Absorption liquid for capturing carbon dioxide and use thereof, and method for capturing carbon dioxide

Abstract

The present invention relates to the technical field of carbon dioxide capture. Disclosed are an absorption liquid for capturing carbon dioxide and the use thereof, and a method for capturing carbon dioxide. The absorption liquid comprises: an absorbent, an activator, an auxiliary agent, and / or a non-aqueous solvent, wherein the absorbent is selected from at least one of 3-amino-1-propanol, monoethanolamine and diethanolamine. Compared with a traditional phase change absorbent, the absorption liquid has the significant advantages of a low viscosity, a large carbon dioxide absorption capacity, a low regeneration temperature, etc., and has positive significances in reducing the energy consumption and cost during the flue gas carbon dioxide capture process.

Description

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

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202310649622.6 filed on June 2, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] 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

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] Summary of the Invention

[0009] 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.

[0010] 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;

[0011] wherein the absorbent is selected from at least one of 3-amino-1-propanol, diglycolamine, monoethanolamine and diethanolamine;

[0012] Wherein, the mass ratio of the absorbent to the activator is 1:1-1:4;

[0013] Wherein, the viscosity of the absorption liquid is 6-50 mPa·s;

[0014] Wherein, the pKa of the absorbent is 8.5-10.

[0015] 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.

[0016] A third aspect of the present invention provides a method for capturing carbon dioxide, the method comprising:

[0017] (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;

[0018] (2) thermally regenerating the rich liquid phase to obtain a first lean liquid phase;

[0019] (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;

[0020] Wherein, the absorption liquid is the absorption liquid provided by the first aspect of the present invention.

[0021] Through the above technical solution, the present invention has the following beneficial effects:

[0022] (1) Under the synergistic effect of the absorbent, activator, non-aqueous solvent and auxiliary agent, the absorption liquid prepared by the present invention has the advantage of low viscosity (absorption liquid 6-50mPa·s; rich liquid phase 200-600mPa·s). The viscosity of traditional phase change absorbents is mostly above 100mPa·s (above 1000mPa·s for rich liquid phase).

[0023] (2) The mass ratio of the absorbent to the activator in the absorption liquid of the present invention is within the range of 1:1-1:4, which allows the absorption liquid to separate into phases after absorbing carbon dioxide. When the mass ratio is outside the range, the absorption liquid cannot separate into phases.

[0024] (3) Compared with traditional phase change absorbents, the absorption liquid of the present invention also has significant advantages such as large carbon dioxide absorption capacity, regeneration temperature does not need to reach the boiling point of the solvent, and is not easy to foam, which has positive significance for reducing the energy consumption cost in the carbon dioxide capture process.

[0025] (4) 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, thereby causing 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

[0026] FIG1 shows an apparatus for implementing the method for capturing carbon dioxide according to the present invention.

[0027] Explanation of reference numerals 1. Absorption tower; 2. Phase separation tank; 3. Heat exchanger; 4. Regeneration tower; 5. Reboiler; 6. Distillation tower DETAILED DESCRIPTION

[0028] 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.

[0029] 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;

[0030] wherein the absorbent is selected from at least one of 3-amino-1-propanol (3AP), diglycolamine (DGA), monoethanolamine (MEA) and diethanolamine (DEA);

[0031] Wherein, the mass ratio of the absorbent to the activator is 1:1-1:4;

[0032] Wherein, the viscosity of the absorption liquid is 6-50 mPa·s;

[0033] Wherein, the pKa of the absorbent is 8.5-10.

[0034] In order to solve the defect of the absorption liquid in the prior art that the viscosity is greater than that of the aqueous solution due to the presence of organic solvents, and the effect of phase change absorption of carbon dioxide is affected, thereby reducing the absorption and regeneration performance of the absorption liquid, the absorption liquid provided by the present invention is added with an auxiliary agent on the basis of the limited components and amounts to improve the phase change absorption effect and improve the viscosity performance. Preferably, the auxiliary agent is a polyether, preferably selected from polyoxyethylene ether or polyoxypropylene ether; further preferably, the weight average molecular weight of the polyoxyethylene ether or polyoxypropylene ether is 3000-5000 g / mol; more preferably 4000-5000 g / 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, Cas No.9003-11-6, and a weight average molecular weight of 4400 g / mol.

[0035] 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.

[0036] In some preferred embodiments of the present invention, the amount of the auxiliary agent added is preferably 0.01-1wt‰, more preferably 0.05-0.5wt‰. The amount of the auxiliary agent added in the present invention is very low, on the one hand, in order to defoam the rich liquid phase in time; on the other hand, the auxiliary agent can also cooperate with the non-aqueous solvent, absorbent and activator described in the present invention to jointly reduce the viscosity of the absorption liquid and assist in improving the phase change absorption performance of the absorption liquid. In short, within the above-mentioned addition amount range, the absorption liquid provided by the present invention can ensure a reduction in viscosity and provide a better phase separation effect.

[0037] In some preferred embodiments of the present invention, the activator is preferably selected from tertiary amines and / or tertiary amine compositions having 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).

[0038] 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.

[0039] 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%.

[0040] In order 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.

[0041] 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 improve the mass transfer effect of the solution.

[0042] In the present invention, the above-mentioned absorption liquid provided can provide a good phase change absorption effect under limited composition conditions. Preferably, the solubility of the carbamate formed by the absorbent after absorbing CO2 in the activator is not higher than 1 mol / kg. According to the above-mentioned composition of the absorption liquid provided by the present invention, and the above-mentioned solubility relationship between the absorbent and the activator, the technical effect of the present invention in absorbing carbon dioxide by phase change can be provided. When the dosage relationship between the absorbent and the activator and the above-mentioned solubility relationship are not taken into consideration, the phase change absorption effect that can be achieved by the present invention cannot be obtained.

[0043] 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.

[0044] The solubility of the carbamate formed by the absorbent after absorbing CO2 in the activator is not higher than 1 mol / kg.

[0045] 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.

[0046] A third aspect of the present invention provides a method for capturing carbon dioxide, the method comprising:

[0047] (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;

[0048] (2) thermally regenerating the rich liquid phase to obtain a first lean liquid phase;

[0049] (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;

[0050] Wherein, the absorption liquid is the absorption liquid provided by the first aspect of the present invention.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] In some preferred embodiments of the present invention, preferably, the water concentration at the outlet of the distillation tower used in the distillation is 99.99%.

[0057] The above method provided by the present invention can be implemented in the device shown in FIG1 , and the specific process is as follows:

[0058] (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;

[0059] (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;

[0060] (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;

[0061] Wherein, the absorption liquid is the absorption liquid provided by the first aspect of the present invention.

[0062] The present invention is further described below with reference to specific embodiments.

[0063] 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.

[0064] The boiling point of 1,4-butanediol (BDO) is 228°C (0.1 MPa).

[0065] The boiling point of ethylene glycol (EG) is 197.3°C (0.1 MPa).

[0066] Example 1

[0067] 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, the viscosity of the absorption liquid (25°C) is 16mPa·s, the pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0068] In the apparatus shown in Figure 1, an absorbent liquid is used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (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, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 350 mPa·s).

[0069] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.71 mol CO2 / 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.

[0070] A portion of the first lean liquid phase (8 wt% of the first lean liquid phase) was then introduced into a distillation column for distillation at 108°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 90%, the regeneration energy consumption was 2.95 GJ / t CO2.

[0071] 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.

[0072] The solubility of carbamate formed after the absorbent MEA absorbs carbon dioxide in the activator 3DMA1P is 0.77 mol / kg.

[0073] Example 2

[0074] The composition of the absorption liquid is as follows: the mass ratio of absorbent DEA to activator PMDETA is 2:7, the amount of the auxiliary agent is 1 wt‰, the amount of absorbent DEA is 20 wt%, the amount of activator PMDETA is 70 wt%, the non-aqueous solvent BDO accounts for 9.99 wt% of the total absorption liquid mass, the total volume of the absorption liquid is 30 L, the viscosity of the absorption liquid (25°C) is 10 mPa·s, the pKa value of the absorbent is 9.0, and the LogP value of the activator is 0.54.

[0075] In the apparatus shown in Figure 1, an absorbent liquid was used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (volume percent) was brought into contact with the absorbent liquid at a constant temperature of 39.85°C, yielding an upper liquid phase and a lower, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 380 mPa·s).

[0076] 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).

[0077] 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 / t CO2.

[0078] 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.

[0079] Among them, the solubility of carbamate formed after the absorbent DEA absorbs carbon dioxide in the activator PMDETA is 0.65 mol / kg.

[0080] Example 3

[0081] 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, the viscosity of the absorption liquid (25°C) is 12mPa·s, the pKa value of the absorbent is 9.96, and the LogP value of the activator is 0.43.

[0082] In the apparatus shown in Figure 1, an absorbent liquid was used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (volume percent) was brought into contact with the absorbent liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 300 mPa·s).

[0083] 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.

[0084] 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 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 2.22 GJ / t CO2.

[0085] 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.

[0086] Among them, the solubility of carbamate formed after the absorbent 3AP absorbs carbon dioxide in the activator TMPDA is 0.58 mol / kg.

[0087] Example 4

[0088] 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, the viscosity of the absorption liquid (25°C) is 6mPa·s, the pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0089] In the apparatus shown in Figure 1, an absorbent liquid is used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (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, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 280 mPa·s).

[0090] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 4.01 mol CO2 / kg. The lower rich liquid was passed through a regeneration tower for a first thermal regeneration process, and then passed through a high-gravity reboiler for a second thermal regeneration process at 95°C to obtain a first lean liquid phase.

[0091] 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 / t CO2.

[0092] 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.

[0093] Comparative Example 1

[0094] 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, the viscosity of the absorption liquid (25°C) is 19mPa·s, the pKa of the absorbent is 9.0, and the LogP value of the activator is 0.54.

[0095] In the apparatus shown in Figure 1, an absorbent liquid is used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (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, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 320 mPa·s).

[0096] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.69 mol CO2 / 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.

[0097] A portion of the first lean liquid phase (8 wt% of the first lean liquid phase) was then introduced into a distillation column 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 column 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 2.45 GJ / t CO2.

[0098] 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.

[0099] Comparative Example 2

[0100] 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, the viscosity of the absorption liquid (25°C) is 32mPa·s, the pKa of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0101] In the apparatus shown in Figure 1, an absorbent liquid is used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (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, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 250 mPa·s).

[0102] 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.

[0103] 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 105°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 80%, the regeneration energy consumption was 2.57 GJ / t CO2.

[0104] 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.

[0105] Comparative Example 3

[0106] 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.

[0107] In the apparatus shown in Figure 1, an absorbent liquid was used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (v%) was brought into contact with the absorbent liquid at a temperature stabilized at 39.85°C to produce a rich liquid (viscosity (25°C) 10 mPa·s).

[0108] The rich solution was analyzed for CO2 content, revealing a maximum absorption capacity of 2.52 molCO2 / L. After absorbing CO2, the aqueous solution remained intact. After passing through a regeneration tower for a first thermal regeneration process and a second thermal regeneration process in a conventional reboiler at 120°C, 1.29 molCO2 / kg 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.

[0109] 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.

[0110] Comparative Example 4

[0111] 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.

[0112] In the apparatus shown in Figure 1, an absorbent liquid was used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (v%) was brought into contact with the absorbent liquid at a constant temperature of 40°C to produce a rich liquid (viscosity (25°C) 280 mPa·s).

[0113] 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, a residual 0.56 mol CO2 / kg 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 / t CO2.

[0114] 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.

[0115] Comparative Example 5

[0116] The composition of the absorption liquid: the mass ratio of absorbent MEA, activator 3DMA1P and non-aqueous solvent EG is 1:6:1, the amount of absorbent MEA is 12.5wt%, the amount of activator 3DMA1P is 75wt%, the amount of non-aqueous solvent EG is 12.5wt%, 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.

[0117] The apparatus shown in Figure 1 uses an absorption liquid to capture carbon dioxide. Real flue gas containing 12% CO2 by volume is contacted with the absorption liquid at a constant temperature of 40°C. After absorbing the CO2, the absorption liquid undergoes no phase separation. After a first thermal regeneration process in a regeneration tower and a second thermal regeneration process in a conventional reboiler at 120°C, the residual CO2 content is 0.47 molCO2 / kg. The resulting lean liquid is returned to the absorption tower for recycling. When the capture rate is 90%, the regeneration energy consumption is 3.63 GJ / tCO2.

[0118] Comparative Example 6

[0119] The composition of the absorption liquid: the mass ratio of absorbent MEA, activator 3DMA1P and non-aqueous solvent EG is 3:1:1, the amount of absorbent MEA is 60wt%, the amount of activator 3DMA1P is 20wt%, the amount of non-aqueous solvent EG is 20wt%, 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.

[0120] The apparatus shown in Figure 1 uses an absorption liquid for carbon dioxide capture. Real flue gas containing 12% CO2 (volume percent) is contacted with the absorption liquid at a constant temperature of 40°C. After absorbing the CO2, the absorption liquid undergoes no phase separation. After a first thermal regeneration process in a regeneration tower and a second thermal regeneration process in a conventional reboiler at 120°C, a residual 0.55 molCO2 / L remains. The resulting lean liquid is returned to the absorption tower for recycling. When the capture rate reaches 90%, the regeneration energy consumption is 3.65 GJ / t CO2.

[0121] Comparative Example 7

[0122] 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 10wt%, no auxiliary agent is added, the total volume of the absorption liquid is 30L, the viscosity of the absorption liquid (25°C) is 12mPa·s, the pKa value of the absorbent is 9.5, and the LogP value of the activator is -0.1.

[0123] In the apparatus shown in Figure 1, an absorbent liquid is used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (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, carbon dioxide-absorbed, liquid-rich phase (viscosity (25°C) 350 mPa·s).

[0124] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 3.54 mol CO2 / 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.

[0125] A portion of the first lean liquid phase (8 wt% of the first lean liquid phase) was then introduced into a distillation tower for distillation at 108°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 90%, the regeneration energy consumption was 2.26 GJ / t CO2.

[0126] Comparative Example 8

[0127] The composition of the absorption liquid: 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 the absorbent 3-aminopropanol is 30wt%, the amount of the activator 3-dimethylaminopropylamine is 60wt%, the amount of the non-aqueous solvent EG is 9.99wt%, the amount of the auxiliary agent is 0.08wt‰, the total volume of the absorption liquid is 30L, the pKa of the absorbent is 9.96, and the LogP value of the activator is -0.1.

[0128] In the apparatus shown in Figure 1, an absorption liquid is used to capture carbon dioxide. Real flue gas containing 12% carbon dioxide (v%) is brought into contact with the absorption liquid at a constant temperature of 40°C, yielding an upper liquid phase and a lower, carbon dioxide-absorbed, liquid-rich phase.

[0129] The rich liquid phase was analyzed for carbon dioxide content, and the maximum absorption capacity was 2.71 mol CO2 / 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.

[0130] A portion of the first lean liquid phase (8 wt% of the first lean liquid phase) was then introduced into a distillation column for distillation at 108°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 90%, the regeneration energy consumption was 2.98 GJ / t CO2.

[0131] 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.

[0132] The solubility of carbamate formed after the absorbent 3-aminopropanol absorbs carbon dioxide in the activator 3-dimethylaminopropylamine is 1.38 mol / kg.

[0133] Comparative Example 9

[0134] The composition of the absorption liquid: the mass ratio of absorbent MEA, activator N-methyldiethanolamine (MDEA) and non-aqueous solvent EG is 3:6:1, the amount of absorbent MEA is 30wt%, the amount of activator MDEA is 60wt%, the amount of non-aqueous solvent EG is 10wt%, the total volume of the absorption liquid is 30L, the pKa of the absorbent is 9.5, the LogP value of the activator is -0.72, and the absorption liquid is a uniform liquid phase before and after absorbing CO2, without phase separation.

[0135] Comparative Example 10

[0136] The composition of the absorption liquid: the mass ratio of absorbent n-butylamine, activator N-methyldiethanolamine (MDEA) and non-aqueous solvent EG is 3:6:1, the amount of absorbent n-butylamine is 30wt%, the amount of activator MDEA is 60wt%, the amount of non-aqueous solvent EG is 10wt%, the total volume of the absorption liquid is 30L, the pKa of the absorbent is 10.6, the LogP value of the activator is -0.72, the absorption liquid is a uniform liquid phase system before absorbing CO2, and liquid-solid phase separation is produced after absorbing CO2.

[0137] As can be seen from the above-described embodiments and comparative examples, the non-aqueous absorption liquid system used in the present application absorbs carbon dioxide and the solution can be phase-split, and regeneration temperature does not need to reach the boiling point of non-aqueous solvent, therefore compared with traditional organic alcohol amine water system (comparative examples 3, 4), there is the remarkable advantage that regeneration energy consumption is low, while the complete solution formula provided by the present invention solves the problems such as non-aqueous system viscosity is large, easy to foam, compared with comparative example 1, 2 without adding auxiliary agent, embodiment 1-4 all adds auxiliary agent after, after the thermal regeneration of upper liquid phase, lower floor's rich liquid phase and the defoaming time after it is mixed with upper liquid phase all is shorter, so that the flue gas intake of absorption tower will not significantly decline, it is ensured that the efficiency of absorption liquid absorption carbon dioxide. When the mass ratio of the absorbent in the absorption liquid and activator is greater than 1: 1 or less than 1: 4 (comparative examples 5, 6), the absorption liquid cannot phase-split after absorbing carbon dioxide, therefore it can be seen that the mass ratio of absorbent of the present invention and activator is the key of whether phase-splitting. Comparative Example 7 differs from Example 1 only in that no additive is added, yet the resulting absorption liquid has a significantly greater viscosity than Example 1, indicating that the additive, absorbent, activator, and non-aqueous solvent can synergistically reduce the viscosity of the absorption liquid. The carbamate formed by absorbing carbon dioxide in Comparative Example 8 is significantly greater than 1 mol / kg, and its maximum absorption capacity and regeneration energy consumption are significantly lower than those of Example 1, indicating that the phase change absorption effect achieved by the present invention cannot be achieved without considering the dosage relationship between the absorbent and activator and the aforementioned solubility relationship. Comparative Examples 9 and 10 show that when the absorbent pKa value and the activator LogP value are not both within the claimed range, no liquid-liquid phase transition can occur after CO2 absorption.

[0138] 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.

[0139] 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 absorbent liquid for capturing carbon dioxide, It is characterized in that The absorption liquid comprises: 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 mass ratio of the absorbent to the activator is 1:1-1:4; Wherein, the viscosity of the absorption liquid is 6-50mPa·s; Wherein, the pKa of the absorbent is 8.5-10.

2. The absorbing liquid according to claim 1, in, The auxiliary agent is selected from polyethers, preferably polyoxyethylene ethers or polyoxypropylene ethers; Preferably, the weight average molecular weight of the polyoxyethylene ether or polyoxypropylene ether is 3000-5000 g / mol; more preferably 4000-5000 g / mol.

3. The absorbing liquid according to claim 1 or 2, in, Based on the total amount of the absorption liquid, the content of the auxiliary agent in the absorption liquid is 0.01-1wt‰, preferably 0.05-0.5wt‰.

4. The absorption liquid according to any one of claims 1 to 3, in, The activator is selected from tertiary amines and / or tertiary amine compositions having a LogP value of -0.1 to 0.6, 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.

5. The absorption liquid according to any one of claims 1 to 4, in, Based on the total amount of the absorption liquid, the content of the non-aqueous solvent in the absorption liquid is not higher than 30wt%, preferably 10-20wt%; the content of the absorbent is 10-60wt%, preferably 20-35wt%; the content of the activator is 10-80wt%, preferably 50-70wt%.

6. The absorption liquid according to any one of claims 1 to 5, in, The absorbent absorbs CO 2 The solubility of the carbamate formed in the activator is not higher than 1 mol / kg.

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: include: (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; (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 described in any one of claims 1-7.

9. The method according to claim 8, in, 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 or 9, in, In step (3), a portion of the second lean liquid phase is 5-30 wt% of the second lean liquid phase; the distillation temperature is 105-115° C.; and the water concentration at the outlet of the distillation tower used in the distillation is 99.99%.

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