Low temperature regeneration non-aqueous absorbent for carbon dioxide capture

Abstract

The application discloses a low-temperature regeneration non-aqueous phase absorbent for carbon dioxide capture, and belongs to the technical field of carbon dioxide capture and separation, which is mainly composed of a steric hindrance amine and an organic solvent, wherein the steric hindrance amine is an absorption component, and the molar concentration is 1-5 mol / L; the organic solution is used as a solvent and participates in the reaction at the same time. The non-aqueous phase absorption system prepared by the application can realize low-temperature and high-efficiency regeneration of the absorbent without adding any catalyst, and meanwhile, the system has higher absorption rate and CO2 load. The low-temperature regeneration absorbent can realize utilization of low-grade heat of a power plant, thereby greatly reducing the power generation cost of the power plant with the added carbon capture system, and laying a foundation for further popularization of the carbon capture system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon dioxide capture and separation, and particularly relates to a low-temperature regeneration non-aqueous phase absorbent for carbon dioxide capture. BACKGROUND

[0002] Carbon capture and storage technology (CCUS) is an effective CO2 capture technology for fixed CO2 emission sources such as thermal power generation, steelmaking, and limestone calcination. Among them, the organic amine absorbent is the most widely used chemical absorbent in industry at present. However, the current organic amine absorbent has high regeneration energy consumption, which limits its further promotion.

[0003] The regeneration energy consumption of the absorbent is mainly composed of three parts, namely the reaction heat of the absorbent and CO2, the sensible heat for heating the absorbent, and the latent heat caused by the partial evaporation of the absorbent. At present, the regeneration of the absorbent is carried out at a high temperature of about 120℃, which means that the regeneration process needs to provide heat through steam, which will reduce the power generation efficiency of the power plant. If the low-temperature regeneration (less than 100℃) of the absorbent can be realized, only the low-grade waste heat of the power plant can be used to regenerate the absorbent, which will greatly reduce the regeneration energy consumption of the absorbent, reduce the regeneration cost, and promote the further promotion of carbon capture technology.

[0004] Due to the problem of high regeneration energy consumption of the organic amine absorbent, the industrial development of the absorbent is limited, and it is urgent to build an absorbent system that can realize low-temperature regeneration to adapt to fixed CO2 emission sources such as thermal power plants and promote the large-scale industrial application of carbon capture technology. At present, some organic amine absorbents can realize low-temperature regeneration by adding catalysts, but this method often has problems such as high cost, low regeneration efficiency, catalyst deactivation and blockage. SUMMARY

[0005] The purpose of the application is to further promote the large-scale application of carbon capture technology, and the application provides a low-temperature regeneration non-aqueous phase absorbent for carbon dioxide capture to realize the low-temperature regeneration of the absorbent and reduce the cost of carbon capture.

[0006] To achieve the above purpose, the application provides a low-temperature regeneration non-aqueous phase absorbent for carbon dioxide capture, which is mainly composed of a sterically hindered amine and an organic solvent, wherein the sterically hindered amine is an absorption component, and the molar concentration is 1-5 mol / L, and the organic solution is used as a solvent and also participates in the reaction.

[0007] The unstable product formed after the space-stabilized amine captures CO2 is further reacted with the organic solvent to convert it into a decomposable product, thereby increasing the absorption load of the absorbent and reducing the energy barrier required for releasing CO2. In addition, the non-aqueous absorbent uses an organic solution with high boiling point and low specific heat capacity instead of water as the solvent, which can reduce the sensible heat and latent heat of regeneration, and has great energy-saving advantages.

[0008] Preferably, the organic solvent is ethylene glycol. As the organic solvent, ethylene glycol has the advantages of high boiling point and low specific heat capacity, which can reduce the sensible heat and latent heat of regeneration, and can be further reacted with the intermediate product to convert it into a decomposable product, thereby increasing the absorption load of the absorbent and reducing the energy barrier required for releasing CO2. In comparison, although other alcohols can also achieve the effect of low-temperature regeneration, the boiling point of ethanol is too low and it has strong volatility, and the viscosity of other polyhydroxy alcohols is too high, which are not conducive to industrial application.

[0009] Preferably, the space-stabilized amine includes a primary amine with three substituents on the alpha carbon, and / or a secondary amine with two / three substituents on the alpha carbon.

[0010] Specifically, the space-stabilized amine includes one or more of 2-(isopropylamino)ethanol, 2-(tert-butylamino)ethanol, tert-octylamine, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, tris(hydroxymethyl)aminomethane, N-methylcyclohexylamine, 2-methylpiperidine, and 2-methylpiperazine.

[0011] Specifically, the absorption temperature of the absorbent is 30-50℃.

[0012] Specifically, the absorbent is regenerated by thermal desorption, and the regeneration temperature is 70-100℃.

[0013] Specifically, the absorbent is a homogeneous clear solution before and after absorbing CO2, and does not undergo liquid-liquid or solid-liquid phase change. Compared with the phase change absorbent, the non-aqueous absorption system prepared by the present application is suitable for the existing carbon capture equipment, and does not need to be developed additionally, so the equipment cost is greatly reduced.

[0014] Beneficial effects: The non-aqueous absorption system prepared by the present application can realize low-temperature and high-efficiency regeneration of the absorbent without adding any catalyst, and at the same time has a high absorption rate and CO2 load. The low-temperature regenerated absorbent can utilize the low-grade heat of the power plant, thereby greatly reducing the power generation cost of the power plant with added carbon capture system, and laying the foundation for the further promotion of the carbon capture system. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1This is a schematic diagram illustrating the reaction principle of the non-aqueous phase absorbent in the CO2 capture process in this embodiment of the invention.

[0016] Figure 2 This is a comparison diagram of CO2 loading between the non-aqueous absorbent and the aqueous ethanolamine solution in Example 1 of the present invention;

[0017] Figure 3 (a) and (b) are images collected before and after CO2 absorption by the non-aqueous phase absorbent in Example 1 of the present invention, respectively.

[0018] Figure 4 This is a comparison chart of CO2 loading of non-aqueous phase absorbents at different concentrations in Example 2 of the present invention;

[0019] Figure 5 The image shows the CO2 loading change curve of the non-aqueous phase absorbent in the cyclic absorption-desorption experiment of Example 3 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0021] This embodiment provides a low-temperature regenerable non-aqueous phase absorbent for carbon dioxide capture, which is prepared by mixing a sterically hindered amine with ethylene glycol. The sterically hindered amine is the absorbent component with a molar concentration of 1-5 mol / L, while ethylene glycol acts as an organic solvent and partially participates in the reaction.

[0022] like Figure 1 As shown, this invention utilizes the steric hindrance effect of amine molecules to trap CO2 and form intermediate products with increased instability, such as zwitterions or carbamates. These products can further react with ethylene glycol, releasing amine sites that can then react with CO2, increasing the absorption load of the absorbent. Simultaneously, the energy barrier required for the newly generated products to release CO2 is much lower than that of the original products. Furthermore, the non-aqueous absorbent uses a high-boiling-point, low-specific-heat-capacity organic solution instead of water as a solvent, reducing sensible and latent heat during regeneration, resulting in significant energy-saving advantages.

[0023] Preferably, the sterically hindered amine comprises a primary amine with three substituents on the α-carbon, and / or a secondary amine with two or three substituents on the α-carbon. Specifically, the sterically hindered amine comprises one or more of 2-(isopropylamino)ethanol, 2-(tert-butylamino)ethanol, tert-octylamine, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, tris(hydroxymethyl)aminomethane, N-methylcyclohexylamine, 2-methylpiperidine, and 2-methylpiperazine.

[0024] Specifically, the conditions for the absorbent to capture CO2 include: an absorption temperature of 30–50°C and a regeneration temperature of 70–100°C. The absorbent remains a homogeneous, clear solution before and after absorbing CO2, without undergoing liquid-liquid or solid-liquid phase transitions.

[0025] Example 1:

[0026] Using N-methylcyclohexylamine as the absorbent component, non-aqueous absorbents with a concentration of 1 mol / L were prepared and compared with ethanolamine (MEA) aqueous solution under the same conditions. The test results are as follows. Figure 2 As shown, the CO2 loading of this absorbent is as high as 0.86 mol / L, which is about 1.65 times that of the MEA aqueous solution.

[0027] Meanwhile, the states of the absorbent before and after CO2 absorption saturation are as follows: Figure 3 As shown in (a) and 3(b), it can be seen that the absorbent always remains in a homogeneous and clear state, and no liquid-liquid or solid-liquid phase transition occurs.

[0028] Example 2:

[0029] Using N-methylcyclohexylamine as the absorbent component, non-aqueous absorbents with concentrations ranging from 1 to 5 mol / L were prepared. The CO2 loading of the absorbents at different concentrations is as follows: Figure 4 As shown.

[0030] It can be seen that the absorption load of the absorbent at a concentration of 1 mol / L is 0.86 mol / L, which is much higher than the theoretical load of 0.5 mol / L. This indicates that the organic solvent ethylene glycol not only acts as a solvent but also partially participates in the reaction, promoting absorption. Meanwhile, as the concentration of the absorbent component increases, the absorbent load increases from 0.86 mol / L to over 2.00 mol / L, clearly indicating a high CO2 load.

[0031] Example 3:

[0032] Using N-methylcyclohexylamine as the absorbent component, a non-aqueous absorbent with a concentration of 3 mol / L was prepared. A cyclic absorption-desorption experiment was conducted under the conditions of absorption at 40℃ for 30 min and desorption at 80℃ for 25 min. The cyclic results are as follows: Figure 5 As shown, the absorbent can maintain stable circulation under these conditions, and the load in the fourth cycle is still 2.82 times that of the initial regeneration load of the 30wt% MEA / H2O solution.

[0033] In summary, this invention achieves low-temperature regeneration without the need for a catalyst, relying solely on the properties of the absorbent itself. Furthermore, it minimizes the cost of the absorbent and equipment modifications, and results in a low viscosity of the final saturated solution, which is beneficial for promoting the large-scale application of carbon capture technology.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-temperature regenerable non-aqueous phase absorbent for carbon dioxide capture, characterized in that, The product comprises a sterically hindered amine and an organic solvent, wherein the sterically hindered amine is a single active absorbent component containing N-methylcyclohexylamine and without the addition of an active amine, and the molar concentration of the sterically hindered amine is 1~5 mol / L; the organic solvent is ethylene glycol.

2. The low-temperature regenerated non-aqueous phase absorbent according to claim 1, characterized in that, The absorption temperature of the absorbent is 30~50℃.

3. The low-temperature regenerated non-aqueous phase absorbent according to claim 1, characterized in that, The absorbent is regenerated by thermal desorption at a temperature of 70-100°C, and no catalyst is added during the regeneration process.

4. The low-temperature regenerated non-aqueous phase absorbent according to claim 1, characterized in that, The absorbent is a homogeneous and clear solution before and after absorbing CO2, without undergoing liquid-liquid or solid-liquid phase transition, and the CO2 loading after CO2 absorption is 0.86~2.00 mol / L.

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