An absorbent for removing sulfur dioxide in flue gas and a preparation method thereof

Abstract

The application discloses an absorbent for removing sulfur dioxide in flue gas and a preparation method thereof, and the absorbent comprises organic polyamine, organic acid buffer solution and desulfurization activator; the organic polyamine comprises primary polyamine and tertiary polyamine; and the organic acid buffer solution is a mixture of citric acid-sodium citrate buffer solution and ethylenediaminetetraacetic acid-ethylenediaminetetraacetic acid disodium buffer solution. The desulfurization absorbent has a large absorption amount of sulfur dioxide and strong oxidation resistance, and can reduce the concentration of sulfur dioxide in flue gas from 5000-20000 mg / m 3 to 40 mg / m 3 , so that the purpose of deep removal is achieved.

Description

Technical Field

[0001] This invention belongs to the field of gas purification technology, specifically relating to an absorbent for removing sulfur dioxide from flue gas and its preparation method. Background Technology

[0002] During natural gas exploration and development, since the majority of the produced natural gas contains sulfur, it needs to undergo desulfurization treatment before entering the gas transmission network and being supplied to downstream users. Generally speaking, for small-scale processing volumes (50×10... 4 m 3 For the purification of medium and low sulfur content (potential sulfur content S < 50 t / d, especially S < 10 t / d) natural gas, the following methods are mainly adopted: For those with very small potential sulfur content (S ≤ 0.1 t / d), dry desulfurization process is the main method; for those with large potential sulfur content (S ≥ 5 t / d), amine desulfurization combined with secondary conventional Claus sulfur recovery and tail gas incineration is used.

[0003] Organic amine wet desulfurization processes can realize the resource utilization of sulfides and the recycling of desulfurizing agents, effectively reducing secondary pollution. Amine solutions can absorb sulfur dioxide; MEA is one of the most common commercial absorbents. However, this absorbent suffers from severe degradation. This is because the presence of small amounts of oxygen in the sulfur dioxide gas in the flue gas duct leads to the oxidation and degradation of organic amines, reducing their absorption capacity for sulfur dioxide. Simultaneously, sulfur dioxide dissolved in water reacts with organic amines to generate HSO3. - and SO3 2- The oxygen present oxidizes HSO3 - and SO3 2- Will generate SO4 2- This results in the absorbent being unable to regenerate, and the generated SO4 2- There may be precipitation in the pipes, which can cause blockages.

[0004] Although current absorbents are working to improve their absorption capacity for sulfur dioxide and reduce the impact of oxygen, the removal rate of sulfur dioxide remains insufficient, failing to achieve deep removal. Furthermore, existing absorbents often include antioxidants, such as the phenolic antioxidant BHT, which are highly volatile, resulting in poor antioxidant effects.

[0005] Therefore, this patent application is filed. Summary of the Invention

[0006] The purpose of this patent application is to solve the technical problems of insufficient removal rate of sulfur dioxide by existing organic amine desulfurization absorbents and easy degradation due to oxygen influence.

[0007] This invention is achieved through the following technical solution:

[0008] The first objective of this invention is to provide an absorbent for removing sulfur dioxide from flue gas, comprising an organic polyamine, an organic acid buffer solution, and a desulfurization activator;

[0009] The organic polyamines include primary polyamines and tertiary polyamines;

[0010] The organic acid buffer solution is a mixture of citric acid-sodium citrate buffer solution and ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution.

[0011] The desulfurization absorbent provided in this embodiment of the invention uses polyamines as the organic amine, which can improve the absorption capacity of organic amines for sulfur dioxide. The organic polyamines include primary and tertiary polyamines. The combination of primary and tertiary polyamines can significantly improve the absorption efficiency of sulfur dioxide and increase the absorption capacity. Furthermore, the molecular structures of primary and tertiary amines increase intermolecular steric hindrance and hydrogen bonding, which has a certain stabilizing effect on the generated sulfite ions, reducing the oxidation of sulfite ions by oxygen. Two buffer solutions are added to the absorbent: citric acid and sodium citrate act as complexing agents to complex sulfite ions, thereby stabilizing them. Sodium citrate, when dissolved in water, can adjust the pH of the system, preventing a significant drop in the pH value of the solution after sulfur dioxide dissolves in water, and reducing the reaction equilibrium from shifting towards SO4 formation. 2- This process, by moving in the same direction, also increases the solubility of sulfur dioxide and improves the removal rate.

[0012] Ethylenediaminetetraacetic acid (EDTA)-disodium EDTA can act as an antioxidant to capture free radicals (OH·) dissolved in aqueous solutions. Since OH· is an oxygen-containing free radical with strong oxidizing properties, it can cause organic amines to be oxidized, affecting their absorption capacity for sulfur dioxide. It can also lead to the stabilizing effect of complexing agents on sulfite ions, impacting the regeneration reaction. Therefore, this invention utilizes EDTA-disodium EDTA to capture free radicals (OH·) and reduce oxidation. The presence of citric acid and sodium citrate enhances the antioxidant properties of EDTA-disodium EDTA. EDTA-disodium EDTA also has a stabilizing effect on sulfite and bisulfite ions. Furthermore, EDTA-disodium EDTA has relatively low volatility.

[0013] Therefore, the absorbent provided by this invention achieves deep removal of sulfur dioxide through the synergistic effect of multiple tertiary amines and buffer solutions, and can remove sulfur dioxide from flue gas with an initial concentration of 5000–20000 mg / m³. 3 The concentration of sulfur dioxide was reduced to 40 mg / m³. 3 The following steps are taken to achieve deep removal.

[0014] In an optional embodiment, the polyamine is selected from any one or a combination of two or more of ethylenediamine and its derivatives, 1,2-propanediamine and its derivatives, 1,3-propanediamine and its derivatives, and tris(2-aminoethyl)amine.

[0015] The polytertiary amine is selected from any one or any combination of two or more of ditertiary amines, tritertiary amines, and tetratertiary amines.

[0016] In an optional embodiment, the molecular structure of the poly-tertiary amine has aliphatic alkyl branches, wherein the aliphatic alkyl group is a straight-chain or a branched aliphatic alkyl group.

[0017] The molecular structural formula of the poly-tertiary amine is:

[0018]

[0019] R1, R2, R3, and R4 are all aliphatic alkyl groups with hydroxyl groups. The number of carbon atoms in the aliphatic alkyl group is 1 to 5. The aliphatic alkyl group is a straight-chain or branched alkyl group, and n is an integer from 1 to 5.

[0020] In this embodiment of the invention, the molecular structure of the poly-tertiary amine is designed to contain aliphatic alkyl groups, which are branched and contain hydroxyl groups. This promotes the transport efficiency of sulfur dioxide. The branched alkyl groups increase the steric hindrance within the molecule, reduce the heat of absorption, and facilitate desorption. The intermolecular hydrogen bonding also facilitates the desorption of the absorbent, reducing the energy consumed in the desorption process. The introduction of hydroxyl groups into the tertiary amine enhances the absorption of sulfur dioxide. With strong absorption of sulfur dioxide, less is absorbed of the small amount of carbon dioxide in the flue gas, achieving selective absorption.

[0021] In an optional embodiment, the molar ratio of the polyamine to the polytertiary amine is 1.2 to 2:1.

[0022] In an optional embodiment, the molar ratio of citric acid to sodium citrate in the citric acid-sodium citrate buffer solution is 0.8 to 1.0:1.

[0023] In an optional embodiment, the molar ratio of ethylenediaminetetraacetic acid (EDTA) to disodium EDTA in the EDTA- ...

[0024] In an optional embodiment, the volume ratio of the citrate-sodium citrate buffer solution to the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:(1.2-1.5).

[0025] In this invention, citric acid-sodium citrate belongs to organic strong acid-organic strong acid salt. Through the rational design of the volume of the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution, the volume of the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is larger, which is more conducive to the removal of sulfur dioxide in synergy with citric acid-sodium citrate, and the antioxidant effect is also more obvious, so there is no need to add antioxidants separately.

[0026] In an optional embodiment, the desulfurization activator is any one or a combination of two or more of triethanolamine, N-methyl-diethanolamine, and tripropanolamine.

[0027] In an optional embodiment, the mass ratio of the organic polyamine, the organic acid buffer solution, and the desulfurization activator is (10-70):(1-8):(0.05-6).

[0028] The second objective of this invention is to provide a method for preparing an absorbent for removing sulfur dioxide from flue gas as described in any of the above claims, wherein an organic polyamine, an organic acid buffer solution, a desulfurization activator, and water are mixed evenly, and the pH is adjusted to 5.0-6.5.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] The desulfurization absorbent provided by this invention uses poly-primary and tertiary amines, which can improve the absorption capacity of organic amines for sulfur dioxide. The molecular structure of primary and tertiary amines reduces the oxidation of sulfite ions by oxygen. The addition of two buffer solutions to the absorbent: citric acid-sodium citrate acts as a complexing agent to chelate sulfite ions, thereby stabilizing sulfite ions and improving the solubility of sulfur dioxide, thus increasing the removal rate; and ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid acts as an antioxidant to capture free radicals OH· dissolved in aqueous solution, reducing oxidation.

[0031] The absorbent provided by this invention achieves deep removal of sulfur dioxide through the synergistic effect of multiple tertiary amines and buffer solutions, reducing the initial concentration of sulfur dioxide in flue gas from 5000 to 20000 mg / m³. 3 The concentration of sulfur dioxide was reduced to 40 mg / m³. 3 The following steps are taken to achieve deep removal. Detailed Implementation

[0032] The embodiments of this application will be described in further detail below with reference to the examples. The detailed description of the following embodiments is used to illustrate the principles of this application, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0033] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0038] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0039] Example 1:

[0040] An absorbent for removing sulfur dioxide from flue gas is prepared by mixing organic polyamine, organic acid buffer solution, desulfurization activator, and water evenly and adjusting the pH to 6.0.

[0041] Organic amines include ethylenediamine and polyamines. The structural formula of polyamines is:

[0042] Wherein, R1 and R2 are both methyl, R3 is ethyl, R4 is -CH(CH3)CH2OH, n is 1, and the molar ratio of ethylenediamine to polytertiary amine is 1.2:1.

[0043] In the organic acid buffer solution, the molar ratio of citric acid to sodium citrate is 1:1, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:2, and the volume ratio of citric acid-sodium citrate buffer solution to ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:1.5.

[0044] The desulfurizing agent is triethanolamine.

[0045] Example 2:

[0046] An absorbent for removing sulfur dioxide from flue gas is prepared by uniformly mixing organic polyamine, organic acid buffer solution, desulfurization activator, and water, and adjusting the pH to 6.2.

[0047] Organic amines include 1,2-propanetriamine and polyamines. The structural formula of polyamines is...

[0048] Wherein, R1 and R2 are both ethyl groups, R3 is an ethyl group, R4 is -CH(CH3)OH, n is 3, and the molar ratio of ethylenediamine to polytertiary amine is 2:1.

[0049] In the organic acid buffer solution, the molar ratio of citric acid to sodium citrate is 0.8:1, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:2.5, and the volume ratio of citric acid-sodium citrate buffer solution to ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:1.2.

[0050] The desulfurizing agent is N-methyldiethanolamine.

[0051] The mass ratio of organic polyamine, organic acid buffer solution, and desulfurization activator is 10:3:5.

[0052] Example 3:

[0053] An absorbent for removing sulfur dioxide from flue gas is prepared by mixing organic polyamine, organic acid buffer solution, desulfurization activator, and water evenly and adjusting the pH to 6.0.

[0054] Organic amines include ethylenediamine and polyamines. The structural formula of polyamines is:

[0055] Wherein, R1 is -CH(CH3)OH, R2 is ethyl, R3 is ethyl, R4 is -CH(CH3)OH, n is 2, and the molar ratio of ethylenediamine to polytertiary amine is 2:1.

[0056] In the organic acid buffer solution, the molar ratio of citric acid to sodium citrate is 0.8:1, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:2.5, and the volume ratio of citric acid-sodium citrate buffer solution to ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:1.2.

[0057] The desulfurizing agent is N-methyldiethanolamine.

[0058] The mass ratio of organic polyamine, organic acid buffer solution, and desulfurization activator is 10:3:5.

[0059] Example 4:

[0060] An absorbent for removing sulfur dioxide from flue gas is prepared by mixing organic polyamine, organic acid buffer solution, desulfurization activator, and water evenly, and adjusting the pH to 6.5.

[0061] Organic amines include ethylenediamine and polyamines. The structural formula of polyamines is:

[0062] Wherein, R1 is -CH(CH3)OH, R2 is -CH(CH3)CH2OH, R3 is ethyl, R4 is methyl, n is 5, and the molar ratio of ethylenediamine to polytertiary amine is 2:1.

[0063] In the organic acid buffer solution, the molar ratio of citric acid to sodium citrate is 1:1, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:5, and the volume ratio of citric acid-sodium citrate buffer solution to ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:1.4.

[0064] The desulfurizing agent is N-methyldiethanolamine.

[0065] The mass ratio of organic polyamine, organic acid buffer solution, and desulfurization activator is 60:8:6.

[0066] Example 5:

[0067] An absorbent for removing sulfur dioxide from flue gas is prepared by mixing organic polyamine, organic acid buffer solution, desulfurization activator, and water evenly, and adjusting the pH to 6.5.

[0068] Organic amines include ethylenediamine and polyamines. The structural formula of polyamines is:

[0069] Wherein, R1 is -CH(CH3)OH, R2 is -CH(CH3)CH2OH, R3 is ethyl, R4 is -CH(CH3)OH, n is 1, and the molar ratio of ethylenediamine to polytertiary amine is 2:1.

[0070] In the organic acid buffer solution, the molar ratio of citric acid to sodium citrate is 1:1, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:4, and the volume ratio of citric acid-sodium citrate buffer solution to ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:1.2.

[0071] The desulfurizing agent is diethanolamine.

[0072] The mass ratio of organic polyamine, organic acid buffer solution, and desulfurization activator is 50:7:1.

[0073] Example 6:

[0074] An absorbent for removing sulfur dioxide from flue gas is prepared by mixing organic polyamine, organic acid buffer solution, desulfurization activator, and water evenly, and adjusting the pH to 6.5.

[0075] Organic amines include ethylenediamine and polyamines. The structural formula of polyamines is:

[0076] In this system, R1, R2, R3, and R4 are all ethyl groups, n is 1, and the molar ratio of ethylenediamine to polytertiary amine is 2:1.

[0077] In the organic acid buffer solution, the molar ratio of citric acid to sodium citrate is 1:1, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:4, and the volume ratio of citric acid-sodium citrate buffer solution to ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:1.2.

[0078] The desulfurizing agent is diethanolamine.

[0079] The mass ratio of organic polyamine, organic acid buffer solution, and desulfurization activator is 50:7:1.

[0080] Comparative Example 1:

[0081] The difference from Example 1 is that the organic polyamine is only a polyamine, and the polyamine is ethylenediamine; otherwise, it is the same as Example 1.

[0082] Comparative Example 2:

[0083] The difference from Example 1 is that the organic acid buffer solution is only a citrate-sodium citrate buffer solution, without the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution, otherwise it is the same as Example 1.

[0084] Comparative Example 3:

[0085] The difference from Example 1 is that the organic acid buffer solution is only ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution, without citric acid-sodium citrate buffer solution, otherwise it is the same as Example 1.

[0086] test:

[0087] 1. Study the oxidation rate during the absorption and desorption processes.

[0088] Oxidation rate 1 during absorption process = S in amine-rich solution 6+ Increase in substance amount x 100% / Increase in sulfur dioxide in amine-rich solution;

[0089] Oxidation rate 2 during desorption = S in lean amine solution 6+ Increase in substance X 100% / Increase in sulfur dioxide in lean amine solution.

[0090] Specifically:

[0091] A mixture of SO2 and air was passed into the absorbents of the various examples and comparative examples. After absorption at 45°C for 4 hours, a rich amine solution was obtained. The rich amine solution was then heated to 105°C for desorption for 3 hours to obtain a lean amine solution. The oxidation rates were measured using both the rich and lean amine solutions, and the results are shown in Table 1.

[0092] Table 1

[0093] Serial Number Oxidation rate during absorption process Oxidation rate during desorption Example 1 047 0.53 Example 2 0.42 0.51 Example 3 0.44 0.54 Example 4 0.49 0.58 Example 5 0.45 0.57 Example 6 0.52 0.63 Comparative Example 1 4.54 5.87 Comparative Example 2 9.24 9.88 Comparative Example 3 7.10 8.42

[0094] As shown in Table 1, in Comparative Example 1, the use of organic polyamines as primary polyamines had no significant impact on the oxidation rate during absorption and desorption. However, in Comparative Example 2, when only one type of buffer solution was used, such as a citrate-sodium citrate buffer solution or an ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution, the oxidation rate increased significantly.

[0095] 2. Study the absorption and desorption rates of SO2.

[0096] The absorbents obtained in Examples 1-6 and Comparative Examples 1-3 were subjected to simulated absorption and desorption experiments:

[0097] Operating conditions for sulfur dioxide absorption:

[0098] Temperature: 50℃, Pressure: 0.1MPa;

[0099] The gas mixture composition is as follows: SO2 and O2 have a volume percentage of 5.7% and 5.7%, respectively, and CO2 has a volume percentage of 2.0%.

[0100] The gas flow rate was 300 ml / min, and the absorption rate was measured.

[0101] Operating conditions for SO2 regeneration: temperature 100℃, pressure 0.1MPa, and determination of desorption rate.

[0102] The results are shown in Table 2.

[0103] Table 2

[0104]

[0105] As can be seen from the results in Table 2, the initial concentration in the flue gas in each embodiment can be 5000–20000 mg / m³. 3 The concentration of sulfur dioxide was reduced to 40 mg / m³. 3 The following examples show that the absorption rates for sulfur dioxide reached over 99.0% within 1 hour, while the absorption rates for carbon dioxide were very low. The absorbents obtained in each example exhibited a large absorption capacity for sulfur dioxide, achieving selective absorption. The desorption rate for sulfur dioxide reached over 90%. However, in Example 6, because the organic amine structure did not contain aliphatic alkyl hydroxyl groups, the absorption rate and desorption rate for sulfur dioxide were slightly lower. This demonstrates that aliphatic alkyl hydroxyl groups are helpful in improving both the absorption capacity and desorption rate of sulfur dioxide.

[0106] In the comparative examples, Comparative Example 1, due to the presence of a polybasic primary amine, showed a significant decrease in its sulfur dioxide absorption capacity. Comparative Example 2 used a citrate-sodium citrate buffer solution; without the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution, the absorption of sulfur dioxide decreased due to reduced antioxidant capacity of the absorbent, lower sulfite ion concentration, and significant degradation of the organic amine. In Comparative Example 3, the organic acid buffer solution was solely an ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution; the absence of citrate-sodium citrate further reduced the absorbent's antioxidant capacity, also affecting its sulfur dioxide absorption efficiency.

[0107] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. 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. An absorbent for the removal of sulfur dioxide from flue gas, characterized in that, Including organic polyamines, organic acid buffer solutions, and desulfurization activators; The organic polyamines include primary polyamines and tertiary polyamines; The organic acid buffer solution is a mixture of citric acid-sodium citrate buffer solution and ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution.

2. The absorbent for removal of sulfur dioxide from flue gas according to claim 1, characterized in that, The polyamine is selected from any one or a combination of two or more of ethylenediamine and its derivatives, 1,2-propanediamine and its derivatives, 1,3-propanediamine and its derivatives, and tris(2-aminoethyl)amine. The polytertiary amine is selected from any one or any combination of two or more of ditertiary amines, tritertiary amines, and tetratertiary amines.

3. The absorbent for removal of sulfur dioxide from flue gas according to claim 1, characterized in that, The molecular structure of the poly-tertiary amine has aliphatic alkyl branches, and hydroxyl groups are attached to the aliphatic alkyl branches. The molecular structural formula of the poly-tertiary amine is: R1, R2, R3, and R4 are all aliphatic alkyl groups with hydroxyl groups. The number of carbon atoms in the aliphatic alkyl group is 1 to 5. The aliphatic alkyl group is a straight-chain or branched aliphatic alkyl group, and n is an integer from 1 to 5.

4. The absorbent for removing sulfur dioxide from flue gas according to claim 3, characterized in that, The molar ratio of the primary polyamine to the tertiary polyamine is 1.2 to 2:

1.

5. An absorbent for removing sulfur dioxide from flue gas according to claim 1, characterized in that, In the citric acid-sodium citrate buffer solution, the molar ratio of citric acid to sodium citrate is 0.8 to 1.0:

1.

6. The absorbent for removing sulfur dioxide from flue gas according to claim 1, characterized in that, In the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution, the molar ratio of ethylenediaminetetraacetic acid to disodium ethylenediaminetetraacetic acid is 1:(2-5).

7. The absorbent for removing sulfur dioxide from flue gas according to claim 1, characterized in that, The volume ratio of the citric acid-sodium citrate buffer solution to the ethylenediaminetetraacetic acid-disodium ethylenediaminetetraacetic acid buffer solution is 1:(1.2-1.5).

8. An absorbent for removing sulfur dioxide from flue gas according to claim 1, characterized in that, The desulfurization activator is selected from any one or any combination of two or more of triethanolamine, N-methyldiethanolamine, and diethanolamine.

9. An absorbent for removing sulfur dioxide from flue gas according to claim 1, characterized in that, The mass ratio of the organic polyamine, organic acid buffer solution, and desulfurization activator is (10-70):(1-8):(0.05-6).

10. A method for preparing an absorbent for removing sulfur dioxide from flue gas according to any one of claims 1 to 9, characterized in that, Mix the organic polyamine, organic acid buffer solution, desulfurization activator, and water thoroughly, and adjust the pH to 5.0–6.5.

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