO2 - rich phase are formed by CO2 absorption. By heating only the CO2 - rich phase for regeneration, the energy consumption for system regeneration can be reduced, so this is regarded as a promising CO2 capture technology with low energy consumption.

[0006] Currently, due to some drawbacks of phase - change absorbents, their large - scale use is restricted. Therefore, an absorbent for capturing carbon dioxide by phase separation is required.

[0007] [Summary of the Invention] [Problems the invention aims to solve] The objective of the present invention is to provide a carbon dioxide collection absorbent, its use, and a method for collecting carbon dioxide, in order to solve the problems in conventional carbon dioxide collection processes using organic amine solution-based absorbents, such as high energy consumption for solvent regeneration, the need to raise the regeneration temperature to the boiling point of the solvent, high viscosity of the absorbent, low carbon dioxide absorption capacity, and tendency to foam.

[0008] [Means for solving the problem] To achieve the above objective, a first aspect of the present invention provides a carbon dioxide collection and absorption liquid, the absorption liquid comprising an absorbent, an activator, an auxiliary agent, and a non-aqueous solvent. The absorbent is at least one selected from 3-amino-1-propanol, diglycolamine, monoethanolamine, and diethanolamine. The mass ratio of the absorbent to the activator is 1:1 to 1:4. The viscosity of the absorbent liquid is 6 to 50 mPa·s. The pKa of the absorbent is 8.5 to 10.

[0009] A second aspect of the present invention provides the use of the absorbent liquid provided in the first aspect of the present invention in the field of carbon dioxide capture.

[0010] A third aspect of the present invention provides a method for capturing carbon dioxide, the method being: Step (1) involves bringing a carbon dioxide-containing gas into contact with an absorbent to obtain an upper liquid phase and a lower rich liquid phase that has absorbed carbon dioxide, Step (2) involves thermally regenerating the rich liquid phase to obtain a first lean liquid phase, The process includes step (3), which involves rectifying a portion of the first lean liquid phase to obtain a second lean liquid phase, and recycling it by returning it to the absorbent liquid of step (1). The absorbent liquid is the absorbent liquid provided in the first aspect of the present invention.

[0011] [Effects of the invention] The above technical solutions provide the following beneficial effects of the present invention.

[0012] (1) The absorbent liquid produced by the present invention has the advantage of low viscosity (absorbent liquid: 6-50 mPa·s, rich liquid phase: 200-600 mPa·s) due to the synergistic effect of the absorbent, activator, non-aqueous solvent, and auxiliary agent. Most conventional phase-change absorbents have a viscosity of 100 mPa·s or more (rich liquid phase: 1000 mPa·s or more).

[0013] (2) The mass ratio of the absorbent to the activator in the absorbent solution of the present invention is within the range of 1:1 to 1:4, so that the absorbent solution undergoes phase separation after absorbing carbon dioxide. If the mass ratio is not within the above range, the absorbent solution will not be able to undergo phase separation.

[0014] (3) Compared to conventional phase-change absorbents, the absorbent liquid of the present invention has significant advantages such as a large carbon dioxide absorption capacity, no need for the regeneration temperature to reach the boiling point of the solvent, and low foaming, which have positive significance in reducing energy consumption and costs in the carbon dioxide capture process.

[0015] (4) The present invention also solves the problem that when actual exhaust gas contains about 8% water, water is absorbed into the non-aqueous solvent during the carbon dioxide capture process, but because the regeneration temperature of the non-aqueous system does not reach the water vapor generation temperature, water content accumulates in the non-aqueous system, that is, a dynamic imbalance of water occurs in the non-aqueous solvent system. In other words, by adopting the process proposed by the present invention, the dynamic balance of the non-aqueous system can be maintained, and energy saving can be achieved by utilizing the water vapor generated by rectification as part of the heat source for the reboiler.

[0016] [Brief explanation of the drawing] Figure 1 shows an apparatus for carrying out the carbon dioxide capture method of the present invention.

[0017] [Explanation of symbols] 1. Absorption tower Two-phase separation tank 3 Heat exchanger 4 Regeneration Tower 5 Reboiler 6. Rectification tower [Modes for carrying out the invention] Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described herein are for illustrative and interpretive purposes only and do not limit the present invention.

[0018] A first aspect of the present invention provides a carbon dioxide collection and absorption liquid, the absorption liquid comprising an absorbent, an activator, an auxiliary agent, and a non-aqueous solvent. The absorbent is at least one selected from 3-amino-1-propanol (3AP), diglycolamine (DGA), monoethanolamine (MEA), and diethanolamine (DEA). The mass ratio of the absorbent to the activator is 1:1 to 1:4. The viscosity of the absorbent liquid is 6 to 50 mPa·s. The pKa of the absorbent is 8.5 to 10.

[0019] Since the conventional absorbent contains an organic solvent, its viscosity is higher than that of an aqueous solution, and it affects the carbon dioxide absorption effect due to phase change, resulting in a decrease in the absorption and regeneration performance of the absorbent. To solve this problem, in the absorbent provided by the present invention, additives are added based on limited components and amounts, thereby improving the phase change absorption effect and the viscosity performance. Preferably, the additive is a polyether, preferably selected from polyoxyethylene ether or polyoxypropylene ether. More preferably, the weight average molecular weight of the polyoxyethylene ether or polyoxypropylene ether is 3000 - 5000 g / mol, and even more preferably 4000 - 5000 g / mol. The polyether can be obtained as a commercial product, for example, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (product number P131344, Cas No. 9003-11-6, weight average molecular weight 4400 g / mol) manufactured by Aladdin Chemical Reagent Co., Ltd.

[0020] When the additive is added, the upper layer liquid phase obtained by the absorbent absorbing carbon dioxide has a defoaming time of 30 - 70 s, and the obtained lower layer rich liquid phase has a defoaming time of 1 - 8 s. The lower layer rich liquid phase has a defoaming time of 8 - 30 s after thermal regeneration and a defoaming time of 6 - 20 s after mixing with the upper layer liquid phase. On the other hand, for the upper layer liquid phase obtained by the conventional absorbent without the additive absorbing carbon dioxide, the defoaming time is 100 - 500 s, and the obtained lower layer rich liquid phase has a defoaming time of 1 - 5 s. The lower layer rich liquid phase has a defoaming time of 30 - 60 s after thermal regeneration and a defoaming time of 30 - 60 s after mixing with the upper layer liquid phase.

[0021] In some preferred embodiments of the present invention, preferably, the addition amount of the auxiliary agent is 0.01 to 1 wt‰, more preferably 0.05 to 0.5 wt‰. The addition amount of the auxiliary agent in the present invention is very small. This is to defoam the rich liquid phase in a timely manner. On the other hand, the auxiliary agent can exert a synergistic effect with the non-aqueous solvent, absorbent, and activator of the present invention, can reduce the viscosity of the absorbent liquid, and can also assist in improving the phase change absorption performance of the absorbent liquid. In short, within the above range of the addition amount, the absorbent liquid provided by the present invention can ensure reducing the viscosity and providing a better phase separation effect.

[0022] In some preferred embodiments of the present invention, preferably, the activator is selected from tertiary amines and / or tertiary amine compositions with a LogP value of -0.1 to 0.6, preferably at least one of 3-dimethylamino-1-propanol (3DMA1P), diethylethanolamine (DEEA), 1-dimethylamino-2-propanol (1DMA2P), triethanolamine (TEA), tetramethylpropylenediamine (TMPDA), tetramethylethylenediamine (TMEEA), and pentamethyldiethylenetriamine (PMDETA).

[0023] In some preferred embodiments of the present invention, preferably, the non-aqueous solvent is at least one selected from ethylene glycol (EG), glycerol (GL), 2-propylene glycol (12P), and 1,4-butanediol (BDO). The energy consumption for solvent regeneration in the carbon dioxide capture process using a conventional organic amine solution-based absorbent can be reduced. By using a non-aqueous solvent instead of water, while reducing the viscosity of the rich liquid, the latent heat consumption of the solvent during regeneration can be avoided.

[0024] In some preferred embodiments of the present invention, preferably, based on the total amount of the absorbent liquid, the content of the non-aqueous solvent is 30 wt% or less, preferably 10 to 20 wt%. The content of the absorbent is 10 to 60 wt%, preferably 20 to 35 wt%.

[0025] To improve the absorption performance of the absorbent solution, the tertiary amine is used as an activator, and its content is 10 to 80 wt%, preferably 50 to 70 wt%, based on the total amount of the absorbent solution.

[0026] The viscosity of the absorbent solution is 6-50 mPa·s (25°C). Reducing the viscosity improves the fluidity of the solution and also improves the mass transfer rate of the solution.

[0027] In the present invention, the absorbent solution provided can provide a good phase-change absorption effect under limited compositional conditions. Preferably, the carbamate salt formed by the absorption of CO2 by the absorbent has a solubility of 1 mol / kg or less in the activator. By having the absorbent solution provided in the present invention have the above composition and the above solubility relationship between the absorbent and the activator is also limited, the present invention can provide a technical effect that allows for better phase-change absorption of carbon dioxide. The phase-change absorption effect that the present invention can provide cannot be obtained without considering the relationship between the amounts used of the absorbent and the activator and the above solubility relationship.

[0028] When the absorbent liquid absorbs CO2, two liquid phases with significantly different CO2 loads are formed, with almost all of the CO2 concentrated in the lower phase. After separation, the upper liquid phase is directly recycled, the lower, CO2-rich liquid phase is thermally regenerated, and the resulting lean liquid phase is recycled and reused together with the upper liquid phase. Compared to conventional chemical absorption methods, the phase separation process of the present invention can reduce the amount of liquid used for thermal regeneration for the same amount of CO2 removal, thus reducing energy consumption for regeneration.

[0029] Here, the carbamate salt formed by the absorption of CO2 by the absorbent has a solubility of 1 mol / kg or less in the activator.

[0030] A second aspect of the present invention provides the use of the absorbent liquid provided in the first aspect of the present invention in the field of carbon dioxide capture.

[0031] A third aspect of the present invention provides a method for capturing carbon dioxide, the method being: Step (1) involves bringing a carbon dioxide-containing gas into contact with an absorbent to obtain an upper liquid phase and a lower rich liquid phase that has absorbed carbon dioxide, Step (2) involves thermally regenerating the rich liquid phase to obtain a first lean liquid phase, The process includes step (3), which involves rectifying a portion of the first lean liquid phase to obtain a second lean liquid phase, and recycling it by returning it to the absorbent liquid of step (1). The absorbent liquid is the absorbent liquid provided in the first aspect of the present invention.

[0032] In some preferred embodiments of the present invention, preferably in step (2), the thermal regeneration process first performs a first thermal regeneration step, and then performs a second thermal regeneration step. Here, the apparatus for the first thermal regeneration step is a regeneration tower, and the apparatus for the second thermal regeneration step is a reboiler, preferably selected from a conventional reboiler, a supergravity reboiler, or a flowing liquid film reboiler. In the present invention, the regeneration temperature may be lower than the regeneration temperature of the non-aqueous solvent.

[0033] In some preferred embodiments of the present invention, the steam generated by the distillation is preferably used as part of the heat source for the reboiler.

[0034] In some preferred embodiments of the present invention, preferably, in step (1), the contact temperature is 30 to 60°C, and the viscosity of the rich liquid phase (at 25°C) is 200 to 600 mPa·s.

[0035] In some preferred embodiments of the present invention, preferably, in step (2), the temperature of the second heat regeneration step is 85 to 105°C, more preferably 90 to 100°C.

[0036] In some preferred embodiments of the present invention, preferably in step (3), the portion of the first lean liquid phase is 5 to 30 wt% of the first lean liquid phase, and the rectification temperature is 105 to 115°C.

[0037] In some preferred embodiments of the present invention, the concentration of the outlet water of the rectification column used for rectification is preferably 99.99%.

[0038] The above method according to the present invention can be carried out using the apparatus shown in Figure 1, and the specific procedure is as follows: (1) A carbon dioxide-containing gas is introduced into the absorption tower 1 and brought into contact with the absorbent liquid inside it, and then the absorbent liquid is introduced into the phase separation tank 2 to obtain an upper liquid phase and a lower rich liquid phase that has absorbed carbon dioxide. (2) The rich liquid phase in step (1) is sequentially fed into the regeneration tower 4 and the reboiler 5 via the exchanger 3 to regenerate heat and obtain the first lean liquid phase. (3) A portion of the first lean liquid phase is introduced into the rectification column 6 and rectified to obtain a second lean liquid phase, and the second lean liquid phase is returned to the absorbent liquid of step (1) and recycled to the absorption column 1. The absorbent liquid is the absorbent liquid provided in the first aspect of the present invention.

[0039] The present invention will be further described below with reference to specific examples.

[0040] The additive, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), has a weight-average molecular weight of 4400 g / mol and was purchased from Aladdin Chemical Reagents Co., Ltd.

[0041] The boiling point of 1,4-butanediol (BDO) is 228°C (0.1 MPa).

[0042] The boiling point of ethylene glycol (EG) is 197.3°C (0.1 MPa).

[0043] Example 1 Composition of the absorbent solution: The mass ratio of the absorbent MEA, the activator 3DMA1P, and the non-aqueous solvent EG is 3:6:1. The amount of absorbent MEA used is 30 wt%, the amount of activator 3DMA1P used is 60 wt%, the amount of non-aqueous solvent EG used is 9.92 wt%, the amount of auxiliary agent used is 0.08 wt‰, the total volume of the absorbent solution is 30 L, the viscosity of the absorbent solution (at 25°C) is 16 mPa·s, the pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0044] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 350 mPa·s) that had absorbed carbon dioxide.

[0045] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 3.71 mol CO2 / kg. After the first thermal regeneration process was performed on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a conventional reboiler to obtain the first lean liquid phase.

[0046] Subsequently, a portion of the first lean liquid phase (8 wt%) was introduced into a rectification column and rectified at a rectification temperature of 108°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 90%, the energy consumption for regeneration was 2.95 GJ / t CO2.

[0047] Here, the upper liquid phase had a defoaming time of 35 s, the lower rich liquid phase had a defoaming time of 5 s, the lower rich liquid phase had a defoaming time of 15 s after thermal regeneration, and a defoaming time of 7 s after mixing with the upper liquid phase.

[0048] Here, the carbamate salt formed when the absorbent MEA absorbed carbon dioxide had a solubility of 0.77 mol / kg in the activator 3DMA1P.

[0049] Example 2 Composition of the absorbent solution: The mass ratio of the absorbent DEA to the activator PMDETA is 2:7, the amount of auxiliary agent used is 1 wt‰, the amount of absorbent DEA used is 20 wt%, the amount of activator PMDETA used is 70 wt%, non-aqueous solvent BDO accounts for 9.99 wt% of the total mass of the absorbent solution, the total volume of the absorbent solution is 30 L, the viscosity of the absorbent solution (at 25°C) is 10 mPa·s, the pKa of the absorbent is 9.0, and the LogP value of the activator is 0.54.

[0050] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 39.85°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 380 mPa·s) that had absorbed carbon dioxide.

[0051] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 3.78 mol CO2 / kg. After the first thermal regeneration process was performed on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 100°C using a conventional reboiler to obtain the first lean liquid phase (0.26 mol CO2 / kg residual).

[0052] Subsequently, a portion of the first lean liquid phase (10 wt%) was introduced into a rectification column and rectified at a rectification temperature of 110°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 80%, the energy consumption for regeneration was 2.48 GJ / t CO2.

[0053] Here, the upper liquid phase had a defoaming time of 40 s, the lower rich liquid phase had a defoaming time of 5 s, the lower rich liquid phase had a defoaming time of 10 s after thermal regeneration, and a defoaming time of 8 s after mixing with the upper liquid phase.

[0054] Here, the carbamate salt formed when the absorbent DEA absorbed carbon dioxide had a solubility of 0.65 mol / kg in the activator PMDETA.

[0055] Example 3 Composition of the absorbent solution: The mass ratio of the absorbent 3AP to the activator TMPDA was 1:3. The amount of absorbent 3AP used was 22.5 wt%, and the amount of activator TMPDA used was 67.5 wt%. GL, a non-aqueous solvent, accounted for 10% of the total mass of the solution. The amount of additives added was 0.1 wt‰. The total volume of the absorbent solution was 30 L. The viscosity of the absorbent solution (at 25°C) was 12 mPa·s. The pKa of the absorbent was 9.96, and the LogP value of the activator was 0.43.

[0056] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 300 mPa·s) that had absorbed carbon dioxide.

[0057] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 3.75 molCO2 / L. After performing a first thermal regeneration process on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a conventional reboiler to obtain the first lean liquid phase.

[0058] Subsequently, a portion of the first lean liquid phase (5 wt%) was introduced into a rectification column and rectified at a rectification temperature of 110°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 80%, the energy consumption for regeneration was 2.22 GJ / t CO2.

[0059] Here, the upper liquid phase had a defoaming time of 42 seconds, the lower rich liquid phase had a defoaming time of 4 seconds, the lower rich liquid phase had a defoaming time of 14 seconds after thermal regeneration, and a defoaming time of 15 seconds after mixing with the upper liquid phase.

[0060] Here, the carbamate salt formed when the absorbent 3AP absorbed carbon dioxide had a solubility of 0.58 mol / kg in the activator TMPDA.

[0061] Example 4 Composition of the absorbent solution: The mass ratio of the absorbent MEA to the activator 3DMA1P is 2:6, the amount of absorbent MEA used is 20 wt%, the amount of activator 3DMA1P used is 60 wt%, the amount of non-aqueous solvent EG used is 19.999 wt%, the amount of auxiliary agent used is 0.1 wt‰, the total volume of the absorbent solution is 30 L, the viscosity of the absorbent solution (at 25°C) is 6 mPa·s, the pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0062] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 280 mPa·s) that had absorbed carbon dioxide.

[0063] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 4.01 mol CO2 / kg. After the first thermal regeneration process was performed on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a supergravity reboiler to obtain the first lean liquid phase.

[0064] Subsequently, a portion of the first lean liquid phase (10 wt%) was introduced into a rectification column and rectified at a rectification temperature of 110°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower rich liquid was 82.5%, the energy consumption for regeneration was 2.76 GJ / t CO2.

[0065] Here, the upper liquid phase had a defoaming time of 40 s, the lower rich liquid phase had a defoaming time of 5 s, the lower rich liquid phase had a defoaming time of 10 s after thermal regeneration, and a defoaming time of 10 s after mixing with the upper liquid phase.

[0066] Comparative Example 1 Composition of the absorbent solution: The mass ratio of the absorbent DEA to the activator PMDETA was 3:6. The amount of absorbent DEA used was 30 wt%, the amount of activator PMDETA used was 60 wt%, and the amount of non-aqueous solvent EG used was 10 wt%. No auxiliary agents were added. The total volume of the absorbent solution was 30 L. The viscosity of the absorbent solution (at 25°C) was 19 mPa·s. The pKa of the absorbent was 9.0, and the LogP value of the activator was 0.54.

[0067] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 320 mPa·s) that had absorbed carbon dioxide.

[0068] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 3.69 mol CO2 / kg. After the first thermal regeneration process was performed on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a conventional reboiler to obtain the first lean liquid phase.

[0069] Subsequently, a portion of the first lean liquid phase (8 wt%) was introduced into a rectification column and rectified at a rectification temperature of 105°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 80%, the energy consumption for regeneration was 2.45 GJ / t CO2.

[0070] Here, the upper liquid phase had a defoaming time of 120 s, the lower rich liquid phase had a defoaming time of 4 s, the lower rich liquid phase had a defoaming time of 50 s after thermal regeneration, and a defoaming time of 45 s after mixing with the upper liquid phase.

[0071] Comparative Example 2 Composition of the absorbent solution: The mass ratio of the absorbent MEA to the activator 3DMA1P is 1:1. The amount of absorbent MEA used is 40 wt%, the amount of activator 3DMA1P used is 40 wt%, the non-aqueous solvent EG accounts for 20% wt of the total mass of the solution, no auxiliary agents are added, the total volume of the absorbent solution is 30 L, the viscosity of the absorbent solution (at 25°C) is 32 mPa·s, the pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0072] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 250 mPa·s) that had absorbed carbon dioxide.

[0073] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 3.55 molCO2 / L. After performing a first thermal regeneration process on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a conventional reboiler to obtain the first lean liquid phase.

[0074] Subsequently, a portion of the first lean liquid phase (5 wt%) was introduced into the rectification column and rectified at a rectification temperature of 105°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 80%, the energy consumption for regeneration was 2.57 GJ / t CO2.

[0075] Here, the upper liquid phase had a defoaming time of 130 s, the lower rich liquid phase had a defoaming time of 4 s, the lower rich liquid phase had a defoaming time of 50 s after thermal regeneration, and a defoaming time of 50 s after mixing with the upper liquid phase.

[0076] Comparative Example 3 The absorbent solution is a 305.4 g / L MEA aqueous solution, in a volume of 30 L, with a viscosity of 1 mPa·s (at 25°C).

[0077] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 39.85°C to obtain a rich liquid (viscosity (25°C) 10 mPa·s).

[0078] Analysis of the carbon dioxide content of a sample of the rich solution revealed a maximum absorption capacity of 2.52 mol CO2 / L, and the aqueous solution did not undergo phase separation after carbon dioxide absorption. After a first thermal regeneration process was performed on the aqueous solution using a regeneration tower, a second thermal regeneration process was performed at 120°C using a conventional reboiler, resulting in a residual CO2 content of 1.29 mol / kg. The resulting lean solution was returned to the absorption tower for recycling. With a collection efficiency of 90%, the energy consumption for regeneration was 5.1 GJ / t CO2.

[0079] In this case, the rich liquid phase had a defoaming time of 5 seconds, and the rich liquid phase had a defoaming time of 6 seconds after thermal regeneration.

[0080] Comparative Example 4 The absorbent solution is 30 L of a 305.4 g / L MEA aqueous solution, and its viscosity (at 25°C) is 1 mPa·s.

[0081] Carbon dioxide was collected using the absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain a rich liquid (viscosity (25°C) 280 mPa·s).

[0082] After carbon dioxide was absorbed, the aqueous solution did not undergo phase separation. A first thermal regeneration process was performed on the aqueous solution using a regeneration tower, followed by a second thermal regeneration process at 115°C using a conventional reboiler, resulting in a residual CO2 of 0.56 mol / kg. The resulting lean liquid was returned to the absorption tower for recycling. With a collection efficiency of 80%, the energy consumption for regeneration was 4.25 GJ / t CO2.

[0083] In this case, the rich liquid phase had a defoaming time of 5 seconds, and the rich liquid phase had a defoaming time of 6 seconds after thermal regeneration.

[0084] Comparative Example 5 The composition of the absorbent solution is as follows: the mass ratio of the absorbent MEA, the activator 3DMA1P, and the non-aqueous solvent EG is 1:6:1. The amount of MEA used is 12.5 wt%, the amount of activator 3DMA1P used is 75 wt%, the amount of non-aqueous solvent EG used is 12.5 wt%, and the amount of auxiliary agents used is 0.08 wt‰. The total volume of the absorbent solution is 30 L, and the viscosity of the absorbent solution (at 25°C) is 12 mPa·s.

[0085] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C. After the carbon dioxide was absorbed, the absorbent liquid did not undergo phase separation. A first thermal regeneration process was performed on the absorbent liquid using a regeneration tower, followed by a second thermal regeneration process at 120°C using a conventional reboiler, resulting in a residual CO2 of 0.47 mol / kg. The resulting lean liquid was returned to the absorption tower for recycling. When the collection rate was 90%, the energy consumption for regeneration was 3.63 GJ / t CO2.

[0086] Comparative Example 6 The composition of the absorbent solution is as follows: the mass ratio of the absorbent MEA, the activator 3DMA1P, and the non-aqueous solvent EG is 3:1:1. The amount of MEA used is 60 wt%, the amount of activator 3DMA1P used is 20 wt%, the amount of non-aqueous solvent EG used is 20 wt%, and the amount of auxiliary agents used is 0.08 wt‰. The total volume of the absorbent solution is 30 L, and the viscosity of the absorbent solution (at 25°C) is 12 mPa·s.

[0087] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C. After the carbon dioxide was absorbed, the absorbent liquid did not undergo phase separation. A first thermal regeneration process was performed on the absorbent liquid using a regeneration tower, followed by a second thermal regeneration process at 120°C using a conventional reboiler, resulting in a residual CO2 of 0.55 mol / L. The resulting lean liquid was returned to the absorption tower for recycling. When the collection rate was 90%, the energy consumption for regeneration was 3.65 GJ / t CO2.

[0088] Comparative Example 7 Composition of the absorbent solution: The mass ratio of the absorbent MEA, the activator 3DMA1P, and the non-aqueous solvent EG is 3:6:1. The amount of absorbent MEA used is 30 wt%, the amount of activator 3DMA1P used is 60 wt%, and the amount of non-aqueous solvent EG used is 10 wt%. No auxiliary agents are added. The total volume of the absorbent solution is 30 L. The viscosity of the absorbent solution (at 25°C) is 12 mPa·s. The pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0089] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase (viscosity (25°C) 350 mPa·s) that had absorbed carbon dioxide.

[0090] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 3.54 mol CO2 / kg. After the first thermal regeneration process was performed on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a conventional reboiler to obtain the first lean liquid phase.

[0091] Subsequently, a portion of the first lean liquid phase (8 wt%) was introduced into a rectification column and rectified at a rectification temperature of 108°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 90%, the energy consumption for regeneration was 2.26 GJ / t CO2.

[0092] Comparative Example 8 Composition of the absorbent solution: The mass ratio of the absorbent 3-aminopropanol, the activator 3-dimethylaminopropylamine, and the non-aqueous solvent EG is 3:6:1. The amount of 3-aminopropanol used is 30 wt%, the amount of 3-dimethylaminopropylamine used is 60 wt%, the amount of EG used is 9.99 wt%, the amount of auxiliary agents used is 0.08 wt‰, the total volume of the absorbent solution is 30 L, the pKa of the absorbent is 9.96, and the LogP value of the activator is -0.1.

[0093] Carbon dioxide was collected using an absorbent liquid in the apparatus shown in Figure 1. Actual exhaust gas containing carbon dioxide (12 v%) was brought into contact with the absorbent liquid, and the contact temperature was stabilized at 40°C to obtain an upper liquid phase and a lower rich liquid phase that had absorbed carbon dioxide.

[0094] Analysis of the carbon dioxide content of the rich liquid phase revealed a maximum absorption capacity of 2.71 mol CO2 / kg. After the first thermal regeneration process was performed on the lower rich liquid phase using a regeneration tower, a second thermal regeneration process was performed at 95°C using a conventional reboiler to obtain the first lean liquid phase.

[0095] Subsequently, a portion of the first lean liquid phase (8 wt%) was introduced into a rectification column and rectified at a rectification temperature of 108°C. The resulting second lean liquid phase was returned, an absorbent was added, and the mixture was recycled. The steam rectified at the top of the rectification column was supplied to the reboiler as part of the heat source. When the carbon dioxide capture efficiency of the lower layer rich liquid was 90%, the energy consumption for regeneration was 2.98 GJ / t CO2.

[0096] Here, the upper liquid phase had a defoaming time of 35 s, the lower rich liquid phase had a defoaming time of 5 s, the lower rich liquid phase had a defoaming time of 15 s after thermal regeneration, and a defoaming time of 7 s after mixing with the upper liquid phase.

[0097] Here, the carbamate salt formed when the absorbent 3-aminopropanol absorbed carbon dioxide had a solubility of 1.38 mol / kg in the activator 3-dimethylaminopropylamine.

[0098] Comparative Example 9 The composition of the absorbent solution was as follows: the mass ratio of the absorbent MEA, the activator N-methyldiethanolamine (MDEA), and the non-aqueous solvent EG was 3:6:1. The amount of MEA used was 30 wt%, the amount of MDEA used was 60 wt%, and the amount of EG used was 10 wt%. The total volume of the absorbent solution was 30 L. The pKa of the absorbent was 9.5, and the LogP value of the activator was -0.72. The absorbent solution was a uniform liquid phase before and after CO2 absorption and did not undergo phase separation.

[0099] Comparative Example 10 The composition of the absorbent solution was as follows: the mass ratio of the absorbent n-butylamine, the activator N-methyldiethanolamine (MDEA), and the non-aqueous solvent EG was 3:6:1. The amount of n-butylamine used was 30 wt%, the amount of MDEA used was 60 wt%, and the amount of EG used was 10 wt%. The total volume of the absorbent solution was 30 L. The pKa of the absorbent was 10.6, and the LogP value of the activator was -0.72. The absorbent solution was a homogeneous liquid phase system before CO2 absorption, and liquid-solid phase separation occurred after CO2 absorption.

[0100] From the above examples and comparative examples, it was found that the non-aqueous absorbent system used in the present invention can undergo phase separation of the solution after absorbing carbon dioxide, and that it is not necessary to raise the regeneration temperature to the boiling point of the non-aqueous solvent. Therefore, it has the significant advantage of lower energy consumption for regeneration compared to conventional organic alcohol amine aqueous systems (Comparative Examples 3 and 4). Furthermore, the complete solution formulation provided in the present invention solves the problems of non-aqueous systems, such as high viscosity and tendency to foam. Compared with Comparative Examples 1 and 2, which do not contain any additives, in all of Examples 1 to 4, additives are added, and the defoaming time of the upper liquid phase, the lower rich liquid phase after thermal regeneration, and the liquid phase after mixing with the upper liquid phase is shortened, and the intake amount of exhaust gas from the absorption tower does not decrease significantly, thus ensuring the carbon dioxide absorption efficiency of the absorbent. When the mass ratio of the absorbent to the activator in the absorbent is greater than 1:1 or less than 1:4 (Comparative Examples 5 and 6), the absorbent cannot undergo phase separation after absorbing carbon dioxide. Therefore, it was found that in the present invention, the mass ratio of the absorbent to the activator is key to achieving phase separation. Compared to Example 1, Comparative Example 7 differs only in that no auxiliary agent was added, but the viscosity of the resulting absorbent solution was significantly higher than that of Example 1, indicating that the auxiliary agent, absorbent, activator, and non-aqueous solvent can synergistically reduce the viscosity of the absorbent solution. In Comparative Example 8, the amount of carbamate formed by absorbing carbon dioxide was significantly greater than 1 mol / kg, and its maximum absorption capacity and energy consumption for regeneration were significantly worse than those of Example 1. This indicates that the phase change absorption effect that the present invention can have cannot be obtained if the relationship between the amounts of absorbent and activator used and the solubility relationship described above are not taken into consideration. Comparative Examples 9 and 10 show that when the pKa value of the absorbent and the LogP value of the activator are not simultaneously within the range described in the claims, a liquid-liquid phase change does not occur after CO2 absorption.

[0101] The proposed partial solvent distillation method solves the problem of water concentration imbalance in existing organic systems used in actual exhaust gas capture, ensuring the continuous and normal operation of the system. Furthermore, the heat of the water vapor produced by rectification can be used as a partial energy supplement for heat regeneration, resulting in the beneficial effect of reducing the energy consumption required to regenerate the absorbent. This has positive significance in reducing the energy consumption and costs of the carbon dioxide capture process.

[0102] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications are possible, including combining individual specific technical features in any appropriate manner, and in order to avoid unnecessary redundancy, various possible combinations of the present invention will not be described separately. However, these simple modifications and combinations should also be considered as part of the disclosure of the present invention and all fall within the scope of protection of the present invention. [Brief explanation of the drawing]

[0103] [Figure 1] This is an apparatus for carrying out the carbon dioxide capture method of the present invention.

Claims

1. A carbon dioxide collection and absorption liquid, wherein the absorption liquid comprises an absorbent, an activator, an auxiliary agent, and a non-aqueous solvent. The absorbent is at least one selected from 3-amino-1-propanol, diglycolamine, monoethanolamine, and diethanolamine. The mass ratio of the absorbent to the activator is 1:1 to 1:

4. The viscosity of the absorbent liquid is 6 to 50 mPa·s. The absorbent liquid is characterized in that the pKa of the absorbent is 8.5 to 10.

2. The aforementioned auxiliary agent is selected from polyethers, preferably from polyoxyethylene ether or polyoxypropylene ether. Preferably, the weight-average molecular weight of the polyoxyethylene ether or polyoxypropylene ether is 3,000 to 5,000 g / mol, more preferably 4,000 to 5,000 g / mol, the absorbent solution according to claim 1.

3. The absorbent liquid according to claim 1 or 2, wherein, based on the total amount of the absorbent liquid, the content of the auxiliary agent in the absorbent liquid is 0.01 to 1 wt‰, preferably 0.05 to 0.5 wt‰.

4. The activator is selected from tertiary amine and / or tertiary amine compositions having a LogP value of -0.1 to 0.6, and is preferably at least one of 3-dimethylamino-1-propanol, diethylethanolamine, 1-dimethylamino-2-propanol, triethanolamine, tetramethylpropylenediamine, tetramethylethylenediamine, and pentamethyldiethylenetriamine. Preferably, the non-aqueous solvent is at least one selected from ethylene glycol, glycerol, 2-propylene glycol, and 1,4-butanediol, the absorbent according to any one of claims 1 to 3.

5. Based on the total amount of the absorbent, the absorbent according to any one of claims 1 to 4, wherein the content of the non-aqueous solvent in the absorbent is 30 wt% or less, preferably 10 to 20 wt%, the content of the absorbent is 10 to 60 wt%, preferably 20 to 35 wt%, and the content of the activator is 10 to 80 wt%, preferably 50 to 70 wt%.

6. The absorbent is CO ２ The absorbent solution according to any one of claims 1 to 5, wherein the carbamate salt formed by absorbing has a solubility of 1 mol / kg or less in the activator.

7. Use of the absorbent liquid according to any one of claims 1 to 6 in the field of carbon dioxide capture.

8. A method for capturing carbon dioxide, wherein the method is Step (1) involves bringing a carbon dioxide-containing gas into contact with an absorbent to obtain an upper liquid phase and a lower rich liquid phase that has absorbed carbon dioxide, Step (2) involves thermally regenerating the rich liquid phase to obtain a first lean liquid phase, The process includes step (3), which involves rectifying a portion of the first lean liquid phase to obtain a second lean liquid phase, and recycling it by returning it to the absorbent liquid of step (1). The method wherein the absorbent is the absorbent described in any one of claims 1 to 7.

9. The method according to claim 8, wherein the contact temperature in step (1) is 30 to 60°C, and the viscosity of the rich liquid phase is 200 to 600 mPa·s.

10. The method according to claim 8 or 9, wherein in step (3), a portion of the second lean liquid phase is 5 to 30 wt% of the second lean liquid phase, the rectification temperature is 105 to 115°C, and the concentration of the outlet water of the rectification column used for rectification is 99.99%.

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