Absorbent liquid for capturing carbon dioxide, application thereof, and method for capturing carbon dioxide

Abstract

The present invention relates to the field of carbon dioxide capture technology, and discloses a carbon dioxide capture absorption liquid and its application and carbon dioxide capture method. The absorption liquid comprises an absorbent, an activator, an auxiliary agent, and / or a non-aqueous solvent; the absorbent is selected from at least one of 3-amino-1-propanol, monoethanolamine, and diethanolamine. Compared with traditional phase-change absorbents, the absorption liquid has significant advantages such as low viscosity, high carbon dioxide absorption capacity, and low regeneration temperature, and is beneficial for reducing energy consumption and costs in the flue gas carbon dioxide capture process.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide capture, and in particular relates to an absorption liquid for capturing carbon dioxide and a method for applying and capturing carbon dioxide. Background Art

[0002] The existing mature chemical absorption technology for removing carbon dioxide, which has been used on a pilot scale and in industrialization, uses ethanolamine (MEA) as an absorbent to capture carbon dioxide. However, the high energy consumption of MEA regeneration (3.7-4.2 GJ / tCO2) and the high capture cost have restricted its subsequent development.

[0003] In order to improve the absorption and desorption performance of the absorption liquid, effectively reduce the desorption energy consumption, and save the capture cost, the current work is mainly carried out in two aspects: new absorbent development and process improvement or new process research.

[0004] Absorbents that undergo phase separation during or after CO2 absorption are generally referred to as phase-change absorbers. In a phase-change absorption system, CO2 absorption forms a CO2-lean phase and a CO2-rich phase. By heating and regenerating only the CO2-rich phase, the system's regeneration energy consumption is reduced, making this a promising low-energy CO2 capture technology.

[0005] Currently, phase-change absorbents have several drawbacks that restrict their large-scale operation. Therefore, there is a need to provide an absorbent that can capture carbon dioxide using phase separation. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the conventional process of capturing carbon dioxide using an organic amine solution system absorbent, such as high energy consumption for solvent regeneration, the need for the regeneration temperature to reach the boiling point of the solvent, high viscosity of the absorption liquid, small carbon dioxide absorption capacity, and easy foaming, and to provide an absorption liquid for capturing carbon dioxide and a method for its application and capture of carbon dioxide.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides an absorption liquid for capturing carbon dioxide, wherein the absorption liquid comprises: an absorbent, an activator, an auxiliary agent and a non-aqueous solvent;

[0008] Wherein, the absorbent is selected from at least one of 3-amino-1-propanol, diglycolamine, monoethanolamine and diethanolamine.

[0009] The second aspect of the present invention provides use of the absorption liquid provided by 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 comprising:

[0011] (1) contacting the carbon dioxide-containing gas with an absorbing liquid phase to obtain an upper liquid phase and a lower liquid phase rich in carbon dioxide;

[0012] (2) thermally regenerating the rich liquid phase to obtain a first lean liquid phase;

[0013] (3) distilling a portion of the first lean liquid phase to obtain a second lean liquid phase which is returned to the absorption liquid in step (1) for recycling;

[0014] Wherein, the absorption liquid is the absorption liquid provided by the first aspect of the present invention.

[0015] Through the above technical solution, the absorption liquid prepared by the present invention has the advantage of low viscosity (6-50mPa·s for the absorption liquid; 200-600mPa·s for the rich liquid phase). The viscosity of traditional phase-change absorbents is mostly above 100mPa·s (above 1000mPa·s for the rich liquid phase). In addition, compared with traditional phase-change absorbents, the absorption liquid of the present invention also has significant advantages such as large carbon dioxide absorption capacity, phase separation after absorbing carbon dioxide, the regeneration temperature does not need to reach the boiling point of the solvent, and it is not easy to foam, which has positive significance for reducing the energy consumption cost in the carbon dioxide capture process.

[0016] At the same time, the present invention also solves the problem that when the real flue gas contains about 8% water, the water will also be absorbed by the non-aqueous solvent during the carbon dioxide capture process, but the regeneration temperature of the non-aqueous system does not reach the water vapor generation temperature, thus leading to the accumulation of water content in the non-aqueous system, that is, the dynamic imbalance of water in the non-aqueous solvent system. That is, the process proposed by the present invention can maintain the dynamic balance of the non-aqueous system, and can use the water vapor generated by distillation as part of the heat source of the reboiler, thereby achieving energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A device for implementing the method for capturing carbon dioxide of the present invention.

[0018] Description of Reference Numerals

[0019] 1. Absorption tower; 2. Phase separation tank; 3. Heat exchanger; 4. Regeneration tower; 5. Reboiler; 6. Distillation tower DETAILED DESCRIPTION

[0020] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0021] A first aspect of the present invention provides an absorption liquid for capturing carbon dioxide, wherein the absorption liquid comprises: an absorbent, an activator, an auxiliary agent, and a non-aqueous solvent;

[0022] Wherein, the absorbent is selected from at least one of 3-amino-1-propanol (3AP), diglycolamine (DGA), monoethanolamine (MEA) and diethanolamine (DEA).

[0023] In order to solve the problem that the absorption liquid in the prior art has a higher viscosity and is easy to foam compared to the aqueous solution due to the presence of organic solvents, thereby affecting the absorption and regeneration performance of the absorption liquid, the absorption liquid provided by the present invention is added with an auxiliary agent, wherein the auxiliary agent is selected from 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 3000-5000g / mol. The polyether can be commercially obtained, such as poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) from Aladdin Chemical Reagent Co., Ltd., with a product number of P131344, CasNo.9003-11-6, and a weight average molecular weight of 4400g / mol.

[0024] After adding the additive, the defoaming time of the upper liquid phase obtained after the absorption liquid absorbs carbon dioxide is 30-70 seconds, and the defoaming time of the lower rich liquid phase is 1-8 seconds; the defoaming time of the lower rich liquid phase after thermal regeneration is 8-30 seconds, and the defoaming time after mixing with the upper liquid phase is 6-20 seconds. In contrast, the defoaming time of the upper liquid phase obtained after absorbing carbon dioxide in the prior art without the additive is 100-500 seconds, and the defoaming time of the lower rich liquid phase is 1-5 seconds; the defoaming time of the lower rich liquid phase after thermal regeneration is 30-60 seconds, and the defoaming time after mixing with the upper liquid phase is 30-60 seconds.

[0025] In some preferred embodiments of the present invention, the amount of the auxiliary agent added is preferably 0.01-1 wt‰, more preferably 0.05-0.5 wt‰. Within the above addition amount range, the absorption liquid provided by the present invention can ensure reduced viscosity and is not prone to foaming during the capture method.

[0026] In some preferred embodiments of the present invention, preferably, the activator is selected from 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).

[0027] The solubility of the carbamate formed by the absorbent after absorbing CO2 in the activator is not higher than 1 mol / kg.

[0028] In some preferred embodiments of the present invention, the non-aqueous solvent is preferably selected from at least one of ethylene glycol (EG), glycerol (GL), 2-propylene glycol (12P) and 1,4-butanediol (BDO), which can reduce the energy consumption of solvent regeneration in the traditional process of capturing carbon dioxide using an organic amine solution system absorbent. The use of a non-aqueous solvent instead of water can, on the one hand, reduce the viscosity of the rich solution, and on the other hand, avoid the latent heat consumption of the solvent during regeneration.

[0029] In some preferred embodiments of the present invention, preferably, based on the total amount of the absorption liquid, the content of the non-aqueous solvent is not higher than 30 wt%, preferably 10-20 wt%.The content of the absorbent is 10-60 wt%, preferably 20-35 wt%.

[0030] To improve the absorption performance of the absorption liquid, the tertiary amine is used as an activator, and its content is 10-80wt%, preferably 50-70wt%, based on the total amount of the absorption liquid. The mass ratio of the absorbent to the activator is 2:1-1:10, preferably 1:1-1:4.

[0031] The solubility of the carbamate formed after the absorbent absorbs CO2 in the activator is less than 1 mol / kg, and the viscosity of the absorption liquid is 6-50 mPa·s (25°C). Reducing the viscosity can improve the fluidity of the solution and also enhance the mass transfer effect of the solution.

[0032] After absorbing CO2, the absorption liquid forms two liquid phases, one above the other, with a significantly different CO2 loading. Almost all of the CO2 is concentrated in the lower phase. After separation, the upper phase is directly recycled. The lower, CO2-rich phase is thermally regenerated, and the resulting lean phase is recycled and combined with the upper phase for reuse. Compared to traditional chemical absorption methods, the phase separation process of the present invention can reduce the amount of liquid entering thermal regeneration for the same CO2 removal rate, thereby reducing regeneration energy consumption.

[0033] The second aspect of the present invention provides use of the absorption liquid provided by the first aspect of the present invention in the field of carbon dioxide capture.

[0034] A third aspect of the present invention provides a method for capturing carbon dioxide, the method comprising:

[0035] (1) contacting the carbon dioxide-containing gas with an absorbing liquid phase to obtain an upper liquid phase and a lower liquid phase rich in carbon dioxide;

[0036] (2) thermally regenerating the rich liquid phase to obtain a first lean liquid phase;

[0037] (3) distilling a portion of the first lean liquid phase to obtain a second lean liquid phase which is returned to the absorption tower in the absorption liquid of step (1) for recycling;

[0038] Wherein, the absorption liquid is the absorption liquid provided by the first aspect of the present invention.

[0039] In some preferred embodiments of the present invention, the thermal regeneration process in step (2) is preferably: first performing a first thermal regeneration process, and then performing a second thermal regeneration process. The apparatus for the first thermal regeneration process is a regeneration tower, and the apparatus for the second thermal regeneration process is a reboiler, preferably selected from a conventional reboiler, a supergravity reboiler, or a falling film reboiler. In the present invention, the regeneration temperature may be lower than the regeneration temperature of the non-aqueous solvent.

[0040] In some preferred embodiments of the present invention, preferably, the water vapor generated by the rectification is used as a part of the heat source of the reboiler.

[0041] In some preferred embodiments of the present invention, preferably, the contact temperature in step (1) is 30-60° C.; and the viscosity of the rich liquid phase (at 25° C.) is 200-600 mPa·s.

[0042] In some preferred embodiments of the present invention, preferably, in step (2), the temperature of the second thermal regeneration process is 85-105°C, more preferably 90-100°C.

[0043] In some preferred embodiments of the present invention, preferably, in step (3), a portion of the first lean liquid phase is 5-30 wt% of the first lean liquid phase; and the distillation temperature is 105-115°C.

[0044] The above method provided by the present invention can be Figure 1 The specific process is as follows:

[0045] (1) introducing carbon dioxide-containing gas into an absorption tower 1 to contact with an absorption liquid therein, and then introducing the absorption liquid into a phase separation tank 2 to obtain an upper liquid phase and a lower liquid phase rich in carbon dioxide;

[0046] (2) introducing the rich liquid phase in step (1) into a regeneration tower 4 and a reboiler 5 in sequence through a heat exchanger 3 for thermal regeneration to obtain a first lean liquid phase;

[0047] (3) a portion of the first lean liquid phase is introduced into a distillation tower 6 for distillation to obtain a second lean liquid phase which is returned to the absorption liquid in step (1) in the absorption tower 1 for recycling;

[0048] Wherein, the absorption liquid is the absorption liquid provided by the first aspect of the present invention.

[0049] The present invention is further described below with reference to specific embodiments.

[0050] The auxiliary agent, 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 Reagent Co., Ltd.

[0051] The boiling point of 1,4-butanediol (BDO) is 228°C (0.1 MPa).

[0052] The boiling point of ethylene glycol (EG) is 197.3°C (0.1 MPa).

[0053] Example 1

[0054] The composition of the absorption liquid: the mass ratio of absorbent MEA, activator 3DMA1P and non-aqueous solvent EG is 3:6:1, the amount of absorbent MEA is 30wt%, the amount of activator 3DMA1P is 60wt%, the amount of non-aqueous solvent EG is 9.92wt%, the amount of auxiliary agent is 0.08wt‰, the total volume of the absorption liquid is 30L, and the viscosity of the absorption liquid (25℃) is 12mPa·s.

[0055] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, CO2-rich liquid phase (viscosity (25°C) 350 mPa·s).

[0056] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.71 molCO2 / kg. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a conventional reboiler for a second thermal regeneration process at 95°C to obtain a first lean liquid phase.

[0057] A portion of the first lean liquid phase (8 wt% of the first lean liquid phase) is then introduced into a distillation column for distillation at 108°C. The resulting second lean liquid phase is then recycled and added to the absorbent. The steam from the distillation overhead is partially supplied to the reboiler as a heat source. When the carbon dioxide capture efficiency of the lower rich liquid layer is 90%, the regeneration energy consumption is 2.95 GJ / tCO2.

[0058] Among them, the defoaming time of the upper liquid phase is 35s, and the defoaming time of the lower rich liquid phase is 5s; the defoaming time of the lower rich liquid phase after thermal regeneration is 15s, and the defoaming time after mixing with the upper liquid phase is 7s.

[0059] Example 2

[0060] Composition of the absorption liquid: the mass ratio of absorbent DEA to activator PMDETA is 2:7, the amount of auxiliary agent is 1wt‰, the amount of absorbent DEA is 20wt%, the amount of activator PMDETA is 70wt%, the non-aqueous solvent BDO accounts for 9.99wt% of the total absorption liquid mass, the total volume of the absorption liquid is 30L, and the viscosity of the absorption liquid (25℃) is 10mPa·s.

[0061] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 39.85°C, yielding an upper liquid phase and a lower, CO2-rich liquid phase (viscosity (25°C) 380 mPa·s).

[0062] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.78 molCO2 / kg. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a conventional reboiler for a second thermal regeneration process at 100°C to obtain a first lean liquid phase (containing a residual 0.26 molCO2 / kg).

[0063] A portion of the first lean liquid phase (10 wt% of the first lean liquid phase) was then introduced into a distillation tower for distillation at 110°C. The resulting second lean liquid phase was then recycled and added to the absorbent. The steam from the top of the distillation tower was partially supplied to the reboiler as a heat source. When the carbon dioxide capture efficiency of the lower rich liquid layer was 80%, the regeneration energy consumption was 2.48 GJ / tCO2.

[0064] Among them, the defoaming time of the upper liquid phase is 40s, and the defoaming time of the lower rich liquid phase is 5s; the defoaming time of the lower rich liquid phase after thermal regeneration is 10s, and the defoaming time after mixing with the upper liquid phase is 8s.

[0065] Example 3

[0066] The composition of the absorption liquid is as follows: the mass ratio of absorbent 3AP to activator TMPDA is 1:3, the amount of absorbent 3AP is 22.5wt%, the amount of activator TMPDA is 67.5wt%, the non-aqueous solvent GL accounts for 10% of the total solution mass, the amount of additive added is 0.1‰wt, the total volume of the absorption liquid is 30L, and the viscosity of the absorption liquid (25℃) is 12mPa·s.

[0067] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, CO2-rich liquid phase (viscosity (25°C) 300 mPa·s).

[0068] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.75 molCO2 / L. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a conventional reboiler for a second thermal regeneration process at 95°C to obtain a first lean liquid phase.

[0069] A portion of the first lean liquid phase (5 wt% of the first lean liquid phase) was then introduced into a distillation column for distillation at 110°C. The resulting second lean liquid phase was then recycled and added to the absorbent. The steam from the distillation overhead was partially supplied to the reboiler as a heat source. When the carbon dioxide capture efficiency of the lower rich liquid layer was 80%, the regeneration energy consumption was 2.22 GJ / tCO2.

[0070] Among them, the defoaming time of the upper liquid phase is 42s, and the defoaming time of the lower rich liquid phase is 4s; the defoaming time of the lower rich liquid phase after thermal regeneration is 14s, and the defoaming time after mixing with the upper liquid phase is 15s.

[0071] Example 4

[0072] The composition of the absorption liquid is as follows: the mass ratio of absorbent MEA to activator 3DMA1P is 2:6, the amount of absorbent MEA is 20wt%, the amount of activator 3DMA1P is 60wt%, the amount of non-aqueous solvent EG is 19.999wt%, the amount of auxiliary agent is 0.1‰wt, the total volume of the absorption liquid is 30L, and the viscosity of the absorption liquid (25°C) is 6mPa·s.

[0073] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, CO2-rich liquid phase (viscosity (25°C) 280 mPa·s).

[0074] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 4.01 molCO2 / kg. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a supergravity reboiler for a second thermal regeneration process at 95°C to obtain a first lean liquid phase.

[0075] A portion of the first lean liquid phase (10 wt% of the first lean liquid phase) was then introduced into a distillation column for distillation at 110°C. The resulting second lean liquid phase was then recycled and added to the absorbent. The steam from the top of the distillation column was partially supplied to the reboiler as a heat source. When the carbon dioxide capture efficiency of the lower rich liquid layer was 82.5%, the regeneration energy consumption was 2.76 GJ / tCO2.

[0076] Among them, the defoaming time of the upper liquid phase is 40s, and the defoaming time of the lower rich liquid phase is 5s; the defoaming time of the lower rich liquid phase after thermal regeneration is 10s, and the defoaming time after mixing with the upper liquid phase is 10s.

[0077] Comparative Example 1

[0078] The composition of the absorption liquid: the mass ratio of absorbent DEA to activator PMDETA is 3:6, the amount of absorbent DEA is 30wt%, the amount of activator PMDETA is 60wt%, the amount of non-aqueous solvent EG is 10wt%, no auxiliary agent is added, the total volume of the absorption liquid is 30L, and the viscosity of the absorption liquid (25°C) is 9mPa·s.

[0079] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, CO2-rich liquid phase (viscosity (25°C) 320 mPa·s).

[0080] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.69 molCO2 / kg. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a conventional reboiler for a second thermal regeneration process at 95°C to obtain a first lean liquid phase.

[0081] A portion of the first lean liquid phase (8 wt% of the first lean liquid phase) is then introduced into a distillation tower for distillation at 105°C. The resulting second lean liquid phase is then recycled and added to the absorbent. The steam from the distillation overhead is partially supplied to the reboiler as a heat source. When the carbon dioxide capture efficiency of the lower rich liquid layer is 80%, the regeneration energy consumption is 2.45 GJ / tCO2.

[0082] Among them, the defoaming time of the upper liquid phase is 120s, and the defoaming time of the lower rich liquid phase is 4s; the defoaming time of the lower rich liquid phase after thermal regeneration is 50s, and the defoaming time after mixing with the upper liquid phase is 45s.

[0083] Comparative Example 2

[0084] The composition of the absorption liquid is as follows: the mass ratio of absorbent MEA to activator 3DMA1P is 1:1, the amount of absorbent MEA is 40wt%, the amount of activator 3DMA1P is 40wt%, the non-aqueous solvent EG accounts for 20%wt of the total solution mass, no auxiliary agent is added, the total volume of the absorption liquid is 30L, and the viscosity of the absorption liquid (25°C) is 6mPa·s.

[0085] exist Figure 1The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, CO2-rich liquid phase (viscosity (25°C) 250 mPa·s).

[0086] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.55 molCO2 / L. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a conventional reboiler for a second thermal regeneration process at 95°C to obtain a first lean liquid phase.

[0087] A portion of the first lean liquid phase (5 wt% of the first lean liquid phase) was then introduced into a distillation tower for distillation at 105°C. The resulting second lean liquid phase was then recycled and added to the absorbent. The steam from the top of the distillation tower was partially supplied to the reboiler as a heat source. When the carbon dioxide capture efficiency of the lower rich liquid layer was 80%, the regeneration energy consumption was 2.57 GJ / tCO2.

[0088] Among them, the defoaming time of the upper liquid phase is 130s, and the defoaming time of the lower rich liquid phase is 4s; the defoaming time of the lower rich liquid phase after thermal regeneration is 50s, and the defoaming time after mixing with the upper liquid phase is 50s.

[0089] Comparative Example 3

[0090] The absorption liquid is 30 L of a 305.4 g / L MEA aqueous solution, and the viscosity of the absorption liquid (25° C.) is 1 mPa·s.

[0091] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is brought into contact with the absorbent liquid at a constant temperature of 39.85°C to produce a rich liquid (viscosity (25°C) 10 mPa·s).

[0092] The rich solution was analyzed for carbon dioxide content, revealing a maximum absorption capacity of 2.52 molCO₂ / L. After absorbing the carbon dioxide, the aqueous solution remained intact. After passing through a regeneration tower for a first thermal regeneration process and a second thermal regeneration process at 120°C in a conventional reboiler, 1.29 molCO₂ / L remained. The resulting lean solution was returned to the absorption tower for recycling. At a capture efficiency of 90%, the regeneration energy consumption was 5.1 GJ / tCO₂.

[0093] The defoaming time of the rich liquid phase is 5 seconds, and the defoaming time of the rich liquid phase after thermal regeneration is 6 seconds.

[0094] Comparative Example 4

[0095] The absorption liquid is 30 L of a 305.4 g / L MEA aqueous solution, and the viscosity of the absorption liquid (25° C.) is 1 mPa·s.

[0096] exist Figure 1 The device shown uses an absorbent liquid for CO2 capture. Real flue gas containing 12% CO2 (volume percent) is contacted with the absorbent liquid at a constant temperature of 40°C to produce a rich liquid (viscosity (25°C) 280 mPa·s).

[0097] After absorbing CO2, the aqueous solution remained phase-separated. After a first thermal regeneration process in a regeneration tower and a second thermal regeneration process in a conventional reboiler at 115°C, 1.29 molCO2 / kg of residual CO2 remained. The resulting lean solution was returned to the absorption tower for recycling. At an 80% capture efficiency, the regeneration energy consumption was 4.25 GJ / tCO2.

[0098] The defoaming time of the rich liquid phase is 5 seconds, and the defoaming time of the rich liquid phase after thermal regeneration is 6 seconds.

[0099] It can be seen from the above embodiments and comparative examples that the non-aqueous absorption liquid system used in the present application can separate the solution into phases after absorbing carbon dioxide, and the regeneration temperature does not need to reach the boiling point of the non-aqueous solvent. Therefore, compared with the traditional organic alcohol amine water system (Comparative Examples 3 and 4), it has the significant advantage of low regeneration energy consumption. At the same time, the complete solution formula provided by the present invention solves the problems of high viscosity and easy foaming of the non-aqueous system. Compared with Comparative Examples 1 and 2 without additives, Examples 1-4 all add additives. After the thermal regeneration of the upper liquid phase and the lower rich liquid phase and after mixing with the upper liquid phase, the defoaming time is shorter, so that the flue gas intake of the absorption tower will not decrease significantly, thereby ensuring the efficiency of the absorption liquid in absorbing carbon dioxide.

[0100] The proposed partial solvent distillation method solves the problem of water enrichment imbalance in existing organic systems used in real flue gas capture, ensuring continuous and normal operation of the system. Furthermore, the heat generated by the distillation vapor is used as a partial energy supplement for thermal regeneration, which has the beneficial effect of reducing the energy consumption of absorbent regeneration. This has a positive impact on reducing the energy consumption of the carbon dioxide capture process.

[0101] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple variations and combinations should also be considered as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. An absorption liquid for capturing carbon dioxide, characterized in that: The absorption liquid includes: an absorbent, an activator, an auxiliary agent and a non-aqueous solvent; wherein the absorbent is selected from at least one of 3-amino-1-propanol, diglycolamine, monoethanolamine and diethanolamine; Wherein, the auxiliary agent is selected from polyether; Wherein, the polyether is selected from polyoxyethylene ether or polyoxypropylene ether; Wherein, the weight average molecular weight of the polyoxyethylene ether or polyoxypropylene ether is 3000-5000 g / mol; Wherein, based on the total amount of the absorption liquid, the content of the auxiliary agent in the absorption liquid is 0.01-1wt‰; wherein the activator is selected from at least one of 3-dimethylamino-1-propanol, diethylethanolamine, 1-dimethylamino-2-propanol, triethanolamine, tetramethylpropylenediamine, tetramethylethylenediamine and pentamethyldiethylenetriamine; Wherein, the non-aqueous solvent is selected from at least one of ethylene glycol, glycerol, 2-propylene glycol and 1,4-butanediol; Wherein, the viscosity of the absorption liquid is 6-50 mPa·s.

2. The absorption liquid according to claim 1, wherein Based on the total amount of the absorption liquid, the content of the auxiliary agent in the absorption liquid is 0.05-0.5wt‰.

3. The absorption liquid according to claim 1, wherein Based on the total amount of the absorption liquid, in the absorption liquid, the content of the non-aqueous solvent is not higher than 30 wt %; the content of the absorbent is 10-60 wt %; and the content of the activator is 10-80 wt %.

4. The absorption liquid according to claim 3, wherein Based on the total amount of the absorption liquid, the content of the non-aqueous solvent in the absorption liquid is 10-20 wt %; the content of the absorbent is 20-35 wt %; and the content of the activator is 50-70 wt %.

5. The absorption liquid according to claim 1, wherein The mass ratio of the absorbent to the activator is 2:1-1:

10. The absorbing liquid according to claim 5, wherein The mass ratio of the absorbent to the activator is 1:1-1:

4.

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

8. A method for capturing carbon dioxide, the method comprising: (1) contacting the carbon dioxide-containing gas with the absorbing liquid phase to obtain an upper liquid phase and a lower liquid phase rich in carbon dioxide; (2) thermally regenerating the rich liquid phase to obtain a first lean liquid phase; (3) distilling a portion of the first lean liquid phase to obtain a second lean liquid phase which is returned to the absorption liquid in step (1) for recycling; Wherein, the absorption liquid is the absorption liquid according to any one of claims 1 to 6.

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

10. The method according to claim 8, wherein In step (3), the portion of the second lean liquid phase is 5-30 wt% of the second lean liquid phase; and the distillation temperature is 105-115°C.

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