Composite absorbent for separating carbon dioxide from a mixed gas

Abstract

The application discloses a composite absorbent for separating carbon dioxide in mixed gas; the application provides a composite absorbent for separating carbon dioxide in mixed gas, which is composed of hydroxyethyl ethylenediamine, benzyl alcohol and water, and the desorption temperature of the composite absorbent is less than 100 DEG C, which can be applied to the scene with a desorption temperature less than 100 DEG C, and shows good absorption and desorption effect on CO2 in the mixed gas.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, and specifically to a composite absorbent for separating carbon dioxide from a mixed gas. Background Technology

[0002] Among various technologies for reducing CO2 emissions, carbon capture, utilization, and storage (CCUS) technology, which is environmentally friendly and highly efficient at capturing CO2, can separate CO2 from stationary carbon emission sources such as industrial processes and energy utilization, or from the atmosphere. After capture and compression, it is transported to specific locations for conversion and utilization or injected into reservoirs for storage, thereby separating CO2 from the atmosphere for a long period of time and achieving permanent emission reduction. This has made CCUS a major means of reducing CO2 emissions in global industry. CCUS technology can effectively ensure the normal power supply and low-carbon operation of coal-fired power plants throughout the entire process.

[0003] In the CCUS system, chemical absorption refers to the process of targeted CO2 removal by using a chemical solvent as the absorbent and utilizing the chemical reaction between the absorbent and CO2. In this method, the absorbent is alkaline, and CO2 is acidic; a neutralization reaction occurs to form salts. By changing external conditions, the entire reaction can be reversed, achieving CO2 desorption and absorbent regeneration. Physical absorption, on the other hand, uses a physical solvent as the absorbent. By changing physical conditions such as pressure and temperature, the physical solvent absorbs and desorbs CO2. Throughout this process, the physical solvent does not chemically react with CO2, offering advantages such as rapid desorption rates and low regeneration energy consumption.

[0004] Currently, absorbents generally contain a variety of additives, which does not significantly improve their absorption and desorption of CO2. Furthermore, the introduction of multiple additives makes the composition of the absorbent more complex, which greatly increases the possibility of reactions between the components within the absorbent, thereby further reducing its absorption and desorption efficiency for CO2. Summary of the Invention

[0005] This application provides a composite absorbent for separating carbon dioxide from a mixed gas, which can improve the absorption and desorption of CO2 with fewer types of chemical components.

[0006] This application provides a composite absorbent for separating carbon dioxide from a mixed gas, which is composed of hydroxyethyl ethylenediamine (AEEA), benzyl alcohol and water, and the desorption temperature of the composite absorbent is less than 100°C.

[0007] In some embodiments, the hydroxyethyl ethylenediamine accounts for 30% of the total mass of the composite absorbent by weight percentage.

[0008] In some embodiments, the benzyl alcohol accounts for 30-50% of the total mass of the composite absorbent by weight percentage.

[0009] In some embodiments, the water accounts for 20-40% of the total mass of the composite absorbent by weight percentage.

[0010] In some embodiments, the composite absorbent is composed of 30% hydroxyethyl ethylenediamine, 50% benzyl alcohol, and 20% water by weight percentage.

[0011] In some embodiments, the average absorption rate of the composite absorbent over 120 min is between 2.68 × 10⁻⁶. -2 L / min up to 3.68 × 10 -2 Between L / min.

[0012] In some embodiments, the average desorption rate of the composite absorbent over 120 min is between 2.23 × 10⁻⁶. -2 L / min up to 2.47 × 10 -2 Between L / min.

[0013] In some embodiments, the desorption rate of the composite absorbent is not less than 80%.

[0014] In some embodiments, the desorption temperature of the composite absorbent is 95°C.

[0015] In some embodiments, the mixed gas includes flue gas from a coal-fired power plant.

[0016] As can be seen from the above technical solutions, this specification provides a composite absorbent for separating carbon dioxide from a mixed gas. The composite absorbent is composed of three components: hydroxyethyl ethylenediamine, benzyl alcohol, and water. It can be applied to scenarios where the desorption temperature is less than 100°C and exhibits good absorption and desorption effects on CO2 in the mixed gas. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A diagram of the carbon dioxide absorption and desorption experimental apparatus provided in this application is shown;

[0019] Figure 2 The diagram shows the relevant test results of the composite absorbents provided in Example 1 and Comparative Examples 1-9;

[0020] Figure 3 The diagram shows the relevant test results of the composite absorbents provided in Examples 1-6. Detailed Implementation

[0021] To facilitate understanding of this specification, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this specification are shown in the drawings. However, this specification can be implemented in many different forms without departing from the core spirit of this specification and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this specification.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this specification belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this specification. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] This application provides a composite absorbent for separating carbon dioxide from a mixed gas. The composite absorbent is composed of hydroxyethyl ethylenediamine, benzyl alcohol, and water, and the desorption temperature of the composite absorbent is less than 100°C.

[0024] The composite absorbent provided in this application consists of three components: hydroxyethyl ethylenediamine, benzyl alcohol, and water. Applying this composite absorbent to separate CO2 from a mixed gas can include two stages: a CO2 absorption stage and a CO2 desorption stage. In the CO2 absorption stage, hydroxyethyl ethylenediamine reacts with CO2 to form carbamate, which then hydrolyzes in water to form free amine, which in turn absorbs more CO2. Benzyl alcohol acts as a physical solvent to absorb CO2 and does not react with it. In the CO2 desorption stage, the carbamate formed from the reaction of hydroxyethyl ethylenediamine and CO2 is relatively stable and difficult to desorb. As mentioned earlier, benzyl alcohol only physically absorbs CO2 and does not react with it. Therefore, the introduction of benzyl alcohol can improve the desorption effect. Furthermore, since the sensible heat required to heat benzyl alcohol to its desorption temperature is less than that of water, and the latent heat carried away by water vapor evaporation is eliminated, most of the energy saved is used for the desorption reaction. Therefore, the introduction of benzyl alcohol can accelerate the solution desorption process and increase the desorption rate.

[0025] The composite absorbent provided in this application embodiment can complete desorption at temperatures below 100°C without raising the desorption temperature above 100°C. Therefore, it can be used to absorb and separate CO2 from mixed gases with an original temperature below 100°C.

[0026] In some embodiments, the mass percentage of hydroxyethyl ethylenediamine is 30% of the total mass of the composite absorbent, the mass percentage of benzyl alcohol is 30-50% of the total mass of the composite absorbent, and the mass percentage of water is 20-40% of the total mass of the composite absorbent.

[0027] Extensive experiments have shown that the absorption and desorption rates of CO2 by the composite absorbent can be controlled by adjusting the dosage of each component. Specifically, compared to other composite additives, when the mass percentages of hydroxyethyl ethylenediamine (30%), benzyl alcohol (30-50%), and water (20-40%) are controlled, the resulting composite absorbent exhibits higher overall absorption, desorption rates, and desorption rates.

[0028] In some embodiments, the composite absorbent is composed of 30% hydroxyethyl ethylenediamine, 50% benzyl alcohol, and 20% water by mass percentage. The inventors discovered through experiments that further controlling the mass percentages of hydroxyethyl ethylenediamine (30%), benzyl alcohol (50%), and water (20%) in the composite absorbent results in a more superior overall performance in terms of absorption rate, desorption rate, and desorption percentage.

[0029] In some embodiments, the average absorption rate of the composite absorbent over 120 min is between 2.68 × 10⁻⁶. -2 L / min up to 3.68 × 10 -2 The absorption rate can be between L / min. For example, the average absorption rate of a composite absorbent over 120 min could be 2.68 × 10⁻⁶. -2 L / min, 2.80×10 -2 L / min, 3.00×10 -2 L / min, 3.24×10 -2 L / min, 3.40×10 -2 L / min, 3.60×10 -2 L / min, 3.68×10 -2 L / min or any value between any two of the above absorption rates.

[0030] In some embodiments, the average desorption rate of the composite absorbent over 120 min is between 2.23 × 10⁻⁶. -2 L / min up to 2.47 × 10 -2 The rate can be between L / min. For example, the average desorption rate of the composite absorbent over 120 min could be 2.23 × 10⁻⁶. -2 L / min, 2.29×10 -2 L / min, 2.32×10 -2 L / min, 2.35×10-2 L / min, 2.40×10 -2 L / min, 2.45×10 -2 L / min, 2.47×10 -2 L / min or any value between any two of the above desorption rates.

[0031] In some embodiments, the desorption rate of the composite absorbent is not less than 80%. Extensive experiments have shown that the composite absorbent provided in this application, when used to separate carbon dioxide from a mixed gas, exhibits a high desorption rate, which can reach over 80%, for example, 80%, 80.1%, 85.9%, or other values ​​greater than 80%.

[0032] In some embodiments, the desorption temperature of the composite absorbent is 95°C. In the field of waste treatment technology for coal-fired power plants, the desorption temperature of absorbents is generally 90-110°C (at normal pressure). However, due to the presence of a certain mass of water in the solution system, if the desorption temperature exceeds 100°C (exceeding the boiling point of water), a large amount of water will evaporate during the entire desorption process, which is detrimental to desorption. Since industrial applications of this technology particularly value desorption at normal pressure, considering the actual desorption temperature range in industrial applications and the volatility characteristics of water, the suitable desorption temperature for the composite absorbent provided in this application embodiment is below 100°C. For example, the desorption temperature can be 95°C.

[0033] In some embodiments, the mixture includes flue gas from a coal-fired power plant.

[0034] The following are specific preparation examples related to the above-described contents of this disclosure. It should be clarified that the following examples are merely illustrative of the composite absorbent for separating carbon dioxide from a mixed gas disclosed above, and the specific implementation methods and parameters used are only one or more of the numerous processes and methods described above. Those skilled in the art can prepare the composite absorbent for separating carbon dioxide from a mixed gas using other parameters according to the methods described above, without departing from the core spirit of the application.

[0035] The embodiments and comparative examples of this application use the following methods to test the separation effect of the composite absorbent on carbon dioxide in a mixed gas. Figure 1 A diagram of the carbon dioxide absorption and desorption experimental apparatus provided in an embodiment of this application is shown. Figure 1 As shown, the device may include a simulated coal-fired power plant flue gas unit A, an absorption and desorption unit B, and a carbon dioxide detection unit C.

[0036] The simulated coal-fired power plant flue gas unit A includes a nitrogen cylinder 1 and a carbon dioxide and nitrogen mixed cylinder 2. The carbon dioxide partial pressure in the carbon dioxide and nitrogen mixed cylinder 2 is 15%, and the nitrogen partial pressure is 85%. The simulated coal-fired power plant flue gas unit A is connected to the absorption and desorption unit B via pressure reducing valves 3 and 4, three-way valves 5 and 6, and a flow meter 7. The absorption and desorption unit B includes a heating and stirring component 9, a temperature detection component 10, and a condensation and reflux component 8. The absorption and desorption unit B is connected to the carbon dioxide detection unit C via a drying component 11. The carbon dioxide detection unit C includes a carbon dioxide infrared analyzer 12 and a computer 13. The carbon dioxide infrared analyzer 12 can monitor the carbon dioxide concentration at the outlet in real time.

[0037] The mixture consists of 15% CO2 and 85% N2 to simulate flue gas. The inlet flow rate of the mixture is controlled by an inlet rotor flow meter, which determines the inlet CO2 concentration reading. The infrared gas analyzer 12 records the outlet CO2 concentration reading every 15 seconds. Since N2 does not participate in the reaction, the absorption capacity, absorption rate, desorption capacity, desorption rate, and desorption ratio of the absorbent can be calculated from the N2 flow rate and the changes in inlet and outlet CO2 concentrations.

[0038] 1. The absorption experiment using a carbon dioxide absorption and desorption experimental apparatus specifically includes the following steps:

[0039] (1) Preheating of infrared gas analyzer 12: Start the infrared gas analyzer 12 to preheat for 15 minutes;

[0040] (2) Zeroing the infrared gas analyzer 12: After the infrared gas analyzer 12 has finished preheating, open the pressure reducing valve 3 and the nitrogen cylinder 1, place the three-way valve 5 in the infrared gas analyzer 12 passage, introduce nitrogen into the infrared gas analyzer 12 and start zeroing for 180s.

[0041] (3) Preparation of absorbent: Prepare the required absorbent solution and transfer it to a three-necked flask;

[0042] (4) Install the absorption device: Place the three-necked flask and the serpentine condenser in a water bath and fix them with an iron stand. The condensate flows in from the bottom of the condenser and out from the top. Insert the thermometer into the solution and connect the inlet pipe and the outlet pipe. The inlet pipe is placed below the liquid surface of the solution.

[0043] (5) Absorbent pretreatment: Turn on the water bath to heat, set the absorption temperature to 40℃, and the stirring speed to 200rpm;

[0044] (6) Pipeline cleaning: Place the three-way valve 5 in the reactor inlet passage and the three-way valve 6 in the nitrogen passage. Turn on the rotor flow meter and use nitrogen to purge the CO2 in the device and pipeline. Wait for the reading of the infrared gas analyzer 12 to return to zero, indicating that the CO2 in the device and pipeline has been purged.

[0045] (7) Start the absorption reaction: observe the thermometer reading reach 40℃, close the pressure reducing valve 3 and nitrogen cylinder 1, open the mixed gas cylinder 2 and pressure reducing valve 4, place the three-way valve 5 in the reactor inlet passage, place the three-way valve 6 in the mixed gas passage, adjust the flow rate of the rotor flow meter to 0.6L / min, and the infrared gas analyzer 12 counts automatically at 3s intervals.

[0046] (8) End the absorption reaction: wait for the reading of infrared gas analyzer 12 to stabilize at 15.00%, close the mixed gas cylinder 2 and pressure reducing valve 4, open the nitrogen cylinder 1 and pressure reducing valve 3, place the three-way valve 5 in the reactor inlet passage, place the three-way valve 6 in the nitrogen passage, wait for the reading of infrared gas analyzer 12 to return to zero, indicating that CO2 in the pipeline has been exhausted, turn off the water bath heating and stirring and disassemble the three-necked flask and condenser, and turn off infrared gas analyzer 12.

[0047] The data processing method for the CO2 absorption experiment is as follows:

[0048] (1) The absorption rate of CO2 by the absorbent at time t is:

[0049]

[0050] r abs (t) — The absorption rate of CO2 by the absorbent at time t, mol / min

[0051] Q abs,2 —The CO2 flow rate at the inlet during the absorption experiment, in L / min

[0052] Q abs,1 —The flow rate of N2 in the absorption experiment, L / min

[0053] —volume concentration of CO2 in the outlet gas mixture at time t

[0054] V m —Molar volume of gas, 22.4 L / mol

[0055] (2) The average absorption rate of CO2 by the adsorbent during time interval 0-t is:

[0056]

[0057] —The average absorption rate of CO2 by the absorbent within time t

[0058] t - absorption time, min

[0059] (3) The CO2 absorption capacity of the absorbent during time 0-t is:

[0060]

[0061]

[0062] R(t) — CO2 absorption capacity of the absorbent during time 0-t, mol CO2 / kg solution

[0063] R'(t) — CO2 absorption capacity of the absorbent during time 0-t, mol CO2 / mol amine

[0064] m—mass of solution, kg

[0065] n—Amount of amine in the absorbent, in mol.

[0066] 2. The desorption experiment using a carbon dioxide absorption and desorption experimental apparatus specifically includes the following steps:

[0067] (1) Preparation of desorption reaction: Turn on the water bath and heat it. Set the desorption temperature to 95℃ and the stirring speed to 200rpm.

[0068] (2) Start the desorption reaction: When the absorbent solution reaches 95°C, open the nitrogen cylinder 1 and the pressure reducing valve 3, place the three-way valve 5 in the reactor inlet passage, place the three-way valve 6 in the nitrogen passage, adjust the flow rate of the rotor flow meter to 0.6 L / min, and the infrared gas analyzer 12 counts automatically at 3-second intervals.

[0069] (3) End the desorption reaction: wait for the reading of infrared gas analyzer 12 to stabilize at 1.00%, which indicates that the desorption reaction is over. Close nitrogen cylinder 1 and pressure reducing valve 3, turn off the water bath heating and stirring, and disassemble the three-necked flask and condenser. Turn off infrared gas analyzer 12.

[0070] The data processing method for the CO2 desorption experiment is as follows:

[0071] (1) The desorption rate of CO2 by the absorbent at time t is:

[0072]

[0073] r des (t) — The rate of CO2 desorption by the absorbent at time t, mol / min

[0074] Q des —The flow rate of N2 in the desorption experiment, in L / min

[0075] —volume concentration of CO2 in the outlet gas mixture at time t

[0076] V m —Molar volume of gas, 22.4 L / mol

[0077] (2) The average desorption rate of CO2 by the adsorbent during time 0-t is:

[0078]

[0079] —The average desorption rate of CO2 by the absorbent during time 0-t, mol / min

[0080] t — desorption time, min

[0081] (3) The CO2 desorption capacity of the absorbent during time 0-t is:

[0082]

[0083]

[0084] L(t) — CO2 desorption capacity of the absorbent during time 0-t, mol CO2 / kg solution

[0085] L'(t) — CO2 desorption capacity of absorbent during time 0-t, mol CO2 / mol amine

[0086] m—mass of solution, kg

[0087] n—Amount of amine in the absorbent, in moles

[0088] (4) The amount of CO2 remaining in the absorbent after one absorption-desorption experiment is:

[0089] C = RL

[0090] C'=R'-L'

[0091] C — Residual CO2 content in the absorbent, mol CO2 / kg solution

[0092] C' — Residual CO2 content of the absorbent, mol CO2 / mol amine

[0093] (5) The CO2 desorption rate of the absorbent after the absorption and desorption experiment is:

[0094]

[0095] θ—CO2 desorption rate of the absorbent, %.

[0096] Example 1

[0097] This embodiment provides a composite absorbent for separating carbon dioxide from a mixed gas. By mass percentage, the composite absorbent is composed of 30% hydroxyethyl ethylenediamine, 30% benzyl alcohol, and 40% water.

[0098] Comparative Examples 1-9

[0099] The composite absorbents provided in Comparative Examples 1-9 are basically the same as those in Example 1, except that other solvents are used instead of benzyl alcohol in Comparative Examples 1-9.

[0100] The composition of the composite absorbents provided in Examples 1 and Comparative Examples 1-9 is shown in Table 1 below, where each component is expressed as a percentage by mass.

[0101] Table 1. Composition of the composite absorbents provided in Example 1 and Comparative Examples 1-9

[0102] serial number composition Example 1 Hydroxyethyl ethylenediamine + benzyl alcohol + water Comparative Example 1 Hydroxyethyl ethylenediamine + water Comparative Example 2 Hydroxyethyl ethylenediamine + n-propanol + water Comparative Example 3 Hydroxyethyl ethylenediamine + isopropanol + water Comparative Example 4 Hydroxyethyl ethylenediamine + n-butanol + water Comparative Example 5 Hydroxyethyl ethylenediamine + isobutanol + water Comparative Example 6 Hydroxyethyl ethylenediamine + tert-butanol + water Comparative Example 7 Hydroxyethyl ethylenediamine + polyethylene glycol + water Comparative Example 8 Hydroxyethyl ethylenediamine + ethylene glycol + water Comparative Example 9 Hydroxyethyl ethylenediamine + triethylene glycol + water

[0103] The experimental data corresponding to the composite absorbents provided in Example 1 and Comparative Examples 1-9 were tested using the aforementioned test methods. Figure 2 The diagram shows the relevant test results of the composite absorbents provided in Example 1 and Comparative Examples 1-9. Specific experimental test data for Example 1 and Comparative Examples 1-9 are shown in Table 2.

[0104] Table 2. Test results of the composite absorbents provided in Example 1 and Comparative Examples 1-9

[0105]

[0106]

[0107] Combination Figure 2 Analysis of Table 2 shows that, compared to the comparative examples, the composite absorbent prepared with benzyl alcohol in Example 1 exhibits excellent performance in both the absorption and desorption stages. Its absorption capacity reaches 61.08 L CO2 / L solution, its desorption capacity reaches 48.90 L CO2 / L solution, its desorption rate reaches 80.05%, and its average absorption rate reaches 3.68 × 10⁻⁶. -2 The flow rate was L / min, and the average desorption rate reached 2.23 × 10⁻⁶. -2 L / min.

[0108] It should be noted that during the experimental phase, the inventors considered introducing diethylene glycol into the composite absorbent system (replacing benzyl alcohol with diethylene glycol, or adding diethylene glycol based on Example 1). However, under the same conditions, the viscosity of diethylene glycol is much higher than that of benzyl alcohol. For example, at 298 K and 0.1 MPa, the viscosity of benzyl alcohol is 5.037 cp, while the viscosity of diethylene glycol is 30 cp. If diethylene glycol is introduced as a physical solvent, the viscosity of the absorbent solution will increase significantly, resulting in a decrease in the amount of CO2 absorbed by the solution. This is because a high-viscosity physical solvent reduces the formation of ions and the rate of CO2 absorption in the solution. Since the viscosity of diethylene glycol is higher than that of benzyl alcohol, the rate of ion formation and CO2 absorption in a solution containing diethylene glycol will be lower than that in the composite absorbent solution containing only benzyl alcohol in Example 1 during the CO2 absorption process. Furthermore, diethylene glycol contains COC groups, which react with amine groups during the absorption reaction to form imines. Increased imine concentration hinders the binding of free amines to CO2 in the solution, thus reducing the absorption rate and amount of CO2. Conversely, benzyl alcohol's nucleophilic attack on carbamates generates alkyl carbonates and free amines. These free amines then continue to absorb CO2, increasing the absorption rate and amount of CO2 by the absorbent solution. Therefore, introducing diethylene glycol into a composite absorbent system does not offer any advantages.

[0109] Examples 2-6

[0110] Examples 2-6 continue from Example 1 by changing the amount of different components added, and compare the absorption and desorption performance of the composite absorbents prepared by each example.

[0111] The composition of the composite absorbents provided in Examples 1-6 is shown in Table 3 below, where each component is expressed as a percentage by mass.

[0112] Table 3. Composition of the composite absorbents provided in Examples 1-6

[0113] serial number Hydroxyethyl ethylenediamine benzyl alcohol water Example 2 30％ 10％ 60％ Example 3 30％ 20％ 50％ Example 1 30％ 30％ 40％ Example 4 30％ 40％ 30％ Example 5 30％ 50％ 20％ Example 6 30％ 60％ 10％

[0114] The experimental data corresponding to the composite absorbents provided in Example-6 were tested using the aforementioned test methods. Figure 3 The diagram shows the relevant test results of the composite absorbents provided in Examples 1-6. Specific experimental test data for Examples 1-6 are shown in Table 4.

[0115] Table 4. Test results of the composite absorbents provided in Examples 1-6

[0116]

[0117]

[0118] Combination Figure 3 Analysis of Table 4 shows that, with a total amine concentration of 30 wt%, the absorption capacity of hydroxyethyl ethylenediamine + benzyl alcohol + water gradually decreases with increasing benzyl alcohol content and decreasing water content, and the average absorption rate also gradually decreases. Among them, the absorption capacity of 30 wt% hydroxyethyl ethylenediamine + 10 wt% benzyl alcohol + 60 wt% water is the largest, reaching 62.27 L CO2 / L solution. This is mainly because the carbamate generated by the reaction of hydroxyethyl ethylenediamine and CO2 undergoes a hydrolysis reaction in the aqueous system to generate free amine. The generated free amine continues to absorb CO2, thereby promoting the increase in absorption capacity. Therefore, the addition of water is beneficial to increasing the absorption capacity and the average absorption rate.

[0119] The desorption capacity initially increased and then decreased, with the highest desorption capacity observed in a solution of 30wt% hydroxyethyl ethylenediamine + 50wt% benzyl alcohol + 20wt% water, reaching 51.85 L CO2 / L. The desorption rate gradually increased, with the highest rate (93.5%) observed in a solution of 30wt% hydroxyethyl ethylenediamine + 60wt% benzyl alcohol + 10wt% water. The average desorption rate gradually increased, mainly because the carbamate formed by the reaction of hydroxyethyl ethylenediamine and CO2 is relatively stable and difficult to desorb. Benzyl alcohol, as a physical solvent, only physically absorbs CO2 and does not chemically react with it. Therefore, the higher the benzyl alcohol content, the higher the desorption rate. Furthermore, since the sensible heat required to heat benzyl alcohol to its regeneration temperature is less than that of water, the latent heat carried away by water vapor evaporation is eliminated, and most of the saved energy is used for the desorption reaction, thus accelerating the desorption process and increasing the average desorption rate.

[0120] In summary, comparing the absorption, desorption, and desorption rates of the six different ratios of composite absorbents, it can be concluded that the optimal ratio of 30wt% organic amine solution + 50wt% benzyl alcohol + 20wt% water provides the best overall absorption-desorption effect.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above-described embodiments are merely illustrative of several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A composite absorbent for separating carbon dioxide from a gas mixture, characterized in that, Composed of hydroxyethyl ethylenediamine, benzyl alcohol, and water, the composite absorbent has a desorption temperature of less than 100°C.

2. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The hydroxyethyl ethylenediamine accounts for 30% of the total mass of the composite absorbent by weight percentage.

3. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The benzyl alcohol accounts for 30-50% of the total mass of the composite absorbent by mass percentage.

4. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The water accounts for 20-40% of the total mass of the composite absorbent by mass percentage.

5. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The composite absorbent is composed of 30% hydroxyethyl ethylenediamine, 50% benzyl alcohol, and 20% water by weight percentage.

6. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The average absorption rate of the composite absorbent over 120 minutes was between 2.68 × 10⁻⁶. -2 L / min up to 3.68 × 10 -2 Between L / min.

7. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The average desorption rate of the composite absorbent over 120 minutes is between 2.23 × 10⁻⁶. -2 L / min up to 2.47 × 10 -2 Between L / min.

8. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 6 or 7, characterized in that, The desorption rate of the composite absorbent is not less than 80%.

9. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The desorption temperature of the composite absorbent is 95℃.

10. The composite absorbent for separating carbon dioxide from a mixed gas as described in claim 1, characterized in that, The mixed gas includes flue gas from coal-fired power plants.

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