Liquid-liquid phase change absorbent for capturing carbon dioxide

Abstract

The invention discloses a liquid-liquid phase change absorbent for capturing carbon dioxide, and belongs to the technical field of carbon capture, the absorbent comprises an absorption component and a solvent component, the absorption component comprises N, N-dimethylethanolamine and 2-methylaminoethanol, the solvent component comprises triethylene glycol monobutyl ether and water, and the solvent component comprises a solvent component and a solvent component. The phase change absorbent is a homogeneous solution before absorbing CO2 and is divided into an upper liquid phase and a lower liquid phase after absorbing CO2 to be saturated, and CO2 is enriched in a lower water phase. According to the absorbent, the volume of a rich phase needing to be regenerated is greatly reduced through phase separation, and the energy consumption in the regeneration process can be effectively reduced, so that the defects of a traditional organic amine absorption method are effectively overcome. In addition, the method has the advantages of high absorption load, high absorption rate, short phase splitting time, high CO2 enrichment degree, high regeneration efficiency, low regeneration energy consumption, low saturated solution viscosity and the like, and has a wide industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon capture, and particularly relates to a liquid-liquid phase change absorbent for capturing carbon dioxide. Background Art

[0002] Carbon dioxide capture, utilization and storage technology (CCUS) is an effective CO2 capture technology for fixed CO2 emission source processes such as thermal power generation, steelmaking, and limestone calcination. Among them, organic amine absorbents are the most widely used chemical absorbents in industrial applications at present. However, the excessively high regeneration energy consumption and cost limit their further popularization. Phase change absorbents developed based on traditional organic amine absorbents are considered to be able to significantly reduce the desorption energy consumption and have become a research hotspot in recent years.

[0003] Compared with traditional thermal desorption, for the phase change absorbent with phase separation after absorption, the amount of CO2-rich liquid entering the desorption tower is significantly reduced, and the regeneration energy consumption is significantly reduced by reducing the heat exchange load. Therefore, it is considered to be an ideal CO2 absorbent. However, the existing phase change absorbents generally have high regeneration energy consumption and cannot simultaneously take into account properties such as viscosity, absorption capacity, absorption and phase separation rate, regeneration efficiency, and corrosiveness, and further optimization is needed. Summary of the Invention

[0004] Object of the Invention: In order to make up for the deficiencies of the prior art, the present invention provides a novel liquid-liquid phase change absorbent for capturing carbon dioxide, providing support for the industrial promotion of carbon dioxide capture technology.

[0005] Summary of the Invention: To achieve the above object, the present invention provides a liquid-liquid phase change absorbent for capturing carbon dioxide, including an absorption component and a solvent component. The absorption component includes N,N-dimethylethanolamine (DMEA) and 2-methylaminoethanol (MAE), and the solvent component includes triethylene glycol monobutyl ether (TGME) and water (H2O). The phase change absorbent is a homogeneous solution before absorbing CO2 and is divided into upper and lower liquid phases after absorbing CO2 to saturation, where CO2 is enriched in the lower aqueous phase.

[0006] Among them, DMEA and MAE can play a good synergistic effect as the absorption component, having a large absorption amount and a stable regeneration rate. And TGME as a phase separation agent can be divided into rich and lean liquid phases with the product aqueous solution, reducing the volume of the rich phase to be regenerated and effectively reducing the regeneration energy consumption.

[0007] Specifically, in the phase change absorbent, the concentration of N,N-dimethylethanolamine is preferably 1-3 mol / L.

[0008] Specifically, in the phase change absorbent, the concentration of 2-methylaminoethanol is preferably 0-1.5 mol / L.

[0009] Specifically, in the phase change absorbent, the volume ratio of triethylene glycol monobutyl ether to water is preferably 6:12 to 10:8.

[0010] Specifically, the phase change absorbent is used to absorb pure CO2 or a mixed gas containing CO2, and the volume ratio of CO2 in the mixed gas is not less than 5%.

[0011] Specifically, the absorption temperature of the phase change absorbent is 30 to 60 °C, and the absorption load is not less than 0.4 mol CO2 / mol organic amine.

[0012] Specifically, after the phase change absorbent absorbs CO2 to saturation, the volume of the liquid phase enriched with CO2 accounts for 41 to 72% of the total volume, and the enrichment degree of CO2 in the rich phase is 72 to 90%.

[0013] Specifically, after the phase change absorbent absorbs CO2 to saturation, the viscosities of the upper and lower liquid phases are both not higher than 9 mPa·s.

[0014] Specifically, after the phase change absorbent absorbs CO2 to saturation, it is regenerated by thermally desorbing the lower aqueous phase, and the regeneration temperature is 80 to 120 °C.

[0015] Furthermore, the regeneration energy consumption of the phase change absorbent is not higher than 2.62 GJ / t CO2.

[0016] Beneficial effects: Compared with traditional organic amine absorbents, the liquid-liquid phase change absorbent provided by the present invention greatly reduces the volume of the rich phase required for regeneration through phase separation, can effectively reduce the energy consumption in the regeneration process, and thus effectively overcomes the defects of the traditional organic amine absorption method.

[0017] Compared with other phase change absorbents, the liquid-liquid phase change absorbent provided by the present invention simultaneously has advantages such as high absorption load, fast absorption rate, short phase separation time, high CO2 enrichment degree, high regeneration efficiency, low regeneration energy consumption, and low viscosity of the saturated solution, and thus has broad industrial application prospects.

[0018] In addition, the absorbent undergoes phase separation only when it is close to saturation, has the characteristic of controllable phase change, and can regulate whether to undergo phase separation by adjusting the CO2 load of the absorbent, and will be a new type of economical and efficient CO2 absorbent with practical application prospects, which is more conducive to industrial promotion. Description of the Drawings

[0019] Figure 1 It is a comparison chart of the cycle load of the solution prepared in Example 1 of the present invention and the MEA aqueous solution under the same cycle conditions;

[0020] Figure 2It is a data graph of CO2 loading of the solution configured in Embodiment 2 of the present invention under different solvent ratios;

[0021] Figure 3 It is a data graph of the regeneration energy consumption of the solution configured in Embodiment 2 of the present invention under different solvent ratios;

[0022] Figure 4 It is a data graph of the solution viscosity of the solution configured in Embodiment 2 of the present invention under different solvent ratios;

[0023] Figure 5 It is a data graph of the phase separation time of the solution configured in Embodiment 3 of the present invention at different temperatures. Detailed implementation manners

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention.

[0025] To realize the industrial promotion of carbon dioxide capture, the embodiments of the present invention provide a liquid-liquid phase change absorbent for capturing carbon dioxide, which includes N,N-dimethylethanolamine (DMEA), 2-methylaminoethanol (MAE), water (H2O) and triethylene glycol monobutyl ether (TGME), thus forming a quaternary component system. Among them, the tertiary amine DMEA and the secondary amine MAE are the absorption components of the absorbent, and water and TGME are the solvent components of the absorbent.

[0026] Before absorbing CO2, the phase change absorbent is a homogeneous quaternary mixed system. After absorbing CO2 to a certain load (at least reaching 88% of the equilibrium load), liquid-liquid phase change gradually occurs. After the phase change occurs, the CO2 absorption product is enriched in the lower water phase, and TGME acts as a phase separation agent to separate the rich and lean liquid phases from the product aqueous solution.

[0027] Specifically, in the phase change absorbent, the concentration of N,N-dimethylethanolamine is preferably 1-3 mol / L, the concentration of 2-methylaminoethanol is preferably 0-1.5 mol / L, and the volume ratio of triethylene glycol monobutyl ether to water is preferably 6:12-10:8.

[0028] Specifically, the phase change absorbent is used to absorb pure CO2 or a mixed gas containing CO2. In this embodiment, the absorption object is a mixed gas with a CO2 volume ratio of 5-20%, the absorption temperature is 30-60 °C, and the absorption load is not less than 0.4 mol CO2 / mol organic amine.

[0029] Specifically, after the phase change absorbent absorbs CO2 to saturation, the volume of the liquid phase enriched with CO2 accounts for 41-72% of the total volume, the enrichment degree of CO2 in the rich phase is 72-90%, and the viscosities of both the CO2-lean and CO2-rich phases are not higher than 9 mPa·s.

[0030] Specifically, after the phase change absorbent absorbs CO2 to saturation, it is regenerated by thermally desorbing the lower aqueous phase. The regeneration temperature is 80-120 °C, and the regeneration energy consumption is not higher than 2.62 GJ / t CO2.

[0031] Example 1:

[0032] A solution was prepared using 2 mol of DMEA, 1.25 mol of MAE, and 1 L of solvent (TGME: water = 6:12). As Figure 1 shown, under the cyclic conditions of absorption at 40 °C and regeneration at 80 °C, the cyclic loading of this solution (i.e., the CO2 loading after desorption and regeneration) is 0.37 mol / mol, which is 1.85 times that of a 5 mol / L MEA (0.2 mol / mol) aqueous solution, and the viscosity of the rich phase is 7.71 mPa·s.

[0033] Example 2:

[0034] A solution was prepared using 2 mol of DMEA, 1.25 mol of MAE, and 1 L of solvent (TGME and water). Figure 2 、 3 、4 respectively show the CO2 loading data, regeneration energy consumption data, and solution viscosity data of this solution under different solvent ratios. Among them, the phase change loading refers to the CO2 loading when the absorbent starts to phase separate, and the equilibrium loading refers to the CO2 loading when the absorbent is first absorbed to saturation.

[0035] It can be seen that even under different solvent ratios, the CO2 absorption loading of the above solution is not less than 0.4 mol CO2 / mol, the regeneration energy consumption is not higher than 2.62 GJ / t CO2, and the viscosities of both the CO2-lean and CO2-rich phases are not higher than 9 mPa·s. In addition, under the ratio of TGME: water = 9:9, the regeneration energy consumption of the solution is even as low as 1.99 GJ / t CO2.

[0036] Example 3:

[0037] A solution was prepared using 2 mol of DMEA, 1.25 mol of MAE, and 1 L of solvent (TGME: water = 9:9). Figure 5 shows the phase separation time data of this solution at different temperatures. It can be seen that the phase separation time of this solution decreases with increasing temperature in the temperature range of 30-60 °C and is not higher than 390 s, thus being conducive to industrial promotion.

[0038] In summary, the liquid-liquid phase change absorbent provided by the present invention simultaneously has the advantages of high absorption load, fast absorption rate, short phase separation time, high CO2 enrichment degree, high regeneration efficiency, low regeneration energy consumption, and low viscosity of saturated solution, and thus has broad industrial prospects.

[0039] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A liquid-liquid phase change absorbent for carbon dioxide capture, characterized in that, It includes an absorption component and a solvent component. The absorption component includes N,N-dimethylethanolamine and 2-methylaminoethanol. The solvent component includes triethylene glycol monobutyl ether and water. The phase change absorbent is a homogeneous solution before absorbing CO2 and is divided into two upper and lower liquid phases after absorbing CO2 to saturation, where CO2 is enriched in the lower aqueous phase.

2. The liquid-liquid phase change absorbent according to claim 1, wherein, In the phase change absorbent, the concentration of N,N-dimethylethanolamine is 1 to 3 mol / L.

3. The liquid-liquid phase change absorbent according to claim 1, wherein In the phase change absorbent, the concentration of 2-methylaminoethanol is 0 to 1.5 mol / L.

4. The liquid-liquid phase change absorbent according to claim 1, characterized in that, In the phase change absorbent, the volume ratio of triethylene glycol monobutyl ether to water is 6:12 to 10:

8.

5. The liquid-liquid phase change absorbent according to claim 1, characterized in that, The phase change absorbent is used to absorb pure CO2 or a mixed gas containing CO2, and the volume ratio of CO2 in the mixed gas is not less than 5%.

6. The liquid-liquid phase change absorbent according to claim 1, wherein The absorption temperature of the phase change absorbent is 30 to 60 °C, and the absorption load is not less than 0.4 mol CO2 / mol organic amine.

7. The liquid-liquid phase change absorbent according to claim 1, wherein After the phase change absorbent absorbs CO2 to saturation, the volume of the liquid phase enriched with CO2 accounts for 41 to 72% of the total volume, and the enrichment degree of CO2 in the rich phase is 72 to 90%.

8. The liquid-liquid phase change absorbent according to claim 1, wherein After the phase change absorbent absorbs CO2 to saturation, the viscosities of the upper and lower liquid phases are both not higher than 9 mPa·s.

9. The liquid-liquid phase change absorbent according to claim 1, characterized in that After the phase change absorbent absorbs CO2 to saturation, regeneration is achieved by thermally desorbing the lower aqueous phase, and the regeneration temperature is 80 to 120 °C.

10. The liquid-liquid phase change absorbent according to claim 9, wherein, The regeneration energy consumption of the phase change absorbent is not higher than 2.62 GJ / t CO2.

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