Rapid screening process of novel liquid-liquid phase change absorbent for CO2 capture and absorbent application

Abstract

The invention provides an innovative rapid screening process of a novel liquid-liquid phase change absorbent for CO2 capture. According to the method, system components are screened by dropwise adding a physical solvent and water, the composition and the load interval of the phase change solvent are determined, and the split-phase load critical value is accurately determined by adopting a back titration method. The screening process is simple and efficient in step, is suitable for various complex liquid-liquid phase change solvent systems, greatly improves the solvent screening efficiency, and is particularly suitable for efficient solvent screening for CO2 capture. The absorbent screened by the process shows excellent CO2 absorption performance at normal temperature and normal pressure, and has the advantages of easy control of phase change conditions, low regeneration energy consumption and the like. The absorbent is not only suitable for CO2 capture of industrial emission sources of coal-fired power plants, cement plants, steel plants and the like, but also suitable for CO2 emission reduction and resource utilization processes in various environmental protection scenes.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical absorbents, and specifically relates to an efficient and rapid screening process for a novel liquid-liquid phase-change absorption system for CO2 capture. The technical solution of the present invention focuses on improving the screening efficiency of liquid-liquid phase-change absorbents, utilizing a multi-step screening method to rapidly determine the composition and properties of the phase-change solvent. This screening process not only simplifies the screening process for complex absorbent systems, but also effectively evaluates the application potential of novel absorbents in CO2 capture, thereby reducing the experimental workload in subsequent industrial applications and significantly improving the overall efficiency of absorbent screening and application. It is suitable for industrial flue gas purification and other CO2 emission reduction application scenarios. Background Art

[0002] With the acceleration of global industrialization, greenhouse gas emissions, particularly carbon dioxide (CO2), have become a major contributor to global climate change. To address this challenge, CO2 capture, utilization, and storage (CCUS) technology has emerged and has become a key approach to reducing greenhouse gas emissions. Among existing CO2 capture technologies, post-combustion capture (CCUS) has attracted significant attention in the industrial sector due to its maturity and adaptability. This technology can effectively separate and capture CO2 from flue gases from industrial sources such as coal-fired power plants, steel mills, and cement plants without changing existing combustion processes. However, existing technologies still face numerous challenges in practical application, such as high energy consumption, absorbent degradation, equipment corrosion, and excessive operating costs. Absorbents are a key component in the CO2 capture process. Traditional absorbents, such as monoethanolamine (MEA), while widely used in industry, also have significant drawbacks. For example, MEA is volatile and easily oxidized and degrades during CO2 absorption, resulting in significant losses. Furthermore, the high energy consumption during regeneration reduces overall economic viability. Therefore, researchers have gradually turned their attention to new absorbents, especially absorbents with phase change properties.

[0003] Phase change absorbents can effectively reduce regeneration energy consumption due to their characteristics of phase change when absorbing CO2 or when the temperature rises, and have high research and application potential. Phase change absorbents mainly include liquid-liquid and liquid-solid phase change forms. Among them, liquid-liquid phase change absorbents have greater application prospects because of their simple operation and no risk of pipeline blockage. After absorbing CO2, this type of absorbent can spontaneously stratify to form a rich phase rich in carbamate and bicarbonate, and then release high-purity CO2 by heating desorption, reducing regeneration energy consumption. Although liquid-liquid phase change absorbents have shown great application potential, existing research and technology still have the following problems: (1) There are many types of solvents to choose from, resulting in a huge screening workload and great difficulty in screening; (2) The phase change mechanism of existing absorbents is still unclear, and the composition of the absorbent and its optimal ratio still need to be further determined; (3) The phase separation behavior of phase change absorbents is unclear, and performance parameters such as the critical point of phase separation load and the component redistribution law of the rich and poor phases need to be further studied. In addition, although many existing patents have proposed formulas that can reduce regeneration energy consumption, they have failed to fundamentally solve the problem of efficient screening of phase change absorbents.

[0004] To address these challenges, the present invention proposes an innovative, rapid screening process for novel liquid-liquid phase-change absorber systems. This process, through step-by-step screening, rapidly determines the composition, ratio, and phase behavior of absorbents, and effectively evaluates their performance in CO2 capture. This screening process is simple, efficient, and reliable, significantly improving the efficiency of phase-change absorbent screening. It addresses the challenges of screening due to the wide variety of solvents and provides optimized absorbent solutions for subsequent industrial applications. Summary of the Invention

[0005] To overcome these challenges in phase-change absorbent research, this paper proposes an innovative rapid screening process for novel liquid-liquid phase-change absorbent systems, aiming to provide an efficient and cost-effective technical solution for CO2 capture. This process significantly simplifies the complex screening process and rapidly identifies high-performance phase-change absorbent systems suitable for CO2 capture.

[0006] In response to the current labor-intensive and complex process of screening phase-change absorbents, this paper proposes a simple and efficient screening method that can rapidly identify high-performance phase-change absorbent systems, effectively addressing the low efficiency and cumbersome steps inherent in current screening methods. This method not only simplifies the screening process but also provides an economical and practical optimization solution for carbon capture technology. This screening process rapidly determines the absorbent's composition, phase change behavior, and absorption performance, significantly improving the practical application of phase-change absorbents in CO2 capture.

[0007] Specifically, the present invention includes the following three-step screening process:

[0008] (1) Preliminary screening: Determine the absorbent system that may undergo phase separation through screening. First, through the preliminary screening of solvents and base liquids, the influence of different component ratios on phase change behavior is examined to determine the appropriate solvent system. The cross-experimental method is used in the experiment, that is, screening is carried out by water droplet addition and physical solvent droplet addition. This method can quickly and effectively determine which solvents can undergo phase change reaction with the base liquid, thereby simplifying the solvent selection process. The solvent droplet addition method is to add the physical solvent dropwise to the secondary amine aqueous solution that has absorbed CO2 to observe whether the solution changes from a homogeneous phase to a two-phase phase; the water droplet addition method is to swap the positions of ultrapure water and organic solvent, and the other operations are the same. Through this step, the appropriate solvent combination can be quickly screened, significantly reducing the screening workload.

[0009] (2) Load screening: The phase transition behavior is further explored by controlling the CO2 load and determining the load range in which phase separation occurs. In the experiment, the unloaded solution and the saturated solution after CO2 absorption are mixed in proportion, maintaining the load between 10% and 90%, and observing the phase transition of the solution. By adjusting the CO2 load level, the relationship between the phase transition behavior and absorption performance of the solution under different load conditions can be accurately explored. This step greatly simplifies the traditional load adjustment process and can quickly determine the phase separation behavior of the solution under different loads.

[0010] (3) Determine the critical load for phase separation by back titration: Back titration experiments are used to further determine the critical load point for phase separation of different solution ratios. In the experiment, fresh unloaded solution is added dropwise to the separated solution until the solution transitions from two phases to a homogeneous phase. The titration endpoint is the critical load value for phase separation of the solution. Back titration can quickly and accurately obtain the phase separation load point, avoiding the previously complicated and time-consuming screening steps, significantly improving screening efficiency, and providing a precise experimental basis for industrial applications.

[0011] The phase change absorbent system of the present invention:

[0012] The phase-change absorbent system of the present invention uses a secondary amine (such as N-ethylethanolamine (EAE)) as the base liquid. The first part of the screening process consists of two steps: First, a cross-experimental method of water droplet addition and physical solvent droplet addition is used to screen for organic solvents (such as alcohols, ethers, and amides) that undergo a phase transition with the base liquid. Second, the mass fractions of the secondary amine, organic solvent, and water are manipulated to determine the effect of different component ratios on the phase transition behavior. This step allows for rapid screening of suitable solvent combinations. The solvent droplet addition method involves adding the organic solvent dropwise to an aqueous solution of the secondary amine that has already absorbed CO2, observing whether the solution transitions from a homogeneous phase to a two-phase phase. The water droplet addition method involves swapping the positions of the ultrapure water and organic solvent, with all other procedures remaining the same. This cross-experimental method allows for rapid and efficient screening of organic solvents that undergo a phase transition with the base liquid, significantly reducing workload and improving screening efficiency.

[0013] The second part investigated the effect of solution loading on phase transition behavior by adjusting the CO2 loading. An unloaded solution was mixed with a saturated solution of CO2 absorption in a proportional manner, maintaining the loading between 10% and 90%. The phase transitions of the solution were observed to determine the phase separation behavior under different loadings. This step simplifies the traditional load adjustment process and allows for quick determination of the load range for phase separation behavior.

[0014] The third part further determines the critical load point for phase separation using back titration. In this experiment, fresh, unloaded solution is added dropwise to the separated solution until the solution transitions from two phases to a homogeneous phase. The endpoint of the titration is the critical load value for phase separation. Back titration allows for rapid and accurate determination of the phase separation load point, eliminating the cumbersome experimental steps previously required.

[0015] Using the rapid screening process described in this invention, a new liquid-liquid phase-change absorbent based on the N-ethylethanolamine (EAE)-butanol-water system was developed and optimized for use in CO2 capture. This absorbent effectively addresses the high energy consumption and low regeneration efficiency issues associated with existing absorbents in CO2 capture. The screening method and absorbent development complement each other, simplifying the screening process while also improving the CO2 capture performance of the phase-change absorbent, making it suitable for practical industrial applications.

[0016] Function and addition of additives:

[0017] In the phase change absorbent system of the present invention, the addition of additives can effectively improve the performance of the absorbent. The additives used include defoamers, antioxidants and corrosion inhibitors:

[0018] (1) Defoaming agent: It can reduce the generation of bubbles during the absorption process and prevent bubbles from affecting the absorption efficiency of the absorbent;

[0019] (2) Antioxidant: used to prevent the performance degradation of the absorbent due to oxidative degradation during long-term operation, thereby ensuring the service life of the absorbent;

[0020] (3) Corrosion inhibitor: It can extend the service life of equipment by reducing the corrosion of metal parts by absorbents, especially in industrial applications.

[0021] The amount of additives added is usually controlled within a trace range that does not affect the main properties of the absorbent, and can achieve the effect of optimizing the performance of the absorbent.

[0022] Compared with the prior art, the technical advantages of the present invention mainly include:

[0023] (1) Fast and simple screening process: The screening system developed in this invention simplifies the screening process for phase-change absorbents, effectively reducing workload and significantly improving screening efficiency. This solves the screening problem caused by the wide variety of solvents. Through crossover experiments and back titration, the composition and phase change behavior of the phase-separation absorbent system are quickly and accurately determined, avoiding the lengthy steps in previous screening processes.

[0024] (2) Comprehensive absorbent property evaluation: This invention not only systematically screens a complete liquid-liquid phase change absorbent system, but also comprehensively explores the system's phase separation behavior, absorption performance, component ratio, and phase separation load point. During the screening process, the load can be quickly adjusted to determine the system's phase separation load critical point, allowing the absorbent's performance to be fully evaluated and optimized.

[0025] (3) New absorbents with superior performance: The selected N-ethylethanolamine (EAE)-butanol-water system absorbent exhibits significantly improved CO2 capture performance compared to traditional absorbents. This absorbent is capable of operating over a wide temperature and pressure range, has a high CO2 concentration in the rich phase after phase separation, and consumes less energy during regeneration. The low volume fraction of the rich phase reduces energy consumption during desorption, making it more suitable for industrial applications.

[0026] (4) Wide range of application scenarios: The absorbent of the present invention is not only suitable for CO2 capture from industrial emission sources such as coal-fired power plants, cement plants and steel plants, but can also be used in a variety of environmental protection scenarios, especially in situations where it is necessary to reduce CO2 emissions and improve capture efficiency. It has important application prospects.

[0027] (5) Industrial adaptability and regeneration efficiency: The absorbent system selected by the present invention not only significantly reduces energy consumption during CO2 capture, but also enables efficient regeneration at lower temperatures, reducing equipment requirements and operating costs. Therefore, the absorbent system developed by the present invention has strong adaptability in industrial applications and can reduce problems such as equipment corrosion and absorbent degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attachment Figure 1 This is a diagram showing the changes in the water drop addition experiment process in Example 1.

[0029] Attachment Figure 2 This is a diagram showing the changes in the solvent dropwise addition experiment process in Example 1.

[0030] Attachment Figure 3 These are the two-phase volume ratio diagrams after phase separation of the EAE-n-butanol-water system solutions with different mass ratios in Experimental Example 3, the upper and lower phase ratio diagrams of EAE concentration, the CO2 absorption load diagram of the lean and rich liquids, and the rich liquid load ratio diagram.

[0031] Attachment Figure 4This is the phase separation behavior of the EAE-butanol-water system at different temperatures in Experimental Example 4. DETAILED DESCRIPTION

[0032] The following specific examples provide detailed descriptions of the screening process, absorbent system, and applications of the present invention. These examples are intended to provide typical experimental procedures and results for reference and understanding by those skilled in the art. The present invention is not limited to these examples; any modifications, equivalent substitutions, or variations based on these examples are intended to fall within the scope of protection of the present invention.

[0033] Example 1: Absorbent Screening Process

[0034] This example demonstrates the operational process of screening an absorbent system based on N-ethylethanolamine (EAE) and various physical organic solvents. The specific steps are as follows:

[0035] (1) Preliminary screening: Using the water droplet addition experiment and the solvent droplet addition experiment, we screened out the solvent system that can undergo phase change after absorbing CO2 after combining with the EAE base liquid from a variety of physical organic solvents. Water droplet addition method: Add ultrapure water dropwise to the physical solvent and observe the phase change behavior of the solution (see Appendix Figure 1 Solvent addition method: add pure CO2 to a 30 wt% EAE aqueous solution at room temperature until it is saturated, then add a physical organic solvent (such as butanol, acetone, acetonitrile, etc.) dropwise to observe whether liquid-liquid phase separation occurs (see attached). Figure 2 The results showed that n-butanol, isobutanol, and tert-butanol all caused liquid-liquid phase separation after absorbing CO2 (see Table 1).

[0036] (2) Load screening: In the initially screened solvent system, the EAE / solvent ratio was further adjusted, and the CO2 loading was gradually increased to observe the phase transition behavior of the solution. In the experiment, the mass fraction of EAE was maintained at 30wt%, and the concentration of butanol solvent ranged from 0wt% to 70wt%. The relationship between the solvent ratio and the CO2 loading range was determined experimentally. The results showed that when the butanol concentration increased to 30wt%-40wt%, the solution began to undergo obvious phase separation after the loading reached 0.97mol / L.

[0037] (3) Determination of the critical load for phase separation by back titration: To accurately determine the critical load for phase separation, a fresh, unloaded solution is added dropwise to a solution that has absorbed CO2 and separated into phases. The point at which the solution transitions from two phases to a homogeneous phase is observed and recorded as the titration endpoint. Experiments have shown that the critical load for phase separation is reached at 1.577 mol / L for the n-butanol system.

[0038] Example 2: Application of additives and performance improvement

[0039] This example demonstrates the role of additives in the absorbent system of the present invention and their effect on performance optimization. The additives include a defoamer (polydimethylsiloxane), an antioxidant (BHT), and a corrosion inhibitor (sodium nitrite). The experiment is as follows:

[0040] (1) Effect of defoaming agent: 0.1 wt% of defoaming agent was added to the EAE-n-butanol-water system. The results showed that the defoaming agent could reduce the bubbles generated during the absorption process and increase the absorption rate by about 10%.

[0041] (2) Effect of antioxidant: 0.05 wt% BHT was added to the EAE system and the absorption experiment was run continuously for more than 200 hours. The experiment showed that the antioxidant effectively slowed down the oxidative degradation of the absorbent and the absorption performance remained stable.

[0042] (3) 0.1 wt% sodium nitrite was added to the EAE-n-butanol-water system to simulate the corrosion environment of industrial equipment. The results showed that the corrosion inhibitor significantly reduced the corrosion of the absorbent on the equipment and extended the service life of the equipment.

[0043] Experimental Example 1: Physical organic solvent screening experiment

[0044] The experiment demonstrated the screening process for 15 different physical organic solvents. Experimental conditions were room temperature (24°C) and the addition of water and solvents was alternating. The EAE mass fraction was maintained at 30 wt%, and pure CO2 was bubbled through the solution until saturation loading was reached. The results showed that n-butanol, isobutanol, tert-butanol, acetone, and acetonitrile all exhibited liquid-liquid phase separation with the EAE base solution, while other solvents (such as isopropanol and dimethyl sulfoxide) did not (see Table 1).

[0045] Experimental Example 2: Phase Transition Behavior of EAE-Butanol-Water System

[0046] The experiment further studied the effect of the solvent ratio in the EAE-butanol-water system on the phase change behavior after CO2 loading. At room temperature, the phase separation behavior of the solution was observed after absorbing CO2. The experiment showed that when the mass fraction of butanol was 10%-40%, the solution underwent obvious phase separation, and with the increase of butanol content, the CO2 concentration in the rich phase after phase separation increased significantly. At the ratio of 3:1:6, the CO2 loading ratio of the rich phase was as high as 99%, indicating that the absorbent has excellent mass transfer performance and regeneration stability (see Appendix). Figure 3 ).

[0047] Table 1 Cross-drip test results

[0048] — Water drop experiment Water drop experiment Solvent addition experiment Solvent addition experiment Solvent name Is there phase separation after dropwise addition? Volume added during phase separation (mL) Is there phase separation after dropwise addition? Volume added during phase separation (mL) n-Propanol × — × — Isopropyl alcohol × — × — n-Butanol √ 4 √ 4 Isobutanol √ 3 √ 3 tert-Butanol × — √ 2 Ethylene glycol monoethyl ether × — × — Ethylene glycol monomethyl ether × — × — Diethylene glycol monoethyl ether × — × — Acetonitrile √ 2 √ 2 Sulfolane × — × — dimethyl sulfoxide × — × — N-Methylpyrrolidone × — × — acetone √ 1 √ 6 N,N-Dimethylformamide × — × — N,N-Dimethylacetamide × — × —

[0049] Experimental Example 3: Load Point and Phase Performance Study

[0050] This experiment investigated the absorption performance and phase separation of an EAE-n-butanol-water absorbent system at various loading ratios. Back titration was used to investigate the phase separation load point at various ratios. A fresh, unloaded solution was added dropwise to a solution that had already undergone stable phase separation. The point at which the solution transitioned from two phases to a clear, homogeneous phase was observed and recorded as the critical phase separation load point for that ratio (see Table 2). The phase separation load point gradually increased with increasing n-butanol content in the system. This demonstrates that adjusting the phase separation agent content can effectively control the phase separation load point and optimize absorbent performance.

[0051] Table 2 Phase separation loading points of EAE-n-butanol-water system at different ratios

[0052] <![CDATA[M EAE : M 正丁醇 :M H2O ]]> 3:1:6 3:2:5 3:3:4 3:4:3 <![CDATA[CO2 loading (mol / L)]]> 0.970 1.084 1.517 1.577 <![CDATA[CO2 loading (mol / mol)]]> 0.293 0.349 0.480 0.508

[0053] Experimental Example 4: Effect of Temperature on Phase Separation Behavior

[0054] This experiment studies the effect of temperature on the phase separation absorbent system. The experimental conditions are 20℃ to 90℃, and the phase separation behavior of the EAE-butanol-water system at different temperatures is observed (see Appendix Figure 4 The results show that the phase separation behavior remains stable before the temperature rises to 80°C. Above 80°C, the phase separation behavior changes due to water evaporation, but the system still exhibits good thermal stability and is suitable for industrial applications in a wide temperature range.

[0055] The above description is only part of the embodiments of the present invention and is not intended to be the scope of protection of the present invention. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present invention are included in the scope of protection of the present invention.

Claims

1. A screening process for a novel liquid-liquid phase change absorbent for CO2 capture, characterized in that: The following steps are involved: S1: Preliminary screening of the base liquid amine and the selected physical organic solvent was performed by water drop addition and physical solvent drop addition to determine the components of the phase change system, and the phase separation state and ratio of the solution were determined by adjusting the mass fractions of the amine compound, the organic solvent and water; S2: After the component ratio is determined by S1, the load threshold of CO2 is controlled, the phase change behavior of the system is regulated, and the load range where the phase change occurs is determined; S3: In the load range determined by S2, the back titration method is used to further determine the critical value of the phase separation load of the solution system with different ratios, and screen out the phase change system with the best CO2 absorption performance.

2. The screening process according to claim 1, characterized in that: The solvent addition method includes dripping a selected physical organic solvent (such as alcohol, ether, amide, etc.) drop by drop into an aqueous solution of an amine compound (such as primary, secondary, tertiary amine, etc.) that has absorbed CO2 to saturation, and observing whether the solution changes from a uniform clear phase to two phases; the water addition method is to add ultrapure water drop by drop into an organic solvent for the same observation.

3. The screening process according to claim 1, characterized in that: The screening process is to determine the effect of CO2 loading on phase change behavior by mixing saturated loading solution and unloaded solution in different proportions to maintain the overall loading of the system between 10% and 90% of the saturated loading.

4. The screening process according to claim 1, characterized in that: The back titration method is to gradually add a fresh solution to a phase-separated solvent system until the solution changes from two phases to a clear homogeneous phase, and the phase separation critical point of the solution is recorded at this time.

5. A liquid-liquid phase change absorbent developed according to the screening process of claims 1 to 4, characterized in that: The absorbent consists of secondary amine (N-ethylethanolamine, EAE), organic solvent (including n-butanol, isobutanol or a mixture thereof) and water, and a defoamer, an antioxidant or a corrosion inhibitor is added as an auxiliary agent.

6. The liquid-liquid phase change absorbent according to claim 5, characterized in that: The method is prepared according to the following weight percentages: 10%-90% N-ethylethanolamine (EAE), 10%-90% organic solvent, 10%-90% water, and a trace amount of additives for optimizing the performance of the absorbent, wherein the additives are one or more of a defoamer, an antioxidant or a corrosion inhibitor.

7. The absorbent according to claims 5 to 6, characterized in that The absorbent can effectively absorb CO2 gas with a volume fraction of 5% to 100% at normal temperature of 25°C to 50°C and normal pressure.

8. The absorbent according to claims 5 to 7, characterized in that After the CO2 load reaches the critical value, the solution system begins to separate into phases, and the volume proportion of the rich phase does not exceed 80%.

9. The absorbent according to claims 5 to 8, characterized in that After absorbing the CO2, only the rich phase needs to be regenerated by heating to 70°C to 90°C to release and recover high-purity CO2.

10. Use of the absorbent according to claims 1 to 9, characterized in that The absorbent can be widely used in the flue gas purification process of industrial emission sources such as coal-fired power plants, cement plants, steel plants, and any environmental protection application scenarios aimed at reducing industrial CO2 emissions.

11. A method for capturing CO2 using the absorbent according to any one of claims 1 to 10, characterized in that: The method includes fully contacting the absorbent with the CO2-containing gas to enable it to absorb CO2 and form a liquid-liquid two-phase, and then thermally treating the rich phase to release and recover high-purity CO2, thereby achieving effective capture and resource utilization of CO2.

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